DOCUMENT RESUME,, A ED '170 1110 SE027 bill.

0 AUTHOR Thatcher, L.L. ;And Others 1 TITLE Techniques of Water-Resources Investigations of the United. States' Geblogical.Survey. Book 5, Laboratory, Analysis. Chapter- A5, Methodscr Dete-rmination of - Radioactive Substances in Water and Fluvial Sediments. INSTITUTION -Geological Survey (Dept,: .of Interior) ,Reston, PUB DATE 77 NO Tr 95p. ;For related document, see ED 131 218 AVAILABLE FRQM Super.intendent of Documents, U.S. Government Printing Off /ce , Washington, D.C. -20402(Stock Number 024- 0.01- 02928- 6:, No price quoted) */ FDRS PRICE MF01/PC04 Plus Postage. DESCRIPTORS *ChemiCal Analysis; *Geolo'gy; *LaboratorTechniques; PhYsic; Pollution; Retource Materials; S.c ence Equipment; Water Pollution control IDENTIFIERS *RadioactiveVs- Substances; *Sediments; Water Quality ABSTkACT Analytical methods for determining important , tompbnents of fission and 'natural radioactivity found in water are reportedThe discussion of each method includes conditions for application of the method, a summary of the method, interferences, required apparatus, Procedures, calculations and estimation of precision. considered are cesium-137, -90, -210, -226. and 228, tritium, and -714. `When two methods are in use for an ,- both methods are reported. Techniques for the collection and preservation of water samples to be anallze?d for radioactivity are also discuSsed.(CS)

v. *********************************************************************** 4 Re. productions supplied by ERRS are the best that can :be made * * * T from theotigiRal document. a \ t 1*****************************;******4***************A***************,**Ii 1.1$ DEPARTMENT OFHEALTH, EDUCATION & INFLFARE NATIONAL INSTITUTE OF EDUCATION _BEEN REPRO- THIS DOCUMENT HASRECEIVED FROM DUCED: EXACTLY AS ORIGIN- PERSON OR ORGANIZATION ATING IT POINTS OF VIEWOR OPINIONS STATED DO NOT NECESSARILYREPRE- INSTITUTE OF SENT OFFICIAL NATIONAL EDUCATION POSITIONOR-POLICY

CD -Techniques or Water-Resou rces Investigations ,, Of .the United States,GeOJogicalSurvey

.00 r I

Chapter A5-

I METHODSFORDETERMINATION OFc. RADIOACTIVE SUBSTANCES IN WATER ANDFLUVIAL SEDIMENTS is

/ By L. L. Thatcher land 'V.pianzer, U.S. Geological Survey, and K: W. Edwards, Colorado. Schoolaf Mines

0 Book 5 RATOitY AN

..f(-6) e

'UNITED TC115 7.7P-414RTMENT OF THE INTERIOR

r,CEPPIE, Secretary

GEOLZGaICAL SURVEY

ItItt=eivey, DretttOr', ti

:

UNITED STATEiC-OVERi .r RINTING OFFICE, WAS 1S377

V .

For sale by-the SL:pertnte cumehts. U.S. _ang , fir n, D.C. 20402 \ : 024-001-02928-6 PREFACE meth used by '2e T is serifs of -lar12sorisrlkliescbs. Gologe. cal Survey olannin. tn,:,_=x.ecuting water -Tscr.-rces.finvestoz;..- tions. The mater.. -, gr-._:.ne;: u..,:te.ma .o..- sub;ect readin.-3 -called.'booE.-s and Is further su',-,- Diet::iri:.tetions s.-..: chapter Bonk 5 is on labors tory analysis. Se' )1..._ -:: water. Tlw ...-.1.: of pubilmtion, the chapte 44limited to a.na 7 -ow :.-__,..._ ( st.t.7,-;ect mi t.k,- Aethoosi f.:,kr determination of radioactive sutstance: in N' -..".tmitrt 11,tvial sediments'' is the fifth chap- ter to be publisht-a underect.,.,r., .' Flo t)lc 5. The chapter a..tunberincluds- the letter of the sectior7h. .. ".-..k4t1'.,' rrna.- of this rittx,vatkis manual .1 designed, to permit flex: -...-,i3O'.(37: Id c.blication. :.: -.;plements. he prepared as the nee( .-:,,,:-..,,-A- .. Itt:.-,.:..,-(1 o at no char.:, as they teconio availabi- III

4 CONTENTS.

Page Pre . Preface III and beta radioactivity, dissolved .. Abstrar- 1 uspended. Residue method (R-1120-- j . 29 ( Introduzon 1. - 4- Pu__ose 1 Reference 5.- 32 (irilization 1 Lead-210, "dissol Cherpical )separation and 33 ., 7_ .-__.-2.ear data.i4(- .....-- 2 precipitation method (R-1130-76) - IV Urr,:s, symbo s, and abbFeviapions Referetice,1 37 gources of radioadtivity in water . 2 Radi lved, as radium-226.Precipi-4- Natural*: radioaCtivity 2 n method (R-1140-76) 39 '41 Artificial radioactivity' ... 3 Reference Permissible concentrations of radioactiv- Radium-226, dissolved. Ratonemanation ity in, effluents to unrestricted areas method. (R-1141-76) 43 Radiological safety 4 RefTrences 49 Geochemistry of radioactivity in water 4 Radium-228, dissolved. Determination by sepa- Carbon-14 4 ration' and counting of -228 (R- Cesium -137" and cesium-1 '''.4 5 1142-76) .61 Lead-210 5 Reference. 54 .Radium 6 Radioruthenium, dissolved, as -106. Ruthenium-106 and ruthenium-103 _ 7 Distillation method (R-1150-76) 55 Strontium-90 7 References 58 Tritium (-3) '7 Strontium-90, dissolved. Chemical separation 8 ^ -, . and precipitation method (R-1160-76) __- 59 9 -ollection and, treatment of samples References 62 _olculations of radionuclide -concentrations _ _ 11 "stoilium. Liquid scintillation method, Denver Glossary 14 14 lab (R-1171-76) q3 Selected references 66 Principles of .rOioactivity, nuclear\ instru- Reference mentation . 14 Tritium. Liquid scintillation method, Reston Compilations of data: on radioactivity and lab "(R-1173-76) 67 71 radiochemistry 14 References Radioactivity iii/the environment 15 Tritium. Electrolytie enrichmentliquid scin- Radioisotope methods in hydrology. __ _ 15 tillation method, Denver lab' CR-1172-76) - 73 Radiochemical analytical tnethods 15 References 78 Radioactivity regulations and safety ._ 15 Tritium: Electrolytic enrichmentliquid scin- :references 16 tillation method, Reston lab (R-1174-76) _ 79 Carbon-14, dissolved, apparent_ ale. , Liquid References 17 81 scintillation method, Denver lab (R-1100 , Uranium, dissolved. .Fluprometric method 76) direct 1R-1180-76) 83 References 2 References -.0 88 Cesium-137 and cesium-13 ,dissolved. Inor- ganic ionexchange me ocl-gamma count- ' Uranium, ...dissolved. F/uorometric methodex- 23, traction procedure (R-1181-76) 89 ing (R-1110-76) References 92 References-- __ _, 25 ,Uranium, dissolved,isotopicratios.. Alpha . ed, as cesium-137. Thor- Ftadiocesium, disso AR- '. genic ion-exc ge filethodbeta counting spectrometrychemical separation (R-111146 27 1182-176) 93. Refere 28 Reference 95

- CT CONTENTS

FIGU ). $ a I . . .' . ) N 6 Ptge 1 '1.In-growth and decay of a daught6 .nuclide, significant time intervals _L,_,_ 13 2.Apparsitus for collection of carbonates from a water. sanhple 18 3. Vacuu4 line for prepaiation of and conversion to benzene 19 4.' Growth of -210 from pure lead-210 source .. 36 SI-"-- 5. deemanation 'train and bubbler 44 6. Radon 'Scintillation cell and housing. .. . 45 7. Apparatus for the distillation of . ruthenium tetroxide 66 8.Oltlund electrolysis cell . ..- :-'75 9.Stevens apparatus for fusion and Mixing of sample- and iux in uranium determination 84 10. dish. for use in Stevens apparatus ..,=. .011. Uranium calibration curve 86 .

TABLES

Pigs 1. Radon fraction (e-''') remaining after for specified times .. 48 2. Recommended sample volumes, minimum, and reduced volumes for isotopic uranium analysis 94

- r

METHODS .F041 DETERM1444JMN OF RADIOACTIVE SUBSTANCES 4 WATEc, ,ND FLUVIAL SEDoMENTS

By . Thaecnt ---,a Janzer, U.S. GeologicalSurvey. and 1( c-wards. Colorado School. of Mines

oulastrar- referenced so that an expEriersceL radio- chemist could set upi the anz6.7ti'-r.._ met Analytical menucds :or tn.. _Aratiat of some w. of the mere imurz-=nt Compor-- neu- with rea,onable assurance or su2'ess. . tronactivation radios tatural exceptior are the determinx=or tr, wt radioactity four water I ';'17".1. h P re- by gas cout.:.-..ug and the deterr" matif port for each arx,..:!ai metnc ..:at ns Beemuse of the Conapiexity ne for application ae meth°, . ,he )f ar 7-ag- equipment air.the extreme immort,A. method, interferte,etvps ,,dpa ru- ents,analytical.rutedure, ulation. rpc.rting certain. critics_ details in both of results, sad =nation srecisien. fission mentation and operating proced=--. at- product isotopes 7isidere, ceaitm. sr:rori- temp( to convey the fully detaileL,ir., tium-90, and ruth.--_urn-10_ nate*, maioete..,- procedure for direct dupli-ior. has ments. and isotope:-nsider '. ead-210' r.f. A probability for success: There is radium-226, radio- .28, :s.bor- -gross radioactivit- 7r -hoc uranium tute for actual operating experiencc. isotope ratio meths Jse Whe_ iislytical atories equipped for the gas,:ount.g deter methods are in roe us:, .% inc.: isotope, mination of tri.tum and the determ:Tiation or both methods are -1-zorted -v . . n ofthe carbbn-14. For the above reason`, the de- speciftc areas- of :clues fcr scriptions of these two analytica prvcedure. the collection ant 7--fZeseivE _= Wimples:0 be analyzed for m=:..oactiv4.2,a concentrate on the principles am najor op- erating conditions 'involved. "Q. In several analytical methods. reagents on rgrroch...:tibn equipment are cited by propr-etary name. This is due tc inadequate iatormation on ?urls%ose chemical composition 'on which to base a chemical name. or to special requirements This :he cal meth- known to be met by the citad,reagent or ods used by -!--110..F °logical Survey for equipment. In every case equivalent products the collectior azai) sis of water samples 'that meet requirements may sp- substituted. for radioac: ubstances. The analytical No endorsement is intended. methods art- ---ndec-..)r the radicschemist who applies :truer- :se to the analysig of Organization water. Adel .r.rour ling in :he principles' and practices 1116-saiioc nernistry is assumed. Each determination-includes section on Therefore, sue,-flojeczs as nuclear instru- "Application," "Summary of method," mentation4sr-1,,4qts, Lad radiation charac- "Interferences," "Apparatus,''Reagents," teristics are at tscusd. References are "ProCedtre," "Calculations,:' ..eport"(of given to several e=r2.11en textbooks available results), and "Precision." The "Chiculation" on these- sgbjmf.'s section under each -determinaon differs Generally, met _.na:yfical method is de- slightly from thekracti& in. chapt.er Al in scribed in suffi-ier. .tail- and .s adequately that reference is made to a general equation 2 TECHNIQUE: OF WATER-R. I:SOURCES INVEST.T'ONS when possible. Radioactivity calculations for ml____milliliter different nuclides follow similar principles zal____gallon (3.7'65 li*rs 1 which can be summarized in 2 general equa- rheatfr tion. The general equation, with its.modific.:. cm tions to fit particular requirements, is col- mm '___millimeter sidered in a following sectioi. in.J___inch (2.54 cm) ft foot (30.48 err)

Nucleay data gram Data on half-lives were taken from 1.tt "Chart of :he Nuclides" 7'; der and Wei, molarity o± solution er, 1969): Data or deck,livErnes and ene _ normality cs soluti gies of nuclear raJiation"ere taken frog 71 QC. rniljiequivale- "Table of Isotopes"(Le-... and others- 7)1.- ___pounds per scare inch 1968). The "Chart the:fielides" wa's re- /. prcuced in "Radii 'It.jth Handbook. :aurces of radioactivity in water (U.S. Dept. of He. .ucation, and We.- fare, 1970), and 11 le more importar 4.adioactivity in water may beof natural nuclides listedit -er.Hollander, an: . artificialorigin. The principal natural. Perlman (1968) - reproduced in th,-- Apses that bring radioactivity into water HEW publication weathering of rocks containing radio- ct;--ze minerals and fallout of cosmic-ray-

. rociuced nuclides..The major sources of Unit, Symboe. anrbbreviations radipactivity are the nuclear power in- Terms that ar eno used throughout -try, nuclear weapons testing, and the the text are listocl'-eio-111rms that are used :!.efulapplications of nuclear. materials

infrequently, ust... -,imection with one, _devices. analytical Meth( the first us- age in the text. ... are used in calcu- Natural radioactivity la:ion df data ar ender the general The principalradionuclidesintroduced equation in the' 7-ins" sections. iaturalliinto surface and ground waters are C: 'curie (3.7 .=2grations per second) ranium, radium-226,radium-2c28,radon, #Ci disintegrationspe otassium-40, tritium, and carbon-14.All second) pCi___picocurie ii...sintegrations per sec- ,ut the last two derive from- radioactive minerals.Radioactiveelementsincluding ,uCi/I __microciari zer .Iter .cranium, , and actinium and radio- 'pCi/1 __picocuries er liter _active daughters. resulting from . these de- $ cayseries- are important primarilyfor cfm counts per minute dpm ___disintegrations per minute reasons of health and as potential energy, sources. TheSe three natural decay series are keV ___thousand electron volts headed respectively by uranium-238 (half- MeV __million electron volts life 4.51 xf08 Yr), thorium-232(half-life 1.41 x10") yr), and uranium-235 (half -life d day hour 7.13 x108 yr). In ar.:1of the World where min.-__ minute radioactive minerals aA particularly -abun- sec- _ - _ _second dant as in the Joachimsthal region of Czecho- yr____year slovAia, the Minas Gerais region of Brazil, *7 base of the natural logarithms ,and the Colorado Plateau of the United In logarithm of any number N, to the base e States, radioactivity in some waters m;ay log logarithm of\any number N,'to the base 10 J greatlyI exceed the average concentrations

.0 4 , ) idiTKOBS'r FORDETERMINATIONOF RADIOACTIVE&DOAN '3 r. present in most continental waters. Dissolved by, 1980, severalftnillion gallot ofhigh-1iel natural Uranitkin is the Mayior with radioactivity on the order of 1Q constituent in most of these,waters. billion curies will becn storag-_-,- as a result of Tritium and carbon-14 are produced by-the 'clear power production .(F__Dgerton, 1963, interact* of ,cosmic -rayneutronswith p. 44a) . in the upper atmosphere. The triti- A relatively4allor an'un-Ifracilioaciivi- um is ,eventually'rain-0 out as tritiated ty may leak to the environmen: as _ resultof water, and...the radiocarbon is incorporated daily operatiOn of a nuclear povterplant be- -;-,--4-t-s:-In the into atmosi3heric . The princi- cause of neutry activation -7.1-1 " pal reservoir for both radionuclides is ulti- coolant water, Vtettti-onactwaiii...,nof s- mately the ocean. Bot radionuctides are also solVed corresi" products, ar .possible r produced by thermonuclear weapons, testing. lease of fiss- products by L;.t--'ectivetfuel In 1963, the when radioactive fallout element., though every nucl&.,powerplant reached its maximum, the atmospheric con- has built-in safeguardsaga...7:_::1,release of centratten of thernitnuclear tritium exceeded radioactivity, the possfnilit _:. accidental., that of natural tritium by apprdximately 3 leakage must alwilis be considered. orders of magnitude. The additional Carbon- In addition to tritiumaniicz..-bon-14; 14 of thermonuclear origin was much lower aboveground nuclear weapotp,testing ,re- and approximately equalled the carbon -14 leasts-- strontium-90, radioceFium isotopes, naturally in the atmosphere. Radioisotope's"ludirie-134 and other to the environ- doncentrations . in fallout have diminished ment. The fraction ' of these -adionuclidw rapidly since' 1963, as a, source of -radioiso- that fall out or, rain out into wi.zer .00diei3 or topes" in water. tritium is also a fission prod- watersheds constitute .si.,..:--__-__n .source df "lid, and by 1970 -the nuclear power industry water contamination. had probably become the largest source of Peaceful applications , n.:c_ear explo-

-tritium (Jacobs,'1968).4 sives, stich as ,nuclear gam stimulation and nuclear mining, present a _iossible source of Arificial radioactivity locallyintensecontaminationof ground Nuclear waste disposal .s the principal water. If venting occurs theT_N)ssibilitY of possible source for the leakage of artificial'contamination of surface water by fallout radionuclid$ (fission products and activa- also exists. tion products) into water. Most of the waste Nuclear fesearektlabor-,:tori,.-.:.hospitals, is derived rom the reprocessing of nuclear ftild the very, limited nurnue- .-: industrie, :fuel. ReprOessing is required at intettals to isradioactivity on ,-..v a ra-lativii' remove neutron - absorbing. fission products minor ,our,eof pole :adionuclide leak and to recover the uranium and : age, bulianaY ke of-1 I Signific,ance. Until reprocessing, 99.9 percent of the fission Measureable radioactive mate.-.1.1 may. and activation products produced remain rive from sources not normally::onsidered lticked .i.usidethe fuel element. The fuel ele- radioactive.. Examples are fly asz from' the I nkent is dissolved in , and cherhical_'e.pa- "combustion of fossil fuel (coal may contain rations of-tire highly radioactive s are uranium and radium and the ceramics in- carritd out. The fina c waste consistsf a low- dustry (uranium salare used in the prepa- level solution, whichay be sent seepage ration of some glazes) ..- .. ponds, and a high-level solutioor " ot" eolu- tion that must be stored fmany nars to Perinissible c skntWitions of allow radioactive decay. Strontium -90 (half, radioactivityeffluents to 28.9 yr), cesium-137 (hal -life 30.2 yr) unrestricted areas . iodi 12* (I-olf-life' 1.6X10 -yr) and plu- tOnium-239 (half-life 24,39yr) are major' Current values are tabula in Part 20, i raajolsotop0 of concerns It is estimatVd that "Standards for Protection Aga't Radia.: .,.

° 7

'4 . TECJINI ES. CKF--7 ATER-RE S40 CAS INVESTIGATIONS I. t. tion;"- published and uWated Ter--7*.iically by Energy Agency includes reports of. particu- . l'he U.S. Nuclear '.Regulators 0,7-imission lar val0e tolaboratory users ofetadioactIvp , 0976). The Commission is the in. ';'of the 'Safe 1111ling of Radioidappes" (ID 2) permissible concentrations of- :activity nd the " Physics Addendum" (19q0) in effluent (PCRE) valueS rep, Tie:or the are cited. Precautions againtit Contamination nuclides in this. //lanai. Tile nc2,--- --r---Fnce of and prnedures for decontamination are de- the values and tide basis for ttite.7 -7:puta- tailed in the National Bureau of Standards tionisdescribedin. NationaB..tau, ofpublication "Control and Removal of Radio-. - Standards (NBS)Handbook 5::.= 'F-;' ) and active. COntamination inLaboratoinies" NBS .Handbook 69 ()959). TheI_Public (1951). Procedures to be followed iii event.of Health Service has published _-,-._.oraqnended' an accide t involving radioactivity are de- maximum concentrationsfor racum -226, scribedif."Medical Aspepts of Radiation

strontium-90, and grossbet..aact:Arityin accidents '(Saengep, 1963). .

. drinking-water (D1-ining Water Standardp, 1962). Updated standards published in "Wa- ter Quality Criteria, 1972'c (1E73 I are quoted Geochepiisky o'racjioactivity : in additiOn, when applicable. 0 on'wat:er. -Additionaldrinleing-water regulatiort were published in the Federal -Register, vol Dis.kblved, and particulate radioactivity in aline 41, No. 133, July ,9, 197ft.. as a supple- Water is controlled by the s me mechantsms ment to Title 40, Code of Feder-al Regulationsthat affect Ether trace'and c constituents '(CPR), Part 141. The National Intevim Pri- in the geo4ydrologic environment. Radioac- mart' Drinking Water Re: rations(Part tive.disinteration of an atom by alpha and beta ,decriy ,.results in the formation of an 141) have been published *( -_ ---i),but were in the pr cess of revision a:me time this atom of a ne* element; frequently in an ex- cited state. Gamma emission results from palier was written. 7 such an atom in the excited state gding to a * .. . loweeenergy state. The geochemical behavior - Radicilogi44saiety4 of a daughter element-maybe grossly differ -' The radiochemist or*-,----.is uses the ent/frc 111 that bf the racidacti- e parent, al- methods in this Mande. s, e an ad.e-Ails:10hitsoccurrence,distribution,and quate-Ntraining inradios,),.._nealth and traimatilmayie governed by the parent..----) safety pradtice in the laboiatory. Such train- ing is a requirement for o taining tht-U.S. Carbon-14 Nuclear. Regulatniy ssien license to Carbon-14 is the radioactive' isotope of use radionuclides. Analyse of even environ- n- with a half-I fe of 5,730 . The mental-level samples will generally require offer half-life value of 5,568 yr is generally the'use--oryarioui, radioactive' calibration used for the /alculition pf ages in order to planchets pr standardized solutions, some Of.;maintain consistency with carbon-r4 dates in which are hazarddus if not propeiTY used. the older literature. Ages based on the older Disctissions of various aspects of radiologica,1 half-lif*value are converted to the-basis_ tt i safety are given in the followingsuggested the ner half -lifebi- multiplying -by -1.03. ' reference13. An introduction iz-llie subject is Carbon-decays by. the emission of a 1:Ceta found in the. Chapter) of the radiological particle vathe low maximum energy of 156. laboratory in "*Guidelor.SafetY in the Clremi- key. cal Laboratdry" (M.iV.A., '1954). A compre- Neutrons producedb'jtrImary cosmic", hensive _exposition. ofradinlogiealhealth radiation interact: with stratospheric nitro- physics is Fund in "Principles"-of Radiation gen to produce carbon-14 and hydrogen : (.Morgan and Turner, 1971). 1N + +. H. The safety aerie's of the International Atomic 7.0 0 6 1

-11 r

-A 7; is METHODS FOR ETERMINATION OF RADIOACTIVS090.14CFS . Tl'ifate of production in the atmos,p.here i the Si- remisphere as a resin is estimated at approxima 2.4 atoms per nucleakliTeapons testing. -- ',second per square centimeter th filth's Eitliej the beta or gamma radiation aseci-, surface (Libby, 1956). Carbon- LIAls also a ated with the cesiumisotopes may be used for product 6f thertnenucleaL weapoirs" testing. their detection. DeVction by beta r'adiation,, This source h:1 apptolcirnately doubled the is more sensitivebuf less specific. The use of, atmospheric co centration of carbon-14 and gamma radiation permits distinguishing be- h5d jncreased the, concentration in surfade tween the isotopes by means of energy dis- ocean water by' bout 20 percent by' the late . crimination since t energy peak fOr cesi- 1960's (Nydal, 1966). Possible contamina- um-137 (bariunr-1 ) is at 662 keV, and' the,,,jr tion of ground waters by thermonudear car- principal for cesium-13'4 are at 605' bon-14 imposes a severe liriiition to the''keV and 796eV. predincentration of th application of carbon-14 dating. . radiocesitnn Issed before counting, in ei Carbon-14 produced-by.-cosc radiation is titer case, to perit detection at low, enizi oxidized to carbpndioxide an Ntranspkted mental levels. Pour to 20 liters of s ple tense lower atmosphere by m xing ocesses have been used with the, gamma-conting -where cit enters the biologic 1 icye. Some technique depending on sensitivity r ired. radioacttive carbonates enter the hydrologicalA few hundred xniltiliters ,are.usuallad'e: cycle an provide the.basis far/ carbon-14 .slat- quate for the beta-counting technique. 7.' k. . , mg oflder ground WaterThe specific. ac- <, 1 of cosmic-ray produced carbon-14 in Lead-210_ tivi - the a°sphere, surfae waters, and -all .livr Lead-210 orighlate,s from the decay of , ing and was determined by Libby (1955) radon-222. The isotope? a beta emitterlwith ,/to be 16 dp er gram of carbon, but is now half-life orf 22 years. Lead 210 formed under- considered toe loWer. Suess(1965) ,deter- ground ti probably trapped pn exchange sees min d 14 dp,per gram of carbon. . of clay minerals-or!, Other ieactive rnatekal he specifiactivity of carbon-14 in. car and pres mably has very limited migration. ._ bonaceoirs material cut off from contagt with The lead 210 formeVy decay of atmospheric ,the dtmosphere, such as the carbonate species radon enrs the hydrologic cycle principally. in gi*nd water, decreases at a xate con- throughrecipitation. A smaller part is ie- trolled `by .the Carb 14 halfilife The car- ffected by moged fr m,the atmosphere ,as dry fallout. bon-14 to carbon-12 l tio is als he oceans f .excliangeOf carbona betw n the water Most of t e lead-210 falls on where it finds use as a tracer for he investi- r and aquifer, biocheinica , andpossible reactions with silicates. Compensation for gation of vertigal mixing. Some jead-210 e%. exchange effects-has been attempted through tersterrestrial , surfacewaters' and the the carbyn-13t( carbon-12 ratio (Pearson, permanent snow fields. The half -life is con- 41. , 4966). . a i 4 venient dating more recent snow deposits,

0 .4 . and thentural level of lead-210 has not been ,Cesium -137 and cesium -134 :- upset by huclearlreapons testing as is the , case with tfitium. Estimation 'Of thelead:210-ik Elhven, cesium isotopes ,are fission prod-. ut through precipitation, a iequireientj$,. lucts, but usually; only cesiu 37, is signi.fi- Nant to water cruality. Cesium-134 is proi dating of show and ice,.mupt be based on duced inefission by the neutin activation of actual measuremerkts of the lead isotope since cesium-133, a fission product. The half-life of calculation on the baks ofievilibriumOith; cesium -137 is 30 yr and that of cesium-134 'is prevailing radon cioncentrations is. .dot at--,, 2.7yr.Cesium-137hisbeendepoilited .curate This wasShownEby Patterson and throughout the world, with much higher con Lockhart (1964) who nide a latitudinal Sur- .."' lcentrations in the Northern, Hemisphere than vey of lead-20 in ground-level air. 4. ,----

a 7,, 7. ) 4 I TECHNIQUES S OF WATgR-REsOUAtOES INVETIGI§TIONS, ,r , - t-- . lead-21131;c61. re it;:kflirecipitationap- and the specineiativity.ofhoriitin232:Isap- PeVsto vary greatly with, individual stoma-, iiraximatery cete-third tha -cif tranium;238, prWably depending on tl* trajectory -of the the world active' invent° es of radium-226 air/ mass. Rama and Goldberg (1561) 're- and yarium-2'S8 shwa. roughly equal. -ported 0 05 pCi/I for. surface ocean water World activity inventor* for radiumr224 and 0.13 to 6.7 pCi,'1 for Colorado River wa- should also be equal to that M radium:228. ter. lioltzmaun '(1964), using the more sensi- since the two are in.radioactive equilib_rluni.

, tive--210 alpha-cemiting teChnique; The locarrelative,abunden-ceS of the 22¢ anti /found an average of 0.127 pp/1 of lead -210 228adiiini Isotopes maY vary gTeatlyi how- in untreated Illineis sUrface waters andio.054 : , asafunction of fke local ufaiiiVm tor, PCi/l. in 'well waters. 'As expected,; the sorp- thorium tatios. Afso:thete may ,be 'extreme ,tion of lead by soil reduces the concentration_loca variations- in the ratio'o'1 radium -228 to insound water. HOiltzmanhfound,that lead- radium -224 beCause the latter is producs'l. 7210 4ncentrationsn potable 'waters' of from the former through an. actiniiim and a noig were generally smucydelow radium426 thorium isotope. Because the geOclemistry of concentrations. actinium and thorium are signrAcanTly'diff-er- efit from that Ofc,rhdium, there is great ipp- Radium portunity for locardisequilibria. Radium is a radioactive-member of the,Radium fs found in waters from most geo7 - alkaline-earth family th'as widely-dissemi- logic tertanes becaae Of the wide distribu- nated throughout the ust of the Earth. tion of theivarent elements in nature. ton- Pourisotopes of radium, are membtrs of the centrationsof radium -226in freshwater tilreetatural-madioactive series The isotopes usually aye less than 11-21-pei/l.' Concentra; wig' their natural'series nd decay data are of radium-226 in,',,the 'Cambrian and .ensOrdovicianlimestones. c North Central listed below. . Ar- tnited States -often exceed 3 pCi71, and in / .4; Decay, isovopeir Sales Halt-life mode 'certain aquifers of,the ColikradolPlatead, the Radium-223 Actiniurp 1,1.43 d a concentration may be.intiel higher (gicott and Radium-224 ___!--.Thorium 3.64 d a it Barkers 19 Water that 16aches Was. 11,Radium-.226 ____ Tranium _r91,602 yr fi jiles from uranium, 3.0ifind milling op- Radium-228 ____Thoriurn 16 5,75 Yr . , eratimipmay contain raditim at much 'higher The-concentration the adipm isotapes levels.' . 'in geologic and hydrologic Materials vag, While most of ,the, kaditum investigations 'greatly in nature depending on the uranium. ,have centered Olitiie1 22 14otopie, Work iii.thei and thorium 'concenations'in the source and U.S: Geological Survez has shown .Ihe im- the geochemical history of the ?fta,te;ial., porbance of radium-228. Johnson 1,1971) fe- .Cheinically, rium is anarOgous to fitill L ported that concentration of radiuma3,28:in 11.111'; the carbonates.. aulyfates, 'and obrom s sever-al streams of the Front Range near 7", are inNuble, while the chlorides, nitrates, Denver -exceeded the ooniekratithLof radiz_ and Vdpoxides aresoluble in water. Thedi--urn-226. This agrees*itti the ..twice normal ltributikp of radium is governed litre by the.abundance ratio of thorium to`uraniuin for ,distribution -of uranium and thum, how-.the area. Krause (1959), repo edrelatively ever, than py the geochemistry of radium. high concentrations, of radium 228 in wells. Radiutn-220 and radiuni-228 are the Most-tapping deep ground-water aquifers in Iowa, important isotopes of *radium 'found in water Wisconsin, Illinois, and Missouri. . 'because of their longer, halfrlives; health' sig- 411 radiuin isotopes are hazardouslibecause nificande, alid as .geochemical indicators of of', the bone-seeking. properties of the ele- uranium 'at.,_ d rium respectivtly. Qn the nt. Concentrations in the bone can lealitto basis that the Id abundanet of thorium Is ncies. The_tr.S.Public Health Service approximately three times, that .of uranium has xe orninended 3 PCi/1 as the uPper, limit , , I 1 r\ ' r - 'METHOD'S EO'R DETERMINATION..0V RADIOACTIVE SUBSTA410E8 7...

, raum-226 in water-for consureP;1-.°140-16 are reporte as ruthenluin-106,4101- iqn. The U.S. Nuclear'gegttlatorY Convis- though; rutheniuin:10may.so )Aprte,sent sion (NRC) ,976) gave the fdllowin in' the sample/After 8, inorit s decay (6 half-

-PrigsSible conceiltngtibns of ratlioactivi srin trlives), the ruthenibm-103 .cohcearation. is effluent (TCRA.)- vaitt.es for radium (solubte)4 tjtually insignificant in waste solutions th t reletsed water bodies -ace e by the-public: Strontium -90 Nu-Clear s-fisign -'Radipm-234r, ti_ 700/g1/1 r Radium-224 2,000 Kin isotopesprf strqltium :stIontiuin-90 If 4 ' 1 :Radiulin,-226 30 pti/C, lie 38.9 yr) and.,sontinn1-89 (tiaif-life 50:8" Radium -228 30 pCI41 d) .Al;ty.likiugh the tte ha.4 4he "W.'ate'r Qpality Criteria ',1972'(gPA3., greater activk cngerifilf-life of `"tron7 .. . .- 1973,) recommended aradium -226 intake. tiurnzta0 makeA it In gj.g4gtcant, to World- :lima 'of. 0.5 Vi /d: Assumini,Tha 2,0 d -Corr- 5vide 7'veillr Except. for s'ElniPion rate, this is* eqbiiv,alent:* a 9:25 .,Short- pez16ZfilOwinatmospheric nuclear pCi:/.1. Concentration liiilit. strontium -9fr'sthe pirellominant° ,!,!.,, Three analyticalmethodsjor,,..0. radiurn'is.,o- radioiXitope of this elemteon the Earth's ;topes are reported, e4Choserking a diffeexit Surface. This nuclide is now widely purppse.*A. determination of the groq,s -al tributed, man,:s environment,,fromtrato- radioactivity of 'radium is the simplest DiA,v,.sph'eric and. troposPheric4alloui: Higher - 0442 cedure and "is, satisfactory where identitiffk-'centrations existin "the Northern ILIeM1-, -tion Qindividual alpha,emitting isotopes iS sphere. It is 'Often ;detected in ils, foods, not =ru,ired, A second proceduire. is specific water, and biological materials.he "Water' , . for radium-226 and' a third for radium-228. .,Q lity Criteria, 1972" (EP.A; f9 3) recom- in' : . mended Ant on strontium-90 intake Rutheilpin-106. anitt!!iiitheni um-103 water used for public supply is 5pd/d. Assuming, a 2 rd. consumption rate, this is -Ruthenium-106 and ruthenium-103 are the important ruthenium iicttepes produced in equiyalent'to a 2.5 PCi/1 concentration' limit.. nuclear tissiOttel, may be present in'pre- cipitation :and surface waters after atmos- Tritium ,(hytrrogeh-3) puclear. testing. The short half-life of Tritium is the radioisotope of hydrogen ruthenium-103. (39.8 d) essentially, rules out'-i,vith atomic weight of. 3. It decays by pure its presence in ground water. Ruthenium-106 beta emission with half-life of 12.33 yr: The (halfllife 368 d). may Abe found in ground beta particles- have an. overage energy of 5.7 Water in the, immediate vicinity of under- keV and makimurn energy of 18.6 keV. Triti- ground.nuclearftests. Both isotopes are beta um is 'formed in the upperatmosphere by emittgrs'withmaximurhenergy of 0.0392 cosmic-ray spallation and by the interaction Melifor ruthenium-106 and maximum'ener- of fast neutrons. with nitrogen: gy of 0.70'MeV (3 percent) and 0.22MeV 1N+ (97 percent) for ruthenium-103. Ruthenium- 106 is determined by counting' the daughter, The natural production rate oftriti4m is -106, with which it is in secular equi- on the order of SO atoms per square centime- librium. The more energetic beta particles of ter of the Earth's surface per minute. (Kauf- rhodium-106 (3.53, 3.1, 2.4, and 2.0 MeV,) man and Libby, 1954). are more easily, detected. Tritium is also produced by thermonuclear The NRCPCRE value for ruthenium-106 weapons testing. The firsttritium from this in effluents released to uncontrolled areas is source was detected in 1952, and1i3 1954 the 1 x 10'.p.Ci 'ml (10,000 pCi A) . Ruthenium thermonucleartritiumwassubstantially concentrations determined by procedure R- greater than.the natural tritium. (Begemann

.0:77:i. TECHNIQUE OFWATER-RESOURCES INVESTIGATIONS . and Libby, 1957). Thermonuclear tritium tritium inventory is substantial. Sources of - reached a Peak in 1963 when the concentra- tritium _have. beenreviewedby ,Jacobs tioo in the Northern Hemisphere exceeded (1968). the natural /level. by approximately 3 .orders Determination of tritiumfIclioattivity is of magnitude. . , complicated by the veiloud, energy of the '.Tritium is Principalof interest to the beta radiation which necessitates mixing the hydrologist as .a water-d ting tool and asa tritium intimately with the counting medi- tracer, introduced either naturally. 'or arti- um. `Gas phase counting is carried out by ficially, -for investigatinground -wader hy- introducing the tritium as a gas (HT) into a drodynainics inre's of rela0ely rapid flow. proportional counter containing the proper The,. tritium dating of i.rou.nd.water that en- pressure of hydrocarbon gas to assure opera- tered as recharge before "1952 is basedon tion in the proportional -region. Liquid scin- radioactie decay of. tritium and the "Pre- tillation counting of tritium is carried out by - biomb" COncerktration'of iapproXimately 8 tvi- Mixing the tritiated water sample with .an tium units (Ti), (t' Tu =1 T atom /10'" H organic scintillator suspended or dissolved in atoms) determi ed by''KaUfmann and Libby an organic' medium compatible with water. (17341. The efficiency of gas phase counting may be ,,Thel dating IA' ground 'water (originatingas very high, 60-80' percent. The efficiency of recharge_ afttik195.4.is based on the correla- liquid scintillation counting is on the order tion of triiiuni.ConcentrAtions in the ground of 20-25 percent. water with known fallout peaks. The applica- Since the decay rate for 1 Tu concentration tions of tritium hihydrology are reviewed by.in water iA only 0.007 dpm/m1 and the back- Thatcher (1969). ground count (gas counting) is on the order Tritium is also of interest in public health of 2 cpm, it is obvious that enrichment of the,. inasmuch as concentrations much exceeding, tritium in the water sample is required when the natural, level may be released to the en- low concentrations of tritium are to be de- vironment in the course of tritium tracer termined. Enrichment is carried out by elec.- riMents,'nuclearpowerproduction, trolysis using essentially the same process as .,,weap ns testing, nuclear waste disposal, and is .used for the preparation of heavy water. "Plot share" activities: "Water Quality Cri- Passage-of electric current. through water re- eria, 1972" (EPA, 1973) notes that a tenta- sults in the liberation of the light hydrogen' ive limit of 3,000 pCi/J of tritium has been isotope (protium) at a faster rate than the prepared for the revised edition of ."Drinking Heavy isotopes (deuterium, tritium), thus en- Water Standards:: The NRC (1975) PCRE riching the, latter in the residual water. value, for tritium in effluents released to un- controlledd areas is 3 IA Ci/l. The liquid-scintil- Urariium latiiin counting technique provides all the Uranium is widely disseminated in the sensitivity required for monitoring tritium lithosphere, and most natural waters contain concentrations at the levels significant to detectable concentrations of this element. publie health. . The avrage concentration in the ocean is Although tritium is not a major fission about 3 p.g/1 (Rona and others, 1956). The product, there is a significant production of uranium content of ground and surface wa- tritium in nuclear power reactors. The great--ters .varies greatly, from less than 0.1 pg/1 to er part-nf the tritium remains enclOsed in several milligrams per liter (mg/1). In most the fuel 'element until the latter is dissolved natural waters the concentration is less than for reprocessing. The production of tritium 10 /4/1. The limit on uranyl ion (UO2+2) in in reactors depends greatly on the reactor publicsupplies(Water QualityCriteria, type, and estimates of tItial production are 1972 ) is 5 mg/1. subject to many uncertainties. It seems clear, Dissolved ufanium in natural waters exists however, that the reactor contribution to .the principally as uranyl in (U62+2) which may , METHODSFORDETERMINATIONOF RADIOACTIVE SUBSTANCES be complexed with carbonate. While uranium 23in water (Chalov and others, 1964;Cher- in surface waters is glmost entirely hexa- ntsev and others, 1961; Thurber 196) valent, there may be an appreciable percent- Depletion' of the 234 isotope is less cOmm n. age of tetravalent uranium under reducing Isotopic dating'of waters, correlation of dig.- conditions found i5 some ground waters. T equilibria pith rapid leaching (important in latter is predominantly 'completed and pollution studies), and .the geochemistry of highly insoluble in basic solution. uranium triansport are examples of the possi- 'Uranium in natural water is important in ble applicatioi of uranium isotope disequi- geochemical 'prospecting 'and',as an indicator libria studied.: of pollution from mining operations. It is un- While the usual objective of the analysis likely that uranium could reach 'concentra- is determina.tiOn OfYthe pranium-234 to 238, tions significant "to health, aqhough a high activity ratio; it is,-also Possible to determine concentration of urahluin- could be indicatire the activity ratiolof the 235 isotope to*238. of _possible high levels of 'the much more The uranium:230 to V8 ratio is constant hazard6uS radium isotopes. (1:137) in the abse4e/o"fertificial depletion three. natural uranium or enrichment.Thereate4 :an increase of the There arethe 235 isotope is IleasOn to-su'speOth.6 presence isotopes: of material 1Srocessed for nuclear fuel. Abundance Half-life I Isotope (Percent) (yr) U-238 (U series) ,v- 99 ,127 4.51VO° Collection and -treatment U-235 (Ac series) 1- .72 7.1 x10' U-234 (U series) .0(3 2.47x105 of samples Uranium-234 is related toi raniurn.-238, The principal requirements to be met in the parent of .the uranium decay series, by sampling a water body for the determination the following decay sequence: , of radioactive constituents are the same as for other constituents, that Is, collection of Unsff.Th21' (24.1 d)1.Pa2" (1.18 min)_.U2", samples in an orderly sequence, that provide a The total world rallioactivities of the 234 representative analysis of the water body and 238 isotopes Must be equal since the two both areally and temporally. Considerations are in secular equilibrium. Local physical and involved in setting up a sampling program chemical effects may result in local disequi- that yields the required representative. infor- Llibria -which are of geochemical interest and mation are discussed in detail in an earlier have been given intensive study. Disequi- chapter (Brown and others; 1970) in this libria may. result from physical or chemical ,series of Techniques of Water Resources In- mechanisms. The principal physical mechan- vestigations of the U.S. Geological Survey. ism is the energetic alpha recoil associated Reference is made to the earlier chapter for with, the decay of urapium-238 to t orium- disciission of site selection, sampling fre-, 234. This may rupture chemical .bo ds and quency, equipment, sample identification, and .. permit thorium to go into solution in ground other elements of an organized sample-collec- water where it .decays to uranium-234. Al- tion program. Guidelines for the collection thouth thorium is considered to be sorbed by and field analysis of ground-water samples sediment, the presence of dissolved organic are given by Wood (1976)." If analyses for matter or other complexing agents may tend the determinations described in this manual tostabilizeit.Since both intermediates, are to be made by a U.S. Geological Survey thorium-234andprotoactinium-234,are Water Resources Division central laboratory, chemically different from uranium, chemical the appropriate section chief should be con- differentiation may occur. Difference in oxi- tacted. Specific information can then .be ob- dation state between the 234 and 238 isotopes tained for collecting the samples, obtaining can have an additional effect. These effects the necessary sampling supplies, and so frequently lead to enrichment of uranium- forth. 10 - .TECHNIQUES WATEit-itiSOURCES INVESTIGATIONS a The overriding problem irisampling for'repor- in the. literature are based 'on dis- radioactivity is preservation o the extremely tilled-titer solution, and thus are not entire- dilute conceAtration of radionuclides, (usually ly rele ant. in ,.t enanograni-, andpicogratn-per-liter Similar tests with uranium showed no sig- rang') in their original conditions until the ioss under any condition, kexavalent anasis can be performed. While preserva- urani-rn is stable in natural water exposed to,';' tio I of the original -condition of-the sample is the atmosphere, particularly when bicarbon- a geral Oblem in water analysis, the alte is present. Earlier tests by Janzer (un- extre ,;. dilution of the ratlionuclides greatly /pub. data) are in agreement with the above,? inten $4 es the problem. Although/ extensive/ findings.Si rkace-water samples were col- research has been given to the c emistry of / in polyethylene bottles under three extremely dilute solutions; theraetical re- conditions:/no treatment, filtered and acidi- sults in terms of preservation othe sample fied at time of collection, and filtered at time have not been completely effec ive. indeed, of collection but not acidified. The concentra- conclusions from different invtigations are tions of i tadiufn, uranium, and gross alpha- often at variance, and indicateat the essen4°beta actiVity determinecl repetitively in all tial phenomena are not com i tetely under/. three sapies agreed closely and did not sig-

stood. . 1 nificantlchange with time. Early in the history of rad chemistry the Itisgenerally recommended that acid term "radiocolloid" came intuse as a result, should be added to very dilute solutions of of apparently colloidal phen menabserVed trace e ements for the purpose of minimizing in radioisotope solutions (diy3/4ic,se aration:sorpti ri loss of trace elements from the solu- nonionic migration- behavioin thelectric Von.while it is iii contact with a sample con- field, and so forth). Altho gh rad bactivity iner. This is the practice recommended prOduces,electrically charteCente s (which. herein, but it should be noted that the experi- could attract othei- ions tform aggrega- mental evidence is not at all conclusive. There tions), it iS unlikely that t e phe omens in appears to be significant evidence, from both very dilute solutions ofadiois pes, are radioactive and ndnradioactive work with greatly different from ph nomenin very trace elements that the individual chemistry dilute solutions of nonradio ctive inns. Starik of the elements must be considered, and op- (1959) has exhaustively reviewed he earlier timum preservation techniques for each ele- work and finds both colloidal and n ncolloidal ,ment, or for chemically related groups of behavior depending on conditions. elements, are "required. Starik (195?)re- Starik also investigated the effec of filtra- ported, for example, that polonium ivsorbed tion and found that radioisotopesere re- most strongly (on glass) at pH 4.5, and while tained in varying ratios by diffent filter )the sorption is much less below pH 4, it is media depending upon the pHnd ot ler reduced to the minimum above pH 82He also chemical fa tors. Overall; both sotion loss reported minimum sorption of radiotantalum and filtrati n loss are functions othe c n- at pH 10 with maximum sorption at pH 3.5, centration, pH, oxidation state, electrol te and maximum sorption of -95 at pH composition, and presence of trace' s of col- [9. loidal material in the solution such as col-: Ground-water samples are usually clear loidalsilicaaswellas numer usother initially but may become turbid as hydrated factors. Many observations of "rad'ocolioids'' and oxides form on expOsure are apparently attributable to sorp ion of the to air. It is essential to prevent the formation radionuclide on traces of colloidalilica. of these precipitates becauSe they can copre- Tests suggest that the sorpti n lossin capitate radioactive elements. Precipitation natural,water samples, as again. t sorption of hydrous oxides is prevented by acidifying loss in very dilute distilled-wate'solutions, the sample after filtration. Sufficient reagent may be relatively small./Manyif the tests grade hydrochloric oil nitric acid should be f; METHODS FOR DETERMIN! TTON OF RADIOACTIVESUBSTANCES 11 added to the filtered sample to obtain a pH more acid. Test withpH paper. Seal the 1 or less. cap withtvinyl tape. out appropri- A 4-liter sample is usually adequate fDr 3. At the time of collection, fill ate sample data form ascompletelyvas radiochemical analysis of gross alpha, -5S in -n- possible and 4nclude with the sample beta, uranium, and radium. Additional s analyzing. ple may be required if other analyses or e- the manner preScribed by the laboratory. When compiling the results runs are desired. Recommended samp__ng of the 'analysis, it is essential tohave procedures for surface and ground waters pertaining are described as follows' - all the inforntation posSible to the conditions which existedat the 1.Collect and store the samples only in spe- time the sample was collected. cially. washed and labeled 4-liter poly- 4. Box the samples in thecartons provided, sampling bottles provided by and ship as soon' as.mossible aftercol- the radiochemical laboratory. The bot- lection. Be"sure tha %'return address is tles are cleaned by the following pro- -on the shipping label. cedure': Wash with tap water ; add 10 5.During winter months, it is .essentialto ml nitric acid, and refill with tap water; mark the cartons "Water Sample. Keep allow to stand overnight ; empty, and from freezing." finally rinse several times with small When sampling a ground-water system for amounts of distilled water ; and drain, im- and allow to dry before capping and tritium or carbon-14,:it is particularly portant to select the sampling wells with care storing. so that a representatfvesample is obtained. 2.Surface-wtter samples are collected to ob- The well should, be properly Sealed toMini- tain a representative sample of well- mize surface -water contamination,and it mixed water at' a single point, generally should preferably be in constant use. Ahigh- - near the center of the stream orriver. if ly productive well is preferred to a lowyield possible. Preforably only clay- 'or silt- well. The well should be thoroughly pumped sized particles should be present in the before the sample is taken. A perfectlydry sample if samples are to be analyzed bottle or barrel is used. During and afterthe for suspended gross alpha andbeta collection of the sample, minimizecontact radioactivity. No filtration or acidifica- with the atmosphere which may contain car- tion ,is usually required if dissolved and bon-14 and tritium- at concentrationsranging suspended gross alpha and beta radio-.from several-fold to several orders of'magni- activity and dissolved radium or urani- tude higher than the radionuclidein the um are desired. (Otheranalyses may water sample.- require special handling,. and the ap- propriate Central Laboratory section chief tshould be contacted for specific Calculations of radionuclide detajls.) Leave an air space of several concentrations . centimeterstoallowforvolume changes with temperature. Seal the cap The method used to calculate concentra- with vinyl tape: Ground-watersamples tions of ~adionuclides for most of the deter- should be filtered through a 0.45-mi- mination, in this manual may be expressed crometer membrane filter at the timeof in'the form of a general equation. Exceptions collection. Add sufficient reagent:grade are the calculations foruranium, uranium hydrochloric acid (preferred), Or nitric isotope ratio, and carbon-14 age. The general acid, to lower the pH to approximately method of calculation compares the activity 1. Minimum value of concentrated acid of a sample against the activity of a stand- that should be added to a 4-liter samp:e ard, and coirects for decay of the radionu- is 8 ml. Alkaline waters may require clide in the sample between time of collection 12 TECHNIQUES OF WATER-RESpCifcES AIVESTIGAT:ONS , and time of analysis. If the recommended specified for the.determination. E. 'practice of minimizing time delay between is usually determined by analyzing sampling and analysis is followed, the correc- standards' in, the same analytical tion for decay through this inte?val becomes procedure as for Samples (a modi- negligible for many radionuclides. fied prrocedure is used instwO meth- A more significant cdtection is that neces-? , ods described in this report), sitatal by decay of the standard between the f =fractional recovery of the nuclide in date of its certification bytthe- National Bu. the sample,, reau of StandardS or other supplier) "end A A-tdetaY ctnstant' of the nuclide deter- the date of its use to calibrate the analytical in 2 method. This time interval may,famOunt to mined by: , several years and j'Al significant, relative to 7 1/2 the half-lives of several radionuclides: where, .The following general equatii---2-applieS; T11 = half -life of the nuclide of in- when In-Erowth of daughter activity is not a terestintkeappropriate factor, aird when the half-life is long relative, _ , time units, aril to The counting time., Thisisthe usua4- It= elapsed time between collection of the 'situation. sample and count of radioactivity nooe (in same timelnits as used fi r it). KVEf (e-x4 -The counting efficiencyffi .factor,E, is lcu- where lated by the following general equati?n: C= concentration of radionuclide. This is E (2) usually expressed in pCi/I: c= c, (6, -t-\b- 2) . Averake :count- rate of where thee sample in counts per minute- c =average count. rate of standard in (cpm) after correction foi back- cpm after correction for. bacli- groundk,and blank, ground and blank, w ere ddisintegratiOnrateof 'standard average gross sample count.rate (dpm), (ePrO, _`fn= fractional chemical recovery of the b,=averagf blank count rate nuclide in the standard, and (cpm1and b,=averag bickground countrate t,;= elapsed time between certification of (cprn) the standard and the count, in Usually' b1. and are experimental some units as the respective A. -lydetermtnedasa combin In the determinations of gross alpha and quantity. \ beta' activity, cesium-137 and 13+4tritilm K= factor to convedisintegration rate (without, electrolysis), radium-228, radiuM ind.isintegr donsperminute as radium -226, and radium226, the chemical (dpni) to cur s. The value ,of recovery factors f and f are not determined. for different co centration exp-es- The preluct Ef,, is determined by counting sions (C) is: the star:arci and is substit:: A for Ef in C K eqUatior1. This Ordcedure i.valid when f mCin 2.22 x10" and f equal and reproduci')le (within ex- uCi/1 2.22><10' perimemal -andeffecti--ely cancel out.. pCi/1 2.22 The usua. situat-Dn is that f Lnd f, are very V = volume of sample inilliliter. close to unity. E Counting efficiency.r the Equations I. d 2 apply wnen the sample underthecounti gcohrlitions and standard counted under the same

, '7 MeTTIOR*FOR DETERMINATION OFRADIOACTIVE SUBSTANCES 13 conditions on tbe same detector. This is. the normal situation. In the dete* 'inationof radiuM-226 the indiiidual sam and, stand- 'ards are counted in individual alpha scintilla- ,tion cells, each of which has its'own counting. efficiency, (cell constant). Hence, in the 'de- termination ...pfradium -226 an individual'. counting effwiency is dete/mined for each cell. In the determination of lead-210, radium- 26,, and radium-228, the radioactivity Count isade on a relatively short-lived daughter of the nuclide determined. This necessitates . theintroduction of an "in- growth" or"build- up" factor, whi0 ig the fraftion of'the equi-, librium concentration of daughter that .had grown in at the timeOf separation from the 42a rent nuclide. Since the daughternuclides 100 °200 . . 300 are relatiAly short lived withrespect to the TIME IN. HOURS counting time, it is necessary to introduce a A-6 IN-GROWTH OF DAUGHTERNUCIADE iN correction factor for decay during4fhe count- TIME t1 ing interval: With radium -226 and radium- '(NUCLIDE ILLUSTRATED HAS HALE*Q_IFE 228 it is also necrOsary to introduce a factor OF 3;,S2d) . B SEPARATION OF DAUGHTER FROM PARENT that corrects for decay of the daughter dur- B-CDECAY OF .DAUGHTER BEFORE COUNTING. ing an aging prior to counting. TIME INTERVAL t2 Altho-ugh a daughter nuclide is 'ounted (in C .BEGINNING OF COUNT C-DDECAY OF DAUGHTER DURING OUNTING addition to the parent) in the determination INTERVAL t3 of strontium-90, an in-growth factor is,t'- t4 TIME INTERVAL BETWEEN SEPARATION OF used because the daughter is allowedto rea DAUGHTER FROM PARENT AND MIDPOINT a constant level. (99.5 percent ofequilibri- OF COUNTING INTERVAL Ann) befoise counting. The relatio ship of the three correction Figure 1.In-growth and decay °la daughternuclide, factors to theme intervalsinvolved in the significant time intervals. counting of a dahter nuclide is illustrated in figure 1. The figure shows growth and de Y= (.0ecay of daughter between cay of the daughter with .time andidentifies 6epar-alron from parent and begin- the significant time intervals. The general .ning of count), equation for use with ingrown, nuclides is: Z (decay of daughtduring 10006Z C- (3) KVE f (e-xi)XY j counting period), where .04. where C= concentration of radionuclide. This A= decay co nt of parent nuclide, is usually expressed in pCi/l. t- elapsed time of parent between e= average count rate of sample incpm collection of the sample and after correction for background - separation of daughter, - and blank, Ai =decay constant of daughter nu- X = 1- e-Aii (in-growth of daughter), elide, A CV-11!( 14- TINEIND IUES OF WATER-RESOURCES INVESTIGATIONS (3, ti= in-growthtimeofj daughter,.Fitteltable solids. Those dissolved solids cap- r point A to B (fig.), able of passing-thuugh a 0.45,micrometer t2= delay before cuUnting, point IT to membrane filter and dried, tq constant it . C. Separation of the daughter weiOt at r0°C. from the parent at time B, and Half-life. Th time required fof the decay of t16 time interval for counting of the a given quai)titiv of a radioactive substance - daughtet, point C to D. ,to one-half its_origal mass ;..thus it ism ) K, V, f, and E are as\ 4efined for equa- measure of tyre rate of su qh'processes. Minimum detectism)lev411. The least amount , tion .'ThefficOlicy 9ilduiation'fOr ingrown nuclides is or concentration that canbi'e detected an'd quantified by a 'fest methodi E en. 7--: (4) Nonfilterable solids.---those solids Which are , df ( e--',..) X Y ' 3 retained by 'a 0.45 micrometer membran with 5mb015,1:riti units asfrdefinedn equa-°, filftr and dried to constant wgightAt 103°7: tions 2 and-39 , 105°C. - xi )",- I3ecause of the short counting time permi -PreciSlhon. The degre'e- of agreement Q re- tO by the higher concentration ofbthesta4 peated measurements of tl}ie same proporty and, the coventing time is short relati3zeto the: '!expressed in tien:ryi of dispersion of test balf-lifeC Hence the scOrrection factor for results about tie meartresult obtaineti by

decay during counting is eliminated. , gesting of a horriogeneo6 h.?nple(s) uancleri The general equations 'are modified in di- specific conditions. 7.,cordarice with specific conditions prevailing Sorption. A general term for the processes of in the determination q.;individual radionu- absorption and adsorption. ° ,\clides. For example, f and f are eliminated when chernical separatimis are not used or , when the chemical recovery factor is included Selected references in the deteination of overall efficiency. Decay to . are re eliminated whelk the half- life of the elide permits. Principles of radioactivity The terms used in,equations 1 to 4 are not nuclear instrumentation repeated under/ the calculation section of the Friedlander, G., Kennedy,, J. W., and Miller, individual determinations u less required for J. M 1964, Nuclear and radidchemis- clarification. , try: New York, John Wiley and sons, 520 p. (Glasstone, S., 1958, Sourcebook on atomic OSSOly energy: second` edition, D. Van istostrand Confidence level. The stated probability, un- Co., 525 p. der the experimental conditions employed, Hogerton', J.Ti'.,1963, The atomic 'energy that t`he value will be within the interval deskbook: New Yprk, Reinhold Publish- indicated by the prtcision around the ingCo., 623 p. - mean. Overfnan R. T., and Clark, H. M., 1960, , Decay. The spontaneous retdioactive trans- Radioisotope techniques :New York, formation of one-nuclide into a different McGraw-Hill Book Co., 464 nuclide or into a different energy state of the same nuclide. Every decay process has Compilations, of data on a definite half-life. radioactivity and biochemistry Dissolved. The sample is filtered through a Holden, N. E. and Walker,-F. W., 1969, Chart 0.45 micrometer membrane' filter and the of theuclides: Schenectedy, N.Y., Gen- filtrate analyzed. eral E1 stria Co. e

METHODS FOR DETC,RMINAT1ON OF RADIOACTIY E SUBSTANCES 15 , Lederer,, C., I-fail:rider; J. M., and Perlman, I., Wahl, A. C., and Bonner, N. A.,195,g,' Radio- K. 1968, Table of *topes :6th ed., New activitItapplied ,o' chemistry :New . Wiley and sons, 536 p. York, John';'.ey and .Sons, 593 p.. N4tiorial Acaderr f Sciences, tN.Taticnal Em- searchCour :960-62, A series of pub'- Radioactivity regulations and lications or :iochamistry of 'the ele- scOpty ments begin_ -2: with N4S-IISpublica-,.. tibn no. 30 The radiochemistry, of FederalWater Pollutmn.Control Adm cadmiurq:. R.,--isions of publications \ ,prf- tion 4nowEnvironfriatale P

) several elements 'have since been pub- Aitncy), 1968, Water quality lished. ft' c 2144). d**,t. Dtt)t. of Health, Education andWelfare, General S4ety Committee of the t)lic kIealth Service% 1970, Radiological turiniChemists Assock 1 4 or heter handbook : 4457w .safety in the labra o ew York,an Nostrand, 221 p. ritavity in the environment /ntert 7 altomic Energy Agency, Vi'en- Adams, J.A.S., and Lowder, W. X., 1964, The n 960Sairhanlineotradioisotepes, Natural radiation erffirelinmentil. William N la'ealthe hysics'adnduni: Sgety series no. 2, 120 p, , t March' Rice UniveriK'UriVersit# of icago: Press, 1069 p. 1(962,afe handl ng!`of radioisotope- . Jacs, D. g., 1968, Sources oftritium acid 'Safety series, no. 1, 159 p. its behavicir upori rele* to the environ- Morgan, K. Z. and Turner, J. E.. 1971, Prin- ment: U.S. AtOmic Energy Comm, :-;ion ciples of radiation protection : New York, TID-2463 John Wiley and Sons, 598 p. Saenger,°E. L., 1963, Medical aspects of radi- -Radion,4ttitte methods in ation accidents: AEC contract AT (30- hydrology 41.)- 2106 With University Cincinnati, U.S. Atomic Energy Con-_-- .,328 p. International...comic Energy Agency,, -ien- -U.S: Dept. of Commer National Bureau of na, 1967 I; isotopt;te.ch- Standards, 1951, Ctrol and removal of Arology': 175 p: -niques in radioactivecoritanationinlabora- 1970,s,,-)tope hydrology( Latest in a tories: NBS Handb... 48, 24 p. o-_' 'symposia pn is(topi..tech- series 1953,..Maximum peer missible amounts e c Toearli- niques in hydrOlogy. References of radioisotopesin the human body and er symposia are i_rten in the 197 ubli- maximum permissible concentrations in cation), 623 p. air and water: Report of subcommittee * 2 of the. National Committee on Radia- Radiochemical anaivtical tion Protection, NBS Handb. 52, 45 p. methods 1959, Maximum permissiblebody bui- -otitharneli C. E., 1,9-Appli- dens and maximum permissible cqncen- spectrometry: sec: :Id edit. n trationsof radionuclidesinair and Adams,F.andth:1.7-2,'.R., ( Pe.- :a- water, for occupational exposure: Recom- mon Press, 747 p. mendations of the National Committee NBS Handb. 69, rrukhina, A. K,. 1VIalysheva. T. V.. on Radiation Protection, skaya, F. I., 1967. Chemical analysis of 95 p. radioactive materials: Clevelan CRC. U.S. Public Health Service, 1962, Drinki g Press, a division of Chem' ic:_lRut:-)er'o., waterstandards,1962:U.S.Ptis originally published in Mo:=..ow, 3;30 p. Health Service Pub. 956; 61 p. P6 TECHNIQUES OF., WATER-RESOURCESINVgSTIGATICTSIS 11. ' , U.S. Environ ental Protection Agency, 1973, Jacobs, 0. 'P.1968, SOurces of trif m and its .,13e-, "--1. Water qlMy 'criteria, 1972: 'EPA -R3.- hav upon release to' the e oninf,,nt:U.S. Atom c Energy Comm. TID-24685, -.. _73 033., U S. Govt. Printitig-Office, .Wash. Johnson, S. 0%, 19,71, Determination of -adium-228 594 P., ;? 40 innatural water: U.SGeol. Survey Water- 1.970anIcriin primary drilAking water Sapply Pap regula4n: Title 46, Code of Federal 'Khufrann, S:', aina.%.ibby, W. 1954 nenatural ot distribution of tritium: Physical ellview, v. 93, Regulations; Part 141; Federlal Register,. 1337-1311 v.4'0,41050: Aug. 14, - Krause, D.Fh, 1959, (Mes thorium I),in . Nu ear gulatorJommission, 19* Illinois well water Argonne N t. Lab. diol. .Rulei: and ,re tilations: ,Title 10, Chaptr Phy. -Div.Semia_I ualRept. ANL-Zri '1, Code of Fed'eI Regulations,-- gy\ 51-52.. Libby, ,W. .F.,..1455, 'Radiocarbon second Part20,'' Standar,dsfor otecti - tSaiv.Ist Chicago Pres, 12f.p. against ,jadiation, Sept. 1975, 1966, ,Variations in carbon-14 concentra- throughprir19; 1976, 18 p..3 in the atmosphere during the last several? a ytars :TeIlus 18, p, :271-276. di/ Patterson, 7/Z.--L., ;aferLockhart, L.B., 19q4, tre4- Reference)s graphical' distribution of lead -210 in grouhd. leve 4 air,in 'Mt Vatural RadiationEnliircituLent: Barker, F. B John**, J. .,°Edv:mi-ds,, K. NVz and Chicago, TIMM of Chicago Press,.p. 383-394. Robinson, ^B. P., 19651u. eterminationc! uranium-N. 15earsonF. J..; I9q5, ;31,e of C-13/C-12,. ratios ik natural waters: Geol.- Survey Water- correct radiocarbon ages of materials imtniflir Supply Paper 1596-C,5 pt. diluted by limestone: Internat. Conf. on dio- carbon -.end 1.Tritiam Begemana, F., anLibby, W. F., 1957, Continental Dating,6th,Pullsn, water Washington, 7-11, June 1965, USAE Conf. balance,ground-waterinventoryand 650652, ., p. 357-366. storage times, surface ocean mixing rates ar. Rama, M. d Goldberg, E. D., 1961, Lead-210 world wide circulation pagerns from cosmic in ntural w ters: Science, 134' p. 98-99. ray and bomb tritium,Geocltim.Cosmochim. Acta 12, p. 277-296. Rona, ElRabeth,/Gilpatrick, L. 0., andleffrey, L. M., . 195k, Uranium determination in sea water: Am. Brown, Eugene, Skougstad, M. W., and Fishman, Geophys. Union Trans., v. 317,--p-7131-'701. M. J., 1970, Methods- fol collection and analy- 'and Barker, F. B., 1959, R dium and sis of water. samples dissolved minerals and uranium in ground water of United States: gases:U.S.Geol.. .Survey _Techniques Water- °inf. on the peacefuluses of atomic energic 2d, Resources Inv:, book .5; chap. Al, p. 4-15. Chneva, Switzerlami, 191, .P -oc., v. 2,- p. 154L- thalov, P.I., Tuzova, T.A., and Musin, Ya. A °k.., 157. 19644Isoptope ratio o: U-234/U-238 in natura. -Starik,I.E., '1959, Principles radiochemistry: waters and utilizationo the ratio in nuclear -'ublishing house of the Acaaemy of Sciences. geochronology:Izv. Akad. Nauk. SSSR, Ser. JSSR,TrantlationAEG-tr-6314,Officeof (Geofiz, no. 10 p. 1552-61. Tech. Services, Dept. of Commerce-Washing-4 Cherdyntsev, V. V., Gritty,: E. P.,Isabaev, E. A.. _ ..on,D.C.20230. , and Ivanov, V. I., 1961, '-1 Suess, H. Et, 1965, Secular variations of the cosmic- natural cond ions,Radiokhimijia' no.1d ray produced carbon-14 in the atinosphere and 840-848. theirinterpretations:Jour,Geophys.'Res., Cooper, J. A. Rancili, L. A., and Perkins, R. 70(23), 5937-5952. 1970, An anticoincidence-Shielded Ge(L Thatcher, L. L., 1969, Principles of the 'application gamma-raspectrometer and its application of nuclear techniques to hydrologic investiga- radioanalical chemistry pr.olems: Jour. Rac tions,The progressof hydrology:FirstIn- anal. Chsin. 6, 147-163 p. ternat. Seininar for Hydrology Professors, Univ, of Illinois, Urbana, Proc.,. p. Edwards, K. W:, 1968,Isotopic analysis of ura:-- Thurber, D. L.,1962, Anomalous T:-234 /U-238 in ium in natural waters by alpha spectrometr--: nature: Jour. Geophys. Research, v. 67, p. 4518- U.S. Geol. Survey Water- Supply Paper 1696-7. 4520. 26p. Jr. t Wood, W. W., 1976, Guidelines for.oliection 'and \Holtzrnann, R. B., 1964, Lead-260 and polonium-21) fieldanalysisofground-water- samplesfor' in. potable waters inIllinois,in The Natural selected unstable constituents: U.S. C Survey RadiationEnvironment:Chirgo,Univ.of Techniques Water - Resources Inv., nook 1, chap. Chicago press, p. 227-238. D2, (In press). Jr r. , /

r. . 1- Carbon -14,dissolved, apparent age cintill-cOon'methdd, DenverLai)( Ru:1100-76) Liq-ui . ir ,

. \Lr 1. Patameter 001code: Carbon-14,dissolved,-appa rent age (years none atssP rmed,------V .1 . .1 '' 3c2H,-- Calla. \ .1. APplicaliciA . -.1d,N46 4 Tie,1130-aentaitis placed in a taredscIritilla.1 , The.method cRiterintnes,, thellItapparent age' ogn-t ng ial, ieighed, and thendiluted \ of Cm-bon-14dissoliTed the'watet sample. tion slightly, wi a toluene solutioncontaining-A If is suitAtfle -tor the Analysis of any natural; sen-iitiye to low - .water sample from". which 'of dissolvedt mixtureof scintIllato'rs energy betas. 'FirkitiNiip-:of -the sample is r carbon cloq ob Only Carbonih ctinter. form .ciffdissolve IMO, andits hydro' measured in a liquid 'scintillation protluctS%fs deter pined.he ,apparent .age, From*-natiiii of carbon-14 activity to' he Atandai-d, eight of -coon recovered, the apparen age_ detp-mined by cdmparisoss with a the- salpple; may be de-. 34.1.cnown.age (see sec.55.1O),applies only to the .carbon the carbon-14 in the'-s'ample; 'use of'the de- -tined.( requites termination totC date thckvater.itself - a ri,kmber ofadditional' measurements and Interferences 'assumptions ,and a general knowledge ofthe The conversion from CO),. to Callais, ap- geohydrologic syStem from which thesample parently free of both chemicaland radio- was obtained. As notedbelow, a modification metric interferenfes: Duringsample collec of the procedure is d for waters contain- tion and _precipitation proceduresinterfer- ing sulfate in' excess ofapproxithately 206 ence may resMt fromcontact with atmos-. mg/l. phe7e or from lissolved sulfate --icentra- tions in excess of approximately2) mg/l. 2. Summary of method The sample collection ,mustrnin_mizeeat-,, The method is based onihat of Noakes mo:zpheric contact with the water.Sample . and othets''. (1967), Dissolved carbon inthe col.ection*sh-ould be in a closed system from carhoitate system is concentrated from a ,the sampling pointto the collection contain- large volume of water by precipitation of ers. Collectioncontainers (nonnally 15- to carbonate. The precipitateis treated 55 -cal steel drumq should befilled by in-. with acid to liberate carbondioxide, which se:-ting tubing to the container bottlm,and is then allOwed to react with metalliclithium flo--- contirr---:-: until three contamervolumes to produce carbide: passe,through the corzail,cr.The sa7- piing tube:inould be remov,,slowly and 2CO3 +10Li --0Li2C2+4Li20. after re- The carbide is then hydrolyzed toproduce th- container sapped immedia:217 moval of trie delivery tube. acetylene: Li2C2+2H20 4. Apparatus Finally,:; the acetylene is passed over a -doped aluminum oxidecatalyst to 4.1 Beakers, polytthylene, 400 MI. fort* benzene: 4.2 Cylinder, graduated, 50

17 4,1 18 NtecliNiQuEsOF WATER-RE#OUW6E§AINY-E.STIGATICNS .6 Tat 43 Druins, s ,715-ga,1afle55-ifal capa- city okith 1- and .2._.-inch bungs. 92' 4 Liquid scinitllation erbuAter.4 'ndtatin4, ,paRier, pH .2.0-5.0 - V -e. 4.Precipitatorfor bafium carbona to: 4. `(fig 2) -I. -1 '. I...).f.. ' 4.7Tacuum line for storageogetylene \\4nd couersk. ..tion toftenzene .(fig. 3) v . .ti 4.A Valeves for transfer of wateN samplet.. fpm drums:trecipitator. s- . . - ,-- 5. Reagents , -.'-c '1.... ° ' 5.1 Asparite (trade name of Arthur H. Thomas Co..for s od iuriik ydr oxide-imp,rerv- a,nated asbetteer. . le 1 o . 5.2Bci.ri'16 chlorkklanthanum. chloride.: tttonDissolve 290 g:BaC12:21120 and-10 ' g LaC1,,- in (dikilled water and dilute to. 1 rit-er. ,- - - .< < ,5.3'Benzery, speetroscopic grad. e,fre4 of carbOn-14 activity: 5.4Catalyst, vapadium-doped.A1203,,, or Mobil Oil Co. Durabead. 6.5. Dry ice. 5.6IsoproPanol, technical grade. 5.7Liquid *frogen: 5.8Lithium 6.etal,shot,paclied,anti stored under. . 5.9Nitrogen gas. Must be free of CO2. or scrubbed to remove CO2. .10 Qxalic NatiOnalBureauof- Standards contemporary standard. 5.11 Phosphoric acid, concentrated (135 percent). XIG ASS VIEWING PORT 5:12 , pentoxide, gran,ular. . ,COr NEC OR FOR HOSE 6.13 Scintillator solution:10 g 2,5-di- FROM S MPLE BARREL phenyloxazole (PPO)', 0.25 g C STIRRING MOTOR -benzene (dimethyl PRESSURE. RELIEF VALVE 'D POPOP). Dissolvei 250 ml analytical- E IMMERSION HEATER grade toluene. F MASQN JAR G GATE VALVE 5.14 solution, 5 M. 5.15 Sulfuric acid, 0.0164 N. Figure 2.Apparatus for collection of carbonates 5.16 Strontium chloride- chlo- from a water sample. ride solution: Dissolve 230 g SrC1221-120 and 10 g LaC1, in distilled water and dilute to 1 liter. 4 METHODS FOR .DETERMINVIOOciADIOACTIVESI SSTANCES 21

A' CARBON DIOXIDE EVOLUTION FLASK -, L CATALYST REACTION TUBE B. C. D.G. H,"1.J.K. 0 TRAPS M COLD FINGER FOR BENZENES E- 1 N. GAS STORAGE CYLIN-DERS P. Q. R COLD FINGERS F REACTION CHAMBER G-7 VACUUM GAUGES.

.Figure 3. Vacuum line for prepationOf-acetylene and conversion to benzene. the solution in the -400-m1 beaker. Again, 6. Procedu test the pH. If the pH is more 4.5, it 6.1 Determine the volume of water sample is satisfactory to use two 15-gal drumsof required to contain 5 g carbon as 'carbonate water sample. If the pH is still less than 4.5 or bicarbonate. Alkalinitycohtributed by repeat the addition of 50-ml sample aliquots .silicateborate, phosphate, and other basic to the 400-m1 beaker until a pH of 4.5is constituents is included in the fopowing esti- obtained. Collect one 15-gal drum for each mation. of . carbonate alkalinity. Therefore, 50-m1 portion of sample required for neu- the method underestimates the volume re- tralization of the acid Co pH 4.5. Six 15 -gal quitedif noncarbonate alkalinityisalso or two 55-gal drums is themaximum volume present. collected.' 6.1.1 To 50-m1 water cBample in 400-ml 6.2 Collection o/ sample. beaker add 30 ml 0.0164'N sulfuric acid. Test 6.2.1 Fill each 15-gal druiby inserting the pH, usingnarrovr-range indicating paper a hose to the bottom of the drumand 'fill or a pltmeter. If the pHis,above 4.5, suffi- until two or more drum volumes have over- cient carbon_is contained in 1y5,4gal (55 liters) flowed. Remove hose, insert plugs in bunks of the water sample. and tighten securely, taking care to minimize 6.1.2 If the pH is less than 4.5, add a trapped air: Ship to the laboratory taking Ind 50-m1 portion of water sample to care to prevent freezing in coldweather. 20 --js C H N IQU k'SL0 FWA R-RE SOURCE S.,INVESTIGATIONS I N N.g 6.3 Collect difisoled carl3on'at4 species by 6.4.1. vacuateitheq4iter flask Care- precipit'ationY,as innfcaibonate using the fully 'until bubbles fogrn in the slurry. Con: ' precipitation apParatus shoWn in figure t. tinug evacuation for 2 min. 6.3.1 Attach.a -2-liter Mason jar to the 6.4.1.3 Carefully run the plidsphorite bottom otthe precipitation one.Run'a hose acid from the separatoryfunnel into the 4- fiOm the 15-gal di-lin-I...containing the sample liter flask. Carbon dioxitie is.releacqd from to the precipitatdreall the top plate/All the..slurry.AlloW the pressure to 'build. up si%44ep out the 'u4it with nillrbi,Aen gai to,r toapproximately 120 mm of -Irkrcury move atniosph.e.fic carbon (gauge G-1) a;nek,then operi die stopcock to . pressurized nitrogen to the' 16-gal drVlb to, traps'.0 and D ihat pressure holds can. fOtrce the water Asample over' into t pm- stint. Trap'.B is cooled with isopropa cilpitator. ice. Itsfunctioniitocondense waterra ilk6.3,2 Proipitate bariumsidfal C And.D are cooled with liquid nitrogen;a, 4darbonath byeating the sample w' h. flit their fUnCtion is condense carbiln dioxi imther4ionheater while- stirring .and adding a Wh the evolutiond carbon 2 liters of barilichloriire* solution: If sul-r/dio)-'cYde' is-completed as show n by decrease fate in.,the wa"-rer ,sa6pleeYceeds approxi- of pressure on gauu to onstant,( mate.zop me'] (pr6viously determined in minirfi lun, carbon dtoZide cari now ,be traps-. the fiell:1 or laboratqry), strontium chloride'ferre4-t-er-th-e storage,.cyli4ers E-1, isused as pi-,ipitant. Add M, socOrim E23, and E-4. Theaquaptiti of carbon diox- hydroxide sinWly until pH of 10.4. iS.-"reached, ide is calculated from-the known volume of to convert bicarbonate to carbonate. Stir for each cylinder (ghtly. more than 6 liters) 1 hr while holding the temperature at ap- and the press on gauge G-3. Remove .the proximitely 40°C. ' liquid-nitrogen Dewar from trap 0;,. Replace-. 6.3.3, Open the bottom valve and permit the liquid-nitrogen Dewar at tratF. D with the barium sulfate-carbonate precipitate 'to an isopropanol-dry ice Dewar. Carbon di- flow into the Mason jar. Rotate stirring rod oxide flows into cylinder and when briefly by flipping control switch after 1 hr. atmospheric pressure -ireac ,cylinftr, Repeat cycle each one-half hour for next 2 E-2 is opened and fit .The remaining two hr. Major portion of precipitate should now cylinders are succively filled in the same be in the Mason jar. Close bottom valve, un- way. *iv screw' Mason jar, cap immediately, and seal, 6.4.1.5 Calculate the number of moles exposed cap edges with vinyl or rubber. tape. of carbon dioxide collected using volume of 6.4 Synthesis of benzene. The vacuum line e ch storage cylinder, gauge pressure, and for evolution of carbon dioxide and its con- ambient temperature. Determine the gr s version to benzene is shown schematically of lithiumetal to be used in the followiirg in figure 3. . carbide con ersion step by multiplying the 6.4.1 Evolution of carbon dioxide from number ofoles by 60. barium carbonate. -. , 6.4.1.Weigh out the required lith- 6.4.1.1 Decant most of the supernate ium shot, an lace in the steel reaction from the barium sulfate-barium carbonate chamber F. Evacu to the line and the cham- precipitate. Slurry the-xemaining precipitate ber, start the flow of cooling water through I and solution and transfer to ,a 4-liter heavy- the reaction chamber, and turn on the heater. walle&Pyrex flask(A).. Put, a. magnetiC 6.4.2 Reduction of .carbon dioxide_ to stirrer bar in the flask, cap with a two-hole lithium, carbide carbide. stopper containing a separatory funnel, and 6.4.2.1 When lithium is adull-red place ori`the.,y,acutun line. The vacuum line heat (as obsered through the viewing port) has been previously evacuated.Fillthe admit carbon dioxide from the storage tanks seParatory funnel with 125 ml of 85 percent into the reaction chamber F. Pressure drops phosphoric' acid.. sharply as the reaction proceeds (G-4). Con

. ) ) METHODS FOR DEVERMINAION 01'''RADIOACTIVE.SUBSTANOES 21 tinue heating until pressure *drops to min- gen Dewar wi opropan9I-dry ice. Com- imum. Continue heating for 1 hr. Turn off pletereactio ndicated by 'constant heat and allow to cool. , minimum pressure cm gauge Gw' 6: Complete 6.4.2.2 The lithium carbide ,contain- reaction requires 2-3 hr. A second tube of mg carbon-14 is treated with water to form catalyst may be required to achieve complete acetylene. Unreacted lithiumreacts with reaction. I . water to produce_hydrogen. Carefulty intro- 6.5 Preparation for counting. ' duce Water ftorthe dietilled-water reset= 6.5.1 Transfer the catalyst tube contain- voir. The pressure rifts because of produc- ing benzene to a vacuum-distillation appa- tion of acetylene and hydrogen. The ace- ratus. ImmOrse the receiving tube in iso- prldne condenses in traps I and K which 'are propinol-dry ice,, and after, the system is cooled with liquid nitrogen. Acetyleneis evacuated, heat the catalyst tube. When con- yurifiedbeforecdndensation by passage densation bf benzene in the receiving tube through traps G, H, and I. Traps G and H are is complete, remove and 'weigh to determine cooled with isopropanol-dry ice and trap 1 benzene recovery. f contains ascarite and phosphorous pentoxide. 6.5.2 Transfer 3.0 ml benzene tosa scin- One to 1.5 liter of water is required for com- tillation-counting container, add 1.0 ml scin- plete reaction. When the pressure nears at= tillator, and count sunder optimum' conditions ..mospherie, open the-,thamber to the vacuum for -carbon-14. Count each sample several pump- to removehydrogen as fast as it istimes to accumulate at least 400 min of produced.. Continue pumping .aft4r comple- counting timeoneachsample.Reject tion ot, the reaction. (hubbling ceases) until early' counting run results if instability is pressure falls to full vacuum. displayed. 6.4.3 `Formition of benzene from acety- lene' 7. Calculations .6.4.3.1 The ,reaction tube L contains Calculate the aPparer4ge of the sample approximately-150 g of catalyst. Remove the from the following equation": liquid nitrogen. Dewars from traps .J and a, T= 3.32.1'(log A log 43, and replace with isopropanol-dry ice coolant around. K only. Place aliquidnitrogen. where Dewar around the. cold finger M. Acetylene T = apparent age of sample in years, T= half lif e in,years now sublimes from J and K and condenses IA of carbon-14 in M., (5,168 Yi), 6.4.3.2 Conversion- of acetylene into A, -0.950 times activity" (in net counts bertzene via the alumintim oxide catalyst per minute per'gram of carbon) average's about 97 percent with a good batch of NBS oxalic acid contemporary of-catalyst. Occasionally an inferior batch is standard. This value is an aver-. encountered, and conversion is much lower. age Of several measurements on There is no, way to pi-edict whether a new contemporary standards, and shipment of catalyst will give high or low. A Vactivity of ,,sample (in'net counts conversion. The percentage,of conversion for per minute per gram of.carbon). an individual run is determined by diverting the acetylene into storage cylinder N before' 8. Report it is frozen intq cold finger. M. The pressure Report apparent age of dissolved carbon- reading sho"W7 on gauge G-6 and the known 14 in sample to nearest 50 yr for ages <1,000 volume of N enables calculation of the moles and to nearest 100 yr for ages >1,000. t of .acetylene. 6.4.3.3 When acetylene is completely 9. Precision condensed in M transfer it to, the catalytic Precision as calculated from the counting reaction rube by replacing the liquicl nitro- variance's for the sa:mple, bacicground, and * 22 TECHNIQUES OF WATER-RESOURCES INVESTIGATIONS theJandardcounts give an optimistic esti- References mation since possible errors involved in the Noakes, J. E., S., and Akers, L., 1967, Recent precipitation of the carbon and its conversion improvements in benzene chemistry for radio- to benzene- are not included. According to , carbon dating, Geochim. Cosmochim. A'cta 31, Stuiver (1972), the precision of a carbon-14 (6) p. 1094-1096. date should be ± 100 yrin the 10:000-yi range Stuiver, M., 1972, in Encyclopedia of geochemistry and environmental sciences, edited by Fairbridge, and ± 800 yr in the 30,000-yr range? Van Nostrand Reinhold Co., p. 131.

!.

4

a Jr/

I Cesium-137 and ce,ium-134, dissolve4 Inorganic ion-exchange method- -gamma counting, (R-111.0-76)

Parameters and codes: Cesium-137, dissolved(pCi /I): none assigned Cesium-134, dissolved(pCi /I): 28410

1\ Application ma detector and an automatic sample chang- The combination of a reasonably specific er and single channel gamma spectrometer. ion- exchange sepaiation of cesium isotopes The signal to noise ratio is optimized by with the eneigy discriminationavailable adjusting the spectrometer window to the through gamma spectrometry provides a cesium-137 or cesium-134 energy peaks very specific method with potentially wide Blanks consisting of test tubes w x- applicability. Boni (1966) applied the related changer are counted with the compator .KCFC technique toy thf...._determination of standards and samples for a minimum of cesium-137 inmilk, \-drine, seawater and three' 50-min counts. The cesium concentra- freshwater. Petrow and Levine (1967) ap- tion is calculated on the basis of the net plied an ammonium hexacyanocobalt ferrate gamma counts observed in the standards and (NCFC)' method to the determination of samples. cesium-137 in precipitation. 3. inteffereatirt 2. Summary of method Rutheniumirconium-niobium, , and The method is a development of Janzer, were reportedrio be sorbed by KCFC based on the work of Petrow and Levine from neutral aqueous solutions. Sorption of (1967), who used NCFC for the concentra= interfering radionuclides was reduced to less tion of cesium. isotopes from water. Thre am- than 0.1 petcent from a 10 N HCl and 0.5 N monium compound is supeilor to the potassi- HF solution (Boni, 1966). Boni also noted C um compound (KCFC) used by Prout, Rus- that interfering radionuclides could be re- sell, and. GrOh, (1965) because of elimination moved by passing the sample through 50-100 of background fromyotassium-40. mesh Biol7Rad Celex 100 in the form The gamma-counting technique begins before collecting the cesium on the KCFC. kith collection of radiocesium from relatively Ellenburg and McCown (1968) reported large volumes of water (tip to 20 liters) by -131 and molybdepum-99 were sorbed passing the sample through a column of in- in the analysis of reactor-fuel solutions using organicion-exchanger(NCFC). Selieral a slurry technique with150 ml df,samPle and standards are prered by passing a meas- 50 mg of KCFC sorber. NCFC probably ex- ured amount of st&dardized cesium-137 so- hibits similar sorption. The degree to which lution in water through columns prepared in extraneous radionuclides collected by NCFC thessame, manner as those used for the un- may interfere during counting is a function knowns. The columns are dried and then of the energy resolution of the detector. counted using a well-type sodium iodide gam- Iodine -131 might interfere using the NaI de- _

23 24 TECHNIQUES OF WATER-RESOURCES INVESTIGATIONS 4.., tectorspecified,becausethe, cesium-137 from 0.3 t9 0.5 meq Cs/g KCFC using a cesi- photopeak at 662 keV might not be fully re- um nitrate feed solution varying from 0.001 solved from the iodine-131 photheak at 636 to 0.008 M. They calculated a theoretical ex- lseV. Using a Ge (Li) deteoaor, there would change capacity of about 6 meq/g for KCFC. be no interference because resolution would 5.2 Cesium-137 and cesium-134 standard be complete. The combination of decay to solutions: Obtain from the National Bureau eliminate, -99 (T,, =67 h) and of Standards or other commercial suppliers. other,short-lived nuclides and high-resolution Dilute to approximately 100 pCi /ml for use. gamma spectrometry would appear to permit specific determination of cesium isotopes. 6. Procedure 6.1 Using the slotted16 x 150-mm test. 4. Apparatus tubes, prepare exchange columns by placing 4.1Gamma spectrometer, single-channel small plug of glass wool in bottom of tube, type. add 30-60 mesh NCFC to a depth of 1 cm, 4.2Glass and plastic tubing. and position a porous polypropylene disk on 4.3'Glass wool. top of the NCFC to keep it in place. Do not 4.4Porous polypropylenedisks:Cut. compress the NCFC granules, or excessive ' from 1.5 mm thick, 120 micrometer porous flow reduction will result from the slight hydrophilic polypropylene sheeting (Bel Art swelling which occurs when the sorber is F-1256 or equal). wetted. Prepare columns as uniformly as 4.5Sample changer, automatic for 16 possible to obtain reproducible counting ge- x 150-mm test tubes, coupled to a printout ometry in the well-type detector. system. .2 Using5-mm glass and plastic tubing, 4.6 4 Slotted 16x150-mm test tubes: A 2- pre are a series of siphons which will pro- to 3-mm vertical slot, 1-mit wide, is cut into vide a 1- to 1.5-meter head. Firmly insert the the bottom of the test tube. Fire-polishing lower end of the siphon into the numbered the tubes after cutting reduces breakage. test tube exchanger using a size 0, ,one-hole rubber stopper, and.place the upper end of the- 5. Reagents siphon in the water sample. Maximumsam- 5.1Ammonium hexacyanocobalt ferrate, ple volume normally used is 20 litets. (NCFC) 30-60 mesh prepared 'after the 6.3 Apply suction to the slat of the test manner described by Petrow and Levine tube to start flow. Flow rates of 1-5 ml/min . are normal. More rapid flow rates can be.ob- (1967). F Add 10 ml of 0.5 M sodium ferrocyanide tained by using coarser NCFC or increasing solution dropwise (approximately aa5 .ml/ the siphon. head, bUticantact time would be Min) to 240 ml of -0.3 M cobalt niate -1.0 reduced. accordingly. Some color may be M ammonium nitrate solution while stirring leached out of the NCFC during the first few on a magnetic mixer. Centrifuge slurry in milliliters of flow, but this apparently has ho 250-ml centrifuge tubes, deca9t, and discard effect on the cesium collection. the supernate. 6.4 When allthe solution has passed Wash slurry with water several times to through the column, disconnect the 'siphon, remove excess unreacted salts. Dry slurry in wipe the tubes dry, and place in an 80°C oven' tubes. heating overnight in 80°C oven. to dry. Crush dried silt and sieve to collect 30-60 6.5 Prepare several comparator standards mesh fraction. Retain finesfor incorporation by passing a measured amount of cesium-137 with next batch 9f slurry prepared. standardized solution (20-100 pCi) through The measured cation exchange capacity additional exchanger tubes. for 30-60 mesh KCFC was reported by 6.6 Adjust the gamma spectrometer to Prout, Russell, and Groh- (1965) to range obtain optimum counting in the cesium-137 METHODS FOR DETERMINATIONOF RADIOACTIVE SUBSTANCES 25 energy region (662 keV) or the cesium-134 is set equal to Ea or E b., Decay correctiot for energy region (605 keV, 796 keV). cesium-137 is, usually not required. 6.7 Count reagent blanks, standards, /111c1 1000e pCi/1 un Samples for a minimum of three 50-rnin KVE,(e-a.') counting periods each. 1000e . pCi/1 ofcesium -134= 7. ,Calculations KVEb 02'0 7.1 Efficiency factors for cesiurn_137 (Ea) 8. Report and cesium-134 (Eb) are calculated by the f011owing ,suations. The efficiency factor ilk, Report concentrations to one significant eludes counting efficiency and chet$11 concentrations between 0 and 10 covery. Use of standard equation 2 a correc a %two significant figures for high- for cesium-137 decay is not often required. er concentrations. Ea- Cry, 9. Precision d(e-Y^) of the method is estimated to be approximatelyrrroecxiimsia°rtleloy4.-20 percent. E %-e6 b d where References average countrateof standard Boni, A. L., 1966, Rapid ion - exchange analysis of (cpm) corrected for baeltgrounq radioctaithn in milk, urine, sea -water and en- and blank, -vrirnnillental samples: 'Anal. Chemistry, v.38, d--- disintegrationrateofstandard no. 1, P. 89-92. Elleohurg, and McCown,. J. J., 1968, Rapid .' (dpm), carrier-fi.t.e method for the radiochemical deter- Ad= decay constant of cesiw-131 mination of cesium-137: Anal. Letters, v. 1, no. (0.02295 yr ) , 11, P. 697-706. an = decay constant of cesium-134 Petrov', H. G., and Levine,11.,1967, Ammonium bex"Yanncobalt ferrate as an improved inor- (0.0280 months-'), and ganic exchange material for determination of ty,= elapsk time between certification of cesium-137: Anal Chemistry, v.39, no. 3,p. the standard and the count, in same units as the respective X. Prou3t6,°46W-.t,tussell, E. R., and Groh, H. J., 1965, Ion exchange absorption of Cesium by pOtas- 7.2 'Calculatikn of cesium-137 and cesium; 0sfinmir obalt (II) ferrate(II) :Jodi. 134 Concentrations Use equation 1 where EF N. 27, 'p. 79, Radiocesium, dissved, as cesium43-7 Inorganic ion-exchange ethodbeta counting FR -11176)

Parameter and code: Radiocesium, di solved,as cesium-137(pCi none assignd

1. Application The method determines total dissolved Application is possible when identification radiocesium concentration because individual isotopes are not identified by this beta count- of individual.cesium isotopes is not required and when interfering beta-emitting isotopes ing. areinlowconcentration.Concentratioh limits for interfering isotopes have not been 3. Interferences fully evaluated but would appear to be lower No interferences have been found. than for the gamma-spectrometry technique for .cesium-137 and cesium-134, dissolved 4. Apparatus (inorganicion-exchange methodgamma 4.1 Low-backgroundcounter; ananti- counting, R-1110-76). Until interferences coincidence-type counter with 2-in. thin win- are quantitatively evaluated, examination of dow flowing gas proportional detector pref- each sample for possible interference is ad- erably capable of measuring both alpha and vised. Applications to samples where radio-, beta activity simultaneously. (The Beckman cesium is the principal source of radioactiv- Wide Beta or Low Beta counters or equiva- ity would appear to be safe. lent, with pulse height discriminating cir-

cuitry, are satisfactory.) 1. 2.Summary of method 4.2 Filter, nitrocellulose membrane filters, the beta-counting technique (Janzer, 0.45-micrometer pore size, 47-mm diameter. 1973) thd same ion-exchanger (NCFC) is A suitable filter holder assembly to facilitate used to collect the cesium-137 and cesium- vacuum filtration using the 47-mm filters is 134 isotopes as in the gamma technique, required. The perforated backup plate under but a simpler batch operation is made pos- the filter disk must be plastic rather than sible by the smaller volume or water used. glass because of the hydrofluoric acid solu- One hundred milligrams of the ion - exchanger tion used. Millipore Sterifil XX-047-10 or are stirred with the buffered water sample equivalent is satisfactory. and then' separated by filtration through a 4.3 ,Teflail , polyethylene, polypropylene, or paper or membrane filter. This forms auni: other acid resistant beakers, 600-m1 volume. form low-density disk deposit that is opti- mum for beta counting. Standards are pre- 5. Reagents pared using the same technique. The sample 5.1 Ammonium hexacyanocobalt ferrate and standard disks are counted in a low- (NCFC) : Prepare as described by Petrow badkground beta counter with anticoinci- and Levine (1967), and sieve to collect the dence shielding. 30-60 mesh fraction. 0

27 28 . TECHNIQUES 'OF WATER-RESOURCES INVESTIGATIONS 5.2 Cedium-137 atandard aolution. Obtaik If different sample sizes are used, corres- from NBSor use commercial standards, ap-. ponding standards should be prepared. Proximately 100 itI/ml. 6.7 Pr: fare blanks by running the deter- minationI 511 ml of distilled water. 6' Procedure 6.8 Co a blanks and standards in the 6>r Place a 500-m1 water sample in a plas- same way as t e samples. tic beaker. 7. Calculation) with 6.2 Acidify concentratedhydro- 7.1 The cesium-137 efficiency factor (E) chloric acid to. 1 N and with hydrofluoric includes chemical recovery and cqunting- acid to 0.5 N. For a 500-ml sample, this re- efficiency corrections and is determined by quires 45 ml of concentrated hydrochloric equation 2' simplified by. treating standards and 10ml of concentrated hydrofluoric acid. and rsamples the same so that do factor f is Add 100 mg ( ±1 mg) of 30-60 mesh calculated. The following equation is then NCFC, and stir for 10 Min. After allowing the NCFC to settle, decant the supernatant used: solutionand filter it through a 0.45-microm- E etermembrane filter (47-mm diameter) in (e-m-). a vacuum-filtrati9n assembly. With the last 7.2 Calculation of cesium-137 concentra- portion of liquid retaining in the beaker, tion: Use general equation 1 simplified by transfer the NCFC o the filter taking care eliminating the f term. Decay correction is to obtainevendistribution. Return thefil- seldom required. trate to the plastic beaker. Filter through 1000e pCi/1 of cesium-137- the original filter disk a second time, and EVE (e-a0) quantitatively transfer any remaining NCFC to thefilter disk with "all amounts of dis- 8. Report tilledwater. Rinse down the funnel 'sides, Report cesium-137 activity to one signifi- and, carefully wash the filter and retained cant figure ,below 10 pCi/1 and to two signifi- NCFC several times so that the filter pad is cant figures above 10 pCi/1. The minimum not disturbed and a-uniform deposit is main- concentration reported, is that which repre- tained. sents two standard deviations above back- 6.4 Mount the filter disk in a ring holder, ground. This is approximately I, pCi/1 with a and dry under an infrared lamp. Govei>the'500-m1 simple and a Beckman Low Beta drY material with a small sheet of 4astic counter or equivalent. wrap (kitchen-type) . 9. Precision 6.5 Count inthe anticoincidence beta counter. Three 50-min counts for each sample On the basis of limited data the analysis are usually adequate. appears to be reproducible to ±10 percent at concentrations above 10 pCi/1 with inferior 6.6 Prepare standards in triplicate: Add reprOducibility4t lower concentrations. rn1 of 100 pCi /ml standard cesium-137 solutionto 500 mlof distilled water, and ear- Reference n' out the analytical procedure exactly' as Janzer, V. J., 1973, A rapid method for the de- with a- sample. The standards prepared in termination of radioactive cesium isotopes in ,this wayare also coveredwith plastic film water: U.S. Geol. Survey Jour. Research, v. 1, andmay be retainedfOr semipermanent use. p. 113-115. Gross alpha and beta radioactivity, dissolved and suspended Residue method(R-1120-76)

Parameters, and codes: Gross alpha, dissolved as U natural (AO): 80030 Gross alpha, suspended, as U natural(Ag/1): 80040 Gross alpha, suspended, specific activity as U natural(Ag/g): 01510 Gross.beta, dissolved, as cmium-137 (pCi /I): 03515 Gross beta, dissolved, as strontiUm-90/-90(pCi/1): 80050 Gross beta, suspended, as cesium-137 (pCi/1): 03516 Gross beta, suspended, as strontium-90/yttrium-90(pCi/1): 80060 Grosi beta, Impended, specific activity as cesium4 37 (pCi/g): 03518

1. Application and strontium-90/yttrium-90 and cesium-137 The method is applicable to any natural- calibration standards, and results are re- water sample. Because of restrictions on the ported relative to these reference isotopes. Thus, the measured sample activity is re- weight of.residue which can be accommo- dated, the sensitivity falls off with increasing ported ,in terms of the amount of natural concentrations of dissolved solids. uranium and equilibrium strontium-90/yttri- , um-90 and cesium-137 activity which would 2. Summary of method give the same alpha and beta count rates 'respectively for the same weight of residue. The method is an gxtension of the proce- The gross activities are reported in terms of dure published by Barker and Robinson equivalent quantities of reference standards (1963) for gross beta radioactivity. of the true alpha and beta activities of .the A representative aliquot, but not more sample. than 1 liter of the', sample including sus- pended solids, is filtered through a tared The accuracy of these approximations Be- 0.45-micrometer membrane filter. Tlr filter nds on'a number of variables related to the and retained solids are dried at room tem- energy distributions of the alphaandp beta perature and then at 105°C, cooled, and re- particles and the similarity, of the residue, weighed to determine the weight of nonfiltra- used in preparation of the-calibration curve% ble residue per liter. to the actual sample residUe. The method, A filtered volume of the sample conta,ining must be regarded as a rapid, semiquantita- no more than 150 mg of dissolved ,solids is tive measure of gross sample activity. evaporated to dryness in a Teflon evaporat- ing dish. The residue is transferred to 9, 3. Interferences 'tared,2-in.concentric-ring,stainless-steel fi planchet, dried in a desiccator, weighed, and Withiits intended purpose, the method is counted on a low-background alpha-beta free of interferences, although the accuracy counter.'The observed radioactivity is com- varies considerably with the nature of the pared with the activity of. natural uranium alpha and beta emitters, chemical composi-

29 30 TECHNIQUES OF WATER-RESOURCES INVESTIGATIONS tion of the sample, and uniformity of plan- 5.6 anium standard solution, 1.00 ml chet preparation. =100 /1g U :Dissolve 0.1773 g of UO2' I ( C,H, _)22H,0 in approximately 500 ml 4. Apparatus distilledwater. Add 15 concentrated 4.1 Evapoing dishes, Teflon, 100 ml. HNO,,' and dilute to 1,000 ml in a volunietric flask. Store in a TeflOn bottle. 4.2 Hotpe or steam table. , 4.3 Infrared drying lamps. 6. Procedure 4.4 Low-background counting equipment. 6.1 Preparation of beta calibration; c rve. Proportional counters capable of measuring, 6.1.1 Add the following amounts of cali- both alpha and beta activity are desirable flon (forexample, Beckman Instrument 'CO. \bration solutions A and B to 100-m1 evaporating dishes : Wide-Beta or Low-Beta II, or equivalent). Approx. Dish A residue 4.5 Membrane filters, 47-mm ?diameter; No. (ml) (ml) wt. 0.45-micrometer pore size, cellulose nitrate (1,17) 1 25 10 or acetate type. c---- 2 5 20 4.6 Planle(s, stainless steelia-in. diame- 80 30 ter, concentric-ring type: 10 40 4.7 Smpecific conductance meter. 5 140 50 4.8 Vacuum desiccator. 6 20 60 4.9 Vacuum-filfration apparatus, for 47- 7 200 70 , - 8 25 80 mm membrane filters. 9 250 90 10 30 100 5. Rapgents 11 300 110 12 25 120 5.1 Calibratick solution A: Dissolve 0.281 13 350 130 g MgS0,7H2O, 0:070 g NaC1,0.026 g 14 40 140 CaS0,21120, 0.109 g NaHCO,,, and -0245 15 400 150 g CaCO, in distilled water, bubblingCO, gas To each dish and to four additional 100-m1 through the solution if necessary to obtain Teflon evaporating dishes (Nos. 16, 17, 18, clear solution. Dilute to 2.00 liters. and 19) add 1.00 ml of strontium-90/yttri- um-90 standard solution. To dishes 18 and 19 5.2 Calibration solution B: Dissolve 1.350 also add 5 drops concentrated N1140H. g MgS0,7H2O, 3.510 g NaC1,1.550 g 6.1.2 Evaporall the solutions to dry- CaS0,21-120, 0508 g Mgd126H2-0, and 0.300 ne,ss on a low-tempprituri. hotplate. 1)rhen g CaCO3 indistilled water, using Cp, bub- Dilute to 2.00 disheS 18 and 19 are dry, raise heat to ap- bling as necessary t proximately 350°C to volatilize NI-14a. liters. 6.1.3 Perfoim sees 6.6 through 6.11 of Note: CompositiOn of the calibrate n_solu- the procedure' which follows. . tions should approximate that of the sa les 6.1.4 Plot the beta efficie,ky, (net colinti. -to be anatyzed._ Solutions A and B were se-\ per Minute per picocurie) againgt the ridue APlected to approximate the composition aver- weight to obin the beta calibration cue. States.' - age of 12 major rivers in the United 6.1.5 Pr re a beta calibration curve 5.3 Cesium-137 standardsolution; ap- for cesium-1 following steps 6.1.1 through proximately 500 pCi /ml and acidified to 6.14. Use .00 ml of cesium7137 'standard. approximately 1 N with hydrochloric acid. 6.2 Preparaioca of alpha calibration curve: 5.4 Hydrofluoric acid, 49. percent. The alpha calibration curve is obtained in 5.5 Stron'tiuM-90/yttrium-90 standard so- exactly the same manner as the beta curve lution, approximately 500 pCi/m1 combined (step 6.1) except that 100 µg of uranium (1 activity and acidified to approximately 1 N ml of uranium standard solution) is substi- with hydrochloric acid. tuted for the strontium-90/yttrium-90 beta METHODS FOR DETERMINATIONarit:CDIOACTIVESUBSTANCES 31 I 1IP standard.. It is important that the uranium solids for the equivalentstrontiuTh1)/yttri- standard be in secular equilibrium with re- urn-§0 or cesium-137 may also be calcUlated. specCto uranium-234. The uranium isotopes 6.6 Gross radioactivity of the dissolved ratio may be detertifined 'by, the ,method de= solids is determined as follovh: Using a tared scribed elsewhere in this manual. . Teflon dish, evaporate the required volume of 6.3 Sample analysis : Measure the specific water to dryness on ahotplate ompteam bath. conductance of each water Ample. Multiply Remove Teflon dishes from/a-13We as soon the specific conductance in onhos/cm at 25'C as they ,reach dryness to prevent warpingof by 0.65 to obtain an approxiate value for dishes due to excess heat. the dissolved- solids concentra on of the sam- 6.7 Detertnine approximate weightof ple in mg/1. Deterniine, the lume of sample residue by weighi g dish plus residufi and which will contain approximately 100 mg of subtracting tare t.If the wght of dissolved solids : residue falls outside the 0- to 130-Trig range, 100 mg start a new evaporation wan); a larger or Sample volume, V(1) mg4 smaller sample volume as required. The actual 'sample residue should weigh 6.8 Quantitatively transfer the residues between 50 and 130 mg. in the evaporating dishes to tared planchets 6.4 Gross radioactivity of the sus end using rubber policemen anda,, minimum solids is determined as follows : Vigorou amount of distilled water to effect the trans- agitate the sampld bottle containing the, to fers. Confine the solution and residue to the amount of sample collected and quickly 'pa three inner concentric rings of the planchet off 1 liter of sample with suspended solids ing the transfer. into a graduated cylinder. Allow sediment to 6.6 Dry the planchets under infrared heat . settle and then, using- suction, ,filter through lamps: Police down the evaporating dishes a tared membrane filter. When'only 100 ml of with small addit* amounts of distille4_ sample remains to be filtered, swirl tb sus- water and transf lanchets. pend solids and add suspension to filter funi" 6.10 Repeat p 6.6. Ifa residue-remains ,nel. Any remaining traces of sediment may in the evaporating (Hill. after three washes be -transferred using small amounts of dis- with 'distilled water, add a saall amount of tilled water. hydrofluoric acid, and use for a final policing. 6.5 Carefully, rinse solids with a small 6.11 Disperse the final liquid slurry in the amount of distilled Water, and maintain as planchets as uniformly as possible, using a uniform a, deposit as possible. Remove filter, stirring rod to disrupt large aggregates.

allow to air-dry, and weigh. If the weight of Again evaporate to dryness. . solids is irk excess of 150 mg, refilter a fresh .12 Place the planchets in a vacuum aliquot of appropriath volUme .to obtain less,. cator and_evaxuate to complete the, 47- than 150 mg; weigh, dry a,t 105°C, and count ng ; eigli the planchets and determine the for alpha anti beta radioactivity. eight of residue. Although not totally comparable, the same 6.13 Count the planchets in a low-back- absorption .or taunting efficiency factors for ground alpha-beta counter. Obtain three 50- the respective counting instruments are used min counts on each sample. as for dissolved solids, and the calculations are made in the same way. The weight of sus- 7. Calculations pended solids per liter of sample is also re- . ported (USGS .parameter code 00530) and Determine t e equivalent concentration of may be used to calculate km radioactivity as- alpha and beta emitters in each planchet > sociathd with the total weight of suspended from the net measured activity and the ap- solids per liter of original sample. Specific propriate factor from a table of calibration activity-of the solids in pCi/g of suspended curves. 32 TECHNIQUES OF WATER - RESOURCES INVESTIGATIONS Scpma 1000 8. Report Fa Pg1 .Ets U natural, Report values of less than 1 pCi/1 to one xFp.1000- sig-nificanfigure. Report ¶iigher values to \jGross V. two signifint figures. pCi/1 as Sr"/Y" or as CS137 where 9. Precision Scpma = alpha count rate of sample in Results for a particular sample are usually counts per minute, reproducible to about ± 20 percent at the 95- Scpmp = beta count rate of sample in percent confidence level, counts per minute, Fa= alpha factor in cpm/pg of natu- ral U, Reference F =beta factor in picocuries per Barker, F. B., and Robinson, B. P., 1963, Determina- count per minute, and tion of beta activity in water: U.S. Geol, Survey Va = aliquot used in milliliters Water-Supply Paper 1696A, .32 p.

fr

) r.

t Lead-210, dissolved , - ical'separation and precipitationmethod (R-1130-76)

Paateter and code: Lead-210,dissolved(pCi /I): none"Ossigned inter- /1.Application and other natural radionuclides do not fere. Lead-212 does not interfere because.of The method may be used with all natural the short half -life (10.6 hr).Stable lead in waters where detection oflead-21'0 With sen- the water sample should cause 'no interfer- Whiire im- sitivity to $,pCi/1 is acceptable. ence by increased betaabsorption since lead proved sensitivity is required, a .larger sam- concentrations seldom exceed a few tenths, of ple than the normal 500' ml is concentrated a milligram per liter.Aisoblem might be en- by evaPoration before begihningthe pro- countered with industrial wastes where lead cedure. Rama and Goldberg (1961 reported concentrations could be much higher. they were aTe to achieve tensitity to0.02 The application of the method to liquid pCi/1 by use of a 20-liter sample and direct waste should be checked by "spiking" sam- precipitation of lead chromate from this ples with , knownlead-2t0 and determining large -volume. percentage of recovery. Lea# recovery may be low in waters con- taining\high concentrations of organic ma- 4. Apparatus terial that can possibly complex lead. 4.1 Centrifuge, capable of handling 50-ml 2. Summary of method tubes. 4.2 Centrifuge tubes, poropylene, ap- The analytical method is designed to iso- proximately 50-m1 capacity. ' late lead-210 in a relatively pure lead chro- 4.3 disks, 49-mm diameter, Mini- allowed to age to mate precipitate. This i mum thiclthess 0.1mm. produce bismuth-210, a beemitter with 5-d 4.4 Ion-exchange columns, 1-cm insidedi- half-life. Lead-210 is not coted directly be- ameter, 10-cm, Jong with 50-MIreiervoir, at iations of 15 cause of its very softibeta, top and-61 keV, which are-greatlytenuated 4.5 Low-background counter, an anticoin- absOrption.. The bisinuth isotope decays by cidence-type counter With 2-in. thin window beta emission with a beta- maximum energy flowing gas proportional detector preferably of 1.16 MeV, and these beta particles are capable of measuring ,bnthalpha and beta easily counted. activity simultaneously. N 4.6 Magnetic stirrer-hotplate. 3. Interferences 4.7 Metrane filters, 47-mm diameter, Henry and Lovegidile (1961) have shown 0.45-micro eter pore size. Must berinert--W that essentially complete , separation from warm, dilute chromic acid. radioisotopes of , cesium, cobalt, Planchets,stainless steel, 5-cm -= iodine, phosphorous, ruthenium, strontium, diameter. , zinc, and is achieved. 4.9 Tape, cellulose, 5-cm wide roll, adhe- \Radium, thorium, uranium, -40, sive on both sides.

SS 34. TECITIQUES OF WATER-RESOURCES INVESTIGATIONS 4.10 Tape,"Magic Tape"(Minnesota 6.1.2 Plug the end of the column with a Mining and Manufacturing Co.), 8 mg/cm= small piece of glass wool, and wash with8 N density, 5-cm width. HC1. , 4.11 Vacuum-ftltratioli apparatus, for 47- 6.1.3 Transfer the .resinslurry mm membrane filters. to the column, allow to drain and :'5.Reagents , settle. 5.1 Acetic acid, 25 percent_ by volume : Di- 6.1.4 Place asmall glass-wool plug at lute 1 volunie glacial acetic acid With 3 vol- the top- of the resin column. Avoidpacking umes distilled water. the resin. Wash with 10 column-volumes each _ 5.2 Ammonium persulfate. of 8 N HC1; distilled water, and finally 2N 5.3 Hydrochloric acid, 8 N and 2 N. HC1. The column is now ready for use. The 5.4 Ion-exchange resin, Bio-Rad Agl-X8, resin is discarded after one use. or equivalent, 50-100 mesh. 6.2 Preparationoflead-210standard 5.5 Lead carrier solution, 1-m1=4.00 mg oplanchets:Threeor more "permanent" Pb+2: Dissolve 6.394 ganhydrOus Pb (NO,) 2 standards are prepared by precipitating a in 100 ml of 1 N HNO, and dilute to 1,000 ml known amount of lead-210 as leaddi/Ornate. it with distilled water. 6.2'.1 Add 5 ml" of tead carrier solution 5.6 Lead -210 standard solution.. Suitable and an accurately known amount of lead-2 0 standards are available, from ArnlViam/. (approximately 200 pCi is convenient) 50 SearleCorp., , rlington Heights, .Solu- ml of4.001 M nitric acid. Heat to 95°C,pw- tionsust be kept strongly acidic (about 1 N ly add 5 mLof,4 percent potassium dichro- inIIN ,) when dilutions are made. mate" solution, stir for several minutes, and 5.7 Nitric acid,. 0.01, M': Dilute 0.1 ml of digest on a rate for 20 min with occasion- concentrated HNO, to 120 ml. al agitation.'r 5.8 Nitric acid, 0.001 M: Dilute 20 ml of 6.2.2 Cool to room temperature, filter p.01 M HNO, to 200 ml. through a tared 0.45-micrometer membrane 5.9 Potassium dichromate solution, 4 per- filter, and wash the >precipitate with a small cent : Dissolve 40-g reagent-grade K,Cr,,O; in amount of distilled water containing a ew distilled water and dilute to 1 liter. drops of.aerosol OT solution. 5.10 Sodium acetate solution, 10 percent: 6.2.3 Allow the membrane and precipi- Dissolve 100 g anhydrous NaC,H ;0, in dis- tate to air-dry, then weigh and calculate the tilled water and dilute to 1,000 ml. chemical yields. Mount the standards as de- 5.11 Sodium carbonate solution, 1.25 M: Scribed in step 6.16. . Dissolve 265 g of anhydrous Na2CO, in dis- 6.2.4) Allow the standarlto age until tilled water and di1C.rte to.2,NOml. the count( rate-becomes. constant. This will re-. N 5.12. Sot tum sulfate, anhydrous: quire 40 ,d. (8 half -lives of bismuth-210)-ot :y less, because' T5 to 100 percent of the bis- 5.13 Strontium carrier solution, 1 m1-760 withthelead, 145-Ng-Sr(NO,)2 in dis- muth-210coPrecipitates mg Sr+2: Dissolve chromate. tilled water; add 1 ml concentratedHN6.1 6.3 Analysis of the water samples : Meas- and dilute to 12,1I00 ml. ure a 500-ml water sample into an800-ml 5.14 Surf actant, Dade AerosolOT,-St-14- beaker, add a magnetic stirring bar and a tific Products Co. few drops of methyl orange indicator, and place on a magnetic stirrer-hotplate. 6. Procedure 6.4. While stirring, add 0.01 M nitric acid , 6.1 Preparation of ion- xchange colunins. dropWise until the indicator turns red. If 6.1.1" Slu 4.0 g of i n-exchange resin the sample, is initially acid to methyl orange, with 10 ml ofN HCl in a 50 nil_beaker. bring to color change with , then Cover- and place in an ultrasonic cleaner for back to acid side with nitric acid. Add 5 ml 1 min and allowstand for at least 20 min. of lead carrier solution, 4.5 g of anhydrous I , , ' - ,

, METHODS FOR DETERMIRATI F fiADIOACTIVE SUBSTANCES 35

sodiuni sulfate, and 1.gf ammonitirnrsul- letting the eluate in a 150-in1 b aker. Record fate. Cover with a watchjglass, and he t and the date and time of elution. This .fraction -- stir at the incipientof fng pointfor 1 hr. - contains lead-210 free of daughter activity. 6.5 Add 5* of str um carner.solution 16.13 Add 3 ml of 25 percent (v/v) :acetic o the sample and continue heating, while acid and 5 ml of 10 percent sodium acetate to stirring at :the incipient boiling point for 20 the eluate, and dilute to approximately 75 ml, min; retrieve the magnet, remove the beaker Heat to incipient:boiling and add slowly-6 ml from the hotplate, and allowe precipitate of 4 percent potassium dichromate-Solution. to settle and Solution to cool wlto room -Mix thoroughly by swirling the beaker and hold near the-boiling 'point for 20 min -with temperature. , 6.6 Decant or syphon off as much of the occasional swirling. supernatant liquid as possible without dis- 6.14/Remove thteaker from the hotplate turbing the precipitate. Wash 'the residue and filter, while wa ,through a tared 0.45 - micrometer, 47-mm-diameter membrane fil- into a 50-m1 round-bottom Teflon or polypro- pylene centrifuge tube using a small, vorume ter. Rinse with distilled water, containing a few drops of Aerosol OT solution, to prevent of distilled water. Centrifuge, and discard the the precipitate from clinging; to the filter supernate. 1- funnel. 6.7 Place a 1/4 -ins Teflon-coated magnet in 6.15 Remove the filter memhkane from the centriftigetube, add 40 ml of hot 1.25. M the filtration apparatus, place on a clean sur -' sodium- carbbnate solution, and ple the tube face,'and allow to air-dry. Weigh the filter to in a boiling-water bath on a magn tic stirrer- determine chemical recovery. hotplate. Stir vigorously for 26_min. 6.16 Place the filter in the center of a 49- 6.8 Remove the tube from the bath, and mm copper disk, the surface of which has wash down any precipitate on the upper part been covered with a strip of double-faced of the tube using a jet of -1.25 M Na,CO3. cellulose tape. Cover the filter disk with a Cgntrifuge and decant or syphon off,rnost of- strip of .5-cm "Magic Tape," trim to the size the supernate. Syphoning is preferable be- of the copper disk, and place in a 5-cm cause of the difficulty of decanting without planchet. disturbing-the precipitate with the magnetic 6.17 Afters' an aging period of7' d (on stirrer; longer), count the sdmpled in a low-back-- 6.9 Repeat steps 6.7 and 6.8 two more ground beta counter with a 5-cm detector for -times. Remove the stirring bar before the 100 min to attain sensitivity to 2 Ex,, final centrifugation. Discard the final super-, tended 'counting improves the detection. 'For natant liquid. vi example, detection to 0.7 pCi/1 is possible 6.10 Dissolve thelead-stroAumcarbon- with a 1,000-minkount. ° ate precipitate in the centrifuge tube by cau- tiously adding 15.0 nil of 2 N HC1 followed 7. Calculations by 1.0 ml of 8 N HC1. Mix thoroudily and 7-.1 Lead:-21,0 efficiency faefor () and pour the solution onto the ion- exchange col- chemical recovery factor (f) : Although bis- umn. Be sure the flow rate does not exceed 2 muth-210, daughter of lead -210, is 'actually ml/min. counted, an in-growth factor is ndt used in 6.11 Rinse the centrifuge tube with two 2- the determinagon of E. The standard is al- ml portions of 2 N HC1, adding these rinse lowed to reach equilibrium (40-d standing) solutions to the column. before counting, and the disintegration rate 6.14. Wash the column with a volume of 2 at this time is controlled by the lead-210 con- N HC1 equal to two column-volumes plus the centration: Deterniine f from the weight of holdup Volume in the column below the resin l'e,ad chroinate. E is determined'using equa- bed.,Elute with, 30 knl of distilled water, col-. tion 2. TECHNIQUES OF WATER-RESOURCES INVESTIGATIONS equation 3 with the to y of (2) c11, daughter before counting and decay during - 7.2 Calculation of lead-210 concentration : counting eliminated. Calculate lead-210 con- An in-growth factor is used in calculation of eentratimA using the equation below, and concentration in individual samples because cotrect for decay if excessive time elapsed between the sample collection and analysis. the aging time before counting (approxir-, e_x -c, mately 7 d) is'insufficient to attain equilibrf- pCof lead-210- 1000-e um. The in-growth factor for each sample is 4 VE f (e-xt) obtained from a curve of the growth of ac- where ivity with time (fig. 4) or,more accurately, -6- net count rate of sample after cor- by calculation. Chemical recovery factor` is rection for background and blank determined fiom.the ratio, of actual weight of A- decay constant of lead-210 (0.0315 lead chromate recovered to the theoretical yr-'), Weight-Tor 20-mg lead carrier, the theoreti- t= elapsed time between collection -of sal weight is 31.20 mg of lead chromate. Use. . sample and analysis, .9

4

0 5 ° 8- 2 co :37 5 E 0 .67 0 z5 0 o .4 cc LL.3

.2 1 .1

2 5 6 7 8 9 1 O.1 1 121314 TIME IN DAYS

Figure 4.Growth of bismuth-210 from pure lec1210 source. METHODS FOR DETERMINATIONOF RADIOACTIVE SUBSTANCES 37

A, - decay constantofbismuth-216 averaging 98 percent with a mean deviation (0.1384 d-1), of ±2,percent at concentrations above 15 ti- elapsed time between elutia of the pCi/l. At lower concentrations the precision ion-exchange column (step 6.0),is2 pCi/1 or ± 10 percent, whichever and counting, and larger, V, E, and f are as defined in equation 1.

8. Report , 4 Report concentrations of less thaitit;fn toyl004References pCi/1 to the nearest pC1/1; higr condefttflat Henry, W. D/14 Loveridge, B. A., 1961, Deter- tions to two significant figures. mination of lead -2.10 in Harwell effluent: Atomic 9. Precisym Energy Regearch Estab. Rept. R-37957 20 p. Tests with eight water spies to which Rains, M. K., and Goldberg, E. D., 1961, L ad -210 in known lead-210 was added gve recoveries natural waters: Science, 134 p. 98-9 Radium, dissolved, as radiUm-226 Precipitation method (R-1140-76)

Parameter and code: Radium, dissolved, as radium-226 (pCi/1): 09510

1. Application Radioactive impurities in the reagents may The method is satisfactory for applica- be significant. Reagents are selected, and Nms./ Oat do not require high precision or blanks are run wit et of samples.:\ radium isotope identification such as routine Since alpha rration is strongabsorbed monitoringforcompliancewith PCRE by the precipitate, it is essential toeep the standards. The applicationis /straightfor- weight of Precipitate constant in the sampl ward with waters of average compodition, standards,andblanks.Highsalinity but the possibility of increased alpha self- (brines), colloidal matter, and high concen- absorption must be considered with waters trations of strontium or barium may cause of high dissolved-solids or alkaline-earth con- problems by adding to the mass per unit area tent. The internal standard technique 'is used of the precipitate. Correction for increased when necessary. - absorption is made by.suse of internal stand- ard techniques. 2. Summary of method 3. Interferences Radium isotopes are concentrated froma. water sample by coprecipitation as the sul- Alpha-emitting nuclides of thorium and fate with barium sulfate. The collection of polonium may be carried down with the pre- radium is quantitative even though the solu- cipitate, but their concentrations are not bility product of radium, sulfate is not ex- sufficiently high in most natural water to con- ceeded. 'Although the coprecipitation collects stitute a problem. all radium isotopes, radium-226 is usually the predominant isotope. Results are consequent- 4. Apparatus ly reported as concentration of radium-226. 4.1 Beaker, 1,500 ml. , lead,' and polonium car- 4.2 Filter flask, 2,000 ml. ried down, partially or completely by the bari- 4.3 Membranefilter,47-mm diameter, um sulfate may also contribute to the alpha ,0.45-micrometer porosity. 'count.,The analytical procedure is taken frOrn 4.4 Filtration assembly, for membrane fil- Barker and Johnson (1964). The, precipitate is collected by filtration ter including funnel, sintered glass-filter sup- through a plastic-membrane filter, and is port and clamp. counted in a low-background thin window 4.5Ring-and-disc sample mounts, 47-mm alpha counter after a suitable delay to allOw diameter, in-growth of alpha-emitting daughters. This 4.6 Low-background counter, an anticoin- increases the sensitivity by a factor of 4 (at cidence-type counter with 2-in. thin window equilibrium). The count rate of the sample is flowing kaa proportional detector preferably compared against that of a radium-226 capable of measuring both alpha and beta standardcarried through the procedure. activity simultaneously. ,

39

4 40 TECHNIQUESOF WATER-RESOURCES INVESTIGATIONS

5. Reagents and dilute to volume 'with distilled water. 5.1 Ammonium sulfate solution (40 per- Add a small, clean disk or foil of 22-carat cent, by weight).: - Dissolve 1,600 g of am- (surface area 4 cm2) to the solution monium sulfate in a minimum volume of hot to remove polonium-210. This disk should distilled water. Coo lto room temperature and remain in the standard solution continu- filter. Dilute the solution to approximately 4 ously. liters in a 4-liter bottle. 5.7 Sulfuric acid wash solution: Dilute 5.2 Barium carrier solution(1.40 mg 5 ml of concentrated H250, to 1,000 ml with Ba+2 per ml) :Dissolve 1.246 g of barium distilled water and add 3 to 4 drops of Triton chloride dihydrate in distilled water, add 5 X-100 surfactant (Rohm and Haas Co.). ml of concentrated HCI, and dilute to 500 ml. 5.3 Hydrochloric acid, concentrated. 6. Procedure 5.4 Methyl orange indicator solution. 6.1 Measure 1,000 ml of the sample, pre- 5.5 Radium standardsolutionI,50.0 viously filtered if necessary, into a 1,500 - pCi/ml. This solution is prepared from Na- ml beaker. If the sample contains more than tional. Bureau of Standards' encapsulated 350 mg/1 of calcium, take a proportionately radium standard No. 4955 which contains smaller volume and dilute to 1,000 ml. If a 0.100 x 10-6 curie of radium -226 in 5 ml of 5 sample is believed to contain sufficient quan- percent HNO3. Rubber gloves should be worn tities of barium, strontium, or other dis- in preparing a standard solution by the fol- solved or suspended material to add more lowing recommended procedure. than 1 or 2 mg to the weight of the pre- 5.5.1 Placethevialcontainingthe cipitate, the internal standard modification radium standard inaclean,heavy-wall, should be used (sec. 6.8).. small-neck bottle or flask of 250- to 500-m1 6.2 Prepare duplicate standard solutions, capacity. Add 50 ml of 3 N HCI, and stopper each consisting of 5.00 ml of radium stand- securely with a polyethylene stopper. ard solution (1 m1=10 pCi radium-226) di- 5.5.2 Place the bottle (or flask) in a luted to 1,000 ml with distilled water, and strong plastic sack and, holding the stopper a blank solution consisting of 1,000 ml of firmly in place, shake vigorously to break distilled water. Add a few drqps of methyl orange indicator,, and adjust the pH to ap- the vial. 4 5.5.3 Decant _the solution into a 2-liter proximately 3.5 by dropwise additidn of con- volumetric flask. centrated HCI (or NH,OH followed by HCI 5.5.4 Rinse the bottle with 50 ml of if the sample has an initial pH below 3.5). 3 N HCI, and decant into the 2-liter flask. 6.3 Heat blank solution, samples, and 5.5.5 Add another,50 ml of 3 N HC1, and standard solutions to incipient boiling point, washthoroughlyusingtheultrasonic and readjust the pH to approximately 3.5. cleaner. Decant into the 2-liter flask. 6.4 Add 3 ml of the barium carrier solu- 5.5.6 Rinse with 50 ml of 3 N HC1. De- tion to each beaker and stir vigorously. Cant into the 2-liter flask. While stirring, add 15 ml of saturated am- 5.5.7 Repeat steps 5.5.4 and 5.5.5 al- monium sulfate solution. Continhe heating ternately, three more times each. near the boiling point for an additional 15 5.5.8 Dilute the solution in the 2-liter to 30 min. flask to 2,000 ml with distilled water and 6.5 AllOw the precipitate to digest at mix thoroughly. oom temperature for 4 hr or Tonger, then The final concentrations of radium and co t the precipitate on a membrane filter. hydrogen ion in this stock solution rare: Police down the beaker carefully to ensure (Ra+2) =50 pCi /ml and (H+) =0.75 lg. complete transfer of the precipitate to the 5.6 Radium standard solution II, 1 ml =10 filter. Wash the precipitate with small vol- pCi : Transfer 50 m1 of the radium standard umes of the sulfuric acid wash solution. The stock solution to a (250-ml volumetric flask barium sulfate precipitate should be evenly . / METHODS FOR pETERmirIATIONOFRADIOACTIvraSUBSTANCES 41

. distributed to minimize set-absorption Of and fir°eedure is calculatedusing the fol- alpha particles. A fine jet6fthe wash solu- lowing equation: tion can be used toredistribute the precipi- tate on the filter and toobtain uniform dis- E b= tribution. e .practi 6.6 Wien the membrane filter is where0--ao= average count rate (cpm) of the tally dry, mount itin the ring-and-disk :, sample econtaining the internal holders. ,',.'''standard, and 6.7 Determine the 'alpha activity ofthe d= known disintfgration rate (dpm) blanks, standards, and samples afterallow- of the inteimal radium standard ing the precipitates to age 15 d (or longer). added to the sample.- '-Count each planchet for 100 min. 7,3 Calculation of radiumgrosys alpha 6.8 For those samples 'suspected ofhav- normal procedure. Use equa- ing excessive'absorption loss of alpharadia- concentration, internal tion tion, repeat the analysis ming the 100066 standard procedure as follows :Prepore a 'pei/1 of tta (as radium-226) second sample as in6.1. Add .5.00 01of KVEO radium standard solution (1 m1=10pcj) 7.4 Calculationof radium-gross alpha Proceed with the analytical determinationas concentration, internal standard pr edure. before, andount. The difference between Use equation the the count ratfe of the sample containing 10/1 of Ita (as radium-226)1000i -- internal standard and the count rate of the KVEb sample is the basis for calculating the effi; ciency factor to be' used. 8. Report

7. Calculations less than 1.0 pCi/1 toRc:epoeritgueiTcentrationseant figure and concentrations 7.1 The "radiumas radium-226"effi- above 1.0 PCl/l to two significant figures. ciency factor (E.) is calculated using thefol- lowing equation 9. Precision Cn E , Reproducibilityat the two standard de- d is Approximately ±1.0 pCi/1 at where concentrations of 0.5 .PCi/1 and below. Re- c-- average countrateofstandard cpernotactibhiilgithyerdu is to approximately ± 20 per- (cpm) corrected for background oncentrations. and blank, and d ---, disintegrationrate-ofstandard Reference (dpm). Barker, 13 and Johnson, JAG., 1964, Determina- 7.2 The "radiumas radium-24"effi- tion of ratiiunA in water: ZS. Geol. Survey ciency factor (Eb), for the internal8tand- water-Supwy Paper 1696--13;29 p. 0-

Radium-226, dissolved Radon emanation method (R-1141-76) I Parameter and code: Radium-226, dissolved(pCi /I): 09511

1. Application 3. Interferences The method is applicable to any water The methodisnormallyspecificfor sample. radium-226. Radium-223 and radibm-224 produce radon-219 and radon-220, respec- Z. Summary of method tively. Neither of these interfere directly, but the 10.6 hr lead-212 from radon-220 has The method is based on the isolation of alpha-emitting daughters which could inter- radon-222produced byradium-226 and fere. A wait of.. 2 or 3 d before counting measurement of the alpha activity of the eliminates the interference. The alpha-emit- radon and 'itsshort-lived daughters. The ting daughters of radon-219 have no effect method is specific for radium -226 in contrast if sufficient waiting time is allowed for com- to the precipitation method of Barker and plete decay of the 36 min lead-211. Johnson (1964). The procedure represents an imprOvement of the emanation method of 4. App9ratus Rushing (1967)in the substitution of a 4.1 Alpha-counting apparatus, scaler and complexing agent to redissolve precipitated high voltage ,power supply, preamp and am- barium sulfate. Formerly a complex proce- plifier with discriminator. dure for resolution involving a strong acid,ir4.2, Beaker, .1,500 ml. s' ashing, and evaporation was requir Radon 4.3. Gas delivery system, for gas. is measured in a modification ofe alpha 4.4 Mixer, wiggle-plate or ultrasonic type. scintillation cell of Lucas (1957). 4.5 Radon deemanation train and bubbler Dissolved.radium in filtered water is col- (fig. 5). lected by coprecipitation with barium sul- 4.6 Radon scintillation cell and housing fate. The precipitate is centrifliged and then (fig. 6). dissolved in alkaline sodium diethylene tria- mine pentacetate solution. The solution is S. Reagents transferred to a radon bubbler, and arty 5.1 Barium carrier solution, 50 mg, bar - radon present is removed by purging with ium/ml: Dissolve 75.81 g barium chloride helium gas. Fresh' radon is then allowed to (BaC12) in distilled water and dilute to 1,000 grow in. After several days the ingrown ml. radon is purged into an alpha scintillation 5.2 Defoaming emulsion, Dow Corning cell-,short-lived daughters are allowed to Anti Foam H-10 emulsion, or equivalent: grow in, and the alpha-count rate is then Dilute to approximately 4 to 5 percent solu- determined. The radium-226 concentration tion with, distilled water before using. in the original water sample is calculated 5.3 DPTATEA solution: Dissolve 10 g from the radon determination on the basis of pellets in a beaker con- of the rate of radon production with time. taining 60 ml of distilled water, and stir in

43

4 -v TECHNIQUES OF WATER - RESOURCES INVESTIGATIONS firmly in place, shake vigorously to break A BUBBLER WITH POROUS DISK AND STIRRING BAR the vial. B DRYING TUBB. 5.4.3 Decant the solution into a 271ite C SCINTILLATION CELL D MANOMETER. 80 Cm volumetric flask. E HELIUM DELIVERY C4.4.4 Rinse the bottle with 50 ml of 3 N SYSTEM HCl and decant into the 2-liter flask. F GEARED MOTOR WITH ROTATING MAGNET 5.4.5 Add another 50 ml of 3 N }ICI-and washthoroughlyusingtheultrasopic cleaner. Decant into the 2-liter flask. 5.4.6 Rinse with 50 ml of 3 NHC1. De- cant into the 2-literflask: 5.4.7 Repeat steps 5.4.4 and 5.4.5 alter- nately, three more times each. *5.4.8 Dilute the solution in the 2-liter To VACUUM flask to 2 liters with distilled water andmix thoroughly. The final concentrations of radium and hydrogen ion in the stock solutions are: (Ra+2) =50 pCi/m1 and (H+) =0.75 mole/1. 5.5, Radium standard solution II, 1 ml = 1.000'pa: Dilute 10.00 ml radium standard solution I and 10 ml of concentrated HCI to 500 ml with distilled water. 5.6 Sulfuric acid wash solution: Add 5 ml of concentrated }1,S0, and 3-5 dropsof Tri- ton X-100 to 4 liters of distilledwater. 5.7 Sulfuric acid, concentrated. Figure5. Radon deemartation train and bubbler. 6. Procedure cold -Waterbath until dissolved. Add 20 g of 6,1 Coprecipitation of radiumwith bar- Purified diethylene triamine pentaacetic ium sulfate. , acid (DPTA),and continue stirring until 6.1.1 Add 5 ml concentrated hydro- dissolved.Add 17 ml of50-percent triethano- chloric acid to 1,000 ml of filtered water sam- lanwie, mix and dilute to 100 ml. Store in ple contained in a 1,500-m1 beaker. Teflon bottle! 6.1.2 Add 1 ml of 50 mg/ml barium 5.4 Radium standard solution I, 1 ml= carrier to the sample and stir... 50.0 PCi: This solUtionis prepared from Na- 6.1.3 Cautiously add 20 ml of concen- tional Bureau of Standards' encapsulated trated sulfuric acid to each sample with con- radiumstandard No. 4955 which contains stant stirring. .(Use of a 500-m1dispensing 0.100 k 10,3curie of radium-226 in 5 ml of flask fitted with a 50-ml delivery headfacili- 5 percent` Rubber gloves should be tates the acid addition.) Stir well afterthe worn in preparing a standard solution by acid addition. Allow barium sulfate precipi- the following recommended procedure. tate to settle overnight. 5.4.1 Placethevialcontainingthe 6.1.4 Carefully remove the supernate by radiumstandard in a clean, heavy-wall, decantation or suction, and quantitatively small bottle or flask of 250- to 500-ml transfer the balance of the supernate and caPaeity. Add 50,m1 of 3 /d HC1 and stopper precipitate to a 40-m1 centrifuge tube using securglywith a polyethylene stopper. a rubber lioliceman andsmall quantities of 5.4.2 Place the -bottle (or flask)in a dilute sulfuric acid-Triton-X-100 w h solu- durableplastic sack, and, holding the stopper tion. METHODS FOR DETERMINATION 6F RADIOACTIVE SUBSTANCES 45

A 'SeINTILLATO9CELL KMAR BELL COATEDINSIDE WITH ACTIVATED PHOSPHOR B QUARTZ WIN W CEMENTED" A TO SCINTILL.TR BELL C PHQTOMULTIPLIER LIME 7E1 D TUBE BASE WITH H VOLTAGE DIVIDER POLYURETHANE CENTERING RING AND SUPPORT F HIGH VOLTAGE ,AND SIGNAL CONNECTION G LIGHT-TIGHT METAL HOUSING H ELASTIC LIGHT TIGHT

1 FELT SURROUND

Figure 6.Radon scintillatiOn cell and housing. 6.1.5 Centrifuge as necessary, decant; 6.2 Deemanations. and discard- supernate. 6.2.1 Using a funnel with a fine tip, 6.1.6 Add approximately 10 ml of dis- transfer the cooled solution to a clean bub tilled water and 1.5 ml of DTPA reagent to r\the'eentrifuge tube several times the precipitate in the centrifuge tub. Dis- with distilled water; and add the washings perse the precipitate in each tube by idsing a ansufficient additional water to the bubbler p wiggle-plate mixen'or an ultrasonic unit. to lave appra*nately 2 cm of airspace at Place tubes in a wire rack, and immerse rack the top. Add 1drops of 4 percent silicone and tubes to a depth of approximately 1 inch defoaming emulsion to the solution in the in a boiling-water bath. bubbler to minimize frothing during purging. 6.1R Complete dissolution should occur 6:2-.2 Attach stopcock and "0" ring to within a few minutes if the barium sulfate bubbler using clamp, leaving outlet stopcock "pellet" was adequately dispersed. Occasion- on bubbler assembly in open position. Attach ally, volume of solution in the centrifuge helium line (3-5 psi) to inlet side of bubbler. tubes may decrease by 4-5 ml as a result of Slowly open stopcock on inlet untilyi, stream, prolonged heating, and the precipitate may of fine bubbles ries from the porous disk. not dissolve. Addition of distilled water to Maintain a steady flow of bubbles through bring the volume to approximately 20 ml the sample for approximately 20 min to com- maximum plus .additional redi,spersion and pletely purge all ingrown radon from the heating, will usually result in rapidNdissolu- solution. Close-inlet stopcock and allow pres- tion of even difficulty soluble precipitates. sure under porous disk to equalize- momen After the precipitate has dissolved, cool the tarily. Close outlet and record the day, hour, tubes. and minute. This is zero time for the growth 4 j 46 TECHNIQUES OF 'WATER-RESOURCES INVESTIGATIONS .e. of, radon that will be removed in thesecond ing. Count overnight '(1,060 min) for the deemanation and counted. average water sample. 6.2.3 Allow froni 2 to 20 d in-growth 6.2.g Dates, times, counts, and all other time for radon-2220,' depending ",uponthe pertinent sample information should be re- inthe original corded on data and calculation sheets. radium-226 concentratitn low sample, volume of saniple used, and so forth. 6.3 Calibration of equipment: One (,--:--_--10 cpm) and one high' (1,000 cpm) 6.2.4 The second deemanation is made count rite disk standards ate useful for rou- by setting up the bubbler as in 6.2.2 except tine instrument calibration tests' and forde- that both stopcocks- are initially closed. At- terminingphotoinultipliertubeplateau tach bubbler to drying tube with "0" ring curves. Prepare by pvcipitating each of'two and clamp. Evacuate_ purging assembly, in- 5 and 500 pCiof cluding cell, with vacuum pump for approxi- standards containin radium-226 with 50 mAof barium sulfate re- . mately 1.5 to 2 min. Close stopcbck at vacuum SPectively as previously described. Mount the . pump, turn pump off, and momentarily crack precipitate by filtering through a 47-mm.'- vacuuni;pIttnp connection. Open stopcock in 0.45-Micrometer membrane filter. Dry and helium' line above bubbler-inlet stopcock and place on the disc of a ring-and-disc assembly. -momentarily. crack "0" ring, connection to After drying, cover the precipitate on the fil- purge trapped air from line andbubbler-inlet with an alpha- -stand ter with a Mylar disk coated connection. Clamp and allow system. to sensitive phosphor. The dull phosphor-coated for approximately 2 min. If system leak side should be placed against the sample. manometer meniscus will flatten ormanom:\Cover with,the ring, press into place, and ter will begin to fall. If meniscusremains then seal the assembly with several pieces of - stable, proceed .'next step. cellophane tape to prevent it from separating. 6.2.5 CarefaullY open bubbler-outlet stop- The high count rate standard is used to de- cock until manometer begins to fall (check termine the plateaus for each photomulti- porous disAfor fine bubbles). Allbyv vacuum plier tube, and the appfopriate operating to equilibraslowly (otherwise there is ex voltage is then chosen accordingly. The low cessive risk drawing liquid sample into count rate standard is used to check instru- drying tube).ubbling will slow appreciably,ment operating conditions at low count rates in a few seconds. Slowly open outlet stoptock complete. Then continue with purging by comparable to those of typical samples. slowly opening bubbler-inlet stoPcockheck- Frequently operating characteristics of ing. porous disk carefully for rising bubbles. two or morephotomultiplier-counting sys- (Flow rate must be closely controlled again.tems are sufficiently similar to enable the use at this° point, to prevent sudden surgeof of a single high-voltage power supply. liquid into drying tube.) Allow pressure to Minor differences in the counting efficien- build up slowly, controlling manometer fall,cy of each unit can beadjusted by the use of - rate to complete purging in 15-20 min.To a focusing potentiometer oneach photomulti- prevent cell leakage during counting, close plier housing. the cell stopcock at approximately 4 mm Long-terminstrumentbackgrounds low atmospheric pressure. should be obtained for each counting system .6.2.6 Close down"purgingsembly stop- and should not generally exceed 0.005 cpm. cocks from cell to helium inlet isequence as Scintillation cell background count rates rapidly as possible. Record tie. Remove hould be determined periodically for each bubbler from as' sembly gifrekl and crack cellin combination with each' instrument. . outlet stopcock momentarily to r se helium Generally, background count rates are deter- pressure. mined using a minimum of 1,000 min." Back- 6:2.7 Place cell in light-tight counting ground count rates for a specific cell may camber. Allow to age 3 or 4 hr before count- vary considerably from oneinstrument to an-

4 METHODS FORDETERMINATION OF RAsDIOACtIVE SUBSTANCES 47 other, but should not ggnerally exceed 0.10 to 7. Calculations 0.15 cpm. 7.1 Radoncountingefficiencyfactor( After long use or after countinga high- (E). The calculation requires corrections fOr rat:Elm-content sample, background rates in radon in- growth and radon decay. The radon soinscintillation cells may become excessive in-growth and decay ciirves and their rela- (>0.15 cpm) for low-level, work. In that tion to the time intervals that appear in the event the cells must be used only for rela- equation are shown in figure 1. Substitute tively, high-1el sames. Original low back- the experimental data obtained for each ground may be red by rebuilding: cell-instrument unit (sec. 6.4) intoa modi- 6.4 Experimental determination of'count- fied form of equation 4. ing efficiency: The counting efficiency of each c scintillation cell varies between cells andbe- ( ittO tween counting instruments. Consequently, d(1 where for the most Accurate work, the countingeffi- cienIcy of ,each geintillatiori cell shouldbe de- decayconstantofradon-222 termined in each instrument in which it is (1.259x10* min), used. ti = time interval for buildupof The counting radon between the previous efficiencyfor eachcell- deemanation of the 'standard instrument unit is determined by counting (point A, fig. 1) and the pres- raddn transferred from a "standard bubbler" enp.deemanation (point B), containing a measured amount of radium-226 time interval between deema,na- standard solution. A minimum of fouror five tion standard (point B) and standards or one for each counting instru- midpoint,ofthecounting ment enables four or five cells to be cali- t3 brated siniultaneously. Waiting time for time4=t2 + , radon it -growth is also considerably reduced 2 as conlhared to that required if only one where standard is available. t2= time interval between deemana- 'Standards are prepared by pipetting 10.0 tion of the standa19, (point ml of 10- pCi /ml radium-226 standard solu- 1) and the beginning Of the count time (point C), tion direCtly into each of several bubbler = half the time interval between tubes. The tubes are fitted' with an "0" ring the beginning (point C) and stopcock assembly, and then deemanated to the end(point D) Hof the determine the zero in-growth time for radon counting time, and in the same manner as a sample. Barringany t, a d d,, are as defined in equation 2. spillage or breakage, the standards will last 7.2 Calculation of radium -226 concentra- indefinitely and can be deemanated every 4 or tion: Efficiency (E) used for an Individual 5 d to provide radon for calibration ptirposei sample is that determined for the cell and Cell-countingefficiencies. aregenerally instrument used to count the sample'. An in- about 5.3 cpm/pCi of radon-222 after in- growth factor is introduced because of in- growth of daughters for 3 hr, but this. may growth of radon with time after the first vary 'considerably' depending upon *tors deemanation. Use a modified form 'of equa- including the age of the cell, phototube condi- tion 3 when counting time is less than 3,600 tion, and moisture in ,cells. Erratic results minutes. are sometithes obtained as a result of im- pCi/1 of raditim-226 proper cell or instrument grounding, loose l000-e connections, noisy power lines, and, so forth; KVE (1 ex:ii) 48 TECHNIQUES OF WATER-RESOURCES INVESTIGATIONS where where intervalforin-growthof t2--= delay before courting, point B to radon belvien first deemanation C, figure 1, and (step 6..1) and second deemana-o me interval of count, point C to D. tion (step 6.2.5) of the sample, and r symbols are as defined in 7.1- t4- time interval between second de- and 7.2. emanation of the sample (step Radon decay and in-growth factors Are 6.2.5) and midpoint of the sample easily and Accurately calculated with an elec- tronic calculator having natural log and er counting time, = t 2 + functions. The table of "Radon fraction 2 (e-xg) remaining after radioactive decay for The other symbols are as defined in sec- specified times," for commonly used time in- tion 7.1. tervals (table 1) may also be used. ,When counting time exceeds 3,600 min- utes, use equation 3 including the term for correction for decay during the count. 8. Report pCi/1 of radium-226 Report concentrationslessthan . 0.10 1000 -Cit., pCi/1 to one significant figure andellues KVE (1- e-xiii) (e-k'.) above 0.10 pCi/1 to two significant figures:

Table 1.Radon fraction (e-")r;mainingof erradioactive decay for specified times [Radon Tv. = 3.823 d] Minutes Time Days Hours Minutes- Time 11 -0.834,18 0.992,47 0.999,87 31 0.996,10 .695,85 .985,00 .999,75 32 .996,98 3 .580,46 .977,59 .999,62 33 .995,85 4 .484,21 .970,23 .999,50 34 .995,73 5 .403,91 .962,93 .999,37 35 .995,60

6 .336,93 .955,68 .999,24 36 .995,48 7 .281,07- .948,49 .999,12 4 .995,35 8 .234,46 .941,35 .998,99 .995,23 9 .195,58 .934,27 .998,87 39 .995,10 10 .163,15 .927,24 .998,74 40 .994,98

11 .136,09 .920,26 .998,62 41 .994,85 12 .113,53 .913,33 .998,49 42 .994,73 13 .094,70 .906,46 .998,36 43 .994,60 1 .079,00 .899,64 .998,24 44 .994,48 15 .065,90 .892,87i .998,1,1 45 .994,35 .994,22 ,16 .054,97 .886,15 .997,99 46 .045,86 .879,48 ;997,86 47 .994,10 17 .993,97 18 .038,25 .812,86 .997,74 48 19 .031,91 .866,29 .997,61 49 .9)3,85 20 .026,62 .859;77 .997,48 50 .993,72 21 .022,20 .853,30 .997,36 51 .993,60 .018,52 .846,88 .997,23 52 .993,47. \22 .993,36, Z3 I. 0 1 5 , 4 5 .840,50 .997,11 53.. 24 .012,89 .834,18 .996,98 54 .993,22 25 .010,75 .996,86 66 arr .993,10 ,008,97 .996,73 56 .992,97 26 .992,85 27 .001,48 .996,61 57 28 .006,24 .996,48 58 .992,72 29 .005,21 .996,36 59 .992,60 30 .004,34 .996,23 60 .992,47 METHODS FOR DETERMINATIONOF RADIOACTIVE SUBSTANCES 49

9. Precision Lion of radium in water: U.S.Geol. Survey On the basis of limited data> the precision Water-Supply Paper 1696B, 29 p. at the 0.10 pCi/I level isestimated.at " ±20 Lucas, H. F., 1957, Improved low-level alpha scin- percent Above 0.10 pCi/I the precision is tillation counter for radon: Rev. Sci. Instr., no. estimated at ±10 percent 28, 680483. Rushing, D. E., 1967, Determination of dissolved References radium in water: Am. Water Works Assoc. Barker, F. B., and Johnson, J. 0., 1964, Determine- Jour. no. 59, 593-600.

1

4

ti ti. Radium-228, dissob . Determination by ieparatidn and counting of actinium- 228 (R-1142-76)

, Paraeter and code: Radium-228, dissolved(pCi/1):no assigned

4s 1. Application countered only in waters contaminated by The method is applicable to all natural- reactor effluent. water samples. Applications to samples con- Success of the method at low levels of taining reactor effluent or other contaminants radioactivity depends largely upon use of re- agents essentially free of radioactive con- have not been evaluated(' fr tamination. Purity of the yttrium reagent is 2.Summary of method especially importa The method is based on the chemical sepa- 4.ApAratus ration and subsequent beta counting of ac-, 4.1 Centrifuge. tinium-228,' the daughter ofradium-228. 4.2 Centrifuge tubes, 40- or 50-ml capaci- Radium-228 is notdetermined directly be-0ty, heavy-walled. cause of the difficulty of counting its weak 4.3 Drying lamp, infrared, mounted in --beta emission in the presence of Other alpha-(ringstand. emitting radium isotopes and their beta-emit- 4.4 Hotplate. ting daughters (Johnson, 1971). 4.5 Low-background counter, an antico- incidence-type counter with 2-in. thin-\Win- 3. Interferences dow flowing gas proportional detector prefer- No cheniical interferences have been de- ably capable of measuring both alpha and tected. Because of chemical similarity, radi beta activity simultaneously. ,; nuclides of the elements and the 4.6 Planchets, 50-mm. diameter, concen- rare7earth elements may accompany the 4,c- tric-ring type. tiniu,m precipitate. Significant concentrations 4.7 Stirring rods, Tefltn. of these would be expected only in areas where clear Wssion oribuclear research is 5. Reagents a carried o - 5.1 Ammonium h ?droxide, cpncentrad. Radioch mical interferences are unlikely 5.2 Amlnoftium sulfate solution, 200 / to occur in natural waters. Decontamination ml : Dissolve 200 g of ammonium sulfatePi factors for other natural radipnuclides, ap- distilled wad and dilute to lliter.' pear to be 5,000 or greater. ExliauStive tests 5.3 Ammonium sulfide solution, 2 percent: for 'artificially produced radi onuclides have Dilute 10 ml of 20-23 percent aqueous am- not been made, but little or no interference monium-sulfide solution to 100 ml. has been detected for cesium -137, strontium- 5.4 Barium carrier solution, 1 ml4F 16.00 90, and yttrium-90J Lanthanum-140 appears mg Ba+2: Dissolve 28.46 g of BaC1221-120 in to be the most Probable interference, but this distilled water, add 2 ml of concentrated ni-. and other' rare-earth nuclides would be en- tric acid, and dilute to 1,000

51

C- 52 . TECHNIQUESOF WATER-RESOURCE ESTIGATIONS 5.5 43inder solution; Dissolve .about 1 g of traie solution containing 5-15 ug of barium., "Duco" cement in 100 mnl acetone. Make up to volume with 1 N 5.6 Citric Aca, 1 M: Dissolve 210.1 g. of Activity of radium-`228in the solutionis citric t .acid monohydrate in distilled watai calculated as follows: - 4. and dilute to 1,000 ml. Radium-228 (dpm/m1)- 5.7EDTAreagent, 0.25 M EDTA con. -246W (1.- e012.059 taining 20 `mk/ml TN1a0H: Dissolve .20 g of where

NaUll In ONO, itiO usl distilled. water. Heat, W= thorium concentrationin, mg/ml, and slowly add 93 g of disodiurn ethylenedi- . and . aminetetraacetate while stirring. When dis- t= ears since thorium xide,. was solution is complete, cool, and dilute to 1,000 prepared. ml. At equilibrium 1 mg thoritim =246 radi- 5.8 Lead carrier solutOn 1 m1=15.00 mg Pb +'2: Dissol,Vr-213.97 g of Pb(NO:,), in um-228. . distilled water;. add' 2 ml of 5.15 Yttriu,m carrier solution, 1 m nig Y+": Add 22.85 g of Y203 to a250-ml nitric acid, and dilute to 1,000 ml:* Erlenmeyer flask containing 20 ml of water. . 5.9 Lead carrier solution II, 1 m1=1.50 mg Pb+ : Dilute 196 ml ,of lead carrier solu- Swirl, place on a hotplate, and heat to boil- ing. Slowly and cautiously add concentrated tion I to 1,000 ml.. Methyl Prange indicator solution. nitric acid, while stirring, until' a homogerie- 5. ous solution isobtained. (Usually about 5.- Nitric acid, concentrated. 5.12 Sodium hydroxide, 10' N: DissolVe ml of nitric acid is required. It is sometimes necessary to add more water.) Add an addi- 400 g'of NaOH pellets in distilled Water and tional 70 ml of concentrated nitric-acid and dilute to 1 liter. Store in a. polyethylene or dilute to 1 liter. 'Rote: The yttriumoxide Teflon bottle.. . 5.13 Sulfuric acid, 18 N: CautiouSly add must be as free as possible of beta activity . (uisually due to ). Yttri-, 500 ml concentrated 1-12S0° while stirring um oxide suitable for carrier preparationhas into about 400 ml distilledtw. cool, and beeji obtained from American Potashand dilute to 1,00 :5.14 RadiuM-228 standar : The repara- chemical Corp., West Chicago, Ill. is coplicated 5.16 Yttrium-strontium carrier solution, tion of thestandard solutlb and 0.9 mg Y.+3: Dissolve f radium-228 is 1 m1=0.9 mg by the fact that a standard 434.8 mg of Sr (1,10 1) 2 in distilled water; add not readily obtainable. tenerally the radium- 10 ml of yttrium carrier solution; and dilute 228 must be obtained from thorium metal or pure compounds sufficiently old to permit to 200 ml. equilibrium in-growth.of radium-228. In 40- year-old material the radiuni-2281daughter,° 6. Procedure has reached 99 percent, of equilibrium Um- 6.1 Use 1-4 liters-of sample, on the basis 'centration. The following procedure is used of they expected radium-228 ".content, and to accurately,prepare standardied' thorium: evaporate to 1 liter,- if necessary, Add 5 ml 232 and radium-2.28 from thorium oxide ap- of citric acid for each liter of original sam- proximately 50 yr old. ple, ,and then add' a few drops of methyl 5.14.1 Weigh but a 1.Q000 g sample Of orange indicator. If the solution isyellow, thoi-ium dioxide. add nitric acid until the red color-is obtained. 5.14.2 Transfer the sample' to a 250-ml Prepare standards by dilution of appro- Erlenmeyer flask containing'20 ml of acid priate volumes of the "old" thOriurn-radiUm mixture' (15.7 N HNO, 0.05 N HF). Care- solution to liter. A disintegration rate of fully heat and stir the mixture until, the Tha., 'approximately1,000 dpm isappropriate., dissolves. Transfer the solution to a 200A-ril Carry the standards through the procedure volumetrii flask and add a little barium ni- in, the same'way as a sample.

e METHODS FOR DETERMINATION OF RADIOACTIVE SUBSTANCES 53

. 6.2 Add 10 ml of lead carrier solution. I, 6.4 Tr4ristiVr the aged solution to a cen- 2 ml of barium carrier solution, and 1 ml of trifuge tube, and add 0.3 ml of ammonium yttrium carrier solution. Heat to incipient sulfide, solution Add 10 ,N NaOH dropwise boiling, and maintain at this temperature for 'while stirring vigorouslY, until leacl\sulfide about 30 min with frequent stirring: precipitates; then add about 10 drops excess. 6.3 Add concentrated ammonium hydrm Stir internli tly over a period of about 10 de until the yellow'color of methyl orange is min. The 1 sulfide should settle as a fine- obtained ; then add a few drops excess. Pre- granular nteciPitate cipitate lead and barium sulfates by adding 6.11 Centrifuge the Solution, and transfer 18 N sulfuric acid until the red color reap- the supernatant liquid to clean centrifuge pears; then add 0.25 ml-excess. Add 15 ml of tubes. Di$eard the residue. ammonium sulfate solution for each liter, of 6.12 ?lace the centrifuge tube in a .hot- solution ; keep the sample. at a temperature water both and slowly add 10 N NaOH to the of about 90°C for 30 min and stir frequently. liquid while stirring, until yttrium hydroxide Remove from the' hotplate and allow to settle precipitates; add 1 ml excess and stir inter- for at least 2 hr; then siphon or decant most mittently tor severgtprilinutes. Record the - of the supernatant liquid and discard. date and tithe of the PreciPitaeion. Centrifuge 6.4 Transfer the precipitate to a 40-ml as soon as the Yttrium hydroxide has largely centrifuge tube; centrifuge, and discard the settled. Discard the supernate. supernatant liquid: - 6.13Wash theprecipitatethoroughly 6.5 Wash the precipitate twice with con- With 5 nil Of water containing about 1.0 drops ' centrated nitric acid using -centrifugation of 10 N Naoil, centrifuge, and discard, the wash techniques. Add '25 ml of EDTA re- wash soil-It-ion. agent.' Heat in a hot-water bath and stir in- 6.14 Transfer the precipitate to a 5--dm termittently, adding a little additional 10 N counting Planchet, using small yolUmes Of NaOH if the precipitate does not dissolve distilled Water, While drying under ali infra- readily. red light larnp. The ll,st washing should con- 6.6 Add 1 ml' of strontium-yttrium car- tain 1 ml of binder solution. rier sciatica. Sti-r thoroughly; add a few 6.16 Count the sample in 1 a )ow-b'adk- drops of 10 N NaOH if any precipitate forms. ground100."1 counter for. a sufficient'leng4 of 6.7 Add 1. ml of ammonium sulfate solu- time to(06t,iin satisfatatorY counting statis- tion and stiriDoroughly ; the& add glacial tic. Record date arid time that count begins. - acetic acid dropwise until barii.frn sulfate pre- For most natural waters. a counting period of. cipitates, and add 2 ml excess. Allow the pre- about ,300 to 500 min iS4desirable becausq of cipitate to digest in a hot-water bath until the low concentration of radium-228. the precipitate has largely' settled. Centri- 7. CalculatIOnS . fuge, then discard the supernatant liquid. 44 6.8 cl 20 ml of EDTA reagent,. heat, 7.1 Radium -228 (actinium-228) efficiency and stir. it the barium sulfate precipitate factor: The calcitiation requires a factor for dissolves. eat steps 6.6 and 6.7. in-grow-0i of the actinium daughter.and for .6.9 Dissolye the barium sulfate precipi- tdieocayionol the time interval between. separa- tate in 20 ml of EDTA reagent add 1 ml tion radium parent and beginning oftyttrium-carrier solution an1' mi.of lead of count. . carier' solution. If any precipitate forms- it The cilethic"al recoverY factor is included should he'dissolved by adding a few drops of in overall efficiency and is not separately 10 N NaOH. Transfer the solution to a Teflon identified- Use equation 4 - omitting the f or polyethylene container. Record the date term. and time. Age for 36 hr or longer. Cover the --e-x,t,) sample to prev e,evaporation.) dm (e-Ixto

4 44- TECiINIQUPS WATER-RESOURCESINVESTIGATIOS7S 'where whete =decay constant radium-228 t. =ecay time of radium-228 between (0.1205 yr-'), sampling and analysi in years, Ai= decay constantofactinium -228 and (0.001885 min-9, = counting time in minutes. t,.= elapsed time between certification of \the standard and time of count in The other,,symbols are defined in section 7.1. ,ears, to. time interval between 'final purifica- 8. Report ' tionof barium-radiumsulfate Report values of less than 1.0 pCi/1 to one precipitate (step 6.9) and separa- significant, figure and values above 1.0 pCi/l, tion of actinium daughter (aging to two significant figures. time in minutes) (step 6.12}, and t2=tirne interval between separation of 9. Precision actinium aughter(step'6.12) and counting in minutes. The limited data available suggest that precision of the method is approximately 7.2 Calculation of radium-228 concentra- ±20 percent for a cmientration of 1 pCi/1 tion: Use equation 3 ()lifting the f term. and ±10 percnt at the 10..pCi/l level or Correction for decay of r dium-228 is seldom, abtv_e. required. In addition to in-growth and decay times for actinium-228 cited under 7.1 a cor- rection for decay during counting is required. Reference pCi/I of radium-228 Johnson, J. 0., 1971, Determination of radium-228iin , 1,000c A1t3 natural water: U.S. Geol. Survey Water-SupPly -KVE (e-.) (1-e-V) (e-Xi'_) (1-e-`e,) Paper 1696G, 26 p.

A Radioruthenium, dissolved,as ruthenium-106 Distillation method (R-1150-76)

, Parameter and code: ,Radiorutheniumas ruthenium-106, dissolved(pCi /I): none assigned

1. Application enium to the:tetroxide and to provide a hi h This method is ap liCaMe to analysis of boiling point for the solution. Rutheniufbn nonsaline waters whicdo not contain high tetroxide is then distilled, with the aid of air concentrations of organic matter. Usinga bubble's through the solution, into'a cold maximum sample volume of 100 ml, the de- sodium hydroxide solution. Ethyl alcohol is tection limit is approximately 4 pCi 1. Be- added to -precipitate the ruthenium .as mixed cause of this rather high detection limit, the oxides. method is of value primarily for water samf The ruthenium oxides are separated from pies which have substantial fission product the superiiate by centrifugation, redissolved activity. The sensitivity may be improved in hydrochloric acid, and then reduced to by preconcentrating the runium and by ruthenium metal-oxide mixture by addition counting the sample more.'thathe recom- of turnings. After dissolving the mended 150 min. excess magnesium; ruthenium is recovered by filtration through a taredfilter hand 2. Summary of method counted on a low-background beta counter. }ruthenium salts form the, tetroxide in Recovery is determined gravimetrically. The acid solution when a strong oxidizing agent".corrected activity is compared with that of standards similarly prepared to determine is present. This oxide melts near`room tern-. perature and can be easily volatilized from the ruthenium-106 activity of the sample. concentkated perchloric acid solution, which The restriction of the method, to fresh- boils at approximately 200'C. Distillation of waters a1d low-sample volumes is necessary the tetroxide 'provides an excellent separa-, to avoid large amounts of solids in the dis- tion from almost all potential sources of in tillation flask. The range of usable sample terference. volumes as a function of dissolved solids The method used is essentially that de- has not be evaluated. scribed by Glendenin. (1951). The water sample is evaporated to small volume, and 3. Interferences stable ruthenium carrieris added. Nitric Because the analytical method separates acid is added to oxidize organic matter, ,phos- pure ruthenium, only ruthenium isotopes can phoric acid ia, added to prevent volatilization interfere. On the basis of half-life, ruth- of molybdenum, bromide. and iodide are enium-103istheonlyinterferenceof added as holdback carriers, and so- practicalsignificance. The ruthenium-103 dium bismuthate is added to oxidize the contribution to the total count is less than halide ions to their respective nonvolatile ruthenium-106 contribution (for equal num- oxyacids (Wyatt and Rickard, 1961). Final- bers of atoms) because of Lower counting ly,"perchloric acid is added to oxidize ruth- efficiency. The ruthenium-103etontribution 56' TECHNIQUES OF, WATER-RESOLLRCESINVESTIGATIONS decreases with time and may be 'completely TO LOWPRESSURE eliminatedby several months decay. Alter- natively,the relativelylow-energy betas IR SUPPLY froni ruthenium-103 may be eliminated by counting the sample through an absorber which does not significantly affect the higher energy betas from rhodium -106 (ruthenium-

, 106). Any organic matter present in the sample should.- be destroyed by boiling with a econ- centrated nitric-perchloric acid mixture be- fore proceeding with the perchloric acid dis- tillation.' To prevent explosive decomposition of the distillation mixture, nitric acid should be present as long as any unoxidized organic material remains. Large am,punts'of insoluble matter in the distillation flask may pause serious bumping and impair the recovery of ruthenium.

4. -Apparatus 4.1 Compressed air, 1-2 psi supply for bubbling air through distillation flask. 4.2 Low-background, counter, an anti-co- A FLASK WITH GROUND incidence-type counter with 2 in. thin win- GLASS JOINT' (125M1) dow flowing gas proportional fletector pre- fi ,ferably capable of measuring both alpha and B HOTPLATE beta activity simultaneously. 4.3 Burner, Bunsen, small. C ANNULAR LEAD WEIGHT 4.4 Centrifuge, capable- of. accepting 40- '- ml tubes. D HEAVY- WALL PYREX 4.5 Centrifuge tubes, 40-m1, heavy-wall. CENTRIFUGE TUBE (4001I) 4.6 Distillatign apparatus. Seefigure 7. '4.7 Filter disks, Nersapore, 47 mm, 5 ICE BATH micrometer (Gelman Instrunient Co., Ann Figure 7.Apraratus for distillation of ruthenium Arbor, Mich. 48106). tetroxide. 4.8 Hotplate. 4.9 Vacuum desiccator. 5.5 Magnesium metalturnings. .4.10 Vacuum-filtration apparatus for 47- 5,6 Nitric acid, concentrated. 5.7. 'Perchloric acid, 70 percent. m filters. 5.8 Phosphoricacid,concentrated(85 5. Reagents percent). 5.9 Ruthenium carrier solution :. Suspend 5.1 Bromide-iodide solution, 1 ml= 10 mg 5 g of /*rifled RitC1; in approximately250 Br and 10 mg I: Dissolve 4.7 g Nal and5.2 g, ml of 6/Af HCI and agitate for Several hours NaBr. in 400 ml distilled water. or overnight on a mechanicalshaker. Filter 5.2"Diethyl ether. the resulting solution through a finefilter. 5.3 Ethanol, 95 percent. The solution is standardized by directreduc- Hydrochloric acid, concentrated and tion of aliquots with magnesium metal,fol- . 5.4 the 6M. lowed by filtration and weighing of

C: METHODS FOR DETERMINATIONOF RADIOACTIVE SUBSTANCES, 57 mixed ruthenium oxide and metal produced. ruthenium. Note: It is best to perform the Care should be exercised to dissolve excess distillation behind an explosion shield. magnesium with HCI and to thoroughly 6.7 Continue thedistillationuntilthe wash the precipitate before drying. dense white fumes of perchloric acid have 5.10 Ruthenium standard: Prepare. stand- been carried over for a few minutes. Total ard deposits of ruthenium-106 on filter paper time required for the distillation is usually: starting with ruthenium standard solution 20-30 min. of 100 pCi in 5 ml. Follow steps 6.12 through 6.8 Lower the centrifuge tube from the 6.16 in the "Procedure" section. Correct the delivery tube, and remove the still from the activity determined for decay. hotplate. Disconnect the air supply and al- 5.11 Sodium bismuthate. low the still to cool. When cool, rinse the 5.12 Sodium hydroxide, 6 M. contents of the delivery tube into the centii- fuge tube with a little distilled water from 6. Procedure a washbottle. 6.9 Carefully warm the centrifuge tube to 6.1 Estimate the volume of sample on the near boiling over small burner. Remove basisodissolved solids. The volume is se- frOm the flame and a d, in small amounts, 3 lected to avoid excess precipitation of salts ml of 95 percent ethanol, reheating to in- in the evaporation step. The diAillation flask cipient boiling after each small addition. It is holds 40 without danger of losing sample. important to swirl the solution constantly SamplA volumes in excess of this are ,evapo- while heating. rated to 50 nil in a Teflon evaporating dish. 6.10 Cool the solutiOn, and centrifuge to 6.0TAnsfer the water sjainple into the recover the precipitated ruthenium oxideS. distillation flask, and evaporate down to ap- The supernate should be colorless and may .; proximately 5 ml. Add an accuratOy meas- be discarded. ured amount of ruthenium carrier between 6.11 Suspend the precipitate in 10 ml of 20 and 30.-mg. Record, pipet voluthe to 0.01 isti led water to which 1 ml of 6 MiNaOH ml. a; .een added. Heat (with swirling) to boil- 6.3 'Evaporate to .less than 5 ml. (Pre- .Centrifuge and discard the supernate. cipitation will usually, occur, but the residue 6.12 Suspend the precipitate in a few mil- mug not go diy.) 'cob], the flask and con- liliters of 6 M HC1 and reheat to boiling tents. (swirl' vigorously). Continue heating for a 6.4 Add the following reagents in order: few minutes to dissolve all solid material. Set 1 ml concentrated nitric acid, 1 ml concen- aside to cool. , trated phosphoric acid, 2 ml bromide-iodide 6.13 Add about 5 ml distilled water to the reagent, 0.5 g.sodium bismuthate, and 10 ml ruthenium solution; then acid small portions 70 percent perchloric acid. Mix thoroughly. of magnesium turnings to reduce the ruthen- 6.5 Place the lead-ring weight around the ium to the mixed oxide-metal precipitate.'The flask. Moisten the ground-glass joint with solution may have to be heated to boiling as phosphoric 'acid, and attach the delivefY ap- the reaction nears completion (supernate has paratus to the flask. Place the distillation light-blue color) to speed the process. apparatus on a hotplate, and 'immerse the 6.14 Add (slowly, at first) about 5 ml of end of the delivery tube in a 40-ml centrifuge concentrated HC1, and then heat to 'boiling tube containing 12 ml of 6 M NaOH. The for a few minutes to dissolve any excess centrifuge tube is kept immersed, in an Ice magnesium. bath. 6.15 Filter the suspension through a tared 6.6 Connect the air supply to the still, 47-mm Versapore filter using a vacuum -fil- and adjust the flow rate to a few abbles per trationapparatus.(The Versaporefilter second. Heat the flask slowly to the boiling should be washed and dried by the same pro- point, and then heat strongly to distill the cedure as the sample (see below) prior to 68 CHN4UES OF WitTER-RESOURCES INVESTIGATIONS taring). Wash the precipitale with three 10- 7.2 Calculation of ruthenium-106 concen- 4 to 30411 .portions of boiling water, twoor retion : Use equation 1. Theruthenium re- three 10-m1 portions of 95 percent ethanol, cdvery factor(f) ,is determined from the and with three 10-m1 portions ofdiethyl initial and final weights of ruthenium carrier. ether to dry and_ distribute the precipitate 4 pCi 1 of ruthenium as ruthenium-106 over the filter pad. 1000e 6.16 Remove the dry filter and place in a (1) KVEf ('e a') heated (100°C) vacuum desiccator for5-10 min (no longer). Remove, cool in adesic- cator, and weigh. Mount in a ring-and-disk 8. Report assembly, covering the precipitate with a thin Report ruthenium-106 values of less thai) plastic kitchen-type wrap. 10 pCi/1 to one significant figure.Valu6

, 6.17 Count the sample for \three 50-min greater than 10 pCi/1 are reportedto two ts periods in a low- background beta counter. significant figufes.

7. Calculations , 9. Precision (E) : 7.1 Ruthenium-106 efficiency factor Typical ruthenium-106 values for the pre- Counting efficiency foi ruthenium-106 isde- are ±4 pCi/I or ±20 termined by measurement of the countrate cision of thismCtilpd bf standards prepared by directprecipitation percent, whichever is larger, at the 95-per- of ruthenium metal from atiquotsof the cent confidende level. ruthenium-carriersolution spikedwith known amounts of ruthenium-106. Rutheni2 References um is reduced byMetallic- magnesium, fil- in the Glendenin, L. E., 1951, Improved determination of tered, dried, weighed, and counted as D., in s-Tuthenium activity in fission, in Coryell, C. procedure above. Since recovery is usually Sugarman, N., Radiochemicalstudies: The excess of 90 percent for theentire analytical fission products (Book 3): New York, McGraw- proCedure, the counting efficiency on thedi- Hill Book Co., Paper no. 260, p. 1549. rectly prepared. standards is a reasonably Wyatt, E. I., and Richard, R. R., 1961, Theradio-. accuracte measurement of the countingeffi- chemistry of ruthenium: Natl. Acad.. Sci.; Natl. ciency5of the samples. A typical value is 1.0 Research Council Nuclear Sci. Ser. NAS N,S cpm/pCi. 3029, 78 p. Strontium-90, dissolved Chemical separation and prec ipitation method ( 1160-76)

Parameter and code:Strontium -90,. dissolved(pCi /I): 1350?

1. Application the analysis is improved by counting. after 21 d to allow in-growth of yttrium-9a. The method is applicable to all natural ff strontium-89 is present, it is counted as freshwaters and saltwater& It is applicable strontium-90. Approximately 45 percent of to reactor wastes and may be applicable to industrial. wastes, provided that recovery the original strontium-89 activity is retained tests are made to assure that organic matter 21 d after the initial., precipitation. Stronti- .um-90 may be determined independently b does not hold back strontium. chemically separating the yttrium-90 daugh- ter, and relating its activity back to st ont* 2. Sum ry of method um-90. The composition of a mixture o T method is based on the work of Hahn three isotopes, strontium -90, strViurn-89,' an traub(1955) and of Johnson and and yttrium-90, may be determined approxi- E wards (1967). Dissolved radiostrontium rnately by plotting the growth of radioactivi- isdetermined by beta counting aftera ,ty with time as shown in Johnson and Ed- lengthy separation procedure that removes wards (1967)% other fission products. Stable strontium car- rieris added to the sample, and a car- 3. Interferences bonateprecipitationismade tocollect strontium -90 accompanied by some fission Interferences from both fission prbducts products. The carbonate precipitate is dis- andnaturalradioactivityarenegligible solved, and strontium nitrate mixed with cal- (Glendenin, 1951). As indicated above, stron- cium nitrateisprecipitated with fuming tium-89 is counted as strontium-90, nitric acid: Calcium is removed by washing with acetone, and strontium nitrate is fur- 4. Apparatus ther purified by solution and reprecipitation. 4.1 Filter disks, 25-mm Whatman No. 42, The precipitate may still contain traces of or equivalent. fission products such as transition metals, 4.2 Filtration apparatus for 25-min mem- rare earths, niobium, zirconium, yttrium, and barium. Radium may be present. These are brane filters. all removed by the addition of iron and bari- 4.3 Hotplate. um carriers which are precipitated as thehy- 4.4 Low-background counter, an anticoin- droxide and chromate respectively. cidence -type counter with 2-in. thin -window Vilna] purification is effected' byrprrNipitat- flowing gas proportional detector prefer- ing strontium as the oxalate. Yttiium-90, the ably capable of measuring both alpha and radioactive daughter of strontium-90, has beta activity simultaneously. been completely removed at this point, and a 4.5 Ring-and-diskmountingassemblies new equilibrium begins. The yttrium isotope for filters, including 21-mm diameter rigid is,also a beta emitter, and the sensitivity of copper backing disks. 60 TECHNIQUES OF WATER-RESOURCES INVESTIGATIONS

5. Reagents tration of .1to 10 -mg/1. Strontium-90 5.1- Acetic acid, 6 M. standardctivity (A), after a decay time 5.2Acetone, anhydrous. (t.),. for an initial activity (Ao), can be 5.3Aluminum foil, 3.5 mg/cm2 or less. calculated by use of the following equation: 5.4 'Ammonium acetate, 6 M solution. A =Aoe-x-1-, '5.5Ammonium hydroxide, concentEated where and 6 M. v . x,,- decayconstantofstrontium-90 5.6Ammo9ziuni oxalate, saturated solu- (1.999x10'3 months-1), and tion. L. - tn= elapsed time (in monthh) between 5.7.. um; carrier solution, 1 ml =3.00 certification of standard and time mg Ba 'lye 1.33 g of BaC12.2H20 in account. -414:--.a few drops, of coh- centr_ andilute to 250 ml. 5.17 ThymNphthalein inVicgtor solution. 5; 46% 5 pelcent. 6. Procedure 5,141" er solution, 1 m1=5 mg A reagent blank should, be run with each Fe ": ob mgr' of pure iron wire in set of samples to check for contamination a ...91,nitric acid, and dilute to of reagents, and to permi4n accurate blank correction Ito. be made. Occasional spiked f0t.d; fuming, concentrated, 6 samples.(samplescontainingaknown amount of added stanedyntrshould also be

5,12 inOtAilklein indicator solution. . run through the entirprocedure1s checks.

. 5.13 dctiln:cLabonate solution, 1 M and 6.1 To a 1,000-m1 or other suitable ali- 0.1 M. quot of filtered water sample in a 1,500-m1 5.14 ..'o m chromate solution, 1.5 M. beaker add 20 mg of strontium carrier (5 5.15 Str.ontium, carrier solution, 1 ml=- ml of 4-mg Sr-4-2/m1). Heat' to boiling on 'a 4.00 mg Sr +2: Dry "anhydrous" strontium hotplate. Make the solution basic to thymol- nitrate overnight- at 105°C, and cool in a phthalein indicator (blue color), by .drop- desiccator. Weigh out 9.66 g of the dried wise additions of concentrated: ammonium salt, and dissolve in distilled water. Add 2 hydroxide, and add an additional 6 ml. ml of concentrated nitric acid, and dilute to 6.2 Add 15 ml 001.0 M sodium carbon: 1 liter. A more exacting procedure is des- ate. Stir thoroughly, cover the beaker with cribed by Glendenin 1461), but the a watch glass, and digest on a steam bath for added work is not wanted unless the 1 hr. Add more ammonium ?3rei:oxide, if re- strontium nitrate contains radioactive im- quilicl,to maintain the blue color of thymol- purities which contribute significantly to the phthilein. (Add more indicator jf the color. reagent blank. fades.) 5.16 Strontium-90standard.solution: 6.3 Remove the beaker from the steam Strontium-90 standard solutions calibrated bath, and allow'the prectSitate,to settle while to ± L5 percent are commercially available. the solution cools to room temperature. In purchasing standards it is essential that 6.4 Carefully decant pr draw off. as much the concentration a the, stable isotopic car- as possible of the supernatant solutionowith- rier be known. Dilute t e standard, to ap- out disturbing the precipitate. Transfer the proximately 5 pCi/m1 asdescribedby Barker insoluble material to a 50-m1 Pyrex centri- and Robinson (1963, p. A28). It is fuge tube, and police the beaker with 0.1 M necessary to add both acid and inactiveston- sodium carbonate. Add washings to the cen- tium carrier at the time of dilution' The trifuge tube. Centrifuge and discard the final solution should be approximately 0.1 N supernatant liquid. in hydrogen ion (HCI or HNO,) and should 6.5 Cautiously add 1 N nitric acid drop- have a chemical strontium carrier concen- wise until the carbonate precipitate is corn- ' METHODS FOR DEFIRMINATION1F RADIOACTIVE SUBSTANCES 61 pleteiy dissolved. Dilute to 5 ml with 'dis-.and stir. Allow the precipitate to settle and tilled water. (Note: 1*ere may be a small the solution to cool to room temperature. residue of silica or insoluble metal oxide re- 6.14 Filter through a tared 25-mm filter maining.) Very cautiously add 25 ml of fum- paper (Whatman, No 42) supported on a ing nitric acid (work in the hood, use plas- sintered glass disk of a microanalytical fil- tic gloves, safety goggles or face shield, and tration assembly.' Wash the precipitate with avoid inhaling the vapors!). Cool, stir, and three 5-1 portions of distilled water and centrifuge. then s ccessively with small volumes of 95 6.6 Using the above safety precautions, percbnt ethanol and diethyl ether. Dry in a f,pour off the nitric acid as completely as pos- desiccator.Weighasstrontiumoxalate sible, cool the tube below room temperature monohydrate, and determine the gravimetric using cold water or ice bath, and cautiously yield.. , add 25 ml of anhydrous acetone to the resi- 6.15 Mount the; filter on a copper disk, due. Stir thoroughly and .centrifuge, again 21-mm diameter. Cover with aluminpm foil discarding the supernate. (3.5 mg /cm2 or less). Store the sargole for 6.7 Repeat step1.8.6. 21 d to permit in-growth of yttriuln-90 to 6.8 lve the nitrates in 5 ml of dis- 99.5 percent of equilibrium activity. If it is tilled water, anplace the tube in a boiling- desired to break down the activity into the water bath until the odor of acetone is gone. three radioactive isotopes, it is necessaryjto (Caution: be sure acetone is completely re- start the counting within a few days of sfrp moved.) 6.15 so that the decay of strontium-89 and 6.9 Cool below room temperature, and'in-growth of 314krium-90 may be obierved. g precipitate strontium nit/ate by add- 6.16 Count e sample for 100'n 'In a in 5 ml of fuming nitric acid. Swirl, cool, low-background anticoincidencesided ancents)fuge. card the supernate. beta counter. isso precipitate in 10 ml of wate dd 5 mg of ferric 'carrier 7. Calculations (1 mlof 5-m 3 per ml) and '15 mg of bIi u arrr (5 of -mg Ba+? per m1) 7.1 Strontium-90efficiencyfactor(E) Add con rated ammonium hydroxide with and fractional chemical recovery (f) : Use constant stirring until ferric hydroxide be- equation 2. Determine f froth the weight of gins to precipitate. Then .add several drops 'strontium oxalate. excess. Centrifuge,.and decant the supernate -Fn into a clean centrifuge tube. This operation E ,(2) removes the yttrium daughter of strontium- df 90. Record the time and -date. where 6.11°Add phenolphthalein indicator, and . x= decayconstantof..strontium -90 add 6 N nitric acid dropwise until the pink (1.999 x10 3 month-1). color disappears. Add 1 ml of 6 N acetate 7.2 Calculation of strop iu 0 concentra- acid and 2 ml of 6 M ammonium acetate. tion: Use equation 1, making the,ecay cor- Place the samples i n a boiling-water bath rection if necessary. Determine f tom the and add 1 ml op.5. M ?sodium chromate weight ostrontium oxa precipite. while agitating. Leave in the water Vath for 0 c 5-10 minutes. pCi/1 of strontium-90 (1) 6.12 Cool to room temperature, centri- KVEf fuge, and decant th supernate into a 100-ml According to Hahn and Strau.(1955), beaker. Discard the ecipitate. the chemical.recoveries range from- .approxi- 6.13 Add 2 ml of concentrated ammon- mately 72 to 80 percent. Accurate determi- ium hydroxide, d heft to boiling. Add 5 nation of chemical recovery requires knowl- mi of saturated a onium oxalate solution edge of the natural strontium content of the

LI 62 TECHNIQUES OF W TER-RESOURCESINVESTIGATIONS sample..Normally this is less than mg/1 9. Precision and may be neglected! In a few ca es, par- Minimum detection level is 0.5 pCi/1 and ticularly with waters from an area extending this is also the precision at ,activities below through parts of Wisconsin and Illinois, the strontium content may equal or exceed the 5 pCi/l. At higher .0trontium-90 activities sriontium carrier added, and natural stron- the precision is -±10 percent. tium must be determined for the calcula- tion of chemical recovery. 7.3 Calculation of stronticm-90, yttrium- \ References 90 and strontium-89. The cotiht rate is de- termined at intervals over a'timespan of ap- Barker, F. B., and Robinson, B. P., 1963, Deter- mination of beta activity in water, 1LS. Geol. proximatelir 30 d starting as close to zero Survey Water- Supply. Paper 1696A. time as possible. A typical counting sched- ule thereafter would be at 24 hr, 48 hr, 100 Glendenin, L. E., 1951, Determindtion of strontium hrl 200 hr, and no hr. The count races are and barium activities in fission, in Coryell, J. D., and Sugarman, N., eds., Radiochemical studies: plotted rt ainst time, and the curve t us ob- The fission products, National Nuclear Energy tained is compared against type cury s for SeriesIV,9,_ Paper" no.236: Ngw York, different isotopic ratios of strontium-90 to McGraw-Hill, p. 1460-69. strontium -89 (Johnson and Edwards, 1967) 44 to obtain the ratio foripe sample. Hahn, R. Z., and Straub, C. P., 1955, Determination 1.9 of radioactive strontium and barium in water: Am. Water Works Assoc. Jour: v. 47, \p. 8. Report 340. rs Report strontium-90 equivalent activities Johnson, J. 0., and Edwards, K. W., 1967, Deter.: to ±0.5 pCi/1 or to ±10 percent, whichever mination of strontium-90 in water:...E.S. Geol. is greater. SurveyW- SupplyPaper 1696V10 p. S

1' :4) +ritium Liquid scintillation method, Denverlab. (R-1.171-76)

Parameters andcodes: Tritium dissolved(pCi /I): 0005 Tritium,in water molecules (Tu): 07012 ,

1. Application secondaryscintillatorusedtoshift "trrelength of the scintillations to themat- , The technique is generally applicable t sensitive spectral region of thePMtube. the determination of tritium artificially in- Much of the tritium data reported iri the - troduced into water by suchactivities as vas determined by use of the above tracer experiments, nuclear power, waste litersre scintilla ixture. The dioxane-PPO com- disposal, and thermonuclear weapons testing. bination has been superseded by, proprietory The technique is not sufficiently sensitive to scintillators that produce gels when mixed be applicable to the determination of very with water in proper ratios. The newer scin- low natural tritium levels. tillatoFshave approximately doubled the sensitivity of liquid scintillation counting for 2. Summary of method tritium. Since the composition' of the pro- Liquid scintillation counting is based on prietory mixtures is, not available, these are the conversion of the energy ofaparticle listed by trade name in the "Reagent" section. emitted by a radioactive nucleus to light ener- While the Mechinism of liquidtscintillation gy by means of a scintillating chemical. The counting is not completely understood,it scintillations are detected by a' photomulti- seems clear that the energy transferis a two- plier (PM) tube. The electrical signals from stage process, with initial, energy transfer-to the PM tube are amplified and sent through the solvent followed by transfer fro,,the simple multichannel analyzer (three or solvent to the scintillator. Many subifancea°,( four channels at most) wheresortilig,into each chan- including water, interfere in "the energy energy takes place. The counts in transfer process to quench the scintillations nel are displayed on a scaler and may be read and red ace the count rate. Excessive salt con- out on paper tape, punched tape, or- magnetic tent, certain metals, and organic compounds tape. quench in varying. degree. Colored substances Liquid scintillation counting is primarily may quench by light aisorption inadditiOn used for the counting of beta emitters al- to interfering with energy transfer.Quench-- though it can also he used for alpha-emitting ing sUbstances are generally removed ' by isotopes. When liquid scintillation taunting is used vacuum distillation. - todetermine a radionalide in aqueous solu- The quenching effect of water is compen- tion, the water sample is dissolved or dis-. sated by usinga,constant volume of water persed in a large volume of organic solvent and constant ratio of, water sample to scin containing the scintillating chemical. A wide- tillator mixture in both samples and stand- ly used mixture for aqueous solutions was ards. The ,count rate of a particular sample dioxane-naphthalene containing the scintil- depends on bothe volume of sampleari/i latOr2,5-diphenyloxazole(PPO)anda the ratio of liid scintillator mixture to

_

C t_l

4 64 TECHNIQUES OF WATER-RESOURCESINVESTIGATIONS water sample. As the fraction of water sam- Operationprogrammable and automatic. Internal checkan external standard and ratio ple in the water scintillator mixture in- computation capabilitz recitiired. creases, count rates increase until a point is ReadoutNutomatic _printout. reached where the quenching effect of the additional tritiated water exceeds the effect 4.3 Pr. 8 ml. of the increased radioactivity. It is found 4.4 Vauum-distillation- apparatus. Con- that a practical compromise between maxi- sists of a 50-ml round-bottom flask as the distillation flask and a 125-ml and-bottom mum sample volume. and scintillator vol e provides optimum sensitivity. The maxim m flask as the condenser flask. ThIlleistillation on the curve of activity versus volue of flaskis( /heated with a rheostat-controlled tritiated water (in a constant overall vol- mantle, and the condenser flask dips into a ume) is a rounded plateau.. Therefore, the Dewar coftfaining isopropanol-dry ice. The proportion of water sample to scintillating two flasks are connected by a 20-mm diame- liquid mixture is not critical and is ea.gily ter U-tube, 10-cm long with ground-glasi con- nectors and stopcock forapplicatiOnof ieproducible in routine work. . The permissible ratio of water sample to vacuum. Heating tape is coiledaigund the liquid scintillator mix is also controlled by U-tube connecting the two flasks. physical stability of the gel formed. A detailed description of the method is 5. Reagents given by Schroder (1971). 5.1 Scintillatgr,Instagel(pack*rdIn- strument Co.) for low-temperature counting 3. Interferences (1°-4°C). A preblended gel-forMing Distillation is used to remove both quench- designated3A70 *.(Research ing substances an4 radionuclides that could Products International) for room-tempera contribute to e3celss count. Distillaticinis ture,counting. fully effective in removing inorganic salts 5.2 Tritium standard solution!: Appropri- and high-boilikg organic' ,compounds. -Or- 'ate'standaids are prepared by the dilution of , gimic materials that vaporize at a lower tem- NBS standard tritiated water with "dead3 pe e than 'water 'and are condensable water, that is, water containing less than 1 under the same conditions as water vapor Tu. may be carried over in the vacuum distilla- 5.3 Water, "dead." The tritium, blank in- tion. IP'these materials contribute either-troduced by reagents mnst be tested at inter- quenching or beta radioactivity the possibili- vals by analyzing -"dead" water (water with ty of interference exists, although it would no measurable tritium content) in exactly appear remote. the same procedure as for a normal water Further protection against int erences sample. It. is very 'difficult to confirm that a is provided by the energy discriminaiion in water is truly-"clead," and it is usually neces- the liquid scintillator analyzer andtheex- sary to make the assumption, that water from ternal standard-ratio test. a deep well in a confined aquifer a hundred 4. Apparatus kilometers or more from the recharge area 4s 4d Autopipet, 25,ml maximum capacity. "dead." This assumption can be correct only 4.2 Counting equipment. Liquid scintilla- if the well is pumped sufficiently to expel all tion spectrometer; counting systems capable meteoric water that may have entered the of meeting the following specifications : well and surrounding aquifer by leakage. Counting efficiencynot lessl than 24percent with optimum sample-scintillator mixture and 6. Procedure polyethylene vials. . 6.1 Counting. Backgroundnot to exceed 5 cpm at sea level 6.1.1 Distill ml of water sample for in tritium channel. pi Sample capacityat least 100sartiples! direct counting, or a proximately 10 ml of

0.

C r METHODS FOR DETERMINATIONF RADIOACTIVE SUBSTANCES st electrolyzed water sample, using the vacuum_end of the counting itin (see instrument in- distillation apparatus. The U-tube ispre- struction manual). This procedure is,a check heated to assure dryness. for quenching; The ratioof Jow.:energy 6.1.2 Pipet 8.00 ml of the distillate from counts in channel A of the spectrometer is the preceding step into,a 25-m1 polyethylene established fOr both tritium and .an external vial, and add 14 ml of scintillator mix. The standard placed near the sample vial. The choice of scintillator depends on the type of value of R in the following equation thouid liquid scintillation spectrometer to be used be constant to within ±0.2. for counting. Instagel is used with the in- r Counts inA.tritium] struments that operate at cold temperature. Counts in B - , ... (3°C), and 3A10* is used with the instru- in Bstandard]. ments that operarte at room temperature. Cap Courits in the vial ancrmix. 'Heat the Instagel-sample. Indidual samples thatfaloutside! this mixture on a liptplate' at approximately rane must be reanalyzed. If allvaluets of R 100°C for 2 or 3 min. This clarifies the mix- faloutside this range', the scintillatdr has' ture. The 3A70*-sample mixture does not re- detriorated and must be replaced. quire heating. The above operation' is carried out under st.id,bdued red light to filter out the ark:Hone° , fable region of the spectrum. This minimizes everal statistical schemed ha've been pre- excitation of fluorescence background in the sample. -sented for the calculation and verification of tritium data, each intended to optimize a par- 6.1.3 Prepare three blanks and Iwo tI4ular analytical situation-. In the present standards in the same manner the Jam-{analytical procedure the repeated counting ples. Place one standard in the 2ci counting of individual samples- has the of aver-_. position in the spectrometer and one inhe aging out short-term fluctirati ". Statistical.' 10thposition.Place blanksatintervals checks have shown that highest precision, in throughbtit the run of 10-14 samples. this analytical situation, is attained by the 6.1.4 Place three sealed standards (tri- use of longer tern average values forthe ated toluene in glass-sealed scintillator solu- Elam pies and standards. tion) in the . One standard-goes in the first counting position to permit monitoring Counting efficiency and background values the instrument before counting the-samples.. are determined with tritiumstandailliLwhen= The remaining sealed' standards are' placed ever a new lot of scintillator is used. Count- ing-efficiency data and background.data from near the blgnks: set are 6.1.5 Allow prepared samples remain standards alid blanks run also determined. The nyw data' each set, in thda in the liquid scintillatio ec- preced- A trome er foseveral hours before counting are averaged into the data from the begins. This a ows decay of fluorescence and ing sets, thuS creating a moving average value for counting efficiency and background. chemiluminesc nce A minimum of8hr As new efficiency and baCkgrotind data ap- standing is r juirei with Instagel and 12 hr pear they displace older data entered into the with 3A70*. moving average. Data from four'or five valid 6.1.6 Count each vial five times for 100 runs (no quenching orotheriberration), en- min. Total Counting time for one sample is ter into the moving average-used at any given 500 min..Counting time is reduced for very time. active samples'. One million counts is cutoff setting. 7.1 Tritium efficiency factor.(E). Use 6.1.7 Program the instrument to per- equation 2: c, form the external-standard °ratio analysis E- (2) on samples, standards, and blanks at the dn(e-x`-) I ' 66 TECHNIQUESOF WATER-RESOURCES INVESTIGATIONS where 7.3 -Ctitwersion of tritium "concentration en= average countrate ofstandard in pCi/1 to tritium uniils. Tritium c6ncentra- (cpm) corrected for ;background pCi tritium/1. Lion ice, and blank., 3.22 dn= disintegrationrateofstanddrd r (dpm), corrected for blank(.§ 8. tepert , A= decay constant of tritium(4.685 Concentrations in both tritium units and x 10-3 month -'), picocuries pet liter are reported to two sig- t,.= elapsed time between certification ofnificant figures down to the minimum detec- the standard and time of count in tion level (MDL). The 'latter can onIP be same units as 11a estimated because of the very pronounced where effect of...Altitude frn the background, count. S= movingaveragecountrate At sea, level the MDL is estimated, af 60 Tu, (cpm)of the standards, and and at 5,000 ft (1,500 in) it pis estimated' at /13 =movingaveragecountra 150 Tu for the direct count method. (cpm)of the blanks. . 7.2 Calculation of tritium conctration : 9. Precision Use equation . The chemical reCovery. factor Precision is dependent on altitude in the (f)is an, enrichment factol- when electro- same way as 1VIDL. At 500 Tu reprollocibility lytic enrichment is applied 'to, the sample. is approximately ±20 percent. Preciion im- Since electrolysis is not used the value of f o351 yes with increasing concentration. is unity: '1,000C-, pCi tritium/1= (1) ,Reference KVE f (e-") where if is electrolytic enrichment factor de- Schroder, L.J., 1971, Determination of ;tritium iti te,rmi.ned by standard included in the run, - water hy the U.S. Geological Survey, Denver, Colo.: U.S. Geol. Survey .Rept. cpm/ml after electroOis f 22 p.; ,Avail. only from U.S. Dept. Commerce, cpm /m1 beforeelectrolysis Natl. Tech. Inf. Service, Springfield, VA 22151.

t

#

A Tritium Liquid scintillation method, ,kestorl lab (kr-1173-76)

Parameters andcodes: Tritium, dissloiod (pCi/1): 07005 Tritium,in water molecules (PO:" 07012

1. Application on to the energY, analYzer and scalar cir- The technique can be used directly to an- cuitry. alyze waters containing more than 60 Tu ; When liquid. scintillation counting is.used (190 pCi/1). Many natural-water samples to determine a radionuclide in aqueous solu- contain less than 60 Tu so the tritium in tion, the water sample is dissolved or dis- such samples is normally enriched by elec- persed in a iat'ger volume of organic solvent trolysis (method R-1174-76) before they are containingthescintillatingchemical. A analyzed by this technique. widely used tnixture for aqueoussolutions The direct liquidscintillation counting wasdioxafiehaPhthalenecontainingthe method, while useful for analysis of the tri- sointillator, 0,4-callenYloxazole (PPO) and tium introduced into water by rainout in a secondary. seintillator used to shift the some samples, is primarily used for measur- wavelength et the scintillations to the most ing tritium introduced in tracer tests. and .sensitive spectal region of the PM tube. locally by nuclear power and waste disporl Mudh early tritium data was determined by facilities. use of the above scintillation mixture. The diox ne -PpO cornhi4ation has been super- 2. Summary of method sed proPiietory scintillators that pro-' duce gels whert mixed with water in proper Liquid scintillation counting is based on ratios. The fielder seintillators have approxi- the converslon of the energy of a particle mately doubled the sensitivitY of liquid scin- emitted by a radidactive nucleus to light tillation counting for tritiurn. These solu- energy by Means of a scintillating chernical. tions generallyinclude an organic solvent The scintillations are detected by a photo- 4toluene or nlene,1 for example) in which multiplier (PM) tube. The electrical signals the- scintillat'°r is dissolved, plus a strong from the PM tube are amplified and sent liquid detergent to promote emulsificationbe- through a two .or three channel analyzer tween the salnAle water and the scintillator- where sorting by energy ranges takes place. containing organic The counts in each cannel are displayed on solvent. a scaler and are printed and (or) read out Since the compositionposition of thepro- on punched tape or magnetic tape. In order prietary iniSttlres is not available,awe, these are to minimize spurious counts, from cosmic listed by trade name in the reagent section. radiation or electrical noise inherent in the While the tneehanism of liquid 'scintilla- PM tubes themselve§, for example, two PM, tion, counting- is completelynot counderstood, undestood, tubes are used to detect the scintillations. it seems clear that the energy transfer is The twq tubes are operated in concidence, so a two-stage brocess, withinitialenergy that only if a scintillation event is detected transfer to the solvnt followed by transfer by both tube's simultaneously is a signal sent from the solvent to the ,scintillator.. MattY '20 61 yr- TECHNIQUES OF WATER-RESOURCES INVESTIGATI6NS 68 dip substances, hielliding water, interfere in the results. Radon has a 'short half-life (3.8 d). energy transfer process to quench the scintil- and its presence ig obvious from adecline in lations and rejitice the count rate. Excessive .Count,rate whilesample i5 counted over a salt content, certain metals, and organic coin- period of several `days or a week. pounds quench in varying degree. Colored A radon-containing sample can' bepuri- substances may quench 'by light absorption fied by distilling it to remove anyi parent in addition to 'interfering with energy trans- radium-226, allowing the sample' fo stand fer. Quenching substances are generally re- for 3-4 weeks for the radon, td decay;and moved by yOuum distillation. redistilling before counting to remove, the The quenching effect of water is compen- radon daughter lead-210. t sated by using a constantvolume of water The analysis of tritium in highly radio- and constant" ratio of water sample to scin- active samples, such as those: fromnuclear tillator mixture in both samples and stand- faciliti ,may be confused by the presence ards. The count rate of a particular sample of oth r radioactive noble gases,particUlarly 'depends on both the volume of sample and kry 5 and argon-41. Rhinehammer and the ratio of liquid scintillator mixture, to L erger (173) discuss techniquesfor water sample. As the fraction of water sam- ritium analysis in the presence of concen- tIlein the water scintillfator xxture i tration of other radioisotopes much higher hases, count rates increase pti a poin is than found in natural samples. ached where the quenelliM effect othe Samples prepared for counting by elec- Etional tritiated water exceeds the effect trolytic enrichment are normally free \ of he increased radioactivity. Itis found radioactive or quenching interfering sub- at a. 'practical compromise between, mfoci- stances. mutt sample v and scintillator volume Oxge 4. Atkibratus sample sftlutigh-it wa'tonsta total volu);' vary slightly without af- 4:1 Counting equipment, Had scintilla- fecting the touing characteristics, of, the tion spectrometer, with two PM tubes, oper- mieThus -optimally sensitive -Mixesan bedating in coincidence minimum of two chan- produced inroutine work. nels for pulse-energy analysis; automatic The permissible ratio of water ,sOmple to sample changerominimum 100 samples; con- liquid scintillator mix' is also controlled by stant temperature chamber. for PMtubes physical stability of the "gel formed.A de- and shield and sample changer, adjustableto tailed description of the method is given by as low as 0°C; readoutdevite(s) to paper Schroder (1971), and the counting charac- forvisualinspection /ofresults and to teristics and thermal stability of various punched tape or other automatic data proces- water-schitillatorsolutionmixturesare sing (ADP) compatable forth fo data trans- given in the manufacturers' literature. fertocomputef forfinalcalculations. Optional :automatic cxternal. standardiza- 3. Interferences tion by channele-ratfo fnethod for quench Potential interferences 'come from other terminalibn. Properly prepared samples do radionuclides or que}ling substances pres- not differ in quenching, and this determina- types are removed tion is unnecessary. The presence of the ex- ent in the sample. Bot the counting' by vacuum distillationf the sample before; ternal standard source near preparation of the 'counting mixture. chatnber may add additional' background. A rare ground-water sample may contain Counters as received from the manufac-) radon-222 in an amount large enough toper= stifferWill not normally be adjUseed fors sist in the sample even after distillation. optimulm counting '.,of water'ini,d;tfres,. and Some radon decay is counted in the tritium before routine tritium measurements are be-' energy channel and tospuriously high must be carefully adjusted, in the laboratoyy METHODS FOR DETERMINATIONOF RADIOACTIVE SUBSTANCES 69 gTLNAdjustments are possible to:- PM-tube standard tritiated water with "dead" water, high 2V-i_j)1 tage; amplifier gain; energy anuirz-°-thatis., water'containing less than I Tu. A ing channel limits; and (by a manufacturer's standards containing 52 to 1.00 dpm/m1 tri- 'representative) the time interval in which a tium (7 to 15 x 103 TO is adequate. pulse' in one PM tube is taken as simultane- 5.3 Water, "de d"'., Water with no meas- ous with a pulse in-the other and sent on to urable tritium ("da-dS water) is required the analyzer cir uitr-T-r. ------for determination of counter- background The type ofintillator solution and opti- rate and for dilutit of standard tritia mum water to ution,ratio of the counted water. It is very dicult to confirm .thaf a mixture must albe chosen, and the count-, water is truly "dead," and it is usually neces- . ing-chamber, temperature set as low as pos- sai-I. to make the assumptihn-trat water from .sible to minimize PM-tube noise without a deep well in a confined aquifer a hundred causing-'the counted mixture to separate or) kilometers or more from the recharge area freeze..' , , is "dead." This asst.!1_lytion can be correct the utility of a liquid scintillation spec- only if the well is pumped sufficiently to ex- trometer for low-level counting isdeter- pel all meteoric wafer that may ha've entered ''=,. mined by its background count rate ancl,its the well a d surrounding aquifer by leakage; tritium-counting3erftrency.A frequently used counting mire consists of 12 ml 6. Procedu H2O sample plus' 13 ml Insta-Ge (Packard 6.1 Distillation.Samplesenrichedby Instrument- Co.),ina polyethylene vial._ electrolysis are distilled in the finalt of Presentlyavailable (1976) commercial that procedure and require no furth reat-L.... counters are capable of counting this mix- ment before preparing the counting mi re. ture, with efficiences of 20 percent or greater. All other samples,must be vacuum distilled and backgrounds of 3.6 cpm or less. Older before preparing the counting

counter sample changer for at least 24 hr the set. . , 'before counting °begins to reach thermal 7.2 Calculation of tritium concentration. equilibrium and for chemiluminescence (if Use equation 1: any) to decay. Members of each 'set are counted sequen- Tu- (1) KVEf (e--m) es. tially ifor a preset time (40 to 100 min) or until a preset number of counts (5,000 to where 10,006) 14ve accumulated. The counter then C,..average ',sample 'count 'rate above records the sample number, count time, and background (cpm), counts accumulated,aW moves the next sam- V=mass of sample water counted (g), ple into,position. Aft g. the last samples the E= counting efficiency, from equation 22 sample changer returns to the first sample [cpm and the cycle repeats. If the automatic external-standardization dpm option on the counter is used, the standard- f= electrolysis enrichment factor. For ization is done at the end of each count on samplescounteddirectly, 1=1 each sample and the results recorded befope (for calculations of f for elec- changing to the next sample.le. trolyzed samples, see method R- Thtotal time requireiik'for counting a 1174-76), same e is determined by Tritium content X= decay constant of tritium(1.534 (see sec. 7.3 below) , If a set contains several x10-4 d-'), high-tritiuin samples, these can be removed, t= time elapsed between sample collec- individually when they. have .counted long tion date and date counted,ikt. enough, and counting of the remainderpf same units as A, and the set continued. K=T.14x10-'3 dpm/g Tu. 07.3 Calculation of tritium counting error. 7. Caleuldtions The error term which accompanies tritium 7.1 Tritium counting efficiency (E). Use results is,calculated, such that there is a 67 equation 2: percent probability that thetrue tritium content of the sample is in the range of the 6 E- (2) reported value ± the error term. d(e-xC)xV' Errors of tritium analyses are due pri- where marily to th uncertainty inherent in any attempt to rheasure the rate of occurence =average count rate of standard (count rate) of a random, process(radio- (cprit) above background (S-B), active decay). For a count' rate, R, the d=disintegrationrateofstandard standard deviation .a=R/t, where tis the (dpm /g), total count time. Errors in counting both V=mass of standard counted kg), the sample and background are included in x=decay constant of tritium (1.534 the' net.sample count rate C, above. That x 10-' d -'), is, if C =S -B, tTelapsed time between certification 2 2 crC = (3) - of the standard and time of crg =B count in same units as A, In sets counted as described above, the count -, where ing time for background and sample are,...the S= average count rate(cpm)of same, so equation 3 can' be written :4 the standard, in the set, and c/C = V (C+ 2H) /t. .(4) 1SL

METHODS FOR DETERMINATIONOF RADIOACTIVE SUBSTANCES 71

4o The relative'eir'of, or precision of the count 8. Report rate measurement ig Tritium errors are reported to two sig- gC/C. nificant figuks or to the nearest 0.1 Tu, Thus equation 4 show's that-ahalytica.I pre-__whichever is larger. The tritium result "it= report)ed td the same number of Sig- cisionincreases(gC/C becomes smaller), . with longer count time, or,itor a fixed count. nificant figures.- time, increases with high7 sample count Tritium data 'ave-frequently requirep in ttyriAltan in Tu. To7conyert, usthe rates (a higher 'tritium-CountingMolexi Cy,, or a.,higher sample tritium concentration) ekfiression: or with a lower background count rate. PCi tritium/1-3.2 Tu. 'In addition-to the count-rate error, small errors are associated with each of the other 9. Precision terms in equation 1, and the reported gl. is The precision of tritium analyses varies calculated with the expression with sample tritium content and with labora- (gEy_fly tory configuration and location. The one uTu Tu x +( standard deviation(1g) error is reported C v E ) f ) with each result. The calculation of this (5) error is described above (sec. 7.3). There are also errors associated with the K and (e-m) terms in equation 1, primarily References due to uncertainties,in the knowledge.of the Schroder, L. J.; 1971, Determination of tritium in tritium half-life, but they are negligible for water by the U.S.. Geological Survey, Denver, most purposes. Colo.: U.S. Geol. .Siirvey Rept. USGS-474-134, Because Tu-error calculations are tediolik 22 p.; Avail. only from U.S. Dept. Commerce, and complicated, they are done by computer Natl. Tech. Inf. Springfield, VA. 22151. Rhinehammer, T. B., d Lamberger, P. H., 1973, from the counting data _punched or other- tritiumcontent technology, U.S.A.E.C. report wise directly recorded by the counter. WASH=1269, 292 pp. (Avail. from NTIS).

4 '410"

!?, Tritium Electrolytic enrichment liquid scintillation method, Deriver lab (R-1172-76)

Parameters and codes: Tritiu dissolved, (pCi /I): 07005. Tritium, in water mole les(Tu): 07012

1. -Application' tt*hniques were introduced by Kaufmann

Gas countingspreceded by electrol I en- and Libby (1954). richment is the- mbst sensitive analytical Electrolytic enrichment is carried out by method.for tritium and is applicable down to adding sodium peroxide (forms sodium hy- concentrations in the range of 1. Tu. With droxide), followed by carefully controlled very careful control of ambient laboratory electrolysis in specially designed' Cells. The tritium levels, and a valid blank based- on. cells of ostlund and Werner (1961) are u \ ied. "dead" water,,it is possible to apply the meth- -rrr4e - isotopic fractionation factors are m- od to waters as low as 0.2 Tu. Where gash proved by operatic% at low temperature. counting equipment is not available qr where Hence, the electrolysis is, carried out while a lower detection limit of 25 Tu ir 'satisfae- the ceA.are partially immersed in a cold bath tory,electrolytic enrichment followed by maintained ato a temperature just above liquid scintillation counting permits the anal- freezing. ysis at lower concentrations than by liquid Thz percentage of recovery of tritium in scintillation alone (method R-1171-76). The the electrolysis is a complex funcVs of tem- technique also may be applied to samples hay-, perature, current density, and electrode sur- ing high concentrations of nonvolatile radio- face reactions which ar t fully understood. activity contamination such as strontium-90, Practical systems have b developed which because thetsample preparation steps elimi- achieve 70-80 percent recovery of tritiunkin nate Solid materials. electrolysis from approximately 500 to 10 Thi' ----The technique is generally applicable to More extensive electrolysis provides g determine tritium introduced into water by enrichment but lower percentage of recovery. rainoiit and to measure natural levels of tri-/The reproducibility of recovery between 04*- tium in surfale4 watify/The technique is not is approximately 3-4 percent under normal conditions. fficiently sensitive fdr the deterfnination of Liquid scintillation counting is based on very low natural tritium levels. the conversion of the energy of a particle 2. Summary of method emitted by a radioactive nucleus to light energy by means of a scintillating chemical.. When it is necesary to determine tritium The scintillations are detected by a photo; at a lower concentration, with improved ac- multiplier (PM) tube. The electrical signals' curacy, than is available in the liquid scintil- from the PM tube are amplified and sent lation method (R-1171-76) , an electrolytic throughasimple multichannelanalyzer enrichment step is introduced ahead of the (three or four channels at most) where sort- liquid scintillation counting. The electrolysis ing into energy takes place. The counts in

73, 74 TECHNIQUES' OF WATER-RESOURCES INVESTIGATIONS eaclir channel are displayed on a scaler and the ratio bf liquid scintillator mixture to may be read out on paper tape, punched tape, water sample. As the friction of water sam- or magnetic tape. pleinthe water-scintillator mixture .in- biquithecintillation counting is used pri- creases, count rates increase until h point is marily for the counting of beta emitters al- reached where the quenching effect of the though it can also be used for alpha-emitting additional tritiated water exceeds the effect isotopes. of the increased radioactivity. It is found When liquid scintillation countinis used that \.a practical compQmise between maxi to determine a .radionuclide in us solu- mum sample volume and scintillator volume tion, the water sample is dissolved or dis- provides optimuiLsensitivity. The maximum persed in a larger volume of organic solvent on the curve, of activity versus volumeof t4- containing the scintillati chernichl. A wide- tiated watx (in a constant overall volume) ly used mixture for aqous solutions Was is a rounded plateau. Therefore,.the propor- dioxane-naphthalene cotaining the scintil- tion of water sample to scintillating liquid lator 2,5-diphenyloxaz e (PPO)', and a sec- mixture' is not critical and is easily, repro.; ondary scintillator used to shift.the wave- du,cible in, routine work! I length of the scintillations to the most sensi- e The peripissible ratio of watersample tive spectral region of the PM tube. Much of liquid scinTillator mix is alSo controlled b the tritium data reported in the literatureAphysical stability of the gel formed. was determined by use of the al:ve scintilla- A detailed description of the inethod is tion mixture. The dioxane-P0 combination given by Schroder (1971). has been superseded by proprietory scintil- lators that prbduce gels when. mixed with 3.Intirferences water in proper ratios, The newer scintil- There are no interferences in the analyti- lators have approximately doubled the sensi- cal met w n electrolysis is included. Dis-, *tivitz of liquid scintillation counting for tri- tillati d to remove both quenching tium Sinca the composition of the proprie- substa radionuclides that could con- tory mixtures is not available, these are listed'tribute xcess counts.Distillation and by trade name in the "Reagent" section,, electrolysis are fully effective in removing ,While the mechanism of liquid scintilla- inirganic salts, high -ling organic 'com- tion counting is not completely understood, it pounds, and gaseous -ridiois'otopes. seems clear thatthe energy transfer is a two- arid all other gases are' stripped out in the -stage process, with initial energy transfer to ele trolysis owing to prolonged bubbling of the solvent followed by transfer from the sol- ox rr-and hydrogen.through the sample. vent to the scintillator. Many substances, in- Further protection against interferences.. cluding water, interfere in the energy-trans- is provided by the' energy discrimination in fer process to iluench the scintillations and'the liquid-skitillathe analyzer and the eX- reduce the count rate. Excessive salt content, ternal standard-ratio test. certainmetals,andorganiccompounds quench in varying degree. Colored substances may quench by lightabsorption in addition 4. -Apparatus to interfering with energy transfer. Quench- 4.1 Autopipet, 25-ml maximum capacity. ing substances are generally removed by 4.2 Counting equipment. Liquid scintilla-, vacuum distillation. - tion spectrometer; counting systenicap- able The quenching effect of water is compen- of meeting the following specificaU/On13: sated by using a constant voloume of water Backgroundnot to exceed 5 cpm at sea level and constant ratio of water sample to scin- in tritium channel. tillator mixture in ):loth samples and stand- Counting efficiencynot lessthitn .24 percent ards. The count rate of a particular sample with optimum sample-scintillator mixture and depends on both the volume of sample and polyethylene vials.

ti '`) .2 -)* METHODS FOR DETERMINATIONOF- RADIOACTIVE SUBSTANCES 75

A Sample capacityat least 100 samples. 4.4 Pipets, 8-ml. Operationprogrammable and automatic. 4.5 Vacuum-distillation apparatus. Con- Internal checkan external standard and ratio computation capability required. sists of a 100-ml round-bottom flask as the Readoutautomatic printout. distillation flask and a 125-ml round-bottom 4.3 Electrolyszunit. Contains the follow- flask as the condenser flask. The distillation ing components: flaskisheated with a rheostat-controlled 4.3.1 Electrolysis cells. See figure 8. The tle and the condenser flask dips. into a Ostlund cell has a mild steel cathode (where Dew containing isopropanol-dry ice. The reduction of hydrogen isotopes occurs) and two flasks are connected by a 20 min diame -. stainless-steel anode. The glass envelope is ter U-tubd, 10-cm long with grow-glass con- designed to attach directly to a vacuum-dis- nectors and stopcockfor 'ap licationof vacutnn, Heating tape is coiled around the tilfation apparatus. ' 4.3.2 Power supply, direct current,at U-tube Connecting the two flasks. least at 30 volts. ..._ 4.3 Freezer, floor-model, large enough 5. Reagents c, Now- to hold tit rows of five electrolysis cells.' 5.1' Scintillator, Inst4e1 (Packnrd Instru- 4.3.Exhaust lines, to vent the explosive Ment Co.)for low-temperature counting mixture of ang hydrogen gener ed (1°-4°71: A preblended gel-forming scintil- in electrolyqis. latordesignated-, 3A70*(Research Prod- I if uctsInternational)for room-temperature counting. 5,2 Sodium peroxide, reagent-grade. 5.3. Tritium standard soligio Appropri- atetan ards are prared,b dilution of NBS sndard tated water with "dead" water, at is, water containing less than 1 Tu.. r 5.4 Water, "dead": The tritium blank in- troduCed by reagents and leakage during electrolysis must be tested .at. inte vals by analyzing "dead" water(water.ith no measurable tritium content), in e actly the same procedure as for a' normal w ter sam- 500m1 SAMPLE RESERVOIR ple. It is very difficult to confirm th t a water 100m1 CELL BODY ,is truly "dead,!' and'it isusually nscary to ELECTRODES SEARATED make`the assumption that water from a deep BY TEFLON SPACERS.. well in acconfined aquifer a hundred kilome7 , LE`AV IN is wines ters or, more from'9 the recharge area TEFLON SPACERS "dead." This assumption canbe correct only CONNECTOR FOR GAS if the well is pumped sufficiently to expel all EXHAUST TUBE AND Meteoric water that may have entered the_ ELECTRICAL ENTRY well and surrounding aqUifer by leakage.

6. Procedure- 6..1 Elroly&is. (In electrolysis and all other,ste at-dried glassware is used.) 6.1.1 till 55-ml volume of water sam- ple in the vacuum-distillation apparatus. The s Figure 8.Ostlund electrolysis cell. unit is evacuated before use, and the Water.,,/. I

d., 76 TECHNIQUES OF MATER-RESOURCESINVESTIGATIONS sample isprotectitrf)romatmospheric mois- tionapparatus and apply vacuum. The 44. ture during distillation. Distill to dryness. sample first bubbles to release trapped gases Recoyery is usually slightly less than the and then freezes. - `Apply a heat lamp or heat original volume bebause of water of hydra- gun to distill the -ample into the liquid- tion remaining in the salts reAidue,and drop- .nitrogen-cooled receiving bulb. neigh the- lets on the walls of the apparatus. The triti- bulb after completion of distillation to deter- um fractionation attributable to nondistilled mine the volumeofthe watersiniple water is insignificant: collected. weir 6.1.2 Transfer the distillate a clean 6.2 Counting. and dry. Ostlund electrolysis Cell (fig. 8), add 6:2..1 Pipet 8.00 mr of the distillate from 0.75,g of sodiurniperoXide, add '50 ml of the the preceding step into a 25-1-r1 polyethylene `distilled-water4ample, and stop pk the cell. vial, alid add 14 iinl of scintillator mix. The An argon atmosphere is maintained in the chte of 'scintilrator' depends an` the type of reservoir to eliminatecontact with atmos- liquid scintillation spectrometer to be used pheric moisture. 0 for counting. Instagel is used with the instru- 6.L3 Prepare a blank sample .("dead", ments that operate, at cold _temperature water) foroelectrolysis using the above pro- (3°C) and 3A70* is used with the instru- cedure. Prepare a standard' for electrolysis ments that operate at room temperature. Cap (200 Tu is .a convenient concentration range) tee vial. and mix. Heat the Insta.gel-samPle using the above procedure. mixture on ahotplate at approximately 6.1.4 Set up one blank, one staard, 100°C for 2 or 3-min. This clarifies the mix- and four samples in series in the electrosis ture.. The 3A70*-sample mixture does not bath. rger number of samples m be require heating. The above operation is car- usedf sufficient voltage is availablerom ried out under subdued red light to filter out theectrolysis power supply. The trit m the blue region.,of the spectrum. This mini- enric ment for one group of samples is dete mizes excitation of fluorescence background mined the enrichment of the standard in in the sample. seriesith the group. 6. .2 Prepare three blanks d two 6.1.Proceed isLith/the electrolysis after standds in the same manner as tp sam- samples have been Pooled in the coj chest. ples.lace one standard in the 2counting' The temperature ofthe ethylene glycol- water, position in the spectrometer and one in the ks,c a t bath is maintained at 0°C toughout 10th position.Place blanksatintervals.: thprocess. Electrolysis' from 50 ml to ap- throughout thgrun of 10-14 s les. pro 'irately 10 ml using, 4-ampere urrent, 6.2.3 Pla e three sealed stan ards (fri- 6.1.6 Neutralize the highly caustic solu- ated toluene igps-sealed s 'ntil ator solu- .tion in the cells to, pehPiit full recovery of tri- tion) in theoup. One sten does in the tium and to avoid mechanical and ,corrosionlfirst counti position to pe i monitoring .problems in subsequent steps. Disconnect a the instru pnt befdre counting the samples..' .cell froth the electrolysis line, and while pro- The r ing sealed standards are placed tecting from the atmosphere insert a dis- near the, blanks. posable pipet through the hole in the Teflori - 6.2.4 Allow prepared samples to remain. spa .Bubble,carbOn dioxide through slow in the dark in the liguid scintillation spec- ly. ut-a min and 1 liter of carb n dioxide trometer for several hours before counting are required tocomplete 'lentization. A begins. This allows decay of fluorescence and precipitate of sodium carbonate orms. chemiluminescence. A ruininnkm oft .8 -hr 6.1.7 Distill the neutra sample into standing is required with Instagel and 12 a "small tared Pyrex bulb usinvacuum -dis- hours' with 3A70*. I tillation apparattiskT e flainple" iscooled (but 6:2.5' Colinf ealkhustAkfive times for 100 not frozen) in liquid_nitrogen. Attach the Min.' Total counting time for One ample is still-liquid sample to the inlet of the distilla- 500'

11: METHODS FOR DETERMINATION OFRADIOACTIVE SUBSTANCES 77 6.2.7 Program the\ instrument to 1!.er- E- (2) form the external- standard ratio analysis on an (e-m.) samples, standards, And ,blanks at th4" end of where the counting run (see instrumeni,nstruc- tion manual). This procedure is a check for c,, = averagecountrateofstandard quenching. The ratio of low-energy counts in (cpm) corrected for background channel A of the spectrometer is established and blank, for both tritium and an external standard d--= disintegrationrateofstandard placed near the sample vial. The value of R (dpm), 'corrected for blank (S n the folloWing equation should be constant -B), To within .±0.2. .A.-= decay constant of tritium(4.685 x10-3 month-9, Counts inA. R tritium] t= elapsed time between certification of Counin B the standard and tirrie of count-in Counts in B same units as A, Counts in A'standard]. where Individual samples that falloutside this g= movingaveragecountrate range must be reanalyzed. If all values of R (cpm) of the standards, and fall outside this range, the scintillator has B =Movingaveragecountrate deteriorated and must be replaced. (cpm) of the blanks. 7.2 Calculation of tritium concentration : 7. Calculations - Use cation 1. The chemical recovery factor Several statistical schemes have been pre- (f) an enrichment factor When electrolytic sented for the and verification of enrichment is applied to the sample. tritium ate.; each intended to optimize a par- 1,000E -- ticular "analytical 'situation. In the present p(Stritium/1- (1) analytical procedure the repeated counting KVE f (e-A1) of individual swops has the effect of aver- where f is electrolytic enrichment factor de- aging out short -term fluctuations. Statistical termined-by standard included in the run, checks have shown that highest precision, in cpm/m1 after electrolysis this analytical situation, is attained by the fcpm/ml before electrolysis' use of longer term averake valdes fc*the 7.3 Conversion of tritium concentration samples and standards. . pCi/1 to"tium units: Counting efficiency and background values pCitrItium/I are detertninV with tritium standards when- Tritium 'conntration-in Tu.- jiver. a new. lot of scintillator is used. Count- 3.22 ng-efficiencyrdataand background data from 8. Report standards and blanks run with each set are )Concentrations in both tritium units and so determined. The new data from each set picocuries per liter are reported to tv(o sig- are averaged into to data from the preced- nificant figures down to the minimum detec- ing sets, ,thus creating a mlevir average'-tien level (MDL). The latter can only be vAlue for counting efficiency and bWkground. estimated because of the very pronounced As new efficiency and background data ap- effect of altitude on the background count. pear they displace older data entered into the At 5,000 ft (1,500,m) it is estimated at 25 Tu moving average. Data from four or five valid for the liquid scintillation counting of an runs (no quen0fing Or other aberration) electrplytically enriched sample. , ter, into the moving average used atny 9. Precision given time. .o 7.1 Trititim efficiency factor(E). Use ision is dependent on altitude in the equation 2: same w as MDL. At 500 Tu reproducibility t 9 78 TECHNIQUES OF WATER-RESOURCES 1NVESTIATIO/1S is approximately ±20 percent. precision lm- Ostlund, H. G., Werner, 0. E., 1962, The elec- proves with increasing concentration andis trolytic en chment, of tritium and deuterium for improved by etectrolytic concentration of natural tritium measurements, in Tritiur?f the samples with lower tritium concentration. physicalandbiologicalsciences,Symposium Reproducibility for samples enriched by Proceedings (STI/PUB/39) IAEA, Vienna, p. electrolysis is, limited by the reproducibility 95-104. of electrolysis (approximately ±3 percent): Schroder, L. J., 1971, Determination, of tritium in water by the U.S. teblogical Survey, Denver, - References Colo.: 10. Geol. Survey Rept. USGS-474-134, Kaufmann,'S.,Iand Libby, W. F., 1954, The natural distribution of,4tr ium, Physical Review, v. 93, 22 p.; Avail. only from U.S. DeptCommerce, p. 1337-1'344. Natl. Tech. Inf. Servcce, Springfield, VA 22151.

4

L Tritium Electrolytic- enrichmentliquid scintillation method, Reston lob. (R- 1174 -76)

Paraineters and codes: Tritium, dissolved(pCi 1): 07005

Tritium, in water molecules (Tu): 07012 c

1. Application and soft iron electrodes. (See fig.. 8, The limit of detection of tritium the -method R-:1172-76, for'diagram of electroly- , liquidscintillationcounting method(R- sis cell.) During operation, the cells are kept .--1173-76) is about 60 Tu (190 pCi/ly...Many at 0°-1°C to. improve 'electrolytic tritium .re- l'Eurface'-water itnd most ground-water sam- covery and to minizel loss of sample ,by ples., contain less than 60 iii; -and cannot be evrapovfition. A maxiMuic of 100 ml is elec- analyzed directly'. Concentfation t>f the trifti-_ trblYzed in the cell. If larger samples are to um in low-tritium samples by electrolysis be- be .electrolyzed, the sample is periodically fore counting by liquid scintillation permi ded to the, cell frOm.the reservbir as elec- /the analysis of watef'scontaining a_ s little trolysis proceeds: :1°Tu (3 pCi/1). Electrolysis proceeds at 6 amperes until less than 25 ml remains. Then the current is, reduced in ps to-as low as one-half ampere, , 2. Summary of method as the remai ng.volumedecreases to the de-. . When water is decompoijed to and 02 sire5-ml final volunie. Electrolysii from a gas by ,electrolysis theris a strong isotope star 'rig volume f 00 ml requires about 4 d. fractionationeffectwhichresults in the Fo lowing elecolysis, the. sample water is heier sotopesisotopes (tritiluin particular) lte- separated from the electrolyte by vacuum ; i concentrated in the remainingquid' distillation and is thenTeddy to be counted. phase. Under the proper con'ons, r overy Electrolysis, is performed in sets4cells of More than 70 percent of the initiv.1 tritiurrP connected in series to a constant voltage,"cur- ispossible. Thus, if a sainpleis reduced from rent-limitin 500 ml to 5 ml by electrolysis, the---triiiunti i electrolyzis standard, a blank, ,ans_17,f the rasidual-fkml will have been concentrated 4jto--111, sam es. .

500 x0'.7 _ by at least: 70 timeas,When sych 3. 'Itnth Sainpl stilled before and after elec- an electrolyzed sample is counted using the trolysis, 41..are thoroughly gas-stripped by procedure...described in method R-1173-76, the H, and 02 produced during the'electroly: tritium level as ldw as 1 Tu can be detect d. sis itself. Thus all potential interfering sub- A'he electroly,sis procedure used is esn- stancesare effectif,ely removed,Ind no radio- tially that described by Ostlund and Werner,.active or other interfei.entes'reniain in the (1962). The sample, after distillation,is -sample ready for counting.

made basic with Vadif or NaO2., andr.elec- Tho.rna or interference with low-level tri- Ji_y trolyzed in glms cells (Ostlund cells) with tkum' ari0 liCiontamination by tritium-% it- F 79

.r 4. 80" TECHNIQUES OF WATER-RESOURCESINVESTIGATIONS self. The electrOlyte may contain tritium, or method R- 1173 --76) is calculated using equa- the sample may pick up tritium during exces- tion 1: r sive exposure to the laboratory atmosphere. V° Vo-roh9), To minimize contamination, it is important Vfx Vf that sources of tritium above le4iqk naturally t present in the air 'be rigorous). xcluded where from the laboratccrytillese sOv 'inOlnsle 170.= volume of-sample pefore electrolysis, luminous watches an such high-tMin spsn- VIvolume of sample f011owing electrol- pies as may result from tracer tests. \ ysis, and Samples of "dead", water should be- run p= the separation factor. thilrgh the entire electrolysis and countinki. The elearolysis- standard with each set is o process as blanks to monitor contamination counted as if it were a sample and its tritium and to permit corrections to be made t,o,the content determined. Then : final. reported tritium content' (see section Tut below). JOIN Tuo 4.ApFiaratus Mere The apparatusqequired is the same as that =Tritiumcontent.ofelectrolysis described in method it7,1173-76 with the ad_ - standard after electrolysis, , dition of the following: Tuo = Tritiumcontent Oftelectrolysis ostlund electrylysis cells. (See fig. 8, meth- standard' before electr6lysis, and od R-1172776.) Lrd-=standard enrichment faiter( Vacuum-distillation apparatus,(1)for The standard enrichment factor' is- then predistillationi capable of handling volumes substituted for "c: in equation -1 And ,p is Up to 500 ml; and (2) tor distillation' after, calculatedifor the-set. electrolysis, capabld of handling from to 7.2 Calculation ofritium concentration: 10 ml. Calculate tritium: conntration in the sample -Freezer for cooling electrolysis cells. iii the manner descri ed in method R-1173 71, ti 5. Reagents As specified in, method R-1173-76 with 8. Report the ZidditionAgf the f011owing: Report as described in method R-1173-76. Electrolyte, NaOH or Na2O_. - Electrolysis standard, a tritium standard 9. Precision solutiOn Prepared as described in method There' are uncertainties in ech of-the' ,R-1173---76, sec. 5.2, and containing about 1 terms in equation 1 leasting to f. These are dpm/ml. the weighing err is in V° and VI, and-vatia-' s inthe eltrolysis proc:ess itself giving 6.ProCedurs e to variati ns 3n )3.- Eg3erienee suggests . :Performelectrolytic enr?ctinent as de- that the one tandard donation, error of Pj. scribed in sec. 2 above, the follow procedure joijf in equa ion 5, method11-1173'70) .is . desCrib&I iti.method R-11776. bout 5 perce t. Therere also erroral7itv)ewith the- 7. Calculations value'k'e blanwhich isucs correct for 7.1 gnrichment factor. The enrichment sam ntamtionby reagents and ex- factor, f, required to calculate the samplet posnre in the laboratorykidder favorable tium content 'from the count data(see conditioni, the error in the blank may bie-its

t,.

I METHODS FOR DETERMINATION OF RADIOACTIVE SLIBSTANCE . 81 small as ±0.02 Tu (ostlund and others, References 1974), In routine work, the error in the blank is taken as equal to the value of the Ostlund, H. G., and Werrte,r, E., 1962, The electrolytic blank correction- itselfusuak from 0.1 to enrichment of tritium and deuterium fo,ririfrtural ' tritium measurements: in Tritium,in he PhYsi- .,, 0.3 Tu. Thus, although itis sometimes possi: n c es ;jAternat. Atomic ble to count la sample to a precision o sr : ,ienna, V.I., p. 96-1/04. I. than 0.1 Tu, the real precision of routine1,,4 46;ffun,. . ., orsey, H. G,, and Roah, C. G., 1974,_ Geosecs North Atlantic radiocarbon and tritium ti-uth analyses is limited by the blank error to restilts'tEarth and Planet. Science Letters, v. ± 0.1 to ± 0.3 Tu. 23, p. 69-86.

r

.1

\.

r.

4 Urcknium, dissolved , Fluorometric methoddirect (R.71180-76)

Parameters and codes: Uranium, dissolved(Agin: 22703. Urania, dissolved '(pCi /I): 80010

s. 1. Application centration, quench-compensation . techniques may be used. When quenchingelements. are 'IThp-inethod is suitable for the determine:.present in rplatiyely high concentration, itis Mr:: ofuranium . innonsaline waters necessary to purify theuranium by extrac- 10,000 mg /j dissolved solids)....in which tion. This technique is described' as "Fluor°- florescence is quenched legs th 30 . .metric `meth6dextraction procedure" (R- Cent. Jf quenching exceeds 30 perce t, it 1181-76). . J tt use, the extraction m od. The letter Metkod is much more time con- Althdugh the fluorescence of. 14 sample isfr suming. Theeeforei, itis usual practice to directly proportional to the ura iunt ,00ncen-'" effects),,' it . apply the direct fluotimetric method as a first tration .(disregarding quenchin aconstant calibratiOn step unless previous analysth.otsamples from is not possible td" use --straigllt-line plot of fluorescence against con -. a-Particular area has 'slOwn.thak-the of .vEiriDtionin 1 centration. This is a result . approach is 'not possible. propertie; between batches of flux, Vanati,ons The minimuM detection limit variesk0tvith in the: fluxing temperature, possible surfpre the propities of the. sample, flux, andfiuori- oxidation during fluxing, And varistiOns;of . meter, butnorwAlly 0.3 4/1. uranium ipi,purity in different batches of,flux. The Above, effects are minimized by running . Summaryof methOd uranium standarags'vtrith each set of,sampfes The fluOrimetric. -method of determining so that a new 'ctdibretionof concentration ,,arAnium is among the most, sensitive and seem ihst fluorescence is made underthe condi-. clfie ofenalytical methods. The intense fluor- fis existing for-Wiz set of 4nalyses.. escence of urerlium i. when fused in a sodium The indteriels used for the preparation of "fluoride-sodium carberiate-potassium carbon- the flux alWays,,,contain a small amount of ate flux'is utiiiied to determinequantit4ive-, uraiium. Fluorescence_from this source pips ly the amount of uranium present in 'the reflected light not absorbed by the filters irr . sample. In its simplest form theanalysis is. the fluorimeters Make up the "blank.The the carried oNt .by using a dry 'residue of fluorescence comPonent,fof theblaAk is sub- 6'aporathd-water sani2le in fluoride-carbon- 'while .the reflectance corn -.. ate flux, alkiltripg thimio solidify into asmall ject to quenching d determining the fluorescence under.ponent. isnot. The blank for a highly ;disk, quenched sample is, therefore, lets than the-,, u..;,6f. et light in areflection-tybe ffuorimel blank for Asample .40Kith.relativelyrow. ter. miuM-copper, manganese; and D. ,.r. feik other elements-in water quench the flUor- quenching. A' graphi Method ''of coper17rn essrcein- _varyingdegrees Whentbe sating for this effect o e blank 'velue.was 'quenching.elements are in relatively lew con-developed by Thatcher and BArker (1957) :

! to ti8

tJ 84 TECHNIQUES QF WATER-RESOURCES INVESTIGATIONS Niakine The following od is similar to that ;described in Water-Supply Paper 1696Cv (Barker and others, 1965) for the determine% iiof uranium in norisaline water.

pe/r .N-4- Direct spectral interferencels not al) lem In the fltidrimeiric method. Cadm fluoresces in highcarbonate,flux disks at ep- proxicnately tire same *avelength as,uranium .,.,(Boomen andItein, 1962; p. 102), but inter- ference from this source is unlikely in most natural waters. High concentrations of -salt cause difficulty in the preparation of the flux disks. The quenching effect of transition metals has been cited above.'

4. Apparatus 4.1 Crucible tongs, platinum tipped for holding hOtplatinum dishes. 4.2 F'luorimeter. A reflection-type instru- ment pf high sensitivity equipped with a sample carriage to accept small disk- shaped ,so'lid- samples is reqiiired. The sample cavity should be 4pproximAtely 35 mm in diameter and 5-miri deeps InstriictionsAerein,pertain )V-41i,,E6TATING SAMPLE TABLE to the 'Jarrell -Ash Model 26L:600 instrument, but any fluorimeter that fulfills the above re-; Nt -r .4( suirements-may be used. c.; 44; 1.4 QUARTZ RODS ,TO 'HOLD 4.3 Fusion, aPparatus. The rotary.'fusiii PLATINUM DISHES' machine develoPgd by .Stevens and -othe a. (1959) and modified by Barker 'and .other's (1965) is used (fig,. 9). A rotating sample G BURNER carr e is mounted above a ring of burners. and slowly revolved during the Osion to ass re that each-sample receives Ole super' SHEET METAL HOUSING hen ing. The samples are contained in .plati- nil fusion dishes resting on .quartz rods: The fusion. unit' is tilted aPProxiniately 30° E AR ED MOtOR during 'part.ofthe fusion so thakinolten 'washes the sided Of the fusion dishes to sweep doWn agy sample residue that may' adhere F LEVER FOR 'INCLINING 4 The design of the burner must be adapted to BURNER 20° local gas 'composition and pressure to obtain Figure 9.Stevensranparatus for fusion and mixing the e7optimiim temperature. of sample and flux in uranium, determination.i 4.4:Fusion dishes.he 'dishes .arejlabri-- eked of platinum to a shallow:dish .shape ty). compatible with adequate thickness for that provided maximum exposure of seinplestrength (fig..10).,Therothiding of the 'bot- disk surface (for. high fluorescence tail. fietthits easy removal of the4lidified METHODS FORDETERMINATION OF RADIOACTIVE SUBSTANCES 85

'3 Smrn mm 5.4 Sodium fluoride 'solution, 1 m1=0.01 g NaF: Dissolfe0 g of dry sodium fluoride in distilled watet and dilute to 1,000ml. 5.5 Uranium standard solutionI,1 ml =100 pg U: Dissolve 0.1773 g of reagent- grade* uranyl acetate dihydrate in approxi- mately 500 ml of distilled water. Add la ml of concentrated nitric acid and dilute to 1,000; ml -in a volumetric flask. Store in a- Teflon bottle. 5,6. Uranium standard solution 'II',1 ml =1.00 pg U: Dilute 10.0 ml of uranium standard solution I to 1,004 ml with distilled 3 5mm water. Store in a Teflon bottle. 1 DEPTH AT RIM 10mm' 5.7 Flux: Using anhydrous powdered re- DEPTH -AT CENTER 12mm agent-grade chemicals, weigh out 910 g of Figure -10.Platinum dish for use. inStevens ap-, Na2C0 910 g of KX03, and 180 g of NaF, paratus.. and rough-mix in the glass-jar mill using a large porcelain spatula, or Lucite rod. Add the small Lucite rods, stopper tightly with a flux disk. An identifying number is stamped on the into the lip of each dish. polyethylene supper, place thejar mechanical rollers, and dry-mix overnight: 4.5 Infrared drying lamps ."Dual 250-watt infrared drying lamps in a protective metal shield are moun on a ringstand for vari- 6. Procedure able heat adjustment. 6.1 Determination of flux constants : It is of re- 4.6 Micropipet, 50-0 capacity, Eppendorf necesary to determine r (the fraction flected light in the blank) and f (the fraction type, foraddjtion of uranium standard. . wafluorescent light in the 'blank) for each 4.7 Mil/. ''"A. 5- to 6-liter Pyrex glass-jar tch of flux. These :Tux constants" are used mill _containing 15 cm by 2.5: cm cylindrical for all analyses made with the given hateh of Lucite rods is used'to mix the flux. flux. Two calibration curves are prepared as 4.8 Pipeti, volumetric 1-, 2-, 3-, 4-, 5-, 6- shown in figure 11. The calibration°curve X and letornl. is prepared with pure uranium solutions And 4.9 Polyethylene jarst wide-mouth, 4-liter the 'calibration'. curve Y is prepired with screw-capped, for storing flux. nianium solutionscontaining a constant mount of quenehing agent, The two guryes 4.Reagents intersect '(P) at a negative uranium ciiinceb- 5.1Chromlium solution, 1. m1=30 pg Cr: .tration. The intersection of the curve X with Dissolve 0.085 g of X2Cr207 in (*tilledwater 'the fluorescence axis is point ,A, the un- and dilute to 1,000 ml. Wei ht and volume .quenched blank. The intersection ? of X' and -meigurkents,nteed-ndt be etEt.,:. Y is pointB,the reflected light. The fraction 5.2 Copper solution, .1 mi=60,'/.4 Uu: Dis- of. reflected' lighWs BA and the fraction solve-:4.236 g of 'CuSe4.51120 in, distilled of fluorescent IiiOn Iffe' blank reading is water and dilute' to 1,000 nil.Weight and 1r. - -volume measurements need not be exact. -The proCeddre is 'as follows ; 6.1.1 .Measure 1 'ml of sodium fluoride 5.3 lifanganese solution:1 ml = 20 pg Mn : t Dissolve 0.081.g of. MnSO4.51120 in distilled ?solution and' the follring volumes of urani- water and. dilute 'to, 1,000 ml. Weight and um.st4Idard Solution II (microburet) into 'Volume measurements need not be exact. platinum' fusion dishes. 86 TECHNIQUES OFWATEri.RESOURCES INVESTIGATIONS

solution 11 . Dishes (ml) turn the table to the leve ,position,, and con-

1 and2 0.000 . tinue heating the melt /for an -'additional 3 3 and4' .020 min at the same temperature. 5 and6 .040 6.1.6 Turn the heat controLto the inter- 7 ,and8 .060 9 and ,>10 .080 mediate setting and heat'''at this tempera- tare for;3.min. 6.1.7 Turn to the low setting and heat a z for 3 min. Turn off the burner and alloW the Q60 diShes to cool for' 8 min with the fusion table still rotating. Finally, place theadishes in a desiccator, and cool for at least 30 min before measuring fluorescence. Lij40 6.1.8 Measurement of fluorescence: The 2 following instructions apply to the Jarrel- 0 Ash fluorimeter. Modify if other lluorimeters 11- 20 are used. Allow the instrument to warm up 30 min before use. 6.1.9 Set the fluorimeter reading to zeroo- using the zero-adjustment knob.' Push the empty sample tray all .the Ray in,".depress r.02.04:0608.10 he,X.01 key.;dnd adjust to zero using the URANIUM CONCENTRATION (09) screw adjustment. Re hove the blank flux X-FLUORESCENCE(UNQUENCHED). disk from the platinum dish by -inverting it Y-PLUORcSCENCE (QUENCHED) on a clean piece of ,paper. Place the disk in A-FLUORESCENCE BLANK (UNQUENCHED e fluorimeter tray and push into measures PLUS REFLECTED' LIGHT) ment position. Depress the X.1 key and ad- B:REPItECTED LIGHT P- INTERSECTION4:-POINT' just: the sensitivity só that a, reading.of 10 (oh'a scale of 100) is ol4ined for the blank. Figure 11.Uranium calibration curve. 6.1.10 Remove the blank disk and re- 6.1:2 Ti3 the even-numbered dishes, add check the zero .setting." Use a soft-bristle, 1 ml of ,solution. brusktO remove any particles sloUghed into 6.1.3 Evaporate the solutions to dryness the sample tray from the preceding disk. If uhder the infrared lamps. Do not 'permit the the zero needs readjustment, repeat step - 8amples to bake as this can result in loss of 6.1.9 until the empty holder reading. is zero uranium, although the sodium fluoride ad- when the blank reading is 10. The "fluores- ded as the first step minimizes loss by over- cence" reading of the empty holder is minim- heating. izedby painting ,with a colloidal grathite 6.1.4 Fusion procedure u: To each of the mixture such as Aqua-dag. This must ,dry dishes 'add 2 g of the flux cernixture. Spread before. use. Repainting is required at inter- and bank. the' flux with a glass rod so that4.1s. ' any solids on the vertical walls of the dishes 6.1.11 Readthefluorescenceofthe wilt be covered. standard and Oarnple disks ugng the X.1 6,.1.5,,Place the dishes on the ',rotating scale, if possible or X1 and X10 scales if table of the Stevens fusion apparatus, And needed. incline it by, operating the positioning lever. 6,1.r2 Plot the fluorescence of the disks Ignite the .hurner ring, ad,iust to maximum as a Junction df the weight of'uranium (fig. heat; 'and. heat the dishes until' the flux is 11) : Draw the; best straight- line13 X and Y completeIlunelted.,This re-quires about 5 min. through the 'sets'of points for the quenched Allow the fusion table to, rotate in the in- and 'utiquenched-disks. Determine B, A, and

cjined".position for 'an additional 2'min. Re- r and, f as above. , METHODS FOR DETERMINATION OF RADIOACTIVE SUBSTANCES 87 6.1.13 Repeat the calibration substitut- 7.2 Calculation of the corrected blank ing1 ml of manganese 'solution for the value Nr each sample: The blank value to chromium solution. be used with an individual watersample 6.1.14 Repeat the calibration substitut-, must be somewhat less than the blank Meas- ing--aml of copper solution for thechromium ured instrumentally on the pure' sodium solu ion. fluoride-sodium carbonate disk because, of 6.1.1.5 Average the values of r and f quenching in the water, sample of that por- determined for the three quenching elements tion of the blank value contributed by uran- as above. These mean values of r and f,,are ium impurity fa the flux. Since a blank that used for all analyses using this batch-of flux. represents conditions inothe sample cannot 6.2 Analysis of the water sample. be ti'repared, it is necessary to calculate the 6.2.1 Four samples may be analyzed blank value Nor' each sample on the basis^ simultaneously using .the Stevens fusion ap- of the blank measured for the disk of pure pa.ratil\s_ with 20 positions for samples, when .fluoride-casponate flux. The e:kntribution of analyses are run in duplicate. One milliliter. reflected light to the blank is- assumed to be: of sodium fluoride solution is added tofthe "the same for the sample disks and the pure 20 platinum dishe's. Two dishes .serv4 as flux disk. The calculation is simply:r, blanks. Stalfaaratranium (0,06 pg). is added B« B = (420!) + (7.13,),s to each of two dishes. Four 7'- aliquots of each sample are pipetted into four. dishes. where 41,04 Standard uranium (0.06 p.g) Js added to two B,="sample blank. of them. 'kip Bf 7:blank Obtained. with disk of pure 6.2.2. Proceed with the analysis as Pity flux, t. steps 6.1.3 through 6.1.11 above. ffra.ction. of fluorescent light for *-the batch of fliti"usea; 7: talculations r=fraction of reflected light for the 7.1 Determine the' quenching f?ctor; Q, batch of flux used; and for each sample filen the equation: Q is defined ineg,tion-7.1. Q_DA - C-oncentration--of IfraniUmin,the. C B .11 Sample: This is Calauliated using equatron.: where S .A 133 1,00(t ;ratio- ofuraniumfluorescence g/1 of U= under quenching contlitions to Ain Q II V the fluorescence under noquench, where for a given. sample, S=mierograms.04A ofuraniumin -the , A = niea.n" fluorimeter reading of unz- standard, and spiked, samples, V =sample 'volume in ml and the other -Q., B= mean fluoeter,reading of blank terms are as defined In Sections. 7.1 and 7.2. t C= mean frtiorimeter reading stand- If it is known from previous.experierice arA disks, . , with . water from a particular source that D = mean fluorimeter reading ,,of sam- the quenching factor Q is always greater:\,,;i1 plediskscontaining uranium 0.7 (quenching less thari 30. percent); Ispike it' becomes possible to omits the determina- ,;11,=fliiorescence increment of Spiked tion of Q and combine equations under..V. sample, ancl and 7.3 tcr obtain the following aimplifiedr an= fluorescence of the standard.. expression:. Note that the equation appii?e'SonlYfwiien S(A the amount of 'uranium spike It' the sample .g/1t, of U is equal to uranium in the sta.ftdard. of. V X88 TECHNIQUES OF WATER-RESOURCESINVESTIGATIONS am &Aron alyzed with a relatively pure flux, and as Report concentrations less than 1.0 pg/1 high as, 0.5 pg/I when a highly quenched to one significant figure. Above 1.0 pg/I, re- sample is analyzed with a flux having rela- port two significant figures. Occasionally the tively high uranium impurity. Under aver- radioactivity is reported in pCi/l. The con- age conditions the MDL is 0.3 µg /l. version factor is 1 pg=0.33 pCi when only the radioactivity of uranium -238iscon Referencii sidered. Natural uranium contains 0.72 per- Barker, F. B:, Johnson, J. 0., Edwards, K. W., and cent of uranium -235, and normally uranium- Robinson, D. P., 1966, Determination of uranium.-- ' 238 is considered to be in equilibrium with in 'natural waters:U.S. Geol. Survey Water- an equal Activity of uranium -234. The can- Supply Paper 1696C, 25 p. Booman, G. L:, and Rein, J. E., 1962, Uranium in version factor is1pg.-- 0.68 pCi when all Kolthoff, I. M., and Elving, P. J., eds., Treatise three isotopesisotopes are inchided. on anitjytieal chemistry;pt.2 of Analytical chernistrylof the eleinesits, sec. A. Systematic 9. Precision analytiekl 'chemistry of the .elements: New York, - Interscir Pbblishers, v. 9, p. 1-48W .- Precision is. Vvoximate y ±MDL or ±15 Stevens, R. E., Wood, W. H., -Goetz, ,and peicent, whiclievef4s larger. The MDL is a Hod e A 1959,t Miefline forp phoe- function of quekching, fluorescence intensity phol,s-for the fluorimetric determination of uran- ium : 'Aiiiti,ch4nistry4 v. 31,.p: 962 -964. of the- flux, and uranium impurity in the -.Thatcher, Barker, Fe...B., 107, Determii1-7 flux. It may be as low as 0.1 pg/1 with a tibn of uranium it natural iyaters: Anal. Chem sample ,having no significant quenching an- try, v. 29, p.',157571578...... =;

4 Uranium, dissolved Fluorometric methodextraction procedure (R-1181-76)

Parametersand codes: Uranium, dissolved(Ag/1): 80020 Uranium, dissolved(pCi /I): 80015

t1. Application 3. Interferodlits The method is _applied to water samples All interferences in .riatural waters are where the reduction of uranium fluorescence.,removed by the separation steps agOehave no" by quenching exceeds 30 percent (as deter! effect. The 'method has not, howeVer, been Minedin"Fludrometric methoddirect" extensively tested with industrial wastes, (R-1180-76)), the concentrationof. total- mine waters, and other Waters that may'have dissolved solids exceeds approximately 10,000 unusuallyhighconcentrationsof heavy mg/1, or a minimum detectionlevel rower metals. When such waters are encountered it than 0.3 pg/1 is desired. is advisable to Pun a sRiked sample contain- ing a known increment of uranium through I 2. Summary of method the analytical procedure to test for possible Uranium is.separated from-quenching ele- residual quenching. A quenching correction men* and excessive salt concentrations in a can then be made as in "Fluorometricmeth- twoXtep separation procedure- developed by oddirect" (R-1180-76) based. on thy-per- Smith and Grimaldi (1954). Uranium is co- centage of reduction of the ekpected fluores- precipitated, as uranyl phoopht

7 1 It 90 TECHNIQUS WATER-RESOURCES INVESTIGATIONS

.;.. 5;,. Reagents through steps6.11 through 6.19 of this procedure.' 5.1Aluminum nitrate solution,-,0.2 M: . DisSolve 15 g Al (NO,).9H.,0 in distilled wa- 6.2.Add 3 ml of concentrated HNO,, 1 ml of 0.2 M aluminum nitrate reagent, and 5 ter and dilute to 200 ml. _ 5.2Ammonium 4droxide, concentrated. ml of 0.090 M diammanium-hydrogen phos- 5.3Aminonlum nitrate solution,1 ml phate reagent:Heat to boiling to re-move car- =101Ing NH,NO, : Dissolve '10 g of reagent- bon dioxide. grade ammojuiumium nitrate in d Stilled water 6.3Add a few drops of methyl red indi- cator, and neutralize just to the yellow end- and dilute to .1,000 ml. -. . point by dropwise additions of concentrated . .5.4e Diandnoniumhydro enphosphate solution, 0.090 M: Dissolve .12 g of (NH,), ammonium hydroxide with constant stirring. HPO, in distilled water and dilute to '1,00 If, on addition of the indicator, a pink color nil. forms and thendisajpears,the water proba- . !,.., bly contains an excessive amount of iodide or 5.5Ethyl ether. Gromide ions. In that/event, add ammonium .5.6Magnesium nitrate reagent, 5.0 N in hydroxide; 2 or 3 drops att a time; the& add a Mg (N0.,)a0.5 N in HN O., : Dissolve 640 g of drop of indicator. Repeat his procedure until Mg (NO0761420 in the minimum volume of the indicator exhibits the yellow color. in- hot distilled water in a 1-litre beaker. Pour stantly upon hitting the solution. into a 1,000-ml volumetric flask, add 32 ml of 6.4Digbst the precipite near the boil- . concentrated HNO3, ,dilu e o volume, cool-to ing point on a hotplate oil steam bath for 30 room temperature,a dagaindilUteto min ; then allow to cool to room temperature volume. "-`,.. and settle. %e - 5.7Methyl red i dicator solution: Dis- 6.5Using a small pipet connected to an csolve 0.1 g of methyl red (dimethylaminoazo- aspirator, draw off as much of the super- benze-necarboxylic acid) in 250 ml of 60 per - nate' aspossible without disturbing 'the ent ethanol. . -:-,,. precipitate. 5,8Nitric acii4 concentrated. it 6.6Transfer the precipitate to a 40- or 5.9Urcaqirm standard ,solution LH. ml 50-ml screw-cap Pyrex centrifuge tube. Po- =100 1,g U: ge method -R- 1180 -76. lice the beaker and the stirring rod with r 5:10 Uranium standard solution II, 1 m1 ,percent ammonium. nitrate ,solution, adding the washings to the centrifuge tube. ,Centri- =1.0 ,ug I.J: See method R-1180-76. -- fyge, discard the supernate, and add 4 or 5 . 5.11 Uranium'standard solution,111,.1 ml ml of the 1-percent ammonium laitrate solu- =0.01 ttg U': Pipet. 10 ml of uranium stand- tion. Agitate the mixture in the tube. to wash a'rd solution 'II and 5.;m1 of concentrated" the precipitate, ana again centrAuge, and dis- HNO., into a I,O00 ml vOlymetric flask, and card the supernate. Note: In transferring the dilute to .volume with distilled 'water. Mix precipitate to the centrifuge'tube it will prob- thorlughly; and sto in a Teflon bottle. ably be necessary to centrifuge and &cant onbefofe the transfer can be completed. 6. Procedure . . . . 6.7Qvendry the precipitate in the cen- ' . . 6.1,PlaC651;06-Inl :aliquots of tte Filtered trifuge tube for 15-20 minutes-at 80°C. Raise samples in .600=ml beakers. .Prepare two oven temperature-,to approximately 100"C standardtvby .addition of 8.0 ml of uranium and take tp complete dryness. standard solution III' to 400 'ml of distilled ,6.8'Add 8 ml of the Mg(NO.), reagent, water in 60Q -ml beakers.. Also :prepare a and warm gently to dissolve the precipitate. blank of 400 ml of di8tilled water. An addi- Usetheultrasonicgeneratortospeed' tional blank and staulard (prepared by pi- dissoluti6fi. petting 50p1 off-traniutn standard soluliod II . 6.9When cool, add 10:m.l of cold ethyl,4 directly into the platinum dish) are taken ether to, the test tube, cap, aud,hgiraie vs e 0.

1 METHODS FOR DETERMINATION OFRADIOACTIVE SUBST4NCES *. 91. 1,000 S (A -43)R,, .ously for at least 2 min. Allow about 15 min ktg/1 of U- . for the two layers to separate. vccm R, 6.10 Piper off 5.0 ml of the ethyl ether whdre layer using a 5-ml pipet with a control, and ';S=Itg of uranium added to prepare the place in a 125-m1 Teflon dish to which ap- standards, proximately 8 dropsof 'water have been A -mean fluorimeter reading of the added. Add another 5 ml of ether to the tube, sample disks, cap, and agitate for 2 min. Again, allow 15 B--= mean fluoririieter reading of the min forthe layers to separate, then pipet an blank disks, additional 5 nil of the ethyl ether layer from C= mea fluorimeter'readingof the the tube into the same Teflon dish. Use the sndard disks, ultrasonic generator to break up emulsions. e of the sample in milliliters, The equivalent volume transferred is thus V --- Volu . Te = fractional recovery of uranium ex- ml of the Original 10 ml of ether added. tracted from the sample, and 6.11 Allow the ethyl ether to evaporate 1? = fractional recovery of uranium ex- :completely in a fume hood at Korn tempera- traded-from the standard. .4ture. t gently on ahotplate to complete dryness., The fraction of uranium recovered in seri- 6:1 Transfertbe`Aample from the Teflon al extraction of the samples and standards evaporating .dish to the platinum dish used (R,, R) is determined by equation : forfusion with a, small portion of ethyl arc4- v, v, vl vl hol, policing the bottorh and the sides of the V, V, V, V, V, Teflon dish thoroughly with A small rubber policeman: Repeat the ethyl alcohol wash one more time. A third wash must be completed where using a small portion of distilled water. Com- bine with the ethyl alcohol washes immedi- v = volume of ether (ml) removed after ately. The three wAhes must be kept small each, extraction, and enough so the combined washes do not exceed VA--Volumi of ether (m1) in the sample AN- volume Of the platinum fusio dish. for each extraction. (Here again the distilled water wasserves When V is equal to 10 ml and v is a double purpose:('1)'assuresc plete to 5 ml (normal procedure) the I?' values transfer of the sample, and (;ot reduce the for the. first, second, third, ,acrd'. fourth ex- 1 ethyl alcohol.creep up the sides of the fusio tractions are respectively 0.5,.0.75, 0.875, 'dish.) Take fusion dish to dryness under a and 0.937.411 heft: lamp. '! ° When the sefiextraction of* the sample 6.13 Carefully flame fusion dish over is identito t serial extraction of b' rner until thf dish is a dull red. ', standar sam ber of eoitractiorip using 6.14 Add 2 g of flux and prepare 'fluores- the same v es)' the 'filiatonal recoveries cent disk as in method R-11,80-76. 6 .... cancel and the equation simplifies to : i 6.15 PlacF,the dishesi in "a desiccator, and 1,000 S (A B) pg/1 of U- 5 cool for at least 30 min. Determine the fluor- ., V (C-B) escence of the samples, blank,: and standard ''as im method R-1180-76. ;t 4. ,A, 8, Report . , , . . V' Report concentrationS to tWo significant 7. altulations 4' - figui'es above Q.10 lig/1 and to one significant Concentration ofuraniumistalculated figure -For values beloW 0.10 p. with 0.01 /..,g/1 as the minimum. from the.equatig.le *$ 4 .4! L.

*

* * 92 T E C H N I Q U E SOF WA4ER-RESOURCE kINV'ESTIGATIONS 9. P.rcision Raeiences Minimum detectable concentration isOn Barker, F. B., Johnson, J. 0., Edwards, K. W., and Robinson, B. P., 1965,,Deterininalion of Uranium pg/I.meprecision of the fluorescence meth- in natural waterbt: U.S. Geol. Survey Water-` ods, .for determinatiou of uranium is gov- Supply Paper 16941C, 25 p. IN. N., aid Wolfe,. NC J., 1952, Influence erned prima ;conditions_ inthe' flux and of various nitrates on the diethyl ether fictrac- in the fusion ii'ation. Reproducibility of Aion of low.. concentrations of uranium from thorium; in. Production and §eparation of Uran- the fluorescence from replicates standards ium -233 Katzin): U.S.. Atomic Energy averages ± 15 .percent. The same value is Comm. TI 1Wt23, pt. 1. Smith, A. P., aria. Grimaldi, F. S4 1954, The fluori- Used for preq4ion of sample runs except at metric determination of uranium in nonsaline concentrations below approximately0.07 and saline waters, in Collected papers on meth- ods of analysis for uranium and thorium: U.S. pg/1 where 1-MDL represents the precision. Geol. Survey BUIL 1006, p. 125-181.,

0

o '- O'f*. F la'

*

. 4 , Uranium, .dissolved,"igotapiratios tAa specqorneiry----Chetnical separ !ionit-1182-76)

'!.# 4 Parameter and code: Uranium, disiolved, isotoperatio(dimensionless): none assigned

1. Application Uranium-238; 4.195 MeV (0.77), 4.147 MeV (0.23) Uranium-235; 4,370 MeV (0.25, 4.354 MeV (0.35),:4. The method is applicable to most fresh- (with five other energy peaks of less intensity) water and saline waters. _Industrial wastes Uranium=234; 4.768 MeV (0,7 7MeV (0.28). and mine drainage may require special treat- Since snrface-barrier-Clef can be ob- ment. tained 0140.KeV (30 keV) (for 450itnjlici5ungng area), it 2. Summary of method is possible to Oeanly relve -illitthe uranium peaks of interest. The uranium isotopes 'are determined by Because of the very low tadioactivity of alpha spectrometry, after concentration and uranium, itay be necessary to collect the separation from the bulk of the water sarri-" uranium fro"a relatively large water sam- ple by use of the precipitationlextraction ple to yield. between 2.5 and 220 pg of uran- -.procedure described under method -R-1181 ,ium. Samples as lifrge. as 25- liters can be ..! 76 determination of.. uranium. This is fol- used. ) lowed by an ion-exchange procedure .to -elimi- nate thorium, an alpha-emitting .radionu- 3. interferences . clide. The final step is electrodepositiOn of . There is no direct spectral overlap by the uranium (as uranium oxide) in t. very other matural alpha-emitting? nuclides. How - thin layer on a, metal disk. ElectrOdeposition ever, ifthorium-2A or protoactinium-231 conditions are critical because thick or non - are present in great excess,broadening of uniform deposition must be avoided, and in- their pips might introduce a small error, terfering radioisotopes must be kept in the Transition metals, when present its great solution phase. Thick or nonuniform electro- excess, might be carried throughthe "final ' depositions result in distortion of the alpha electtodeposition to increase the mass of the energy peaks and reduced countingeffi- dep'o'sit. This would broaden the alpha energy ciency. The procedure is described in detailfi)eaks and reduce the counting efficiency. None of these possible adverse effects have by Edwards (1968). yet been ,encountered in practice. Alpha speciroscopyiscarded out' by -means of a surface-barrierdetector ,4. Apparatus with' output to a linear amplifier and multi- 4.1 Detector, silicon surface-barrier de- channel analyzed. Readout is' by means of tector with approximately 450 mm2 sensitive an xy plotter and electric typewriterwhich area and depletion depth ofOmicrons or ,411

prints out counts in each energy channel. more. - The alpha spectra of the uranium isotopes 4.2 Vacuum ) chamlitr. The detectoris are asfoltows: mounted in a chamber which is evacuated

vv ./ 94 TECHNIQUES OF WATER-RESOURCESINVESTIGATIOI4S-

after the samp ,le is inserted. This is essential 6. Proeeduie to,' minimize 4cattering; of .alphas by air. A' 6.1 Determine the volume of, sample re- vacuum.,,pum moisture trap qui: ed by,cartying Out the Ihiorimetric urarli4 are use-ti t° 'vt,cuum:at 0.1' torn analysis by *method g-1180-76 or R- I. . 4.3 'Mu nnelnttlyzer array-. The sigr 1181,1W as in, icafed .1;4y,,t1-1 nature of the; riai is f .,..rom tor thrOngh a pee-. The weight -1of Uranium ainplifier t inear a liher *irit4,.4a 'that can be used in the *inotopie analysis is Channel i4nalkzen, re, the alpha energy"220;yg and the minimum as g.5 -Recorri- Pulse's are riluted-,their appropriate than= mended -sample volumes for a 'thousandfold .4nels in the memo .The analyzer should have 'range p.f. uranium cOncentrations areliven a minimum of 256 channels if the full resolu- in table 2. 1r tion capability of the best silicon barrier de- tecObrs is to be realized. .4.4 'Readout system. The.mernory may be Table 2.-Recommended sarriple voltames, and reduced volumes for isotopic uranium analyii readout' using a plover, 'teletypeunit; punched tap; magnetic tape; 'or other ap- Volurire. jn liters U concentration- Rec- Reduced propriate means. The combination .of x-y ommended Minimum. volume plotterarid. electric typewriter hasbeen* , 4' 25 25 - -5 found to besatilitagtory.-- .2 25 12.5 5 4.5Chemical - separation apparatus. The .3 25 4 5 .4 2Q 4 chemical apparatus required for method .5 20 4 1181-76 (items 4.6 t.8) are used. .6 20 4.2 4.6 /anzexchae comizs.,These are de- 20 3.2 signed to hOld.401 of liquid in afunnel top 1.0 29 2k5 12- 0 2:1 and to pass the solution throiigh Et 14-cm 1.5 20 1.7 lengthofion-exchangeresin, cmin ,2.0 1¢' 1.25 diameter. 3.0' 10 .84 4.7, EleetrolySis apparatlfs. The cell is -de= 5.0 ).0 :50. 7.0 5 .36 signed to plate a circular deposit 2.2 crn-,in ,10 -4- ,25 diameter to' correspond with the Sensitive 12 5, .21 diameter of freNalpha detector. The deposit 15 .17 iscollected on a diskw'h'ichis 20 2 1 ,30 2 .08.13f clamped onto the bottom of a Teflon cylinder 50 --2 .050 1 .,thus forming 1:iielectrolysis cup. The titani- 70 1 .036' 1 um, disk is the cathode. The andis a flat 100, .025 ,, 1 coil of platiniim wire suspended i2 cm above the titanium disk. POwer is supplied by a Ifthe sample volume exceeds 1 'small 12-volt rectifier vvithsql-tnieter and eaporate on a; hotplate t*O- the- reduced meter. The titanium' disks are-AFein.7,1- 'volume value shown in table. Ifthe reduced diameter: volume exceeds 1 'liter it is .necessary to, vide, the sample into two or more 17liter 5, Reagents tioris. Each portion is carried rough te- EtectronlatrIng rcag'nts, ,C1 procedure as an individual ..sample through tion,.2 N; acetone; 41,nd ammonia. step 6.3. 'Run a blank of .1-literdistilled

. 5.2 Ion-exchange reagents, Bio-Rad. A.G water through 'the procedurt

1-X8, 50-100'res.11... or equivalent. Llyeiro . .6.3 Carry out the iiranitirn exthetion.pro- chloric acid, 8 N and 0.1 N. ;* '..cecitire, method R-1.181-76; steps4.6.2,through 5.3'Prfcipitation-extraction reagents. All 6.111. If'two or more 1.-liter-portioris of -one reagents required for the precipitation-ex- sample are extracted, combine the extracts traltion steps of method R-1181-76 are'used.. before step

r.#.7-T. N/ tt NATIONF RADIOACTIVE SUBSTAN*CES, 95 , , METHi3D,S.'FOR. DETER t . '--' 6:4 Dtsgolvethb dry residue that remains, .malized, to the same counting time, this also froth the evapOraticon. of the -e layer in ,corrects for background. .1.0"ml of 8 N,HC1. . .,- - tiTile isoto ic"ratio is: 6.5 Prepare thk icm-exchange columns byv1 1..i-234 C-234 seisiling g- cif resin in beakecdth 13 N '1:1.7238 HO. Translef to the columns and wash with 3'N here 8 N HC1. 6.6 Pour the solution from'fitV vitt lam, C-*23:4,,= counts 'under ,t1le '4,763 4Ier con-7xchnge tube. Allow to flow xbrosh at "peak:CO,erected for blank, and th? rate of 20-30 drops per minute. Elute. C-238 --counts under the' 4.195 MeV ehori,Um with 50 ml of 8 N.' HOI and discard peak corrected for blank: 7.2 Determine loncentr4ionofeach 'this elu7te. Elute uranium with 60 ml,of 0.1 uranium isotobecif desired, .* applying the :N 11C1. s isotope ratio, to the concentration of total-- 6,7 After evaporating to .dryness, adding-- - .uranium as determined by fluorescence meth- 141.59 and evaporating again to eliminate od R-1180-76 or it-1181-76: the last traces of HCI, prepare the residue for electrolysis byk di'sscilvinijn the electro- 8.,Repoit lyte, 1-0 ml of 2 N NH ,C1.. 6.8 Transfer' to the electrobrsis cell,and Report activity ratios less than one to'tl:vo plate the uranium onto the titanium disleus-: significant figures. Report activityratios 'greater than one to three significant figure's. . ing current of 12.7.6.1 ampere.°Electrolyze for 6 0 100 'in* - 9. Precision 6.9. Introduce the dry sample on the ti- tanium disk into tit vacuum chamber, pump There are .insufficient data to establish a ,dmvn to 0,1 torn,r an't1 coufit the .alpha. activity ireliabN; experimentalstandard,deviation. oifthe sample fOr.1,000_ min using the eorgy Standard deviation based on counting,statis- range 3.8,5.3 MeV. tics may be-calculated using the following: 6.10 Printout the spectrum_ with the xy 17/ (C-234) +B+1 (C-238) -i-B41 plotter and the typevyriter, (C-234) B)2 ( (C-238)B)21-11 phere- 7. Calculations t B 'experirriehtally,gletermined blank. 7.1 Identify the uranium isotopes present Derivatibn of the equationmay'be thund in. on the basisojhe plot, using, the data Edwards (1968) . frbin the typed readout, ,establish the count under the pringipal: alpha energy. peak far Reference -vor each isotope by summing the counts and sub- K. W.,.19,68, Isotopic .analysiss`trf uranium tracting the blank: Since.backgrotind for the in"nAural waters by alpha, syectrometry: U.S. samplesand the-blanliis the same when Geol. Stirvey Water-Supply -1?aper..1696F, 26 p. -C