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••1 1 PRODUCTION AND APPLICATIONS OF *^Ac

T U L.H. BAETSLE, A. DROISSART

L'

U C L • June 1973

I

BLG 483 144, avenu* E. FUsky, BRUXELLES 4 E. PlMkylufl 144, ÏÏKV3$tL 4 (BELGIQUE) CWLOU) ..H. '-ET5LE., *. Df*OiwjAST

'il G 40 ;, jun» J.^1 '', •

Df»ODUCTiC;' i»1;. -BPL'C-TIJN5 Or '"-'*':

jummir^. - i'>»r i sho't survey o* ">e TI a i n c n ew i c * I ana nuclear properties "* -c 'he earlier develoDed o rodu'. t i on tec^niiu'5 are reviewed. The 'jraime- ^cjle nroluc*!on o* ii'-'^c is tised on *he irraaia'ion of la'ge amounts o' o, ; r, «he 8^ reactor.

r In tkt n0» call facilities '"e irradiât ei targets -tre reo'0cesses us ng o rec i o • t-s t i on and ion e»cKançe •echnriues. The 'unction o* the ad- s o r o • i o " in< ventilation facility is described schematically as it takes oart in 'h» hot ce' ' operations. *ctinium-227 can be used as heat source cr in conjunction with Be as neutrcn source. The isotooic heat source oro- Traiime ai^s at the development of ! t^er-noionic jon*er*er. The neutron sources orogrjinfne coiDrises the production o* 10 to 10 ns" sources and an evaluation c* their use in oil well logging, on-line activation analysis, and neutron radiography.

L.M. 3AETSLE, A. QROISSART

3LG 483 «June 1973)

PRODUCTION AND APPLICATIONS OF 227Ac

Î11Î.1 v.2ilin2' ~ ** een '•orte opsomming van de voornaamste chemische en nukleai-e eigenschaocer van Ac, wordt een overzicht gegeven van de reeds eerier ontwikkelde produktietechnieken. Ce gram-schaal produktie vin 22?Ac 22 is gebazeert op de bestraling van grote hoeveelheden 6fta ;n reaktor BR2.

in de hete cel installaties worden de bestraalde kapsules opgewerkt door •uiddel van o ree i p i t a ti e- en ionenmisselingstechnieken. Oe funktie van de radonadsorotie- en ventiIatie-eenheid wordt schematisch beschreven zoals ze ootreedt in de hete-cel ooera+ies. -227 kan gebruikt worden als A-i TT, têS ror, of, samen ret 3e, .-* i s n eu t ronen b ron. Het ï sot*pei»-wa rmtet ron pro­ gramma beoogt de ontwikkel ing van een termoionische omzetter. Het neutronen- o o _ i cronnen orogramma omvat de oroduktie van 10 tot 10 ns bronnen en een evaluatie van hun gebruik in o Iiebron-"logging", on-line aktiveringsanal y se en neutronerradiogra'ie.

L.H. BAET5LE, A. DR0ISSART

BLG 483 (June 1973)

PRODUCTION AND APPLICATIONS OF 227Ac

R£sum4. - Après un bref aoerçu des principales propriétés chimioues et nuclé­ aires de l'Ac, les techniaues de production développées antérieurement sont

résumées. La production de 'AC à l'écheMe du gramme es» basée sur l'ir­ radiation de grandes Quantités de 2°Ra dans le réacteur 6R2.

Les 'bibles irradiées sont retraitées dans les installations de la cellule :h aude en utiIi sant I es t PRODUCTION AND APPLICATIONS OF 227Ac

L.H. BAETSLE, A. DROISSART*

June 1973

BLG 483

Work performed in association with UNION MINIERE, 1 rue de Is Chancellerie, 1000 Brussels ACTINIUM

Introducti on

The element actinium received its ^ame from André Louis Deb ier^e '1: in 1633 bur was really identified as a rare earth like element cy criedrich Qskcir Giesel •'2 ) in 1902. It was found in the residues T1 * the 'J ores I pitch bien a e] associated with and rare earths .

The honour of having separated actinium devolves upon Gtto Hahn (3j in 190S who discovered that almost all the radiation asso­ ciated with actinium comes from its decay products. The controversy about this discovery has recently been related by H.W. Kirby (4) who showed how both scientific logic and intuition were necessary to cer­ tify the existence of this "ray less" element.

Extensive reviews of the earlier literature were published Dy Hagemann ,' 7) and more recently Kirby (6) reviewed the analytical chemistry of actinium and included unpublished work from the lound . Boussieres (5) reviewed the general chemistry of actinium.

Chemical properties of actinium

Actinium is the first element of the series and has a chemical behaviour which is almost identical to that of lan- tnanum tse lightest member of the series.

The physico-chemical data of actinium and are summarized in Table I V?)(8 ) . It is clear from this comparison that it is extremely difficult to separate actinium from lanthanum but explains on the other nand why actinium was always found in the rare earth fraction o* the pitchblende residues.

Nuclear properties of the actinium

All the are racioactivo with half-lives ranging from 1 s to 2 1.77 y as summarized in Table II. It is of : 2 course oriy <- 7 /\ c w-;t,n the 21.77 y half-life which if?, of technological interest. ^'Ac constitutes a of the 4 n • 3 series (see Fig.';. Actinium-227 itself is a we?k 0 emitter with only 1.4 % 27 a emission Dut its daughter products ^ 7r (13.73 d; and 223R3 ^11.43 d) anc other short-lived Daughters are at tne origin of a substantial amount 0*" ot, _ Ö and y radiation. The radioactive families of 2 2 6R3 p ;4n+2 rjn,± 228)-p (4n) are shewn in i£. 2 and 3. 3.

PRODUCTION OF ACTINIUM

Historical developments

It is striking that apart from the preparations of trace quantities of actinium by (9) using precipitation and fractional crystallization processes no substantial progress was made until Peterson (10) produced Ac artificially in 1945 b^ irrad­ iation of 1 mg . When Hagemann (11) irradiated 1 g of Ra in 1949 he obtained for the first time 1.8 mg Ac free of rare earth. By using TTA extraction a 95 % pure Ac fraction was obtained.

When irradiating larger quantities of Ra in reactors with higher neutron fluxes cation exchange techniques were used more and more frequently (12) (13)»

From 1963 on, a research programme was started at Union Minière in conjunction with the BR2 reactor staff of S.C.K./C.E.N. in order to evaluate the possibilities of the BR2 reactor for Ac production from irradiated radium.

In September 1965 Union Minière has undertaken the irradiation of 5 g 226Ra followed by separation and purification experiments ; the purification of Ac being committed to the S.C.K./C.E.N. (18).

When it was decided in 1967 to start in Belgium a gram bcale Ac production programme the need for new separation techniques working in highly irradiating medium was urgently f^lt.

Belgian production programme

Union Minière, Brussels, and the Belgian Nuclear Research Centre S. C. K./C. E . IM. , have undertaken together the gramme-scale production of actinium at the Mol laboratories.

The following important facilities are available ;

1. the high flux BR2 reactor with a neutron flux of 3 to 14 _ 4.10 n cm-2 s 1* 2. the LMA processing laboratories with hot cells equipped for work with radon; 3. the radiochemical analysis laboratories for production control.

With these facilities it is possible to produce about 10 g of 227Ac per . y croducti -, i- i-i • of radi ce e., s a:: :hs T o owi n, reactions

C' v -^ 2? k ?r> 1 / ? : {Yi y;

/ O o o 97 8 30 c o ö >u? 4 c? 6.13 /- VT V )

2 2.1 fc 22i? 2 25 Th r* Y;

Detailed studies about the nu-clear transformation- were made at different institutes all over the world '14) Hi)(16) out the most pragmatic and practical results were obtained at S.C.K./ ci tne first, production campaign o* I9 60-197G Cl/).

It may be stated that a yield of about ".C t * -> s- U i. I ~>u and G. 3 to C.4 % 2 2 8 7 (-, may he retained at an integrated flux o* 2 te 3.*û':'1 nvt. In a few cases we have observed a slightly higher transformation yield which would point at a contribution of the epitHerrr,a 1 neutrons. However, loading of the fi R 2 reactor being modified at each cycle.unexpected variations occur in the production y i e 10 measured en each individual capsule?. But the oraer of magni­ tude o^ the nuclear reaction products 2 2 / /\ c ancj 2,d8jn ^ c not change.

he capsules contain between 30 and 5C g of Ra (as RaCO ) each and contain after two irradiation cyclec s the following approxi- 227 mate a• vities : 30 0 ttoo 5500 CCii 226^QRaRa,, 26 to 4 3 Ci Pc and 7 0 to 10 Ci • 228Tn.

£ny chemical processing of irradiated targets must take into account these basic data and must be flexible enough to be adaptée to the activity level.

CHEMICAL R 0 C E S S I G 0 F IRRADIATED RADIUM

The chemical treatment of irradiât 3d racium targets has been gradually adapted "c the amount of radioactivity involved.

TA extraction 1 1 J gaje satisfactory results when irradiât i n g 1 g c f R a a n c p u i' layin:vineg 11 iïiE of Ac but ne success f u a n d quanti ta tive separations wart reported afterwards (6) (18, By chemical precipitation techniques it is possible to separate Ra from Ac and Th. Several separation techniques have beer. eraposed :

Ra as Ra C N0 80 HNO. (18) 3'2 in Th (10 ) in 2 M HNO (19) h as { Th (0XJ„ in 2 M HNO^

as Ac9 ( 0 X ] _ in dilute acid (20)

We have found that the Ra(NC3) precipitation is an excellent and selective method to separate Ra from almost all other elements except Ba. However,it requires the use of equipment. Thorium precipitation by periodic acid is tricky and hard to perform with compounds having such high specific activity as 228Th. Good results were obtained with Th precipitation in 2 H HNO» but the operations must be carried out within a very short time because of the decomposition of the THOX precipitates by a radiation. A yield of 80 % Th precipitation has been found in presence of g quantities of Ac and up to 97 % yield when pure 228yn was precipitated.

The Ra recycling of the irradiated targets is shown in Fig« 4. it is essentially based on precipitation techniques and powder metallurgy procedures. Operational experience of the first production campaign is given in a recent paper (21).

The quantitative separation of Ac from Th and traces of Ra cannot be achieved by preciDitation techniques and therefore ion exchange was considered already in the nineteen fourties as the most appropriate separation technique (7) (22) (23).

Hagemann (23) aasorbed the Ra Ac Th mixture in 2 PI HC1 on actinium with 6 M HN0 and Dowex 50 and eluted radium with 3 M HNO 3' o Th with 6 M HN0„ • 0.1 M HF.

extensive research was undertaken at the Mound Laboratories in order to separate Ac and Th from 5 g irradiated Ra at the 35 mg Ac level (24) but the experience was considered as "generally unsatis­ factory" (6). Most troubles occurred with RaS04 precipitation in the sulphonate resin and radiolytical clogging of the columns.

Taking advantage of the suggestions of Diamond and Nelson (2S)(26) we tried to separate Ra-Ac-Th at tracer level on Dowex AG 50 W X 8 in HC10„ 12 M but got into trouble when the resin expanded from its shrinked form in 12 M HC10, to its expanded form in 4 M HN03 (27). 5 .

Separations are possible i r principle but it appeared sc:n :r,?.t technological di**icL.ities would jeopardize this Hr_']C>„ approach whe" working in hot ceils.

Continuing our previous research on inorganic ion exchangers it was felt attractive to try the chromatographic abilities cx Zr and Ti phosphates, hydrou? of 3b and ferro- cy aride c* ^o and W (27). Very good results were obtained with t i\. a~ i urn phospnate at trace level and relying on this encouraging result a separation of 2^-/\c ancj 228rn at Curie level was u.icer- taker. i - the 1GQG Ci facility of 5 . C . ,;. / C.E.N, at Mol .

In one run through a 5 g phosphate column,

Th '1.2 Cii was separated from the 227/\c fraction in 4 f\ HNG-^. A secor-d rjn of the effluent of the first column [dilutsd to 2 ^i through an identical titanium phosphate column was used to ensure a total 226Ra decontamination from the 227/\c fraction. The sepa­ ration factor between 227^c ancj 2 28rn amounted to 5.10.3 which was considered as sufficiently good for large scale separations. The Ac fraction contained still corrosion products and small amounts of Ti and phosphate ions.

The gramme-scale Ac production was started in 1969 and soon it appeared that the presence of unavoidable and large con­ centrations of corrosion products e.g. Fe , (Mi, Cr interfered with the '"^Bjh adsorption on titanium phosphate. Moreover the adsorbed r 229- n was difficult to elute quantitatively and unpredictable precipitates of 227Ac were found on the walls of the vessels •possibly Ac(H P0 )^ .

A completely new separation method using anion exchange in H IMG,, nedium was developed in ou£ and relies on a weak anionic complex /_ Ac(!M0~] __//_x which is slightly adsorbed by OQWEX AG 1 x 8 (a strong anion exchanger) in 6 to 7 P! HNQg. Since it is known that Th is very strongly adsorbed on the same ion exchanger (P.8) a separation from Ac and non - comp lexed cations .' m c s t of the corrosion products) is possible.

Separations for analytical purposes confirmed these findings and after a few months the new method was introduced successfully in the Ac production process. A great advantage of the use of anion exchange resins lies in the absence of SO^ ions wnich may cause Ra precipitations in the column. However,the acti'.ity level which can be handled is limited tc 100 Ci of 228rh oecdL.se otherwise the radiation damage becomes too important. 'he results obtained during the first production campaign have shown that still some impurities follow the Ac -Taction and therefore a second anion exchange step with DOWEX * < 5 in the CI" form was added to the two previous steps. Since Doth ~b and Pt form strong chloride complexes in 2.5 M HC1 (pbCl„ . r r4 a complete purification of actinium is achieved.

Fig. 5 shows the complete separation and purification cycle of Ac and Th as it is operated at present in the hot cells. 'wo grammes of Ac have according to this procedure been ourified in one natch '21) and currently 50Ö mg batches are now processed in routine operation.

The radiochemical analysis and quality control of all the separation steps is made by instrumental a and Y spectrometry linked to a PDP 8 computer. Details of the procedures were given in an earlier paper (21). Chemical analysis is made by emission spect rography.

RADON ADSORPTION AND VENTILATION FACILITY

Work with such large quantities of emanating requires very special security measures in ordei to avolH endangering the working conditions of the hot cell operators and to remain within safe limits of discharge at the stack, of the building. The limits imposed by health physics authorities are 10"s Ci s"^ of a radon isotopes mixture (222Rn, 220Rn and 219Rn) and the MPC in air at the vicinity of the facilities may not exceed 3.10'^Ci m~3.

Referring to Fig. 1, 2 and 3 it is clear that the continuous production of the three radon isotopes exceeds largely the permissible ccncsntrations. The nuclear-physical backgrouna of the radon adsorption and ventilation system iias been discussed in our previous paper (21). Several functions have to be accomplished by the radon adsorption ventilation facility :

1. keep the r^idon emanation inside a closed loop ; 2. reduce the discharge of air at the stack to the quantity of inieaking air ; 3. remove the acid vapours and moisture from the circulating air 4. reduce the radon level in the boxes when required ; 5. guarantee the depression in the ex boxes when an accidental leak occurs. ft . * '/ irder ta provide these r 31 P e r cmp Aex 5 d sorption dn; ventilât! in 11 has be o u i i t .

"-g snows tne depression line which Keeps tne ertire * 3 31 v at a depression c- to - 4 0 mm W C When air h s s leaked into the decressio". decrease? and at set value ; e a - ;.u->n mm sl.es :p£r and air is s u c K e o through a molecular sieve cartridge n ->' r, f ,- a 1i a c i o itrogen cacied charcoal trap. The cleaned air is dis* n erg a c into tne stack or the c u i i d i r. g. At depressions excee,rt-: r g -4 0 mm MC compressed air is injected into the loop.

rig. 7 snows the ventilation scrubbing loop whiuh is continue sly in operation. vapours liberated from reaction vessels cd-taining eg. h!M0- are flushed through an alkali scrubber filled with raschig ri.ngs followed bv a cyclone. condensor working at 1 ^ o - a seconc eye lone and a blower of 35 m^h" . Each large h o .< a and OU_J has such iooc . T i. i cig. 6 shows the intervention cycle which keeps the rad e co entrât ion inside the a box under control. This was necessary ce cause 22 zRn diffuses through the sleeves of the master slave manipulators, Air leaded with radon is continuously turning aro_i,nc in the ventilation _oop but nay be diverted through a purification set [molecular sieve + charcoal trap) when it is required. This way the radon concentration in the box drops at a rate wnich is proportional to the number of renewals per hour '.in this case 5 J . Fie. Z shows the superposition of the three loops

By -lushing air during one hour through the charcoal traps at renewals per hour the radon concentration is in principle red.ceo tc 3 % of its original value. Such a procedure is only valid when 222Rn is involved. With 22ü Rn and 21'9Rn the production rate from mother isotopes exceeds by far the. adsorption rate on the chartoal traps.

•f an accidental leak occurs [tearing of the sleeves of tne master slaves air may be discharged through the charcoal traps i n t c the sta;:.'. .

'he -facility has been running now for several an o" ;ay considered as the most appropriate answer to the nuclear a * s t y p r o t 1; • ÎT ; 29) APPLICATIONS OF ACTINIUM

The application:, of actinium are to a ce. tain extent similar te those cx the transuranium elements. As showr in Fig. i sach actinium nuclide emits with a half-life of 21.77 y five alpha rays originating from the daughter products. The energy emitt?-1 c> ere gramme of actinium in secular soui1ibrium amounts to 14.6 Wg"1. xith its high specific power and relatively long naif-life actinium constitutes an outstanding for fuelling heat sources. Table III shows a series of radioisotopes which may be or are currently being used as heat source. 227 A glance at this table shows that Ac occupies a foremost position among the isotopes listed. None of the presently available ot emitters except ^ Cm can compete with actinium when lcrg-term missions are envisaged requiring compact heat sources. 7 7 8 In addition,it has to be mentioned that Th is produced simultaneously with 227^c (juring the irradiation of radium. "he characteristics of this nuclide as heat source are without competition but the strong gamma emission of one of its daughters (208T^ . y 2.6 MeV) limits its use to "strongly shielded" applications.

Neutron sources find diversified applications in moisture determination, ground water hydrology .mineral exploration, logging o^ oil wells, on-line activation analysis, reactor start-up sources and neutron radiography. - 1 Taking into account the specific activity (Ci g ) it is clear that 14 mg of Ac produces 1.5 time more neutrons than 1 g of 225pa DUt the is decaying with its inherent half-life Of 21.77 y. 2 2 S 2 2 7 The transformation of Ra into Ac and its use in neutror sources is a definite economic advantage which justifies cy itself already a continuous production effort (31). 9 7 B The accompanying production of Th can be used for two 9 types of neutron sources : 228yn ge with an output of 2.10 n/g Th whicn is about ten times higher than the 227/\c-ge sourCes and photo- n e-troR sources with OnO or Be as neutron emitting medium. 223. g tT. h f\, e photcne^tro^ sources h ; y ~ S e. or [y n are i "terestirg because the hal+-life ov 2^Srh (t 1/2=1.9 y) is 124 - er£ = a- that :? 3b -t 1/2 - 6C.4 a). 226 e neutron energy of the photoneutron source ' v - n 5 T, : !W3 2 lev! tha' that of the ian] sources

ISOTOPIC HEAT SOURCES

The incentive to start a large-scale production of actinium was the joint decision between Union Minière and Brown Boveri to cevelop a thermoionic generator of 25 0 W th fuelled , . i.?t j-h L. 1A 3n g of 227 Ac (2?; T33/1 .

:xperin(enta l work has been performed at S . C . K.. /Z . E . N . the metallurgi c.a l conditio mng of Ac?0 aiming at the formation a m ixea s tab le at 18 00 °K A solution between cC. and ThG was proposed a fue 1 containing W as heat conducting ateria>i i and capsulated in a 2b Re capsule.

219 bu iId "up an d-. Rn (actinon) containment in the ue 1 c apsule recei ved conside rab le attention especially a semi - ermea bie venting system s u f f i ci entl y permeable to He but providing s u f f ici ent delay to avoid t he d if fusion of actinon and its daughce: roouc ts through i t (34). A protc type heat s ource containing ? g of actinium in he * o rm of Ac_0q representin g nearly 30 thermal watts was tested or ab out 200G h^a t a tempera •cure of 1800 °C (25). After melting he f'j el in the r° rous prefer med matrix (fh0-W 50 \ porosity], h s ca psuie was Ke p t at 16 0 0 °C. The vacuum furnace bell was • c n n ecte d to a mas s spectrome ter He leak detector and to an alpha pectr ometer. The Si alpha d etector built into a dead end of a ub e w as connect ed to an ampl ifier and 400-channel analyser.

At 1800 °C the He was quantitatively liberated from fuel matrix but small amounts of actinon gas were found in the furnace atmosphere. Post mortem examination has shown a small fissure in the upper part of the capsule. The T h 0 9 - W porous plug did not show any damage but its efficiency could not be verified.

Immobi1izat ion of the AC2O3 by melting in a porous refractory body showed well feasible. The oxide has been taken up completely and only a srnal 1 fraction of the fuel was found in the uCpsr part. The hot, cell operations were performed in the V2A :ei:s 0* the LMA laboratories (ZC). For technical reasons the tontinuation of this project has been delayed. NEUTRON SOURCES

A second field of application in which actinium has beer: recognized as an isotope with outstanding properties is the production of Ac-Be neutron sources. The increasing demands for high intensity neutron sources may be at the origin of a long-term production programme.

-5 C O TTÛ 227 Table V shows the comparative merits of *" Cf, Th Be a^d Ac Be neutron sources. 2 27 252 228. An important advantage of Ac with respect to Cf and Th is its half-life. The neutron spectrum of Ac"Be sources has been studied by Dixon et el. (38) and recently by Geiger et al. (39). Both curves do coincide in the higher neutron energies (> 3 MeVj but some discrepancy is observed at the lower energy part of the spectrum. More research in this field is necessary and since new information can be obtained by the pulse shape discrimination technique a better knowledge of the spectrum is to be expected in the near future.

Union Minière which has lieveloped the fabrication of Ac-Be neutron source (31) has put at the disposition of the S . C . K ./C. E.N . a 7.5 107 neutron source which served to start a research and development programme on the use of Ac-Be neutron sources in industrial process and quality control.

The total neutron output was measured with the MnSO. bath technique and did coincide within 1 % (7.50 compared to 7.57 1§ 7 ni with the value measured by Union Miniere.

The relative flux measurements are displayed in Fig 10 and show that a linear decrease cf the flux is observed from a maximum at 20 mm distance to 50 %"" at" ""70" m~m~ distance-•-•-- . -"-•-The- -maximmaximu- u m thermal flux was determined by a GeLi detector calibrated with respec•esp t to the absolute activity measured in a 4 IT $ y coinciden ce counter . The maximum flux amounts to 3.8 10 n cm s or roughly 1 % of the total neutron output. This value corresponds to flux measurements made around 252Qf sources (40).

Several elements can be monitored continuously by on-line neutron irradiation of a process stream and gamma counting of short­ lived activation products or by direct measurement of the prompt gammas. Various elements are partie u la rly suitable for this t v p e o ~ on-line analysis. Preliminary experiments with liquids moving a r o « n c the A c- E e source have been carried out in a set-up schematic­ ally snown in pig. 11.

~able VI shows the same results obtained with \/, Co. A g and Al in solution. The concentration levels of the elements listed can be analysed continuously at the mg/ml level or higher. Inter­ ferences will oe studied intensively in cur research programme. The scope of this method is limited to those elements having very short Uvea radioisotopes.

A second type of application of neutron sources in activation analysis is the direct capture y-ray spectrometry (41) (42). The concurrent development of intense portable neutron sources and the availability of Ge-Li detectors with very high resolution is responsible for this new flourishing field in activation analysis (43).

Fig. 12 shows the experimental set-up installed in our laboratory. Valuable results can be obtained with, for example V, Md . Au. Cl, Y, Hg, Cd. Hf, Dy and Yb if the samples are sufficiently large ;> 1000 ml] and the counting times not very critical (1 Lo 2hl.

Fig. 13 shows a y spectrum obtained with the set-up of Fig. 12 and using CC14 as target. Attention has to be? drawr, on the series of peaks resulting from the presence of structural materials used in the set-up (Pb. Fe, Ni and Cr).

The direct capture gamma ray spectroscopy is a potentially powerful technique which is developing at fast rate and may find applications in mining industries and in non-ferro metallurgical processing plants.

Acknowledgments

The authors wish to thank the staff of Union Minière and the staff of the S.C.K./C. E.N. 13.

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) Heremans et al. 14ième Comité des Laboratoires Chauds, juin 1972 , Ansell K.H. and Hall E.G. Proc. Am. Nucl. Soc. Top. Meeting on Neutron Sources CONF 710402 Vol. 2 I 90 (1971) ) Dixon W.R. et al. Can. J. Phys. 36_, 6, 699 (1957) J Geiger K.W. Int. J. Appl. Radioisotopes 1973, 24, 165 i O

Californium 252 -:':gï>ess ."..:. ls 'j':bsv 196 9, r . _T

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Fettweis P. et al î.iV. repcrr 515 -??£ '1967. TABLE I PHYSICO-CHEMICAL PROPERTIES OF La AND Ac COMPOUNDS (S)(6) (?)

La Ac

ELEMENT Number Mass Z = 57 M = 138.82 Z = 89 M | 227.03 Electronic Conf. (Xe) 5 6 s2 (Rn) 6 d 7 s Valence + 3 + 3 HP 884 1050°C BP 2730 3200°C Radius 1.06 Î 1.11 A Cryst. Structure f r C ax = 5.30 A f C c = 5.31 A OXIDE MP 2315 BP 4200 6.57 9.19 = 6.15 Â = 4.07 À = 6 29 Â Cryst. Structure 1 = 3.94 A a, 1 o CHEMICAL COMPOUNDS LaF, hex 4.14 A 7.33 AcF- hex 4.27 A 7.53 A LaClL hex a 7.46 4.36 A AcCT, hex 7.62 À 4.55 À LaBr; hex 7.95 I 4.50 Â AcBr! hex 8.06 Â 5.68 Â -28 -27 SOLUTION CHEMISTRY La oxalate S 6 10 Ac oxalate S 6 7 10 -19 -21 La (OH), S 1 10 Ac (OH), S 1 3 10 TABLE II ISOTOPES OF ACTINIUM

Mass Ha If-life Decay mode and energy Production method Number of principal radiations (MeV)

221(?) Is a ; 7.6 ?HTII (d,9n or p,8n) Û$P a D 222 4.2 s a ; 6.998 (93 %), 6.952 (6 %) „,Th (d,8n or p,7n) ^ Pa or 226Ra (p,5n) 22^Ac 223 ? . 2 min a (99) ; 6.657 (37.5 %), 6.643 (42.1 %) , 6.561 '•^Th (d,7n or p,6n) ^Z/Pa H3.3 %), 6.52 53.8 %), 6.47 (3.2 %) ; E.C. (1 %) 224 a (10 %) ; 6.205 (32 %), 6.139 (26 *), 6.044 (32 %) ?32Th (d,6n or p,5n) 228Pa 2.9 h 6.002 (5 %), 5.939 (3 %), 5.870 (1 %), 5.72 (<1 %) E.C. (90 %) ; y -0.217 (62 %), 0.133(28 2) 225 a 5.829 (52 %), 5.793 (28 %), 5.732 + 5.724 oofiTh (n.Y) ^l3Th - 233p deca 10.0 day a y or (12 %), 5.683 (1.3 %), 5.6 38 (4.2 %), 5.610 226Ra (d,3n)225Ac (1.0 %) , 5.581 (1.0 %) , others 22Ó B (80 %), 1.2 max llha (d,2n) 225AC or 29 h E.C. (20 %) ; - 0.253 (11 %), 0.230 (47 %) 226Ra (p,n) 226Ac 0.185 (9 %), 0.158 (32 %) 227 6 (98.6 %) ; 0.046 max 226 227 21.77 yr Ra (n.y) Ra a (1.4 %) ; 4.949 (48.7 %), 4.936 (36.1 %), 4.866 natural source (235y decay) (6.9 %), 4.849 (5.5 X), 4.786 (1.0 %) 4.759 (1.8 %, others 228 6.13 h 6~; 2.11 max Y ; 1.587 (8 % complex), 0.96 (20 % complex) natural source ( 232 Th decay) 0.908 (25 %), 0.34 (15 % complex, others 229 66 mi n B~ popR!Raa ((' r'»^)o'iriR3 i3i 230(?) < 1 min 3_ ; ;2.2 max -"- Th ('d.ap-^A c 231 15 mi n B ; 2.1 max Y ; 0.71, 0.39, 0.28, 0.185 232Th (Y,p)231Ac J TABLE III ISOTOPES FOR HEAT SOURCES

Nuclide Decay type Half-life Specific heat W g'1

210Po a 138 d 141.3

227Ac a B Y 21.77 y 14.6

228Th a 6 Y 1.91 y 170.5

238 Pu a iy) 86.4 y 0.55

Lm c y 163 d 120

Cm a y 17.6 y 2.74 TABLE IV

ALPHA-NEUTRON SOURCES (30)

Type t 1/2 i energy Neutron energy Yield in Average J Maximum lO^s^Ci"1

2 10 PbBe 22 y 3.72 1 4.5-5 10.87 2.3-2.5 210 PoBe 138.4 d 5.30 4.2 10.87 2.3-3.0

225 RaBe 1620 y 4.78 3.9-4.7 13.8 10.0-17.1 27 AcBe 21. 77y 4.86 4.0-4.7 12.8 15 -26 228 ThBe 1.91y 5.43 ! 17 -20.0 238 PuBe 86.4 y 5.5 5.0 11.3 2.2-4.0 241 AmBi 458 y 5.49 5.0 11.5 2.2-2.7 242 CmBe 162.5 d 6.12 11.5 3.0-7.0 244 CmBe 17.6 y 5.81 11.2 6.0 TABLE V

FUNDAMENTAL DATA OF 252Cf, 228ThBe AND 227AcBe NEUTRON SOURCES

228Th 227Ac

Half-life 2.55 y 1.91 y 21.77 y Specific -1 ci 534 822.4 72.64 activity 9 i des s 1.92 1013 1.52 1014 2.6 1012 n c-ln-s g 1 2.34 1012 2.34 1010 1.67 109

Neutron energy 2.3 4.7 4.5

Gamma dose rate at 1 m Rad h-lg"1 140 680 0.89 TABLE VI CONTINUOUS ANALYSIS OF PROCESS STREAM BY Ac Be NEUTRON SOURCE OF 7.5 10'ns-

Optimal E 1ement Isotopes t 1/2 flow rate cps mi n ml mi n (mg/ml)"1

52 V v 3.77 1.39 28

Co 60"'Co 10.5 0.5 9.7

108 Ag A9 2.4 2.17 8.8 Al 128 A1 2.3 2.29 2.5 235u(AcU) Figure 1 -ACTINIUM SERIES 7.1 x 10* y (4n +3)

23fPik I 3.25 x \&>y 231 0. 227 hhfUY) Ih(MAc) 25.64 h 16.73 d

2233 Ra(AcX) 11.435ï 1 219 a Mxurât Rn(An) 3.92s Ï 3 21SPà(AcA) 1.83x 1(T3s

Z16m 207Pb(AcD) a 997% 1 stable 207TI(AcC') 4 79 m j ure 2 URANIUM -RADIUM SERIES (An + 2) 234U(UII)

2 234mPa(UXj^ ^r 1.18 m 11 n f 230 Th(Jo) IT0.63*A fit S.OxtO4 y 2Mp*(UZ) f 6.7 h I 1622I y

3 823 d I 218Po(RaA) 214Po(RaC') 2WPo(RsF) 305 m a! 1.64 xW^s 13B 4 d 2J4Bi(RaC) 4? 210Bi(RaE) 4? 19.7 m S.Old I 20S ï 210pb(RaD) Pb(RaG) aW.04% l£* a iSxIO^K M 19.4 y &.*L stable 206Tl(RaE") 1.32 m 4.19m Figure 3 THORIUM SERIES I nn }

™Th(RdTh) 1.91 y

22B Ac(MsThj 6.13h 2X Rê(MsTh{) S7Sy

X°Rn(Tn) 515s i VGPolThA) 0 158 s 212Bj(ThC) /3 60.5m I & 2'2Pb(ThB) OJJS 2 V. 10.64 h /3 208Tl(Thc") 3.10 m Figure 4 Radium recycling and separation of Ra from Ac-Th

FRESH

RaBr2 i IRRADIATED DISS HN03 Ra( N0 ) Ac/Th Ra-Ac -Th 3 2 RaC0 TARGET DIL. H NO 8% ppt FRACTION 3 SOLUTION *HAc 4 t DISSOLUTION ACID FILTERING IRRADIATION t BR2 Ppte RaCr04 IN

C03 FILTRATE t FILLING NEW FILTERING PRECIPITATION NH4OH DISSOLUTION CAPSULE { FIRING AS M OF PRECIPITATE co2 GRINDING RaCO IN H20 Figure. 5 Actinium and thorium separation and purification

227 226^^ 228 227 Ac*A Th * 80% Th Ac*Residual H2 OX 22 22S Residual 226Ra Precipitation *Th * Ra

2 M HN03 5 M HNO3

2M HN03 I 228 Th Fraction

I o ' .Elution O.tM HNO3 * H20X 0.5 M I Th OX 227 "'Ac* Residual Precipitate 226 Ra *Corr. products 2.5M HCl

5 M HN03 l Traces of 22BTh 1 Pb . Pt impurities Th O Chro m a tographic ï CO separation l Ac fraction J Encapsulation >b , Pt I I 1 Ra dio chemica I f 5foray* 226Ra * Corr. chemical pure products ACTINIUM o

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