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1971 Simultaneous Determination of Gold, Mercury, Silver, Tellurium and Uranium by Instrumental Neutron and Photon Activation Analysis. Frank Thomas Campbell II Louisiana State University and Agricultural & Mechanical College
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CAMPBELL II, Frank Thomas, 1939- SIMULTANEOUS DETERMINATION OF GOLD, MERCURY, SILVER, TELLURIUM AND URANIUM BY INSTRUMENTAL NEUTRON AND PHOTON ACTIVATION ANALYSIS.
The Louisiana State University and Agricultural and Mechanical College, Ph.D., 1971 Chemistry, analytical
University Microfilms, A XEROX Company, Ann Arbor, Michigan
THIS DISSERTATION HAS BEEN MICROFILMED EXACTLY AS RECEIVED SIMULTANEOUS DETERMINATION OF GOLD, MERCURY, SILVER, TELLURIUM AND URANIUM BY INSTRUMENTAL NEUTRON AND PHOTON ACTIVATION ANALYSIS
A Dissertation
Submitted to the Graduate Faculty of the Louisiana State University and Agricultural and Mechanical College in partial fulfillment of the requirements for the degree of Doctor of Philosophy in
The Department of Chemistry
Frank Thomas Campbell II B.S., Fresno State College, 1963 M.S., San Diego State College, 1967 to my parents and my sister who helped to make me the way 1 am
to my friends who believed in me even when I did not
and
especially to Linda, my unwitting inspiration
11.... there are no easy victories...."
John W. Gardner Acknowledgment
The author wishes to acknowledge the contributions to his betterment made by Professors James W. Robinson, Norman S. Bhacca, and Edgar L. Steele.
Special thanks go to Dr. Edward F. Zganjar, Dr. David A.
Copeland, Dr. J. Tracy Broussard, Mrs. Patricia A. Kelly and Dr.
Edgar L. Steele for the assistance, of a personal nature, which they so graciously conferred to the author. This grateful acknowledgment is the only means of compensation which the author is able to offer to them for their most generous efforts on his behalf.
The author wishes to express a general thanks to all of those persons who have contributed directly, or indirectly, to his work and to his life. He also wishes to thank those persons who have not been a hindrance.
The author gratefully acknowledges the financial assistance in preparation of this dissertation which was provided by the Charles
E. Coates Memorial Fund of the Louisiana State University Foundation.
Most of all, and far above any other, the author wishes to express his gratitude to Professor Edgar L. Steele who has been, not only a research director, but also a personal friend and an example as well. He took a two-time loser to the pot of gold.
ii Table of Contents
Page
Acknowledgment...... ii
List of Tables...... iv
List of Figures ...... v
Abstract...... vii
Chapter I. Introduction...... 1
Chapter II. Review of the Literature...... 4
Chapter III. Experimental...... 17
Chapter IV. Experimental Procedures, Data and Results . . 24
Chapter V. Discussion and Conclusions...... 73
Appendix 1 ...... 85
Appendix I I ...... 91
References...... 107
Vita...... 115
iii List of Tables
Table Page
1. Energy Resolution of Gamma Ray Spectrometer ...... 22
2. Experimentally Determined Values of Relative Efficiency of the Full-Energy Peak 22
3. Nuclear Data for Selected Isotopes...... 48
4. Potential Sources of Interference ...... 49
5. Data for Go l d ...... 58
6. Data for Mercury...... 61
7. Data for Si l v e r ...... 64
8. Data for Tellurium...... 67
9. Data for Uranium...... 70
10. Calculated Accuracies and Sensitivities ...... 74
11. Data for Mercury...... 98
12. Data for Si l v e r ...... 101
13. Data for Tellurium...... 104
iv List of Figures
Figure Page
1. Aluminum Disk for Linac Irradiation...... 19
2. Gamma Ray Spectrum 6f Gold 5 Days After Irradiation with Photons ...... 27
3. Gamma Ray Spectrum of Mercury 5 Days After Irradiation with Photons ...... 28
4. Gamma Ray Spectrum of Silver 5 Days After Irradiation with Photons ...... 29
5. Gamma Ray Spectrum of Tellurium 5 Days After Irradiation with Photons ...... 30
6. Gamma Ray Spectrum of Uranium 5 Days After Irradiation with Photons ...... 31
7. Gamma Ray Spectrum of Gold 10 Days After Irradiation with Neutrons...... 32
8. Gamma Ray Spectrum of Mercury 10 Days After Irradiation with Neutrons...... 33
9. Gamma Ray Spectrum of Silver 10 Days After Irradiation with Neutrons...... 34
10. Gamma Ray Spectrum of Tellurium 10 Days After Irradia tion with Neutrons ...... 35
11. Gamma Ray Spectrum of Uranium 10 Days After Irradia tion with Neutrons...... 3 6
12. Calibration Curve - Gold LINAC ...... 37
13. Calibration Curve - Mercury LINAC...... 38
v Figure Page
14. Calibration Curve - Silver LINAC ...... 39
15. Calibration Curve - Tellurium LINAC...... 40
16. Calibration Curve - Uranium LINAC...... 41
17. Calibration Curve - Gold Reactor ...... 42
18. Calibration Curve - Mercury Reactor...... 43
19. Calibration Curve - Silver Reactor ...... 44
20. Calibration Curve - Tellurium Reactor...... 45
21. Calibration Curve - Uranium Reactor...... 46 140 140 22. Growth Decay Curve for Ba- La Couple...... 81
23. Photofission Spectrum of Uranium 2 Days after Irra diation...... 82
24. Photofission Spectrum of Thorium 2 Days after Irra diation...... 83
25. Gamma Ray Spectrum of Mercury 2 Days after Irradiation with Photons ...... 93
26. Calibration Curve - Mercury (197m) LINAC ...... 94
27. Calibration Curve - Mercury (203) LINAC (Later Count). . 95
28. Calibration Curve - Silver LINAC (Later Count) ...... 96
29. Calibration Curve - Tellurium LINAC (Later Count). . . . 97
vi Abstract
A rapid, inexpensive method for the determination of gold, mercury, silver, tellurium and uranium was developed. The method utilized non-destructive activation analysis by means of gamma ray spectrometry. Both neutrons and photons were used as sources of activation. Irradiation of a stable nucleus with neutrons results in the formation of an unstable nucleus of mass number one greater than the target nucleus while bombardment with photons causes a loss of one mass number. The different radio isotopes yield different gamma ray spectra thus enhancing the likelihood of obtaining an interference-free peak. Computer reduction of the data reduces the time required for analysis to two hours per sample, only slightly more than the counting time.
Minimal laboratory skill is required to obtain sensi tivities as follows:
Au 3.4 PPM Hg 74.6 PPM Ag 198.1 PPM Te 120.0 PPM U 16.6 PPM
The precision obtained was 20% or better.
An exhaustive survey of potential interferences was conducted and means of elimination are discussed. Several modifi cations and extensions of the method are included indicating its flexibility and response to the particular needs of the analyst.
vii Chapter I
Introduction
A rapid, inexpensive method for the determination of gold, mercury, silver, tellurium and uranium in soil and rocks was developed. The purpose of this research was to demonstrate the
feasibility of determining these elements by a fully instrumental,
nuclear activation analysis procedure. Eliminating chemical
separations minimizes sample handling and reduces the requirements of time and technical skill on the part of the analyst. Thus, rapid analysis of multitudinous samples becomes possible.
Activation analysis is based upon the production of unstable nuclei from stable nuclei and the measurement of radi ations emitted when these nuclei subsequently decay to stable
states. In reactor neutron activation, a thermal (0.025 electron volt in energy) neutron is added to the stable nucleus by the (n,y)
reaction. Photon activation is accomplished by bombarding the
stable nucleus with high energy bremsstrahlung (yrays) from an electron linear accelerator. At electron energies of 30 million
electron volts or less, this results predominantly in the expulsion
of a neutron by the ( ^ n ) reaction. Combination of the two methods
of activation permits the production of two different unstable
1 nuclei from the same stable nucleus. Both differ from it by a single neutron; one is lighter, the other heavier.
In general, the gamma ray energy spectrum of an isotope is a unique characteristic of that isotope. The energy of the gamma ray indicates the isotope while the intensity of that radi ation corresponds to the amount of the isotope present. Though the introduction of lithium-drifted germanium detectors has greatly improved the resolution obtainable in gamma ray spectra, some interferences from gamma rays of similar energy remain. The use of two different gamma ray spectra for each originally stable nucleus greatly enhances the likelihood of obtaining interference- free photopeaks. An isotope which results in interference following neutron activation is unlikely to produce interference when the system is irradiated with gamma photons because both the interfering isotope and the isotope of interest result in different spectra after gamma irradiation. The reverse is, of course, true of an isotope interfering in the spectrum of a photon activated sample.
Thus, correlation of analytical results from the two methods of activation should yield a reliable value for the quantity of stable isotope present. This value, in turn, indicates the amount of the element present in all isotopic forms (assuming natural isotopic abundances to be fixed).
The vast amount of data generated in instrumental nuclear activation analysis makes the use of computer techniques a virtual necessity in the analysis of data. Programs were therefore evaluated, adapted and written as needed to provide complete analysis with a minimum of requisite operator laboratory skill.
The method as developed should be useful in geological and mining survey work (prospecting). In addition, the technique is readily adaptable to the determination of other elements and,
since activation analysis is matrix independent, the technique can be applied to a variety of other matrices such as blood, water and biological tissue. Improvements in sensitivity and accuracy can often be obtained by increasing the activation and counting times, respectively. Chapter II
Review of the Literature
A wide variety of methods is available for the deter mination of each of the elements gold, mercury, silver, tellurium, and uranium in a geological matrix. These methods are well de
lineated in standard reference texts such as those by Hillebrand 1 2 3 4 5 et a l . , Bowen , Smales and Wager , Vogel , Snell and Snell , 6 7 8 Welcher * and Morrison . Gravimetric, volumetric, colorimetric and instrumental methods are all included and are compared for 9 sensitivity, cost and degree of difficulty by Siggia . For sensi
tive, multielement determinations instrumental methods are clearly
superior to chemical methods.
Nuclear activation analysis is an instrumental method
of multielement analysis particularly attractive for geochemical
studies because it is highly sensitive, free of interferences from 1C the matrix and involves a minimum of sample preparation and handling.
It is based upon an induced nuclear transmutation which converts a
portion of the stable isotopes of an element into radioactive
isotopesThese produce isotopes that decay to a stable state with the emission of characteristic particles or electromagnetic
radiation. The decay follows a first-order rate law and has a half-
life unique to the isotope. Use of these characteristic properties
allows the identification of an isotope, and a comparison of radiation
4 5 intensities yields quantitative data. Many different parameters may be varied in activation analysis to suit the needs of the analyst and these are well covered in the available literature.^
In general, activation time and decay time are varied in direct relationship with the half-life of the isotope sought, and the choice of activating particle or electromagnetic radiation depends upon the properties of the radioactive nucleus each produces.
Thermal neutron activation analysis is the most widely used form of activation analysis. Almost all of the elements have been determined by this means including the five elements of interest 17-19 here. Since excellent review articles are available, no exhaus tive literature search was made for the years prior to 1968. Each of the elements of interest has been determined by neutron activation followed by radiochemical separation and gamma ray spectrometry. 20 21 Gijbels and Hoste determined gold in osmium and in platinum using 198 the 411.8 keV gamma ray of Au (Ti = 2.698 days) and obtained a 2 sensitivity of 0.1 PPM in both cases. A direct ratio method was used in the latter case to determine the percent of impurity. Oka 22 et al. used an internal reference method to determine gold at the PPB (part per billion) level in meteorites, tektites and standard rocks. A relative standard deviation, of ±2.77. was obtained for amounts of gold ranging from 4.43 x 10" p,g (microgram) to 4.35 x 10 pg.
The detection limit calculated was 0.5 ng. In a previous paper, this 6
group had reported the determination of silver in palladium using
the 657.6 keV and 884.5 keV gamma rays of ^^AgCTi = 253 days) 'Z 111 with the 340 keV gamma ray of Ag(Ti = 7.5 days) as an internal 1: monitor. The latter isotope is produced by the following equation:
110 111 Pd(n,y) Pd(Ti = 22 minutes)
111 Ag
Sensitivities as low as 0.8 PPM with relative errors of ±2% were claimed for the method.
Nominally 99.9999% pure zinc was analyzed for silver by
Mousty et al.^ using ^ ® mAg. (The samples were irradiated for two 13 2 days at a flux of 3 x 10 neutrons/cm /sec). Electrodepositing the silver from solution, they found ''■0.03 PPM of Ag present. The esti mated relative error was 15%. In this case, the 657.6 keV and 884.5 keV gamma ray peaks were also evaluated and compared. Integral 25 gamma counting as well as the method of Covell were used in quan
tizing the peaks.
Hoste et al. have done extensive determinations of trace 26 27 elements in titanium dioxide. * They found 0.0016 PPM of gold *| QQ 1 1 ftm and <0.07 PPM of silver using Au and Ag, respectively. In another study, they determined uranium at the 0.05 PPM level using 239 the 74.7 keV gamma ray of U(T^ = 23.5 minutes). They performed 7
the determination both destructively and nondestructively with the latter being an order of magnitude less sensitive. This same group also analyzed electrolytic zinc sulfate solutions for trace impur ities. They found 0.02 ^g of mercury by measuring the 77 keV gamma 197 ray of = 6 5 hours). Uranium was determined using the
106 keV gamma ray of ^^Np(T, = 2.35 days). This isotope is pro- is duced by the reaction sequence:
^3\(n, y) = 23.5 minutes) %
Uranium concentrations ranging at or below 1 mg/j£ were found and the limit of detection was estimated to be 2 ^g. The determination of tellurium presents special problems in that those isotopes produced in significant amounts yield only very small percentages of gamma rays. The isotope produced in greatest abundance, 131Te, has a half life of only 24.8 minutes and this makes decontamination 28 29 before counting a problem. Hoste and Dams circumvented this 131 problem by using the 364.5 keV gamma ray of = 8.05 days) in coincidence with its 610 keV beta ray. Iodine-131 is produced by 131 decay of Te. The reaction sequence is as follows:
130 , , 131_ Te(n,-Y) w Te .3 J31, 131 Unfortunately, I is also produced by the thermal neutron fission 235 30 of U. The fission yield is 3.1 and quite significant. Calcu lations based upon nuclear data indicated that the presence of 1 PPM of natural uranium in a sample would give rise to an apparent 0.91 PPM of tellurium by this method. Experimentally, however, one PPM of uranium gave rise to an apparent tellurium concentration of 0.79±0.03
PPM. Thus, a separation of uranium was effected prior to irradiation.
Parts per million levels of tellurium were detected.
More than 30 elements in biological material were deter- 31 32 mined by Samsahl ejt al. using rapid group separations and gamma 203 ray spectrometry. They used the 279.1 keV gamma ray of Hg, the
657.6 keV gamma ray of ^ ^ A g and the 106 keV gamma ray of ^^Np, respectively, to determine these elements. A reproducibility of better than ±10% was found. In a very extensive paper Morrison 33 et al. determined 45 elements in U.S. Geological Survey standard rocks using neutron activation analysis, chemical group separations, a high-resolution lithium-drifted germanium detector and a coinci- 34 dence-anticoincidence system. The latter system mentioned is an expensive, effective means of suppressing the compton background in a gamma ray spectrum and will be dealt with later in this survey.
These authors obtained a relative deviation of 6% and sensitivities 197 of less than 1 PPM. They used the 77 keV gamma ray of Hg and the 239 106 keV gamma ray of Np to determine mercury and uranium, re- 239 spectively. The 228.2 keV and 277.6 keV gamma rays of Np were 9
used for confirmation. Limitations of the memory system used dictated that the spectra be divided into three parts in order to
obtain adequate dispersion and take full advantage of the excellent 60 (2.8 keV FWHM for the 1332 keV Co gamma ray) energy resolution of
the gamma ray detector. This necessitated three separate counting periods to obtain a full energy spectrum to 1700 keV. Irradiation
times were also of three different lengths and, though the decay
times used were not specified, those recommended ranged from minutes
to a month for the various elements. Thus, the number of counting
periods was multiplied yet again. No use was made of decay curves
in this study.
Uranium has been determined by thermal neutron activation 35a analysis using a variety of its fission products. Wechter and Voight 135 used = 6.7 hours) which has a 146 keV gamma ray while Ikeda 35b 132 et al. suggested the use of = hours). Both of these 235 isotopes are produced by thermal neutron fission of U and both
have preceding tellurium isobars. These methods, based upon fission
products, were compared to the most commonly used method of deter
mining uranium via fission products, the very meticulous and compre
hensive method of Smales^ based upon the - *"^Ba couple. 37 239 Turkowsky et al. used U(Ti = 23.5 minutes) to determine uranium
in geological materials down to a minimum of 5 ng with an accuracy of about ±5%. 10
Instrumental neutron activation analysis which involves no chemical separation whatsoever became possible with the appear- 38 39 ance of the Nal(Tl) scintillation detector in the mid-1950's. *
The introduction of high resolution Ge(Li) (lithium-drifted ger manium) detectors in about 1965 spurred the development in this area.
In general, the method sacrifices maximum sensitivity for tremendous savings in time and technical skill. Determinations involving extremely short-lived isotopes became possible as well as simul- 40 taneous multielement analyses. Lack of sensitivity and interfer ences due to overlap of gamma ray photopeaks are steadily being eliminated by the continued improvement in efficiency and energy 41 42 43 resolution of Ge(Li) detectors. * *
Instrumental neutron activation analysis has been applied to the determination of silver in commercially available red phos phorus using the 657.6 keV gamma ray of ^ ^ mA g ^ and to determining 45 gold and uranium in witwatersrand ore using the 411.8 keV gamma 198 239 ray of Au and the 277.6 keV gamma ray of Np, respectively. 46 47 48 Pollutants in the air have also been determined by this method. * * 48 Dams et: al. used various different irradiation and decay times to determine 33 elements in the air over East Chicago, Indiana. They used the 411.8 keV, 937.2 keV, and 279.1 keV gamma ray peaks to determine as little as 1 ng of gold, 100 ng of silver and 10 ng of mercury, respectively. Applications to geological samples have 11
49 50 51 seen the determination of 15 ,29 , and 32 elements in single 52 samples. Using epithermal neutrons, Brunfelt and Steinnes deter
mined uranium in rocks at the PPM level. These workers measured the 239 277.6 keV gamma ray peak of Np. They also indicated that use of 239 the 228.2 keV gamma ray peak of Np gave high results attributed
to the 229.3 keV gamma ray of ^^Ta(T, = 115 days). 53 Schmitt jet al. utilized thermal neutrons, 14 MeV (million
electron volt) neutrons and bremsstrahlung of various energies as
activation sources in extending instrumental activation analysis to
its fullest scope to date. They were thus able to take advantage
of the best available nuclear reaction for determining each element.
Since they were ostensibly developing a method suitable for the
analysis of rocks from the lunar surface which were, at the time
(1970), in short supply they were compelled to reuse the same speci
mens in various types of analysis. Thus, a single aliquot of sample was subjected to: 14 MeV neutron activation, 1 minute thermal neu
tron activation, 10 minute thermal neutron activation at low neutron
flux, 10 minute thermal neutron activation at slightly higher flux,
10 minute thermal neutron activation at moderate flux, 15 minute
activation in a highly thermalized neutron flux, 4 hour activation
in a beam of 28 MeV (maximum) bremsstrahlung and a two hour acti- vation at high thermal neutron flux (7 x 10" n/cm /sec), sequentially.
The induced activity remaining after one activation step was either 12
allowed to decay away or neglected before proceeding to the following
step. After the bremsstrahlung activation, the sample was allowed
to decay for one month, then residual activities were measured for
species which would also be produced in the high flux thermal neutron
activation and these were subtracted from the values obtained after
that final activation. Unsatisfactory results were obtained for
magnesium, so this determination was done separately using 23 MeV
bremsstrahlung as the activation source while shielding the sample with cadmium to prevent any neutron activation. The reaction 25 24 23 24 Mg(Y»P) Na was desired and this required that all Na(n,y) Na
be eliminated. With decay times of a month following photon (brems
strahlung) activation and two weeks following high flux thermal neu
tron activation, this analysis consumed considerable time; however,
no use was made of decay curves for analysis. Nor was any effort
made to use the various isotopes produced by different types of
activation to corroborate data from other sources. Each element was
determined by a single, best method of activation. Since the entire
series of procedures was nondestructive, the samples were still
available for other types of analysis and the authors state that the
level of radioactivity at the completion of the analyses was not
dangerously high.
Photon activation analysis using high energy bremsstrahlung
to induce (v,p), (y»a), (y,pn), (y,2n) and predominantly (y,n) reactions 13
has seen slow growth over the years due to the limited availability 54 of photon sources of high flux. A very recent review article
covered all aspects of the subject and negates the need of much
discussion here. The basic theory of photon activation analysis was elucidated by Engelmann"^ who did much of the early work in the
field. Photon activation analysis is most useful as a supplement
to, but not a substitute for, neutron activation analysis. Its
advantages relative to thermal neutron activation analysis were 56 delineated by Andersen et al. as being useful:
(1) where thermal neutron activation of the element
is negligible or very small (e.g. C,N,0), but photon activation is
considerable;
(2) where the photon activation sensitivity is
considerably better than a moderately good thermal neutron sensi
tivity (e.g. F,Fe,Cr);
(3) where the photon activation product is a more
conveniently measured gamma emitter, whereas the thermal neutron
product is a pure, or almost pure, beta emitter (e.g. Si,P,Pb);
(4) where the photon activation product has a more
convenient half-life than does the thermal neutron product;
(5) where photon activation greatly reduces the
interferences from matrix activation (for example, in all sodium-
rich matrices, such as biological materials, glass, etc.); 14
(6) where the matrix produces considerable thermal neutron self-shielding (e.g. samples rich in boron).
Though the elements gold, mercury, silver, tellurium and uranium have not all been determined by photon activation analysis, numerous 57 *• 65 workers have tabulated the interference-free sensitivities for the most likely photon induced reactions along with their appropriate gamma rays. These sensitivities are calculated for bremsstrahlung beams ranging from 20-35 MeV. Higher energy increases the yield of most (.y,n) reactions but it also leads to a greater likelihood of interfering reactions. ^
As mentioned previously, major advances in the use of nondestructive activation analysis have resulted from the continuing improvement in resolution and efficiency of Ge(Li) detectors. Compared to the Nal(Tl) scintillation detector which has an optimum resolution of about 7% (FWHM/energy of the gamma ray peak), the Ge(Li) detector 41 is capable of very high resolution. Heath gives a value of 0.012% 88 for the 1836 keV gamma ray of Y. The detector utilizes a diode of high purity germanium doped with lithium to improve its electrical properties. At high temperature and under strong bias the lithium is diffused into the ingot of germanium. Cooling the ingot to liquid nitrogen temperature and reversing the bias creates a semiconductor in which entering gamma rays cause the formation of electron-hole pairs. The charge collected from these electron-hole pairs is proportional (~3eV/electron-hole pair) to the energy of the incoming gamma ray and is amplified and transferred to the multichannel pulse height analyzer. Even with the early, small, inefficient detectors,
the factor of 10 or more improvement in resolution over scintillation 67 detectors made these devices useful and means were developed to 6 8 compensate for the lack of efficiency. Higher activating fluxes and longer count times were two of the methods used. Improvements
in low noise electronics and multichannel analyzers of sufficient
dispersion to take full advantage of the Ge(Li) detector's high
resolution were soon forthcoming. As solid state gamma ray spectro metry has been refined, other problems have been dealt with such 69 as pulse pileup and detector aging. Above about 400 keV, the Ge(Li) 70 detector is particularly prone to Compton scattering and efforts
to alleviate this problem have led to the development of anti- 23 71-77 coincidence systems to reject the Compton electron. * These
rather sophisticated systems increase the peak to Compton ratio
to about 245:1 (versus about 25:1 for the bare detector). They
involve the use of a large annular detector surrounding the analytical
detector; gamma rays which result from Compton scattering in the
analytical detector yield a simultaneous count in the annulus and
are rejected. In some cases, a severe reduction in photopeak
efficiency is observed but use of an additional multichannel analyzer
memory enables the analyst to retain the unsuppressed spectrum as 16 well as the Compton-suppressed spectrum. Few applications of any of these systems have been reported presumably due to rather high 7 8 cost of the instrumentation. Fagden and Sutherland stated that a single Ge(Li) detector is not adequate to determine completely the radiochemical components of any mixture but that use of an additional detector would enable them to increase the resolving power of the system exponentially. They compared energy values for gamma rays which cascade in coincidence, doing all of their work on a computer.
Instrumental activation analysis yields a very large amount of data which makes the use of computer reduction imperative. A variety of methods of gamma ray peak quantitation were developed 25 79-85 for scintillation spectra * but these are not suitable to analysis of the far narrower peaks found in spectra obtained with a Ge(Li) detector. Another series of methods suitable to deter mining the areas of Ge(Li) detector peaks has appeared due to the 86*100 wide acceptance of these devices. These methods employ various mathematicl representations of the ideal gamma ray peak or measure only a given portion of the peak felt to be most representative. 101 Fortunately, Baedecker has reviewed and compared most of these methods and applied them to the measurement of activities in a 60 chondritic meteorite in the presence of varying amounts of Co activity. Chapter III
Experimental
All chemicals used in this study were of high purity.
Those elements and compounds to be activated were irradiated in neat form in both neutron and photon fluxes. No impurities giving rise to interfering gamma rays were found and an exhaustive analysis was deemed unnecessary. The chemicals used in this study were:
Chemical Formula Description Source Silica sio2 (Floated Powder) Fisher Scientific (about 240 mesh) Company
Gold Oxide A u 2°3 Powder K & K Laboratories Fisher Scientific Mercuric Oxide HgO Powder Company
Silver Ag Powder A.D. Mackay, Inc. Tellurium Electronic Space TeO„ Powder dioxide Products, Inc. Baker & Adamson Quality Uranium Powder Allied Chemical Co. acetate U02(C2H3°2>2' 2H2° General Chemical Division Hydrochloric HCl Analytical Mallinckrodt acid (approximately 37%) Reagent Chemical Works Nitric acid HNO^ Analytical J.T. Baker Chemical (approximately 70%) Reagent Company
Distilled water taken from an all glass still was used throughout this work.
Standard mixtures of the pertinent elements in silica were prepared in powder form. Sufficient material to prepare ten grams of
17 standard mixture containing 1000 PPM (by weight) of the element
(undried) of interest was weighed out on an analytical balance
(Mettler type H6). This was then blended with the appropriate amount of silica (undried) in an agate mortar (courtesy of Dean H.B.
Williams, College of Chemistry and Physics, Louisiana State University,
Baton Rouge, Louisiana) for fifteen minutes. Random samples of these mixtures showed a variation of not more than 20% (at the 10 PPM level) when subjected to neutron activation analysis. Standard samples were prepared for the 1000, 500, 100, 50, 10, 5 and 1 PPM levels for each of the elements of interest. These samples were then weighed out and encapsulated for activation. The weight of standard sample used was constant at 1.5 grams. For activation in the nuclear reactor (Georgia
Institute of Technology, heavy water, approximate thermal neutron flux: 12 1.8 x 10 neutrons/square centimeter/second) the samples were enclosed in polyethylene vials (polyvial, 2/5 dram, Olympic Plastic Company) and heat sealed. These were then shipped to the reactor and activated for a period of 4-14 hours. The intense heat generated by the electron linear accelerator necessitated the use of screw cap glass vials
(12 x 35 mm, 1/2 dram, Kimble Glass Company) for this activation.
Difficulty in filling these vials was overcome by using a small glass funnel in combination with a vibrating engraver. The vials were placed into slots encircling the perimeter of an aluminum disk (12 inch diameter,
1/2 inch thick, milled to reduce mass, 72 slots to the wheel) which was then attached to a 50 RPM constant speed, electric motor and rotated during irradiation in a manner similar to a phonograph record. The samples were placed in the bremsstrahlung beam as close as possible to Glass 0 ° 0 0 0 o O o
.... ^ |
P 00000C>0°°
1 L j - v ------...... ^ " ------' L -J ^ ------^ r - - ~ ^
Figure 1
Aluminum Disk for Linac Irradiation 20 the tungsten-copper target of the linear accelerator. This machine
(Gulf Radiation Technology Division of Gulf Energy and Environmental
Systems Inc.) was then operated for one hour at a maximum electron energy of 30 M ev (million electron volts). The beam current was 600 milliamps, pulse width 4.5 (j,sec, repetition rate 180 pulses per second and average power 14.5 kilowatts.
Following removal from the reactor and a suitable decay period the neutron rich samples were counted in their irradiation vials. The proton rich samples from the linear accelerator activation were trans ferred to 2/5 dram polyvials before counting to reduce interferences from the radioactive glass.
The effectiveness of the method was demonstrated by preparing mixtures of all five elements of interest in various naturally occuring geological matrices. Alluvial soil (dried) was dug from the grounds
surrounding the Nuclear Science Center at Louisiana State University in
Baton Rouge, Louisiana. Several examples of different rocks were obtained from Mr. John Rovik of the Department of Geology, Louisiana
State University. These were crushed in a procelain mortar and multiple
1.5 gram samples were weighed into containers for activation. The glass vials were again used for work with the linear accelerator but for the
reactor larger polyvials (polyvial, 2 dram, Olympic Plastics Company) were used to contain liquid to be added later.
Solutions of each of the elements were prepared in suitable
solvents. Uranium acetate was dissolved in distilled water (0.0267 gm
in 25.00 ml), gold oxide in dilute HC1 (0.0168 gm in 100.00 ml), mercuric
oxide in dilute HG1 (0.3247 gm in 100.00 ml), silver powder in dilute HNO^
(0.2531 gm in 25.00 ml), and tellurium dioxide in dilute HNO^ (0.1407 gm in 25.00 ml). All volumetric flasks used were class A in quality. The
concentrations of these solutions were calculated to yield minimum determinable amounts of each element for a single drop when absorbed on the solid matrix. The solutions were added dropwise to the vials of
solid material using a 10 ml buret. Samples received from one to ten
free-falling drops of each solution. The buret was then calibrated using distilled water and found to give 22.54 drops per milliliter. The mixture samples were then handled in a manner similar to that used with
the standard samples except that the samples in glass vials were dried very carefully in an oven before being transferred to polyvials for
counting. Losses incurred in transfer were nullified by back weighing
the thoroughly dried material after counting and adjusting the specific mass counted accordingly.
All samples were counted on a lithium drifted germanium gamma ray spectrometer system, model 7249, S/N 069, five-sided drifted detector with rectangular cross section (34 x 28.5 ram), p-core: 16:10mm; 16 mm behind window, dimensions: length: 55 mm, weight 285 gm, active area 2 facing window: 18.7 cm , Canberra Industries, Inc. A one inch thick
lucite plate was cut to fit the window surface of the detector and a hole was cut to 1/8 inch thickness in the center to accept and position the
sample. This plate served to absorb the |3 particles emitted by the
sample and to provide a fixed and reproducible geometry for the polyvials when counting.
The energy resolution of this system was as good or better
than that specified by the manufacturer (see Table 1). 22 Table 1
Energy Resolution of Gamma Bay Spectrometer*
137 . 60 88 Isotope 57Co Cs Co Y 228Th
Energy OkeV) 122 662 1332 1836 2614
FWHM (keV) 2.75 3.1 3.5 4.0 4.85
FW .1M (keV) 5.2 5.9 7.0 7.9 10.0
Peak/Compton --- 18:1 12:1 11:1 9:1
(where keV = thousand electron volts; IWHM s full width of the full energy peak at half its maximum height; FW . 1M = full width of the full energy peak at one tenth its maximum height)
* Instruction Manual, Canberra 7000 Series of Ge(Li) Spectrometer Systems, Canberra Industries, p.7.
The efficiency of the detector as compared to a standard 3 inch x 3 inch
sodium iodide-thallium detector was given in the following table as a ratio of counts measured on the Ge(Li) detector versus those measured on Nal(Tl).
Table 2
Experimentally Determined Values of Relative Efficiency
of the Ful 1-Energy Peak fla'^T l )
Isotope 57Co 203Hg 22Na 137Cs 6°Co 6°Co
Energy (keV) 122+ 137 279 511 662 1173 1332
Erel (%) 23.7 12.0 7.4 6.5 6.3 5.9 23
The output signal from the gamma ray spectrometer was fed into either a 400 channel (model 401D, Technical Measurements
Corporation) or a 1024 channel (model 161F, Nuclear Data Company) analyzer. Most of the preliminary work was done using the 400 channel analyzer but the analysis of neutron irradiated samples and standards listed herein was done on the 1024 channel analyzer
(courtesy of Dr. Edward F. Zganjar, Department of Physics, Louisiana
State University, Baton Rouge, Louisiana). The background radiation
from natural sources was reduced when using the 400 channel analyzer
by shielding the detector with at least two inches of lead (as bricks). Data from the 400 channel analyzer was read out by means
of a Franklin printer and then punched onto computer cards as
necessary. Data from the 1024 channel analyzer was read out by
means of a paper tape perforator (model SO 420, Tally Corporation)
and transferred to computer cards by means of a tape-to-cards key
punch (model 410, International Business Machine Corporation). All
computer programs were run on ah IBM 360-60 computer at the Louisiana
State University. Chapter IV Experimental Procedures, Data and Results
The vast amounts of data generated in multielement
analysis of many samples make use of computer methods of data
reduction imperative. Consequently, several of the available 87 97 98 100 programs * * * were obtained and evaluated as to suitability.
The program selected was named GAUSS and was in actual use with
the computer at the Louisiana State University.
The program, GAUSS, is based upon the assumption that
the gamma ray photopeak approximates a Gaussian statistical shape
(actually Poisson statistics apply in this case but the less
accurate--but more convenient— Gaussian statistics are customarily 102 used). It carried out a non-linear least-square fit of one or
more modified gaussians to a set of data. The expression was used
J— Ax-x *“|
U /2/ln2“* r o !. Y = Y e [l+a1(x-xo > 1+Qf2(x-xo)ni2] o
where Y = ordinate; Yq = initial ordinate x = abscissa; x s center of the Gaussian o W 0 s BWHM 0^ 2 = parameter modifying Gaussian m^ 2 = power influencing non-Gaussian tails of peaks
This program was derived from that presented by Helmer et al. in references 97 and 98 and was modified by G. Keller, M. Walton and D. Copeland all of whom were in residence at the Louisiana State University. 24 25 for each component peak. The contribution to the peak from background radiation was removed by observing the boundary channels of the peak (channels wherein the number of counts per channel ceases to decrease), averaging the number of counts in these two channels and feeding this number to the computer which was instructed to substract it from each channel under the peak. After a series of peak fits to obtain the optimum value, the area of the peak was computed. A variety of options were included in this program including doublet and triplet fitting routines for resolving over lapping peaks but these were never used in practice. When the 400 channel analyzer was used the read out was in the form of printed numerical values on a paper ribbon. These values were manually evaluated for peak areas for the gamma rays of interest. Scanning the energy range from 0-800 keV necessitated the use of a channel width of 2 keV per channel. The peaks of interest were then identified by using this channel width in conjunction with the gamma ray energy of the pertinent nuclide. The boundaries of the peak were determined by including every channel extending from the center of the peak outward until the number of counts in a channel ceased to decrease. The channel with the minimum number of counts at each edge of the peak was then taken as indicative of the background for that energy region. These two channels were averaged and that average was multiplied by the number of channels 26 within the peak. This value was then subtracted from thq sum of all of the counts in all of the channels within the peak.
Experience and ingenuity were brought into play in some exceptional
cases but the procedure was generally as outlined. This method
of summing total peak counts was found to agree within 57o with the values obtained from the computer program GAUSS (for peak areas of
200 counts or more).
The efficiency of the Ge(Li) detector decreases with
increasing gamma ray energy as may be seen from Table 2. Aging 69 also causes a gradual decrease in efficiency. However, since
these measurements were all made on the same detector and within
a relatively short period of time, no corrections were applied.
Pulse pileup, peak distortion and diminished response due to very
high specific activity were controlled by maintaining the dead
time of the multichannel analyzer at or below 5%.
Gamma ray spectra for each of the elements irradiated with neutrons and photons are presented in Figures 2 through 11.
Concentration curves for all species determined are
shown in Figures 12 through 21. The curves for '*'^mHg(Ti - 24 hours) -2 203 and for Hg (T^ - 46.9 days) shown after three week decay are
included as part of special consideration given to determination of
this element via the C^n) reaction.
Each element was determined by using an isotope produced
in quantity, having a half-life on the order of days and possessing 10 9- 355.7 keV 196. 7- Au
5 -
4-
2-i
4 10 ¥— 3—
J-
3 0 9- B-
7-
6 -
4 -
3-
2-
100 200 600 G a m a Bay En«irty (keV)
Figure 2 Gamma Ray Spectrum of Gold 5 Days after Irradiation with Photons Counts 0 0 3 2 Gamma Ray Spectrum of Mercury 5 Days after Irradiation with Photons with Irradiation after 5Days Mercury of Spectrum Ray Gamma 2 - s 4- e- 7 0 9 3 100 ------134.0 keV 134.0 w n 7 9 1 o d a am a nry (keV) Energy Ray Gamma 7. keV 279.1 o d J 203,. Figure 3 Figure
v. 0
0 Counts 0 2 3 Gamma Ray Spectrum of Silver 5 Days after Irradiation with Photons with Irradiation after 5Days Silver of Spectrum Ray Gamma 3 4 4- ~ S 3 2 2 2 r- 3- 7 7 9 6— e------280.4 keV 280.4 3$s. Ganna Ray Energy (keV) Energy Ray Ganna
iue 4 Figure 344*4 keV 344*4 e f l
511/6 keV 511/6 106m.
1 cf f3o 20*0 306 4?)0 3^0 6^0 Gasma J8ay Energy (keV)
' ■ • i&tgufe 5 Gamma Ray Spectrum of.Tellurium.5 Days after Irradiation with Photons Counts 10 0* o '3 4 Gamma Ray Spectrum' of Uranium 5 Days after Irradiation with Photons with Irradiation after Days 5 Spectrum' Ray Uranium of Gamma <4 3 3- S 9 6- Z- 7 7 v 6 8 100 - — - - -
Gamma Ray Ray Sste$sy(keV) Gamma 300
iue 8 Figure boo 300 31 600 9- 8— 7- 6— S—
4-
2-
10 100 20*0 300 ^oE 500 600 Gamma Ray Energy (keV)
Figure 7 Gamma Ray Spectrum of Gold 10 Psye after Irradiation with Neutrons 10 f-
7-
4 -
2-
o4 ?- a-
7-
J-
2—
3 0 7 - S_
7 -
6 —
4-
2 -
2 0 1 0 6 5 0 0 600 Gena? Say Energy (keV)
. Figure. 8 Ganuna Ray Spectrum of Mercury 10 Days after Irradiation with Neutrons 657.6 keV U O n A
884.5 keV
2.— 937.4 keV 110m A
0
9 - a~
7—
•3"—
3- O
3 0 7- a—
7— 6~ S-
4 -
«-
2 O' 600 gOO $00 fooo 1200 Garrana Hay Energy (keV)
Gamma Ray Spectrum of Silver 10 Days after Irradiation with Neutrons V--1
364.5 keV 131-
3 -
a—
of ?-
7-
6 -
S-
1-
3 -
Z-
0s
7- *- 4T-
4 -
3 -
,2 0 100 200 300 ZfOO 5 0 0 600 Gamma Ray Energy (keV)
Figure 10 Gamma Bay Spectrum of Tellurium 10 Days after Irrediation with Neutrons 2-
228.2 keV 239.. 10 _ 277.6 keV 8- 239i. 7—
6 —
5 - 4-
3 -
9-
8-
7-
4-
3-
Z~
100 600 Gambia Ray Energy CkeV)
Figure 11 Gamma Ray Spectrum of Uranium 10 Days after Irradiation with Neutrons Counts dL id ~ 2 2 3~ 3 s- - - Calibration Curve - Gold LINAC Gold - Curve Calibration Concentration (PPM) Concentration iue 12 Figure Counts _ 0 2 - S 3~ 4— 6 7 8~ 3- 9 - - - - Calibration Curve - Mercury LINAC -Mercury Curve Calibration ocnrto (PPM) Concentration iue 13 Figure 38 Counts 10 _ - 3 8 - Z 9 6 - - - Calibration Curve - Silver LINAC Silver - Curve Calibration Concentration Concentration Figure 14 Figure (PPM) * 0 1 x 5 Counts - n 8 9- - Calibration Curve - Tellurium L1NAC Tellurium - Curve Calibration Concentration Concentration iue 15 Figure (PPM) Counts 1 dL idL ~ z 3 2 - - airtQ uv - Uroftiuid - Curve CalibratiQn LINAC ocnrto (PPM) Concentration iue 16 Figure Counts 10 2 A — 4 S- 2 7 3 2~ 3 '— > £ 8 _ a— 7 8- 9- 6 1 — - ~ — - — - - - - airto uv - od Reactor Gold - Curve Calibration ocnrto (PPM) Concentration iue 17 Figure Count s 10 10 _ _ 3 S 4— J — 8 6— 9 2 3 6- 7 f- 3 9~ 9 — — — ------
Calibration Curve ^ Mercury Reactor ^ Mercury Curve Calibration Concentration (PPM) Concentration iue 18 Figure Counts 10 2 - 7 airto uv -* Curve Reactor Silver Calibration ^ ocnrto (PPM) Concentration Figure 19 Figure J I'n 8 Counts 10 _ 3 - 2 3 4 3- a •t ------Calibration Curve - Tellurium Reactor Tellurium - Curve Calibration 0 ^ 10 ocnrto (PPM) Concentration iue 20 Figure
Counts 1 1 1 1 - s 2 4 - 6 - 3 .6 tf — 2~ 3 9 1 - 3 v~ 6 7 - 4 8 * - 7- 2 H - ■ f — ------
Calibration Curve - Uranium Reactor Uranium - Curve Calibration ocnrto (PPM) Concentration iue 21 Figure 46 47 at least one abundant gamma ray moderately free of Interferences.
The nuclear data for the Isotopes chosen are given in Table 3. 103 All values were taken from the Table of Isotopes. Exact (y,n) and (-Y,2n) cross section values at 30 MeV were not available but are known to be of the order of millibarns for all elements and show an increase with atomic number.
Table 4 lists the nuclear data for all potential interferences of any consequence. Isotopes with extremely weak gamma rays, those with half-lives of less than a few hours and those with very long half-lives are not included. Five refer- 104.105.106.107.108 , , , ^ ences * * * * were thoroughly searched for gamma rays within ± one multiple of the resolution of the detector of the gamma ray of interest. Overlap from peaks within this range may still be resolved but the doublet fitting routine will more than likely be required.
Most interferences were either circumvented or were felt to be insignificant. The decay time used for neutron irradiated samples was 9-11 days. That for photon irradiated samples was 3-6 days. At these decay times, some interferences persisted. They were dealt with individually as follows:
^Se: This isotope may be produced in either neutron
or photon irradiation and possesses gamma rays
of 264.6 keV and 279.6 keV. The latter, which
interferes with the determination of mercury, Table 3 Nuclear Data for Selected Isotopes
Isotopic Reaction Reaction Parent Radioactive Half Gamma Ray Energy Abundance of Gross Section Isotope Isotope Life (keV) (%) Interest (barns) 198. 197Au 100.00 98.8 Au 2.697 days 411.8
202ng 29.80 4 - 203Hg 46.9 days 279.1
l09Ag 48.65 n,Y 3 U % g 253 days 657.6 l30Ie 34.49 n»Y 0.2 13^ 24.8 mins. * 1 3 1 8.05 days 364.5
238 239 u 99.28 2.73 23.5 anins.j 239.7 Np 2.346 days 228 , 277.6
196. Au 100.00 V»n Au 6.18 days 355.7 204„ Hg 6.85 Y»n 203Hg 46.9 days 279.1
1 07Aga„ y, n l05Ag 40 days 280.4 , 344.4 122 121 Te Y,n Te 17 days 573.1 238.. 237u b Y,n 6.75 days 208.0
198„ Hg 10.02 Y,n 197mHg 24 hours 134.0 Table 4 Potential Sources of Interference
Isotopic Reaction Reaction Parent Radioactive Half Gamma Ray Abundance of Gross Section Remarks Isotope Isotope Life Energy (keV) . (%) Interest (barns') (A) Isotopes Interfering with the 228.2 keV Gamma Ray of ^ N p f T , = 2.346d} -2 181Xa 99.98 (n,v) 21 182Xa 115d. 229.3 A 174Kf 0.163 (n»v) 400 175Hf 70d. 229.6 A 114Cd 28.86 (n,y) 1.1 ll5Cd 53h. 230 G , A 94, Zr 17.40 (n,y)-£ 0.08 95" W 90h. 235 C , R 142 Ce 11.07 (n,y) 1 l43Ce 33h. 232 C , A , R 132 Xe 26.89 (n,y) 5 133"Xe 2.26h. 232.8 R 184 Os 0.018 (n »v) 200 1850 s 94d. 233.4 A , I , E 235 0.720 (n»f ) 577 132Ie 78h. 230.0 B 203 (B) Isotopes Interfering with the 279.1 keV Gamma Ray of Hg(T^ = 46.9d)
132Ba 0.097 (n,y) < 0.2 133mBa 38.9h. 275.7 I , C 146Nd 17.18 (n,y) 2 147Nd 1 1 .Id. 275.4 R , A 238d 99.28 (n,y)—( N 3‘ * 2.73 239h p 2.346d. 277.6 Persistent, see
l96Hg 0.146 ( n.,y) 25 203Hg 24h. 279.3 C , T 74Se 0.87 (n,y) 30 75Se 121d. 279.6 Persistent, see
1920 a 41.0 (n.» y ) 1.6 1930 s 31h. 278 A , T 174Yb 31.84 (n,y) 55 175Yb lOlh. 282.6 A 191Ir 38.5 (n,v) 1000 192lr 74d. 283.4 A , R
196Pt 25.2 ___ foxXl.... 0.95 197Pt 18h. 279 T 4 C , A Table 4 (Continued)
Isotopic Reaction Reaction Parent Radioactive Half Gamma Ray Abundance of Cross Section Remarks Isotope Isotope Life Energy (keV) (%) .... Interest (barns) (C) Isotopes Interfering with the 364.5 keV Gamma Ray of 131I(T, = 8.05d)
1920 s 41.0 (n,Y) 1.6 l930 s 31h. 362.0 T , A 102Pd 0.96 (n >Y> 4.8 103Pd 17d. 365 A
158Gd 24.9 (n,Y) 3.4 158Gd 18h. 363.2 T 183_ Ta unstable (n ,Y> 8000 Ta 5.Id. 365.6 D 102_ 103_ Ru 31.6 (n,Y) 1.4 Ru 39.6d 366 A 76Ga 7.67 (n,Y) 0.1 77Ge 1 1 .3h. 367 C , T 198, V UJ ^ 0 V b V K w O 4 . ^ ^ J. 1 i v * y v i . • v y v u j ------l9°pt 0.0127 (n, Y> 150 l91pt 3.0d. 409.9 A , I
l82Ia unstable (n, y ) 8000 183Ta 5.Id. 406.6 D , R 232 228Th unstable natural decay from Th 224Ra 3.64d. 41 x 10 A 108Pd 109Pd 26.7 (n,Y> 12 13.5h. 41 x 10 T , A 1 A1 4192„ A A Ir 38.5 (n,Y) 1000 Ir 74d. 416.6 A , R 76Ge 7.67 0.1 77Ge llh. 417 T 4 p A (n3 Y) R , B^fsm__ ___ 26.63__ ...... 210 153Sm 46.8h. 411.5 A
Ln O Table 4 (Continued)
Isotopic Reaction Reaction Parent Radioactive Half Gamma Ray Abundance of Cross Section Remarks Isotope Isotope Life Energy (keV) (7.) Interest (barns) (E) Isotopes Interfering with the 657.6 keV of Gamma Rav of * ^ mAg(Ti = 253d) '2
75A s 100 (n,-y) 4.5 76A s 26.4h. 657.4 T , A
148Nd 5.72 (n,v> 4 149Nd 1 .8h. 654 T , A 50Cr 4.31
(F) Isotopes Interfering with the 208.0 keV Gamma Ray of 237U(T, = 6.75d) "2 192t 193Ir 61.5 (\»n) Ir 74d. 205.7 A 184. Os 0.018 (Y,n) 5C- > 183Re 71d. 208.8 I 80 Kr 2.27 W»n) 79Kr 34.9h. 208.6 A 185« Re 37.07 (\»n) 18V 38d. 216.2 A , R 122 Te 2.46 (■y»n) 121inTe 154d. 212.2 L , R Table 4 (Continued)
Isotopic Reaction Reaction Parent Radioactive Half Gamma Ray Abundance of Cross Section Remarks Isotope Isotope Life Energy (keV) (%) Interest (barns) (G) Isotopes Interfering with the 279.1 keV Gamma Rav of 203H8 (T, . 46.9d)
13V 0.101 (Y,n) 129CS 32h. 278 A , I 76Se 9.02 (V»n) 75Se 121d. 279.6 L , see text Ba 2.42 (Y»n) 133mBa 38.9h. 276 A , R 198Hg 10.02 (Y»n) 197"Hg 24h. 279.3 A i76W> 12.73 (y»n) 175Ib lOlh. 282.6 A , R 204Pb 1.40 (Y,n) 203Pb 52.1 279.1 G
iU7Ag 51.35 (V,2h) l°5Ag 40d. 280.4 Persistent, see text
(H) Isotopes Interfering with the 344.4 keV Gamma Rav of 105Ag(Tv . 40d) "2 160Gd 21.9 (Y»n) 159w 18h. 348.0 A , T 160_ Dy 2.294 (Y,n) 15V 144d. 348.0 A , L Eu 52.23 (Y»n > 152"feu 9.3h. 344.2 A , T 235 d 0.72 (v,fH C 111^ 7.5d. 340 R , F 2 3 8 d 99.28
Isotopic Reaction Reaction Parent Radioactive Half Gamma Ray PomaT.Vg Abundance of Cross Section Isotope Isotope Life Energy (keV) ^ .. „.a>_____ Interest (barns') 196 (I) Isotopes Interfering with the 355.7 keV Gamma Rav of Au(T, = 6.18d) 2
74Se 0.87 (•y»n) 73se 7. lh. 359 T , A , I l74Hf 0.163 W»n) 173H£ 23.6h. 357 I , T
U 6 Cd 7.58 (Y»n ) U 5 m Cd 43d. 355 A 104Ru 18.87 (Y»n) 103Ru 39.6d. 357 A
(J) Isotopes Interfering with the 573.1 keV Gamma Ray of 121Te(Ti = 17d) ■2
76Se 9.02 Ul 00 Table 4 (Continued) (a) Code for Symbols: A = The isotope produces the interfering gamma ray in very low abundance, primarily decaying by other means. This interference may be ignored. B = The isotope is produced from the same element as the isotope of interest and has a similar half-life. Production of “Ce amounts to approximately 6% of the ^ % p produced. C = The reaction producing this isotope has a very low cross section and therefore only a small amount of the isotope is produced. This interference may be ignored. D = This interference may be disregarded except for work involving very long irradiations (days) as it is produced by a secondary reaction from ^^^-Ta. F = Low fission yield. 6 = When present in great amount, a three week decay time becomes necessary. H = When present in quantity, a two week decay time may be required. I s The interfering isotope is produced from a stable isotope which has a very low isotopic abundance. This interference may be ignored. P = When present, choice of another gamma ray becomes necessary. R s The gamma rays of this isotope and the isotope of interference are resolved by the Ge(Li) detector. T = The interfering isotope has a half-life sufficiently short to allow essentially complete decay (10 half-lives) before counting. 55 is 39.9% as abundant as the former. Since the 264.6 keV gamma ray is relatively inter ference free, it was measured and 39.9% of its area (if any) was subtracted from the peak at 279 keV. Produced in the photon flux, this isotope also interferes with the determination of mercury. It can be corrected for by sub tracting the measured area of the peak at 3 4 4 . 4 keV from the 279 keV peak. The 344.4 keV and 280.4 keV gamma rays of ^^Ag produce equally abundant peaks. 239 Np: Produced in the neutron flux, this isotope also interferes with the determination of mercury. Correction for this error was obtained by subtracting 69.2% of the area of the 228.2 keV gamma ray peak from the 279 keV peak. 131 I: This isotope is produced as an interference 235 by the thermal neutron fission of U. OQ Hoste et al. calculated the error caused in the apparent concentration of tellurium to be 0.91 PPM of Te per PPM of U. They observed a vajLue of 0.79 PPM of Te per PPM of U. In this work, the area values for the 228.2 keV 239 gamma ray peak of Np and the 364.5 keV 131 gamma ray peak of I were corrected to zero decay time. Then an experimentally determined percentage (3.06%) of the 228.2 keV peak was 131 subtracted from the I peak area. A supplementary computer program (included herein as Appendix I) was written to correct all peak areas to zero decay time, calculate a concentration fot each element for both neutron and photon irradiations, combine the two concentrations and yield a final result. An effort was made to reflect the varying sensi tivities for the different elements under the two conditions of irradiation by using a sensitivity factor in weighting the results. These factors were experimentally determined and are based upon relative peak areas at the optimum time of counting, not zero decay time. The times chosen were 10 days after irradiation for reactor products and 3 days after irradiation for LINAC products. An effort was also made to reflect the fact that peaks from higher energy gamma rays tend to yield more reliable data due to a diminished Compton background. Several different factors were used in weighting the gamma ray energy values and all results are presented. The final equation used had the form: Concentration Reported = ~ 1 t o In this equation, the following symbols are defined: I C.^ - concentration of the element derived strictly from LINAC data. = concentration of the element derived strictly from reactor data. S = sensitivity factor for the element in the reactor K flux. = sensitivity factor for the element in the LINAC flux. = gamma ray energy of the isotope used to determine the element after reactor irradiation. yT - gamma ray energy of the isotope used to determine Xj the element after LINAC irradiation. F = exponent in the power series. Table 5 DATA FOR GOLD WEIGHTED CONCENTRATION RESULTS FROM LINAC AND REACTOR DATA SAMPLE CONCENTRATIONS (PPM) EXPONENTS OF THE GAMMA RAY ENERGY USED IN WEIGHTING NUMBERS LINAC REACTOR Spike Added 0.5______UO ______2.0 4.0 Pleistocene Alluvial Soil 301 20.83 16.25 17.7 17.46 17.45 17.45 17.43 302 35.25 46.44 44.3 43.48 43.49 43.51 43.55 304 37.82 33.61 31.0 34.72 34.72 34.71 34.70 305 6.31 3.45 4.4 4.21 4.21 4.20 2.19 306 22.02 19.14 22.1 19.90 19.90 19.89 19.89 307 23.30 34.41 35.4 31.47 31.48 31.50 31.54 308 17.60 27.19 26.6 24.65 24.66 24.68 24.71 309 22.72 16.43 8.9 18.10 18.09 18.08 18.06 310 13.01 10.63 13.3 11.26 11.26 11.26 11.25 311 0.34 0.02 0.11 0.11 0.11 0.11 Gabbro (an igneous rock) 312 6.51 7.00 8.9 6.87 6.87 6.87 6.87 313 17.10 14.44 17.7 15.15 15.14 15.14 15.13 314 9.78 11.75 13.3 11.23 11.23 11.23 11.24 315 25.49 21.63 26.6 22.65 22.65 22.64 22.63 316 20.60 22.69 22.1 22.14 22.14 22.15 22.15 317 29.71 26.68 31.0 27.48 27.47 27.47 27.46 318 4.65 4.76 4.4 4.73 4.73 4.73 4.73 319 34.16 33.82 35.4 33.91 33.91 33.91 33.91 320 47.42 46.35 44.3 46.64 46.64 46.63 44.63 321 23.22 46.55 39.9 40.37 40.40 40.44 40.51 322 0.14 0.01 0.05 0.05 0.05 0.05 00 (Continued) CONCENTRATIONS (PPM) EXPONENTS OF THE GAMMA RAY ENERGY USED IN WEIGHTING LINAC REACTOR Spike Added______CK5______LO ______2^0______4.0 Arkose (a sedimentary rock) 323 14.80 11.47 13.3 12.35 12.35 12.34 12.33 324 38.43 35.33 39.9 36.15 36.15 36.14 36.13 325 23.55 33.91 31.0 31.17 31.18 31.20 31.23 326 13.81 16.01 17.7 15.43 15.43 15.44 15.44 327 17.59 22.68 22.1 21.33 21.33 21.34 21.36 328 3.68 3.57 4.4 3.59 3.59 3.59 3.59 329 20.26 21.86 26.6 21.44 21.44 21.44 21.45 330 20.38 36.69 35.4 32.38 32.39 32.42 32.47 331 5.28 7.99 8.9 7.27 7.27 7.28 7.28 332 50.40 39.56 44.3 42.43 42.42 42.40 42.36 333 0.27 0.02 0.09 0.09 0.08 0.08 Quartz Diurite (an igneous rock) 334 7.32 3.98 4.4 4.86 4.86 4.85 4.84 335 43.11 31.76 39.9 34.77 34.76 34.73 34.70 336 23.57 21.55 22.1 22.08 22.08 22.08 22.07 337 16.83 11.73 13.3 13.08 13.08 13.07 13.05 338 35.19 40.77 35.4 39.29 39.30 39.31 39.32 339 28.63 25.46 31.0 26.30 26.30 26.29 26.28 340 19.68 21.94 26.6 21.34 21.35 21.35 21.36 341 8.86 9.01 8.9 8.97 8.98 8.98 8.98 342 45.25 46.19 44.3 45.94 45.94 45.94 45.94 343 17.54 15.49 17.7 16.03 16.03 16.03 16.02 0.78 0.03 0.23 0.23 0.22 0.22 Ln VO Table 5 (Continued) SAMPLE CONCENTRATIONS (PPM) EXPONENTS OF THE GAMMA RAY ENERGY USED IN WEIGHTING NUMBERS______LINAC REACTOR Spike Added______(L5______LO ______2j0______4.0 Granite (an igneous rock) 345 20.03 22.25 22.1 21.66 21.66 21.67 21.67 346 3.29 4.65 4.4 4.29 4.29 4.30 4.30 347 11.40 15.33 13.3 14.29 14.30 14.30 14.32 348 33.48 33.64 44.3 33.60 33.60 33.60 33.60 349 15.72 18.58 17.7 17.82 17.82 17.83 17.84 351 22.12 35.08 35.4 31.65 31.66 31.69 31.72 352 5.55 8.58 8.9 7.78 7.78 7.79 7.80 353 17.17 24.80 31.0 22.78 22.79 22.80 22.82 354 18.22 24.88 26.6 23.12 23.13 23.14 23.16 355 0.28 0.01 0.08 0.08 0.08 0.08 SAMPLE 303 LINAC DATA ABSENT **** SAMPLE 350 LINAC DATA ABSENT **** : M M “A-A-A"A-^ O' o Table 6 DATA FOR MERCURY WEIGHTED CONCENTRATION RESULTS FROM LINAC AND REACTOR DATA CONCENTRATIONS (PPM) EXPONENTS OF THE GAMMA RAY ENERGY USED IN WEIGHTING LINAC REACTOR Spike Added 0.5______1 ^ ______2^0______4.0 Pleistocene Alluvial Soil 675.99 138.09 177.5 285.02 285.02 285.02 285.02 302 770.31 511.17 443.7 581.95 581.95 581.95 581.95 304 795.31 118.27 88.7 303.20 303.20 303.20 303.20 305 740.49 409.15 355.0 499.65 499.65 499.65 499.65 306 L623.28 701.87 710.0 953.55 953.55 953.55 953.55 307 838.93 335.90 266.2 473.30 473.30 473.30 473.30 308 922.85 919.71 798.7 920.57 920.57 920.57 920.57 309 L116.34 1000.59 887.5 1032.20 1032.20 1032.20 1032.20 310 674.69 610.45 621.2 628.00 628.00 628.00 628.00 311 428.77 0.22 117.28 117.28 117.28 117.28 Gabbro (an igneous rock) 312 155.90 180.37 177.5 162.76 162.76 162.76 162.76 313 35.55 668.67 710.0 495.74 495.74 495.74 495.74 314 438.25 562.78 621.2 528.76 528.76 528.76 528.76 315 603.60 406.01 443.7 459.98 459.98 459.98 459.98 316 881.64 1018.76 887.5 981.30 981.30 981.30 981.30 317 440.71 411.03 532.5 419.14 419.14 419.14 419.14 318 624.27 1043.94 798.7 929.31 929.31 929.31 929.31 319 257.30 326.77 266.2 307.80 307.80 307.80 307.80 320 75.59 126.26 88.7 112.42 112.42 112.42 112.42 321 69.88 482.10 355.0 369.51 369.51 369.51 369.51 0.0 4.59 3.34 3.34 3.34 3.34 Table 6 (Continued) SAMPLE CONCENTRATIONS (PPM) EXPONENTS OF THE GAMMA RAY ENERGY USED IN WEIGHTING NUMBERS LINAC REACTOR Spike Added 0.5______UO ______2;0______4.0 Arkose (a sedimentary rock) 323 724.16 603.80 710.0 636.67 636.67 636.67 636.67 324 558.59 571.01 621.2 567.62 567.62 567.62 567.62 325 341.32 520.58 443.7 471.61 471.61 471.62 471.62 326 173.66 168.82 177.5 170.14 170.14 170.14 170.14 327 274.18 284.22 266.2 281.47 281.47 281.47 281.47 328 169.13 83.71 88.7 107.04 107.04 107.04 107.04 329 583.57 819.61 887.5 755.13 755.13 755.13 755.13 330 273.79 436.35 355.0 391.95 391.95 391.95 391.95 331 328.41 495.63 532.5 449.95 449.95 449.95 449.95 332 925.31 803.94 798.7 837.09 837.09 837.09 837.09 333 0.0 0.0 0.0 0.0 0.0 0.0 Quartz Diurite (an igneous rock) 334 840.35 864.64 798.7 858.00 858.00 858.00 858.00 335 1001.19 779.61 887.5 840.13 840.13 840.13 840.13 336 626.96 182.66 177.5 304.02 304.02 304.02 304.02 337 466.81 339.49 355.0 374.27 374.27 374.27 374.27 338 240.99 321.64 266.2 299.61 299.61 299.61 299.61 339 280.59 418.85 443.7 381.08 381.08 381.08 381.08 340 0.0 96.44 88.7 70.10 70.10 70.10 70.10 341 617.91 737.02 621.2 704.48 704.48 704.48 704.48 342 763.32 863.74 710 0 836.31 836.31 836.31 836.31 343 1032.07 766.35 798.7 838.93 838.93 838.93 838.93 344 26.68 0.28 7.49 7.49 7.49 7.49 O' ho Table 6 (Continued) SAMPLE CONCENTRATIONS (PPM) EXPONENTS OF THE GAMMA RAY ENERGY USED IN WEIGHTING NUMBERS LINAC REACTOR Spike Added 0.5______UO ______2^0______4,0 Granite (an igneous rock) 345 1079.99 899.25 887.5 948.62 948.62 948.62 948.62 346 154.98 222.23 177.5 203.86 203.86 203.86 203.86 347 670.84 995.18 798.7 906.59 906.59 906.59 906.59 348 234.84 314.90 355.0 293.03 293.03 293.03 293.03 349 170.47 107.29 88.7 124.55 124.55 124.55 124.55 351 259.63 721.64 621.2 595.45 595.45 595.45 595.45 352 473.52 530.01 443.7 514.57 514.57 514.57 514.57 353 385.39 479.47 532.5 453.77 453.77 453.77 453.77 354 437.35 332.58 266.2 361.19 361.19 361.19 361.19 355 0.0 0.0 0.0 0.0 0.0 0.0 SAMPLE 303 LINAC DATA ABSENT **** SAMPLE 350 LINAC DATA ABSENT **** On CO Table 7 DATA FOR SILVER WEIGHTED CONCENTRATION RESULTS FROM LINAC AND REACTOR DATA CONCENTRATIONS (PPM) EXPONENTS OF THE GAMMA RAY ENERGY USED IN WEIGHTING LINAC REACTOR Spike Added 0.5______UO ______2J3______4.0 Pleistocene Alluvial Soil 301 1516.98 1146.13 1197.8 1249.48 1246.67 1243.02 1240.01 302 551.45 719.22 598.9 672.47 673.74 675.39 676.75 304 1092.62 1148.88 898.3 1133.20 1133.63 1134.18 1134.64 305 1875.07 1395.07 1197.8 1528.83 1525.19 1520.06 853.23 306 837.63 858.51 898.3 852.69 852.85 853.06 853.23 307 118.99 370.91 299.4 300.70 302.61 305.09 307.14 308 320.73 737.33 598.9 621.23 624.39 628.48 631.87 309 1142.86 1456.70 1197.8 1369.24 1371.62 1374.70 1377.25 310 895.61 845.05 898.3 859.14 858.75 858.26 857.85 311 0.0 1.94 1.40 1.41 1.43 1.45 Gabbro (an igneous rock) 312 799.23 1171.86 1197.8 1068.2 1070.85 1074.51 1077.54 313 181.45 588.75 598.9 475.25 478.34 482.34 485.65 314 469.42 980.41 898.3 838.01 841.89 846.91 851.06 315 312.49 555.00 598.9 487.42 489.26 491.64 493.61 316 724.62 1076.84 898.3 978.69 981.36 984.82 987.68 317 329.48 369.63 299.4 358.44 358.74 359.14 359.46 318 347.66 802.31 598.9 675.61 679.06 683.52 687.22 319 503.55 708.80 598.9 651.60 653.16 655.17 656.84 320 283.02 385.80 299.4 357.16 357.94 358.95 359.78 321 1903.82 2266.88 1197.8 2165.70 2168.46 2172.02 2174.98 322 102.75 2.63 30.53 29.77 28.79 27.97 (Continued) CONCENTRATIONS (PPM) EXPONENTS OF THE GAM-IA RAY ENERGY USED IN WEIGHTING LINAC REACTOR Spike Added 0.5 1.0 2.0 4.0 Arkose (a sedimentary rock) 1007.90 1304.51 1197.51 1221.85 1224.10 1227.01 1229.42 416.09 618.82 598.9 562.32 563.86 565.85 567.50 325 481.84 1207.76 898.3 1005.46 1010.97 1018.10 1024.00 326 1073.08 1284.96 1197.8 1225.91 1227.52 1229.60 1231.32 327 104.67 375.87 299.4 300.29 302.35 305.01 307.22 328 549.48 833.62 898.3 754.43 756.59 759.38 761.69 329 593.57 883.71 898.3 802.85 805.06 807.90 810.26 330 265.17 728.91 598.9 599.67 603.19 607.75 611.51 331 751.93 1319.33 1197.8 1161.21 1165.52 1171.09 1175.70 332 306.30 332.46 299.4 325.17 325.37 325.63 325.84 333 121.59 5.13 37.59 36.70 35.56 34.61 Quartz Diurite (an igneous rock) 334 1040.59 1344.82 1197.8 1260.04 1262.35 1265.33 1267.80 335 75.58 297.83 299.4 235.89 237.58 239.76 241.57 336 1012.68 1359.11 1197.8 1262.57 1265.20 1268.60 1271.41 337 825.59 900.93 898.3 879.93 880.51 881.25 881.86 338 707.85 1167.35 898.3 1039.30 1042.79 1047.30 1051.03 339 355.14 568.28 598.9 508.88 510.50 512.59 514.32 340 968.56 1201.08 1197.8 1136.28 1138.05 1140.33 1142.22 341 282.57 756.33 598.9 624.30 627.90 632.55 636.40 53.42 367.03 299.4 279.63 282.01 285.09 287.64 166.14 341.32 299.4 292.50 293.83 295.55 296.97 0.0 4.79 3.46 3.49 3.54 3.58 Table 7 (Continued) SAMPLE CONCENTRATIONS (PPM) EXPONENTS OF THE GAMMA RAY ENERGY USED IN WEIGHTING NUMBERS LINAC REACTOR Spike Added 0^5______LO ______2 JD______4.0 Granite (an igneous rock) 345 631.96 691.44 598.9 674.87 675.32 675.90 676.39 346 1001.57 1478.17 1197.8 1345.35 1348.97 1353.65 1357.52 347 321.88 416.96 299.4 390.46 391.18 392.11 392.89 348 400.71 532.24 598.9 495.59 496.58 497.88 498.95 349 791.80 1503.53 1197.8 1305.19 1310.59 1317.58 1323.36 351 476.58 698.35 598.9 636.55 638.23 640.41 642.21 352 390.21 1111.85 898.3 910.75 916.22 923.31 929.17 353 429.82 858.93 898.3 739.35 742.60 746.81 750.30 354 579.90 1351.65 1197.8 1136.58 1142.44 1150.02 1156.29 355 0.0 22.82 16.46 16.64 16.86 17.05 SAMPLE 303 LINAC DATA ABSENT **** SAMPLE 350 LINAC DATA ABSENT **** SAMPLE CONCENTRATIONS (PPM) EXPONENTS OF THE GAMMA RAY ENERGY USED IN WEIGHTING NUMBERS LINAC REACTOR Spike Added 0.5______1.0 2j0______4.0 Pleistocene Alluvial Soil 301 1266.95 1147.28 1330.8 1180.74 1181.57 1183.80 1191.23 302 1161.72 1165.91 1197.8 1164.74 1164.71 1164.63 1164.37 304 1246.77 781.16 798.5 911.32 914.56 923.22 952.13 305 917.64 516.03 532.3 628.30 631.09 638.56 663.50 306 693.14 268.77 266.2 387.41 390.36 398.25 424.60 307 465.35 447.33 399.3 452.37 452.49 452.83 453.95 308 811.41 938.93 931.6 903.28 902.39 900.02 892.10 309 919.80 1021.23 1064.7 992.88 992.17 990.28 983.99 310 666.35 575.43 665.4 600.85 601.48 603.17 608.81 311 104.00 3.09 31.30 32.01 33.88 40.15 Gabbro (an igneous rock) 312 982.41 1014.67 1330.8 1005.66 1005.43 1004.83 1002.83 313 509.82 820.19 1064.7 733.43 731.27 725.50 706.22 314 398.56 466.87 532.3 447.77 447.30 446.03 441.79 315 472.52 304.68 399.3 351.60 352.77 355.89 366.31 316 205.79 199.00 133.1 200.90 200.95 201.07 201.50 317 1030.72 1125.45 1197.8 1098.97 1098.31 1096.55 1090.67 318 995.31 1190.13 798.5 1135.67 1134.31 1130.69 1118.59 319 388.21 298.92 266.2 323.88 324.50 326.16 331.71 320 1088.01 964.01 931.6 998.68 999.54 1001.85 1009.55 321 739.70 912.62 665.4 864.28 863.08 859.86 849.12 322 0.0 7.44 5.36 5.31 5.17 4.71 (Continued) CONCENTRATIONS (PPM) EXPONENTS OF THE GAMMA RAY ENERGY USED IN WEIGHTING LINAC REACTOR Spike Added 0.5 1.0 2.0 4.0 Arkose (a sedimentary rock) 506.42 300.48 399.3 358.05 359.49 363.31 376.10 324 982.09 520.72 665.4 649.69 652.90 661.48 690.13 325 852.87 1176.27 1197.8 1085.86 1083.61 1077.60 1057.52 326 592.10 757.68 931.6 711.39 710.24 707.16 696.88 327 1801.45 1256.73 1330.8 1409 1412.79 1422.92 1456.75 328 815.53 797.49 1064.7 802.53 802.66 802.99 804.11 329 274.18 181.29 133.1 207.26 207.90 209.63 215.40 330 271.60 552.22 532.3 473.77 471.82 466.60 449.17 331 261.88 275.17 266.2 271.45 271.36 271.11 270.29 332 1226.30 694.02 798.5 842.82 846.52 856.42 889.47 333 60.94 2.98 19.18 19.58 20.66 24.26 Quartz Diurite (an igneous rock) 334 381.75 205.12 266.2 254.50 255.73 259.01 269.98 335 1298.88 661.21 931.6 839.48 843.91 855.77 895.37 336 1331.05 1196.82 1330.8 1234.34 1235.28 1237.77 1246.11 337 441.58 171.94 133.1 247.32 249.20 254.21 270.95 338 454.44 440.00 399.3 444.04 444.14 444.41 445.30 339 1279.78 885.93 1197.8 996.03 998.77 1006.09 1030.55 340 634.51 651.05 798.5 646.43 646.31 646.01 644.98 341 936.95 722.60 665.4 782.52 784.01 788.00 801.31 342 1318.67 1033.24 1064.7 1113.03 1115.01 1120.32 1138.05 343 548.12 482.22 532.3 500.64 501.10 502.32 506.41 138.62 1.94 40.15 41.10 43.64 52.13 Table 8 (Continued) SAMPLE CONCENTRATIONS (PPM) EXPONENTS OF THE GAMMA RAY ENERGY USED IN WEIGHTING NUMBERS LINAC REACTOR Spike Added 0.5______UO ______2j0______4.0 Granite (an igneous rock) 345 1328.15 740.48 798.5 904.76 908.85 919.78 956.27 346 1271.18 1309.41 1330.8 1298.72 1298.45 1297.74 1295.37 347 524.23 298.85 266.2 361.86 363.43 367.62 381.61 348 309.52 675.28 931.6 573.03 570.48 563.69 540.97 349 1193.66 1164.09 1197.8 1172.36 1172.56 1173.11 1174.95 351 620.38 533.21 532.3 557.57 558.18 559.80 565.22 352 831.22 1047.59 1064.7 987.10 985.59 981.57 968.14 353 392.53 344.43 399.3 357.88 358.21 359.11 362.09 354 570.57 506.01 532.3 524.05 524.50 525.70 529.71 355 54.85 0.0 15.33 15.72 16.74 20.14 SAMPLE 303 LINAC DATA ABSENT SAMPLE 350 LINAC DATA ABSENT VO Table 9 DATA FOR URANIUM WEIGHTED CONCENTRATION RESULTS FROM LINAC AND REACTOR DATA SAMPLE CONCENTRATIONS (PPM) EXPONENTS OF THE GAMMA RAY ENERGY USED IN WEIGHTING NUMBERS LINAC REACTOR Spike Added 0.5______UO ______2J)______4.0 Pleistocene Alluvial Soil 301 10.09 20.11 17.7 14.67 14.72 14.84 15.07 302 42.41 34.86 35.5 38.96 38.92 38.83 38.66 304 91.77 78.59 70.9 85.75 85.68 85.53 85.22 305 119.07 83.28 88.6 102.73 102.53 102.12 101.29 306 188.56 84.40 106.4 141.01 140.42 139.24 136.83 307 189.43 122.06 124.1 158.67 158.29 157.53 155.97 308 118.40 139.35 141.8 127.96 128.08 128.32 128.80 309 127.68 171.86 159.5 147.85 148.10 148.60 149.62 310 157.87 134.10 177.3 147.02 146.89 146.61 146.07 311 5.53 0.0 3.01 2.98 2.91 2.79 Gabbro (an igneous rock) 312 15.07 13.56 17.7 14.38 14.37 14.36 14.32 313 35.11 18.10 35.5 27.34 27.25 27.05 26.66 314 35.10 57.76 53.2 45.44 45.57 45.83 46.35 315 63.18 48.62 70.9 56.53 56.45 56.29 55.95 316 91.03 104.16 88.6 97.02 97.09 97.24 97.55 317 152.81 106.05 106.4 131.46 131.20 130.67 129.59 318 106.73 116.41 124.1 111.15 111.20 111.32 111.54 319 145.22 127.31 141.8 137.05 136.95 136.74 136.33 320 150.30 178.85 159.5 163.33 163.50 163.82 164.48 321 163.00 216.63 177.3 187.48 187.78 188.39 189.63 322 0.0 7.33 3.35 3.39 3.47 3.64 (Continued') CONCENTRATIONS (PPM) EXPONENTS OF THE GAMMA RAY ENERGY USED IN WEIGHTING LINAC REACTOR Spike Added______0^5______1JD______2JD______4.0 Arkose (a sedimentary rock) 33.79 10.08 17.7 22.97 22.83 22.56 22.02 324 46.46 25.39 35.5 36.84 36.72 36.48 36.00 325 48.16 76.65 53.2 61.17 61.33 61.65 62.31 326 61.42 69.06 70.9 64.91 64.95 65.04 65.21 327 85.80 74.39 88.6 80.59 80.53 80.40 80.13 328 79.78 85.20 106.4 82.25 82.28 82.34 82.47 329 114.42 93.11 124.1 104.69 104.57 104.33 103.83 330 101.82 150.41 141.8 124.00 124.28 124.83 125.95 331 208.03 136.01 159.5 175.15 174.75 173.93 172.26 332 185.84 175.14 177.3 180.95 180.89 180.77 180.52 333 4.94 0.79 3.04 3.02 2.97 2.88 Quartz Diurite 334 20.55 9.25 17.7 15.39 15.33 15.20 14.94 335 49.13 41.32 35.5 45.56 45.52 45.43 45.25 336 60.60 55.65 53.2 58.34 58.31 58.25 58.14 337 85.38 74.54 70.9 80.43 80.37 80.25 80.00 338 92.69 103.03 88.6 97.41 97.47 97.59 97.83 339 108.04 84.40 106.4 97.25 97.11 96.85 96.30 340 107.77 99.73 124.1 104.10 104.05 103.96 103.78 341 149.54 128.69 141.8 140.02 139.90 139.66 139.18 125.48 146.97 159.5 135.29 135.41 135.66 136.15 227.08 140.24 177.3 187.43 186.94 185.96 183.95 2.43 5.11 3.65 3.67 3.70 3.76 Table 9 (Continued) SAMPLE CONCENTRATIONS (PPM) EXPONENTS OF THE GAMMA RAY ENERGY USED IN WEIGHTING NUMBERS LINAC REACTOR Spike Added______0^5______UO ______2^0______4.0 Arkose (a sedimentary rock) 323 33.79 10.08 17.7 22.97 22.83 22.56 22.02 324 46.46 25.39 35.5 36.84 36.72 36.48 36.00 325 48.16 76.65 53.2 61.17 61.33 61.65 62.31 326 61.42 69.06 70.9 64.91 64.95 65.04 65.21 327 85.80 74.39 88.6 80.59 80.53 80.40 80.13 328 79.78 85.20 106.4 82.25 82.28 82.34 82.47 329 114.42 93.11 124.1 104.69 104.57 104.33 103.83 330 101.82 150.41 141.8 124.00 124.28 124.83 125.95 331 208.03 136.01 159.5 175.15 174.75 173.93 172.26 332 185.84 175.14 177.3 180.95 180.89 180.77 180.52 333 4.94 0.79 3.04 3.02 2.97 2.88 Quartz Diurite 334 20.55 9.25 17.7 15.39 15.33 15.20 14.94 335 49.13 41.32 35.5 45.56 45.52 45.43 45.25 336 60.60 55.65 53.2 58.34 58.31 58.25 58.14 337 85.38 74.54 70.9 80.43 80.37 80.25 80.00 338 92.69 103.03 88.6 97.41 97.47 97.59 97.83 339 108.04 84.40 106.4 97.25 97.11 96.85 96.30 340 107.77 99.73 124.1 104.10 104.05 103.96 103.78 341 149.54 128.69 141.8 140.02 139.90 139.66 139.18 342 125.48 146.97 159.5 135.29 135.41 135.66 136.15 343 227.08 140.24 177.3 187.43 186.94 185.96 183.95 344 2.43 5.11 3.65 3.67 3.70 3.76 Table 9 (Continued) SAMPLE CONCENTRATIONS (PPM) EXPONENTS OF THE GAMMA RAY ENERGY USED IN WEIGHTING NUMBERS LINAC REACTOR Spike Added 0.5______UO ______2^0______4,0 Granite (an igneous rock) 345 34.51 40.66 17.7 37.31 37.35 37.42 37.56 346 27.04 36.74 35.5 31.47 31.52 31.63 31.86 347 38.43 85.27 53.2 59.81 60.07 60.61 61.69 348 66.72 61.27 70.9 64.23 64.20 61.14 64.02 349 98.20 96.83 88.6 97.58 97.57 97.55 97.52 351 93,85 110.69 124.1 101.54 101.63 101.82 102.21 352 111.34 142.82 141.8 125.54 125.89 126.25 126.98 353 52.83 113.48 159.5 80.52 80.86 81.55 82.95 354 152.63 150.09 177.3 151.47 151.46 151.43 151.37 355 3.57 2.81 3.22 3.22 3.21 3.19 SAMPLE 303 LINAC DATA ABSENT •k'k'k'k SAMPLE 350 LINAC DATA ABSENT **** Chapter V Discussion and Conclusions A rapid, economical, fully instrumental method has been developed for the determination of gold, mercury, silver, tellurium and uranium. The procedure utilizes neutron and photon activation of samples followed by analysis of the gamma ray spectra. Computer techniques are involved in the reduction of data. This method has been demonstrated effective on a variety of rocks and alluvial soil. Precision of approximately 20% has been obtained for concen trations varying (peculiar to the element determined) from 4 to 300 parts per million by weight (6 to 450 micrograms). Table 10 provides the information pertinent to each element along with the estimated maximum sensitivities. These sensitivities were calculated for the conditions used and, in all likelihood, could be enhanced by longer irradiation times (at greater cost per sample). Obvious sensitivity advantages for neutron (reactor) irradiated samples are frequently offset by the complexity of the resulting gamma ray spectrum (on the order of 2000 gamma rays from nuclides having half-lives greater 78 than one day). The estimated time of analysis was two hours (mostly counting time of the detector) per sample. The method is presented as outlined, fulfilling all re quisites set. It involves single irradiations with the reactor and LINAC and single gamma ray spectra from the products of each. Thus, it cannot be compared fairly to the herculean method of 73 Table 10 Calculated Accuracies and Sensitivities Estimated Concentration Relative Absolute Relative Absolute Relative Absolute Element Maximum Sensitivity Range % Error 7. Error 7. Error 7. Error 7o Error 7o Error Determined (PPM)* (PPM) Linac Linac Reactor Reactor Composite Composite lilNAC Reactor Gold 4.4 - 44.3 5.9 22.0 4.6 12.5 4.7 11.5 3.4 0.03 Mercury 88.7 - 887.5 35.4 61.5 7.4 14.1 14.6 23.1 74.6 3.1 Silver 299.4 -1197.8 24.9 32.7 16.1 17.7 6.3 12.3 198.1 8.5 Tellurium 133.1 -1330.8 19.4 36.3 5.8 16.9 4.2 18.1 120.0 7.0 Uranium 17.7 - 177.3 3.9 23.2 2.8 18.0 3.8 15.9 16.6 3.9 Maximum sensitivity was calculated for standard samples (in silica matrix, which was essentially inter ference-free but yielded some Compton background) at the same decay time as the samples analyzed. The following equations of Currie'^ were used: LQ = 20% = CT + CB where L0 h the minimum quantity of the element which may be determined with a precision of 207. or ^ better. /ji = the estimated standard deviation. C^, = the total counts in the gamma ray peak. C., = the total counts attributed to background in the region studied. D S was then estimated: I*_ max g _ ^ max Cg . Q where S s the estimated maximum sensitivity;i C_ = the net signal counts (C =C_-C ); Q = the quantity max o b i ii of the element in the sample. 75 j 3 Morrison ejt al. which involved no less than four different irradiations and, at least, a dozen gamma ray spectra (of unspeci fied count time) for each sample, all of which were obtained with 34 a Compton-suppression spectrometer of considerable sophistication. Nor can the method be expected to compete with the procedure of 53 Schmitt ejt al. which used fast neutrons as well as photons and thermal neutrons among seven different irradiations of each sample. Exchanging the frame of reference, it can be frankly stated that neither of these methods can compare to the method described herein for economy of time, funds and effort. Even so, more information of a specialized nature is available at the simple cost of obtaining and analyzing additional gamma ray spectra. In this study, addi tional spectra were obtained from the photon irradiated samples after a decay period of three weeks. Where pertinent, the data are presented in Appendix II and discussed below along with the general method for the element. The determination of gold presented no significant problems in either neutron or photon irradiated samples, potential interferences failed to materialize and sensitivity and accuracy were both outstanding. Silver was determined with good accuracy but sensitivity was limited by the lack of a highly abundant peak in the gamma ray spectrum of photon irradiated samples. The gamma ray chosen is produced by *^Ag which is a (-y^n) product of *^Ag. 76 The cross section for (7 ,2 0 ) reactions is relatively low at 30 MeV, the (y»^) reaction prevailing.The latter reaction does produce an isotope, * ^ mAg, of suitable half-life (8.4 days), but the most prominent peak in its gamma ray spectrum arises at 511 keV which co incides with the peak from position annihilation, which is very common among photon irradiated substances. Two gamma rays of sensitivity approximately equal to the one of choice do arise from ^ ^ mAg. A futile effort was made to utilize the one at 717.1 keV, but an inter ference free gamma ray at 1045.7 keV had to be abandoned due to limitations of the multichannel analyzer; to include it in a single spectrum would have meant using a channel width of more than 2.6 keV thereby wasting resolution vitally needed at lower energies. The 344.4 keV gamma ray of ^"*Ag was measured again after a decay period of three weeks and results were seen to be slightly improved. However, ^^Hf(T^ = 70 days) hangs as a Sword of Damocles over any long delayed analysis using this peak. In spite of the direct and rather significant inter- 235 ference from fission products of U, the reactor irradiated samples gave a very good determination of tellurium. No consistent error could be attributed to the varying amounts of uranium in the samples. Results from the photon irradiated samples were less satisfactory and these samples were recounted after three weeks with some improve ment in accuracy. One possible cause of the erratic data is 77 ^Ge(T^ = 38 hours). This isotope produces a gamma ray of 573.4 keV 121 which cannot be resolved from the Te peak, but the abundance is 103 a matter of question. Lederer et al. list it as moderately strong and it is shown thus by Cline and Heath*"*’*’, but the spectra 112 113 114 shown by Baker et al. , Abe and Oka ejt al. show only a small contribution, if any. Regardless of this discrepancy, all 69 contributions from Ge would be eliminated after a three week delay in counting. However, a 100 minute count of the diminished activity was subjected to a persistent interference from the 583.1 keV (the 121 103 gamma ray of Te appears at 575.4 keV, Lederer et: al. notwith- 208 standing) gamma ray of T1 which was present as member of the 4n series of natural radioactivity and penetrated the lead shield to the extent of about one count per minute at 583.1 keV. Application of more sophisticated methods than that of simple manual measure ment of the peak area would, undoubtedly improve this situation. Mercury proved to be by far the most difficult of the five elements to determine. While having considerable sensitivity when determined using thermal neutrons the only isotope with a useful half-life has only one abundant gamma ray which is of rela tively low energy and is subject to several persistent interferences which can only be removed by subtraction of a portion of the peak. The probability of error increases with each subtraction. The linear accelerator offered the possibility of an interference free 78 determination of mercury. The isotope *'^mHg(T^ = 24 hours) is 198 produced by the (*Y,n ) reaction from Hg(10.02% isotopic abundance) and emits an interference free ganana ray of 134.0 keV. Duly an attempt was made to utilize this isotope, but it met with failure. The 1024 channel analyzer was unavailable during the counting period of the LINAC irradiated samples and the limitations of the 400 channel analyzer are most debilitating at lew energies where great dispersion is needed to take advantage of the very high resolution 41 of the Ge(Li) detector in this region. The relatively short half- life of the isotope does not impose insurmountable obstacles. The 203 isotope Hg is also produced by photon irradiation and was used to determine mercury in this case. It is again subject to persistent interferences and again portions of the peak must be subtracted. 115 In addition, relatively common lead produces an overwhelming 203 (see results for samples 301-311) interference with its Pb(Ti = 52 hours) isotope. The presence of this isotope necessitates a three week (<-10 half-lives) delay in counting and the results, as given in Appendix II, show the vast improvement when this pro cedure was used. Uranium was determined with remarkable sensitivity and accuracy. Both neutron and photon irradiated products were felt to be highly vulnerable to interferences because both produce rela tively short half-lived species with low energy gamma rays. Compton 79 background from all gamma rays of higher energy diminishes the sensitivity obtainable though this was not reflected in the stan dard spectra used to estimate sensitivity. Thus, alternative methods of uranium determination were investigated. When irradiated with high energy photons, uranium and thorium undergo photofission (see Figures 23 and 24) yielding a wide variety of fission pro ducts. The relative mass yields depend upon the species fissioned 116-119 and the inducing energy. Photofission cross sections have 120-126 also been obtained but no data have been presented for 30 MeV bremsstrahlung. Binary fission does predominate, however, giving the characteristic two humped mass yield curves with maxima at mass numbers about 95 and 135 for both substances. The fission yields 235 are generally similar to those for thermal neutron fission of U 30 which are well documented. Perusal of the photofission spectra 140 showed the 1597.0 keV gamma ray peak resulting from La to be far and away the most promising for analytical purposes. This isotope 140 is the daughter of Ba(T. = 12.8 days) formed by the reaction 30 sequence: 2 ^®U(v,f) "^XeCTj. = 16 seconds) Cs(Ti = 66 seconds) La(Ti = 40.2 hours) The equations for such a transient equilibrium indicate that the 140 activity of La does not reach its maximum point until 4.7 days after irradiation. Thus, the large peak in the photofission spectra shown (see Figures 23 and 24) is still growing only two days after the irradiation while background radiation continually diminishes. 140 140 The growth-decay curve for the Ba- La couple is shown in Fig ure 22. Occurring at such a high energy, the 1597.0 keV gamma ray peak is ideal for instrumental activation analysis. Very few iso topes of significant half-life exist which have gamma rays near or above it in energy and it is thus surrounded by an extremely low 208 background. A slight, persistent interference comes from T1 which is part of the counting room background. This peak is caused by the double escape of positron annihilation signals and occurs rather broadly around 1595 keV. In addition, a small amount of j^O 139 La was produced by the reaction La(n,Y) La. The neutrons result from bremsstrahlung interactions with the walls of the 53 irradiation facility. This interference, which is not serious since three half-lives have already passed before the fission pro- 140 . . duced La activity reaches its maximum, can be completely elimi nated by simply shielding the samples with cadmium. Cadmium-113 has 103 a neutron capture cross section of 20,000 barns and thus is vir tually impermeable to neutrons. Despite this copious promise, a dearth of funds precluded further investigation. Given these funds, Activity 0 140. La(T, = 40.2 hours) 40.2 = La(T, 50 rwhDcyCre o 4B-^a couple 140Ba-l^La for Curve Decay Growth 100 4 1 ea ie (Hours) Time Decay °Ba(Tj = 307.2 hours) 307.2 = °Ba(Tj 150 iue 22 Figure "2 200 250 300 (.flU Nl'./U lR N N H i 00 20C 9 • 300 -100 500 600 /00 HTFSIN PCRM F RNU Tf DT RTR IRflfiDlRTION RFTER TrfQ DRTS URRNIUM OF SPECTRUM PHOTOFISSION 0 90 00 10 20 1300 1200 1100 1000 900 800 iue 23 Figure moo :io‘ ro 00 I °Sni A«1C/CS A«1C/CS *1 .v 200 300 4 00 500 600 700 800 900 100 iJUO PHOTOFISSION SPEC1RJM OF IHORIUM T»JO OfiTS RFT£R I RRflO 1RT I ON Figure 24 00 u> 84 a simple method for the determination of uranium plus thorium (used interchangeably as breeder reactor fuels) should be readily available. 235 In a slow neutron flux, only U of naturally occurring isotopes is appreciably fissioned. A radiochemical method developed by Smales^ used the ^^Ba-^^La couple to determine uranium down to the 10 nanogram level. Sacrificing needless sensitivity in the interest of simplicity, an attempt was made to adapt this couple to a fully instrumental determination. After neutron irradiation, two separate measurements were made of the 1507.0 keV gamma rays 140 of La, the second one coming at least two weeks after the first. Simultaneous equations were then used in an effort to eliminate 139 140 the contribution from La(n,y) = 40.2 hours), but errors attributed to inconsistencies in the spectrometer performance made the method of dubious value though it does deserve further study. In summary, the method developed in this work allows many possibilities for improvements in sensitivity and accuracy with only a modest additional investment of time. Greater monetary investment would inevitably lead to even more bountiful improvement in results. However, as it stands now, a method has been developed which determines gold, mercury, silver, tellurium and uranium in geological matrices by fully instrumental means and with minimum investment of time and technical skill. In other words, it does what it was supposed to do. Appendix I Computer Program CONC DATA* 0001 DIMENSION ENERGY(10,2),THALF(10,2),CONCOR(10,2),SENWT(10,2),GEN(50,10,2), NEN(500,2),DECTIM(500,2),A(500,2),A0(500,2),RAWCON(500,2),C0N2C(500,4), TITLE(20),1(2) ,P(4) 0002 DOUBLE PRECISION SOURCE(2) 0003 DATA SOURCE/8H LINAC ,8HEEACTOR /,II/ 0 /,P/.5,1.,2.,14./,ST0P/4HST0P/ 0004 ALN2 = ALOG(2.) 0005 DO 1 L =1,10 0006 DO 1 J=l,2 0007 1 ENERGY(L,J) =0.0 0008 READ 3,TITLE 0009 3 FORMAT(20A4) 0010 1 (1) =0 0011 1 (2 ) =0 0012 4 CONTINUE 0013 READ 5,K,EN,T1,CC,SF 0014 5 FORMAT(I5,4F10.0) 0015 IF(K - 1) 8,7,6 0016 6 1 (2) = 1 (2) + 1 0017 ENERGY(I(2),2) = EN 0018 THALF(I(2),2) = T1 0019 CONCOR(I(2),2) = CC 0020 SENWT(I(2),2) = SF 0021 GO TO 4 0022 7 1 (1) = 1 (1) + 1 0023 ENERGY(I(1),1) = EN 0024 THALF(I(1),1) = T1 0025 CONCOR(I(l),1) = CC Computer Program CONC DATA* (continued) 0026 SENWT(I(1) ,1) = SF 0027 GO TO 4 0028 8 PRINT 100,TITLE 0029 100 FORMAT(1H1,30X,20A4,// ) 0030 DO 89 J = 1,2 0031 PRINT 17,SOURCE(J) 0032 17 FORKAT(60X,A8,'DATA1// 58X,'CALIBRATION DATA'// 200X,'GAMMA ENERGY1,1,12X, 'HALF LIFF',13X,'CONC. CORRECTION',9X,’SENS. CORRECTION’/) 0033 K = I(J) 0034 PRINT 18,(ENERGY(L, J) ,THALF(L, J),CONCOR(L, J) ,SENWT(L, J) ,L=1,K) 0035 18 FORMAT(15X,F15.4,10X,F15.4,10X,G15.4,10X,G15.4) 0036 89 CONTINUE 0037 K = 1(2) - 1(1) 0038 IF(K.EQ.O) GO TO 10 0039 II = 1 0040 IF(K.LT.O) II = 2 0041 PRINT 9,SOURCE(II) 0042 9 FORMAT(5X,A8,' CALIBRATION DATA ABSENT ***** / 1X,28(1H*) /) 0043 10 CONTINUE 0044 READ 3,TITLE 0045 MM = 1 0046 NM = 500 0047 IF(TITLE(1).EQ.STOP) GO TO 25 0048 DO 2 L =1,500 0049 DO 2 J =1,2 0050 2 GEN(L,J) = 0.0 0051 90 READ 91,M,N,G,DT,AI 0052 91 FORMAT (13,12,3F10.0) 0053 IF(N.NE.1.AND.N.NE.2) GO TO 11 „ 0054 GEN(M,N) = G Computer Program CONC DATA* (continued) 0055 DECTIM(M,N) = DT 0056 A(M,N) =» Al 0057 IF(M.GT.MM) MM = M 0058 IF(M.LT.NM) NM = M 0059 GO TO 90 0060 11 CONTINUE 0061 DO 13 L = NM,MM 0062 DO 13 M = 1,2 0063 NEN(L,M) = 0 0064 IF(GEN(L,M) .EQ.O.) GO TO 13 0065 J = I(M) 0066 DO 12 N = 1,J 0067 12 IF (GEN(L,M) .EQ. ENERGY(N,M)) NEN(L,M) = N 0068 N = NEN(L,M) 0069 AO(L,M) = A(L,M) * EXP(ALN2 * DECTIM(L,M) / THALF(N,M) ) 0070 IF ( GEN(L,M) .EQ. 228. ) AOCOR = AO ( L , M ) * .03058 0072 RAWCON(L,M) = AO(L,M) / CONCOR(N,M) 0073 13 CONTINUE 0074 DO 16 L = NM,MM 0075 IF(NEN(L,1).EQ.0.AND.NEN(L,2).EQ.0) GO TO 16 0076 IF(NEN(L,1).EQ.O) PRINT 14,L,S0URCE(1) 0077 IF(NEN(L,2).EQ.O) PRINT 14,L,SOURCE(2) 0078 14 FOHMAT(5X,'SAMPLE ',14,2X,A8,'DATA ABSENT ****'/ 1X,28(1H*)/) 0079 IF(NEN(L,1).EQ.0.0R.NEN(L,2).EQ.0) GO TO 16 0080 DO 15 J = 1,4 0081 15 C0NC(L,J) = (RAWCON(L,l) + RAWCON(L,2)) / 4. 1 + ( SENWT(NEN(L,1),1)*GEN(L,1)**P(J)*RAWCON(L,1) + 2 SENWT(NEN(L,2),2)*GEN(L,2)**P(J)*RAWCON(L,2) )/ (2.*( 3 SENWT(NEN(L,1),1)*GEN(L,1)**P(J) + SEIWT(NEN(L,2),2)*GEN(L,2)**P 4(J)) ) Computer Program CONC DATA* (continued) 0082 16 CONTINUE 0083 DO 21 J =1,2 0084 PRINT 100,TITLE 0085 PRINT 19,SOURGE(J) 0086 19 FORMAT(60X,A8,'DATA'// 55X,'CONCENTRATION RESULTS'// ' SAMPLE NUMB1ER1,4X 'GAMMA ENERGY',10X,'DECAY TIMES(HRS.)',11X,'RAW COUNTS',1OX,2 'COUNTS (TIME = 0)',7X,'RAW CONCENTRATION1/) 0087 DO 21 K =NM,MM 0088 IF(GEN(K,J).EQ.O.) GO TO 21 0089 PRINT 20,K,GEN(K,J),DECTIM(K,J),A(K,J),AO(K,J),RAWCON(K,J) 0090 20 FORMAT(5X,I4,11X,F8.2,15X,F6.0,18X,F10.0,11X,F10.0,14X,F7.2 ) 0091 21 CONTINUE 0092 PRINT 100,TITLE 0093 PRINT 22,P 0094 22 FORMAT(37X, 'WEIGHTED CONCENTRATION RESULTS FROM LINAC AND REACTOR 1DATA7/1X, 'SAMPLE', 14X, 'CONCENTRATIONS'/IX, 'NUMBERS',7X, 'LINAC1,14 2X,'REACTOR',3X,4F20.0/) 0095 DO 24 L = NM,MM 0096 IF((GEN(L,1).EQ.0.).0R.(GEN(L,2).EQ.0.)) GO TO 24 0097 PRINT 23,L,RQWCON(L,l),RAWCON(L,2),(CONC(L,K),K=1,4) 0098 23 FORMAT(1X,I5,2(F14.2,6X),4F20.2) 0099 24 CONTINUE 0100 GO TO 10 0101 25 STOP END *This program was kindly written for the author of this dissertation by Dr. David Copeland and was amended by Dr. Tracy Broussard, Mr. Henry Streiffer and Miss Linda McCarter. 89 To facilitate the use of computer program CONCDATA, the input procedure is explained. In addition to the control cards, the data cards must be included in the program in the following sequence: Title Card: This card specifies that the following data are for calibration. Calibration Cards: Column (for each element for both activa 5 a 1 or a 2 indicates whether data tion sources) are from LINAC or Reactor. 6-15 the gamma ray energy in keV. 16-25 the half-life in hours. 26-35 the concentration correction factor in counts per part per million. 36-45 the sensitivity weighting factor in counts per part per million. Blank Card Title Card: this card gives the name of the element for (for each which individual sample data follow. element) Data Cards: Column 1-3 the sample number. 5 a 1 are 6-15 the 16-25 the 26-35 the peak in counts. 90 Blank Card (for each element) STOP Card Column 1-4 STOP Terms are defined as follows: ENERGY = the gamma ray energy of the isotope in keV. THALF = the half-life of the isotope in hours. CONCOR = the concentration correction factor in peak area counts per part per million of the element at time zero. SENWT = the sensitivity weighting factor in peak area counts per part per million at the optimum time of counting. GEN = the gamma ray energy of the isotope in keV. NEN = the number of the sample for which data are given. DECTIM = the time that the activated sample decayed before counting in hours. A - the area of the gamma ray photopeak at the time of counting in counts. AO = the area of the gamma ray photopeak corrected to time zero in counts. RAWCON = the raw concentration of the element determined from a single activation in parts per million. CONC = the concentration of the element determined by the weighted equation in parts per million. P = the power to which the gamma ray energy is raised in the weighting equation. Appendix II For the most part, data pertinent to extensions or modifications of the analytical method are included herein and discussed elsewhere. Much of the material applies to determinations made using samples counted three weeks after L1NAC irradiation. The calculated maximum sensitivities for this decay time are: Au 9.5 PPM Hg 84.2 PPM Ag 198.0 PPM Te 239.7 PPM U 42.8 PPM Other aspects of the data are left to a qualitative judgment based upon scrutiny of the graphs and spectra. For the photofission studies, 100 mgs of pure uranyl acetate and thorium oxide, respectively, were placed in 2/5 dram polyethylene vials which were then heat sealed and wrapped in aluminum foil to reduce heat deformation. They were irradiated for one hour in the LINAC beam at 25 MeV maximum electron energy. 3 Spectra were taken with an 8 cm Ge(Li) detector which had a 137 resolution of 2.5 keV FWHM for the 662 Kev gamma ray of Cs. A 4096 channel analyzer (Nuclear Data #2200) was used with the same 91 read out system previously described . All equipment along with much helpful expertise was kindly provided by Dr. E.F. Zganjar of the Physics Department of the Louisiana State University. Further technical assistance was generously provided by Mr. Michael Svoren, a member of Dr. Zganjar's research group. 10 Counts 2 __ 4- Gamma Ray Spectrum of Mercury 2 Days after Irradiation with Photons with Irradiation after 2Days Mercury of Spectrum Ray Gamma 3 . 5 6 3 z z ~ 8 - Z 7 - S 9 3 7 ~ i '— 8— v— 100 - - - - ~ - - - - 203„ keV 279.1 am RyEeg (keV) Energy Ray Gamma 300 iue 25 Figure Energy 300 93 600 Counts 10 _ 0 3- 2 £>- 3 5 - s 6 8 t — 3 I — - r 5 - a - 7 — — - — - — - - airto uv -Mruy17) LINAC -Mercury(197m) Curve Calibration ocnrto (PPM) Concentration iue 26 Figure Counts 1 1 2 3 2 - - - Calibration Curve - Mercury fclRAiC -Mercury Curve Calibration Jj(Later Count) ocnrto (PPM) Concentration iue 27 Figure Counts 0 0 j I 5x10 - Calibration Curve - Silver LINAC (Later Count) (Later LINAC Silver - Curve Calibration ocnrto (PPM) Concentration iue 28 Figure 96 Counts 0 1 j _ - Calibration Curve - Tellurium LINAC (Later Count) (Later LINAC Tellurium - Curve Calibration Concentration (PPM) Concentration iue 29 Figure Table 11 DATA FOR MERCURY (LINAC SAMPLES Allowed Three Weeks Decay) WEIGHTED CONCENTRATION RESULTS FROM LINAC AND REACTOR DATA SAMPLE CONCENTRATIONS (PPM) EXPONENTS OF THE GAMMA RAY ENERGY USED IN WEIGHTING NUMBERS LINAC REACTOR Spike Added 0.5______LO ______2^0______4.0 Pleistocene Alluvial Soil 301 122.05 138.09 177.5 133.45 133.45 133.45 133.45 302 152.37 511.17 443.7 407.34 407.34 407.34 407.34 304 1 7 0 . 2 8 118.27 88.7 133.32 133.32 133.32 133.32 305 358.00 409.15 355.0 394.35 394.35 394.35 394.35 306 934.81 701.87 710.0 769.28 769.28 769.28 769.28 307 307.57 335.90 266.2 327.70 327.70 327.70 327.70 308 541.31 919.71 798.7 810.21 810.21 810.21 810.21 309 918.47 1000.59 887.5 976.82 976.82 976.82 976.82 310 475.65 610.45 621.2 571.44 571.44 571.44 571.44 311 0 . 0 0 . 2 2 0.16 0.16 0.16 0.16 Gabbro (an igneous rock) 312 88.75 180.37 177.5 153.86 153.86 153.86 153.86 313 832.08 668.67 710.0 715.96 715.96 715.96 715.96 314 508.01 562.78 621.2 546.93 546.93 546.93 546.93 315 479.74 406.01 443.7 427.34 427.34 427.34 427.34 316 758.56 1018.76 887.5 943.46 943.46 943.46 943.46 317 381.56 411.03 532.5 402.50 402.50 402.50 402.50 318 628.97 1043.94 798.7 923.85 923.85 923.85 923.85 320 773.01 126.26 88.7 313.42 313.42 313.42 313.42 321 564.88 482.10 355.0 506.06 506.06 506.06 506.06 322 0.63 4.59 3.45 3.45 3.45 3.45 vO CD Table 11 (Continued) SAMPLE CONCENTRATIONS (PPM) EXPONENTS OF THE GAMMA RAY ENERGY USED IN WEIGHTING NUMBERS LINAC REACTOR Spike Added 0.5______UO ______2^0______4.0 Arkose (a sedimentary rock) 323 767.67 603.80 710.0 651.22 651.22 651.22 651.22 324 494.50 571.01 621.2 548.87 548.87 548.87 548.87 325 293.75 520.58 443.7 454.94 454.94 454.94 454.94 326 188.03 168.82 177.5 174.38 174.38 174.38 174.38 327 176.56 284.22 266.2 253.06 253.06 253.06 253.06 328 878.26 83.71 88.7 313.64 313.64 313.64 313.64 329 691.17 819.61 887.5 782.44 782.44 782.44 782.44 330 227.62 436.35 355.0 375.95 375.95 375.95 375.95 331 248.66 495.63 532.5 424.16 424.16 424.16 424.16 332 1102.42 803.94 798.7 890.31 890.31 890.31 890.31 333 0 . 0 0 . 0 0 . 0 0 . 0 0 . 0 0 . 0 Quartz Diurite (an igneous rock) 334 1077.44 864.64 798.7 926.22 926.22 926.22 926.22 336 141.06 182.66 177.5 1 7 0 . 6 2 170.62 170.62 170.62 337 356.90 339.49 355.0 344.53 344.53 344.53 344.53 338 310.08 321.64 266.0 318.30 318.30 318.30 318.30 339 277.25 418.85 443.7 377.87 377.87 377.87 377.87 340 123.15 96.44 88.7 104.17 104.17 104.17 104.17 341 647.03 737.02 621.2 710.98 710.98 710.98 710.98 342 861.77 863.74 710.0 863.17 863.17 863.17 863.17 343 517.44 766.35 798.7 694.32 . 694.32 694.32 694.32 344 0 . 0 0.28 0 . 2 0 0 . 2 0 0 . 2 0 0 . 2 0 VO VO Table 11 (Continued) SAMPLE CONCENTRATIONS (PPM) EXPONENTS OF THE GAMMA RAY ENERGY USED IN WEIGHTING NUMBERS LINAC REACTOR Pike Added______0^5______LO ______2^0______4.0 Granite (an igneous rock) 345 1184.89 899.25 887.5 981.91 981.91 981.91 981.91 346 63.46 222.23 177.5 176.29 176.29 176.29 176.29 347 649.86 995.18 798.7 895.25 895.25 855.25 895.25 348 229.03 314.90 355.0 290.05 290.05 290.05 290.05 349 108.70 107.29 88.7 107.70 107.70 107.70 107.70 351 226.83 721.64 621.2 578.45 578.45 578.45 578.45 352 102.46 530.01 443.7 406.32 406.32 406.32 406.32 353 257.46 479.47 532.5 415.23 415.23 415.23 415.23 354 139.02 332.58 266.2 276.56 276.56 276.56 276.56 355 0 . 0 0 . 0 0 . 0 0 . 0 0 . 0 0 . 0 SAMPLE 303 LINAC DATA ABSENT **** SAMPLE 319 LINAC DATA ABSENT **** SAMPLE 33-5 LINAC DATA ABSENT **** SAMPLE 350 LINAC DATA ABSENT **** Table 12 DATA FOR SILVER WEIGHTED CONCENTRATION RESULTS FROM LINAC AND REACTOR DATA SAMPLE CONCENTRATIONS (PPM) EXPONENTS OF THE GAMMA RAY ENERGY USED IN WEIGHTING NUMBERS LINAC REACTOR Spike Added______0^5______1^0______2^0______4.0 Pleistocene Alluvial Soil 301 1868.64 1146.13 1197.8 1357.01 1349.17 1338.85 1330.16 302 866.81 719.22 598.9 762.30 760.70 758.59 756.81 304 1601.79 1148.88 898.3 1281.07 1276.15 1269.69 1264.24 305 1717.52 1395.07 1197.8 1489.18 1485.68 1481.08 1477.20 306 1328.58 858.51 898.3 995.71 990.61 983.90 978.24 307 191.34 370.91 299.4 318.50 320.45 323.01 325.17 308 922.72 737.33 598.9 791.44 789.43 786.78 784.55 309 485.00 1456.70 1197.8 1173.09 1183.64 1197.51 1209.20 310 929.26 845.05 898.3 869.63 868.71 867.51 866.50 311 0 . 0 1.94 1.37 1.39 1.42 1.45 Gabbro (an igneous rock) 312 905.08 1171.86 1197.8 1094.00 1096.89 1100.70 1103.91 313 523.50 588.75 598.9 569.71 570.42 571.35 572.13 314 721.78 980.41 898.3 904.93 907.73 911.43 914.54 315 475.95 555.00 598.9 531.93 532.79 533.91 534.87 316 892.58 1076.84 898.3 1023.06 1025.06 1027.69 1029.91 317 240.41 369.63 299.4 331.91 333.31 335.16 336.71 318 553.91 802.63 598.9 729.81 732.51 736.05 739.04 320 270.40 385.80 299.4 352.12 353.37 355.02 356.41 321 1121.09 2266.88 1197.8 1932.46 1944.89 1961.25 1975.04 322 31.63 2.63 11.09 10.78 10.36 1 0 . 0 1 101 Table 12 (Continued) SAMPLE CONCENTRATIONS (PPM) EXPONENTS OF THE GAMMA RAY ENERGY USED IN WEIGHTING NUMBERS LINAC REACTOR Spike Added______0^5______1J0______2^0______4.0 Arkose (a sedimentary rock) 323 1184.07 1304.51 1197.8 1269.36 1270.66 1272.38 1273.83 324 474.18 618.82 598.9 576.60 578.17 580.24 581.98 325 711.55 1207.76 898.3 1062.93 1068.31 1075.40 1081.37 326 1122.83 1284.96 1197.8 1237.64 1239.40 1241.71 1243.66 327 279.05 375.87 299.4 347.61 348.66 350.04 351.21 328 366.71 838.62 898.3 697.34 702.41 709.07 714.69 329 744.04 883.71 898.3 842.94 844.46 846.45 848.14 330 357.39 728.91 598.9 620.47 624.50 629.81 634.28 331 1092.40 1319.33 1197.8 1253.10 1255.56 1258.80 1261.53 332 209.71 332.46 299.4 296.63 297.97 299.72 301.20 333 45.20 4.13 16.83 16.39 15.82 15.34 Quartz Diurite (an igneous rock) 334 1353.36 1344.82 1197.8 1347.31 1347.22 1347.09 1346.99 336 1502.76 1359.11 1197.8 1401.04 1399.48 1397.43 1395.70 337 960.92 900.93 898.3 918.44 917.79 916.93 916.21 338 712.62 1167.35 898.3 1034.63 1039.57 1046.06 1051.53 339 691.81 568.28 598.9 604.33 602.99 601.23 599.74 340 880.15 1201.08 1197.8 1107.41 1110.89 1115.48 1119.34 341 552.24 756.33 598.9 696.76 698.98 701.89 704.35 342 359.15 367.03 299.4 364.73 364.81 364.93 365.02 343 582.63 341.32 299.4 411.75 409.13 405.69 402.78 102 344 0 . 0 4.79 3.39 3.45 3.52 3.57 Table 12 (Continued) SAMPLE CONCENTRATIONS (PPM) EXPONENTS OF THE GAMMA RAY ENERGY USED IN WEIGHTING NUMBERS LINAC REACTOR Spike Added 0.5 ______L lO______2^0______4.0 Granite (an igneous rock) 345 565.72 691.44 598.9 654.75 656.11 657 91 659.42 346 1173.62 1478.17 1197.8 1389.28 1392.58 1396 93 1400.60 347 229.12 416.96 299.4 362.13 364.17 366 85 369.11 348 401.94 532.24 598.9 494.21 495.63 497 49 499.05 349 1158.11 1503.53 1197.8 1402.72 1406.46 1411 40 1415.55 351 300.37 698.35 598.9 582.19 586.51 592 19 596.98 352 861.16 1111.85 898.3 1038.68 1041.40 1044 98 1048.00 353 630.32 858.93 898.3 792.20 794.68 797 95 800.70 354 1102.43 1351.65 1197.8 1278.91 1281.62 1285 18 1288.18 355 0 . 0 22.82 16.16 16.41 16 74 17.01 SAMPLE 303 LINAC DATA ABSENT SAMPLE 319 LINAC DATA ABSENT SAMPLE 335 LINAC DATA ABSENT SAMPLE 350 LINAC DATA ABSENT IcMcMc'k'Mek'k'frkfrk'klticiirklrfcMriflek'}: Table 13 DATA FOR TELLURIUM (LINAC SAMPLES Allowed Three Weeks Decay) WEIGHTED CONCENTRATION RESULTS FROM LINAC AND REACTOR DATA CONCENTRATIONS (PPM) EXPONENTS OF THE GAMtfA RAY ENERGY USED IN WEIGHTING LINAC REACTOR Spike Added 0.5______UO ______2^0______4.0 Pleistocene Alluvial Soil 301 908.69 1147.28 1330.8 1076.99 1074.59 1068.33 1049.09 302 1083.89 1165.8 1197.8 1141.74 1140.92 1138.76 1132.15 304 665.51 781.16 798.5 747.09 745.92 742.89 733.56 305 738.89 516.03 532.3 581.69 583.94 589.78 607.75 307 431.20 447.33 399.3 442.58 442.42 441.99 440.69 308 570.67 938.93 931.6 830.44 826.72 817.06 787.36 309 649.66 1021.23 1064.7 911.76 908.01 898.27 868.30 310 632.18 575.43 665.4 592.15 592.72 594.21 598.78 311 0 . 0 3.09 2.18 2.15 2.07 1.82 Gabbro (an igneous rock) 312 773.48 1014.67 1330.8 943.62 941.18 934.86 915.41 313 777.36 820.19 1064.7 807.57 807.14 806.02 802.56 314 351.27 466.87 532.7 432.81 431.64 428.61 419.29 315 237.96 304.68 399.3 285.02 284.35 282.60 277.22 316 444.83 199.00 133.1 271.42 273.90 280.35 300.18 317 1183.90 1125.45 1198.5 1142.67 1143.26 1144.80 1149.51 318 614.46 1190.13 798.5 1020.54 1014.73 999.63 953.21 320 897.51 964.01 931.6 944.42 943.75 942.00 936.21 321 638.73 912.62 665.4 831.93 829.17 821.98 799.90 322 0 . 0 7.44 5.25 5.17 4.98 4.38 104 Table 13 (Continued) SAMPLE CONCENTRATIONS (PPM) EXPONENTS OF THE GAMMA RAY ENERGY USED IN WEIGHTING NUMBERS LINAC REACTOR Spike Added______0^5______UO______2.0______4.0 Arkose (a sedimentary rock) 323 470.20 300.48 399.3 350.48 352.19 356.65 370.33 324 866.72 520.72 665.4 622.65 626.14 635.22 663.12 325 869.04 1176.27 1197.8 1085.76 1082.66 1074.60 1049.82 326 897.78 757.68 931.6 798.95 800.37 804.04 815.34 327 1939.26 1256.73 1330.8 1457.80 1464.69 1482.60 1537.63 328 1361.46 797.49 1064.7 963.64 969.33 984.13 1029.60 329 237.39 181.29 133.1 197.82 198.38 199.85 204.38 330 707.96 552.22 532.3 598.10 599.67 603.76 616.32 331 355.21 275.17 266.2 298.75 299.55 301.65 308.11 332 779.81 694.02 798.5 719.30 720.16 722.41 729.33 333 0 . 0 2.98 2 . 1 0 2.07 1.99 1.75 Quartz Diurite (an igneous rock) 334 375.12 205.12 266.2 255.20 256.92 261.38 275.09 336 1605.79 1196.82 1330.8 1317.31 1321.43 1332.16 1365.14 337 373.74 171.94 133.1 231.39 233.43 238.72 255.00 338 876.90 440.00 399.3 568.72 573.12 584.58 619.82 339 1056.03 885.93 1197.8 936.04 937.76 942.22 955.94 340 792.32 651.05 798.5 692.67 694.10 697.80 709.19 341 721.87 722.60 665.4 722.39 722.38 722.36 722.30 342 1297.21 1033.24 1064.7 1 1 1 1 . 0 1 1113.67 1120.59 1141.88 343 685.35 482.22 532.3 542.06 544.11 549.44 565.82 344 0 . 0 1.94 1.37 1.35 1.30 1.14 105 Table 13 (Continued) SAMPLE CONCENTRATIONS (PPM) EXPONENTS OF THE GAMMA RAY ENERGY USED IN WEIGHTING NUMBERS LINAC REACTOR Spike Added 0.5______ljO______S^O______4.0 Granite (an igneous rock) 345 699.67 740.48 798.5 728.46 728.04 726.97 723.68 346 848.17 1309.41 1330.8 1173.52 1168.87 1156.77 1119.58 347 135.79 298.85 266.2 250.81 249.17 244.89 231.74 348 691.86 675.28 931.6 680.16 680.33 680.77 682.10 349 • 816.33 1164.09 1197.8 1061.64 1058.13. 1049.01 1020.96 351 315.92 533.21 532.3 469.19 467.00 461.30 443.78 352 641.36 1047.59 1064.7 927.91 923.81 913.16 880.40 353 379.67 344.43 399.3 354.81 355.17 356.09 358.93 354 334.04 506.01 532.3 455.35 453.61 449.10 358.93 355 0 . 0 0 . 0 0 . 0 0 . 0 0 . 0 0 . 0 SAMPLE 303 LINAC DATA ABSENT **** SAMPLE 306 LINAC DATA ABSENT **** SAMPLE 319 LINAC DATA ABSENT SAMPLE 335 LINAC DATA ABSENT **** SAMPLE 350 LINAC DATA ABSENT **** References 1. 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Phys.. 74, 377 (1965). 114 124. Manfredini, A., M. Muchnik, L. Fiore, C. Ramorino, H.G. de Carvalho, R. Bo'sch, and W. Wolfi, II Nuovo Cimento, XLIV, 218 (1966). 125. Manfredini, A., L. Fiore, C. Ramorino, H.G. de Carvalho, and W. Wb’lfi, Nucl. Phys.. A127, 637 (1969). 126. Moretto, L.G., R.C. Gatti, S.G. Thompson, J.T. Routti, J.H. Heisenberg, L.M. Middleman, M.R. Yearian, and R. Hofstadter, Phys. Rev.. 179, 1176 (1969). 127. Reference 102; p.130. Vita Frank Thomas Campbell II was born on September 11, 1939 in Madera, California. Six years in a public school, two years in a parochial school and four years at Madera Union High School preceded graduation in June, 1957. After completing one year's study of physics at Fresno State College, he was drafted into the United States Army in October, 1958. While serving in the Artillery and the Signal Corps, he was involved in research and development in meteorology and he contributed to the Tiros I project. He separated from the Army in July, 1960, and returned to Fresno State College from which he received a Bachelor of Science Degree in Chemistry in June, 1963. He then entered San Diego State College from which he received a Master of Science Degree in Analytical Chemistry in January, 1967. At that time, he entered the Louisiana State University Graduate School and is presently a candidate for the degree of Doctor of Philosophy in Analytical Chemistry. 115 M AiHliN AI1UIN A«L> UlliiiSliS ItmruiVA Candidate: Frank Thomas Campbell II Major Field: Chemistry Title of Thesis: Simultaneous Determination of Gold, Mercury, Silver, Tellurium, and Uranium by Instrumental Neutron and Photon Activation Analysis. Approved: Major jy'ofessor and Chairman Dean of the Graduate School EXAMINING COMMITTEE: 'jtyL Date of Examination: Mav ^. 1971