estimated gas content. Xeither S2 nor CO2 is observable. ilt 17 minutes, however, a 1-division deflection indicates the Presence of Son. This one division, considering the system’s sensitivity to SOz, accounts for the entire sample volume. CONCLUSIONS
There are various means by which a gas chromatographic system can be
improved for enhanced sensitivity to specific gases. An investigation of detectors, columns, and operating ternperatures could perhaps bring the gas chromatograph into complete quantitative lvith the spectrometer for the analysis of bubbles in glass. I n the meantime, standard chromatographic systems can serve the useful purpose of qualitative and semiquantitative identification of major
constituents of medium and large size bubbles commonly found in glass. LITERATURE CITED
(1)TKlaasse, J. hf., HamPton, \v., Paper Lo. 6-H60, Winter Conference, Inst. Soc. Am., Houston, Feb. 1960. ( 2 ) Seerman, J. C., Bryan, F. R.,ANAL. ( 3 ) Todd,3 1 9B.532-5(1959). J., J . Soc. Glass Technol. 40, 32-ST (1966). R~~~~~~~~ for revielr- september 5, 1961. Accepted November 27, 1961.
Radiochemical Analysis of Irradiated Polyphenyls F. F. FELBER, Jr.,’ and R.
C. KOCH
Physical Sciences Department, Nuclear Science and Engineering Corp., Pittsburgh, Pa.
b
Analytical procedures have been developed for radiochemical determination of 15 radionuclides in small quantities of irradiated polyphenyls. After a carefully controlled treatment with perchloric acid, the procedures utilize sequential elemental separations to provide optimum analytical sensitivities, Nine of the fifteen nuclides have been analyzed in sufficient quantities and at net counting rates sufficiently high to permit statistical evaluation of the procedures. Average precisions, at the 9570 confidence level, achieved in a series of replicate analyses for these nine nuclides varied from 3.4 to 5.2%.
A
have been developed for radiochemical determination of 15 activation and fission products in irradiated polyphenyls and related organic materials. These procedures have been uspd routinely to determine radioactivity concentrations in the coolant of a n organic moderated reactor and to obtain data in engineering tests of systems for treatment of radioactive organic wastes. The procedures also have been used for activation analyses for trace constituents in a variety of solid and liquid organic materials. Many of the radioactive nuclides present in the irradiated polyphenyls are expected to be bound chemically in one of the several constituents of the matrix. This bonding may occur either because a bound atom is activated without a net rupture of its chemical bonds or because i t reacts, after its formation, with an irradiation-induced free radical NBLTTICAL PROCEDURES
Present address, Connecticut Aircraft Nuclear Engine Laboratory, Pratt and m’hitney Corp., Middletown, Conn. 280
ANALYTICAL CHEMISTRY
to form a stable molecule. For these reasons, i t was deemed necessary to destroy the organic matrix and produce a n aqueous solution in which the radioactive species are present as inorganic ions. Two methods of sample treatment were considered: combustion of the sample in a closed system with quantitative recovery of resultant volatile and nonvolatile combustion products, and dissolution with a strongly oxidizing solvent. The first method n a s rejected on the basis of two considerations : the difficulty of ensuring chemical exchange between tracer and carrier states of the multivalent elements, and the difficulty in quantitative recovery of the volatile carrier-free radioactivities liberated during the combustion. The diss-olution procedure selected involves sequential treatment of the polyphenyls with nitric and perchloric acids in the presence of macro quantities of carriers for the nuclides to be assayed. Due to the potential hazard associated with the vigorous exothermic reaction betreen perchloric acid and the samples, i t is necessary to control the sample size, the ratio of solvent volume to sample mass, and the rate a t which heat is applied to initiate the reaction. If attention is given to these parameters, the reaction rate of the perchloric acid with the organic material can be controlled with safety. The limitation on sample size and the desirability of minimizing the number of aliquots of sample to be dissolved dictate certain requirements for the analytical procedures. Since analyses for as many as 15 nuclides are required in one sample, serious limitations on analytical sensitivities may be introduced if separate aliquots of the sample solution are used for each nuclide. Therefore, a sequential separation pro-
cedure was devised for the required elements in a relatively large fraction of the solution. Two sample aliquots are dissolved. One solution is used for analysis of the cations, while the other is used for nuclides rt hich form anions. The individual elements are then separated, purified, and their radioactive nuclides are assayed by measurement of their respective beta or gamma radiations. ANALYTICAL PROCEDURES
Sample Dissolution. Separate, weighed aliquots of t h e polyphenyl sample, not exceeding a mass of 15 grams each, are combined in 4-liter Erlenmeyer flasks n ith known quantities of carriers for t h e desired nuclides and holdback carriers for other important nuclides. hpproximately 20 ml. of 16.Y HKOs are added per gram of sample to be dissolved. When no further reaction is observed with the boiling acid, the solution is cooled, and approximately 15 ml. of perchloric acid per gram of sample are added. The mixture is heated slowly until evolution of perchloric acid fumes. Heating is then terminated, since the reaction is sufficiently exothermic t o maintain itself nearly to completion, After the vigorous reaction has subsided, additional heating is usually required to effect dissolution of final traces of the sample. Each solution is then divided into three approximately equal portions for replicate analyses. Since the carriers are added t o the sample in knonn amounts prior to dissolution, it is not necessary to measure these aliquots quantitatively. The solutions for both the cation and anion analyses are evaporated to volumes of approximately 25 ml. Initial
Separation
Procedures. initial separation method for the three anionic nuclides, P32, 535, and Se7j, which hare been analyzed routinely
APU’IOSICELEMENTS. The
S
s.
Figure 1 . elements
II:.
I
sc
cs'po,),
Preliminary separation scheme for anionic
1% ith these procedures, is shown schematically in Figure 1. Sulfur is separated from the reduced volume of the solution of anionic nuclides by precipitation as BaSO?. Selenium is then precipitated as the metal by reduction Lvith SOz. Residual BaSOl may precipitate with the selenium. It is removed, if necessary, by filtration after dissolving the selenium in €IC1 in the presence of bromine. Since this BaS04 may have resulted from the oxidation of the SO, to sulfate, i t must be discarded. The phosphorus remains in the supernate during the selenium precipitation. It is separated from the perchloric acid medium by prccipitation as CATIOSIC ELEMEKTS. The initial separation method for the cationic radionuclides, Mnc4, Fe5y, COB, Co60, Zn65, Xsi6, S1.90, Zr9a, Sb122, Sb124, Cs137 and Bala, is indicatc,d in Figure 2. During evaporation of the perchloric acid solutions of tht>cations, manganese and antimony are precipitated as the olides. Subsequently, barium and strontium sulfates are precipitated by addition of 1 to 2 ml. of 3 6 9 HzS04. The supernate is then diluted to about 6N, and arsenic is precipitated as the sulfide. After volatilization of the excess H2S, iron and zirconium hydroxides are precipitated by addition of excess NH40H. Cobalt and zinc sulfides are then precipitated from the supcrnate with (NH,),S. The resulting supernate is evaporated repeatedly with nitric acid to destroy excess ammonium salts, and cesium is precipitated as the perchlorate. The precipitate of the mixed manganese and antimony ovides is dissolved in 12N HC1. The acidity is adjusted to 2.5-Y in HC'1, and antimony is precipitated as the sulfide with HzS. MnS is then precipitated from a n ammonical solution with (SH4),S. The precipitate of the mixed iron and zirconium hydroxides is dissolved in 6*V HC1 containing HF. Zirconium is separated by precipitation as BaZrF6, and iron is precipitated from the supernate as Fe(OH)3. Purification Procedures. T h e individual radionuclides are purified radiochemically a n d their respective beta or gamma radiations a r e then measured. T h e purification procedures are adapted from a selection
of established methods. Detailed information for these methods is provided in t h e Kuclear Science Series of Radiochemistry Monographs (1-4, 6I S ) prepared under the auspices of the National Academy of Sciences and National Research Council. End window, methane flow proportional counters are used for beta counting. X SaI(T1) Fell crystal is used to meawre the total gamma radioactivity at energies greater than 60 k.e.v. The radiochemical purity of the counting samples is verified by examination of the gamma spectrum obtained with a 256channel pulse-height analyzer. The gross gamma counting technique, with verification of spectrum purity, is used in the determination of most of these nuclides. -1summary of the analytical procedures follon s. Sulfur-35. The Bas04 precipitate from the initial anion separation procedure is thoroughly mixed M ith zinc ponder and reduced to the sulfide by roasting. The sulfide is dissolved in 3N HC1 in a small distillation flask, and HZS is distilled into a trap containing a Cu(N03J2 solution. The CuS precipitate is washed with boiling n ater and boiling ethyl alcohol, dried, and weighed. The washes with boiling solvents assist in maintaining counting samples of homogeneous thickness. Sulfur-35 is assayed by beta counting. Corrections for the attenuation of the 0.17-n1.e.v. beta radiations of S35 in the counting sample are made by comparison to a self-absorption curve prepared from a S3jstandard solution.
~ p ,
Selenium-75. The selenium precipitate from the separation procedure is dissolved in concentrated HBr containing sulfuric and nitric acids. Selenium bromide is distilled in the presence of air into a n ice-cooled water trap. Selenium metal is precipitated by reduction of the SeBrd with SOz. After a second distillation and repetitive metal precipitations, selenium is neighed as the metal, and Se7jis assayed by counting its mixed gamma radiations. Phosphorus-32. The Ca3(P04)*precipitate from the separation procedure and phosis dissolved in 1N "03, phorus is precipitated once as ammonium phosphomolybdate and twice as magnesium ammonium phosphate hexahydrate. The final precipitate is prepared and weighed under carefully controlled standard conditions, and P32 is assayed by counting its 1.71 m.e.1'. beta radiations through a 23 mg. per sq. em. aluminum absorber. The absorber is used to minimize the contribution of the weak beta radiations of any 25-day P33which may be present. Antimony-122, -124 The antimony sulfide precipitate from the initial cation separation procedure is dissolved in 122V HC1 in the presence of small quantities of cationic holdback carriers. The antimony is oxidized to the pentavalent state with bromine. After volatilization of any excess bromine, the antimony is extracted into isopropyl ether, followed by back extraction into a solution prepared from equal volumes of 3LV HC1 and 457, hydrazine. Finally, antimony metal is precipitated by reduction by CrC12, and weighed. The 2.8-day SblZ2and 60-day SbIz4are assayed by component analysis of decay curves obtained by beta counting. 3fanganese-54. Holdback carriers for zinc, cobalt, and iron are added to the acid solution of the llInOz (or MnS) precipitate from the initial separation procedure. After destruction of any nitrate ion by repetitive evaporation n ith HC1, the solution is adjusted to 12-1- in HCl and passed
EVIRRbTE
SOLN
H F. CO
I" AS
I i;
%
Zr
I --
I
I
I
Sb
Ba CI
I
0
ADD
12N
nci
T ,O
ION EXCH CM
s
950.
Lln
s Figure 2.
Preliminary separation scheme for cationic elements VOL. 34, NO. 2, FEBRUARY 1962
0
281
through a Dowex 1 anion exchange column. Alternatively, if several or all of these elements are to be assayed, solutions of the initial Mn02, Fe(OH)3, COS, and ZnS precipitates may be combined in a single 12N HCl solution which is passed through the column. I n this case, no holdback carriers are added. All of these elements, escept manganese, are efficiently adsorbed on the column The eluted manganese fraction is subjected to AgCl and CuS scavenging precipitations. Manganese carbonate is then precipitated and dissolved, and the manganous ion is osidized to permanganate with sodium bismuthate. The permanganate is reduced to manganous ion with oxalic acid after a Fe(OH)3 scavenging precipitation. Manganese is precipitated twice as MnOn by osidation with bromate, and the final precipitate is ignited and weighed as Mn304. N n S 4is assayed by counting its 0.84-m.e.v. photon. Cobalt-58, -60. The solutions of the mixed cobalt and zinc sulfides and iron hydrovide from the initial separation procedure are prepared for anion exchange separation as in the manganese procedure. After elution of manganese with 12.11 HC1, cobalt is eluted from the column n-ith 4N HC1. A Fe(OH)3 scavenging precipitation is performed, and co5alt is precipitated as potassium cobaltinitrite and is electroplated on a platinum disk from an NH4S04-NH40H solution. Cobalt is weighed as the metal, and Cess and Co60are assayed by a gamma spectrum analysis method described elsewhere (6). Cobalt-60 is determined through the 2.50-m.e.v. photopeak which represents the coincidence of its 1.17 and 1.33 m.e.v. photons, and CoSS, through its 0.81m.e.v. photon. Iron-59. After elution of the cobalt from the Dowex 1 column, iron is eluted with 0.5N HC1 and is precipitated as the hydroxide. The iron is extracted into isopropyl ether from 9 N HCl and then is back extracted into water. Following an additional hydroxide precipitation, the iron is dissolved in a n (NH4)H2POd(SHd'ZC03 solution, electroplated on a platinum disk, and weighed as the metal. Iron-59 is assayed by gamma counting of its 1.10- and 1.29-m.e.17. photons. Zinc-65. After elution of the cobalt fraction from the Dowex 1 column, the zinc fraction is eluted with 3 M ",OH. An iron hydroside scavenging precipitation is performed, after which ZnS is precipitated with (P;H4\2S. Zinc is precipitated as ZnHg(SCN)* and then is dissolved in H N 0 3 . After removal of mercury by precipitation as the sulfide, zinc is precipitated and weighed as ZnHg(SCN)d. Zinc-65 is assayed by measuring its 1.11-m.e.v. photon. Arsenic-76. The arsenic sulfide precipitate from the preliminary separation 282
ANALYTICAL CHEMISTRY
procedure is dissolved in a minimum volume of HNOI. Nitrate ion is destroyed with 12N HCl, and the solution is adjusted to 3hT. After addition of HI, arsenic is extracted into chloroform and back extracted into 1J1 HzS04. After a n additional extraction cycle, arsenic metal is precipitated with CrC12 and weighed. Arsenic-76 is assayed by counting its mixed beta radiations. Zirconium-95. The BaZrF6 precipitate from the separation procedure is dissolved in a nitric acid-boric acid mixture, and zirconium is precipitated as the hydroxide. After a second BaZrFG precipitation and dissolution, barium is removed by precipitation as the sulfate. Zirconium is precipitated successively with h"40H and cupferron, ignited, and weighed as ZrO,. The 0.72- and 0.76-m.e.~..photons of Zrg5 are counted promptly to avoid interference from the 0.77-m.e.v. photon of the 35-day Nbg5daughter. Barium-140. The mixed barium and strontium sulfates from the initial separation procedure are metathesized to the carbonates. The mixed nitrates are precipitated twice with fuming nitric acid. After precipitation of Fe(0H)a using carbonate-free T\",OH, barium chromate is precipitated from an acetic acid-ammonium acetate buffered solution. The supernate is reserved for strontium analysis. The barium is further purified by precipitation of BaClz from an HC1ether solution. After a second Fe(0H)o scavenging precipitation, barium is precipitated and weighed as BaC03. Barium-140 is assayed by gamma spectrometric measurement of the 1.60m.e.v. photon of the 40.2-hour Lala daughter as i t g r o m into equilibrium in the purified sample. Separation time for Lala growth is taken as the time of the second ferric hydroxide precipitation. Strontium-90. A few milligrams of iron carrier are added to the supernate
Table 1. Mean Precisions Achieved in Analyses of Radionuclides
Kuclide P 32
s 35
P*ln54
FeSg Co58 cow Zne6
Se75 Sr90
Replicate Assays" (sets)
Mean Precisionb (%)
23
4.1 f0.9
32 -~ 16 17 17 18
4.6
8 14 7
* 0.8 3.4 * 0 5 4 . 7 =!= 1 . 0
4.7 1 . i 4 7 z t 1 0 5.2 f 2.1 4.3 f0 . 9 5.0 i2.5
Number denotes sets of replicate assays. Mean value of precisions, at the 95% confidence level; error is the standard error of the mean value. 4
from the BaCr04 precipitation from the barium procedure, and Fe(OH)3 is precipitated with carbonate-free NH4OH. Strontium is then precipitated from the supernate and weighed as SrC03. The precipitate is dissolved in HC1, a known quantity of yttrium carrier is added, and the YgOdaughter is allowed to grow into the purified strontium sample. Zero time for the gron th of YyOis taken as the time of the last Fe(OH)3precipitation. After 3 to 7 days, Y(OH), is precipitated with carbonate-free KH40H. The time of this precipitation is taken as the end of Y90gronth in the strontium sample. .I second Y(OHI3 precipitation is made in the presence of a small quantity of strontium holdback carrier. Yttrium is then extracted from 161V H N 0 3 into a benzene 60 v./% tributyl phosphate solution which has been previously equilibrated R ith 16N "03. After back extraction into water and precipitation as the hydroside, yttrium is precipitated as the ovalate, ignited, and weighed as Y203. Yttrium-90 is assayed by beta counting, and the Sr90 disintegration rate is computed after correction for the growth and decay of the YgO and for the chemical yields of both elements. Cesium-13i. The CsC'104 precipitate from the initial separation procedure is dissolved in 0 . 3 s HCl, and the solution is scavenged once with CuS and twice with Fe(OII)3. The supernate is evaporated repeatedly FT-ith nitric acid to remove ammonium salts. After final traces of KH4K03 are removed by volatilization, cesium is precipitated and u eighed as CsC104. Cesium-137 is assayed by counting its 0.66 m.e.v. photon. DISCUSSION
These procedures have been used routinely in this laboratory for analyses of irradiated polyphenyls and related materials. I n routine use, the chemical yields achieved with these procedures varied from 50 to 90%, after taking into account the aliquot factor which they also measured. The specific activities of the respective nuclides in the various samples have ranged from the limits of the analytical sensitivities upward several orders of magnitude. Furthermore, no significant activity is induced in the major elemental constituents of these samples. Therefore, decontamination requirements for the purification procedures were relatively modest, seldom exceeding two to three orders of magnitude. These procedures fulfilled these requirements. The relatively small quantities of radioactivities did not permit evaluation of the ultimate decontamination factors achievable with these samples.
The precision of the analytical data has been evaluated for those nuclides for which a statistically significant number of assays has been performed. For this purpose, data obtained in replicate analyses for some of these nuclides in a set of 35 samples have been employed. Two criteria were used to select data for evaluation of the precisions: The net counting rate in the individual assay sample was greater than 5Oy0 of the counter background, and a minimum of six sets of replicate assays, satisfying the first criterion, was available for a given nuclide. Analytical data, which fulfilled these two criteria, have been obtained for nine nuclides: P32,P5,1W4,Fe59,Co5*, CoB0, ZrP5, Se7j, and Sr9'3. The precision, a t
the !%yo confidence level, was calculated for each set of replicate analyses for the respective nuclides. The value of the mean precision for each nuclide is shown in Table I with the number of sets of replicate assays from which the mean value was derived. The values vary from a minimum of 3.4y0for Fe59 to 5.2y0 for ZnG5. These precisions are deemed adequate for most applications for which these procedures may be used. LITERATURE CITED
(1) Bate, L. C., Leddicotte, G. W.,eds., Natl. Acad. Sci.-Natl. Research Council R e p t . NAS-NS-3041 (1961). (2) Beard, H. C., ed., Zbid., NAS-NS3002 (1960). (3) Finston, H. L., Kinsley, M. T., eds., Zbid., NAS-NS-3035 (1961).
(4) Hicks, H. G., ed., Zbid., NAS-NS-3015 (1960). (5) Koch, R. c., Grandy, G. L., ~ ~ N A L . CHEM.33,43 (1961). (6) Leddicotte, G. W., ed.,, N a f l . Acad. Sa.-Natl. Research Counczl Rept. NASNS-3018 (1960). (7) LeddicdGe,. 6. W., ed., Ibid., NASNS-3030 (1961). (8) Leddicotte, G. W., ed., Ibid., in publication. (9) Leddicotte, G. W.,ed., Zbid., NASNS-3054 (1962). (IO) Maeck, W. J., ed., Ibid., NAS-NS3033 (1961). (11) Nielson, J. hf., ed., Ibid., NAS-NS3017 (1960). (12) Steinberg, E., ed., Zbid., NAS-NS3011 (1960). (13) Sunderman, D. N., Townley, C. W., eds., Ibid., NAS-NS-3010 (1960).
RECEIVEDfor review June 19, 1961. accepted December 11, 1961.
Radiochemical Determination of Yttrium and Promethium A Precipitation Technique M. E. PRUITT,IR. R. RICKARD, and E. 1. WYATT Analytical Chemistry Division, Oak Ridge National laboratory, Oak Ridge, Tenn.
F A procedure is presented for separating yttrium from the lanthanum group of rare earth elements by precipitating the latter as iodates. Yttrium remains in solution and is determined separately. In fission product mixtures that have cooled a year or longer, Pm'47 can be determined readily after the separation of the lanthanum group elements from yttrium. Other applications of the general technique are suggested.
R
radiochemicsl analyses are required in the control of the proccss for the large scale recovery of long livcd fission products. The feed materials for the rccovery process most often are the 11-aste solutions from processes for the rccovrry of irradiated reactor fuels. The solutions usually have becn cooled for several years to rid them of short lived radionuclides. Some of the radionuclides recovered are: SrgO,Csla7, Ce144, and Pml47. Of these PmI47 has been the most difficult to determine because of the presence of other rare earth radionuclides in old fission product mivtures and because PmI47 is a weak beta emitter with no associatrd gamma emission. The rare earth radionuclides present in mixed fission products vary with bombardment timc., cooling time, and APID
the history of the sample. Those likely to be found in fission product mixtures that have cooled for a year or more are listed in Table I. Since classic methods (18, 96) can be used to separate cerium from the trivalent rare earth elements, it becomes necessary only to separate promethium, praseodymium, samarium, and europium from yttrium. When this latter separation is accomplished, Pm147 can be determined rather easily in the remainder of the group n-ithout further separation because Pr144 will decay within 2 to 3 hours, Sm151 is too weak to interfere with GeigerAluller beta-counting techniques, and Eu155 will be present in negligible amounts. Ion exchange techniques for separating the rare earth elements from each other have been reported by Cuninghame (5j, Ketelle and Boyd (IW), Xervik (17), Petrow (80), and many others. However, ion exchange procedures for determining Pm147 are not easily adapted to the rapid analysis of a large number of samples. Extraction techniques for separating rare earth elements have been used by Kleinberg (16), Handley (9), Stevenson and Servik (WS), and others. Various precipitation techniques have also been described (1-3, 1 1 , 1 6 , 2 2 , 2 ~ ) . The development of a procedure for separating yttrium from the lanthanum
group elements by iodate precipitation of the latter is described herein. This procedure has been used a t the Oak Ridge Xational Laboratory for the past 3 years (21j . Although the radionuclides of yttrium are not valuable from a production standpoint Y9O and Ygl are nearly always present in fission product mixtures. The separation of these radionuclides from the lanthanum group elements is imperative if PmI47 or any of the shorter lived rare earth radionuclides are to be determined v i t h any degree of accuracy. Also, it is frequently desirable to determine Y90 and/or Ye1 in certain samples. Since promethium has no stable isotope that can be used as a carrier for PmI4', it is necessary to use a stable rare earth element that has chemical
Table I. Rare Earth Radionuclides Present in Aged Fission Products
Radionuclide Y" Y91
Ce14' Pr14( PmL47 Smlbl Eu166
Half Life 64.2 h 57.5 d
285 d
Fission Yield, yo (Daughter of SPOO) 5.4
6.0
17.27 m (Daughter of Ce14') 2.64 y 2.7 -93 y 0.45 1.7 y 0.03
VOL. 34, NO. 2, FEBRUARY 1962
283
