with conventional x-ray equipment, provided a suitable line voltage regulator is used. A practical period of time over which counts may be accumulated depends upon accuracy required, optimization of geometry, instrumentation dead time, and degree of uranium concentration. In this determination, no attempt was made to obtain the maximum counting rate possible. Using available laboratory equipment, a rate of 220,000 counts per minute, corrected for instrument dead time, was obtained with an x-ray beam current of approximately 0.3 ma. This provides measurement accuracy in the neighborhood zkO.l% in a practical counting time. Fewer counts were accumulated for the determinations listed in Table I, with subsequent decrease in the accuracy of measurement. Estimated chemical losses during the extraction process decrease the accuracy to =tO,5%, Short-term electronic instability ef-
fects also cgntribute, so that the overall accuracy of uranium determination is *0.770',. CONCLUSIONS
The feasibility of applying Rayleigh scattering measurement techniques to the determination of high Z atoms in low Z media is well established. Applications requiring only moderate accuracy of measurement, such as onstream process control of high Z materials, would benefit by not requiring chemical processing. High precision quantitative analyses similar to the one described in this report can be accomplished with a minimum of sample preparation and analysis time, compared to conventional wet chemistry and/or x-ray absorptiometry methods. LITERATURE CITED
(1) Connally, R. E., Yucleonics 17, KO. 12, 98-102 (1959).
Table 1.
Summary of Data
Type of Unknowna A B Total counts h'l
N, A',
Concentration, grams/liter
c, cs
cz UCZ
2,837,163 2,761,403 3.424.974 2.998.175 2;669;390 217971186 6,7285 11.885 5,2565 0.0212
Accuracy of measurement, 7c zk0.46 A. Aluminum impurity. B. Stainless steel impurity.
5.7735 7.8130 6.0815 0,0190 10.31
(2) Ziegler, C. A., Bird, L. L., Chleck, D. J., -4NAL. CHEM.31,1794-8 (1959). RECEIVEDfor review April 14, 1960. Accepted August 24, 1960.
Rapid Method for Separation and Analysis of Radioactive Fission Gases R. C. KOCH and G. L. GRANDY Chemistry Department, Nuclear Science and Engineering Corp., Pittsburgh 36, Pa. .An analytical method and apparatus have been developed for rapid determination of the concentrations of radioactive fission gases in helium streams. The method involves sampling of the helium stream, quantitative separation of the xenon and krypton from the helium, from other fission products, and from each other, and gamma spectrometry assays for isotopes in the separated fractions. Charcoal beds are used for both the sampling and the gas chromatographic separation steps. Analytical procedures have been developed for quantitative analysis of KrS5m, KrX7, XelB2, Xe136, and Xe13* in helium streams containing mixed fission gases. Precisions not exceeding 770 were achieved for these nuclides. In addition, a semiquantitative analytical procedure for 3.2-minute Krs9 was developed. This method has applications for fission gas analyses in both reactor and fuel processing plants.
A
ANALYTICAL method for radioactive fission gases in various media has been developed and tested to meet a need which exists in many areas of reactor technology. The method has been used to sample, separate, and assay individual fission gas nuclides in both static and dynamic gases. RAPID
Modifications of the procedures have also been used for assay of solid or liquid samples. Rapid analyses of these gases can provide data for a variety of research, engineering, and operational programs. This paper describes the development of the method. A general procedure for separation of xenon and krypton has been described by Koch and Grandy ( 7 ) . The procedure is based on the principles of gas chromatography, utilizing activated charcoal as the fixed phase and helium as the sweep gas. On the basis of this separation method, a complete analytical method and an apparatus have been devised for the rapid determination of the concentrations of radioactive fission gases in helium streams. The method provides for sampling of the helium stream, separation of the xenon and krypton from the helium and from other fission products, their rapid quantitative separation from each other, and specific radiometric assays for selected isotopes in the separated fractions. Two general methods of sampling gas streams are available: a static method, wherein a known volume of the gas a t a given temperature and pressure is removed from the system, and a dynamic method, Therein a known fraction of the stream passes through
a physical or chemical filter for a predetermined time to remove quantitatively those species of interest. I n many applications, a dynamic method, using a sampling device on a bypass stream, is especially desirable to avoid installation of costly, remotely controlled static samplers or to preserve the mass balance of the major constituent in the stream. The use of charcoal adsorption beds of varying dimensions for quantitative removal of xenon and krypton from gas streams has been demonstrated (1, 2, 7-9) for a variety of charcoal temperatures and gas flow rates. Also, the subsequent desorption of the xenon and krypton separates them from the nonvolatile or quasivolatile species, including iodine (6),which may also be deposited on the sampler. I n addition, Glueckauf (4) has discussed the effect of beta decay heat on the chromatographic separation of highly radioactive krypton and xenon. Because previous work (7) had indicated that 0.4-inch diameter, 16inch long beds of -40 50 mesh charcoal could be used both for sampling and separation operations for a helium system, these beds were selected for further study. Data were required for the maximum quantitative retention times and the elution char-
+
VOL. 33, NO. 1, JANUARY 1961
0
43
acteristics for the two gases using these beds under specific operating conditions. The program was directed specifically to the development of analyses of the fission gases in helium streams a t approximately 75" F. and a t flow rates up to 0.02 c.f.m. However, the developed methods are readily adaptable to other flow rates and temperatures and to other gas streams. DEVELOPMENT EXPERIMENTS
The properties of the adsorbent beds were characterized a t three readily attainable charcoal temperatures, 75", 32", and -112" F., and a t three helium flow rates, 0.02, 0.008, and 0.0026 c.f.m., which spanned the temperature and flow rate ranges of interest in this application. Runs xere performed for system blanks a t each flow rate with an empty adsorbent container to determine the apparent retention of the tracer due to flow time and its dispersion during transit from the injection site to the monitor. To determine the required retention efficiencies and elution patterns, a series of tracer experiments was performed using 10.3-year Kr85 and 5.27-day Xe133. These experiments involved the injection of a charge of tracer into the helium, upstream from the charcoal bed, and the measurement of the rate of elution as a function of time after injection. The elution rate was continuously recorded with an on-stream monitor (6). The
Table I.
apparatus and procedures for these experiments were essentiafiy identical to those described elsewhere ( 7 ) . Preliminary single-tracer experiments were run to characterize the behavior of the individual tracers. Dualtracer experiments were then performed to demonstrate specific separation methods for the two gases. Since only a limited supply of Xe133was available, it was reserved primarily for the latter experiments. In addition to the tests using the 16-inch charcoal beds, several experiments were performed to determine the properties of 2-inch charcoal beds having the same diameter, since it was desired t o use small beds as catcher traps to collect the separated gas fractions and to contain them for assay by gamma spectrometry. The elution curves of the tracers obtained from the on-stream monitor showed the quantity of the tracer released from the charcoal as a function of time after its injection. The elution curves, including those for system blanks, exhibited skewed-Gaussian type distributions. Average curves for replicate experiments were constructed by averaging their respective times a t selected fractions of peak activity. Prior to averaging, the individual elution curves mere normalized to unity a t peak height, after correction for counter background. Normalization facilitates the averaging process by eliminating the need for stringent control of the magnitude of the re-
Data for Retention and Elution of Xenon and Krypton on Charcoal Beds
Temperatye,
Helium Flow Rate, C.F.M. 0.02 0.008 0.0026 0.02 0.008 0.0026
TipD, Ti % A , TpJ Tp, Min. Min. Mm. Min. 2.16 0.78 0.64 0.65 5.75 2.11 2.56 2.08 Kr a 14 7.79 5.75 5.53 Kr5 5.60 2.71 3.64 2.52 Kr 13 5 10.9 8.5 7.8 Kr 31 25.2 18.7 Kr 17.4 8.3 6.26 4.09 4.59 Kr 0.02 22.9 17.9 14.5 13.7 Kr 0.008 89 61 43 Kr 0.0026 39 231 346 Kr 164 173 0.02 78 44 58 45 0.02 Xe 238 168 133 34 Xe 0.02 6.5 3.57 2.51 2.66 Kr 0.02 41 -98 54 40 Xe 13.2 9.9 8.1 6.1 Kr 0.008 75 204 155 35 131 Xe 7.8 5.69 4.17 4.37 Krb 0.02 75 26.4 27 26.0 25.2 Xe 7.4 4.31 3.19 3.05 Kre 75 0.02 ~ 8 6 43 56 41 Xe 50 81 -112 33 Kr 1 32 0.02 118 216 Kr d 70 -112 0.008 66 a D a h for apparent retention of tracers by experimental apparatus. Data for accelerated desor tion of xenon after krypton elution. Data for effect of thermafdesorption from sampling bed on elution pattern8 from chromatographic column. d Data for %inch catcher trap.
Tracer Kra
44
F. 75 75 75 75 75 75 32 32 32 -112 75 32 75
ANALYTICAL CHEMISTRY
spective tracer charges. The averaged elution curves were then corrected for the apparent retention by the apparatus as determined from the blank runs. This correction consisted of subtracting the time a t selected amplitudes on the blank elution curve from the time a t the corresponding amplitude on the averaged elution curve. The corrected curve then represents the retention and elution of the tracer by the charcoal bed only. Data characterizing the various elution curves are shown in Table I. Column 1 of the table lists the tracer used; column 2, the temperature; column 3, the helium flow rate; column 4, Tal the elapsed time from injection to initial appearance of the tracer a t the detector; column 5, Tl%a, the time until the magnitude of the curve rises to 1% of the peak value; column 6, T p , the time to the peak; and column 7 , the time to decrease to 1% of the maximum. All values of time refer t o the elapsed time from tracer injection. The time a t which the tracer becomes unmeasurable is not an important parameter since variations in the counter background and the amounts of tracer in different charges may occur. The values of T A for the two tracers represent the maximum sampling times for their quantitative removal from the helium stream under the specific operating conditions. The values of T 1 % D represent the time5 rcquired to elute -99.8y0 of the tracer charge The data in Table I show that, for the combinations of operating parameters investigated, the appearance (retention) times for xenon in all cases exceed the corresponding effective disappearance or removal times for krypton, The separation is, therefore, shown t o be quantitative. The most rapid separation was obtained a t a helium flow rate of 0.02 c.f.m. with a charcoal bed temperature of 75" F. I n this case, the krypton is eluted in less than 6 minutes, n-hile the xenon is retained for over 40 minutes. However, an even greater degree of separation can be obtained a t 32" F. nith expenditure of additional elution time. Data for the dual-tracer experiments confirmed those ohtained with the individual tracers. Figure 1 shows the separation achieved a t a charcoal temperature of 75" F. and a helium flow rate of 0.02 c.f.m. Figure 2 shoms the unnormalized elution data from a single expeyiment at the same conditions, These curves demonstrate that very well defined separations are achieved with a 16-inch charcoal bed. The shortest quantitative elution time observed for xenon was -78 minutes. Since the krypton was eluted in less than 6 minutes, it was deemed desirable to accelerate the desorption of
T I M E , MINUTES
Figure 1.
Separation of xenon and krypton on charcoal at
75' F.
Helium purge rate, 0.02 c.f.m. Krypton fraction is eluted tlrrt Elution curves are normalized to unity at maximum
xenon after the krypton had been eluted. Two methods were considered: increasing the helium flow rate, or raising the temperature of the chromatographic column. The latter method was selected because it appeared more compatible with the use of short catcher traps. The degree to which an increase in column temperature accelerates xenon desorption was determined. The mixed tracers were injected onto a charcoal bed, desorbed, and separated on a 16-inch bed, using a helium flow rate of 0.02 c.f.m. After elution of the krypton, the second bed was heated to -400" F., and the xenon was eluted. The resulting data (Figure 3) indicate that the xenon can be removed from
IO'
the column within 10 minutes after heat is applied. Therefore, if heating is applied as soon as possible following the krypton elution, the separation procedure can be completed within about 20 minutes after sampling. * Tests were also performed on the 2inch charcoal bed proposed for collection of the separated gas fractions. The characteristics data. shown in Table I, indicate that its retention
time for krypton, a t -112' F. and a given helium flow rate, is greater than the krypton disappearance times from the 16-inch trap a t the two higher temperatures and the same flow rate. Therefore, 2-inch traps were selected for collection and containment of the separated gas fractions. These traps were constructed from 2-inch lengths of 0.5-inch outside diameter copper tubing with an adaptor a t each end for small, helium leakfree shutoff valves. The outer end of each valve had a specially adapted Swagelok fitting for convenient removal from the system. The length of the charcoal bed was defined by soldering an 80-mesh copper screen to the shoulder of each adaptor. Special precautions were taken to ensure that these charcoal beds were firmly packed to prevent channeling of the fission gases. A general analytical procedure was formulated on the basis of these experiments. The procedure consists of the removal of xenon and krypton from a helium stream by the sampling bed, their subsequent desorption by heating and purging with an auxiliary helium sweep gas, their chromatographic separation, their collection and containment on the catcher traps, and gamma spectrometry measurement of the isotopes in the separated fractions. To determine whether the increase in gas temperature during their desorption from the sampling trap affected the elution properties on the chromato-
DATA N O T CORRECTED FOR SYSTEM RETENTION
-
I' 0. 0'
-c > c v
L
Id-
" t = Q
IO L/ 10%-
0
30
40
TIME, MINUTES
Figure 2.
0
5C
Separation of xenon and krypton on charcoal at
75' F. Helium purge rate, 0.02 c.f.m. Krypton fraction is eluted first
Figure 3. krypton
IO
15 20 T I M E , MINUTES
r5
30
Accelerated separation and elution of xenon and
Helium purge rate, 0.02 c.f.m. Krypton eluted flrrt a t 75' F. Temperature raised to 400' F. at 23 minutes to accelerate xenon elution
VOL 33, NO. 1, JANUARY 1961
0
45
graphic columns, an experiment was performed in which a dual-tracer charge was injected onto a sampling bed. The bed was isolated, its temperature was raised to between 300" and 400" F., and the tracers were swept through the chromatographic column, a t 75" F., with a 0.02-c.f.m. helium sweep flow. The resulting elution data, also listed in Table I, are not significantly different from those obtained under the same separation conditions in the other tracer experiments. Therefore, this desorption procedure was adopted.
Figure 4.
Analytical apparatus
pulse height analyzer, a count rate meter, and a recorder. A holder assembly was provided to position the catcher traps a t various geometries with respect to the detector. The counter was calibrated with a series of standard sources.
DEMONSTRATION EXPERIMENTS
An apparatus, shown schematically in Figure 4,was constructed for demonstration of the analyticaI procedures. The apparatus consisted of a 16-inch charcoal sampling bed, an identical bed for use as a chromatographic column, removable 2-inch catcher traps, and suitable Aowmeters. A system of valves and bypasses provided flexibility for testing alternate separation procedures.
Three specific procedures, which are variations of the general sampling and separation method, were investigated, Procedure 1 involves operation of the sampling bed and the catcher trap a t -112" F., and the chromatographic column a t 75" F. After sampling the fission gases in the helium transport stream for a predetermined sampling time, less than the retention time for krypton, the sampling bed is isolated, and its temperature is raised to -400 " F. The helium sweep gas, a t 0.02 c.f.m., is then passed through this bed, the chromatographic column, and the catcher trap, until the separated krypton fraction has been eluted from the column and transferred to the catcher trap. The chromatographic column, which contains the xenon fraction, is then isolated and heated, and the xenon fraction is eluted to a second catcher trap. The two traps are then removed from the system for gamma spectrometry measurements
The validity and reproducibility of the general sampling and separation method and of the subsequent radiometric assays a-ere demonstrated by using this apparatus to analyze a helium transport stream containing mixed fission gas nuclides of various half lives. An auxiliary helium supply provided the sweep gas for the chromatographic separation and transfer operations. In the studies of these procedures, the separated xenon and krypton fractions were assayed using a 2 inch X 2 inch NaI(T1) crystal operating with an automatic scanning, ?ingle-channel
Procedure 2 permits sampling and separation in a single operation and is especially useful when short sampling times are sufficient. This method involves operation of the sampling bed, a t 75" F., and the catcher trap, a t -112" F., in the gas stream to be assayed. The chromatographic column is not used. After sampling flow is terminated, the auxiliary helium flow sweeps the krypton remaining on the sampler to the catcher trap. The xenon fraction, which remains on the sampling bed, is then transferred to a second catcher in the usual manner. The limitation on theasampling time is defined by the requirement that there be sufficient time after sampling to transfer the krypton remaining on the sampling trap to the catcher without exceeding the maximum krypton retention time of the catcher. For helium flow rates of 0.02 c.f.m., the limit is approximately 15 minutes. However, if only xenon is to be measured, this limit may be extended to about 30 minutes, since the catcher trap may be bypassed until krypton elution is effected. Therefore, the retention time of the sampling bed, less the krypton elution time, becomes the limiting parameter. Procedure 3 is similar to the second, except that the gas stream to be assayed passes through the sampling bed and the chromatographic column, held a t - 112" F. After sampling, the krypton and xenon fractions are transferred to their respective catcher traps. The sampling time for this procedure (at 0.02 c.f.m.) is limited to -30 minutes
A - 0 E A Y OF Rbm
\
%b\'
1
C - R E L A T I V E VALUES OF
IO1
10.01
0
12
36
24
T I M E AFTER Kr-Rb
Figure 5.
46
48
SEPARATION. HIN.
Decay curve for Rb8'
ANALYTICAL CHEMISTRY
so
L
-
0
C = R E L A T I V E VALUESOF Dx, (1,)
0.01 20
40 60 110 100 I20 TIME A F T E R X * - C I SP*MmOM,YN.
Figure 6.
I40
Decay curve for C S ' ~ ~
Table II.
Data for Reproducibility of Spectrometry Procedures
Decay Sampling Time to He Flow Bed R(K r q , R(KFrn), Sampling Xe-Kr Atom/Min. Atom/Min. Rate, TemBerature, Time, Separation, Procedure C.F.M. F. ( x 10-1 ( X 10-8) Mill. Min. Used 2.18 0.02 45 30 2.17 -112 45 30 1.94 1.89 0.02 -112 45 30 2.33 2.38 0.02 -112 2.29 45 30 2.10 0.02 -112 2.13 45 30 2.12 0.02 -112 Av. 2.13 f 0.13 2.17 f 0.15 Decay Time to Xe-Cs R(Xe1J3), R(XelU), Separation, Atom/Min. Atom/Min. Min. ( x 10-9) ( x 10-9) 1.30 1.46 -75 20 10 2 0.02 -75 20 10 1.35 1.48 2 0.02 1.47 2 0.02 -75 20 10 1.31 -73 20 10 1.25 1.46 2 0.02 Av. 1.30 f 0.04 1.47 zk 0.01 2a 0.02 -75 20 10 1.10 1.30 2 0.02 -75 20 10 1.06 1.20 2 0.02 -75 20 10 0.97 1.13 2 0.02 -75 20 10 0.99 1.20 Av. 1.03 =I=0.05 1.21 zk 0.06 The following experiments were performed after a change in fission gas source conditions.
R(XeI*a), Atom/Min. ( x 10-8)
2.56 2.62 2.71 2.64 2.64 & 0.06 2.30 2.12 1.94 2.10 2.13 & 0.13
5
by the maximum retention time of the sampling trap for xenon, less that time required for elution of krypton. For each of the above procedures, either one or both of the gas fractions can be taken for assay. Those fractions not desired can be easily bypassed to a waste facility for disposal. Three isotopes of each element were studied in this program: 4.4-hour K r 8 5 m , 78-minute Kr87, 3.2-minute KrS9, 5.27day Xe133, 9.2-hour Xe186, and 17minute Xe138. The longer lived isotopes in each fraction can be separated and analyzed using any of the three procedures. Kr85m was determined by measuring its 150-k.e.v. photon; for K r 8 7 , the 403-k.e.v. photon was used; for Xe139 the 250-k.e.v. photon; and for Xe133, the 81-k.e.v. photon. For each of these nuclides, repetitive scans of the spectrum were made in the vicinity of the selected photopeak. The repetitive scans provided measurements of their half lives. The observed values were in good agreement with literature values. The activity due to each photon was determined by calculating the area under each photopeak, after correction for Compton interactions of higher energy photons. After further correction for counting efficiency and gamma yield, the disintegration rate for each nuclide was corrected for decay from the end of the sampling period. The shorter lived isotopes, Xe138 and Kr89, were determined by measurement of their respective decay products, 32-minute CS~Mand 17-minute Rb89. One method for such analyses involves
an initial separation of the parent from the daughter, and measurement of the decay product as i t is formed in the presence of the purified parent. For short-lived species, a well defined separation time is required. Procedure 3 was used to determine Kr89. The krypton-rubidium separation time, which is zero time for the growth of Rb89 on the catcher trap, is defined as that time a t which the helium sweep flow was initiated through the heated chromatographic column containing the separated krypton fraction. The Rb89 was determined by measuring the photopeak due to its 1.26m.e.v. photon. The decay of this photopeak in a typical sample is shown in curve A of Figure 5 . To correct the observed Rb*9 activities to those of K r 8 9 , it is necessary to consider the relationship between the decay of the purified parent and the growth and decay of the daughter. It is readily shown (3) that the ratio of the disintegration rate of the daughter, Dz(t), a t an arbitrary time, t, after separation, to that of the parent a t the time of separation, D1(t8),is given by Equation 1
where XI and 12 are the decay constants of the parent and daughter, respectively. Curve B in Figure 5 shows this ratio as a function of elapsed time after separation. Curve C shows the constant value of Dl(f,) obtained when the correction factor from curve B is applied to curve A . The corrections for counting efficiency and gamma yield
for Rb89 have not been made in this example, because the gamma yield is not known. However, the reproducibility obtained in the individual photopeak analyses indicates that this procedure is satisfactory for relative measurements of Kr89. To determine the relative disintegration rate of KrB9 in the sample taken, further correction is necessary for its decay during the interval between sampling and the krypton-rubidium separation. Procedure 2 was used for determination of XeIS. The xenon-cesium separation is defined as that time a t which the helium sweep flow was started through the heated sampling bed. The Cs138 was determined by measuring the growth and decay of its 1.43m.e.v. photon. A typical growth and decay curve obtained for this photopeak is shown as curve A in Figure 6. The correction curve, calculated from Equation 1, is presented as curve B , while curve C shows the constant value obtained for the data corrected to Xe1a activity a t the time of separation. The quantity of a nuclide in a given analytical sample is related to its mass flow rate in the transport gas stream by Equation 2.
where R
the mass flow rate of the nuclide, atomjminute 7 = the sampling period, minutes A = the decay constant, minute-' =
VOL. 33, NO. 1, JANUARY 1961
e
47
Table
Procedure Used
He Flow Rate, C.F.M.
1 1 1 1
0.008 0,008 0.008 0,008
Ill.
Data for Reproducibility of Sampling and Separation Procedures
He Purge Rate, C.F.M. 0.02 0.02 0.02
Sampling Time, Min. 45 45 20 45
Decay Sampling Time to Bed Xe-Kr Temoperature, Separation, F. Min. -112 30 -112 30 - 112 30 -112 30
R(Kr*sm), AtomlMin.
R(KrS7)! AtomlMin.
/x
lo-)
( X lo-*:
...
2 10
... ... ...
2.16 2.01 0.02 2.01 Av. 2.07 3Z 0.07 3 0,008 0.008 45 -75“ 30 1.5gb 3 0,008 0.008 45 -75“ 30 1.57 1 0,008 0.02 45 - 112 30 1.51 Av. 1.56 3Z 0.04 Separated on sampling bed and contained on chromatographic column at -112‘ F. The following experiments were performed after a change in fission gas source conditions
a
b
D(T)
=
the disintegration rate of the nuclide on the sampling bed, atom/minute
This correction factor was applied to correct the results of individual assays to a common basis-i.e., the number of atoms per minute arriving at the sampling trap. After the methods for identification and determination of the several nuclides were established, a series of experiments mas performed t o test the reproducibility of the gamma spectrometry techniques for each nuclide under identical sampling and separation conditions. Procedure 2 was used for the krypton samples, and Procedure 1, for xenon. Experimental data for K F m , Krs7, Xe133,Xe136, and Xe138are shown in Table 11. The precision of the assays was about 7% for K r 8 5 m and K r S 7 and somewhat better than iyofor the xenon isotopes. The reproducibility of the sampling and separation procedures was demonstrated in additional analyses for krypton by varying the flow rates of the transport gas or the sweep gas, the sampling time, or the specific separa-
tion procedure. The additional data are summarized in Table 111. The first group of data were obtained under the same experimental conditions as the krypton data in Table I1 and are in good agreement The latter group mere obtained under somewhat different fission gas source conditions. The standard deviations obtained in these tests are less than those in Table I1 Therefore, the deviations may be attributed primarily to the spectrometry techniques. I n summary, a rapid method has been developed for sampling, separation, and gamma spectrometry assay of five niediuni and short lived fission gas nuclides, as n ell as a semiquantitative method for 3-minute KrS9. Specific procedures. rvhich yield data nith a precision better than 7’%> have been demonstrated for the analysis of these six nuclides in a helium stream having moderate velocity and ambient temperature. I
ACKNOWLEDGMENT
The authors thank R. H. Marsh for his assistance in portions of thii pro-
1.25* 1.12 1 2; 1 31 zk 0 07
gram and Paul Kruger for hi. helpful comments and suggestions. LITERATURE CITED
(1) Browning, W. E., Bolta, C C.. U. S. Atomic Energy Comm. Rept. ORNL-
2116 119571. %
,
( 2 ) Browning, W. E., ad am^, R. E., Ackley, R . D , Ibid, ORNL-CF-59-6-
47 (1959). (3) Friedlander, G., Kennedy, J. W., “Introduction to Radiochemistry,” Wiley, New York, 1940. (4)Glueckauf, E., Atomic Energy Research Establ. 1Gt. Brit.) CR-2415 (1957); CR-2434‘(1958) ’ (5) Grandy, G. L., NSEC, unpublished data, 1957. (6) Grandy, G. L., Koch, R C., Rev. Sci. Instr. 31, 786 (1960). (7) Koch, R. C., Grandy, G. L., Sucleonics 18, No. 7,76 (1960). (8) Koch, R. C., Grandy, G. L., U. S. A4tomicEnergy Comm. Rept. NSEC-7 (1957). (9) Ibid., NSEC-12 (1958).
RECEIVED for review June 6, 1960. Accepted September 19, 1960. Work sponsored by U. S. Atomic Energy Commission under contract No. AT(30-1)1940 with the Babcock and Wilcox Co. These data are published by permission of both organizations.
Spectrophotometric Determination of Niobium and Molybdenum with 8-QuinoIinoI in Uranium-Base Alloys KENJI MOTOJIMA and HlROSHl HASHlTANl Division o f Chemistry, Japan Atomic Energy Research Institute, Ibaraki-ken, Japan
b A rapid and accurate spectrophotometric method for the determination of microgram quantities of niobium with 8-quinolinol can b e utilized for the analysis of uranium-niobium alloys containing 5% or less of niobium. The determination of niobium i s based on the extraction of its quinolinate with chloroform and spec48
ANALYTICAL CHEMISTRY
trophotometric measurement of the extract, Extraction of uranium is prevented by use of fluoride ion as a masking agent. This method can also b e used in the analysis of niobiummolybdenum-uranium ternary alloys containing up to 5% of additives; both niobium and molybdenum are determined readily.
T
HE preparation of many kinds of niobium-uranium alloys containing up to 1% niobium by the Metallurgy Research Group of the Japan Atomic Energy Research Institute necessitated a rapid and accurate analytical method for the determination of niobium. The conventional gravimetric methods (6-8, 11) for niobium tend to
