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The branching ratio of 131I
2614
Notes
and xSiO2 + xThO2 = x ThSiO4.
Physics Laboratory Patna University Patna-5, India
DEVENDRA PRASAD SINHA
Radioassay Laboratory University of Illinois Medical Center Chicago Illinois 60612
R A M E S H W A R PRASAD*
*To whom all correspondence should be addressed.
J. inorg, nucl. Chem., 1973, Vol. 35, pp. 2614-2615.
Pergamon Press.
Printed in Great Britain
The branching ratio of ~a~l (Received 6 November 1972) THE B~NCmNG ratio of 131Iis given in the literature as about 0.6 per cent [ 1]. Recent experiments in our laboratory have suggested very strongly that the true value is about 1-0 per cent. A number of samples containing mixed fission products were analyzed by gamma spectrometry with a Ge(Li) crystal coupled to a 2048-channel pulse height analyzer. The system was calibrated with 235UO2 irradiated with thermal neutrons that was analyzed radiochemically for several fission products having a range of gamma energies from about 0-1 to 2 Mev. Thus, the 13q content was determined to better than - 10 per cent. Table 1. Atoms of 13 l-chain by gamma spectroscopy and gas analysis of samples of mixed fission products Atoms of 13 l-chain at To* as determined from 13xlt lalmxe * 1.04 × 9-23 × 2.10x 1.34 x 4"76 × 1"04 ×
109 10s 10H 10TM 1011 10TM
1.09 x 10r 8-16 × 10° 2.17X 10° 2"09 × 101° 5"71 X 109 1"37 X 101°
131mXe/13q§ 0.0105 0.0088 0.0103 0'0156 0"0120 0"0132 ave. 0.0117---+0-0011
*Time of formation of the fission products. ?By gamma spectrometry. ~:By gas analysis. §Branching ratio for 131I. 1. C. M. Lederer, J. M. Hollander and I. Perlman, Table of Isotopes, 6th Edn, p. 277. John Wiley, New York (1967).
Notes
2615
After gamma pulse height analysis the samples were allowed to cool for about two to three weeks in order to effect almost complete decay of the 22-hr '331. Subsequently the samples were fused in a mixture of KOH and K2COO, with helium slowly bubbling through the melt in order to remove all ':"mXe and "~EKethat had been formed by the decay of the iodine isotopes. This procedure was shown to cause no or only insignificant loss of iodine. After solidification, '3'mXe was allowed to grow in again for about two to three weeks, after which a second fusion was conducted, with helium bubbling through the melt followed by a known amount of inert xenon carrier. After separation and purification the '3'mXe-activity was collected in a specially constructed gas counting cell and counted in a methane end-window beta counter. The counting efficiency was determined by cross-calibration with another laboratory where the counter-efficiencies were known. All experimental results were back-calculated to To, the time of formation of the fission products. The half-lives used were 8.04 days for '3'1, and 12.0 days for '3'mXe. The results are shown in Table 1. Note that the numbers in the '3'mXe column were not corrected for the branching ratio of '3'I. This ratio is calculated as the ratio of the '3'mXe column to the '3'I column, and is shown in the last column of Table 1. The average value is 0.012--*_0.001. A more accurate value of the branching is being determined by Momyer and Smith [2]. Our findings are in agreement with his preliminary data.
Acknowledgement-Part of this work was performed under Advanced Research Project Agency. Order No. 1970.
Trapelo Division LFE Corporation 2030 Wright A venue Richmond, California 94804 2. F. Momyer and C. Smith, (UCLLL) Private communication.
P. A. BENSON
H. Y. GEE M. W. N A T H A N S
Notes
and xSiO2 + xThO2 = x ThSiO4.
Physics Laboratory Patna University Patna-5, India
DEVENDRA PRASAD SINHA
Radioassay Laboratory University of Illinois Medical Center Chicago Illinois 60612
R A M E S H W A R PRASAD*
*To whom all correspondence should be addressed.
J. inorg, nucl. Chem., 1973, Vol. 35, pp. 2614-2615.
Pergamon Press.
Printed in Great Britain
The branching ratio of ~a~l (Received 6 November 1972) THE B~NCmNG ratio of 131Iis given in the literature as about 0.6 per cent [ 1]. Recent experiments in our laboratory have suggested very strongly that the true value is about 1-0 per cent. A number of samples containing mixed fission products were analyzed by gamma spectrometry with a Ge(Li) crystal coupled to a 2048-channel pulse height analyzer. The system was calibrated with 235UO2 irradiated with thermal neutrons that was analyzed radiochemically for several fission products having a range of gamma energies from about 0-1 to 2 Mev. Thus, the 13q content was determined to better than - 10 per cent. Table 1. Atoms of 13 l-chain by gamma spectroscopy and gas analysis of samples of mixed fission products Atoms of 13 l-chain at To* as determined from 13xlt lalmxe * 1.04 × 9-23 × 2.10x 1.34 x 4"76 × 1"04 ×
109 10s 10H 10TM 1011 10TM
1.09 x 10r 8-16 × 10° 2.17X 10° 2"09 × 101° 5"71 X 109 1"37 X 101°
131mXe/13q§ 0.0105 0.0088 0.0103 0'0156 0"0120 0"0132 ave. 0.0117---+0-0011
*Time of formation of the fission products. ?By gamma spectrometry. ~:By gas analysis. §Branching ratio for 131I. 1. C. M. Lederer, J. M. Hollander and I. Perlman, Table of Isotopes, 6th Edn, p. 277. John Wiley, New York (1967).
Notes
2615
After gamma pulse height analysis the samples were allowed to cool for about two to three weeks in order to effect almost complete decay of the 22-hr '331. Subsequently the samples were fused in a mixture of KOH and K2COO, with helium slowly bubbling through the melt in order to remove all ':"mXe and "~EKethat had been formed by the decay of the iodine isotopes. This procedure was shown to cause no or only insignificant loss of iodine. After solidification, '3'mXe was allowed to grow in again for about two to three weeks, after which a second fusion was conducted, with helium bubbling through the melt followed by a known amount of inert xenon carrier. After separation and purification the '3'mXe-activity was collected in a specially constructed gas counting cell and counted in a methane end-window beta counter. The counting efficiency was determined by cross-calibration with another laboratory where the counter-efficiencies were known. All experimental results were back-calculated to To, the time of formation of the fission products. The half-lives used were 8.04 days for '3'1, and 12.0 days for '3'mXe. The results are shown in Table 1. Note that the numbers in the '3'mXe column were not corrected for the branching ratio of '3'I. This ratio is calculated as the ratio of the '3'mXe column to the '3'I column, and is shown in the last column of Table 1. The average value is 0.012--*_0.001. A more accurate value of the branching is being determined by Momyer and Smith [2]. Our findings are in agreement with his preliminary data.
Acknowledgement-Part of this work was performed under Advanced Research Project Agency. Order No. 1970.
Trapelo Division LFE Corporation 2030 Wright A venue Richmond, California 94804 2. F. Momyer and C. Smith, (UCLLL) Private communication.
P. A. BENSON
H. Y. GEE M. W. N A T H A N S