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Instrumental neutron activation analysis in the determination of the $sup 235$U/$sup 238$U isotopic ratios for samples from 0.4 to 93% $sup 235$U

Book ·
OSTI ID:4345944
A simple neutron activation method for the determination of the /sup 235/ U/sup 238/U isotopic ratios using a high-resolution Ge(Li) detector for gamma detection is reported. The /sup 235/U//sup 238/U ratios are determined from the activity ratios of /sup 143/Ce//sup 239/Np. The 293- and 278keV gamma rays from / sup 143/Ce and /sup 239/Np, respectively, were chosen for their activity measurements. With well thermalized neutrons the isotopic ratios can be determined for samples with /sup 235/U contents from 0.4 to about 30%. The accuracy is about 2 to 3% for samples with /sup 235/U contents below about 10%. With increasing /sup 235/U contents the accuracy decreases because the relative intensity of the 278-keV gamma ray of /sup 239/Np becomes too weak to be determined accurately. For samples of high /sup 235/U content, epithermal neutrons must be used in the activation to enhance the relative production rate of /sup 239/Np with respect to that of fission products. The epithermal neutrons are obtained by means of cadmium filters. With samples well shielded by cadmium filters, i.e. inside a closed cadmium case, the enhancement of the relative production rate of /sup 239/Np to that of /sup 143/Ce is found to be about 80 fold compared with the activation of well thermalized neutrons. (GE)
Research Organization:
Inst. of Nuclear Energy Research, Taipei, Taiwan
NSA Number:
NSA-29-015238
OSTI ID:
4345944
Country of Publication:
Germany
Language:
English