Hiroshi Okashita

Non-Destructive Gamma-Ray Spectrometry on Spent Fuels of a Boiling Water Reactor

The spent fuels from the JPDR-I reactor were measured by means of a γ-scanning facility installed in the fuel storage pool. The spatial distributions of the fission products (134Cs and 137Cs) were measured and analyzed in reference to the effects of control rod pattern. The ratios holding between the products of neutron capture and of direct fission (134Cs/137Cs and 154Eu/137Cs) were also examined for its relevance to non-destructive burnup determination. The activity ratios of the fission products can be expressed by a linear function of burnup, provided that corrections are made to account for differences in irradiation history and for spatial variations in the neutron spectrum.

Fast Computer Analysis of the γ Spectrum from Ge(Li) Detectors

A method for rapidly analyzing the γ spectrum obtained with Ge(Li) detectors was developed for a medium-size electronic computer. The analysis is based on the first derivative method, associated with a number of peak-shape tests. The effects of data smoothing and of changes in peak width were studied to determine the optimum conditions for spectrum analysis. The resulting computer program was subjected to various quality tests on the predicted values of the peak position and area. The results of the tests showed that the code thus developed works quite satisfactorily. The code requires 10 sec and a memory core of 29 k when using a FACOM 230–60 for the analysis of a 2,047 channel spectrum.

Synthesis of Transuranium Nuclides from Interaction of 160 with 238U

Many studies of actinides, especially of transuranium elements, have been performed mainly owing to scientists’ endeavors to discover new elements and nuclides. (1) In spite of these efforts, the mechanism of the formation of transuranium nuclides by heavy-ion bombardment and the nuclear and chemical properties of the synthesized actinide nuclides have not been clearly elucidated, and a great deal remains to be examined in more detail. In this context, we have begun the investigation of heavy-ion nuclear reactions(2): A system in which a uranium target is irradiated by oxygen ions (160 + 238U), was chosen. For this reaction seventeen nuclides (250Fm) 244,245,248Cf, 242Cm, 233,239Np) 237,239U 225,226,227,228Th, 224,225Ac, and 223,224Ra) were identified and the condition of formation for these nuclides was clarified. This paper deals with a novel method of mutual rapid separation of the synthesized transuranium elements by ion exchange and a discussion of the mechanism which governs the heavy-ion nuclear reactions.