Measurement of the Thermal Neutron Cross Section of the 90Sr(n,.GAMMA.)91Sr Reaction.

概要

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To obtain fundamental data for the research of the transmutation of nuclear waste, the thermal neutron cross section of the reaction 90Sr(n, γ)91Sr has been measured by means of a radiochemical method. Strontium chloride targets containing about 2 MBq of 90Sr were irradiated for 10min with reactor neutrons. Activation detectors of Co/Al and Au/A1 alloy wires were irradiated simultaneously to monitor the neutron flux and Westcott's epithermal index r(T/T0)1/2.The irradiated Sr samples were purified chemically and their γ-ray spectra were measured with a high purity Ge detector. Since the targets included 85Sr, a γ-ray emitter and a tracer for 90Sr, and a ratio of the amount of 85Sr to that of 90Sr was measured in advance, an effective cross section of the 90Sr(n, γ)91Sr reaction for a reactor neutron spectrum was determined from the ratio of radioactivities of 91Sr and 85Sr, and neutron flux data. The resonance integral was also measured by a modified Cd-ratio measurement. Considering an upper limit of the resonance integral to be 0.16b, the thermal neutron cross section (2, 200 m/s neutron cross section) of 90Sr(n, γ)91Sr reaction was found to be 0.0153±0.00130.0042 b. The value obtained is only 1/50 of the value reported by Zeisel (1966), and is in good agreement with the figure reported by McVey et al. (1983).
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