Measurement of Thermal Neutron Cross Section and Resonance Integral of the Reaction 135Cs(n, .GAMMA.)136Cs.

Abstract

The thermal neutron (2,200 m/s neutron) capture cross section (σ0) and the resonance integral (I 0) of the reaction 135Cs(n, γ)136Cs were measured by means of an activation method to obtain fundamental data for research on the transmutation of nuclear waste. Targets of radioactive cesium, which include 135Cs and 137Cs as well as stable 133Cs, were irradiated with reactor neutrons within or without a Cd shield case. The Co/Al and Au/Al alloy wires as activation detectors were irradiated together with cesium samples to monitor the neutron flux and the fraction of the epithermal part (Westcott's index). A high purity Ge detector was used for the γ-ray measurements. The 137Cs nuclide was used as a tracer of 135Cs, since 135Cs decays through β-transition, but does not emit γ-rays. The ratio of the number of nuclei of 135Cs to that of 137Cs in the target was measured with a quadrupole mass spectrometer. This ratio and the ratio of activity of 136Cs to that of 137Cs in the irradiated target were used for deducti...