Measurement of nuclear reaction cross sections of rare earth nuclides-III

not registered

When minor actinides (MA) are returned to a core of fast breeder reactor for tbe purpose of incineration of them, rare earth nuclides and so on (RE) are also returned to the core because the separation of MA from RE is difficult at present. Then, accurate neutron cross section data of RE become necessary for investigating the characteristics of the core. Therefore, the measurement of keV-neutron capture cross sections of Nd and Nd were performed to obtain tbe accurate data. The measurement was relative to the standard capture cross sections of Au. A neutron time-of-flight method was adopted witb a ns-pulsed neutron source by a Pelletron accelerator and a large anti-Compton Nal(T1) gamma-ray detector. As a result, the capture cross sections of those nuclides were obtained with the error of about 4 % in an incident neutron energy region of 10 to 560 keV. A comparison between the present data and the evaluated values of JENDL-3.2 showed tbat JENDL-3.2 provided good evaluations for Nd, but underestimated the capture cross sections of Nd by 10-20 % at neutron energies below 30 keV and overestimated them by about 20 % at 560 keV, whereas it provided good evaluations in the energy region of 40-70 keV. The discrepancy is caused by the weak dependency of evaluated cross sections on the incident neutron energy.