Study on neutron capture cross sections of long-lived fission products

Igashira, Masayuki*; Osaki, Toshiro*; Nagai, Yasuki*; Yamana, Hajimu*; Fujii, Toshiyuki*; Takamiya, Koichi*; Harada, Hideo   ; Furutaka, Kazuyoshi  ; Nakamura, Shoji  

Accurate fast-neutron capture cross sections of long-lived fission products (LLFPs) are indispensable for the R&D of nuclear transmutation systems which utilize the fast-neutron capture reaction. The accuracy of those cross section data contained nuclear data libraries are, however, quite inadequate. Therefore, accurate experimental data on those cross sections are necessary as the basic data usefule for the evaluation of capture cross sections of LLFPs. The final goal of the present study is to obtain the results with the errors from 5 to 10% fore the fast-neutron capture cross sections of Tc and tentative results with the errors of about 10% for those of Zr, using the electron linear accelerator based neutron source at the Oak Ridege National Laboratory. For this goal, the four research items were executed: (1) the separation, purification and analysis of LLFP samples, (2) the improvement of weighting function of -ray detector, (3) the measurement of fast-neutron capture cross sections of impurity isotopes in LLFP samples, and (4) the measurement of fast-neutron capture cross sections of Tc and Zr. The final goal was not reached due to the long-term trouble of the electron linear accelerator, but sufficient results were obtained for the other items. In particular, the present results for the capture cross sections and capture -ray spectra of Zr wer important nuclear data for the R&D of nuclear transmutation systems.