Abstract
237Np oxide targets irradiated in the experimental fast reactor JOYO were analyzed by applying sophisticated radiochemical technique. Pu and Np were isolated from the irradiated targets by anion exchange chromatography. Total fission events of each target were estimated by 137Cs method. 237Np and 236Pu were determined by alpha spectrometry. The isotopic ratio of Pu and the content of Pu were determined by thermal ionization mass spectroscopy and isotope dilution mass spectrometry, respectively. From these analytical results, the transmutation behavior of 237Np in a fast reactor was discussed. Up to about 528 EFPD (Effective Full Power Days) irradiation, the transformation through capture reaction was much larger than the incineration through fission reaction, although the latter increased comparatively in case of irradiation in hard neutron spectrum. 236Pu was clearly observed in all irradiated 237Np samples but its quantity was much smaller than the estimated value on the basis of present nuclear data library.
