Improvement of material dosimetry for irradiation test in JOYO

Ito, Chikara   ; Aoyama, Takafumi ; Masui, Tomohiko*; Saikawa, Takuya*

The material dosimetry using the multiple foil activation method has been carried out in order to assure the accuracy and reliability of neutron fluences for the irradiation tests in the experimental fast reactor "JOYO". In this study, the neutron fluences were calculated by the JOYO core management code system "MAGI" for the subassemblies which were irradiated at the positions around control rods or reflector boundary in the JOYO Mk-II core. Improvement of neutron fluence was evaluated when the "MAGI" calculation was corrected with the dosimetry results. The difference of the neutron spectrum adjustment was also investigated between ENDF/B-V and JENDL-3 dosimetry files. The major results obtained are summarized as follows; (1)The reaction rates of the dosimeters calculated by the adjusted neutron spectrum agreed well with the measured values, and its error was reduced. (2)The neutron spectrum adjusted using JENDL-3 dosimetry file was significantly improved than that by ENDF/B-V in the energy range of 10100 keV, because of the less error of the neutron capture cross sections of Co and Sc. (3)It showed that the correction rate of the "MAGI" calculation by the dosimetry results ranged 1030% for the subassemblies of the JOYO irradiation test.