Neutron spectra measurements at JAEA MOX fuel facility

Tsujimura, Norio   ; Yoshida, Tadayoshi ; Sagawa, Naoki; Shoji, Shigeru

The Nuclear Fuel Cycle Engineering Laboratories (NCL) of the Japan Atomic Energy Agency fabricates MOX fuels for FBRs Monju and Joyo in the Plutonium Fuel Production Facility (PFPF). The MOX pellet contains plutonium of 20-30w%; therefore neutron exposures to workers in the fabrication process are of concern for radiation protection. For a good knowledge on spectra, during the second reload-fuel production campaign for the Joyo reactor, neutron spectrum measurements were made at 20 locations representative of the PFPF using the Bonner multisphere spectrometer. The unfolding code SAND-II was used to determine the neutron spectrum from each set of count data. The unfolded results show that the range of average neutron energies for all locations is from 0.35 to 1.6 MeV; spectrum-averaged fluence-to-ambient dose equivalent conversion coefficients 100 to 340 pSv cm.