Measurement and evaluation of leakage neutron spectrum at TRACY

The leakage neutron spectrum of the Transient Experiment Critical Facility (TRACY) at the Japan Atomic Energy Research Institute was measured. The experimental core is composed of 10wt% enriched uranyl nitrate solution in a 50 cm inner diameter cylindrical tank. As measuring methods, we used the recoil proton proportional counter method and the multi-foil activation method. In order to evaluation a spectrum, the former unfolding code is SPEC-4 and the latter is NEUPAC-JLOG. We had improved the NEUPAC-JLOG in order to use for the thermal reactor. In the case of measurement by the recoil proton proportional counter, it was performed under the stationary state operating condition. The evaluated neutron spectrum was in good agreement with the tendency of calculation using MCNP4B with JENDL3.2 library. For the multi-foil activation method, they were performed under the stationary state and the transient state operating conditions. The neutron spectrum as a guess spectrum was calculated using MCNP4B with JENDL3.2. The result of neutron spectrum analyzed by MCNP is reliable for the steady state. In case of the transient state, the unfolding spectrum of the fast neutron region was almost the same result as the initial spectrum. In the thermal neutron region, the unfolding spectrum was somewhat greater than the initial spectrum. This is considered to be caused by generation of void by the transient. (author)