Prediction of Radioactive Corrosion Product Transfer in Primary Systems of Japanese Prototype Fast Breeder Reactor MONJU

Abstract

Radioactive corrosion products (CP) are main cause of personal radiation exposure during maintenance with no breached fuel in FBR plants. CP is produced in the core region by activation of fuel cladding and sub-assembly wrappers, and they are transported to the primary circuit with sodium flow and deposited on the wall of the primary piping and components. In order to establish the techniques of radiation dose reduction for of personnel, program system for corrosion hazard evaluation code “PSYCHE” has been was developed. The PSYCHE code is based on the solution-precipitation model. The density of each deposited CP and dose rate of primary coolant system in MONJU was estimated by using the PSYCHE and QAD-CG code. From the calculation for MONJU, it was predicted that deposition inventory of 54Mn would be about ten times more than that of 60Co in 20 years. In particularly deposition density; 54Mn would deposit mainly in the primary pump and cold-leg. On the contrary, 60Co depositions to not only the primary pump but also the Hot-leg. In the result, the future values of dose rate around primary piping system were estimated to be saturated at 2∼3 mSv/h. The calculation result of CP suggests that the analysis code and model make it possible to differentiate behavior of these nuclear species, definitely. Using the analysis code, the prospects for the future operations of MONJU could be established. Moreover, it is necessary to examination of improvement that the innovative calculation procedure and physics model, for applied to next generation LMFBR such as JSFR.