Development of evaluation methods for the transfer behavior of corrosion product in the primary cooling system of fast breeder reactor

Radioactive corrosion products (CPs) are a main cause of personal radiation exposure during maintenance with no breached fuel in sodium-cooled fast breeder reactor (FBR) plants. In order to establish techniques of radiation dose estimation for workers in radiation-controlled areas of the fast breeder reactor, the PSYCHE (Program SYstem for Corrosion Hazard Evaluation) code was developed. For the inspection of the analysis model using PSYCHE code, we surveyed past reports on CP deposits in Japan Experimental Fast Reactor JOYO and sodium test loops. The SEM images of the external surface of the irradiated fuel cladding in JOYO show surface deposition of particles containing significant volumes of CP species. The CP particle deposition model (Particle model) was developed from the phenomenological considerations of the observation results for JOYO. We add the Particle model to the conventional PSYCHE analytical model. Moreover, the conventional PSYCHE code does not consider the sodium flow of the coolant. The non-consideration of the sodium flow is a cause of reduction in calculation precision. To counter this problem we built the system that PSYCHE code linked NETFLOW++ code. This code is the one-dimensional network code which can simulate the plant transients of various types of nuclear reactors. In this study, we performed calculations of CP transfer behavior in JOYO using an improved PSYCHE code. The calculation results are consistent with the measured results for actual components in JOYO. The C/E (Calculated / Experimentally observed) value was improved by introduction of the Particle model and considered of the sodium flow.Copyright © 2012 by ASME