Studies of passive safety tests by using the experimental fast reactor Joyo - Verification of Joyo plant dynamics analysis code Mimir-N2

摘要

Studies for passive safety tests to be conducted using the experimental fast reactor Joyo have been carried out to demonstrate the inherent safety of liquid metal fast breeder reactors (LMFBR). In these studies, emphasis has been placed on the improvement of the calculation accuracy of the feedback reactivity. Therefore, in the passive safety tests, the feedback reactivity measurement is planned under the condition simulating the anticipated transient without scram (ATWS) event. The Mimir-N2 analysis code, which has been developed to analyze Joyo plant dynamics, is used for predicting plant behavior during transients. In order to determine the passive safety test plan, the improvement of the accuracy of Mimir-N2 was required. In this study, transient tests including manual reactor shutdown (MRS) test, loss of power supply (LOPS) test and preliminary transient over power (p-TOP) test were conducted to verify the improved calculation model of the Joyo MK-III core and the heat transport system of Mimir-N2. As a result, good agreement was obtained between calculated and measured sodium temperatures. These results provided valuable insight for further improvements and verifications for predictions to plan the passive safety tests.