Margin Analysis of MONJU Thermal Transient Based on Measured Plant Performance

This paper reports a part of realistic safety margin analysis of Japanese prototype fast breeder reactor MONJU, based on actually measured plant characteristics during a commissioning operation under up to 40% electric power generation mode. In order to evaluate realistic integrity margins against design-phase evaluations and against the limit values, the thermal stresses of critical component parts after a typical thermal transient event, i.e., a manual reactor trip, were derived through serially combined thermal transient and structural analyses. The results of thermal transient and structure analysis confirmed that the evaluation values of the structural stresses at the reactor vessel outlet nozzle, at the upper tube sheet of the intermediate heat exchanger, and at the evaporator feed water inlet tube sheet are well within the design evaluation values.