ANALYSES OF THE START-UP AND SHUT-DOWN OF SCWR FUEL QUALIFICATION TEST LOOP

In the development of the Super Critical Water Reactor (SCWR), it is planned to carry out a fuel qualification test (FQT) on a small scale fuel assembly in the research reactor LVR-15 located in Research Center Rez (CZ). The subject of the SCWR-FQT project is to design and license a facility containing the small scale fuel assembly comprised of 4 fuel pins with wire wraps, including the required loop with its safety and auxiliary systems. The present paper focuses on the transient analyses for start-up and shut-down of the FQT loop, particularly to explore the ability of system codes ATHLET 3.0A to simulate the transient between subcritical conditions and supercritical conditions. Simulations of heating up of the SCWR-FQT loop and achieving nominal supercritical conditions (Tiio=390 degrees C and Pio=25 MPa for primary circuit) were carried out. Further, analyses of shut-down of the SCWR-FQT loop from its supercritical conditions by shutting down the reactor and cooling down the loop until subcritical conditions were performed. Particular attention was dedicated for the models of heat transfer in supercritical condition.