PRELIMINARY POWER TRANSIENT ANALYSIS OF THE SUPER FR WITH AXIALLY HETEROGENEOUS CORE

Tsutomu Okui,Akifumi Yamaji,M Margulis,P Blaise

doi:10.1051/epjconf/202124707002

Abstract

The Super FR is one of the SuperCritical Water cooled Reactor (SCWR) concepts with once-through direct cycle plant system. Recently, new design concept of axially heterogeneous core has been proposed, which consists of multiple layers of MOX and blanket fuels. To clarify the safety performance during power transient, safety analyses have been conducted for uncontrolled control rod (CR) withdrawal and CR ejection at full power. RELAP/SCDAPSIM code was used for the safety analysis. The results show that the peak cladding surface temperature (PCST) is high in the upper MOX fuel layer. It is also shown that axial temperature gradient of cladding greatly increases in a short period. Suppressing such large temperature gradient may be a design issue for the axially heterogeneous core from the viewpoint of ensuring fuel integrity.

Highlights

The Super FR is one of the SuperCritical Water cooled Reactor (SCWR) concepts with once-through direct cycle plant system [1][2]
The fuel assemblies are equipped with channel boxes and the coolant flow rate distribution to the fuel assemblies is determined with inlet orifices with consideration of reactivity buildup of blanket assemblies with burnup, so that the Maximum Cladding Surface Temperature (MCST) design criterion of 650 C is satisfied throughout the normal operation cycle [3]
The peak cladding surface temperature (PCST) of about 708 C is recorded in the upper Mixed OXide (MOX) fuel layer just after the reactor scram

Summary

Introduction

The Super FR is one of the SuperCritical Water cooled Reactor (SCWR) concepts with once-through direct cycle plant system [1][2]. The fuel assemblies are equipped with channel boxes and the coolant flow rate distribution to the fuel assemblies is determined with inlet orifices with consideration of reactivity buildup of blanket assemblies with burnup, so that the Maximum Cladding Surface Temperature (MCST) design criterion of 650 C is satisfied throughout the normal operation cycle [3]. For such design concept, abnormal transient and accident analyses have been carried out, which have indicated that loss of coolant flow and loss of coolant events tend to be more limiting scenarios compared with reactivity insertion or overpower events [5]

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Results

Conclusion