Influence analysis of coupled neutronics and thermal-hydraulics on characteristics of supercritical water-cooled reactor system

Coupled neutronics and thermal-hydraulics is one of the key issues of super critical water-cooled reactor system analysis. Taking the Super LWR concept proposed by Japan as example, the neutron cross-section library for supercritical water-cooled reactor was made by Dragon code, and then a two-group neutron diffusion calculation module was created. By combining with the thermal-hydraulic calculation module, the coupled neutronic and thermal-hydraulic calculation module of supercritical water-cooled reactor was finally obtained. By comparing the thermal-hydraulic behavior under the uncoupling calculation condition with that under the coupling calculation condition for both steady-state and transient analyses, thermal-hydraulic characteristics of supercritical water-cooled reactor under coupled neutronic and thermal-hydraulic condition was analyzed. The results show that, in steady-state case, the neutronic and thermal- hydraulic coupling will lead to the axial core power peak factor shifting along axial direction for both the inner and outer assemblies. It makes part of the cladding temperature rising but the maximum cladding temperature decreasing. In transient case, the neutronic and thermal-hydraulic coupling may cause the position changed of maximum cladding temperature. When the loss of feed-water heating occurs, the cladding temperature in the outer fuel assembly will become even higher than that in the inner fuel assembly at a certain time. Thus, the neutronic and thermal-hydraulic coupling has a significant impact on both the value and the location of the maximum cladding temperature. The calculation analysis can provide a theoretical reference for transient and safety analyses of supercritical water-cooled reactor. (authors)