Assessment of TRAC-PF1/MOD1 code for core thermal hydraulic behavior during reflood with CCTF and SCTF data.

摘要

Post test calculations for six selected Cylindrical Core Test Facility (CCTF) and Slab Core Test Facility (SCTF) tests were performed to assess the TRAC-PF1 code for core thermal hydraulic behaviors during the reflood in a PWR LOCA. It was found through comparisons of calculated results with measured results that predicted void fraction and core mass with the TRAC-PF1 code showed poor agreement with measured results in quantity and that the TRAC-PF1 code predicted well turnaround time, turnaround temperature and quench time in clad temperature transient including parameter effect of system pressure and core power level. In the calculation for the CCTF best-estimate test, which was performed with low initial clad temperature, the TRAC-PF1 code predicted higher core cooling rate and faster quench propagation than measured results. A study on the interfacial friction model and wall heat transfer model was performed to identify problem areas of the TRAC-PF1 code. It is recommended to improve following models of the TRAC-PF1 code for more realistic prediction of core thermal hydraulic behaviors during the reflood in a PWR LOCA; (1) Interfacial friction model in the bubbly/slug flow regime, (2) Interfacial friction model in the vicinity of the flow transition point from the churn flow to the annular/dispersed flow, (3) Wall heat transfer model in the film boiling regime, and (4) Wall heat transfer model on the criteria for the boiling transition from the film boiling to the transition boiling at low initial clad temperature. (author). (ERA citation 18:026153)