Assessment of TRAC-PF1/MOD1 and TRAC-PF1/MOD2 codes for thermal-hydraulic behavior in pressure vessel during reflood in SCTF test with an inclined radial power distribution

摘要

Post test calculations for the Slab Core Test Facility (SCTF) Test S3-15 which had an inclined radial power distribution were performed to assess the TRAC-PF1/MOD1 (MOD1) and the TRAC-PF1/MOD2 (MOD2) codes for the thermal-hydraulic behaviors including two-dimensional behaviors in pressure vessel during reflood phase of a PWR-LOCA. In this report, it was mainly assessed whether the predictability of the MOD2 code was improved compared to that of the MOD1 code or not. In the MOD2 code, the core thermal-hydraulic model during reflood and the numerical scheme for pressure vessel have been changed from those in the MOD1 code. The predictions by the MOD2 code was improved qualitatively for the hydraulic behaviors in pressure vessel although the characteristics of water accumulation in the upper plenum was different from measured results. The quantitative difference between the MOD2 code predictions and the data was large for the void fraction in the lower half of core. The predictability of the MOD2 code for the core heat transfer was degraded compared to that of the MOD1 code. Time step size in the MOD2 calculation was larger than that in the MOD1 calculation due to the change of numerical scheme for VESSEL component and the calculational speed in the MOD2 calculation was almost 1.5 times faster than that in the MOD1 calculation. (author). (ERA citation 19:008783)