TRAC analysis of the effect of increased ECC subcooling on the reflood transient in the Slab Core Test Facility

A blind posttest calculation of Slab Core Test Facility (SCTF) Run 510, the high-subcooling test, was completed with TRAC-PD2/MOD1 using initial conditions provided by the Japan Atomic Energy Research Institute (JAERI), but without knowledge of the actual test results. There is good comparison between the calculation and the data for rod temperatures, turnaround times, core differential pressures, and mass inventories, and reasonable comparison for absolute pressures, upper plenum pool formation, and fluid temperatures and mass accumulation in the steam-water separator. Comparison of this calculation with the calculation of the base case test (Run 507) shows that the qualitative behavior during reflood is calculated correctly for both cases. In addition, from this comparison the following conclusions can be drawn: for the high-subcooling case, the peak rod temperture was lower, calculated quench times were earlier, there was more entrainment and liquid carryover from the core to the upper plenum, and the liquid mass accumulation in both the core and the upper plenum was greater