Loss-of-load transient calculations for the ROSA-IV LSTF and the reference PWR with RELAP5/MOD1(Cycle 1)

The response of LSTF and the reference PWR to two loss-of-load transients was analyzed with the RELAP5/MOD1, Cycle 1, computer program. The transients analyzed included a loss-of-load only (base case) and a loss-of-load without scram. These calculations were the first attempt to analyze the response of LSTF to a loss-of-load transient and, therefore, are not a final assessment of the system's capability to represent the PWR response. Comparison of the results showed that LSTF has the capability to simulate the basic PWR response to a loss-of-load. For both transients calculated, the final state of LSTF and the PWR were the same, in that the primary systems had stabilized and were maintained in that condition by the same type of secondary system operation. Because of differences in initial core power and primary flow rate, however, the details of the thermal-hydraulic response (such as the system pressure and temperature) were different. Further study and analysis of the problem areas are recommended in order to find ways to improve the LSTF response relative to the PWR. (author)