Comparison of RELAP4 predictions with standard problems 1, 2, and 3

The report contains the results of RELAP4 best estimate calculations of Standard Problems 1, 2, and 3 including comparisons with experimental data. These analyses were performed to assess the capability and to identify areas of the RELAP4 code that need further improvement. RELAP4 is a digital computer program developed to predict the thermal-hydraulic behavior of experimental systems and water-cooled nuclear reactors subjected to postulated transients. Standard Problem 1 was based on the straight pipe depressurization experiments performed by Edwards et al. in Great Britain. Standard Problems 2 and 3 were based on an isothermal blowdown of the 1-1/2 Loop Semiscale System, Test 1011 and 1009, respectively. The semiscale apparatus is a scaled experimental system which is intended to simulate the thermal-hydraulic phenomena occurring in a pressurized water reactor (PWR) primary system during a loss-of-coolant accident (LOCA). Standard Problems 2 and 3 were similar isothermal blowdown esperiments except an Emergency Core Coolant (ECC) Injection System was added to the latter