Computer simulation of an accumulator discharge test performed during preoperational testing of the ECCS at the Trojan Nuclear Plant

The RELAP4 computer code was used to analyze a test performed on an actual power reactor with the as-built configuration forming the basis of the modeling. This test consisted of an accumulator discharge performance test, which was part of the functional checks of the ECCS conducted during preoperational testing at the Trojan Nuclear Plant. The test procedure specified that the accumulator was to discharge a normal charge of water at an initial pressure of 100 psig to the reactor vessel. During the test, the reactor vessel head and the upper and lower internals were removed. The system was first flushed and then these initial conditions were established. Blowdown was initiated by opening the motor-operated accumulator isolation valve in the 10-in. safety injection line. Precautions were taken to ensure that the discharged water did not interfere with the test or overflow the reactor vessel. The test was terminated by closing the isolation valve when the accumulator pressure reached 10 psig, as measured by a temporary gauge attached to the normal accumulator pressure measuring instrumentation