Development of a phenomena identification and ranking table for a postulated double-ended guillotine break in a production reactor

In the wake of the Chernobyl accident, production reactors in the United States have come under increasing scrutiny with respect to safe operation. Because of additional design features, the U.S. reactors are considered inherently more safe than was the Chernobyl design. However, demonstration of their safety margins is required. The U.S. Nuclear Regulatory Commission has developed a generic methodology (code scaling, applicability, and uncertainty (CSAU)) to quantify the uncertainty in computer codes used to license commercial light water reactors. At the process level, the method is generic to any application that relies on computer code simulations to determine safe operating margins. The CSAU is being applied to a postulated double-ended guillotine break (DEGB) in a U.S. Department of Energy production reactor. The first three steps of the method, producing phenomena identification and ranking tables (PIRTs), have been completed to identify phenomena that are important to the postulated accident. The selected scenario is the hypothesized, but limiting, DEGB in the Savannah River site L reactor.