Improved pressurized water reactor steamline break analysis using RETRAN-02, ARROTTA, and VIPRE-02

The steamline break accident is one of several specified severe transients addressed in the final safety analysis report for any pressurized water reactor plant as part of the licensing procedure. A rupture in a main steamline in the secondary system causes a sudden cooling of the water in the corresponding primary loop. The cold water flowing into part of the core represents a positive reactivity insertion that must be contained by control rods, which are scrammed into the core almost immediately. Later in the scenario, soluble boron reaches the core from the emergency core cooling system. When simulating a steamline break accident during the licensing procedure, many conservative assumptions are added to the transient description. Historically, a steamline break analysis is performed with a system analysis code like RETRAN, using a rather simplified (point kinetics) description of the core. The three-dimensionality of the event within the core is accounted for by constant blending factors, which are used to calculate the evolving point kinetics parameters based on a simplistic cold and hot partition of the core. In this paper the ARROTTA-01 and VIPRE-02 computer codes are coupled to allow a detailed three-dimensional simulation of the reactor core during a steamline break event