TRACE Analysis of the MASLWR Primary/Containment Coupling Phenomena in Beyond Design Accident Scenario

Today the use of small modular integral reactors is one of the options for the use of the nuclear technology in a sustainable energy mix in developing and developed countries. These new designs are relatively portable and well suited for deployment on small electricity grids. Small Modular Reactors (SMR) provide parallel construction capabilities that reduce capital costs, construction times, and finance and costs. They are recognized to be able to reach larger electricity market around the world. In this framework the Multi-Application Small Light-Water Reactor (MASLWR) is a small modular integral Pressurized light Water Reactor (PWR) of 35 MWe relying on natural circulation during both steady-state and transient operation. The integral arrangement of the plant avoids pressurized primary components outside the Reactor Pressure Vessel (RPV) eliminating the possibility of a large break Loss of Coolant Accident (LOCA) and reducing the Small Break LOCA (SBLOCA) initiating event frequency. Of particular interest is the SBLOCA mitigation strategy typical of the MASLWR design based on a natural circulation dynamic coupling between the primary and the containment system. A first test campaign, under a US Department of Energy grant, has been conducted in an experimental test facility constructed at Oregon State University (OSU-MASLWR) to test the MASLWR prototype phenomena. In particular the OSU-MASLWR 003B test thermal hydraulically investigates the MASLWR dynamic primary/containment coupling during a beyond design basis accident scenario. The analyses of this test have been performed by using the TRACE code and shows that the TRACE code is able to predict the primary containment interactions typical of this design.