Thermohydraulic Modelling of Flooding and Steam Dispersion in the Reactor Building of Forsmark 2.

Sammanfattning

Nuclear power is a foundational part of our electrical grid in the present and through our transition towards more sustainable and renewable alternatives. However, given the serious consequences of reckless and/or dangerous operation of nuclear power plants, they are subject to strict regulation and supervision by the Swedish radiation protection authority (SSM) and other regulating bodies (e.g. IAEA). In order to prove that a nuclear power plant is operating in a safe and accident preventative manner, the “Safety Analysis Report” (SAR) is created and submitted. The SAR categorizes and ranks all possible incidents and operation affecting events in terms of risk and available countermeasures to ensure that the radioactive release from the power plant and impact on a third party from any event is at acceptable levels. This projects limits its analysis to flooding of the reactor building or “internal flooding events” as described in the SAR. To determine the affected areas and impacted systems of any flooding event, deterministic safety analyses (DSA) are employed. The goal of this project is to develop a comprehensive thermohydraulic model of the Forsmark 2 reactor building and evaluate its performance with respect to the previously used MATLAB model. The model should allow for a detailed nodalisation of the reactor building as well as realistic modelling of structural components such as doors, hatches, stairwells and drainage systems. The resulting thermohydraulic model can be used to evaluate different flooding incidents dynamically and follow the spread of water and/or steam throughout the reactor building. Furthermore, the resulting pressure changes and heat generation in the reactor building can also be evaluated. The model allows for the possibility to couple the thermohydraulic reactor building model with the existing power plant systems model to holistically evaluate the power plant response to flooding related incidents.