Analysis of Loss of Cooling in Spent Nuclear Fuel Pools

Abstract

This master thesis presents an improved estimate of the course of events in the loss of cooling of the spent fuel pools on Ringhals 3 and 4. Previous analyzes do not take heat losses from the water in the pools into account, leading to large conservatism, especially at lower residual heats as evaporation contributes to the removal of a significant portion of the residual heat. With less conservatism, these results can be used when doing priorities in catastrophic events that causes a loss of cooling in the spent fuel pools. The analysis in this report also shows that evaporation and a decreasing water level occur before boiling, which in the previous analysis was assumed to occur only when the water reaches 100 C. This result can be used to avoid erroneous assumptions about leaking spent fuel pools that could otherwise be assumed as the cause of a decreasing water level. In order to obtain these results Comsol Multiphysics has been used. Comsol is a multiphysics software that uses the finite element method to simulate physics. A big part of the work has been spent on exploring the possibilities with Comsol, which was a wish from Ringhals.