Simulation of Aerosol Removal from the Atmosphere of an NPP Containment using a Sprinkler System

Abstract

In the course of accidents at a nuclear power plant (NPP) beyond the design basis, radioactive fission products enter the atmosphere of the containment shell and then are released into the environment through leaks and the ventilation system. The release of radioactive substances is one of the key factors that determine the radiation consequences of an accident and, as a consequence, the safety of a nuclear power plant. Within the framework of the concept of managing beyond design basis accidents at NPPs with a pressurized water reactor (VVER), a sprinkler system is one of the safety systems used, among other things, to mitigate the consequences of beyond design basis accidents when radioactive fission products (FP) are released. The main functions of the sprinkler system are to reduce the pressure of the environment in the accident localization zone and remove heat from it and to reduce the concentration of radioactive substances (iodine in molecular and organic forms and aerosol particles) in the premises of the accident localization zone. Thus, the description of the process of removing radioactive fission products from the atmosphere of the containment shell of a nuclear power plant becomes an important task in the numerical modeling of beyond design basis accidents. This paper presents models of the main mechanisms for removing aerosol particles from the atmosphere of the containment by water droplets of a sprinkler system as well as the results of validation of these models in the TOSQAN and CSE experiments using the IRKA and MAVR-TA codes developed at the Kurchatov Institute.