HYDROGEN CATALYTIC RECOMBINER’S ENGINEERING MODEL FOR DYNAMIC FULL-SCALE CALCULATIONS

Abstract

In order to protect the hermetic enclosure and the equipment and systems of the reactor installation housed in it from damage caused by the ignition (explosion) of hydrogen, the overwhelming majority of nuclear power plants with pressurized water reactors are provided with a hydrogen concentration monitoring system and an emergency hydrogen removal system. These systems prevent the formation of explosive mixtures in the accident localization zone by maintaining the volume concentration of hydrogen in the mixture below the safety limits which ensures the preservation of the density and strength of the hermetic enclosure and the operability of other localizing security systems. A key component of the emergency hydrogen removal system is a passive autocatalytic hydrogen recombiner which operation is based on the principle of catalytic recombination of hydrogen and oxygen. There is an urgent need for a full-scale dynamic calculation of the development of emergency conditions in a nuclear power plant container accompanied by a large release of hydrogen. In order to achieve this goal, we have constructed and justified a simple engineering thermohydraulic model of hydrogen removal in the operation of the PAR based on the available experimental data. The paper presents the application results of the model as a part of contour industry codes: RELAP, TRACE, and CORSAR, intended, among other things, for carrying out multifactor and fullscale calculations of the dynamics of emergency processes with the release of hydrogen into the nuclear power plant premises. This model allows us to substantiate the dynamics of local concentrations of gas components of the mixture in a confined space, the temperature of the mixture, the catalyst and the walls of the box, the pressure when hydrogen or steam is supplied to the box. We have analyzed various rates of hydrogen supply to a closed box in order to numerically substantiate the time when the concentration reached the maximum level. Moreover, we have calculated the performance for several entrance concentrations of hydrogen, and obtained a satisfactory agreement between the dynamics of the concentrations, temperatures of the catalyst and gas, and the productivity of the passive autocatalytic hydrogen recombiner. These calculations are based on the results of the calculated and the available experimental data comparison.