Analysis of the IRIS pressurizer behavior in the presence of noncondensable gases using RELAP5 computer code

Insurge and outsurge phenomena are transient states and could be analyzed by thermodynamics principles, the pressurizer behavior will vary in response to mass flow changes. These surges can occur in the presence of noncondensable gases. On this paper, with the code RELAP5, the IRIS reactor pressurizer is described to analyze surges phenomena in their control volumes with non-condensable gases since they modify the pressure response. A set of three pipes components represents the pressurizer regions, connected with each other by single junctions components, the bottom volume control is connected to the primary circuit, represented by a time dependent volume component, through a time dependent junction component, which describes the mass flow behavior during surges through surge orifices. The hydrodynamic components representing the pressurizer are surrounded by heat structures, in addition there are heat structures inside the bottom volume control describing the behavior of electrical heaters, that operate in cases of outsurges. The analysis are intended to detail the behavior variables as pressure, temperature and volume of liquid inside the pressurizer during a water surge coming from the primary circuit or a water surge coming from the pressurizer to the primary circuit. (author)