CONTEMPT-4MOD3, LWR Containment Long-Term Pressure Distribution and Temperature Distribution in LOCA

1 - Description of problem or function: CONTEMPT-4/MOD5 describes the response of multi-compartment containment systems subjected to postulated loss-of-coolant accident (LOCA) conditions. The program can accommodate both pressurized water reactor (PWR) and boiling water reactor (BWR) containment systems. Also, both design basis accident (DBA) and degraded core type LOCA conditions can be analyzed. The program calculates the time variation of compartment pressures, temperatures, and mass and energy inventories due to inter-compartment mass and energy exchange taking into account user- supplied descriptions of compartments, inter-compartment junction flow areas, LOCA source terms, and user-selected problem features. Analytical models available to describe containment systems include models for containment fans and pumps, cooling sprays, heat conducting structures, sump drains, PWR ice condensers, and BWR pressure suppression systems. To accommodate degraded core type accidents, analytical models for hydrogen combustion within compartments and energy transfer due to gas radiation are also provided. CONTEMPT4/MOD6 is an update of previous CONTEMPT4 versions. Improvements in CONTEMPT4/MOD6 over CONTEMPT4/MOD3 include coding of a BWR pressure suppression system model, a hydrogen/carbon monoxide burn model, a gas radiation heat transfer model, a user specified variable junction (leakage) area as a function of pressure or time, additional heat transfer coefficient options for heat structures, generalized initial compartment conditions for inerted containment, an alternative containment spray model and spray carry-over capability. Also, the thermodynamic properties routines have been extended to accommodate the higher temperature and multicomponent gas mixtures associated with combustion. In addition, reduced running time is achieved by incorporation of an optional implicit numerical algorithm for junction flow. This makes economically feasible the analysis of very long term transients such as are encountered during degraded core accidents with hydrogen combustion. The user has the option of turning off the implicit routine through user input, if desired. 2 - Method of solution: Containment thermodynamic conditions of hydrogen/air/steam/liquid water mixtures are determined by using modularized equation-of-state subroutines and tabulated water properties. The numeric in the code are completely explicit except for the predictor-corrector technique used to estimate the heat structure effects on compartment conditions, an implicit calculation of junction flow with inertia, and an optional implicit routine for junction flow calculation approaching pressure equilibrium. 3 - Restrictions on the complexity of the problem: Maxima of: 999 lumped parameter compartments, 99 heat conducting structures using a variety of heat transfer options and boundary conditions. Inter-compartment flow junctions may be calculated for either a sharp-edge orifice (single phase homogeneous or two-phase flow) or a nozzle (vapor flow only). Containment cooling spray analytical models are provided for either single or double heat exchangers