A sensitivity study supporting comparative analysis of MELCOR and GOTHIC large dry pressurized water reactor containment models
Conference Paper
Overview
Identity
Additional Document Info
View All
Overview
abstract
The thermal-hydraulic response of large dry pressurized water reactor (PWR) containments under loss-of coolant accident (LOCA) conditions - particularly with respect to containment pressure and sump pool temperature - is crucial for risk informed decision making about GSI-191. Texas A&M University (TAMU) has developed models with several computer codes including MELCOR and GOTHIC. MELCOR is a best-estimate thermal-hydraulics and severe accident code created and actively maintained by Sandia National Laboratories for the Nuclear Regulatory Commission (NRC). GOTHIC is a thermalhydraulics software package meant for design, licensing, and safety calculations for, among other systems, nuclear power plant containments. It was developed and is maintained by Numerical Applications Inc. (Zachry Nuclear Engineering, Inc.) for the Electronic Power Research Institute (EPRT). The overarching goal of this paper is to investigate differences in best estimate calculations of thermalhydraulic response to a double-end guillotine break (DEGB) LOCA for similar MELCOR and GOTHIC containment models. The code predictions themselves are presented in a separate paper wherein reasonable though unsupported conjectures about code disagreements are made. These hypotheses are examined here via a MELCOR-to-GOTHIC comparative sensitivity study because they stem from either code input restrictions (such as DEGB source mass/enthalpy definition) or code physics/equipment models (e.g. for condensation/films or various engineered safety features). Therefore the "sensitivity" in this context is that of the comparative thermal-hydraulic response to the code inputs or phenomenological models in question. Sensitivity calculations are performed so as to exclude, in turn, the effects on comparative thermal hydraulic response of: containment fan coolers, containment sprays, thermal surface condensation/films, and break source definition. Calculations are also performed with multiple models excluded. Using containment sump pool temperature as an indicator, the most impactful physics in terms of code agreement are those of thermal surfaces (condensation, film phenomena) whereas fan cooler models have a minimal effect. Containment spray exclusion has mixed effects while break source definition and/or break effluent flashing models lead to disagreement.
