Evaluation of RELAP5 models and improvement of interphase transfer terms related to ALWR applications
Abstract
The first part of the thesis describes a method for using RELAP5 models to corroborate the scaling methodology that has been used for design of the Purdue University Multidimensional Test Apparatus (PUMA). This facility was built for the U.S. NRC to obtain data on the performance of the passive safety systems of advanced light water reactor concepts such as the experimental boiling water reactor (XBWR). The RELAP5 models are developed for the prototype system, the ideal scaled system, and the actual PUMA facility. Similarity is investigated between these models for a main steam line break accident. The second part of the thesis concerns improvements to the RELAP5 code in wall friction and interface mass transfer modeling. Both of these models are very important to the accurate prediction of the physical processes that occur within the components of the experimental XBWR. Previous RELAP5 models for the annular flow regime unphysically attributed a large fraction of the wall friction to the gas phase, while in reality, the gas does not contact the wall at all. This caused the liquid velocity to be more than ten times larger than it should be. To improve the wall friction model, a new annular wall friction model was implemented that applies wall friction only to the liquid. The revised wall friction model for annular flow produces good agreement when compared to experiment data. The RELAP5 modeling of interphase mass transfer when noncondensable gases are present has been identified as a problem area. In the current RELAP5 code, interphase heat transfer is based on an interfacial temperature determined from bulk conditions. Physically, when noncondensables are present, the interfacial temperature is governed by the local interfacial conditions which differ from bulk conditions due to the mass diffusion process. In this thesis, a mass transfer model is developed in which the interfacial temperature and corresponding energy and mass transfer model are consistent with the RELAP5 numerical solution scheme. The new developed model is tested using a variety of conceptual problems and an experiment.
Degree
Ph.D.
Advisors
Ransom, Purdue University.
Subject Area
Nuclear physics
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