Publikationsserver der RWTH Aachen University
Sicherheitsanalyse zur Auslegung eines Core-Catchers für einen heliumgekühlten schnellen Brüter
Abstract
dc:descriptionA case has been considered in which the core of a 875 MWth. helium cooled fast breeder reactor is totally molten-down in a hypothetical severe accident. A “core catcher concept” with a sacrificial steel-bed is suggested which should encapsulate the core melt in a safe way. The theoretical backgrounds of the heat transfer processes within a fluid (melt) with a volumetric internal heat source were discussed in detail. For the suggested core catcher concept as the first step a one-dimensional modelling was accomplished through which the procedures as well as the pertinent boundary and initial conditions respectively, required to perform the thermal design of a core catcher for a 875 MWth. helium cooled fast breeder reactor were near described (chapter 3 and appendix 2). It was shown that such a one-dimensional modeling for the lack of proper Nu-equations as well as the relevant fluid dynamics equations and at the same time being forced to take into account too many simplifications thereby would not be sufficient. Therefore a CFD (Computational Fluid Dynamics) computation for the modelling of the suggested core catcher concept was essential. So the thermal performance of the core catcher was surveyed through a CFD-analysis. The simulation was performed using the volume of fluid (VOF) and phase change models within the FLUENT CFD-code. The heat source within the two phase melt (steel and UO2) was considered as a function of the reactor thermal power, the time that the reactor has been operating under normal conditions, and the time after shut-down. Three options have been considered namely: without bottom-cooling, using standard k-epsilon turbulence model (option A) and with bottom-cooling, using two different turbulence models, i.e. the RNG k-epsilon model (option B) and the standard-k-epsilon model (option C). It was found that the suggested core catcher concept matches the safety requirements in all considered cases. Likewise a thermal safety analysis of the reactor cavern was accomplished parallel to that for the along-conceived core catcher. The calculated trend of the erosion (both vertically and laterally) on the internal surface of the reactor cavern showed that the reactor cavern can withstand the thermal load even months after a severe accident in a safe manner. And using the SCALE-code on the basis of CFD-simulation results criticality analyses were performed in addition to ensure if the situation in the core catcher can be considered as sub-critical from neutron-physical point of view. The results showed through out sub-critical conditions in the core catcher.
Degree
thesis:*- Grantor dc:publisher
- Publikationsserver der RWTH Aachen University
- Year dc:date
- 2005
Author and committee
dc:creator, dc:contributor.*- Author dc:creator
-
- Sanei, Nader
- Contributors dc:contributor
-
- Kugeler, Kurt
Subjects
dc:subject × 11Rights
dc:rights- Statement dc:rights
-
- info:eu-repo/semantics/openAccess
- Language dc:language
- ger
Identifiers
dc:identifier.*- OAI identifier oai:identifier
- oai:publications.rwth-aachen.de:61878