Transposition of 2D Molten Corium–Concrete Interactions (MCCI) from experiment to reactor
•Simple scaling rules and approaches for MCCI are outlined and discussed.•A detailed MCCI code is compared with simplified approaches.•The assumption of a quasi-steady-state energy balance is an adequate simplification.•Simplified procedures are a useful code-independent scaling-up method for MCCI....
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| Published in: | Annals of nuclear energy Vol. 74; no. C; pp. 89 - 99 |
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| Main Authors: | , , , , |
| Format: | Journal Article |
| Language: | English |
| Published: |
Elsevier Ltd
01-12-2014
Elsevier Masson |
| Subjects: | |
| Online Access: | Get full text |
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| Summary: | •Simple scaling rules and approaches for MCCI are outlined and discussed.•A detailed MCCI code is compared with simplified approaches.•The assumption of a quasi-steady-state energy balance is an adequate simplification.•Simplified procedures are a useful code-independent scaling-up method for MCCI.
In the course of a severe accident in a light water reactor, the interactions of corium with the concrete structures of the reactor cavity (Molten Corium–Concrete Interactions or MCCI) may have a significant impact on the long-term integrity of the containment. The 2D behaviour of the melt pool contained in the reactor cavity under dry or top flooding conditions is considered as one of the key phenomena.
The “scaling” issue is usually resolved by – in a first step – identifying the impact of physical mechanisms on the process and – in a second step – evaluating these mechanisms at scaled conditions regarding time and length. The conditions for the MCCI change with time due to the evolution of the melt’s state defined by e.g., its composition, temperature and solid fraction, and due to the change of cavity contour and the decreasing decay heat.
Here, simplified models are investigated with the objective to infer from laboratory-scale experiments how basic and important parameters like the temperature of the melt and the erosion depth evolve with time if transposed to reactor scale. Due to the simplifications in the models under consideration, the MCCI is analysed assuming “ideal” boundary conditions as e.g., an evolution of a cavity contour with time while retaining its geometrical shape (sphere, cylinder, etc.). Based on these idealised assumptions, generic trends for physical parameters like melt temperature, heat flux at the pool boundary surface, concrete fraction in the melt, viscosity, etc. can be deduced.
Simple scaling methods are introduced and checked for consistency by comparison calculations with the MCCI MEDICIS module of the ASTEC integral code. Finally they are applied to a scaling problem under ideal and simplified initial and boundary conditions and the resulting generic trends of the physical parameters are evaluated at reactor scale. Such methods are very useful to better understand the MCCI phenomenology although more detailed MCCI codes are indispensable to simulate more complex accident sequences or to take into account complex boundary conditions. |
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| Bibliography: | ObjectType-Article-1 SourceType-Scholarly Journals-1 ObjectType-Feature-2 content type line 23 |
| ISSN: | 0306-4549 1873-2100 |
| DOI: | 10.1016/j.anucene.2014.07.009 |