Modelling of core molten material fast vaporisation and expansion for the evaluation of sfr severe accident consequences - Université de Lorraine Access content directly
Conference Papers Year : 2022

Modelling of core molten material fast vaporisation and expansion for the evaluation of sfr severe accident consequences

A Mouly
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N Seiler
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F Bertrand
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Abstract

The fourth generation of sodium fast reactors (SFR) is developed taking into account severe accidents as soon as the pre-conceptual phase is under way in order to increase safety margins. In this context, parametric and fast-running tools are used in addition to mechanistic tools during the reactor design phase for probabilistic margin evaluations. The present paper is dedicated to preliminary transient modelling and studies of the expansion phase using a new parametric tool named MOREINa. Potentially occuring after a secondary power excursion in a SFR with low void worth core (non energetic primary phase), the expansion phase implies a vaporisation of superheated materials, their expansion and their interaction with the coolant, potentially jeopardizing the vessel mechanical integrity. MOREINa has a new expansion phase model considering both fuel and steel in order to evaluate the energy released during this secondary phase and its consequences on the reactor vessel structures. This modelling, based on dimensional analysis and involving mass, momentum and energy balances, is done to simulate the vaporisation of two overheated liquids whose vapors supply a bubble of vapour and fission gases, the bubble expansion due to pressure difference between the bubble and the cover gas located at the top of the vessel and finally the FCI induced by thermohydraulic instabilities and contributing to the further fragmentation of the molten materials. The energy released is evaluated to assess order of magnitudes of the mechanical loading applied on the reactor vessel. Comparison with a CEA validated parametric tool DETONa are finally presented and analyzed.
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Dates and versions

hal-03727171 , version 1 (19-07-2022)

Identifiers

  • HAL Id : hal-03727171 , version 1

Cite

A Mouly, N Seiler, F Bertrand, Michel Gradeck. Modelling of core molten material fast vaporisation and expansion for the evaluation of sfr severe accident consequences. 19th International Topical Meeting on Nuclear Reactor Thermal Hydraulics (NURETH-19), Mar 2022, Bruxelles, Belgium. ⟨hal-03727171⟩
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