A sodium coolant accident analysis code is necessary to provide regulators with a means of performing confirmatory analyses for future sodium reactor licensing submissions. MELCOR and CONTAIN, which are currently employed by the U.S. Nuclear Regulatory Commission (NRC) for light water reactor (LWR) licensing, have been traditionally used for level 2 and level 3 probabilistic analyses as well as containment design basis accident analysis. To meet future regulatory needs, new models will be added to the MELCOR code for simulation of Liquid Metal Reactor (LMR) designs. Existing models developed for separate effects codes will be integrated into the MELCOR architecture. This work integrates those CONTAIN code capabilities that feasibly fit within the MELCOR code architecture.

Implementation of such models for sodium reactor simulation into an actively maintained, full-featured, integrated severe accident code fills a significant gap in capability for providing the necessary analysis tools for regulatory licensing. Current work scope will focus on the following implementation goals:

• Phase 1: Implement sodium Equations of State (EOS) as a working fluid for a MELCOR calculation from:

○ The fusion safety database


○ The SAS4a Code

• Phase 2: Examine and test changes to the CONTAIN-LMR Implemented by Japan Atomic Energy Agency, specifically:

○ Aerosol Condensation

○ Implementation of the capability for simultaneous sodium and water condensation modeling

• Phase 3: Implementation and Validation of CONTAIN physics models:

○ Sodium Spray Fires (including new test data)

○ Sodium Pool Modeling

○ Sodium Pool Fires

• Phase 4: Implementation and Validation of CONTAIN chemistry models:

○ Debris Bed/Concrete Cavity Interactions

○ Sodium Pool Chemistry

○ Atmospheric Chemistry

An option for changing the EOS for the MELCOR working fluid from water to liquid metal and the heat transfer from water/steam to liquid metal has been implemented into MELCOR. The property models implemented include an analytic EOS model developed for the SIMMER-III code and the fusion safety works done at Idaho National Laboratory (INL). This paper provides a summary of the status of the code development work. A description of the current models implemented together with user requirements and test calculations will be presented.

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