Development and verification of a component-level hydrogen transport model for a DEMO-like HCPB breeder unit with OpenFOAM

Abstract This work describes the development of a numerical model to simulate transient tritium transport on the breeder unit (BU) level for the EU helium cooled pebble bed (HCPB) concept for DEMO. The key output quantities of the model are the tritium concentration in the purge gas and in the coolant and the tritium inventory inside the BU structure. The model capabilities should cover normal operation as well as accident conditions. The Open Source Field Operation And Manipulation framework OpenFOAM serves as the basis for the model. Equations and boundary conditions required for hydrogen isotopes transport are implemented. Realistic properties data as diffusion constants and Sieverts constants are required, too. A key model issue is solid-fluid interface mass transfer. Two correlations that (1) approaches Sieverts equilibrium in the diffusion limit and (2) a rate dependent correlation that includes the diffusion limit for very high ad-/desorption rate constants are introduced. A two species interface mass transfer correlation based on the single species rate dependent correlation is developed, too. First verification calculations are compared to analytic solutions and TMAP calculations.