Investigation on Operation of the Compact Molten Salt Reactor by Modelling the Primary Circuit in GeN-FOAM

Sammanfattning

In recent years there has been a revision of the molten salt nuclear reactor concept for production of power. Moving of fissile material throughout the primary circuit for these types of reactors creates the necessity of novel physics solvers to study movement of delayed neutron precursors, plant operation, accident scenario's; crucial for design. GeN-Foam is an open source extension of the C++ OpenFoam library tailored for simulating next generation nuclear reactors, including movement of delayed neutron precursors. Using this numerical tool, an investigation is made into simple physical transport problems related to delayed neutron precursors. Goals of the thesis include verification of GeN-Foam using simple models, asserting mesh-independence for the 3D core model and calculation of the effective delayed neutron fraction in geometries representing the Compact Molten Salt Reactor developed by Seaborg in Denmark. Estimation of the effective delayed neutron precursor fraction by numerical and analytical approaches are given for a simple pipe with laminar flow containing a critical core region, a simplified geometry of the CMSR core area, and a full 3D model of the primary circuit of the CMSR. Results show good agreement between numerical and analytical results for the simplified models, while for the 3D model there was a difference for calculating the delayed neutron fraction, possibly due to the difficult implementation of mass-flow in GeN-Foam and the lack of mesh refining capabilities of the used meshing software, Salome. Nevertheless results show large agreement between the numerical and analytical results, showing GeN-Foam to be a viable tool for the study on molten salt reactors.