Development of an SP3 neutron transport solver for the analysis of the Molten Salt Reactor

The aim of this paper is the extension of a multiphysics OpenFOAM solver for the analysis of the Molten Salt Fast

Reactor (MSFR), developed in previous works (Cervi et al., 2017, 2018). In particular, the neutronics sub-solver

is improved by implementing a new module based on the SP3 approximation of the neutron transport equation.

The new module is successfully tested against a Monte Carlo model of the MSFR, in order to assess its correct

implementation. Then, a neutronics analysis of the MSFR is carried out on a simplified axial-symmetric model of

the reactor. Particular focus is devoted to the analysis of the MSFR helium bubbling system and its effect on

reactivity. The presence of bubbles inside the reactor is handled with a two-fluid thermal-hydraulics module,

previously implemented into the solver. The void reactivity coefficient is evaluated on the basis of the bubble

spatial distribution calculated by the multiphysics solver. Then, the results are compared to simulations carried

out with uniform bubble distributions, highlighting significant differences between the two approaches. The

outcomes of this work constitute a step forward in the multiphysics analysis of the Molten Salt Fast Reactor and

represent a useful starting point for the optimization of the MSFR helium bubbling system, as well as for the

development of appropriate control strategies.