Two-group theory of neutron noise in Molten Salt Reactors

In a previous paper, the kinetics, dynamics and the neutron noise in a Molten Salt Reactor (MSR) was investigated in a simple homogeneous reactor model in one-group diffusion theory. In this paper those investigations are extended to two-group theory in the same reactor model. In addition, unlike in the previous paper where in the quantitative work data from a thermal LWR were used, here material data of a conceptual MSR with a thermal spectrum and thorium fuel are used, along with data from both fast and thermal LWRs. Among other things, the relative weight and the range of the local component is investigated. It is found that the strong neutronic coupling in an MSR, which was pointed out in the preceding paper, diminishes the role of the local component as compared to light water reactors. Some further new features of the noise in MSR, not directly related to the two-group approach, are also found.

► In this study, two-group theory is used to study Molten Salt Reactors. ► A thorium-fuelled concept is compared with reactors using uranium fuel. ► Both static and dynamic properties are studied. ► Molten Salt Reactors have a relatively small local component of the Green’s function. ► Propagating perturbation noise also of interest in traditional reactors.