On reactor neutron noise induced by fuel assembly vibrations in large and small heterogenous water-cooled cores

Paper in proceeding, 2024

A nuclear technology that has been studied in recent years is related to water-cooled Small Modular Reactors (SMRs). For the development of methods for core monitoring and diagnostics, the analysis of reactor neutron noise has been shown to be effective in large Light Water Reactors and its extension to SMRs may be considered. To localize and identify anomalies in the core via reactor neutron noise, it is essential that the deviation from a point-kinetics behavior is strong enough to be seen at least in the readings of some of the in- and ex-core neutron detectors. The point-kinetics response to perturbations is known to be more dominant in smaller cores, so a relevant question to assess is under which conditions reactor neutron noise-based techniques may be applicable to SMR cores. In this paper, a Pressurized Water Reactor core is used to derive a system whose size is close to the size of a possible water-cooled SMR core. Then, simulations are performed to estimate the reactor neutron noise induced by prescribed vibrations of single fuel assemblies, which is one of the most important perturbations to be monitored, at different locations in the two systems. These simulations show that the so-called spatial component of the reactor neutron noise in the small core tends to be weaker, but the system response may also depend on the different types of fuel assemblies and their arrangement in the core.