An adaptive spatial kinetic model to simulate reactivity transients from quasi-static up to super-prompt regime

In widely-used codes such as RELAP or PARET the whole reactor core is approximated by some channels, one-channel model, two-channel model and so on. Furthermore, many of the existing transient codes use the point kinetic approximation in order to anticipate the reactor core behavior in transient conditions. This paper propose a spatial kinetic model to improve on the above approximations of existing codes such as RELAP or PARET with respect to reactivity transients in nuclear reactors. The anticipation of the reactor core behavior in transients depends on how much it could be possible to exactly determine neutron spectrum and thermal feedbacks of the core elements. In the reactor core each zone has a specific temperature and its corresponding thermal feedback. In order to decrease the effects of point kinetic approximations, these partial feedbacks in different zones are superposed to show an accurate model of reactor core dynamics. In this manner the reactor point kinetic can be extended to the entire reactor core, hence “reactor spatial kinetics”. In order to determine temperatures of different elements of the reactor core two different thermal hydraulic models are developed: lumped parameter (in quasi-static and time-delayed regimes) and adiabatic model (in supper prompt regime).

► This study presents a spatial kinetic model for reactivity transients.
► The point kinetic equations and adiabatic kinetics are used to track reactor power.
► Lumped parameter and adiabatic approximation are used in the thermal–hydraulic part.
► Cell and core calculations are coupled to reactor dynamics and thermal hydraulics parts.