PIRAT - An Analytical Tool for Insertion Reliability Assessment of Reactivity Control Systems - Progress and Applications to Sodium Fast Reactors

Abstract : Reactivity Control Systems (RCS) are essential safety components for nuclear reactors. One of the most difficult situations these systems experience is seismic motion due to the large deformation, which can influence the crucial responsibility for reactor shutdown. This paper introduces a new method for dynamic modeling that accounts for the contact and free motion of the mobile part of the RCS with the guiding sleeves. The new method introduces springs with a gap to account for material interaction. This method is implemented into the DEBSE solver within PIRAT, a toolbox currently in development for RCS design. The work presented in this paper explores the dynamic effects on a model (tentatively representative) system to investigate the assumptions made in some previous works using a quasi-static simulation. Based on the frequency of excitation, various responses are seen that are not captured in the quasi-static simulations. This work gives evidence to the importance of the dynamic modeling of RCS.