Core deformation analysis by 'FINAS'. Elastic deformation of core models due to temperature distribution

It is important to understand the deformation behaviors of FBR core in the aspects of safety and economy, i.e., the reaction change in the transient period, the fuel life expectation, and the removal of subassemblies. The aim of this analysis is to investigate the effects of the position of pads, the clearance and the friction between pads, which are considered as factors for core deformation. Thermal deformation analyses of an example core model with 127 subassemblies which were referred to 'JOYO''s were conducted by using FINAS'. The followings were obtained. (1) The pad position: The reaction force due to contact between pads increased as the lower pad position rose, while the maximum deflection between upper and lower pads decreased. In the case of high position of lower pad, the center lines of subassemblies deflected outward at the level of fuel pellet region. (2) The clearance between pads: As the clearance increased, the reaction force decreased. However, the deflection increased and the deformation pattern changed before and after contact occurred. This made the deformation behaviors complex. (3) The friction between pads: The effect of the existence of friction was not observed except axial stress. The possible reasons are that an exisymmetric temperature distribution was used in the analyses, and that the bending moment due to friction force was not involved. To solve the latter, some new model must be developed. (J.P.N.)