Design of LMR reactor structures in the vicinity of hot pool free surface regions subjected to moving elevated temperature cycles

Abstract

In this paper, the structural damage on the reactor structures in the vicinity of the hot pool free surface regions are investigated to check design validity and to propose a modified reactor baffle (RB) design with a Y-piece type cylindrical thermal baffle (TB) structure. Detailed thermal and stress analyses for an envelope thermal transient load of the Passive Safety Decay Heat Removal System event are carried out for both the original design and the modified design. From the results of the analyses, the maximum stresses for the RB and the reactor vessel occur in the level of hot pool free surface regions after primary pump flow coastdown. The modified RB design with the TB structure leads to a significant reduction of the thermal stress, the inelastic creep ratcheting strain, and the creep-fatigue damage compared with those of the original design. Finally, it is verified that the proposed design modification is acceptable in the Korea Advanced Liquid Metal Reactor structural design for hot pool free surface regions.