Investigation on the start-up features of secondary-side passive residual heat removal system

In order to study the start-up characteristics of passive residual heat removal (PRHR) system, a numerical model is established to calculate the transient characteristics of secondary-side PRHR system under station blackout (SBO) accident. The results show that two-phase flow oscillation occurs during the establishment of natural circulation. This is caused by the mismatch between the variation of reactor residual heat power and the PRHR system operation power. In this paper, a thermal energy storage device is introduced to remove the high residual heat power of the reactor at the initial stage of shutdown. The latent thermal storage device using phase change materials (PCMs) as heat storage medium has the advantage of high potential heat storage density and almost constant phase change temperature. This new configuration can eliminate the flow oscillation phenomenon and reduce the maximum pressure of the steam generator. (author)