Multi-Dimensional Thermal-Hydraulic Analysis for Horizontal Tube Type PCCS

A passive containment cooling system (PCCS) using a shell-and-tube type heat exchanger has been developed as a decay heat removal system following a severe accident. A horizontal heat exchanger has been studied for the PCCS heat exchanger since it has several advantages over a vertical large diameter tube heat exchanger that was originally proposed for the SBWR. Based on the fundamental thermal-hydraulic test using a single horizontal U-tube, the feasibility of the horizontal tube type PCCS has been confirmed, and the analysis models for the steam condensation heat transfer with a non-condensable and the pressure loss with steam condensation have been established. In addition, the criterion for the film dryout type heat transfer deterioration in the boiling side has been clarified in the test. The heat exchanger performance is affected by the multi-dimensional thermal-hydraulic behavior in the cooling water pool and the interactions among the multiple heat transfer tubes. In order to clarify the multi-dimensional behavior, numerical analyses have been conducted employing a two-fluid model. From the analyses results, it has been confirmed that the horizontal PCCS heat exchanger meets the design requirements for both the heat removal and the pressure loss and there would be no film dryout type heat transfer deterioration occurred in the cooling pool.