Feasibility Study of Hybrid Heat Pipe with Control Rod as Passive In-Core Cooling System for Advanced Nuclear Power Plant

Abstract

Since Fukushima nuclear power plant accident in 2011, the importance of passive safety has been emphasized during station blackout accidents and associated situation. In conventional emergency core cooling system, refueling water is supplied to the reactor pressure vessel. However, this method had a limitation when pressure inside reactor is too high to inject the refueling water. For passive in-core cooling system (PINCs), the concept of a hybrid heat pipe, which is the combination of a heat pipe and control rod, was proposed for enhanced safety of advanced nuclear reactor. With the unique features of a heat pipe and control rod, the hybrid heat pipe can remove decay heat directly from the core to be inserted into the reactor pressure vessel with the same drive mechanism of a control rod. For demonstrating the feasibility of the hybrid heat pipe, CFD analysis for a single hybrid heat pipe and one-dimensional reactor transient analysis were conducted. Using commercial CFD code, the thermal performance of full-scale hybrid heat pipe was analyzed numerically by solving two-phase flow and heat transfer under high- Temperature and high-pressure conditions in reactors. As a result, the hybrid heat pipe concept was found to remove 18.20 kW per rod with total thermal resistance of 0.015 °C/W. From the one-dimensional reactor transient analysis, the hybrid heat pipe was able to delay core heat-up and coolant boiling, assuring sufficient response time at station blackout accidents. If the hybrid heat pipe had 2.5 times improved heat removal capacity, it could continue cooling the core during accidents while preventing core uncovery. © Copyright (2015) by American Nuclear Society All rights reserved.