Passive cooling system in a nuclear spent fuel pool using a vertical straight wickless-heat pipe

To enhance the thermal safety when a station blackout accident occurs, a vertical, straight, wickless-heat pipe is proposed as a passive residual heat removal system on the nuclear spent fuel pool. The heat pipe will remove the decay heat from the nuclear spent fuel pool and keep the system safe. The objective of this research is to investigate the thermal performance of a vertical, straight, wickless-heat pipe that will be proposed as a new passive cooling system on the nuclear spent fuel pool. An experiment was conducted to investigate the heat transfer phenomena and heat pipe thermal performance. It considered the influence of the heat pipe initial pressure, evaporator filling ratio, evaporator heat load, and coolant volumetric flow rate of the water jacket. The simulation with the nuclear reactor thermal-hydraulic code RELAP5/MOD3.2 was performed to support and compare it with the experimental results. Cooled water was circulated in a water jacket as a condenser cooling system. The experimental results showed that the best thermal performance was obtained at a thermal resistance of 0.016 ± 0.0006 °C/W, a filling ratio of 80%, a lower initial pressure, a higher coolant volumetric flow rate, and a higher heat load of the evaporator. The RELAP5/MOD3.2 simulation model can be used to support experimental investigation and predict the phenomena inside a heat pipe. It was compared with other heat pipe research results, experimental and simulation results showed that the vertical, straight, wickless-heat pipe had higher thermal performance and can be proposed as a passive residual heat removal system of a nuclear spent fuel pool when a station blackout occurred.