New reactor cavity cooling system with a novel shape and passive safety features

A new, highly efficient reactor cavity cooling system (RCCS) with passive safety features and without a requirement for electricity and mechanical drive is proposed for high-temperature gas-cooled reactors (HTGRs) and very-high-temperature reactors (VHTRs). The RCCS design consists of continuous closed regions; one is an ex-reactor pressure vessel region (RPV region), and another is a cooling region with a heat transfer surface to ambient air assumed to be 40 (°C). The RCCS uses a novel shape to remove the heat released from the RPV with radiation and natural convection efficiently. Employing the air as the working fluid and the ambient air as the ultimate heat sink, the new RCCS design strongly reduces the possibility of losing the heat sink for decay heat removal. Therefore, HTGRs and VHTRs adopting the new RCCS design can avoid core melting due to overheating of the fuels. Moreover, we would like to address a comparison methodology between the RCCS and a scale-down heat removal test facility built at Kyushu University. The scaledown heat removal test facility will obtain valuable experimental data to demonstrate the new RCCS's performance. For example, the heat flux by radiation of the scale-down heat removal test facility can be the same as that of the real RCCS because of the same temperature difference, T⁴ _RPV T⁴ _RCCS, and the same view factor and configuration factor. In addition, we also discussed a comparison methodology through the use of the Grashof Number RCCS RPV Gr_rRCCS-rRPV. When the Grashof Number RCCS RPV Gr_rRCCS-rRPV of the scale-down heat removal test facility is the same as that of the real RCCS, the natural convection of the scale-down heat removal test facility is estimated to be the same as that of the real RCCS; therefore, the experimental data of the scale-down heat removal test facility is enormously valuable to demonstrate the heat removal performance of the real RCCS. Conclusively, we can also define the experimental conditions on radiation and natural convection through the use of the same Grashof Number RCCS RPV Gr_rRCCS-rRPV for the scale-down heat removal test facility in which the RCCS can demonstrate its heat removal performance.