Conceptual Design of Passive Containment Cooling System for APR-1400 Using Multipod Heat Pipe

The Fukushima Daiichi nuclear accident showed that severe events are real—not virtual—threats. In both pressurized water reactor and boiling water reactor nuclear plants, the containment is the last resort against radiation leakage, with the integrity of containment being directly linked to nuclear safety. To maintain the containment below Factored Load Category for 24 h and beyond after core damage, external cooling measures such as a gas vent system and an emergency containment spray backup system have been mandated. With these measures, it is difficult to completely satisfy all the requirements for proper cooling and minimized penetration and leakage while maximizing reliability and meeting the need for a passive design. Accomplishing all of these requires substantial repair and maintenance costs; thus, many difficulties can be anticipated with their implementation. This study proposes the installation of several multipod heat pipe assemblies; such an assembly includes an adiabatic region consisting of one large cylindrical structure penetrating the containment dome, a boiling region, and a condenser region consisting of many pipes that serve as the ultimate heat sink to discharge the decay heat energy from the containment with no radiation leak. Such installation will dramatically improve the nuclear safety in the event of a severe accident.