Preliminary study on a new self-sealing strategy for nuclear reactor containment buildings using phase change materials

Nuclear containment buildings are designed as the final barriers to prevent the release of radioactive materials. A containment building consists of a containment liner plate (CLP) and a thick concrete wall. Concrete inevitably deteriorates due to a variety of factors, including the continuously applied load and plastic shrinkage. This continued deterioration could cause cracks in the concrete, which may extend through the entire concrete wall. This would ultimately compromise the ability of a containment building to serve as a final barrier between a nuclear power plant and its surroundings. As a passive measure to repair cracks, research on self-healing concrete has been conducted. In general, self-healing concrete is made by adding a healing agent or bacteria to a concrete mix. However, the previous self-healing concepts cannot be easily applied to current nuclear containment buildings since changes in the chemical composition of concrete mixes cause the changes in the mechanical properties of concrete; thus, a different containment design that matches the changed properties is required. Therefore, in this study, a new self-sealing strategy based on a phase change material (PCM) is introduced, in which the PCM seals a crack physically rather than chemically. To investigate the feasibility of this new strategy, numerical simulations with a thermal analysis were conducted. In addition, experiments were carried out to validate the results of the numerical simulations. The numerical simulations show that the PCMs can seal cracks with maximum sizes of 1.3 mm and 1.8 mm when the inlet temperatures are 60 degrees C and 55 degrees C, respectively. Finally, based on the results of successful PCM sealing, even with several conservative assumptions that make it difficult for the PCM to seal a crack, it is concluded that the new self-sealing strategy is indeed feasible.