Numerical Simulation of Pressure Wave Propagation and Its Effect on Damage to the Reactor Cavity under TNT Detonation for Steam Explosion

In a severe accident, molten corium may penetrate the reactor pressure vessel and enter the cooling water in the reactor cavity, and then a steam explosion may occur. Steam explosions can initiate pressure waves and threaten the structural integrity of the reactor cavity. To investigate the propagation characteristics of the pressure waves, including the propagation pattern, attenuation, and amplification under TNT detonation, a coupled numerical approach combined with arbitrary Lagrangian-Eulerian and fluid-structure interaction methods are utilized. The peak pressures of the incident and reflected shock waves decrease rapidly with increasing distance from the charge center, whereas the reflected pressure in the reactor cavity can be between 1.30 and 1.67 times the incident pressure. Then, structural analysis is performed to evaluate the damages to the concrete, liner plate, and reinforcements. From the numerical results, localized and superficial concrete damages are observed in the reactor cavity and the basemat; however, the risk of damage to the concrete, resulting in the collapse of these components is very low. The risk of damage to the liner plate and reinforcements is also very low since the maximum strain values are much lower than the failure criteria. Finally, the structural integrity of the reactor cavity will be maintained during the TNT detonation for the steam explosion.