Structural Integrity Evaluation of a Reactor Cavity during a Steam Explosion for External Reactor Vessel Cooling

Abstract

Nuclear power is a major source of electricity in the international community. However, a significant problem with nuclear power is that, if a severe nuclear accident occurs, radiation may leak and cause great damage. As such, research on nuclear safety has become increasingly popular worldwide. In this paper, the structural integrity of a reactor cavity during a steam explosion—one kind of the aforementioned severe nuclear accidents—was evaluated. Steam explosions are primarily caused by fuel–coolant interactions (FCI), and result from issues in the cooling system that discharges the melt from the reactor core to the outside. A steam explosion can damage the nuclear power plant, and radiation leakage, the greatest concern, may occur. In the Chernobyl or Fukushima Daiichi accidents, significant radiation leakages resulted in damages extending beyond the country of origin. In this paper, a steam explosion was simulated using values given by the transient analysis code for explosive reactions (TRACER-II)—the only steam explosion code in Korea. The walls of the reactor cavity were modeled after the APR-1400 currently operating in Korea. The integrity of the concrete, rebars, and liner plate in the reactor cavity during a steam explosion was evaluated in terms of stress and ductile failure strain limits.

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

“…Therefore, numerous studies have been conducted on energetic explosive phenomena for the steam explosion in a severe accident [1,[8][9][10]. However, limited research has been carried out on explosion loads and their effects on components or structures in the containment buildings [3,[5][6][7]11]. In their studies, the pressure profiles caused by the steam explosion were simulated using computational fluid dynamics (CFD) or hydrodynamics codes, and then they were implemented into finite element analysis [3,[5][6][7]11].…”

“…However, limited research has been carried out on explosion loads and their effects on components or structures in the containment buildings [3,[5][6][7]11]. In their studies, the pressure profiles caused by the steam explosion were simulated using computational fluid dynamics (CFD) or hydrodynamics codes, and then they were implemented into finite element analysis [3,[5][6][7]11]. Then, the dynamic response of the components or structures of the reactor cavity was numerically evaluated [3,[5][6][7]11].…”

“…In their studies, the pressure profiles caused by the steam explosion were simulated using computational fluid dynamics (CFD) or hydrodynamics codes, and then they were implemented into finite element analysis [3,[5][6][7]11]. Then, the dynamic response of the components or structures of the reactor cavity was numerically evaluated [3,[5][6][7]11]. In the previous study conducted by Kim et al [3], the hydrodynamics code, i.e., TEXAS-V, and the computational fluid dynamics code, i.e., ANSYS CFX v. 14, were combined and used to simulate the pressure time histories in accordance with ten postulated conditions under the steam explosions.…”

“…Even though the internal facilities and structures were severely damaged by the pressure waves, it was determined that negligible damage to the containment was observed, and structural integrity was maintained [7]. Park et al [11] utilized the transient analysis code for explosive reactions (TRACER-II) to perform a numerical simulation of a steam explosion load. The damages to the concrete, rebars, and liner plate in the reactor cavity for the APR-1400 containment during a steam explosion were subsequently evaluated [11].…”

“…Park et al [11] utilized the transient analysis code for explosive reactions (TRACER-II) to perform a numerical simulation of a steam explosion load. The damages to the concrete, rebars, and liner plate in the reactor cavity for the APR-1400 containment during a steam explosion were subsequently evaluated [11]. Their study concluded that the structural integrity of a reactor cavity was guaranteed during a steam explosion [11].…”