Nuclear power plants, which are important national facilities, require special attention against the threat of terrorism using various methods. Among the terrorist threats, as structural damage and human casualties due to explosions continue to occur, interest in the blast load is increasing. However, domestic nuclear power plants do not have sufficient design requirements for protection against the threat of explosives. To prepare for the threat of terrorism using explosives, it is necessary to evaluate the physical protection performance of nuclear power plants against blast load, and to use this to improve protection performance and establish regulatory standards. Most of the explosion-proof designs used abroad use the empirical chart presented by UFC 3-340- 02 (DoD 2008), which does not take into account the effect of near-field explosions. When explosions occur inside nuclear power plants, near-field explosions occur in most cases. In this study, it was assumed that explosives were installed in the corridor inside nuclear power plants. A spherical TNT was placed in the middle of the corridor floor to simulate near-field explosions, and the structure response according to the weight of the TNT was evaluated. The corridor was modeled with a reinforced concrete material and the LS-DYNA program was used for analysis. For the explosion model, the Arbitrary-Lagrangian-Eulerian (ALE) analysis technique applying the advantages of the Lagrangian and Eulerian methods were used. By analyzing the pressure history and the degree of deformation of the structure according to the explosion, the degree of threat caused by the explosion was analyzed. Based on the analysis of this study, physical barriers performance database (DB) using Modeling & Simulation (M&S) will be constructed by performing sensitive analysis such as representative structure shape setting, boundary conditions, material of structures, etc. The constructed DB is expected to be used to establish regulatory standards for the physical barriers of nuclear power plants related to explosives.

In response to the increase in international terrorism threats and demands for terrorism prevention and response activities, the Act on Counter-Terrorism for the Protection of Citizens and Public Security was enacted in 2016, and the need for research to strengthen protection against explosive threats was raised. In the same manner, the Design Basis Threats, which become the standard for the design and evaluation of physical protection systems for nuclear facilities, have been developed and it includes explosive threats. However, the regulatory standards for physical barriers against explosive threats are still not established. Therefore, it is first required to set up a performance database of physical barriers subject to blast loading in order to prepare the regulatory standards. In this study, the pressure with the trinitrotoluene (TNT) charge weights of 0.5-2 kg as a function of time was calculated using Ansys Autodyn software by assuming that the TNT is used for malicious purposes and is attached to a reinforced concrete (RC) corridor wall. The shape of the corridor was the 3×3×6 m cuboid with a rectangular hole of 1.78×1.78×6 m. The RC walls, which make up the corridor, contained the reinforcing bars with a spacing of 0.229 m and a diameter of 0.036 m. The spherical charge of a TNT was placed 0.2 m away from a RC wall in the middle of the corridor. To measure the reflected pressure after the internal explosion with a TNT, three pressure gauges were installed on the three sides of the RC walls in the middle of the corridor, respectively. The results showed that the peak reflected pressure on a RC wall with the standoff distance of 0.2 m was about ten times higher than the opposite RC wall with the standoff distance of 1.58 m in the same condition of TNT charge weight. Thus, it was verified that blast loads are highly affected by standoff distance. It seems that preventing the explosive detonation close to a physical barrier is strategically important to maintain the integrity of the physical barrier.