A Methodology for Risk Assessment and Management for Nuclear Power Plant SMR Hit by High Explosive Warheads

Abstract

Within its 2050 energy plan, Israel examines the demographic implications of a Nuclear Power Plant (NPP) in Shivta Rogem site in the Negev. NPP would have a great contribution to the diversity and robustness of energy sources in Israel. A Small Modular Reactor (SMR) is designated to be safer than existing NPPs and will have better resistance to external hazards due to inherent passive safety features. This study develops a risk assessment methodology for a Nuclear Power Plant (NPP), in particular, SMR, to withstand a large conventional warhead explosion (GBU-28). The methodology comprises: hydro-dynamic simulations, validation of the dynamic simulations using numerical analysis compared to the simulations, risk analysis and damage assessment given the reference scenario of a detonation of a GBU-28 inside the underground water pool of a NuScale SMR. Discrete fragility curves were developed to evaluate the capacity of the SMR critical components. The overall probability of failure was assessed based on a Fault-Tree-Analysis (FTA). Results of the 3 m explosion from the reactor bay wall showed a displacement of 13 cm, breaching of the SMR bay wall and the water pool wall, and 12 cm deflection of the Containment Vessel (CNV). Sensitivity analyses of the uncertainty values were carried out by posting HCLPF (High Confidence Low Probability of Failure) values to the fragility curves. Combination of the results of the study with the failure criteria of NuScale for seismic hazards reveals that given the hazard scenario, core damage is expected accompanied by release of radioactive materials to the atmosphere. The study concludes that building the SMR in Israel will require adapted protective solutions. Future research may examine protective alternatives such as adding a reinforced concrete protecting layer or the possibility to set the SMR at a deeper underground elevation.