A simulation study of hypervelocity jet underwater: physical protection design of offshore floating nuclear power plant against light torpedo threats

Abstract

An offshore floating nuclear power plant (OFNP), located approximately 30 km from the shore, incorporates lessons learned from the Fukushima Daiichi Nuclear Power Plant Accident. To develop a robust nuclear power plant, ‘security by design’ is crucial to address the unique maritime threats that are absent in traditional land-based plants. This study identifies important but rarely examined maritime-specific threats against OFNP: ‘boarding’ for states that do not authorise security personnel to undertake lethal proactive actions, and ‘light torpedoes’ that pose the threat of a penetration attack with hypervelocity jets. We focused on light torpedoes, simulating the behaviour of the hypervelocity jets generated by shaped charges in water, and assessing the integrity of the OFNP’s double-hull upon impact. An equation model is developed that correlates the jet-tip velocity and water penetration depth, which was verified by the simulation results and previous experiments. We demonstrate that jets decelerated to 0.34 km/s by water did not damage the 25 mm steel plate of the outer hull. The study concludes the required minimum water penetration depth is 4.0 m. The installation of underwater nets is recommended, located at least 5.0 m away from the OFNP, with a safety margin of 1.0 m.