There are three types of loading caused by the passage of a tornado over a site of the nuclear power plant: 1) wind pressures caused by the direct aerodynamic action of the air flow on the structures, 2) atmospheric pressure change effects and 3) significant impactive forces caused by tornado-borne missiles. Impact forces are determined by the missile’s velocity, mass, shape and material properties, often reaching speeds that result in severe local damage, such as piercing, scabbing on reinforced concrete walls or other barriers protecting safety systems of the plant.

The Tornado Missile Risk Evaluator (TMRE) was used to address questions concerning vulnerability to tornado missiles. The TMRE is a hybrid methodology comprised of two key elements: 1) a deterministic element to establish the likelihood that a specific structure, system, or component (target) will be damaged by tornado-generated missile, and 2) a probabilistic element to assess the impact of the missile damage on the core damage and large early release frequencies. Application of the methodology and the results are presented in the paper and the safety measures are described, suggested to decrease the risk.