The Asteroid Threat and the Safety of Surface Nuclear Installations

Surface nuclear installations are much more vulnerable to impact events than it has traditionally been considered. They can be destroyed by events with energies greater than 100 Mt. According to the most unfavorable (conservative) estimates, the probability of destruction can reach 10^-7...10^-6 year^-1 for certain areas of the Earth. In fact, any cosmic body that can reach the surface of the Earth, or an atmospheric explosion can cause a serious accident to or even completely destroy a nuclear facility. The burden of the radiological consequences of such an accident will be determined by the total activity of radioactive substances located on site and by meteorological factors. The most dangerous (probable) are low-energy events (10⁰...10² Mt). They can occur during the collision of the Earth with a cosmic body with a diameter of 30...200 m. The risk of death resulting from the direct effects of the impact of the given energy is approximately two orders of magnitude lower than the risk of death due to additional radiological impacts of the destroyed facility. Within the energy range of 10²...10⁵ Mt, the radiological consequences of impact events (opposite to non-radiological) will be global. In our opinion, this is a strong argument for the inclusion of impact events into the list of possible external events when assessing the suitability of sites for placement of NPPs and storage facilities for spent nuclear fuel. The safety analysis of the indicated facilities should consider the complexity of the damaging factors (high temperatures, shock, seismic shock, tsunamis) and also the fact that the loads associated with the phenomena induced by the impact will depend on its energy and can greatly exceed the values of loads typical for the region of the facility location