Probabilistic Tornado Hazard Criterion for the Nuclear Facilities Siting Areas

Due to the significant potential danger of destructive effects of tornadoes on nuclear facilities (NF), national and international safety standards for NF provide for the study of the climate regime of tornadoes and the organization of appropriate protection of NF. An essential feature of the climate in recent decades is the widespread sharp increase in the number of hazardous weather events, including tornado occurrences. This fact determines the need for statistical processing of data on the tornadoes near NFs and assessment of their characteristics, taking into account the existing tornado hazard criteria for the NF siting areas. This study is focused on evaluating design characteristics of tornadoes using additional data on the tornado occurrences in recent years as well as predicting the risk of tornado hazard in the event of intense tornadoes. On the example of one of the tornado-prone zones in the former USSR, the probability of tornado occurrence was calculated. It has been established that the real danger of tornado impact on the NFs would be possible if two or more additional tornadoes of F5 Fujita scale pass across the survey area. Such a situation is possible with the current trend of climate changes. It is noted that there is a need to provide for the collection and analysis of new meteorological data in order to continue maintaining the existing records of registered tornadoes, as well as to expand the categories of industrial facilities that may be affected by emergency events.