The risk of a major nuclear accident

The accident at Fukushima Daiichi, Japan, occurred on 11 March 2011. This nuclear disaster left a lasting mark in the minds of hundreds of millions of people. Much as Three Mile Island or Chernobyl, yet another place will be permanently associated with a nuclear power plant which went out of control. Fukushima Daiichi revived the issue of the hazards of civil nuclear power, stirring up all the associated passion and emotion.

The whole of Part II is devoted to the risk of a major nuclear accident. By this we mean a failure initiating core meltdown, a situation in which the fuel rods melt and mix with their metal cladding. Such accidents are classified as at least level five on the International Nuclear Event Scale. The Three Mile Island accident, which occurred in 1979 in the United States, reached this level of severity. The explosion of reactor four at the Chernobyl plant in Ukraine in 1986 and the recent accident in Japan were classified as level seven, the highest grade on this logarithmic scale.1 The main difference between the top two levels and level five relates to a significant or major release of radioactive material to the environment. In the event of a level-five accident, damage is restricted to the inside of the plant, whereas, in the case of level-seven accidents, huge areas of land, above or below the surface, and/or sea may be contaminated.