Insofar as the four accidents can be categorised, there is a clear dividing line between the circumstances leading to the early accidents at military facilities (Kyshtym and Windscale) and the later civilian nuclear power plant accidents (TMI and Chernobyl). In his review of Windscale and Kyshtym, Jones2 iden­tified the common factors in these accidents:

‘‘…both occurred at installations whose main purpose was to produce plutonium for their respective national weapons programmes, at a time when pressures to produce the necessary material quickly were extreme; moreover in both cases the processes involved were imperfectly understood and would not be considered safe by modern standards’’.

All four were failures both of equipment and management/operation of that equipment, but the latter two could both have been prevented had the opera­tors taken the appropriate actions in the build up to and during the accidents. In fact, at both TMI and Chernobyl, it appears that the operators’ actions, largely through no fault of their own, contributed significantly to the accident. An important contributing factor to the design and management failures leading to the TMI accident, identified by the President’s Commission,27 was an attitude that nuclear power plants were inherently safe; an attitude which also prevailed in the Soviet Union prior to Chernobyl. The President’s Commission on TMI concluded that:

“The Commission is convinced that this attitude must be changed to one that says nuclear power is by its very nature potentially dangerous, and, there­fore, one must continually question whether the safeguards already in place are sufficient to prevent major accidents’’.

“We are convinced that if the only problems were equipment problems, this Presidential Commission would never have been created. The equipment was sufficiently good that, except for human failures, the major accident at Three Mile Island would have been a minor incident. But, wherever we looked, we found problems with the human beings who operate the plant, with the management that runs the key organization, and with the agency that is charged with assuring the safety of nuclear power plants’’.27

Since both TMI and Chernobyl, major improvements have been made in power plant design and in the safety culture of the nuclear industry. But the recent accident at the Fukushima Daiichi nuclear power plant serves as a reminder that extreme events can and do happen. The nuclear industry and regulators must not allow the belief to take hold that major accidents are impossible. It was a major earthquake and Tsunami which caused the Fukushima accident, but a human planning failure player a important part.

In terms of environmental and human health impacts, it is obvious that releases of radioactive materials at Kyshtym and Chernobyl had major impacts on the human population both in terms of enhanced cancer risk and, impor­tantly, the social, psychological and economic impacts of permanent evacuation. Though many radiation-induced cancers, even from the Chernobyl accident, are never likely to be epidemiologically distinguishable from ‘‘natural’’ background cancers, it is possible to estimate the cancer effects from estimates of collective dose. Indicative estimates of collective doses from the four accidents is given in Table 4, though this comparison is far from comprehensive, partly because of the difficulty in estimating doses, and partly because different approaches were used in the different studies. Despite these limitations, it is clear the collective doses from Chernobyl were by far the most significant. It is important to note, however, that the influence of atmospheric nuclear weapons testing on the collective dose to the World population was much greater than that for Chernobyl. All of these collective doses are dwarfed by the much greater collective doses to the World population from natural and medical sources of radiation.

The damage to the ecosystem caused by these accidents was severe in small areas where organisms were exposed to extremely high doses in the period fol­lowing the releases. However, long-term environmental damage from chronic,

lower level, radiation is less clear. Evidence of long-term damage to organisms (at a genetic, individual or population level) from these studies is often contra­dictory, partly as a result of poor study design and methods in some studies, but also because of the confounding from other environmental and ecological vari­ables. At both Chernobyl and Kyshtym, the evacuated areas have, in the long term after the accident, been described by some as a ‘‘nature reserve’’ since the damage human influence has on ecosystems has been removed.