Reactor Accidents (or the potential for accidents) are undoubtedly a public concern for the continued operation of the civil nuclear power programme. There have been comparatively few serious accidents but those that have occurred, e. g. Three Mile Island-Unit 2 (TMI-2) and Chernobyl have had a pronounced affect on the expansion (or lack of it) in the nuclear developed countries.

A good review of the accident record of the nuclear industry is given by Mounfield (1991). Some incidents have occurred during the handling of industrial isotopes or other exposures to ionising radiation; these have resulted in a small number of fatalities. Some accidents have happened at experimental facilities; e. g. a criticality accident occurred in 1961 in a small prototype BWR reactor (SL-1) located at Idaho in the US resulting in the death of three technicians. Other accidents have been recorded in experimental and power reactors involving criticality and also fuel melting. A partial fuel meltdown occurred at St Laurent 1, a 480 MWe plant in France in 1969. Incidents have taken place at San Onofre 1 in California in 1973, Brown’s Ferry, Alabama in 1975 and other more minor (but still serious) events have occurred on some other plants.

In the UK, the only serious accident that caused public concern was the Windscale fire. This fire resulted in significant releases of radioactivity; estimates of 20,000 Ci of I-311 are given by Mortin (2000). As a consequence of this accident, 14 workers at the plant received serious doses of radiation, and there was a suspension of milk production in the surrounding area.

The first most damaging event in terms of limiting nuclear power plant expansion was the TMI-2 accident in 1979. The accident resulted, partly through mismanagement, in a severe core melt down that threatened the integrity of pressure vessel boundary. TMI-2 had various important consequences. It effectively terminated the construction of new power plants in the US (Chung, 1998). It also impacted on the philosophy of approach to severe accident safety. Previously, attention had focussed almost entirely on prevention, after TMI-2 there was a much increased focus on accident mitigation. Nevertheless, despite the substantial core melting, the only significant releases to the public resulted from Xenon-133 and the health consequences were not judged to be significant.

A study was carried out (Blee, 2001) to look at lessons learned over the last 22 years since the TMI-2 accident (Table 2.13).

Table 2.13. Lessons learned from the post-TMI-2 and Chernobyl era

Along with safe operations and good economics, effective communication is vital, particularly in the aftermath of abnormal events

Industry fortunes are global as further demonstrated by Chernobyl — crisis management is vital Environmental linkages have yet to embraced — the beneficial role of nuclear energy in protecting the environment should be proposed The need to manage media publicity Recognition of the benefits of long-term vision

Blee (2001).

The World’s worst nuclear power plant accident occurred at Chernobyl in 1986. The consequences of this accident have been much discussed and publicised. This accident resulted in a massive explosion, dispersing radioactivity over much of Northern Europe. The cause was essentially operator error but subsequent investigation indicated major weaknesses in both technical specifications and management. The Chernobyl accident resulted in moratoria for the construction of nuclear plants in some European Countries, e. g. Italy.

A relatively recent incident involving fatalities occurred in 1999 at the Tokai-mura uranium processing plant in Japan (Suzuki, 2000). This accident resulted from a fission reaction in a precipitation tank of uranyl nitrate solution. Several workers suffered severe radiation sickness ultimately resulting in their deaths, several months after the incident. This accident was investigated in depth and various deficiencies in operating processes (operational and technical, management and control), in the licensing process and in the safety regulations were identified.

As with most industries, experience from accidents has resulted in the implementation of better operational practices and technical improvements. Many of the accidents to date have resulted from human error and the need for improved training and understanding of ‘human factors’ issues is one of the most significant lessons learned.