Some Examples

5.1 INTRODUCTION

Incidents at nuclear power stations create a great deal of public interest and sometimes concern and alarm.

Many incidents occurred in the 50-year period up to 1995, though very few resulted in injury or death to plant operators or the general public. Mosey 0990) lists 60 or so separate events, and even this list is probably not compre­hensive. The three most serious events are the accidents at Windscale 0957), Three Mile Island 0979), and Chernobyl (1986). Brief details of each are in­cluded in this chapter.

Designers of nuclear power stations do assess the risks and consequences beyond the basis adopted for design. However, prior to Chernobyl, the actual release of radioactive fission products from nuclear accidents had been very much less than predicted from such analyses, indicating their general conser­vatism. Accidents can be examined by looking at which of the three basic safety principles, the Three Cs—control the reaction, cool the fuel, and contain the ra­dioactivity, has been breached and to what extent the overall defense in depth has been challenged.

If the world is to benefit from nuclear energy in the longer term despite the potential dangers involved, it is essential that the lessons learned from each ac­cident or incident are incorporated into future designs and into operator train­ing and safety management to make existing stations safer. It is beyond the scope of this book to examine all these incidents. Rather, we will select those examples which illustrate specific points we have highlighted in previous chap-

ters. The examples are chosen to illustrate both type of fault and type of reac­tor, as follows:

Light water-cooled reactors SL-1

Millstone 1

Browns Ferry 1 and 2

1bree Mile Island-2

Ginna

Mihama-2

Chernobyl

Heary water-cooled reactors NRX Lucens