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London. This is not because such an earthquake is impossible in London, but because enough is known about earthquake prone zones to show that the possibility of such an occurrence is, for all practical purposes, indistinguishable from zero. The same argument applies to a number of large chemical plants, fuel stores and transport operations. They may contain large inventories of dangerous materials, but safety studies have shown that in many
situations the likelihood of a major incident is so remote as to not justify an evacuation plan for the surrounding area.
In the same way when considering reactor accidents there are some scenarios which are so incredible that detailed contingency planning for them is not justifiable. Nevertheless contingency plans for reactor accidents should be flexible enough to allow them to be extended to deal with large, less credible, accidents.
The advice given in this report covers a large range of potential accident scenarios from the very small, having no physical effects upon Hong Kong, to the very large, potentially having a major impact. Very large accidents are highly improbable, and detailed planning for their occurrence is not generally considered justifiable. However, because of the good emergency organisation which already exists in Hong Kong to deal with natural disasters, such as typhoons, it is relatively easy for the advice given in this report for dealing with large accidents, which are themselves improbable, to be extended to deal with very large catastrophic accidents, and this has been done. By considering such improbable accidents the recommended organisation and plans will be available to deal with all credible accidents at the Daya Bay site.
The aim of this report is therefore to provide a comprehensive contingency planning guide for Hong Kong, tailored specifically to dealing with potential accidents at the Daya Bay plant including very large, beyond design-basis, accidents (see Section 5.1). The specific aims are:
(i)
to discuss the need for a contingency plan;
(ii)
to set out in detail what the plan should contain;
(iii)
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(iv)
(v)
to propose a structure for the emergency organisation;
to give guidance on countermeasures and when those countermeasures should be introduced; to give guidance on the level of resources which will be needed to implement the plan.
In order to achieve these objectives it is felt that some background information on nuclear reactors, radiation, and nuclear reactor accidents should be included in this report. These chapters will help to set the scene for the later chapters on the more detailed aspects of contingency planning.
Worldwide there have been a small number of reactor accidents over the past thirty or forty years of reactor development. Notably there have been the accidents at Windscale (UK, 1957), Three Mile Island (USA, 1979) and Chernobyl (USSR, 1986). It is important that lessons are learnt from these accidents, however, if an accident were to occur at a reactor in the future it would almost certainly not be a carbon copy of
any previous accident. Emergency planners must always ensure that their plans are flexible and they do not prepare exclusively for a single scenario accident.
This is a report on contingency planning for Hong Kong. It is not in itself "The Contingency Plan for Hong Kong'. This will eventually be contained in the standing orders, etc., of a number of organisations who would be involved in the event of an incident at the Daya Bay plant which could affect Hong Kong.
It is anticipated that the first reactor at Daya Bay should become operational in 1992. The Contingency Plan for Hong Kong should be devised and have been exercised prior to the first fuel loading of the Daya Bay reactors. In order to achieve this a single authority is required to co-ordinate the development of the Plan. This co-ordinating authority is already in existence in the form of the 'Government Committee for Contingency Planning'.
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