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the radiological consequences of such a plume. In particular the foodchain will need to be monitored to ensure that the public do not consume foodstuffs containing unacceptably high levels of radioactive contamination. The foodstuff of particular concern is likely to be milk since grazing animals can concentrate the radioactivity deposited over a fairly large area into a few tens of litres of milk.
The actions which can be taken to minimise the potential dose to the public are discussed. These countermeasures are often, in principle, quite simple actions, such as washing food, or banning the consumption of some foodstuffs. Countermeasures for dealing with contaminated food, or drinking water are discussed in detail. With many countermeasures their introduction will involve some social disruption, or even a small risk to the public. It is therefore necessary to ensure that countermeasures are only introduced if they will achieve a net positive benefit. Major countermeasures should not therefore, be introduced when the predicted doses to the public are small as this would do more harm than good.
The level of predicted dose at which certain countermeasures should be introduced are discussed and numerical values given for these Emergency Reference Levels, (ERLs). Because the degree of detriment caused by the introduction a countermeasure will depend to some extent upon the local condition prevailing at the time, it is not possible to give a single value of ERL for each countermeasure. A range of values is given, the lower ERL being the predicted dose level at which introduction of the countermeasure should start to be considered, and the upper ERL being the predicted dose level by which the countermeasure will have almost certainly been introduced. Having decided upon the appropriate ERL value it is necessary to relate this to some measurable quantity, such as the level of radioiodine in milk. The use of these Derived Emergency Reference Levels (DERLs) is discussed.
Any nuclear incident at Daya Bay would attract a great deal of media interest. Advice is given on the setting up and operation of a Press Briefing Centre. Advice is also given on how to communicate specific instructions to the public.
Any contingency plan will only function well if the participants have been adequately trained in their individual roles and the plan has been exercised. Advice is given on the necessary training and also on the planning and execution of emergency exercises.
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