Basic principles for intervention after a nuclear or radiological emergency

The current status of internationally agreed principles for intervention after a nuclear accident or radiological emergency and the international development of intervention guidance since the Chernobyl accident are reviewed. The experience gained after the Chernobyl accident indicates that the international advice on intervention existing at the time of the Chernobyl accident was not fully understood by decision makers neither in Western Europe nor in the former USSR and that the guidance failed to address adequately the difficult social problems which can arise after a serious nuclear accident. The radiation protection philosophy of today distinguishes between practices and interventions. The radiological protection system of intervention includes justification of the protective action and optimization of the level of protection achieved by that action. Dose limits do not apply in intervention situations. The inputs to justification and optimization studies include factors that are related to radiological protection, whereas the final decisions on introduction of countermeasures would also depend on other factors. The basic principles for intervention as recommended by international organisations are discussed in detail and the application of the principles on a generic basis is illustrated for long-term protective actions. The concepts of intervention level, operational intervention level and action level are presented and the relation between these quantities is illustrated. The numerical guidance on intervention in a nuclear accident or radiological emergency or a chronic exposure situation given by ICRP, IAEA and in the Basic Safety Standards is presented. (author)