[en] In the case of a serious accident and as a precautionary measure, several protection actions can be implemented by the prefect during the emergency phase. In France the levels of intervention are given by a ministerial decree of the 13. october 2003, resuming recommendations of the International Atomic Energy Agency. The selected values are: an efficient dose of 10 mSv for the stake under cover and in the listening: the concerned persons have to put under cover in a building, any openings carefully closed and stay in the listening of the orders of the prefect; an efficient dose of 50 mSv for evacuation; an efficient dose to the thyroid of 100 mSv for the taking of stable iodine tablets. In order to help the authorities to choose between the keeping of populations at their place or immediate evacuation the decision criteria are: if the forecasted efficient dose of the first month is under 1 mSv, the populations stay in place; if the forecasted efficient dose is between 1 mSv and 10 mSv a phase of consultation is decided between the prefect and the concerned mayors to stay or to leave. The efficient dose of the first week gives a supplementary information on the exposure evolution during the first month, if the forecasted efficient dose of the first month is over 10 mSv the immediate evacuation is highly recommended. The same levels are used to decide or not a return after evacuation but the forecasting of efficient dose runs on twelve months. (if the forecasted efficient dose on the twelve following months is over about ten of mSv the return of populations in the contaminated area is forbidden). (N.C.)