Derived intervention levels in the early stage of a nuclear accident

A method of determination of derived intervention levels for temporary evacuation of inhabitants in the case of nuclear accident of VVER NPP type is described. 21 accidental sequences which may leads to the uncontrolled release of radioactive material to the environment have been analysed. Effective doses for 48, 168 and 732 hours at distance of 5, 15 and 30 km from the source have been assessed on the base of results of calculating the kerma rate in air. It has been supposed that monitoring will be performed 2 hours after finishing the accidental release. The exceeding of 50 mSv intervention level up to 48, 168 and 732 hours might be expected if kerma rate in air (DIL1) exceeds 0.4, 0.2 or 0.2 mGy·h−1, respectively. Determination of effective doses at distances under consideration also enables to assess the length of zone for planning the temporary evacuation (DIL2). The zone length at meteorological situation of Pascquill stability categories D, height of release 25 m and wind speed 2m·s−1 may exceed 30 km at the axis of the hypothetical track.