Radiological Aspects of Public Protection at Early Release Stage of NPP Severe Accident

In the modern world, nuclear energy is one of the most economically feasible sources of energy. Although related risks are of a great public interest, they are quite obvious and predictable. The steady risk reduction trend is based on two main areas: improvement of nuclear power plant design basis and enhancement of emergency preparedness at all levels. Such a trend is maintained by more strict requirements for licensees from states and international competent authorities. Recently, practical elimination of an early radioactive release at a nuclear power plant is one of the most significant requirements for NPP safety. The paper covers issues focusing on how this requirement will be implemented within national radiation safety standards, namely within the regulations of the third group on intervention in the case of a radiological emergency, and whether Ukraine is ready to implement this standard for operating NPPs. The paper addresses the following issues: determination of an early release, available interval, theoretical grounds applied to assess an early release and public exposure doses. All the results presented in the paper are of an evaluative nature. The attention is focused not on specific features of a particular power unit or settlement, but on general physical principles of modeling the source term and protective properties of the premises.