Scenario for the severe beyond design basis accident at Kola NPP and its radiological consequences

Primary pipeline break LOCA with simultaneous loss of power in Kola-1 Reactor were assumed for the beyond-design-basis reference accident. Thermal-physical calculations for this reference accident were made using MELCOR code. Analysis of the reference accident indicates the following: 1) Fission products release occurs during the first hour of the accident. It includes a maximum of 3% of volatile products and 7% gases contained in the core. 2) The thyroid inhalation dose for 1 to 8 years old children at an early fase of the accident (10 days) exceeds the interventional level (500 mSv) specified in Russia for obligatory evacuation up to a distance of 24 km from the Kola NPP. For adults (5000 mSv) evacuation up to 3 km is specified. 4 refs., 2 tabs