Defining the options to reduce radiation risks associated with the Techa cascade of water reservoirs

The paper discusses methodological and calculation approaches used to evaluate various radiation risks associated with the world largest liquid radioactive waste storage facility - the Techa Cascade of water reservoirs at FSUE “PA “Mayak” (TCR). The study shows that common risk assessment methods are not appropriate for the majority of scenarios dealing with normal evolution and possible emergencies, as the direct impacts do not exceed relevant regulatory limits. The paper provides qualitative and quantitative estimates for seven risk types and stresses the relevance of each (TCR routine operation under standard water-level conditions, Techa river remediation, TCR impacts from other facilities, V-11 overflow followed by uncontrolled massive environmental contamination, fall in TCR water level causing wind-blown entrainment of radioactive substances, risks associated with tornado and manmade accidents). The article suggests an innovative forecast technique based on the integrated hazard index assessment. It enables quantitative forecast of TCR evolution dynamics during the whole period associated with its potential hazard in the context of different strategies aimed at reaching TCR final state. The paper overviews the options aimed at reaching the acceptable risk level within the next 30 years.