SAFETY OF UKRAINE’S NUCLEAR POWER INDUSTRY IN EXTREME OPERATING CONDITIONS

Abstract

An urgent issue of the state (level) of safety of Ukraine’s nuclear power industry in extreme conditions is the situation of the Zaporizhzhia NPP, the largest in Europe, due to the station’s location in the war zone and difficulties in its management and operation, as well as the safety regulation of the station in the occupied territory. In the proposed article, the possibility of Zaporizhia NPP industrial site flooding is analyzed from the elaborated hydrodynamic model and justifying calculation; the conditions of ZNPP industrial site possible flooding are determined depending on the warhead power producing a corresponding destructive effect. Probabilistic approaches to assessing the Zaporizhia NPP safety objective state (level) in extreme conditions are insufficiently justified taking into account the lessons of the largest nuclear and radiation accidents. On the basis of a deterministic approach, the conditions of Zaporizhia NPP industrial site critical flooding due to extreme military action are identified. Flooding of the plant’s industrial site may cause two initial emergency events: a complete long-term de-energization of power units and violation of heat exchange conditions in spent nuclear fuel dry storage facilities. Prevention of flooding of the Zaporizhia NPP industrial site can be based on the construction of protective flood barriers on the cooling pond coast. Prospective directions to increase the accident management efficiency related to the nuclear power units’ passive safety systems modernization and improvement of operational symptom-oriented emergency instructions/manuals for managing severe (nuclear) accidents have been identified. An effective accident management strategy with complete long-term de-energization of WWER power units can be based on a comprehensive modernization of emergency recharge systems of steam generators with steam driven pumps and natural circulation circuits of passive heat removal systems from the pressurized reactor unit.