Safety provisions during operation of NPPs with fast reactors in the USSR

Specific features of sodium-cooled fast reactors operation and the NPP safety issues related to such reactors are considered. The data characterizing the operation of the BR-5(10), BOR-60, BN-350 and BN-600 reactors and radiation conditions realted to them are given. The total time of fast reactor operation in the USSR exceeds 50 reactor-years. The analysis of their performance shows that most of failures falls on the rhird circuit. These are various seal failures in the steam and water pipe-lines and fittings, troubles in water treatment systems failure of accessories wrong fits of safety valves faulty spare units, failure of instruments. The most specific troubles in the sodium circuits by for less numerous as compared with the third circuit) are connected with damage to the electrical heating system and with minor sodium leaks. It is concluded that the dynamic characteristics of the reactor core and primary coolant circuit of fast sodium-cooled reactor contribute to the NPP greater safety than when running water-water thermal reactors. The greatest hazard might arise in case of accidents due to the radioactive sodium leaks into the working boxes and suhsequent sodium combustion