Safety of sodium-cooled fast reactors

Conclusions The accumulated experience in the operation of NPP, including those with fast reactors, shows that during normal operation, with due regard for possible operational difficulties and accidents, they ensure a significantly lower level of risk for personnel and the surrounding population than is present in industrial regions and those prone to natural disasters. Therefore, the dangers connected with the widespread development of nuclear power arise not so much from a real risk as from a risk which in principle can be realized in very improbable accidents. From this point of view sodium-cooled fast reactors have certain advantages. The probability of the maximum accident of the rupture of pipelines in high-pressure reactors must be considerably higher. Here a single event, and one difficult to detect, such as the failure to detect a flaw in manufacture, is enough to initiate the very dangerous first step of an accident. The rupture of equipment in the primary loop of a fast reactor at practically atmospheric pressure is considerably less probable, and the integral assembly is quite safe. All the other chains of development of maximum accidents in a fast reactor require the simultaneous realization of several events in systems and devices which are constantly being monitored (SS and power supply systems, etc.). The above considerations together with such important properties of sodium as the large reserve before the boiling point and the practically inertialess transport of heat from the reactor to structural elements and heat-transfer devices under natural circulation conditions gives one confidence that the level of risk for future industrial NPP with fast reactors will be at least no higher than that for NPP with thermal reactors.