Approach to testing reliability of nuclear power plant safety systems

The reliability of the safety system of a nuclear power plant is evaluated with regard to its availability and functional reliability. Subjected to reliability analysis is both the equipment and the automatic control system of emergency core cooling. Two separate failure trees were constructed for the investigated system for model failures of accident supply and for a failure of the function of the high pressure pump. The calculations show that the reliability of the control unit of the emergency core cooling system is incomparably higher than the reliability of technology. The calculated value of unavailability of the automatic control system is by several orders lower. (J.C.)