The Approach of Strengthening Safety and Improving Availability of a NPP through Dependability Management Method

Taking into account the importance of the continuous improvement of the performance and reliability of a NPP and practical measures to strengthen nuclear safety and security, it is to be noted that a good management for a nuclear power reactor involves a \"good dependability management\" of the activities, such as: Reliability, Availability, Maintainability (RAM) and maintenance support. The document ISO 9000-4/IEC 300–1“Dependability Management”, describes five different agreed dependability indicators of the nuclear reactor equipment. In order to evaluate certain safety assessment criteria intended to be applied at the level of the nuclear reactor unit management, equipment dependability indicators and their impact over the availability and reactor safety have to be evaluated. Reactor equipment dependability indicators provide a quantitative indication of equipment RAM performances (Reliability, Availability and Maintenance). One of the important benefits of maintenance and failure data gathering is that can be used as a support of probabilistic safety assessment (PSA). Also, a good dependability management implementation may be used to complement reactor level unit performance indicators in the field of safe operation, maintenance and improving of operating parameters, as well as for Strengthening Safety and Improving Reliability of a NPP. The evaluation of those 5 reactor equipment dependability indicators (I1÷I5 ) offer a valuable managerial tool at the reactor level and for certain safety and security criteria to be taken into consideration for the top management of the NPP. It is important to remark that the most valuable dependability data are for items which have a significant effect on safety & security and data need only to be analysed for dominant equipment. The work presents a practical evaluation of those above mentioned dependability indicators referring, as an example, for the primary circuit of a NPP CANDU type reactor unit. The paper underlines the importance of nuclear safety and security as prerequisites for nuclear power. Also, different technical aspects through implementation of a good dependability management will contribute to a strengthen safety and an improvement of Availability of the NPP through dependability indicators determination and evaluation.