NPP operational reliability improvement based on the diversity principle
Automated Process Control Systems (APCS) of the power units under construction must be protected from common cause failures due to software errors. Protection from common cause failures in accordance with GOST R-IEС 60880-2011 can only be ensured by applying the diversity principle.
In the APCS design of the Novovoronezh NPP II-1, software and hardware complexes are used both in normal operation systems and in safety systems. At the same time, the initiating part of the reactor emergency and preventive protection subsystems based on the TELEPERM XS hardware and software is not immune from failures caused by possible errors in the software.
To exclude common cause failures of the control safety systems, the project provides for additional measures that eliminate failures of the safety systems due to the software failure.
Consideration is given to the problem description, basic directions of the diversity principle implementation to reduce the probability of equipment failures, evaluation of reliability indicators in accordance with the SSTC NRS recommendations as well as the description of the diverse protection system (DPS) and its structure. The structure of the DPS algorithm for controlling actuators is exemplified by the steam generator protection. The interaction scheme of normal and diverse protection systems is analyzed.
Based on the experience of using the DPS at the NvNPP II, conclusions are drawn about the practical implementation of the reactor plant protection system and the need to analyze the consequences of joint operation of the initiating part of the safety management system in terms of technological parameters and DPS with possible algorithm adjustments.
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