Electrical and I&C systems
The electrical and instrumentation and control (I&C) systems are central elements of a nuclear power plant. The function of I&C is to register and process all process variables and plant parameters that are necessary to monitor, regulate and control the processes in a nuclear power plant. The main safety-relevant part of I&C is the reactor protection system. The reactor protection system continuously monitors important plant parameters and, if needed, triggers automatic measures to mitigate or prevent the consequences of accidents. In case of abnormal operation, first of all the limitation system is activated to avoid triggering of measures by the reactor protection system.
The electrical equipment includes, besides systems and components used for power supply (e.g. unit generators, transformers), a variety of safety-relevant devices, such as emergency power generators, batteries, drives for pumps and valves for the shutdown of the reactor, for core cooling or for cooling of the fuel pool.
Safety through redundant systems
Reliable electrical and I&C systems and components are of paramount importance in nuclear power plants. Their failure could not only mean interruption of operation, but also the failure of safety-relevant protective measures. To prevent this, all safety-relevant systems have to be installed several times, i.e. redundantly, so that a single failure and repair cannot prevent the performance of the required safety function. In addition, systems and components have to be designed such that a systematic failure that may have an impact on several redundant systems and components at the same time can either be excluded or controlled. If systematic failure of these systems and components cannot be excluded, the design of the redundants should provide for diversity, i.e. different manufactures, types, or the like, should be used.
Digital and hard wired I&C systems
In the last decade, there has been a change in technology from hard-wired to digital, software-based I&C systems . While the operational I&C systems and the limitation system in nuclear power plants have been partially converted to software-based I&C systems, questions arise with regard to the modification of the reactor protection system that are discussed very controversially in Germany but also at the international level. GRS is very much involved in these discussions.
Tasks and solutions of GRS in the field of electrical and I&C systems
GRS supports the Federal Environment Ministry (BMU) within the framework of federal oversight. GRS participates in the creation of an assessment basis for the reliability of modern electrical and I&C systems and components in accordance with the state of the art in science and technology. GRS addresses all safety-relevant issues of conventional and new, software-based electrical and I&C systems and components. The main fields of work are:
• Evaluation of German reportable events relating to electrical and I&C systems
• Evaluation of international IRS (Incident Reporting System) reports
• Evaluation of operating experience with electrical and I&C systems below the reporting threshold
• Development of models for assessing the reliability of software-based I&C systems
• Assessment of concepts for new I&C systems
• Monitoring of the developments of electrical and I&C systems in the non-nuclear sector
Due to its wide range of competence in the field of nuclear safety, GRS also has interdisciplinary knowledge regarding the interfaces to process engineering, system reliability and many other disciplines. GRS participates in the national technical commissions RSK, KTA and VdTÜV.
GRS is committed to the further development of the international rules regulations also in its field of competence “electrical and I&C systems”. GRS participates in international committees and organisations, as for example the International Atomic Energy Agency (IAEA), and in programmes of the European Commission. In addition, GRS works in the field of electrical and I&C systems for foreign regulatory authorities.