The European pressurized water reactor, a safe and competitive solution for future energy needs

Full text: 1. EPR Design Philosophy. The EPR design philosophy is governed by three essential targets: Improving the safety level compared to existing plants by deterministic and probabilistic considerations; Mitigating of hypothetical severe accidents by restricting their consequences to the plant itself; Providing economic power generation at costs competitive with other primary energy sources. The economic requirements have led to a large electrical output of about 1,600 MW, with which the EPR will reach outstanding specific investment costs. Operation costs are reduced by a high average fuel burn-up. The design allows for cycle lengths between 12 and 24 months. An average availability target for the design has been set at 92 % over the whole 60 year lifetime of the plant. Therefore, preventive maintenance features are incorporated in the design to optimize outage durations. 2. Safety Approach. A twofold strategy is pursued for the EPR safety requirements: To improve the preventive measures against accidents; To mitigate Severe Accidents consequences, even if their probability has been further reduced. This is achieved by implementing features to ensure containment integrity. Thus, it can be demonstrated that the need of stringent countermeasures are restricted to the immediate vicinity of the plant. The safety approach includes a strong deterministic basic complemented by probabilistic analyses in order to improve the prevention of accidents, as well as their mitigation. Accident Prevention measures are enforced by: Simplification of the safety systems; Elimination of common mode failures by physical separation and diverse back-up functions for safety functions; Increase of grace periods for operator actions by designing components (e.g. pressurizer and steam generators) with larger water inventories to moderate transients; Less sensitivity to human errors by an optimized man-machine interface by digital instrumentation and control systems and information supplied by modern operator information systems. Low probability events with multiple failures and coincident occurrences up to the total loss of safety grade systems are considered in addition to the deterministic design basis. Representative scenarios are defined for both, core melt prevention and the prevention of large releases. 3. Technical Features. The Reactor Building is located in the center of the plot plan. The Containment is surrounded by the Safeguard Buildings and the Fuel Building, which contain the safety systems. All safety systems are designed in a four-fold redundancy and located in physically separate divisions. Each division comprises a Low Head Safety Injection/Residual Heat Removal System with the related intermediate cooling system, a Medium Head Injection System and an Emergency Feedwater System. The related electrical systems as well as the instrumentation and control systems are also allocated in these divisions but on a higher building level. The inner Containment is constituted by a pre-stressed concrete cylindrical wall with elliptical head and a reinforced concrete basemat. The leak tightness is assured by a metallic liner. The outer Containment is formed by a reinforced cylindrical wall, resting on the same basemat, and covered by a reinforced concrete dome which serves as protection against external hazards (airplane crash). Since the Severe Accident Mitigation approach imposes special requirements on the Confinement function of the Containment, systems for isolation, retention and control of leakages are proved. Leakages through the inner Containment wall are collected, filtered and released via the Annulus Air Extraction System. Conclusion.The EPR with its innovative design features will be the trendsetter for the future of nuclear power plant engineering, the strong support of important entities and organizations of the European nuclear industry ensure a serious and reliable approach for the realization of nuclear power plant projects with EPR technology. On the 18th of December 2003 the first EPR was ordered by TVO, Finland. (author)