European Pressurized Reactor - Design

Design

The main design objectives of the generation III EPR design are increased safety while providing enhanced economic competitiveness through improvements to previous PWR designs scaled up to an electrical power output of around 1650 MWe (net) with thermal power 4500 MWt. The reactor can use 5% enriched uranium oxide fuel, reprocessed uranium fuel and 100% mixed uranium plutonium oxide fuel. The EPR is the evolutionary descendant of the Framatome N4 and Siemens Power Generation Division KONVOI reactors.

The EPR design has several active and passive protection measures against accidents:

• Four independent emergency cooling systems, providing the required cooling of the decay heat that continues for 1 to 3 years after the reactor's initial shutdown (i.e. 300% redundancy)
• Leaktight containment around the reactor
• An extra container and cooling area if a molten core manages to escape the reactor (see containment building)
• Two-layer concrete wall with total thickness 2.6 meters, designed to withstand impact by aeroplanes and internal overpressure

The EPR has a design maximum core damage frequency of 6.1 × 10−7 per plant per year.

The Union of Concerned Scientists has referred to the EPR as the only new reactor design under consideration in the United States that "...appears to have the potential to be significantly safer and more secure against attack than today's reactors."

On November 4th 2009, the nuclear power regulatory authorities in France, Finland and the United Kingdom issued a joint letter to Areva, citing serious problems with the EPR's digital Instrumentation and Control systems (I&C). The letter stated:

"The issue is primarily around ensuring the adequacy of the safety systems (those used to maintain control of the plant if it goes outside normal conditions), and their independence from the control systems (those used to operate the plant under normal conditions).

Independence is important because, if a safety system provides protection against the failure of a control system, then they should not fail together. The EPR design, as originally proposed by the licensees and the manufacturer, AREVA, doesn’t comply with the independence principle, as there is a very high degree of complex interconnectivity between the control and safety systems."