Key principles
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Current second and third generation PWRs​.
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IRESNE is tasked with helping meet the needs expressed by its industry partners, mainly EDF and Framatome. IRESNE is involved in the fields in which it has built up expertise and capitalised on its knowledge and experience, i.e.: behaviour of nuclear fuel and fuel assemblies, reactor core physics, behaviour of components and systems, and nuclear safety which includes severe accidents.​

What is a second generation reactor?
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These reactors were commissioned in the early seventies through to the late nineties and represent most of the reactors currently operating worldwide. These reactors boast a level of nuclear safety that meets the initial requirements applicable at the time of construction, which has since been consolidated with each 10-yearly inspection outage and continuous improvements thanks to the integration of operating experience (OPEX). In France, the second generation is composed of pressurised water reactors (PWR) which are operated by EDF.

Third generation reactors - enhanced nuclear safety
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The probability of core meltdown has been reduced by a factor of 10.


The third generation of reactors have been dubbed “evolutionary”; their design is relatively similar to that of the second generation but with more demanding safety requirements (listed in ASN Guidelines No. 22 in France).

One of the most significant developments is the integration of severe accidents into the reactor design and the factor-10 reduction of the probability of core meltdown compared with the second generation.


The European Pressurised Reactor - EPR
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France chose the European Pressurised Reactor (EPR) for its third generation of reactors.


This 1600 MWe reactor boasts the following improvements:


  • A better power conversion efficiency.
  • Four physically separate redundant safety systems for improved nuclear safety.
  • Consolidated physical protective systems (double concrete containment, corium catcher to protect the base​mat).
  • A longer service life.
  • Better availability (>90%) with the possibility of carrying out maintenance with the reactor in operation.


Learn about IRESNE research on current second and third generation pressurised water reactors.