IRSN, Institut de radioprotection et de sûreté nucléaire

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Enhancing Nuclear Safety

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Preparing the fourth generation of nuclear reactors

At the December 20th, 2006 meeting of the Council of Ministers, the ministers in charge of research and industry gave a presentation on the fourth generation (GEN-IV) of nuclear reactors.

In the words of the press release, "France has decided to commit herself to participate in the design of the fourth generation of nuclear reactors, the industrialisation of which may be considered as starting from the year 2040. The industrial design of these reactors must satisfy several requirements, fixed by the Government, relative to the third generation (GEN-III) reactors :

                      - reducing the volume and radiotoxicity of wastes;
                      - producing the same quantity of energy using a lower amount of uranium,
                      - further improving the safety and security of reactors;
                      - mastering the risks for proliferation.

… (The research to be performed over the coming years) will focus on the sodium - or gas-cooled - fast reactor concepts …

A milestone has been set for 2012 to decide on the technological choices from among the different technological options and to undertake the construction in France of a prototype of a GEN-IV reactor, with the objective to starting it up in 2020, in accordance with the decision taken by the President of France in January 2006".


It is part to the IRSN to give technical advice on the protection of persons, property and the environment and to carry-out research programmes aimed at maintaining and developing the knowledge which is necessary for the expertise of industrial projects in the fields of nuclear security in its widest meaning (safety, radiological protection, non-proliferation, resistance to acts of malicious damage).

In this framework, the IRSN has set up an internal brainstorming on the new safety, radiological protection and security-related problems affecting the six reactor concepts selected, at the international level, by the “Generation IV International Forum (GIF)” created in 2000 at the initiative of the American Department Of Energy (DOE). This think-tank, which started in 2004-2005, was upgraded, following the announcement by the President of France in early 2006, to engage the country in the construction of a GEN-IV prototype by 2020. In addition to power reactor concepts, the IRSN's analysis has been extended to the associated fuel cycles.

Taking into account the government orientations, the IRSN decided to put forward the present state of its thinking on the safety concern on the six reactor concepts mentioned above, it being understood that the subsequent work of the Institute would have as main concern and focus on the fast reactor safety. The high temperature and very high temperature reactors not retained, due to their "open" cycle (with no demonstrated industrial capability for recycling of actinides), will for their part be the subject of an active watch in liaison with industry interested in their development.

The fast reactors so far selected belong to two different types : 

  • The sodium-cooled fast reactors : this concept has already been worked up to industrial scale in France with Rapsodie and Phénix as well as the Creys-Malville power plant; later projects (RNR 1500, EFR) underwent preliminary analysis either in a formal national framework (RNR 1500) or within an international informal framework (EFR). It is straightforward that some improvements of the concept, likely relevant ones, will be proposed by the designers with the aim of improving its competitiveness, safety, security and waste management performance;
  • The gas-cooled reactors : this concept has not yet been worked on either in France or abroad. Its selection in the framework of GIF is linked to its features for actinide transmutation of and to its high thermodynamic efficiency (the target temperatures allow considering the production of heat for industrial processes). Future developments of the concept require the construction of an experimental reactor for testing (the actual REDT project of the French Atomic Energy Commission - CEA - is a 50 MW th reactor, the decision for construction, if any, may not be taken by 2012).

Concerning the sodium cooled fast reactors, the text herewith attached emphasizes several safety issues, which require in-depth examination between now and 2012. The main concerns are presently the features of the reactor core as well as its behaviour in both incidental and accidental situations, in relation to the choice of cooling devices, and the in-service monitoring of the various components (internal structures, steam generators). It is straightforward that the design improvements proposed by the designers should, in due time, be the subject of in-depth discussions (e.g. giving the intermediate sodium circuits up). Nevertheless, the actual state of knowledge appears sufficient for a brainstorming to be launched in 2007 on the main safety issues to be addressed for an industrial size reactor, as it has been done for the 3rd PWR reactor generation at the end of the 1980s (the studies, conducted jointly by IPSN (The IPSN (Institut de Protection et de Sûreté Nucléaire) became the IRSN in 2002) and GRS, led, in mid-1993, to a common statement by the French and German Safety Authorities on the safety objectives to be searched for the EPR reactor project). The proposed think-tank will take into account the results of the analysis carried-out for the RNR 1500 and EPR projects. It will include discussions with other expertise assessment bodies at the international level. Moreover, it will contribute to the definition of the main axes for the research and development in support of the expertise of such concept. It is worth stressing that, if experiments in "large" research facility are to be carried-out, they should be defined and scheduled in large advance in order to match the 2020 milestone.

Concerning the gas-cooled fast reactors, the concept design is not achieved enough, even as regards the demonstrator, to adopt a similar approach in the same time-frame. It is recommended the designers to perform preliminary feasibility studies with particular attention to the safety questions already identified (the main concern being the core cooling in accidental situations).

In the meantime, the IRSN will also conduct a brainstorming on security-related issues (non-proliferation and protection against acts of malicious damage) for both concepts; these problems must be stressed from the very beginning of the design phase in order that the overall plant design accounts for all the nuclear security-related aspects.

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