European Nuclear Society
e-news Issue 35 Winter 2012
http://www.euronuclear.org/e-news/e-news-35/bns.htm

Belgian Nuclear Society organises a conference entitled:  «The long-term operation of Nuclear Power Plants: Life beyond 40 years »

Conference summary and conclusions

Long-term operation (LTO) is becoming more and more a routine procedure in nuclear countries and it is expected that the life of a vast majority of nuclear power plants will be extended. Regulatory frameworks, guidelines and processes are converging more and more, but peculiarities still exist from country to country, particularly with regards to environmental impact assessment, R& D evaluations, design

upgrades, competences & knowledge management. A broad-ranging analysis of the subject of the long-term operation of nuclear power plants was the topic under the debating spotlight during a conference entitled: The long-term operation of Nuclear Power Plants: Life beyond 40 years, which was organised, on 27 October 2011, in Doel, by the Belgian Nuclear Society.

During the conference Frederik Van Wonterghem, from the Federal Agency for Nuclear Control (FANC), gave a presentation in which he outlined how the Belgian national authority has clearly defined the Regulatory Framework and its expectations. This helped Electrabel, the nuclear power plant operator, to understand what he had to do to build its “Safety Case.”  Geert Backaert, of Electrabel, explained the comprehensive approach and methodology that was adopted to structurally address the FANC’s requirements and expectations, and stated that it will soon be detailed in a paper that will include the proposed Design Upgrade plan.

On a more technical level, delegates explored the issue of reactor vessel embrittlement. Rachid Chaouadi illustrated how R& D carried out at SCK-CEN has encouraged a better understanding of the actual mechanisms and influencing parameters relating to embrittlement. It has also helped to refine modelling techniques and promote enhanced surveillance strategy. The main conclusion reached was that irradiation embrittlement is a phenomenon that is now well under control and that the life extension of reactor vessels to 50 or 60 years is perfectly feasible and safe.

Participants in the conference were informed by Michel De Smet, of Tractebel Engineering, about “time limited ageing analysis” and, more specifically, about metal fatigue. One important change in this regard occurred recently in the regulations applicable in the US, namely relating to environmental effects and why it appears that the actual number of transients is, most of the time, lower than predicted at design stage. This new rule challenges older accepted calculations and requires the refining of modelling and calculation techniques. However, exactly how relevant consideration of this environmental effect is remains under discussion.

Finally, André de Jong, from the Borssele NPP in the Netherlands, gave conference delegates a presentation of the journey that they have followed to 60 years of operation, as well as of their Safety Case. The latter is quite close to the Belgian one, but has some specific additions. Similar technical issues face both the Netherlands and Belgium when it comes to meeting the challenge of extending the life of nuclear power plants.

As a conclusion, we may say that although more and more a well known process, LTO is still far from being harmonized. In general, there are no major technical concerns identified that could impair life extension. Also, significant design upgrades and investment might be required. One thing for sure is that such a Safety Case requires a major effort from the licensees. Let’s hope it will not be useless in Belgium.

Jean Van Vyve – Conference Chairman

© European Nuclear Society, 2012