Continued operation of 900 MWe nuclear power plants: ASN has issued its first review following the third ten-year inspection at the Fessenheim and Tricastin plants

In May 2009, Reactor 1 at the Tricastin nuclear power plant in the Drôme département was shut down for four months for the “third ten-year inspection”. Reactor 1 at the Fessenheim nuclear power plant in the Haut-Rhin département also underwent a similar outage in October 2009. These outages are a statutory requirement and are important in the decision-making process with regard to continued operation of a nuclear power plant. They are the first step in a series of inspections to ensure that the safety level of the French 900 MWe power plants is acceptable, and they take into account new statutory requirements and measures specific to reactors that are more than 30 years old.

Regulations concerning continued operation of a nuclear power plant

In France, the authorisation decree for building a nuclear reactor does not set a limit for service life. However, the Act on transparency and nuclear safety (TSN Act) requires the operator to reassess the safety of the facility every ten years.

This safety review is a thorough-going facility “health check". It provides an opportunity for in-depth verification of compliance with all safety requirements, for an assessment of whether aging has affected the reactor’s safety level, for modifications to the facility in order to further improve its safety level and finally for assessing the possibility of continuing to operate the facility until the time of the next safety review.

 Continuing operation of the 900 MWe reactors up to 40 years service life

In July 2009, the French Nuclear Safety Authority (ASN) issued its formal position with regard to the generic issues around continued operation of 900 MWe reactors. The authority did not find any evidence of compromise to EDF's ability to manage the safety of its 900 MWe reactors up to 40 years after their first criticality. However, this general assessment does not take into account the specific features of each reactor. The ASN’s generic position will therefore by supplemented by the checks carried out during the third ten-year inspection of each reactor and by an examination of the reactor safety review, leading to a position that will be taken for each reactor individually.

Process for the third safety reviews

 The safety review is a long-term process that started in 2002 for all the 900 MWe reactors. It features two parts:

• Examination of the technical documentation containing reports on all the 900 MWe reactors and specific reports for each reactor. The operator studies the safety level of its facility with regard to risks such as earthquakes, flooding, fire, explosion and aging and updates its accident studies;

• A ten-year inspection of each reactor: this outage provides an opportunity to carry out in-depth on-site inspections of the main equipment (pressure testing of reactor coolant system pipework and the concrete containment building, examination of the reactor vessel etc.), to perform specific maintenance tasks and to incorporate any equipment modifications identified in the technical reports.

 Approximately one year after the end of each ten-year inspection, the ASN issues its decision as to the continuance or otherwise of operations for each of the 900 MWe reactors, based on the inspections performed.

 Checks during the ten-year inspection of Reactor 1 at the Tricastin nuclear power plant

From 2 May to 30 August 2009, the ASN carried out checks during the third ten-year inspection of Reactor 1 at Tricastin nuclear power plant, the first reactor in France to undergo this inspection. In particular, the ASN supervised the requalification test of the Nuclear Steam Supply System on 19 June 2009.

Five inspections were also carried out by the ASN during this outage to check compliance with requirements concerning the reactor coolant system, the processing of non-destructive test results for safety-related equipment items and the operating technical specifications.

Following a review of the results of the inspections and work performed during the outage, the ASN allowed the restart of Reactor 1 on 20 August 2009.

In 2010, the ASN will issue the government with its opinion as to the continuance of operations at Tricastin Reactor 1 for a further ten years. If a favourable opinion is issued, the ASN may also lay down technical requirements concerning the provisions to be implemented in order to improve the safety level of the facility.

Checks during the ten-year inspection of Reactor 1 at the Fessenheim nuclear power plant

The ten-year inspection outage at Fessenheim 1 ran from 17 October 2009 to 24 March 2010. The operator used this outage to perform specific in-depth inspections of the facility and to undertake a major programme of facility modernisation. The ASN supervised the performance of this work and its associated checking.

In particular, the authority carried out 12 on-site inspections and attended the Nuclear Steam Supply System requalification test on 7 December 2009.

During its inspections, the ASN did not detect any significant deviations which could jeopardise reactor operation. On 26 February 2010 therefore, the ASN authorised the restart of the reactor.

In 2011, the ASN will issue the government with its opinion regarding continued operation of Fessenheim Reactor 1 for a further ten years. If a favourable opinion is issued, the ASN may also lay down technical requirements concerning the provisions to be implemented in order to improve the safety level of the facility.

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In general, restart of a reactor following any outage for scheduled maintenance or refuelling is subject to ASN authorisation. This procedure applies in particular to reactors undergoing their third ten-year inspection. Authorisation to restart the reactor does not prejudice the decision as to whether the reactor is fit to operate for the next 10 years.

The ASN carries out continuous supervision of facilities by means of on-site inspections and examination of technical documentation. If the ASN deems that a facility poses serious and imminent risks, it has the power, under the TSN Act, to suspend operations at the facility.

The ASN issues an authorisation in principle, based on the operator’s demonstration that the reactor is fit to be operated safely for a further 10 years. This authorisation may be issued for a period of less than 10 years. In addition, following one of its inspections during the authorised period, the ASN also has the power to reduce the operating period or to impose specific requirements with the aim of raising the safety level.