EPR Reactor: Information Letter n°7: Progress in ASN inspections of construction activities

During the second half of 2009, ASN continued its inspection activities on the Flamanville 3 EPR construction site.

Treatment of construction joints

During inspections carried out in 2009, ASN inspectors noted on several occasions construction joints[1] displaying inadequate surface roughness. Furthermore, during an inspection on 26 August 2009, ASN and IRSN observed the use of a chemical which was not specifically designed for treating construction joints.

Following this inspection, ASN asked EDF to stop using this product and to make an inventory of all the methods used for treating construction joints on the Flamanville 3 site. ASN also asked EDF to analyse the consequences of the use of this chemical in the areas concerned.

At the same time, the Authority asked for a comprehensive qualification procedure to be carried out on all the methods used for treating construction joints on the Flamanville 3 site. EDF is currently studying these points.

Deviations from civil works design and construction rules

Design and construction rules for civil works on the Flamanville 3 EPR are set out in a document known as ETC-C[2], which was closely analysed by ASN and its technical support organisation, IRSN, during the examination of the Flamanville 3 licence application. These rules are prepared by companies in the nuclear industry, based on standard practice and applicable standards in other activity sectors. They also draw on the experience acquired during the construction of earlier nuclear power plants in France and Germany.

Deviations from specific ETC-C rules must be fully justified and compensatory measures taken to guarantee the same degree of safety.

During inspections of the construction site and EDF central services, ASN observed many deviations from the design and constructions rules for the civil works on the EPR. In light of these inspections, ASN considers that the identification and justification of such deviations should be more rigorous. ASN also asked EDF to check that all deviations from ETC-C had been correctly identified.

Inspection of manufacturing processes for reactor coolant system and secondary system components

During manufacturing inspections of nuclear pressure equipment at the manufacturer AREVA NP's site and at those of its suppliers and their subcontractors, various deviations were observed, many of which are induced by the complexity of the manufacturers' declared reference base. ASN ensures that suitable corrective action is taken for each case.

As part of these activities, ASN has examined a number of cases concerning the design and manufacture of EPR reactor coolant and secondary system components (reactor vessel, reactor coolant pumps, control rod drive mechanisms, pressuriser, steam generators, piping and valves).

At the end of 2009, ASN reached a decision on the corrective action proposed by AREVA NP concerning a manufacturing defect found on a steam generator component. Based on the results of the requested tests and completed inspections, it was decided to accept the AREVA NP proposal to replace the defective component by another which had already been manufactured, but did not present exactly the same characteristics.

During its review inspection of AREVA NP nuclear pressure equipment manufacturing activities, ASN observed that key production quality assurance procedures were satisfactory, but noted that the various tasks of those responsible for quality needed to be made clearer. ASN asked AREVA NP to make improvements in decision-making procedures and supplier approval and monitoring, and to move forward in the area of regulatory documentation.

International relations

ASN is in regular contact with foreign nuclear safety authorities to discuss inspection issues regarding EPR construction. These discussions focus on site work, factory-manufactured components and the examination of detailed reactor design.

In September, two inspectors from STUK, the Finnish Nuclear Safety Authority, carried out a cross-inspection of the Flamanville 3 site. In October, two inspectors from NRC, the US Nuclear Regulatory Commission, came to ASN for a week of intensive training and took part in a cross-inspection. Lastly, an inspector from ENSI, the Swiss Federal Nuclear Safety Inspectorate, took part in an onsite cross-inspection of organisational and human factors. In all these cases, the visits gave inspectors an opportunity to discuss reactor design and construction site methods employed by the operator and to compare inspection practices.

Bilateral relations between ASN and NRC also saw the two organisations set up an exchange of personnel for carrying out manufacturing inspections on nuclear pressure equipment. An NRC inspector is also working at the ASN Nuclear Pressure Equipment Department.

Labour inspection in 2009

In connection with workplace inspections in 2009, the ASN labour inspector responsible for the Flamanville 3 site took steps to address a number of issues, in particular the significant increase in the number of workers on the site and the diversification of construction activities carried out there, which induces a wider range of potential hazards.

In particular, the labour inspector, along with the relevant government departments, ensured that labour regulations concerning the secondment of foreign workers and the safety of workers on site were observed. In view of inspection results in 2009 and other information brought to the labour inspector's attention, ASN intends to give closer attention in 2010 to the observance of regulations on working hours and on site safety, with a special focus on chemical hazards and falls from heights.

[1] A construction joint is the area of contact between two layers of concrete placed at different times. Construction joint surfaces must be treated, generally by mechanical means, to provide a sufficient degree of adhesion between the two layers.

[2] EPR Technical Code for Civil Works: design and construction rules for civil works on the EPR.