Until the end of 2005, the construction of PWR pressure vessels containing radioactive fluids was regulated by the order of 26 February 1974 and basic safety rule II.3.8 for the main primary and secondary systems and the decrees of 1926 and 1943 for the others (see chapter 3 point 2.2.1). Responsibility for the construction, covering design, industrial manufacture and on-site installation lies with the manufacturer (Framatome ANP or EDF). It is up to the manufacturer to demonstrate the conformity of the equipment it designs. It chooses the manufacturing processes, the checks to be used and the acceptance criteria for the results of these checks. To do this, it usually relies on industrial codes, some of which may be specific to the nuclear industry, in particular the RCC-M code (see chapter 3 point 2.2.3). It is also up to the manufacturer to supervise its suppliers and subcontractors.

Throughout this process, the ASN checks that the manufacturer complies with the regulations and correctly carries out the tasks under its responsibility.

This construction supervision takes place:

• during design, on the basis of the justification files provided by the contractor. These files describe the equipment and its components, the loads to which they are subjected in normal operation or would be subjected to in an accident situation, their mechanical behaviour in response to these loads, the characteristics of the materials used, the manufacturing processes and their supervision;
• during manufacture/installation: on the one hand prior to the beginning of these operations, based on documents describing the technical options adopted by the contractor, and on the other hand during execution, via checks in the field and in the factory, to ensure compliance with the stipulations of the files concerning equipment dimensions, materials used, manufacturing processes employed and their qualification, the supervision carried out and its results. It ends with hydrostatic testing. The ASN is responsible for overseeing the hydrostatic test, which is the final full-scale strength and tightness test, decides on its outcome and issues the test report, without which no pressurised equipment can be brought into service.

This process is specific to France, even if in other countries the differences are minimal. For pressurised equipment which is not designed to contain radioactive fluids, there is a European directive which harmonises construction and inspection practices. While maintaining the responsibility of the manufacturer, the directive stipulates essential safety requirements for which compliance must be checked by one of the independent organisations notified by the Member States.

With a view to improving safety, while incorporating the technical advances of the directive, the ASN has prepared a new regulatory text. For nuclear pressure vessels, it specifies construction rules and inspection procedures similar to those of the European directive, but which are supplemented to take account of specifically nuclear aspects. This text, an order of 12 December 2005, will apply as of 2006 to the construction of nuclear pressure vessels, in particular those intended for the EPR reactor, should it be built (see point 2.4).