Welding of the Main Components of Pressurized Water Recator Nuclear Power Plants

The basic materials used to make up the components of pressurized water nuclear power plants (PWR) have been defined to guarantee the perfect integrity of high-temperature pressure vessels for several decades. The grades of these low-alloy steel materials have been optimized so that they can be shaped and welded. In France and in all other countries, nuclear installations are subject to specific regulations, which are constantly being tightened in line with experience feedback. The decree of February 26, 1974 for the main circuit of nuclear power plants, which imposed formal rules on manufacturing, inspection and quality organization, has been replaced by the decree of December 12, 2005 (known as the ESPN decree) which, while retaining the essence of the 1974 decree, reinforces design requirements, particularly in terms of risk analysis. Grades and processes have been codified in the RCC-M (Règles de conception et de construction applicables aux matériels mécaniques) (Design and construction rules applicable to mechanical equipment) in line with the regulations. In addition, special welding precautions were defined for all welding processes, taking into account the specific characteristics of the base materials and filler materials, in order to meet contractual and regulatory requirements and, more generally, the expected level of quality. These precautions, which were originally based on the industrial experience of pressure vessel manufacturers, have been constantly improved on the basis of feedback from the manufacture of nuclear power plants, and supplemented by an exhaustive risk analysis process required by the ESPN decree of December 2005.

Safety-critical components in pressurized water nuclear power plants involving welding operations are not limited to nuclear pressure equipment. In fact, safety-critical civil engineering structures such as reactor building liners and swimming pools also include numerous welded metal components. Here, too, practices (grades used, welding precautions, checks, etc.) have been optimized in the light of experience feedback, and have been codified for the EPR in an ETCC compendium (EPR Technical code for civil work) ...