An ongoing quality audit at the Le Creusot forge has identified "irregularities" in paperwork on some 400 plant components produced there since 1965. The issues "comprise inconsistencies, modifications or omissions in the production files, concerning manufacturing parameters and test results".
Following questions over quality control and carbon content of steel in the reactor pressure vessel of the EPR under construction at Flamanville, France, Areva announced in April 2015 that it would conduct additional studies on the quality of forged components and the quality processes at its Le Creusot facility in Burgundy. The company said the review would help it identify the causes of potential defects in practices and in quality inspection, "as well as the measures to take to continue the improvements made since purchasing the forge in 2006".
The upper and bottom head of the reactor pressure vessel for the Flamanville EPR were manufactured at the Le Creusot facility in September 2006 and January 2007, respectively. A subsequent change in regulations concerning carbon content of steel was applied to them and last April Areva informed the ASN that chemical and mechanical tests conducted in late 2014 on a vessel head similar to that of the Flamanville EPR had revealed an area with carbon concentration beyond the new limits. This, ASN said, has led to "lower than expected mechanical toughness values".
Areva submitted its conclusions from this review to the French nuclear regulator, the ASN (Autorité de Sûreté Nucléaire), in October 2015.
However, the ASN said it "considered that this relatively superficial review - which only went back as far as 2010 - was insufficient and did not give a complete picture of the organization and practices at Creusot Forge, the quality of the parts produced and the safety culture prevailing within the plant". At the end of 2015, ASN requested Areva take the review process back to at least 2004, which was when the first parts intended for the EPR were manufactured.
Areva informed the ASN on 26 April of the preliminary results of the additional analysis. The company told the regulator that the review had identified irregularities in the manufacturing checks on about 400 parts produced at the Le Creusot facility since 1965. About 50 of these parts are thought to be in service at French nuclear power plants, it said.
The ASN said, "These irregularities comprise inconsistencies, modifications or omissions in the production files, concerning manufacturing parameters and test results." It has asked Areva to provide a list of the parts concerned as soon as possible, "along with its assessment of the consequences for the safety of the facilities, jointly with the licensees concerned".
"The review process will need to be seen through to completion in order to assess all the anomalies which may have affected past manufacturing operations and draw any relevant conclusions regarding the safety of the facilities," ASN said.
A process for informing and consulting with ASN is being implemented, Areva said. "In order to characterize the findings, a technical committee has been set up in connection with EDF," it said. "At this preliminary stage, no information has come to light that would jeopardize the mechanical integrity of the parts."
Areva said it would provide ASN with a status report on the quality audit before the end of this month.
Areva's Creusot Forge and Creusot Mécanique subsidiaries are specialized in the supply of big forgings and castings destined mainly for the nuclear industry. Creusot Forge is one of a few facilities that can produce the heavy nuclear-grade forgings required for large components such as steam generators, reactor pressure vessels and primary pumps. Creusot Mécanique, meanwhile, carries out precision finish machining on large components.
Researched and written
by World Nuclear News