(Adds detail from ASN letters, EDF replies)
PARIS, March 31 (Reuters) - French nuclear regulator ASN on Friday published extracts of a decade's worth of correspondence in which it raised safety concerns about Areva's nuclear foundry Creusot Forge.
Commercial production at the foundry has been halted since late 2016 after ASN discovered manufacturing flaws and forgery of tracking documentation. Two of state utility EDF's reactors have been halted for months following the discovery of problems with components manufactured by Creusot Forge.
The publication follows a report by radio station France Inter which said EDF and its supplier Areva had allowed Creusot Forge to manufacture the base and cover for the reactor vessel in Flamanville, despite ASN's warnings.
In the first of several documents published by ASN on Friday, a Dec. 12, 2005, letter to EDF highlights manufacturing problems at the foundry which the regulator said raised questions about the quality of its work. It also urged EDF to closely monitor safety rules there. Some of that documentation had been published earlier on ASN's website.
Despite several more warnings in following years, Creusot Forge manufactured the Flamanville parts, which were installed in the reactor in 2014. In 2015, Areva finally discovered that there was a problem with excessive carbon concentrations in the components. Such concentrations can weaken steel.
The ASN now needs to rule on whether the reactor - which is due to be completed late next year - could function safely despite these weak spots. The ASN on Friday said it would rule on the issue "this summer", pushing back an earlier deadline for a ruling by mid-2007.
EDF head of new nuclear Xavier Ursat told Reuters on Thursday he was confident ASN would declare the Flamanville reactor safe.
Getting the ASN's green light is crucial for EDF, because a negative ruling would mean years of more delay and billions of extra costs for the reactor. It would also scupper EDF's planned takeover of the reactor unit of Areva, as a clean bill of health for Flamanville 3 was a condition for the deal.
Areva is being restructured and recapitalised by the French state after years of losses wiped out its equity.
Following an early 2006 visit to the foundry, the regulator described numerous anomalies at the Creusot site and again urged EDF and Areva to better oversee the plant.
EDF answered in August 2006 that corrective action had been taken, but ASN said a month later that EDF's responses were not satisfactory.
ASN said that in 2012 its director had spoken to Creusot Forge staff about the need to improve its safety culture. Following a new inspection in October 2012, the regulator again warned in writing about quality issues and the need for the foundry to update its skills.
Two years lager, Areva sent its first warnings to the ASN about unsatisfactory resilience tests on the Flamanville components. (Reporting by Geert De Clercq; Editing by Andrew Callus and Mark Potter)