* Testing of Flamanville reactor cover insufficient - ASN
* Reactor cover currently not fit for permanent service
* Reactor cover may only be able to function a few years
* EDF willing to replace reactor cover at 10-year review
By Geert De Clercq
PARIS, June 26 (Reuters) - The cover of the reactor vessel EDF is building in Flamanville, France, may not be able to function more than a few years unless the utility can do additional tests which so far it has not be able to, nuclear regulator ASN said in a report.
While the long-awaited report, a copy of which was obtained by Reuters, concludes the European Pressurized Reactor (EPR) is fit for service, EDF may have to replace its vessel cover soon after its scheduled start-up in 2018.
The requirement is a major blow for EDF, which will have to start planning for a costly replacement of a key part before the reactor even starts up. The reputational damage could also add to concerns in Britain about its 18 billion pound ($23 billion) project to build two similar EPR reactors in southwest England.
The French regulator had ordered a deep review of the Flamanville vessel following the discovery in 2015 of carbon concentrations in the base and cover of the containment vessel, which make its steel more brittle.
The report - led by the IRSN, the ASN's technical arm - is being reviewed by a group of independent experts on Monday and Tuesday. This autumn, ASN will partly base its final ruling on Flamanville on the experts' recommendations.
The ASN report states that while the base of the vessel is fit for service despite the need for increased monitoring over its lifetime, manufacturer Areva NP has not been able to conduct sufficient tests on the cover as it is no longer accessible. These controls are indispensable in order to ensure the reactor's safety over its 60-year lifetime, the report says.
It adds that the technical dossier handed to the ASN by Areva NP and EDF about the follow-up controls is brief and gives no information about the feasibility of these tests.
"The (regulator) considers that the current cover of the Flamanville reactor is not fit for service in a permanent manner given the absence of sufficient non-destructive tests," the Autorité de sûreté nucléaire's (ASN) report says.
"Therefore, the (regulator) considers that the use of the current reactor cover of the Flamanville EPR cannot be envisaged beyond a few years of operation without the necessary controls ... having been put in place," it says.
The report adds EDF has committed to analyse, at the end of 2025, the conclusions of technical feasibility studies and new test procedures, and that in the event of negative conclusions, it will replace the cover during the reactor's first ten-year review.
ASN notes that covers of other EDF reactors have been replaced in past years.
It adds that, according to Areva NP, a cover could be replaced in less than 80 months, meaning a new cover "could be available before the end of 2024 if it is ordered in 2017".
Areva NP's Creusot Forge foundry, which made the base and cover, is currently closed following the discovery of manufacturing flaws and falsification of documentation and is awaiting ASN approval to restart.
BFM TV said on its website that EDF had been expecting ASN to ask it to replace the Flamanville reactor cover and it had already ordered the manufacturing of the new piece, with the replacement scheduled for 2021.
The ASN and EDF declined to comment.
The European Commission has said the ASN's green light for the Flamanville reactor vessel is a precondition for EU approval of the recapitalisation of Areva and the planned sale of its reactor division Areva NP to EDF.
In recent months, EDF has said several times that Flamanville will start up in 2018, six years behind schedule. Its cost was last estimated at 10.5 billion euros ($11.8 billion) in September 2015, compared with an initial estimate of 3 billion euros in 2004.
Another EPR under construction in Finland is also years behind schedule and billions over budget. The first of two EPRs under construction in China, also delayed, might go into service this year.
EDF said on Monday it was reviewing costs and deadlines for Britain's Hinkley Point project after Le Monde reported on Saturday it was set for a 1-3 billion euro budget overrun and completion could be delayed by two years to 2027.
$1 = 0.7853 pounds Reporting by Geert De Clercq; Editing by Mark Potter