French utility company EDF said yesterday that the problems may impact on the costs and timing for starting the reactor, which is already behind schedule.
The site is 30 miles from the Guernsey coast and 20 miles from Alderney.
France’s ASN nuclear regulator warned on 28 February that the substandard weldings could have an impact on the Flamanville start-up calendar.
‘Following the current checks and the licensing process by the ASN, EDF will be able to specify whether the project requires an adjustment to its timetable and its costs,’ EDF said in a statement yesterday.
The Flamanville reactor is expected to load nuclear fuel at the end of 2018.
Its cost was estimated in 2015 at ¤10.5bn, more than three times its original budget.
The site currently houses two pressurised water reactors that came into service in 1986 and 1987.
Construction on the new European pressurised reactor began on 4 December 2007.