Petteri Tiippana, assistant director of STUK, the Finnish nuclear safety authority, said that a government-commissioned inquiry into quality and safety allegations made by the environmental lobby group Greenpeace had found no evidence of transgressions.
On the 35 load-bearing welded joints inspected by STUK, "the welding procedures, the qualification of the welders, the welds themselves are well done", he said.
On the thousands of non-load bearing joints which are not inspected by STUK, "the welds were made by qualified welders and systematic inspections were made", he went on to point out.
Mr Tiippana also refuted allegations made in a television documentary broadcast that Bouygues employees had been banned from discussing safety concerns.
The inquiry found no such rules and STUK inspectors had not had any problems discussing safety with them. However, workers had to seek approval before talking to anyone off-site, such as journalists.
STUK said it had been convinced by the Bouygues project manager "that all employees are obliged to report... any safety-related deviances.
"Deviances are documented and fixed according to the quality system."
STUK said it would check this documentation.
Bouygues said that the issue was now closed and it would not comment further.
Nonetheless, the controversy was taken seriously by the French construction group, which this summer was criticized along with power utility EDF for organisation of work on concrete reinforcement in a EPR reactor which is being built in Normandy.
Areva said it was delighted with STUK's public statement as "delivering a safe EPR reactor is an absolute priority for us".
Finland's Olkiluoto3 EPR reactor is being built by a consortium led by Areva.
It is the world's first so-called third-generation nuclear reactor, an Areva design and the group's first turnkey project, has been fraught with problems and is currently running two years late and at least Â€1bn ($1.47bn) over budget.