(Adds details, EDF and ASN comments, power prices, background)
PARIS, Sept 13 (Reuters) - French regulators have demanded heightened supervision at EDF's Belleville nuclear power station citing failures in safety standards, regulator ASN said on Wednesday.
There were eight incidents rated level 1 -- the lowest risk on a scale of 1 to 7 on the international nuclear and radiological event scale (INES) -- last year, with most arising from a lack of supervision of reactor activity, it said.
"ASN also noted several failures by the operator in identifying and analysing the consequences of anomalies affecting certain safety-critical equipment," it said in a statement.
ASN said EDF had failed to make any notable improvements to date. It also raised concerns about the speed of response of EDF to concerns it had raised and said EDF was not providing reassuring answers.
An EDF spokeswoman said the increased supervision would not affect power output and that the company had put forward an action plan to tackle the issues raised. ASN had agreed to the plan, she said.
"ASN will regularly monitor the effectiveness of the action plan deployed by EDF," ASN said, adding that another inspection similar to one in April will be carried out next year.
The regulator's latest findings may heighten concerns over French nuclear power supply this winter after it ordered EDF in August to carry out a review of all components in France's 58 nuclear reactors that were made by Areva's foundry Creusot Forge by the end of 2018.
The Belleville nuclear plant, located in central France, has two 1,300 megawatt capacity reactors. Belleville 1 reactor has been offline since May 27 and is expected to restart production on Thursday. Belleville 2 is expected to go offline for planned maintenance from Oct. 7 until Nov. 9.
French power prices for delivery in the fourth quarter rose after the regulator's announcement. The contract was up 1.47 percent at 51.85 euros per megawatt-hour (MWh), while the German equivalent was up 1.30 percent at 39.10 euros/MWh. (Reporting by Bate Felix; editing by Richard Lough and Jason Neely)