UPDATE 1-French nuclear watchdog raps EDF over Flamanville failings

* Regulator says EDF must improve pre-startup testing

* Orders EDF to send it report on weldings problems (Adds ASN comment on welding problems)

PARIS, Feb 23 (Reuters) - French nuclear regulator ASN said it has told EDF to improve the running of the construction of the Flamanville nuclear reactor, which is years behind schedule and billions over budget.

The ASN has repeatedly said a schedule to load nuclear fuel at the EPR reactor in Flamanville, which is the same type as EDF is building in Britain's Hinkley Point, by year-end is tight.

ASN said EDF must improve the follow-up of pre-startup test as well as the treatment of any flaws, and to improve the information flow to the regulator.

"EDF has promised to put in place an action plan to remedy these dysfunctions," ASN said in a statement on Friday.

The ASN also said it had questioned EDF and Framatome, the company formerly called Areva, about flaws in the welding of the Flamanville reactor's steam pipes.

EDF said on Thursday some weldings on the reactor did not meet specifications but said this would not affect safety or the schedule to load fuel.

ASN said it had asked EDF to send it a complete study about the discovery and impact of the weldings problem and that it would consult experts about it in the second half of 2018.

In June, the ASN ruled that the reactor vessel's cover was fit for service despite weak spots in its steel, but would have to be replaced by 2024.

Any further delay to Flamanville would be another blow to the image of the EPR reactor. Three others have been under construction for years in Finland and China and are all over budget and schedule.

It could also force EDF to increase its cost estimate for the reactor, which it last updated to 10.5 billion euros in September 2015, from an original estimate of 3 billion euros.

Delays and cost overruns at the Flamanville reactor: https://uk.reuters.com/article/edf-nuclear-flamanville/factbox-french-epr-reacto r - y e a r s - b e h i n d - s c h e d u l e - b i l l i o n s - o v e r - b u d g e t - i d U K L 5 N 1 1 8 2 L Y 2 0 1 5 0 9 0 3 (Reporting by Geert De Clercq; Editing by Dominique Vidalon and Alexander Smith)