An inquiry is being carried out into a blunder at a north Wales nuclear power station.

It happened after refuelling had taken place on a reactor at Wylfa in Anglesey.

Two plugs had to be removed from the top of the charge chute in a standpipe through which fuel is fed.

Earlier this month the fuelling machine was moved off a reactor without the lower plug having been put back in the chute.

This was not fully in accordance with the reactor safety case, which requires both plugs to be in place, according to British Nuclear Fuels.

Investigation under way

An investigation is being carried out but the episode was level 0 in the international nuclear event scale.

Wylfa station operates magnox type reactors and is owned by Magnox Electric.

The name magnox is derived from the magnesium alloy canisters which contain the nuclear fuel.

Wylfa power station is scheduled to close in 2004.