Local MP Russell Brown is due to meet bosses

The incident happened at a reactor which had been shut down for refuelling, and Mr Brown said the plant's three other reactors were unaffected.

Mr Brown said a basket containing fuel rods was being lowered when it dropped a distance of about 5ft.

Some fuel rods remained in place in the basket but others went out of the basket and fell down the remainder of the chute.

But Mr Brown said he and Dr Murray had been assured monitoring showed no increase in radioactivity and there was little likelihood of damage to the fuel rods.

Heavily shielded container

"There is no danger to the safety of the workforce, nor the environment and most importantly there is nothing the local community should be worrying about," he said.

Company spokesman Paul Vallance said the basket involved in the incident was a heavily-shielded container holding 24 fuel rods.

He said the basket was normally lowered down the shoot allowing the rods to be placed in protected flasks at the bottom from where they could be moved away for reprocessing.

He added: "We have now been able to do a camera inspection and we have basically found that a number of fuel elements aren't where we expected them to be.

"There were 24 rods originally inside the basket. We know that 12 are still in the basket.

Completely safe

"The 12 other rods, we are not sure where they are, other than to say that because of the physical arrangements, we are almost certain that they have dropped down the fuel discharge route to the bottom of the chute."

He insisted the rods were "completely safe" as it was a "cladded part of the reactor".

He added: "Even if there is any damage to the rods, they are clearly exactly where they should be in a very highly shielded area with absolutely no personnel access."

Fuel rods are bars of uranium metal clad in an outer magnox can which are placed inside reactors as part of the nuclear fission process that generates heat and ultimately electricity.