RADIOACTIVE debris was found on a rail wagon used to carry flasks of spent nuclear fuel from Oldbury power station, through Berkeley and on to Sellafield.
The small fragments were discovered during monitoring of the wagon when the fuel arrived at the Sellafield reprocessing site on Friday, May 30.
It is thought the contamination was picked up on the feet of a flask when it was in a cooling pond at Oldbury, which is in the process of being decommissioned.
Although the flask was monitored before leaving the plant, the contamination was not detected, possibly because the flask’s feet were 'rough'.
Members of the Oldbury Site Stakeholder Group were told the feet were not perfectly smooth and metallic debris in the pond could have been pressed into them, escaping detection.
Only on arrival at Sellafield had the material loosened.
Rob Ledger, deputy site director at Oldbury, told the group that flasks were taken first by road from Oldbury to the Berkeley railhead before being loaded onto rail wagons, near a Sharpness playground.
“The rail wagons are securely locked during shipments of spent fuel and no staff or members of the public were exposed to radiation at any point during the transport operations," he said.
“Nevertheless, this was a significant event and we instigated an investigation that has now been concluded and recommendations made.”
A clean-up of the cooling ponds has also been carried out.
However Berkeley resident and district Cllr Liz Ashton was unconvinced by their assurances.
"I do not care what they say about no danger, children do not always stay where they are supposed to play and people walk around that area in Sharpness," she said.
"This sort of thing should not happen."
The incident was reported to the Office for Nuclear Regulation (ONR) and the plant has now improved its monitoring instruments and given extra training to staff.
Peter Dickenson of the ONR said it had considered whether any regulatory action was warranted but decided instead to issue a letter.
However, he warned that “it won’t just be a letter next time” if there was any repeat incident, which could involve a notice of improvement being issued.
He said Magnox, which operates the station, had conducted its own investigation into the circumstances surrounding the incident and made recommendations for improvements, which Oldbury was implementing.
He said: “We are confident that action put into place should eliminate the possibility of a repeat.”
Malcolm Lynden, the group’s chairman, said: “This has been a wake-up call for the site.”
Mr Ledger also reported a “significant near miss” to the meeting which involved a hook and chain weighing 18kg becoming detached and falling from a pile cap crane.
No-one was in the vicinity of the incident at the time but an immediate investigation was started into how it had happened.
Mr Ledger said: “These were two very disappointing and very significant events and we have taken them very seriously.”