Office for Nuclear Regulation

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Dungeness A - Pond Crane Incident Preliminary Investigation

Executive summary

Purpose of intervention

At the request of the nominated site inspector I carried out a reactive inspection to gather information related to the circumstances surrounding an incident on the fuel pond crane. This intervention focused on establishing the facts and ensuring that the licensee is addressing any shortfalls in its arrangements.

Interventions Carried Out by ONR

Magnox reported a site incident involving the discovery of a detached R2 flask Crane rail clamp. The clamp was discovered on a roadway below the skip crane rail line. Because of this, the R2 skip crane was withdrawn from service together with R1 pending internal investigation.

Explanation of Judgement if Safety System Not Judged to be Adequate

N/A

Key Findings, Inspector's Opinions and Reasons for Judgements Made

I commended Magnox for reporting the event in a timely manner and following up with a prompt internal investigation and sharing the results of the initial findings with ONR. Site suggested, and I agree, that the detachment of the clamps was mainly a result of oxide jacking. On the location of the damaged clamp, I told Magnox that it was not clear to me how it got to the position where it was found. However after some discussions, we all settled with the possibility of the crane sweeping it to the location from where it dropped to the ground.

As the crane rails are all painted white, I noted that there were no signs on top of the detached clamps indicating whether there is corrosion under the piece. When I enquired how sites detected these failures, they stated that they use a hammer to check if clamps are corroded. I stated that this does not meet relevant good practice and suggested that they develop a formal procedure to support their operation. On the issue of original crane design lives, which Magnox confirmed have all expired, Site stated that they are all over 50 years old but have gained from some refurbishment and updating, and their safety cases have been updated several times. However, I advised that they should consider developing an internal procedure for substantiating/justifying extending the life of cranes beyond their formal design life.

Conclusion of Intervention

In conclusion, based on the evidence presented to me I consider that the incident is not nuclear safety significant and that the crane integrity is not compromised. However, I have identified some weaknesses in site's arrangements which have been shared with site. There are also aspects of maintenance where evidence suggests that some information may have been lost during the transition from operations to decommissioning.

I raised actions that were accepted by site, I will continue to monitor the licensee's response to satisfactory closure.