Office for Nuclear Regulation

Sellafield – B6 Diffuser Demolition – Tower Crane Operation readiness inspection

Executive summary

Purpose of Intervention

Sellafield Limited (SL) has requested ONR’s agreement under its arrangements made under Licence Condition 22 [Modification or experiment on existing plant] for the operation of a tied tower crane to assist demolition of the Pile 1 chimney diffuser.

I undertook an intervention at the Sellafield Site on 10 and 11 October 2018.  The purpose of the intervention was to provide evidence to support ONR’s judgement concerning SL’s readiness to commence operation of a tied tower crane to assist demolition of the Pile 1 chimney diffuser prior to issue of a licence instrument to permit that activity.

Interventions Carried Out by ONR

I undertook an intervention against the requirements of licence condition 22(1) which requires the licensee to make and implement adequate arrangements to control any modification or experiment carried out on any part of the existing plant or processes which may affect safety.  My intervention was completed in accordance with ONR’s technical inspection guide NS-INSP-GD-022 Revision 4 (LC22: Modification or Experiment on Existing Plant) that can be found at

SL provided an overview of project readiness and progress with its Hazardous Activity Readiness Review (HARR).  ONR specialist inspectors engaged with SL staff and contractors and inspected the following topic areas:

ONR visited the construction compound to inspect the block handling route, the F10 temporary storage location, and the Calder Landfill Extension Segregated Area.

Explanation of Judgement if Safety System Not Judged to be Adequate


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

The intervention identified several areas that remain to be completed prior to tower crane operation.  This includes submission to ONR of SL’s approved HF verification report, completion of training / competence assurance for those making the decision on whether a lift may commence; submission of SL’s nuclear inspection and oversight observation report and completion of SL’s Hazardous Activity Readiness Review process and report of this to ONR.  However, this intervention has provided ONR with confidence that SL is in control of the completion of these planned activities, and there is a mature hazardous activity readiness review process in place to confirm completion of those outstanding activities required to be complete prior to actual crane operations being authorised by the duty holder.  ONR is satisfied that SL has adequate plans in place to complete outstanding matters prior to tower crane operation.

SL has highlighted to ONR its intention to develop the detailed removal methodology for 8 concrete blocks that are directly above the tower crane lateral ties nearer to the time of removal, such that the demolition of these blocks benefits from the learning from experience of prior block removals.  SL’s safety case encompasses the entire diffuser demolition activity and removal of the 8 blocks was identified in ONR’s specialist assessment as being safety significant in that they present a dropped load risk to the tower crane lateral ties; and so was one focus area of this ONR intervention.  I was satisfied that SL has in place adequate management controls (including an operating rule that prohibits loads not assessed as safe to lift over the lateral ties from being lifted) to prevent the removal of the identified 8 blocks until such time as the detailed methodologies for their removal have been completed.

 I judge that an inspection rating of GREEN is merited.

Conclusion of Intervention

SL provided an adequate overview of the project’s readiness to commence tower crane operation, including the status of enabling activities.  This overview identified those planned enabling activities that remain to be completed before physical demolition is able to commence.  SL also identified planned documentation that remains to complete its governance process.  This intervention targeted: Emergency arrangements; tower crane independent certification; concrete block cutting and lifting arrangements; the capture of learning from experience; operational decision making including command and control; procedures; fatigue; personnel competence; and waste management arrangement.  My intervention confirmed that whilst SL is not ready to immediately commence the operation of the tower crane to assist demolition of the B6 diffuser due to the identified items that remain to be completed, the governance arrangements SL has in place (including the Hazardous Activity Readiness Review) give me confidence that the activity will not be authorised by SL’s duty holder until they are completed.

At the time of this intervention, as noted above, SL remain to submit its approved human factors verification report for tower crane operations.  ONR has been provided with a mature draft of the report, however submission of the approved report to ONR is required to allow ONR to complete its specialist assessment in this area and is a pre-requisite for issue of a licence instrument to permit this activity. 

I am satisfied with the governance arrangements in place to secure closure of those activities required to be complete prior to actual crane operations which is a constructive approach to enable ONR to permit tower crane operation and so achieve effective delivery against a clear and prioritised safety and security outcome.  The majority of the activities have been completed and the remaining actions are regarded as routine business; although as discussed above, ONR will seek closure of them prior to issue of a licence instrument to permit operation of the tower crane to assist diffuser demolition.  I am satisfied that an inspection rating of GREEN is merited.