UK’s 7th national report on compliance with the obligations of the convention on nuclear safety

The convention on nuclear safety’s aim is to “legally commit participating States operating land-based nuclear power plants to maintain a high level of safety by setting international benchmarks to which States would subscribe“. The UK’s 7th report to this convention is now available.

At 238 pages long it is not an inviting read but it is, nonetheless, quite interesting and provides a good overview of nuclear safety in the UK including a review of the regulations and the operations of the regulators.

An interesting quote (paragraph 16.23) is “Whilst REPPIR does not prescribe a specific probability to what is reasonably foreseeable, events with a frequency of 1×10(-5) to 10(-6) per year are considered, with any cliff edge effects from events of lesser probability also being considered“. ONR usually reframes from accepting any numerical value for “reasonably foreseeable”. This value puts it below the probability of any events listed in the National Risk Register which may surprise some people.


Review – Managing the Unexpected in Decommissioning, IAEA Nuclear Energy Series No. NW-T-2.

nwt28IAEA Nuclear Energy Series No. NW-T-2.8

This document published in March 2016 discusses the surprises that can occur when decommissioning nuclear facilities. It claims to be a good practice guide with expert opinion rather than recommendations made on the consensus of member states.

It explains that nuclear plant, particularly those with a long history, are not always built as recorded. It warns that: “When the nature of a decommissioning project is found to be substantially different to that expected, it often results in unplanned work to investigate and redefine the nature of the project, which may introduce delays and cost overruns, and which has the potential to expose decommissioning staff to additional industrial hazards and unplanned exposure to radiation”. A good decommissioning plan would consider the worst case and be ready to respond accordingly, considering it reasonably foreseeable that additional radioactive sources or contamination might be found or that the plant uncovered might not match the plans exactly and be ready to modify work plans and to protect the workforce against new hazards.

The authors provide a number of examples including finding bolts that were fully welded in place rather than spot welded thus defeating the equipment made to remotely remove the bolts. Other notable issues have occurred when trying to decommission the services to a building and accidently affecting supplies to neighbouring buildings. The finding of unexpected radioactive material or other hazardous material such as asbestos is also not uncommon.

Careful reading of records and investigation of the plant is recommended to characterise the plant and the radioactive inventory as well as possible to minimise the risks of unexpected issues.

The paper discusses the managerial mechanisms that are required to cope with the unexpected and show parallels with emergency planning. These include the ability to stop work on projects while issues are investigated and plans revised and require that the organisation is flexible enough to provide the necessary resource in a timely manner. A good stakeholder engagement plan is required to ensure that communications with groups such as the regulators and the public are appropriate.

Interestingly the report does not mention the role of the site’s Nuclear Safety Committee (see Ref for an ONR description of the NSC) in scrutinising decommissioning plans, hearing reports on progress and the response to issues, and challenging the Company to do better. In the UK this is a key supervisory role.

Much of the report is given over to case studies which provide valuable insight into the experience already gained in decommissioning nuclear facilities.

The report concludes that “Unknowns in decommissioning cannot be eliminated, regardless of the efforts applied. This is especially the case in old facilities where documentation may have been lost or where modifications were carried out without updates to reports. As a result, when planning for decommissioning, it is prudent to assume that such problems will occur, and ensure that arrangements are in place to deal with them when they arise. This approach will not only improve the efficiency of the decommissioning project, but will also improve the safety of the operations”.

This report is well worth a read for anybody involved in the decommissioning of nuclear facilities including safety case engineers, project managers, team leaders, the emergency/contingency planning teams and the regulators.