The UKAEA has some 200 facilities that now require decommissioning. They include 15 reactors, accelerators, fuel fabrication and reprocessing plants.

Although decommissioning had taken place in the UKAEA for some years, until the 1980s this work was largely for ‘house-keeping’ purposes and to counter the possible effects of deterioration of structures.

By 1990, a large number of facilities had started to close in the UKAEA. These included the Steam Generating Heavy Water Reactor (SGHWR) at Winfrith, the DIDO and PLUTO reactors at Harwell and the Mayfair post-irradiation examination facility at Culcheth.

The management of these liabilities represents a significant challenge that needs a well-focused and dedicated effort separated from the conflicting pressures of other business objectives. This led to the ‘new’ UKAEA which is probably unique in being a single mission nuclear liability management organisation, apart from our responsibility for the UK fusion programme.

The key elements of this mission:

• UKAEA will manage the nuclear liabilities in a safe and cost effective manner.

• UKAEA will retain the nuclear site licences.

• UKAEA will concentrate on planning and procurement, will use contractors wherever appropriate but will use our own staff where UKAEA control is essential.

MANAGEMENT ARRANGEMENTS

It was clear that decommissioning tasks in the UKAEA should be managed as discrete projects using best practice project management. It was also obvious that the required number of client project managers would vary over the years as large and small projects were initiated and completed. A third issue related to the responsibilities of the UKAEA as site licence holder and the need to ensure continuity of knowledge and experience relevant to the nuclear facilities being decommissioned.

There is one significant difference between most decommissioning projects and other more conventional projects, such as construction and that relates to the greater uncertainty in specification; this is partly due to the age of the facilities, partly to their non-routine nature and partly to their use for different R&D purposes.

For every decommissioning project a UKAEA member of staff is appointed to take responsibility. In the larger and more complex projects staff from a contractor capable of supplying project management and other relevant skills have also been introduced to support UKAEA. This support has been particularly important in the initiation stages of projects where significant work has to be carried out to resolve uncertainties and pave the way for the specifications to be used in placing contracts for implementation stages. These “managing agency” arrangements have proved useful in major decommissioning projects and will be used in future, wherever appropriate. However, it is clear that there comes a time in the life-cycle of a decommissioning project where the specification has been firmly settled, and it is then more appropriate to have a simpler interface between the UKAEA manager responsible and the main contractor. This is now the situation that applies at the Windscale Piles, Windscale Advanced Gas-cooled Reactor (AGR) and SGHWR, all projects that involved managing agencies at earlier stages.

Given the number, size and complexity of the projects at the Dounreay site the UKAEA is employing a “management support contractor” to provide additional staff with a range of specialist project management, environmental and commercial skills to assist the UKAEA in the management of the site and the many different projects being undertaken. The UKAEA retains the site licence, is fully responsible for safety and the programme of work but the joint skills of the UKAEA and the management support contractor are being employed in a manner that benefits both organisations.

LESSONS LEARNED

During the past 10 years of decommissioning in the UKAEA many lessons have been learned and these are being fed back into our procedures for the management of the future programme. In particular, our procurement policy has since matured.

Option studies

A key element in our planning of projects is an early study of all possible options taking into account government policy, safety, environmental, financial and resourcing considerations as well as the views of regulators and other stakeholders. Contractors have provided valuable inputs and on occasion we have sought an option study as part of the bid for the implementation phase.

Project risk management

Decommissioning projects are subject to a wide variety of risks and it has proved valuable to carry out a risk assessment during the study of options and once the preferred option has been selected. A risk “prompt list” has been devised for decommissioning projects; this leads to a risk log and then to the estimation of the likelihood of each threat together with its impact on the performance, schedule and cost of the project. This analysis is a valuable input into the selection of the contract strategy for the project and the development of a plan to manage the risk which remains with the client.

Fit for purpose specification

To ensure a successful contract between client and contractor it is essential that the specification is fit for purpose. Our policy is that risk should be placed with the party best equipped to manage it. Where significant uncertainties exist (eg on the extent of contamination) it is best to resolve uncertainties by prior study before going to the market for the main implementation task.

Seeking ideas from contractors

Although a strong competitive market for decommissioning has developed in the UK with a number of very experienced contractors, in certain circumstances it is valuable to ensure that the views of contractors with experience outside the nuclear field are sought. This can be achieved by encouraging consortia or joint ventures to bid for work. Seeking competition has been shown to encourage innovative proposals that produce benefits for both client and contractor.

Incentivisation to minimise waste

In some circumstances, particularly where monitoring is straightforward for waste categorisation, benefits have been obtained by incentivising the contractor to minimise the volumes of waste generated in decommissioning. This may be achieved by taking care over segregation or in the monitoring process. However, such incentivisation is not appropriate in all cases.

Dismantling technologies

There have been a number of innovative techniques applied to nuclear decommissioning tasks. These include the following:

• Systems developed for sub-sea work on oil and gas installations used for the fuel recovery and clean-up of the water ducts of the two Windscale Piles.

• With a large number of similar gloveboxes to dismantle, a robotic system was used inside a contained area to size reduce them and sort the wastes.

• In a hot cell line where the radiation levels prevented man access and it was impossible to carry-out a successful clean-up with the installed handling equipment, a robotic system was used to size reduce the in-cell equipment and then to decontaminate the cell to allow man access and final demolition.

• Cutting and handling systems were developed and successfully used for cutting the standpipes and removal of the WAGR pressure vessel top dome.

Decontamination timescales

These options determine the optimum timescales for the different stages of decommissioning. However, one clear message has emerged from our experience: there may be benefit in delaying some decommissioning tasks involving short-lived beta-gamma isotopes, but there is a strong advantage in dealing promptly with facilities contaminated with plutonium, because of the ingrowth of americium and the effect of alpha damage on the materials in contact with the plutonium.

Strategic planning system

The overall planning of the UKAEA’s decommissioning and waste management has been improved recently by the development of a software package that helps us to optimise the strategies to appropriate assumptions and criteria. It permits the integration of many of the aspects of decommissioning and waste management planning that were previously carried out in isolation and allows us to test ‘what if’ scenarios.

Parametric cost estimating

In estimating the overall cost of decommissioning in the UKAEA considerable weight has been given to the accumulating data base of tendering prices. However, prices can vary significantly and to provide a more objective method of estimating decommissioning costs we have developed a parametric system that relates the predicted cost to the detailed parameters of the facility in question. This technique, which uses a computer-based package, is of value in allowing an assessment of tendered prices from contractors, but is also of value in option studies and in refining the overall liabilities estimate.