Dounreay site restoration plan

UKAEA has publically launched its detailed proposals for the environmental restoration of Dounreay. UKAEA says that the plan is the first ever to be produced for the decommissioning of a complex nuclear site in the UK. Dounreay’s director, Peter Welsh, emphasises that the plan is a “living document that will evolve over time.” He added: “I am proud of what the team at Dounreay has achieved in producing this plan. What really matters is that we deliver in practice, and that’s what we shall now focus upon.”

UKAEA has the primary role of decommissioning its nuclear facilities and restoring the environment at its sites.

In the case of Dounreay, decommissioning will be a challenging task taking many decades to complete, and requiring the long-term commitment of significant public resources.

There will be a continuing demand for a highly skilled and experienced workforce. For some projects, innovative technological solutions will need to be developed and deployed.

Over the past two years, the UKAEA team at Dounreay has prepared a plan which addresses the overall task of restoring the Dounreay site. The Dounreay Site Restoration Plan integrates the many separate activities of decommissioning, fuel treatment, waste management and land remediation, so that the work can be done progressively, efficiently and to an ambitious but achievable programme.

Production of the plan is a significant milestone in nuclear decommissioning. It is the first example in the UK of a detailed blueprint for the restoration of a major nuclear site.

The plan envisages a period of 50-60 years to complete the decommissioning programme, half the time of the 100-year programme which was previously envisaged. Our approach is to deal with the major hazards first: all of the major radiological hazards will be removed within some 25 years. By this time, the shaft and wet silo will have been emptied. After the decommissioning programme is complete, a further period of care and surveillance will be required before the site can be released for unrestricted use.

On completion of these works, the site will enter a period of surveillance monitoring, together with maintenance for a period currently envisaged to extend to 300 years.

It is intended that the plan will be open to modifications, in order that it can respond to new opportunities, technical advances and unexpected issues. UKAEA will review the plan regularly with its stakeholders and it wll evolve over time to reflect their views and requirements.

external factors

The plan contains a number of assumptions and it is dependent upon a range of external factors. The most significant of these external factors are:

•Site end state. The end point for decommissioning individual areas of the site will be defined by criteria similar to those adopted for the delicensing of a nuclear licensed site. While this will be an achievable objective for most facilities or areas, there are some for which it may not be practicable and a suitable end point will then have to be agreed with the Regulator.

•Planning consents. The programmes for the building of new plants include a time element for obtaining planning and similar consents based upon the size and complexity of the proposed construction. The possibility that these estimates are exceeded is a significant risk to fulfilling the plan.

•ILW/HLW. ILW will be packaged to standards specified by UK Nirex and stored at Dounreay pending the availability of a UK national repository. Dounreay’s storage facilities are or will be designed for a service life of 100 years. It is assumed that a UK national repository will be available by 2040, and that it will take a further 20 years to transfer all the suitably conditioned ILW from Dounreay to the repository. If such a repository is not available on this timescale consideration will then have to be given to delaying site closure or finding interim storage elswehere. Conditioned HLW will be held on the site until it can either be sent to a UK national repository or to another location pending the availability of a national repository.

•Low level waste. The long-term strategy and associated facilities to manage all existing and future LLW arising from the Dounreay site will be determined by carrying out a Best Practicable Environmental Option Study. In the meantime, the plan assumes a new LLW facility built in the vicinity of Dounreay.

•Very low radioactive material (VLRM). The bulk of the waste produced from the decommissioning and restoration of the site could be VLRM in the form of concrete and soil.

•Prototype fast reactor (PFR) fuel management. The strategy and management of PFR fuel have been the subject of public consultation. The plan has taken account of the three possible outcomes pending a decision by the government.

•Transfer of Dounreay fast reactor (DFR) breeder elements. DFR breeder elements will be removed from the reactor, prepared for reprocessing and transported to Sellafield while the magnox reprocessing facilities remain operational. The fall back strategies, involving conditioning and storage at Dounreay pending direct disposal to a future national repository, have no significant impact on the overall timescale for completion of the site restoration programme.

•National infrastructure availability. The plan assumes that the continued safe transport of nuclear materials and radioactive wastes will be permissible.

•Resource availability. It is assumed that financial and human resources will be sufficient to meet the year-on-year demands of the plan. A shortfall in the availability of skilled staff has the potential to delay delivery of the plan.

•Shaft and silo. The decommissioning of and waste retrieval from the shaft and silo will be planned to allow a high degree of contemoraneous working at these facilities.

Achieving the timescales set out in the plan requires resources in three major categories:

•Funds necessary to implement the works within the scheduled timescales.

•Skilled people within UKAEA, particularly at Dounreay, and within the contracting organisations invited to bid for appropriate packages of work via competitive tender.

•A national repository for storage or disposal of intermediate and high level wastes.

The plan is UKAEA’s response to the 1998 Safety Audit of Dounreay. It is being submitted to the regulators for detailed assessment and evaluation. Once the regulators are satisfied with the plan, they have indicated their intention to approve an agreed programme, including key milestones and a review process.

A large number of other stakeholders have an interest in the plan. In particular, local communities will want to be assured about the environmental implications and the impact on the local economy, and government and tax payers need to understand the benefits of the work which they are funding. UKAEA has committed to present the plan to local, regional and national stakeholders and to take account of their views.

Time periods

During the restoration programme, specific activities will take place within a series of consecutive time periods, each of some 10 to 15 years duration. These have been detailed into five periods of activity.

Period one

The first period will be characterised by intense construction activity. Up to twenty new plants will be needed for waste treatment and the processing of nuclear materials to make them safe for long-term storage or disposal. The main new plants will be:

•Vitrification plant for high level waste.

•New intermediate level waste (ILW) treatment plant.

•New ILW store.

•Enabling works for shaft and silo.

•Shaft retrieval headworks.

•New low level waste (LLW) facilities.

•Nuclear fuel characterisation plant.

•Carbide oxidation plant.

•Active incinerator.

During this period, decommissioning work will continue in existing redundant facilities, for example:

•Stage 1 decommissioning of the Prototype Fast Reactor (PFR).

•Stage 1 decommissioning of the Dounreay Fast Reactor (DFR).

•Materials Test Reactor fuel reprocessing plant.

•Redundant laboratories.

•Criticality facility.

•Post irradiation examination facility.

•Dealing with the contaminated land.

A number of existing plants will need to be upgraded to allow continued operation to treat wastes and fuels, in particular:

•ILW treatment facility.

•Two ILW stores.

•Highly active liquor storage facility.

•Uranium recovery plant.

Period two

Waste will be retrieved from the shaft and silo, in one of the most challenging decomissioning projects to be undertaken at Dounreay.

During this period, the processing of remaining nuclear materials will also be completed. As fuel and waste processing plants complete operations, work will begin to decommission them.

By the end of this period, some 25 to 30 years from now, all fuel materials will have been processed or conditioned for storage, and high level wastes will have been packaged in a form suitable for long term storage and (dependent on government policy) eventual disposal. On completion of this period, all the major radiological hazards at Dounreay will have been eliminated.

Period three

This period will see the decommissioning of all Dounreay’s fuel processing and handling plants. Work will begin to decommission high level waste treatment and storage facilities, which have completed their operations. Waste plants and services required to support the ongoing decommissioning programme will continue to operate.

Period four

The decommissioning of all three of Dounreay’s nuclear reactors will be completed. Ongoing decommissioning of redundant waste facilities will continue. Post operational clean out and decomissioning or remaining redundant facilities will get underway.

Period five

By the end of the final period, 50 to 60 years from the start of the plan, the decommissioning programme will be complete.

All the redundant facilities will have been dismantled and the wastes immobilised and placed in purpose-built facilities. The remediation of contaminated ground will have been carried out. Major areas of the site will be suitable for

delicensing.

Managing uncertainty

The Dounreay Site Restoration Plan has a timescale of half a century, requires the integration of some 1500 separate but inter-dependent activities, and is expected in total to cost in the region of £4 billion (undiscounted). It contains some projects which are among the most technically challenging in the UK. Against this background, UKAEA cannot realistically peg delivery of milestones in the plan to single dates. Instead, programme risks have been identified and accessed, and delivery dates within the plan are expressed as a range, between an ‘early’ date which could be achieved if only a few of these risks were realised, and a ‘later’ date, which would be achieved if most of the risks occurred. This approach is in line with good project management practice.

Safety standards

A fundamental driver for the decommissioning of Dounreay is to provide a long-term guarantee of public safety. UKAEA has developed a safety management system which is independently accredited to internationally recognised standards.

Environmental impact

The long-term aim of the plan is the environmental restoration of the Dounreay site. To achieve that aim, some of the activities in the plan will inevitably generate discharges to the environment. But these will be kept to minimum levels, in accordance with the requirement to use best practicable means to minimise activity in all the waste discharged. Any emissions will continue to be carefully monitored by UKAEA and the regulators.

Prospects for employment

Dounreay is a very significant employer in Caithness, with about 2000 people currently working on the site including 1000 direct UKAEA employees.

Implementing the plan will require a significant increase in UKAEA resources, particularly at Dounreay. Contractors will undertake much of the work in the early part of the plan – in particular the construction of new plants – but UKAEA will need to employ sufficient staff directly to meet its obligations as a nuclear site licensee, and to be demonstrably in control of all safety-related work on its sites. The project management of the Dounreay Site Restoration Plan will be a major task.

The projections for manpower requirements show that current levels of direct employment will essentially be maintained over the first 15 to 20 years of the plan. Contract staff, many of whom may be recruited locally, will augment UKAEA personnel.

The remote location of Dounreay makes the recruitment of UKAEA staff, and contractors, more difficult than elsewhere. UKAEA is competing in a market where there is an undersupply of suitably qualified and experienced manpower: potential shortage of human resources is one of the main threats to the delivery of the programme. UKAEA has been successful in recruiting some 200 additional staff to Dounreay over the past two years. it will continue to recruit and train directly employed staff, and to engage contract staff under their control to implement construction and decommissioning projects.

The details of the full plan can be seen on UKAEA’s web site at http://www. ukaea.org.uk/sites/dounreay/rplan.htm and is available for comment.

Shaft and silo decommissioning

UKAEA has advertised for companies to tender for the retrieval of waste from the Dounreay Intermediate Level Waste Shaft and the Waste Silo.

A key element of the work is to identify the optimum solution for isolating the shaft from the surrounding environment to enable the removal of 700m3 of waste. Several options have been proposed, including that of creating an ice wall around the shaft and the formation of an underground concrete wall to prevent water entering the shaft. The current investigations on the geology and the groundwater flows around the shaft.

A waste treatment plant and an aboveground store will also need to be constructed. This will initially be used to treat, package and store wastes from the site decommissioning activities and will then handle the shaft and silo materials as they arise.