Dounreay

Dounreay   (Nuclear power station)
Scottish nuclear facility

Dounreay is on the north coast of Caithness, in the Highland area of Scotland and west of the town of Thurso. Dounreay was originally the site of a castle (now a ruin) and its name derives from the Gaelic for 'fort on a mound.' Since the 1950s it has been the site of two nuclear establishments, for the development of prototype Fast Breeder Reactors (FBRs) and submarine reactor testing. Most of these facilities are now being decommissioned.

History

Dounreay formed part of the battlefield of the Sandside Chase in 1437.

The site is used by the United Kingdom Atomic Energy Authority (Dounreay Nuclear Power Development Establishment) and the Ministry of Defence (Vulcan Naval Reactor Test Establishment), and the site is best known for its five nuclear reactors, three owned and operated by the UKAEA and two by the Ministry of Defence.

The nuclear power establishment was built on the site of a World War II airfield, called RAF Station Dounreay. It became HMS Tern (II) when the airfield was transferred to the Admiralty by RAF Coastal Command in 1944, as a satellite of HMS Tern at Twatt in Orkney. It never saw any action during the war and was placed into care and maintenance in 1949.

Dounreay is near the A836 road, west of the town of Thurso, which grew rapidly when the research establishment was developed during the mid-20th century. The establishment remained a major element in the economy of Thurso and Caithness until 1994 when the government ordered that the reactors be closed for good; a large workforce employed in the clean-up of the site (which is scheduled to continue until at least 2025) remains.

Dounreay NPDE

Dounreay Nuclear Power Development Establishment was formed in 1955 primarily to pursue the UK Government policy of developing Fast Breeder Reactor (FBR) technology. The site was operated by the United Kingdom Atomic Energy Authority (UKAEA). Three nuclear reactors were built there by the UKAEA, two of them FBRs plus a thermal research reactor used to test materials for the programme, and also fabrication and reprocessing facilities for the materials test rigs and for fuel for the FBRs.

Dounreay was chosen as the reactor location for safety reasons, in case of an explosion. The first reactor built was surrounded by a large steel sphere, still a prominent feature of the landscape. The sphere was constructed by the Motherwell Bridge Company.

Dounreay MTR

The first of the Dounreay reactors to achieve criticality was the Dounreay Materials Test Reactor (DMTR) in May 1958. This reactor was used to test the performance of materials under intense neutron irradiation, particularly those intended for fuel cladding and other structural uses in a fast neutron reactor core. Test pieces were encased in uranium-bearing alloy to increase the already high neutron flux of the DIDO class reactor, and then chemically stripped of this coating after irradiation. DMTR was closed in 1969 when materials testing work was consolidated at the Atomic Energy Research Establishment, Harwell Laboratory, in Oxfordshire.

Dounreay Fast Reactor

The second operational reactor (although the first to commence construction) was the Dounreay Fast Reactor (DFR), which achieved criticality on 14 November 1959, producing an electrical output of 14 MWe. This power was exported to the National Gri from 14 October 1962 until the reactor was taken offline for decommissioning in 1977. During its operational lifespan, DFR produced over 600 million kWh of electricity.

DFR and associated facilities cost £15m to build. It was designed to generate 60 MW thermal power and achieve a 2% fuel burn up.

DFR was a loop-type FBR cooled by primary and secondary NaK circuits, with 24 primary coolant loops. The reactor core was initially fuelled with uranium metal fuel stabilised with molybdenum and clad in niobium. The core was later used to test oxide fuels for PFR and provide experimental space to support overseas fast reactor fuel and materials development programmes.

PFR

The third and final UKAEA-operated reactor to be built on the Dounreay site was the Prototype Fast Reactor (PFR). PFR was a pool-type FBR, cooled by liquid sodium and fueled with MOX. It achieved criticality in 1974 and began supplying National Grid power in January 1975. The output of PFR was 250 MWe. There were many delays and reliability problems before reaching full power.

The reactor was taken offline in 1994, marking the end of nuclear power generation at the site. The lifetime load factor recorded by the IAEA was 26.9%. A remotely operated robot dubbed 'The Reactorsaurus' will be sent in to remove waste and contaminated equipment from this reactor as it is too dangerous a task for a human. The control panel for the reactor has been earmarked for an exhibition on the reactor at the London Science Museum in 2016.

Subsequent activity

Since the reactors have all been shut down, care and maintenance of old plant and decommissioning activities have meant that Dounreay has still retained a large work-force. Commercial reprocessing of spent nuclear fuel and waste was stopped by the UK government in 1998 although some waste is still accepted from other nuclear facilities in special circumstances.

Decommissioning

In September 1998 a safety audit of the plant was published by the Health and Safety Executive and the Scottish Environment Protection Agency. The results were damning and 143 recommendations were made. In November that year, the UKAEA announced a proposed timetable for accelerated decommissioning, reducing the original schedule from 100 years to 60 years. The cost was initially estimated at £4.3 billion.

The Department of Trade and Industry (DTI) was presented with three options for dealing with 25 tonnes of radioactive reactor fuel lying at Dounreay. The options were: 1) to reprocess it at Dounreay, 2) to reprocess some at Dounreay some at Sellafield or 3) to store it above ground at Dounreay.

An accelerated decommissioning plan was welcomed by the Friends of the Earth Scotland, but the environmental group remained opposed to any further fuel reprocessing at the site.

Nuclear Decommissioning Authority ownership

On 1 April 2005 the Nuclear Decommissioning Authority (NDA) became the owner of the site, with the UKAEA remaining as operator. Decommissioning of Dounreay was initially planned to bring the site to an interim care and surveillance state by 2036, and as a brownfield site by 2336, at a total cost of £2.9 billion.

A new company called Dounreay Site Restoration (DSRL) was formed as a subsidiary of the United Kingdom Atomic Energy Authority (UKAEA) to handle the decommissioning process. By May 2008, decommissioning cost estimates had been revised. Removal of all waste from the site was expected to take until the late 2070s to complete and the end-point of the project was scheduled for 2300.

Apart from decommissioning the reactors, reprocessing plant, and associated facilities, there are five main environmental issues to be dealt with:

• A deep shaft used for intermediate level nuclear waste disposal is contaminating some groundwater, and is threatened by coastal erosion in about 300 years time. The shaft was never designed as a waste depository, but was used as such on a very ad-hoc and poorly monitored basis, without reliable waste disposal records being kept. In origin it is a relic of a process by which a waste-discharge pipe was constructed. The pipe was designed to discharge waste into the sea. Historic use of the shaft as a waste depository has resulted in one hydrogen gas explosion caused by sodium and potassium wastes reacting with water. At one time it was normal for workers to fire rifles into the shaft to sink polythene bags floating on water.
• Irradiated nuclear fuel particles on the seabed near the plant, estimated about several hundreds of thousands in number. The beach has been closed since 1983 due to this danger, caused by old fuel rod fragments being pumped into the sea. In 2008, a clean-up project using Geiger counter-fitted robot submarines will search out and retrieve each particle individually, a process that will take years. The particles still wash ashore, including as at 2009, 137 less radioactive particles on the publicly accessible but privately owned close-by Sandside Bay beach and one at a popular tourist beach at Dunnet. In 2012 a two million becquerel particle was found at Sandside beach, twice as radioactive as any previously found particle.
• 18,000 cubic metres (640,000 cu ft) of radiologically contaminated land, and 28,000 cubic metres (990,000 cu ft) of chemically contaminated land.
• 1,350 cubic metres (48,000 cu ft) of high and medium active liquors and 2,550 cubic metres (90,000 cu ft) of unconditioned intermediate level nuclear waste in store.
• 1,500 tonnes (1,700 tons) of sodium, 900 tonnes (990 tons) of this radioactively contaminated from the Prototype Fast Reactor.

Historically much of Dounreay's nuclear waste management was poor. On 18 September 2006, Norman Harrison, acting chief operating officer, predicted that more problems will be encountered from old practices at the site as the decommissioning effort continues. Some parts of the plant are being entered for the first time in 50 years.

In 2007 UKAEA pleaded guilty to four charges under the Radioactive Substances Act 1960 relating to activities between 1963 and 1984, one of disposing of radioactive waste at a landfill site at the plant between 1963 and 1975, and three of allowing nuclear fuel particles to be released into the sea, resulting in a fine of £140,000.

In 2007 a new decommissioning plan was agreed, with a schedule of 25 years and a cost of £2.9 billion, a year later revised to 17 years at a cost of £2.6 billion.

Due to the uranium and plutonium held at the site, it is considered a security risk and there is a high police presence. The fuel elements, known as "exotics", are to be removed to Sellafield for reprocessing, starting in 2014 or 2015.

In 2013 the detail design of the major project to decommission the intermediate level waste shaft was completed, and work should begin later in the year. The work will include the recovery and packaging of over 1,500 tonnes of radioactive waste. As of 2013, the "interim end state" planned date had been brought forward to 2022-2025. In March 2014 firefighters extinguished a small fire in an area used to store low-level nuclear waste.

On 7 October 2014 a fire on the PFR site led to a "release of radioactivity via an unauthorised route". The Office for Nuclear Regulation (ONR) concluded that "procedural non-compliances and behavioural practices" led to the fire, and served an improvement notice on Dounreay Site Restoration Limited.

In 2016 the task of dismantling the PFR core commenced. Plans were also announced to move about 700 kg (1,500 lb) of waste Highly Enriched Uranium to the United States.

Vulcan NRTE

The Vulcan Naval Reactor Test Establishment (NRTE) (formerly HMS Vulcan) is a Ministry of Defence (MoD) establishment housing the prototype nuclear propulsion plants of the type operated by the Royal Navy in its submarine fleet. Its final reactor shut down on 21 July 2015, with post operational work continuing to 2022. Originally it was known as the Admiralty Reactor Test Establishment (ARTE).

For over 40 years Vulcan has been the cornerstone of the Royal Navy's nuclear propulsion programme, testing and proving the operation of five generations of reactor core. Its reactors have significantly led the operational submarine plants in terms of operation hours, proving systems, procedures and safety. The reactors were run at higher levels of intensity than those on submarines with the intention of discovering any system problems before they might be encountered on board submarines.

Rolls-Royce, which designs and procures all the reactor plants for the Royal Navy from its Derby offices, operates Vulcan on the behalf of the MoD and employs around 280 staff there, led by a small team of staff from the Royal Navy. Reactors developed include the Rolls-Royce PWR1 and PWR2.

In 2011 the MoD stated that NRTE could be scaled down or closed after 2015 when the current series of tests ends. Computer modelling and confidence in new reactor designs meant testing would no longer be necessary. The cost of decommissioning NRTE facilities when they become redundant, including nuclear waste disposal, was estimated at £2.1 billion in 2005.

Dounreay Submarine Prototype 1 (DSMP1)

The first reactor, PWR1, is known as Dounreay Submarine Prototype 1 (DSMP1). The reactor plant was recognised by the Royal Navy as one of Her Majesty's Submarines (HMS) and was commissioned as HMS Vulcan in 1963. It went critical in 1965. HMS Vulcan is a Rolls-Royce PWR 1 reactor plant and tested Cores A, B and Z before being shut down in 1984. In 1987, the plant was re-commissioned as LAIRD (Loss of Coolant Accident Investigation Rig Dounreay) a non-nuclear test rig, the only one of its kind in the world. LAIRD trials simulated loss of coolant accidents to prove the effectiveness of systems designed to protect the reactor in loss-of-coolant accidents.

Shore Test Facility (STF)

The second reactor, PWR2, is housed in the Shore Test Facility (STF), was commissioned in 1987, and went critical with Core G the same year. The plant was shut down in 1996, and work began to refit the plant with the current core, Core H, in February 1997. This work was completed in 2000 and after two years of safety justification the plant went critical in 2002. Vulcan Trials Operation and Maintenance (VTOM) (the programme under which Core H is tested) was completed and the reactor shut down on 21 July 2015. The reactor will be de-fuelled and examined, and post operational work will continue to 2022. The site would then be decommissioned along with facilities at neighbouring UKAEA Dounreay.

In January 2012 radiation was detected in the reactor's coolant water, caused by a microscopic breach in fuel cladding. This discovery led to HMS Vanguard being scheduled to be refuelled early and contingency measures being applied to other Vanguard and Astute-class submarines, at a cost of £270 million, before similar problems might arise on the submarines. This was not revealed to the public until 2014.

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References

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