Dounreay Nuclear Power Development Establishment was established 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 program, and also fabrication and reprocessing facilities for the materials test rigs and for fuel for the FBRs.
Dounreay Nuclear Power Development Establishment
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 Harwell Laboratory.
The second reactor to achieve criticality (although the first to commence construction) was the Dounreay Fast Reactor (DFR), which came on-line in November 1959, producing an electrical output of 14 MWe. This power was exported to the National Grid 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 was a loop-type FBR cooled by primary and secondary NaK circuits, with 24 coolant loops, and fueled with uranium oxide.
The third and final UKAEA-operated reactor to be built on the Dounreay site was the Prototype Fast Reactor (PFR), which achieved criticality in 1974 and began supplying National Grid power in January 1975. The output of PFR was 250 MWe. The reactor was taken offline in 1994, marking the end of nuclear power generation at the site. PFR was a pool-type FBR, cooled by liquid sodium and fueled with MOX.
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.
On 1 April 2005 the Nuclear Decommissioning Authority (NDA) became the owner of the site, with the UKAEA remaining as operator. Decommissioning of Dounreay is 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 .
Apart from decommissioning the reactors, reprocessing plant, and associated facilities, there are five main environmental issues to be dealt with:
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 £140,000.
A 65-metre 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. There are fears that accumulated material might represent a potential critical mass
Irradiated nuclear fuel particles on the seabed near the plant, estimated about 10,000 in number. Some are being washed ashore, including as of 2006 about 70 smaller particles on the public Sandside Bay beach and one at a popular tourist beach at Dunnet.  The way these particles escaped the site has not been determined, there are several plausible possibilities. The risk to the public is considered low.
18,000 cubic metres of radiologically contaminated land, and 28,000 cubic metres of chemically contaminated land.
1,350 cubic metres of high and medium active liquors and 2,550 cubic metres of unconditioned intermediate level nuclear waste in store.
1,500 tonnes of sodium, 900 tonnes of this radioactively contaminated from the Prototype Fast Reactor. Nuclear Decommissioning Authority ownership
The Vulcan Naval Reactor Test Establishment (NRTE) 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.
For over 40 years Vulcan has been the cornerstone of the Royal Navy's nuclear propulsion program, testing and proving the operation of four generations of reactor core and currently testing its fifth. Its reactors have significantly led the operational submarine plants in terms of operation hours, proving systems, procedures and safety.
Rolls-Royce, who design and procure all the reactor plants for the Royal Navy from their Derby headquarters, operate Vulcan on the behalf of the MoD and employ around 280 staff there, lead by a small team of staff from the Royal Navy.
The cost of decommissioning NRTE facilities when they become redundant, including nuclear waste disposal, was estimated at £2.1 billion in 2005. 
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, though it did not go critical until 1965. HMS Vulcan is a Rolls-Royce PWR 1 reactor plant and tested Cores A, B and Z before being shutdown 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 accident.The plant was decommissioned in 1992 after more than 250 separate trials and a total of 27 years successful operation.
Shore Test Facility (STF)
Atomic Energy Research Establishment
Nuclear power in the United Kingdom
Energy policy of the United Kingdom
Energy use and conservation in the United Kingdom