Dounreay Fast Reactor
The experimental fast breeder reactor at Dounreay led British research and development of nuclear energy during the 1950s and 60s.
Housed inside a steel sphere, it was built between 1955 and 1958 to test the breeder reactor concept. In 1962, it became the first fast reactor in the world to provide electricity to a national grid. Its 14MW output was enough to power a small town like Thurso (population of about 9,000). It closed down in 1977.
Decommissioning DFR is one of the most significant challenges in the UK today. It was one of only two fast reactors ever built in the UK, both located at Dounreay. It used a liquid metal alloy of sodium and potassium, known as NaK, to cool the reactor.
The fuel and a portion of the breeder material were removed from the reactor following its closure in 1977. The remaining breeder material in the reactor will be removed, packaged and transported to Sellafield for long term storage or processing.
The bulk liquid metal has also been removed from the reactor and its coolant systems. The liquid metal residues will be removed after the breeder material is removed from the reactor.
Reactor and circuit dismantling will then take place, followed by final decontamination of structures and demolition of the structures, including the containment sphere.
Prototype Fast Reactor
Dounreay’s Prototype Fast Reactor (PFR) was the second and last fast reactor to be built in the UK. It followed the successful demonstration of fast reactor technology by the Dounreay Fast Reactor (DFR).
Construction commenced in 1968 and PFR went critical in 1974.
PFR had the dual role of providing power to the national grid and offering unique research and development facilities. PFR provided information for future design and operation of large commercial fast reactor stations. It was the final step towards bringing fast reactors into use as conventional power stations.
The United Kingdom decided in the late 1980s that there was no immediate need to take the next step to a conventional station and discontinued the programme.
PFR generated 250 MW electrical (660 MW thermal output, although the original design intent was 600 MW).
The plutonium metal fuel was cooled by sodium liquid metal designed to remove heat from the reactor core. This heat was transferred via the primary and secondary sodium circuits to the steam raising plant which fed a conventional steam turbine with an electrical output.
The reactor closed in 1994. It was de-fuelled and the 1,500 tonnes of bulk sodium that once flowed through the primary and secondary circuits removed. The world’s largest liquid metal destruction plant was built at PFR to destroy this sodium, and destruction was completed in August 2008.
PFR’s mission included research and development into reactor fuel. A shielded remote handling facility, known as the Irradiated Fuel Cave (IFC), was constructed to support this work. The IFC contained approximately 70 tonnes of liquid sodium in a number of storage tanks. This sodium has been drained and destroyed and the next step is to cleanse the residue from this area. The structure will be decommissioned after completing sodium clean-up.
Dounreay Materials Test Reactor
The Dounreay Materials Test Reactor (DMTR) was the first operational reactor in Scotland.
It was constructed to test the effects of irradiation on metals and took three years to build. It was the first operational reactor to achieve criticality in Scotland in May 1958.
The reactor was contained in a steel pressure containment vessel 21.2m in diameter and 22.7m in height. It had a thermal output of 25 MWth (this was initially 10 MWth).
The reactor was served by a number of ancillary buildings, including a cooling circuit and towers, a fuel pond, post-irradiation examination (PIE) cells, laboratories, an active handling bay and administrative offices.
Operations ended in 1969.