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Dounreay Nuclear Reactors
Dounreay, near Thurso, Caithness, Scotland, UK
associated engineer
T.C. Waters
date  March 1955 - May 1958, November 1959, 1968 - 1974
era  Modern  |  category  Power Generation  |  reference  NC980667
ICE reference number  HEW 1708
The UK's only two fast breeder nuclear reactors were built at Dounreay in Scotland. One of them was the first such reactor to generate electricity for public consumption. In all, three UK Atomic Energy Authority reactors were built on the site, which is now undergoing decommissioning.
The focus of the Dounreay project was to develop fast breeder reactors, to prove the then untested theory that they would be able to generate electricity while breeding additional nuclear fuel. The remote coastal location provided both safety and abundant supplies of water.
The three UKAEA reactors at Dounreay were: the first full-scale experimental fast breeder reactor, Dounreay Fast Reactor (DFR); the Prototype Fast Reactor (PFR); and the Dounreay Materials Test Reactor (DMTR). There are also fuel fabrication plants, laboratories and fuel reprocessing plants on the 55 hectare site.
There are a further two reactor at Dounreay, operated by the Ministry of Defence in connection with the Royal Navy's submarine installations. The Royal Navy Vulcan submarine facility has occupied part of the site since 1957.
Although construction began with the Dounreay Fast Reactor (DFR), it was the DMTR that was first to go critical in May 1958. It had a thermal output of around 25MW and was stood down in 1969.
The DFR was completed in December 1958 and achieved criticality in November 1959. Its reactor is housed in a vault covered by a 41.1m diameter green sphere. The sphere was fabricated from the inside and constructed using steel plates. Its spherical shape is designed to cope with the vacuum created inside it.
The DFR first exported power to the UK's National Grid on 14th October 1962. It had a typical electrical output of 14MW from a thermal output of 60MW, and operated until 1977.
Consent was given for the PFR in 1966 and construction began in 1968. The reactor went critical in 1974 and first supplied the National Grid in 1975. Its electrical output was 250MW from a thermal output of 660MW, and it ceased operating in 1994.
A tunnel leading out from the site under the seabed carried four 230mm diameter cast iron pipes. These discharged low-radioactivity effluent into the sea during the period 1957 and 1992.
Closure of the whole site was announced in 1998, although the famous green sphere will remain as a listed building. Reprocessing of plutonium and uranium continued until 2001, and fuel fabrication until 2004. Now the main activity on the UKAEA is decommissioning the reactors.
By 2025, all redundant infrastructure at Dounreay should have been demolished and the nuclear waste made safe for long term storage or disposal. However, it could be 2060 before the site can be redeveloped.
Dounreay has had its share of incidents. From the 1960s onwards there was offshore contamination by particles of fuel rods, and fishing was banned in 1997. In 1977, there was an explosion in a disposal shaft for contaminated waste. The reprocessing plant was rendered inoperable in 1996 by a radioactive leak. In 2007, it was revealed that until 1975 nuclear waste had been stored in landfill on the site.
Manin contractor (PFR): Taylor Woodrow
Main contractor (DFR): Whatlings
Contractor (sphere): Motherwell Bridge Company
Research: ECPK
reference sources   CEH SHI

Dounreay Nuclear Reactors