are best known for their five nuclear reactors, three formerly owned and operated by the UKAEA and two by the Ministry of Defence. During the 1980s and 1990s, a visitor centre was opened in the former air traffic control tower. Visitors would be taken by bus to the PFR building where anything electronic, including watches and cameras, would be stored away securely until return. White coats were worn along with radiation badges. A guided tour through the air lock into the reactor building was then conducted, walking around the reactor core and then returning via scientists working behind thick mineral glass screens. Dounreay Nuclear Power Development Establishment Dounreay Nuclear Power Development Establishment was formed in 1955 primarily to pursue the UK Government policy of developing civil 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, first a materials test reactor, then two fast breeder reactor prototypes. There were also fabrication and reprocessing facilities for the materials test rigs and for fuel for the FBRs. Dounreay was chosen as the reactor location, remote from large centres of population, for safety reasons. The site has been managed by the site licence Dounreay Site Restoration Ltd (DSRL) since 2012, but the NDA will assume complete control when DSRL becomes a wholly owned subsidiary of the NDA in March 2021. Dounreay Materials Test Reactor The first of the Dounreay reactors to achieve criticality was the Dounreay Materials Test Reactor (DMTR) in May 1958, which was a DIDO class research reactor, producing a high neutron flux. 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 this class of reactor, and then chemically stripped of this coating after irradiation. DMTR was closed in 1969 when materials testing work was consolidated at Harwell Laboratory. 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. Power was exported to the National Grid from 14 October 1962 until the reactor was taken offline for decommissioning in March 1977. During its operational lifespan, DFR produced over 600millionkWh of electricity. DFR and