Oscillator Reactor) built in 1963. Designed to examine the suitability of various materials for use in power reactors. JUNO, built in 1964. Built from the components of a zero-energy graphite moderated reactor called NERO, and from a sub-critical assembly used for steam generating heavy water reactor investigations, it was used to provide the information needed for the design of small power reactor cores. The Dragon reactor was built in 1964. It was the first power reactor built at Winfrith. It was an experimental reactor built as a European inter-governmental research and development project. It was the first demonstration high-temperature gas-cooled reactor (HTGR) and had a thermal output of 20MW. It operated until 1976. Winfrith Steam Generating Heavy Water Reactor Design The largest reactor at Winfrith was a steam-generating heavy water reactor (SGHWR) commonly known as the Winfrith Reactor. It was designed by the UKAEA, and was intended to combine the features of the CANDU reactor and PWR. The core consisted of a bank of metal pressure tubes (zirconium alloy) which passed through vertical tubes in a tank of heavy water moderator – allowing the designers to do without the pressure vessel that normally contained the reactor's core. The pressure tubes contained the fuel which was cooled by a flow of light water up the tubes, generating steam. The fuel was slightly enriched uranium. The power level was varied by the level of the moderator. The reactor exported up to 100MW of electric power to the National Grid. For many years it was the largest water cooled reactor in the United Kingdom. History Construction of the reactor began in 1963. It began operating in 1967, and was notable for being built within the allotted timescale (four years), and for being under-budget. It was built as a demonstration reactor, with the intention of building a series of commercial reactors based on the design. However, the SGHWR design was never advanced beyond the prototype at Winfrith, and the design was sidelined in favour of AGR reactors. The Winfrith reactor was shut down in 1990. The site today The site is now split between the nuclear licensed site, the extensive Dorset Green Technology Park (formerly Winfrith Technology Centre) and the headquarters of the Dorset Police. Ownership of the Winfrith Nuclear site has now passed to the Nuclear Decommissioning Authority (NDA). The site is managed by Magnox Limited, who are contracted to deliver the site