The initial steps that led to the formation of Winfrith began with the creation of the United Kingdom Atomic Energy Authority (AEA) from the former
Atomic Energy Research Establishment (AERE) in 1954.
John Cockcroft, in charge of the Research Group, immediately began pressing for a new site to be set aside for the construction of multiple experimental reactors, with the aim being to try many designs in order to develop the best possible commercial systems. This was opposed by
Christopher Hinton, of the Industrial Group, who wanted to pick a single design and focus their energies on that. Cockcroft eventually won the acrimonious argument. The site in Dorset was selected and led to the formation of the opposition group, the Dorset Land Resources Committee, led by
Colonel Joseph Weld. The AEA were granted
planning permission for the development by
Dorset County Council, which was confirmed by a public inquiry, but during the process it was discovered that various
rights of common may have existed over the land. In order to enable the development to go ahead as quickly as possible, the government introduced, and Parliament passed, the Winfrith Heath Act 1957, extinguishing any rights of common over the land, and allowing for a compensation process for any commoners whose rights had been extinguished. The AEA acquired by compulsory purchase order and another similar size through normal purchases to bring the site to acres. To house the staff, they also purchased 153 homes in
Bournemouth and
Poole for staff to rent, as well as 127 in
Weymouth, 100 in
Dorchester, 24 in
Wareham and 12 in
Wool. The Durley Hall Hotel at Branksome Chine was bought in 1958 for single staff and temporary accommodation. Construction began in 1957, and the first low-energy reactor, ZENITH, was completed and in operation by the end of 1959. 1959 also marked the commencement of the five mile pipeline to the sea at Arish Mell Many others followed. Cockcroft also suggested that larger
fusion reactors be built at Winfrith, but this was met by serious pushback from the scientists involved in the programme. This work instead moved to today's
Culham Centre for Fusion Energy. Staffing peaked at 2,350 in 1966, but the site slowly wound down and the staff was 1,800 by 1978. The largest reactor at the site (SGHWR), closed in 1990, and the site turned primarily to disposal of nuclear waste. In 1995, the eastern part of the site became the Winfrith Technology Centre, and on the western side were decommissioned. The last reactor was shut down in 1995, with decommissioning of the site scheduled to finish 2021. However the process of decommissioning is ongoing as of 2025 with a public consultation being held about how to proceed with the decommissioning and disposal of waste from the two remaining reactors. The consultation is scheduled to finish in autumn 2026. The consultation is around the burial of low level radioactive waste on the site in the underground basements of the two remaining reactors. Winfrith housed several experimental reactors during its lifetime. There were also impact test facilities, and a used nuclear fuel examination facility with the associated hot cells. Experimental reactors included: • ZENITH (Zero Energy High Temperature Reactor) built in 1959. It was a zero-energy reactor which was used to study the physics of high temperature reactors. • NESTOR (Neutron Source Thermal Reactor) built in 1961. Based on the
JASON reactor operated by the
Hawker Siddeley Nuclear Power Corporation at
Langley, Berkshire. NESTOR was a small research reactor which produced a large amount of neutrons making it a useful tool for investigating the design of power-producing reactors and carrying out sub-critical experiments on core assemblies. It was moved to Winfrith in 1962 and extensively modified and rebuilt for studies of the physics of reactor systems moderated by light or heavy water and by an organic moderator. • ZEBRA (Zero Energy Breeder Reactor Assembly) built in 1962. Designed for studying the neutron physics of a wide variety of fuel assemblies containing uranium and plutonium. • HECTOR (Hot Enriched Carbon-moderated Thermal 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==