A research and experimental establishment intended to address all aspects of the use of atomic energy was set up at former RAF Harwell in 1946 with JD Cockcroft as director responsible directly to the Minister of Supply. Prior to 1946 Britain's effective contribution to such research had been made by the seconding of research teams to the US atomic energy project and by co-operation with the Government of Canada in developing the Chalk River Laboratories of the National Research Council.
The existing buildings of the Harwell airfield were converted into Physics, Chemistry, Engineering and Biological Laboratories and building began on GLEEP (Graphite Low Energy Experimental Pile) and BEPO (British Experimental Pile). Much of the early work was carried out on behalf of the atomic factories then being established. Pure research as well as project-orientated research was carried out, and Harwell maintained close contact with universities working in the atomic field.
In 1954, following the Atomic Energy Act, the establishment at Harwell became the research establishment division of the UK Atomic Energy Authority.
After 1959, following safety measures taken in the wake of the incident at Windscale, the division became the site of for the Radiological Protection Division of the Authority's Health and Safety Branch.
Under the Science and Technology Act 1965, Harwell, like other branches of the authority, was empowered to diversify its activities and to undertake non-nuclear work, such as research for government departments. The Radiochemical centre at Amersham, established in 1946 under public ownership for the processing and marketing of radioactive isotopes, was run as an out-station of Harwell from 1950. In 1971 it split away from the authority to form an independent company, the Radiochemical Centre Ltd, subsequently Amersham International plc, privatised in 1982.
Three new research stations were established as satellites of Harwell: Winfrith, concerned with reactor research was created in 1957; Harwell's isotope school, was moved to the Wantage Radiation Laboratory in 1959, where research into the practical uses of irradiation was carried out; and the Culham Laboratory became the centre for thermonuclear fusion research. The Wantage Laboratory was closed in 1970 and its work and personnel were transferred to Harwell.
In April 1974, an Energy Technology Support Unit was established at Harwell to assess the various options and to formulate relevant programmes of research and development in the field of non-nuclear research. On behalf of the Department of Energy, Harwell conducted research on all aspects of energy. It became the largest of the authority's research laboratories. Its main efforts were concentrated on problems of reactor development and nuclear power generally, with particular reference to materials research.