a civil reactor from materials tested in these reactors during the course of a few months. Other activities and experiments carried out were:physics research such as neutron scattering, chemistry studies, and radioisotopes production used in medical facilities and other industries. Because the twin reactors, PLUTO and DIDO, worked on a continuous basis rotating in and out of operation, there was continued flow of short-lived radioisotopes for hospitals. The radioisotopes generated account for 70% of the UK radioisotopes sold on the international markets. Decommissioning PLUTO reactor went critical in 1957 and reached its end of life in 1990. It is expected to be completely dismantled by 2024. Decommissioning is carried out in three stages, as defined by the International Atomic Energy Agency (IAEA) Standards. It began with the shutdown of the reactor following closure of nuclear plant. The first stage was removing radioactive materials and operational waste. Second stage involved dismantling active and non-active plants but keeping building structure and the reactor shield intact. Stage three involved demolishing building structures, dismantling the reactor core and bio shield, and site cleanup of all radioactive waste to restore site for other purposes. By 1994 and 1995, PLUTO was at stage two decommissioning See also List of nuclear reactors References 1957 establishments in the United Kingdom 1990 disestablishments in the United Kingdom Buildings and structures in Oxfordshire Nuclear research institutes in the United Kingdom Nuclear research reactors Nuclear technology in the United Kingdom Research institutes in Oxfordshire Vale of White Horse