DIDO

DIDO was a materials testing nuclear reactor at the Atomic Energy Research Establishment in Harwell, Oxfordshire. It used enriched uranium metal fuel and heavy water as both neutron moderator and primary coolant. A graphite neutron reflector surrounded the core. In the design phase it was known as AE334 after its engineering design number. The reactor was built to provide a high neutron flux for faster testing of materials for nuclear power reactors. Its high neutron flux also produced intense beams for neutron diffraction studies. DIDO reached first criticality in 1956 and operated until it was shut down in 1990. Six reactors of the same DIDO class were constructed worldwide. They included PLUTO at Harwell, HIFAR in Australia, DMTR in Scotland, DR-3 in Denmark and FRJ-II in Germany. Visitors to the Harwell site find the former DIDO building among other research facilities. The reactor’s heavy-water systems and graphite reflector remain part of its preserved structure. The site also contains related laboratories and equipment from the Atomic Energy Research Establishment. The reactor’s shutdown and planned decommissioning mark the end of its operational life. Its legacy includes the six DIDO-class reactors spread across five countries.