Plutonium production reactors in the UK, France and Russia were, like those at Hanford, based on metallic natural uranium with a graphite moderator. As at Hanford the Russian reactor (at Chelyabinsk) was water cooled but in the UK (Windscale) and in France (Marcoule) the reactors were gas cooled and later formed the basis of the first generation of electricity-producing reactors in these two countries. Only the British went on to develop these into a more advanced gas-cooled commercial type although there were many experimental designs along the way, including high temperature reactors. France gave up gas-cooled designs in favour of light water reactors in the late 1960s. In the UK this did not happen until almost two decades later.

A year after the war had ended, the US Atomic Energy Commission (AEC) was established (August 1946) to control nuclear energy development and foster its peaceful use. Within the AEC programme under the direction of Rear-Admiral Hyman Rickover, ANL in collaboration with Westinghouse developed a reactor for use as a submarine propulsion unit.2 The use of plutonium or highly enriched uranium fuel coupled with a pressurised water coolant allowed the requisite power to be generated from a reactor that was sufficiently small to fit inside the ship’s hull. The keel for USS Nautilus the world’s first nuclear-powered submarine was laid in June 1952 and the ship was launched January 1954. The reactor design was subsequently scaled up for a land-based pressurised water reactor (PWR) and a prototype was constructed at Shippingport, Pennsylvania (230 MW thermal, 60 MW electrical); this went critical in December 1957. This was a joint venture between AEC, Westinghouse (vendor) and Duquense Light Company (utility).

A series of five boiling water reactor experiments (known as BORAX I to V) were designed by ANL and tested at AEC’s Idaho National Reactor Testing Station starting in 1953 and running through to 1964.3 The third experiment (mid-1955) produced enough electricity to power the nearby town of Arco. The first commercial plant (5 MW(e)) was built in 1957 at Vallecitos near San Jose, California. Based on this work, General Electric constructed a 210 MW(e) BWR for Commonwealth Edison at Dresden, Illinois, which started operation in October 1959. It was notable for being the first US reactor to be built without government funding.

Canada has developed, operated and exported its own unique pressurised heavy water reactor (PHWR) design, known as CANDU (see Chapter 11). The original aim was to exploit the country’s large reserves of uranium and to avoid the complications, expense and proliferation risks that are inherent in enrichment and reprocessing. The resulting design maximises neutron economy through the use of a heavy water coolant cum moderator. With non-enriched fuel, maximum burn-up is around 8 GWd/tHM (significantly less than with enriched fuel) but the reactor can be operated with a range of fuel cycles and twelve have been sold and are in operation throughout the world. Two units were sold to India the first of which went into service in 1973 but support from Canada was withdrawn after the testing of India’s nuclear bomb in May 1974. Cooperation effectively began again in 2008 when, with the consent of the IAEA, India reached an agreement with the Nuclear Suppliers Group4 but, in the interim, India had developed its own PHWR variants and investigated their use with thorium fuel.

A particular attraction of the PHWR is the use of pressure tubes to avoid the need for a large, difficult to construct pressure vessel. Similar considerations drove the development of the Soviet RBMK (reaktor bolshoy moshchnosty kanalny, high-power channel reactor) design which, like the early gas-cooled reactors, was based on a military plutonium-producing reactor. The fuel was low enrichment uranium oxide held within sealed Zircaloy tubes. These were placed inside vertical pressure tubes through which flowed pressurised water. The pressure tubes, each about 7 metres long, were located in penetrations through a graphite moderator block.5 A 5 MW prototype produced electricity from 1954 to 1959 at Obninsk, though it continued as a research facility until 2000.6 Later designs, constructed in Russia, Lithuania and Ukraine, were much larger.