This week in 1957: Zero-energy nuclear reactor goes critical

With the world’s first nuclear submarine — America’s USS Nautilus — already three years old and the Russian navy just a year away from launching its own nuclear-attack submarine, The Engineer reported on the effort to bring UK technology up to speed.

‘Neptune, a zero-energy nuclear reactor built at the UK Atomic Energy Research Establishment, Harwell, went critical for the first time on 7 November,’ reported the magazine. ‘Neptune will be used to study in detail the behaviour of neutrons in water-modelled core designs, with specific reference to a pressurised water reactor for submarine propulsion. The reactor will be used to check the design calculations for the land-based prototype submarine reactor, for which civil engineering work has begun at the authority’s establishment at Dounreay.’

The Engineer added: ‘In Neptune, enriched uranium is the fuel and ordinary water is the moderator; no special cooling is required since only a few watts of heat will be generated. The reactor has been designed to allow the rapid assembly of many different kinds of cores. Its core is formed by assembling boxes of fuel-element plates inside a large, heavily shielded aluminium tank containing the water moderator. The water in the tank can be adjusted precisely to any required level and the water level is used as one means of regulating the reactor.’