November 1955: Calder Hall - the word's first nuclear power station 

The UK led the world when it opened the first nuclear power station at Calder Hall. Jason Ford reports.

Calder Hall was officially opened on 17 October 1956 by Queen Elizabeth II. It generated electricity for 47 years before closing in 2003
Calder Hall was officially opened on 17 October 1956 by Queen Elizabeth II. It generated electricity for 47 years before closing in 2003 - The Engineer

Readers of a certain vintage might recall the ‘Nuclear power? No thanks!’ smiling sun logo from the 1970s and ‘80s, but now, given the role of low carbon energy in net zero ambitions, shouldn’t this be amended to ‘Nuclear power? Yes please!’?

Compared to a coal-fired power station, a nuclear plant will use 1kg of uranium to generate the same amount of energy as 2.7 million kg of coal. There are drawbacks to nuclear such as upfront and lifetime costs, plus the question of how to best dispose of spent nuclear fuel. Despite this, a resurgent appetite for nuclear in Westminster via Great British Nuclear, an arms-length body responsible for driving delivery of new nuclear projects, makes it clear that atomic energy is back in the electricity generation game.

It all began at Calder Hall, Cumbria, when the plant’s 65MW dual purpose reactors came online in 1956, making it the world’s first full-scale commercial nuclear power station.

Prior to that momentous occasion, The Engineer reported on progress at the site in the publication’s November 25, 1955, edition.


“It should be appreciated that one of the main reasons for choosing Calder Hall as the site for an atomic power station to generate electricity, as a by-product in the production of plutonium, was because the site adjoins the Windscale plutonium factory,” said The Engineer. “The Calder Hall project could, therefore, make use of the existing services technical skill and ‘know how’ already established at Windscale.”

The Engineer continued: “Two stations, ‘A’ and ‘B’ of similar output are under development at the Calder Hall site. Station ‘A’… is already far advanced; work has been started on station ‘B’ where the foundations for one reactor are nearly completed, while site preparation for the second reactor is in hand. While No. 1 reactor is nearing the final stages of construction, the commissioning process has started.

“According to the present programme, it should be producing power by the end of next year. No. 2 reactor should reach the same stage about six months later. The first of the four 23MW turbo-alternators is at present being installed in the turbine hall, which is between the two reactor buildings.”

It was noted that Calder Hall ‘B’ would be a station of similar layout to the ‘A’ station, with a turbine hall between the two reactor buildings. The Engineer reported that the two stations were being built ‘in tandem’ on the same longitudinal axis. Station ‘B’ would lie to the right of station ‘A’ and was due to be commissioned in1958/59.

“Each reactor is a graphite-moderated, pressurised pile, cooled by carbon dioxide in a closed cycle,” said The Engineer. “After abstracting heat from the reactor core the carbon dioxide enters four heat exchangers in parallel where steam is generated for the turbines.

“The graphite lattice containing the uranium fuel rods and the control rods weighs 1000 tons and is contained in a cylindrical pressure vessel made by Whessoe, Ltd.

“A ‘diagrid’ structure built up of ‘I’-section beams, forming a rectangular lattice or honeycomb bounded by a circular ring girder, carries the weight of the graphite core. The pressure vessel, which is about 60ft high and 40ft in diameter, is built up of 2in mild steel plate welded on site to produce five sections-the bottom dome, the two central ring-shaped sections, the ‘diagrid’ and the upper dome.”

These sections were lifted by a 100-ton crane and lowered through the roof of the pile vault with the final welding done in situ. All butt welds were radiographed and all important fillet welds were examined by crack detection.

It was further observed that stress relieving of the completed pressure vessel was effected by applying radiant heat, involving an electrical load of 1.5MW, raising the temperature to over 550oC, maintaining this condition for about eight hours, and then allowing the vessel to cool slowly. A pneumatic pressure test and a vacuum test at 0·1 atmosphere pressure was then applied.

The weight of the graphite and ‘diagrid’ was taken by brackets directly through the walls of the pressure vessel on to ten inverted ‘A’ -frames, which rested on the base of the thermal shield. The bearing face of each support leg was radiused to allow for radial expansion of the pressure vessel and ‘diagrid.’ The entire pressure vessel was surrounded by a thermal shield built up of 6in thick steel plates laid edgewise to form a lining to the octagonal reinforced-concrete biological shield which was 8ft thick.

The biological shields were constructed by Taylor Woodrow Ltd., the main contractor for the civil engineering work on site.

“There is a 6in space between the thermal shield and the biological shield, and this space is used for induced draught air cooling, the exhaust air being discharged 200ft above ground level from the two stacks mounted on the reactor building,” said The Engineer.

Calder Hall was opened by Queen Elizabeth II and Workington was the first town to receive electricity produced by nuclear power. Designed to operate for 20 years, the power station went onto generate electricity for 47 years before closing in 2003. Decommissioning began in 2005 and an eight year defueling programme was completed in September 2019.