[4] The two advanced gas-cooled reactors (AGR) were supplied by TNPG and the turbines by C. A. Parsons & Co.[5] Hunterston B began to generate electricity on 6 February 1976.

A small leak of CO2 through a seal had developed, and a bypass pipe was installed to remove the water contaminated with CO2 to the seawater cooling ponds.

It was estimated at the time that the reactor could be out of operation for a year, that the repairs could cost £14 million, and that electricity tariffs would have to rise by between 1 and 2 per cent.

Extensive modelling work was performed in the Nuclear Power Company's (NPC) Whetstone, Leicestershire, fluid flow laboratories to determine where the salt would have been deposited, and the salt was successfully removed by technicians using vacuum cleaners and the plant returned to operation.

[9] In December 1998, an INES Level 2 incident occurred after severe winds and sea spray disabled all four power lines to the site during the Boxing Day Storm of 1998.

After multiple grid failures in a short period of time, emergency diesel generators failed to start.

[10] In 2006, concerns were raised in a report commissioned by Greenpeace that the graphite moderator core in each of the twin reactors at Hunterston B might have developed structural problems in the form of cracking of the bricks (as at similar AGR power stations).

The Office for Nuclear Regulation (ONR) had raised concerns over the number of fractures in keyways that lock together the graphite bricks in the core.

An unusual event, such as an earthquake, might destabilise the graphite so that ordinary control rods that shut the reactor down could not be inserted.

[16] In early 2018, a higher rate of new keyway root cracks than modelled was observed in Reactor 3 during a scheduled outage, and EDF announced in May 2018: "While Hunterston B Reactor 3 could return to operation from the current outage, it will remain offline while the company works with the regulator to ensure that the longer term safety case reflects the findings of the recent inspections and includes the results obtained from other analysis and modelling.

Fully loaded flasks containing the used fuel are scheduled to be dispatched from the site by rail to Sellafield at a maximum rate of three per week.