Hunterston B nuclear power station is a shut-down AGR
nuclear power station
A nuclear power plant (NPP), also known as a nuclear power station (NPS), nuclear generating station (NGS) or atomic power station (APS) is a thermal power station in which the heat source is a nuclear reactor. As is typical of thermal power st ...
in
North Ayrshire
North Ayrshire (, ) is one of 32 Council areas of Scotland, council areas in Scotland. The council area borders Inverclyde to the north, Renfrewshire and East Renfrewshire to the northeast, and East Ayrshire and South Ayrshire to the east and s ...
, Scotland. Located about south of
Largs
Largs () is a town on the Firth of Clyde in North Ayrshire, Scotland, about from Glasgow. The original name means "the slopes" (''An Leargaidh'') in Scottish Gaelic.
A popular seaside resort with a pier, the town markets itself on its histor ...
and about northwest of
West Kilbride
West Kilbride () is a village and historic parish in North Ayrshire, Scotland, on the west coast by the Firth of Clyde, looking across the Firth of Clyde to Goat Fell and the Isle of Arran. West Kilbride and adjoining districts of Seamill and P ...
on the
Firth of Clyde
The Firth of Clyde, is the estuary of the River Clyde, on the west coast of Scotland. The Firth has some of the deepest coastal waters of the British Isles. The Firth is sheltered from the Atlantic Ocean by the Kintyre, Kintyre Peninsula. The ...
coast. It is currently operated by
EDF Energy. The station began producing electricity in 1976, and was permanently shut down in 2022.
[
Hunterston B is similar in design to sister station Hinkley Point B, which ceased operations in August 2022.
]
History
The construction of Hunterston B was undertaken by a consortium known as The Nuclear Power Group (TNPG). The two advanced gas-cooled reactor
The advanced gas-cooled reactor (AGR) is a type of nuclear reactor designed and operated in the United Kingdom. These are the generation II reactor, second generation of British gas-cooled reactors, using Nuclear graphite, graphite as the neutron ...
s (AGR) were supplied by TNPG and the turbines by C. A. Parsons & Co.[Nuclear Power Plants in the UK - Scotland and Wales]
Hunterston B began to generate electricity
Electricity is the set of physical phenomena associated with the presence and motion of matter possessing an electric charge. Electricity is related to magnetism, both being part of the phenomenon of electromagnetism, as described by Maxwel ...
on 6 February 1976.
On 3 December 1977, ''The Times
''The Times'' is a British Newspaper#Daily, daily Newspaper#National, national newspaper based in London. It began in 1785 under the title ''The Daily Universal Register'', adopting its modern name on 1 January 1788. ''The Times'' and its si ...
'' reported that seawater had entered the reactor through a modification of the secondary cooling system. The secondary cooling system used fresh water to cool parts including the bearings of the gas circulators, which circulated the carbon dioxide () coolant through the reactor to the boilers. A small leak of through a seal had developed, and a bypass pipe was installed to remove the water contaminated with to the seawater cooling ponds. When maintenance work was carried out on the reactor and the pressure in the gas cooling system was reduced, sea water was able to flow back up this bypass pipe and into the reactor. The residual heat of the reactor was such that the seawater evaporated rapidly, leaving deposits of salt in the reactor around the gas circuit.
It was estimated at the time that the reactor could be out of operation for a year, that the repairs could cost £14million, 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.
In February 1997, there was concern that contaminated gas from the plant had entered three road tankers and then entered the food chain via soft drinks and beers. Carlsberg-Tetley withdrew all its gas cylinders in Scotland as a result of finding contamination in one.
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. Normally, in the absence of power for the reactor cooling pumps, the reactor would be passively cooled. However, the emergency control system which would have initiated passive cooling failed to act, as it had not been reset. Reactor cooling was reinstated after fourhours. There was considerable confusion and delay in restoring power as plant schematics and security systems were computerised but were rendered inoperable due to lack of electrical power.
Due to the inherent safety margins of the AGR reactor design, there was no reactor damage, and the plant would have tolerated loss of cooling for 20hours. The subsequent investigation made several recommendations: redesign of the insulators on the 400kV power lines, installation of an additional 132kV power line for emergency power, a second diesel generator building remote from the first, installation of an uninterruptible power supply
An uninterruptible power supply (UPS) or uninterruptible power source is a type of continual power system that provides automated backup electric power to a electrical load, load when the input power source or mains electricity, mains power fai ...
for the reactor safety systems and for essential computer equipment, provision of hard copy plant schematics and emergency protocols, and revised staff training procedures including simulation of multiple simultaneous system failures.
In 2006, concerns were raised in a report commissioned by Greenpeace
Greenpeace is an independent global campaigning network, founded in Canada in 1971 by a group of Environmental movement, environmental activists. Greenpeace states its goal is to "ensure the ability of the Earth to nurture life in all its biod ...
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).
Its net electrical output was 1,215MW. In 2007, the reactors were restricted to operating at a reduced level of around 70% of full output (around 850MWe net). Subsequent work during maintenance shutdowns resulted in Reactor 3 operating at around 82% (540Mwe net) in early 2011, and Reactor 4 at around 73% (480MWe net). In total this equated to around 1,020MWe gross output from the generators. Internal load of 90MWe brought net output to approximately 930MWe. Hunterston B was capable of supplying the electricity needs of over 1million homes.[ ''Hunterston B''](_blank)
EDF Energy
Hunterston B was originally planned to operate until 2011. In 2007, planned operation was extended by five years to 2016. In December 2012, EDF said it could (technically and economically) operate until 2023.
Graphite core keyway root cracks
In October 2014, it was reported that cracks had been found in one of the reactors at the plant following routine inspections which began in August 2014. Two of about 3,000 graphite bricks in the core of reactor four at Hunterston were affected. The plant's operator, EDF Energy, said the cracking was predicted to occur as the station ages and said that the issue would not affect the safe operation of the reactor.
In October 2016, it was announced that super-articulated control rods would be installed in the reactor because of concerns about the stability of the reactors' graphite cores. 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. Super-articulated control rods should be insertable even into a destabilised core.
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."
In December 2018, EDF pushed back their estimated return to service date to March 2019 for Reactor 4 and April 2019 for Reactor 3, to allow for further modelling work and a new seismic analysis. In March 2019, pictures of the cracking were released with EDF stating that it intended to seek permission from the ONR to restart reactor 3 by raising the operational limit for the number of cracks. About 370 fractures were discovered, on average wide, in about 10% of the graphite bricks in the reactor core. This was above the operational limit of 350 fractures, and EDF intended to present a new safety case for an operational limit of 700 cracks.
One reactor was restarted on 25 August 2019 then shut down again on 10 December 2019. In August 2020, EDF received regulatory approval to restart the two reactors, in August and September 2020 respectively, before moving to defuel and decommission the plant starting no later than 7 January 2022.
Closure, defuelling and decommissioning
Reactor 3 was taken offline for the final time at midday on 26 November 2021. Reactor 4 was shut down at midday on 7 January 2022, ending 46 years of generation at the station.[
On 19 May 2022, EDF announced that defueling had started on the two Hunterston B units. This process was expected to take over three years to complete, and it involved the complete emptying of all fuel channels from both reactors. This amounted to over 300 channels from each reactor, each containing 8 fuel elements. Fully loaded flasks containing the used fuel were dispatched from the site by rail to ]Sellafield
Sellafield, formerly known as Windscale, is a large multi-function nuclear site close to Seascale on the coast of Cumbria, England. As of August 2022, primary activities are nuclear waste storage, nuclear waste processing and storage and nucle ...
at a maximum rate of three per week.
The ONR announced in October 2023 that the defuelling of reactor 3 had been completed, and in April 2025 that the defuelling of reactor 4 had been completed. The latter announcement was followed by the Hunterston B site being declared 'nuclear fuel free'.
Following both reactors being fully defuelled, EDF Energy will transfer control of the site to the Nuclear Decommissioning Authority (NDA)'s subsidiary Nuclear Restoration Services to start the decommissioning process. As of April 2025, the NDA is scheduled to assume control of the Hunterston B site in spring 2026.
See also
* Hunterston A nuclear power station nearby, shutdown 1990, now being decommissioned.
*Nuclear power in Scotland
Scotland has a long history of nuclear research and electricity generation. Work started on the Dounreay reactor in 1955.
Four other sites provided electricity to the National Grid in Scotland, however generation ceased at Hunterson A in 1990 a ...
*Nuclear power in the United Kingdom
Nuclear power in the United Kingdom generated 16.1% of the country's electricity in 2020. , the UK has five operational nuclear reactors at four locations (4 advanced gas-cooled reactors (AGR) and one pressurised water reactor (PWR)), producin ...
* Energy policy of the United Kingdom
*Energy use and conservation in the United Kingdom
Total energy consumption in the United Kingdom was 142.0million tonnes of oil equivalent (1,651TWh) in 2019. In 2014, the UK had an energy consumption ''per capita'' of 2.78tonnes of oil equivalent (32.3MWh) compared to a world average of 1 ...
* Western HVDC Link, a 2.2 GW cable from Hunterston to Wales
References
External links
Hunterston B nuclear power station
{{British nuclear power plants
Former nuclear power stations in Scotland
Nuclear power stations using Advanced Gas-cooled Reactors
Firth of Clyde