Hunterston B nuclear power station

The construction of Hunterston B was undertaken by a consortium known as The Nuclear Power Group (TNPG).{{cite web |url=http://www.neimagazine.com/journals/Power/NEI/August_2009/attachments/uk_consortia1b.pdf |author=Wearne S H & Bird R H |year=2009 |title=UK Experience of Consortia Engineering for Nuclear Power Stations, School of Mechanical, Aerospace & Civil Engineering, Dalton Nuclear Institute, University of Manchester.}}{{dead link|date=November 2017|bot=InternetArchiveBot|fix-attempted=yes}} The two advanced gas-cooled reactors (AGR) were supplied by TNPG and the turbines by C. A. Parsons & Co.[http://www.industcards.com/nuclear-uk-sc-wl.htm Nuclear Power Plants in the UK - Scotland and Wales] {{webarchive|url=http://arquivo.pt/wayback/20090719124719/http%3A//www.industcards.com/nuclear%2Duk%2Dsc%2Dwl.htm |date=2009-07-19}} Hunterston B began to generate electricity on 6 February 1976.

On 3 December 1977, The Times reported that seawater had entered the reactor through a modification of the secondary cooling system.The Times, Saturday, 3 December 1977; pg. 1; Issue 60177; col D The secondary cooling system used fresh water to cool parts including the bearings of the gas circulators, which circulated the carbon dioxide ({{co2}}) coolant through the reactor to the boilers. 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. 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 £14{{nbsp}}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.

In February 1997, there was concern that contaminated {{co2}} gas from the plant had entered three road tankers and then entered the food chain via soft drinks and beers.{{cite news |url=http://www.heraldscotland.com/sport/spl/aberdeen/nuclear-chief-admits-failure-fear-of-food-risk-1.409436 |title=Nuclear chief admits 'failure'. Fear of food risk |last=Wilson |first=Iain |date=6 March 1997 |work=Herald Scotland |access-date=24 April 2014}}{{cite web |url=http://www.onr.org.uk/periodic-safety-review/huntb.htm |title=Carbon dioxide supply system at Hunterston B Power Station |date=6 October 1998 |access-date=13 October 2016 |archive-date=14 October 2016 |archive-url=https://web.archive.org/web/20161014060753/http://www.onr.org.uk/periodic-safety-review/huntb.htm |url-status=dead}} Carlsberg-Tetley withdrew all its gas cylinders in Scotland as a result of finding contamination in one.{{cite news |url=https://www.independent.co.uk/news/brewery-recalls-co2-cylinders-1271547.html |title=Brewery recalls CO2 cylinders |date=8 March 1997 |work=The Independent |access-date=13 October 2016}}

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 four{{nbsp}}hours. 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 20{{nbsp}}hours. The subsequent investigation made several recommendations: redesign of the insulators on the 400{{nbsp}}kV power lines, installation of an additional 132{{nbsp}}kV power line for emergency power, a second diesel generator building remote from the first, installation of an uninterruptible power supply 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.{{cite web |url=http://www.sfenjg.org/IMG/pdf/AFF2013-B-Cowell-Loss_of_Off_Site_Power_An_Operator_s_Perspective.pdf |title=EDF Energy Loss of Off Site Power: An Operator's Perspective |access-date=2015-03-20 |archive-url=https://web.archive.org/web/20150924100819/http://www.sfenjg.org/IMG/pdf/AFF2013-B-Cowell-Loss_of_Off_Site_Power_An_Operator_s_Perspective.pdf |archive-date=2015-09-24 |url-status=dead }}

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).[http://www.largeassociates.com/3154%20Graphite%20AGR/R3154-Graphite%20FINAL%2028%2006%2006.pdf Large and Associates. Brief Review of the Documents Relating to the Graphite Moderator Cores at Hinkley Point B and Other Advanced Gas-Cooled Reactors, R3154 5 July 2006] {{webarchive |url=https://web.archive.org/web/20061114001807/http://www.largeassociates.com/3154%20Graphite%20AGR/R3154-Graphite%20FINAL%2028%2006%2006.pdf |date=November 14, 2006 }}

Its net electrical output was 1,215{{nbsp}}MW. In 2007, the reactors were restricted to operating at a reduced level of around 70% of full output (around 850{{nbsp}}MWe net). Subsequent work during maintenance shutdowns resulted in Reactor 3 operating at around 82% (540{{nbsp}}Mwe net) in early 2011, and Reactor 4 at around 73% (480{{nbsp}}MWe net). In total this equated to around 1,020{{nbsp}}MWe gross output from the generators. Internal load of 90{{nbsp}}MWe brought net output to approximately 930{{nbsp}}MWe. Hunterston B was capable of supplying the electricity needs of over 1{{nbsp}}million homes.[http://www.edfenergy.com/about-us/energy-generation/nuclear-generation/nuclear-power-stations/hunterston-b.shtml Hunterston B], EDF Energy

Hunterston B was originally planned to operate until 2011. In 2007, planned operation was extended by five years to 2016.{{cite web |url=http://www.upi.com/International_Security/Energy/Briefing/2007/12/11/scotlands_hunterston_b_to_work_until_16/2920/ |archive-url=https://archive.today/20110524172639/http://www.upi.com/International_Security/Energy/Briefing/2007/12/11/scotlands_hunterston_b_to_work_until_16/2920/ |url-status=dead |archive-date=24 May 2011 |title=Scotland's Hunterston B to work until 2016 |publisher=UPI |date=11 December 2007}} In December 2012, EDF said it could (technically and economically) operate until 2023.{{cite news |url=https://www.bbc.co.uk/news/uk-scotland-glasgow-west-20590915 |title=Hunterston B nuclear power plant will run until 2023 |date=4 December 2012 |work=BBC News}}

File:Hunterston B nuclear power station (geograph 5851943).jpg

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.{{cite news |url=https://www.bbc.co.uk/news/uk-scotland-glasgow-west-29502329 |title=Cracks found at Hunterston nuclear power station |date=6 October 2014 |work=BBC News}}

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.{{cite news |url=https://www.bbc.co.uk/news/uk-england-somerset-37789654 |title=Nuclear reactor cracks 'challenge safety case' |work=BBC News |date=31 October 2016 |access-date=31 October 2016}}

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."{{cite news |url=http://www.world-nuclear-news.org/RS-New-cracks-delay-restart-of-Hunterston-B-reactor-0305184.html |title=New cracks delay restart of Hunterston B reactor |publisher=World Nuclear News |date=3 May 2018 |access-date=6 May 2018}}{{cite news |url=https://uk.reuters.com/article/uk-britain-nuclear-edf-analysis/cracks-in-british-nuclear-reactor-ring-power-alarm-bells-idUKKBN1IA2P0 |archive-url=https://web.archive.org/web/20180509221322/https://uk.reuters.com/article/uk-britain-nuclear-edf-analysis/cracks-in-british-nuclear-reactor-ring-power-alarm-bells-idUKKBN1IA2P0 |url-status=dead |archive-date=9 May 2018 |title=Cracks in British nuclear reactor ring power alarm bells |author=Nina Chestney, Susanna Twidale |publisher=Reuters |date=9 May 2018 |access-date=20 November 2018}}

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.{{cite news |url=http://www.world-nuclear-news.org/Articles/Hunterston-B-restarts-delayed-by-several-weeks |title=Hunterston B restarts delayed by several weeks |publisher=World Nuclear News |date=21 December 2018 |access-date=22 December 2018}} 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 {{convert|2|mm|in|frac=32|abbr=on}} 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.{{cite news |url=https://www.theguardian.com/environment/2019/mar/08/photos-cracks-north-ayrshire-hunterston-b-nuclear-reactor |title=Footage of cracks in North Ayrshire nuclear reactor released |newspaper=The Guardian |date=8 March 2019 |access-date=9 March 2019}}{{cite news |url=https://www.bbc.co.uk/news/uk-scotland-47485321 |title=Hunterston B: Pictures show cracks in Ayrshire nuclear reactor |work=BBC News |date=6 March 2019 |access-date=6 March 2019}}

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.{{cite news| title=EDF to restart Hunterston B-7 soon: Corporate - World Nuclear News |url=https://www.world-nuclear-news.org/Articles/EDF-to-restart-Hunterston-B-7-soon |work=www.world-nuclear-news.org |date=27 August 2020}}

Reactor 3 was taken offline for the final time at midday on 26 November 2021.{{cite news |url=https://www.world-nuclear-news.org/Articles/First-Hunterston-B-reactor-enters-retirement |title=First Hunterston B reactor enters retirement |work=World Nuclear News |date=29 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 is expected to take over three years to complete, and it involves the complete emptying of all fuel channels from both reactors. This amounts to over 300 channels from each reactor, each containing 8 fuel elements. 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.{{cite web | url=https://www.world-nuclear-news.org/Articles/Defuelling-operations-begin-at-Hunterston-B | title=Hunterston B defuelling operations begin |website=World Nuclear News |date=19 May 2022}}{{cite news | url = https://www.bbc.co.uk/news/uk-scotland-glasgow-west-59894688 | work = BBC News | date = 7 January 2022 | access-date = 7 January 2022 | title = Hunterston B nuclear power plant closes down after 46 years | first = Kevin | last = Keane}}

In October 2023, the ONR announced that the defuelling of reactor 3 had been completed, and that the defuelling of reactor 4 was to begin "shortly." Defuelling of reactor 4 is due to be completed in 2025.{{cite press release |date=13 September 2024 |title=ONR grants consent to decommission Hunterston B |url=https://www.onr.org.uk/news/all-news/2024/09/onr-grants-consent-to-decommission-hunterston-b/ |publisher=Office for Nuclear Regulation |access-date=25 September 2024}}

Once both reactors have been fully defuelled, EDF Energy will transfer control of the site to the Nuclear Decommissioning Authority to continue the decommissioning process.{{cite press release |date=10 October 2023 |title=Defuelling milestone for Hunterston B |url=https://www.onr.org.uk/news/all-news/2023/10/key-defuelling-milestone-for-hunterston-b/ |publisher=Office for Nuclear Regulation |access-date=23 July 2024}}

{{stack|{{Portal|Scotland|Energy|Nuclear technology}}}}

• Hunterston A nuclear power station nearby, shutdown 1990, now being decommissioned.
• Nuclear power in Scotland
• Nuclear power in the United Kingdom
• Energy policy of the United Kingdom
• Energy use and conservation in the United Kingdom
• Western HVDC Link, a 2.2 GW cable from Hunterston to Wales

{{reflist}}

• [https://www.edfenergy.com/energy/power-stations/hunterston-b Hunterston B nuclear power station]

{{Scottish energy}}

{{British nuclear power plants}}

Category:Former nuclear power stations in Scotland

Category:Nuclear power stations using Advanced Gas-cooled Reactors

Category:Firth of Clyde