Editing Magnox (section)

==Reactors built==
[[Image:Sizewell A.jpg|thumb|right|[[Sizewell nuclear power stations#Sizewell A|Sizewell A]] magnox nuclear power station]]
In all, 11 power stations totalling 26 units were built in the United Kingdom where the design originated. In addition, one was exported to [[Tōkai Nuclear Power Plant|Tōkai]] in Japan<ref>{{cite journal |url=https://www.fujielectric.com/company/tech_archives/pdf/11-01/FER-11-01-01-1965.pdf |title=Manufacture of Pressure Vessel for Nuclear Power Reactor |author=Tsutomu Nakajima, Kazukiyo Okano and Atsushi Murakami |journal=Fuji Electric Review |volume=11 |number=1 |publisher=Fuji Electric Co |year=1965 |access-date=17 April 2014}}</ref> and another to [[Latina Nuclear Power Plant|Latina]] in Italy.<ref name=grimston-201310/> North Korea also developed their own magnox reactors, based on the UK design which was made public at an [[Atoms for Peace]] conference.

The first magnox power station, [[Sellafield|Calder Hall]], was the world's first nuclear power station to generate electrical power on an industrial scale<ref name=the-engineer /> (a power station in Obninsk, Russia started supplying the grid in very small non-commercial quantities on 1 December 1954). The first connection to the grid was on 27 August 1956, and the plant was officially opened by [[Elizabeth II of the United Kingdom|Queen Elizabeth II]] on 17 October 1956.<ref>{{Cite press release |url=http://www.bnfl.com/index.aspx?page=413 |title=Calder Hall Celebrates 40 Years of Operation |publisher=BNFL |access-date=22 February 2004 |archive-url = https://web.archive.org/web/20040222073030/http://www.bnfl.com/index.aspx?page=413 |archive-date = 22 February 2004}}</ref> When the station closed on 31 March 2003, the first reactor had been in use for nearly 47 years.<ref>{{cite news| url=https://www.theguardian.com/nuclear/article/0,2763,918724,00.html |newspaper=The Guardian | location=London | title=First nuclear power plant to close | first=Paul | last=Brown | date=21 March 2003 | access-date=12 May 2010}}</ref>

The first two stations (Calder Hall and [[Chapelcross nuclear power station|Chapelcross]]) were originally owned by the [[UKAEA]] and primarily used in their early life to produce [[weapons-grade]] [[plutonium]], with two fuel loads per year.<ref>{{cite report|url=http://www.nautilus.org/archives/pub/ftp/napsnet/papers/hayes1193.txt |title=Should the United States Supply Light Water Reactors to Pyongyang?|first=Peter|last=Hayes |date=16 November 1993 |publisher=Nautilus Institute |access-date=21 August 2006 |url-status=dead |archive-url=https://web.archive.org/web/20060307121518/http://www.nautilus.org/archives/pub/ftp/napsnet/papers/hayes1193.txt |archive-date=7 March 2006 }}</ref> From 1964 they were mainly used on commercial fuel cycles and in April 1995 the UK Government announced that all production of plutonium for weapons purposes had ceased.<ref>{{cite web |archive-url=https://web.archive.org/web/20061213032416/http://www.mod.uk/NR/rdonlyres/B31B4EF0-A584-4CC6-9B14-B5E89E6848F8/0/plutoniumandaldermaston.pdf |archive-date=13 December 2006 |url=http://www.mod.uk/NR/rdonlyres/B31B4EF0-A584-4CC6-9B14-B5E89E6848F8/0/plutoniumandaldermaston.pdf |title=Plutonium and Aldermaston – an historical account |publisher=[[UK Ministry of Defence]] |date=4 September 2001 |access-date=15 March 2007}}</ref>

The later and larger units were owned by the [[CEGB]] and operated on commercial fuel cycles.<ref name=dalton-201612>{{cite report |url=http://www.dalton.manchester.ac.uk/media/eps/dalton/documents/Experience-of-Consortia-Engineering-for-Nuclear-Power-Stations.pdf |title=UK Experience of Consortia Engineering for Nuclear Power Stations |author=S H Wearne, R H Bird |publisher=Dalton Nuclear Institute, University of Manchester |date=December 2016 |access-date=25 March 2017 |archive-url=https://web.archive.org/web/20170326135456/http://www.dalton.manchester.ac.uk/media/eps/dalton/documents/Experience-of-Consortia-Engineering-for-Nuclear-Power-Stations.pdf |archive-date=26 March 2017 |url-status=dead }}</ref> However [[Hinkley Point A nuclear power station|Hinkley Point A]] and two other stations were modified so that [[weapons-grade plutonium]] could be extracted [[Nuclear weapons and the United Kingdom|for military purposes]] should the need arise.<ref name=ecologist-20141113>{{cite news |url=http://www.theecologist.org/News/news_analysis/2625877/the_worlds_first_nuclear_proliferation_treaty.html |title=The world's first 'Nuclear Proliferation Treaty' |author=David Lowry |newspaper=Ecologist |date=13 November 2014 |access-date=2 December 2014}}</ref><ref>{{cite web |url=https://api.parliament.uk/historic-hansard/commons/1958/jun/24/atomic-power-stations-plutonium |title=Atomic Power Stations (Plutonium Production) |author=Reginald Maudling |work=[[Hansard|Parliamentary Debates (Hansard)]] |date=24 June 1958 |id=HC Deb 24 June 1958 vol 590 cc246-8 |access-date=2 December 2014 |quote=the Central Electricity Generating Board has agreed to a small modification in the design of Hinkley Point and of the next two stations in its programme so as to enable plutonium suitable for military purposes to be extracted should the need arise.|author-link=Reginald Maudling }}</ref>

===Derating to reduce corrosion===
In early operation it was found that there was significant oxidation of mild steel components by the high temperature carbon dioxide coolant, requiring a reduction in [[operating temperature]] and power output.<ref name=lynceans-20160521>{{cite web |url=https://lynceans.org/all-posts/farewell-magnox-1956-2015/ |title=Farewell Magnox: 1956 - 2015 |last=Lobner |first=Peter |website=The Lyncean Group of San Diego |date=21 May 2016 |access-date=1 June 2021}}</ref> For example, the [[Latina Nuclear Power Plant|Latina reactor]] was derated in 1969 by 24%, from 210{{nbsp}}MWe to 160{{nbsp}}MWe, by the reduction of operating temperature from {{convert|390|to|360|°C}}.<ref name=inis-1989>{{cite journal |url=https://inis.iaea.org/search/search.aspx?orig_q=RN:20085903 |title=Operating experience with the Latina Magnox reactor |last=Volterra |first=E. |website=IAEA |id=IWGGCR-19 |year=1989 |access-date=1 June 2021}}</ref>

=== Last operating magnox reactor ===
The [[Nuclear Decommissioning Authority]] (NDA) announced on 30 December 2015 that [[Wylfa nuclear power station|Wylfa]] Unit 1 – the world's last operating Magnox reactor – was closed. The unit had generated electricity for five years longer than originally planned. Two units at Wylfa were both scheduled to shut down at the end of 2012, but the NDA decided to shut down Unit 2 in April 2012 so that Unit 1 could continue operating in order to fully utilize existing stocks of fuel, which was no longer being manufactured.<ref name=wnn-20151231>{{cite news |url=http://www.world-nuclear-news.org/WR-Worlds-last-operating-Magnox-reactor-closes-31121501.html |title=World's last operating Magnox reactor closes |publisher=World Nuclear News |date=31 December 2015 |access-date=4 January 2016}}</ref>  	

The small 5{{nbsp}}[[MWe]] experimental reactor, based on the magnox design, at [[Yongbyon Nuclear Scientific Research Center|Yongbyon]] in [[North Korea]], continues to operate {{as of|2016|lc=on}}.