generation II reactor

{{Short description|Design classification for nuclear reactors}}

File:Gen II nuclear reactor vessels sizes.svg

A generation II reactor is a design classification for a nuclear reactor, and refers to the class of commercial reactors built until the end of the 1990s. Prototypical and older versions of PWR, CANDU, BWR, AGR, RBMK and VVER are among them.{{cite book|last=Jamasb|first=Tooraj |author2=William J. Nuttall |author3=Michael G. Pollitt |title=Future electricity technologies and systems|publisher=Cambridge University Press|year=2006|edition=illustrated|pages=203|isbn= 978-0-521-86049-9}}

These are contrasted to {{vanchor|generation I}} reactors, which refer to the early prototype of power reactors, such as Shippingport, Magnox/UNGG, AMB, Fermi 1, and Dresden 1. The last commercial Gen I power reactor was located at the Wylfa Nuclear Power Station{{cite web |url=http://www.amacad.org/pdfs/nuclearreactors.pdf |title=Nuclear Reactors: Generation to Generation |author=Stephen M. Goldberg and Robert Rosner |date=2011 |publisher=American Academy of Arts and Sciences |access-date=1 September 2018 |quote=The only remaining commercial Gen I plant, the Wylfa Nuclear Power Station in Wales, was scheduled for closure in 2010. However, the UK Nuclear Decommissioning Authority announced in October 2010 that the Wylfa Nuclear Power Station will operate up to December 2012.}} and ceased operation at the end of 2015. The nomenclature for reactor designs, describing four 'generations', was proposed by the US Department of Energy when it introduced the concept of generation IV reactors.

The designation generation II+ reactor is sometimes used for modernized generation II designs built post-2000, such as the Chinese CPR-1000, in competition with more expensive generation III reactor designs. Typically, the modernization includes improved safety systems and a 60-year design life.{{Citation needed|date=November 2011}}

Generation II reactor designs generally had an original design life of 30 or 40 years.{{cite book |title=Cost Estimate Guidelines for Advanced Nuclear Power Technologies |date=May 1993 |publisher=Oak Ridge National Laboratories |location=Oak Ridge, Tennessee |pages=43–45 |doi=10.2172/10176857 |edition=ORNL/TM-10071/R3 |url=https://www.osti.gov/servlets/purl/10176857/ |access-date=9 September 2020|last1=Delene |first1=J.G. |last2=Hudson |first2=C.R. II }} This date was set as the period over which loans taken out for the plant would be paid off. However, many generation II reactors are being life-extended to 50 or 60 years, and a second life-extension to 80 years may also be economical in many cases.{{cite news|url=http://www.neimagazine.com/story.asp?sectionCode=132&storyCode=2057693 |title=No reason why NPPs cannot live beyond 60 |publisher=Nuclear Engineering International |date=1 October 2010 |access-date=14 October 2010 |url-status=dead |archive-url=https://web.archive.org/web/20110613091957/http://www.neimagazine.com/story.asp?sectionCode=132&storyCode=2057693 |archive-date=13 June 2011 }} By 2013 about 75% of still operating U.S. reactors had been granted life extension licenses to 60 years.{{cite news |url=http://www.world-nuclear-news.org/C_Renewal_a_bridge_to_replacement_1912131.html |title=Renewal a bridge to replacement |publisher=World Nuclear News |date=19 December 2013 |access-date=21 December 2013}}

Chernobyl's No.4 reactor that exploded was a generation II reactor, specifically RBMK-1000.

Fukushima Daiichi's three destroyed reactors were generation II reactors; specifically Mark I Boiling water reactors (BWR) designed by General Electric.

In 2016, unit 2 at the Watts Bar Nuclear Generating Station came online and is likely to be the last generation II reactor to become operational in the United States.