Darlington Nuclear Generating Station

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Darlington Nuclear Generating Station
Darlington Nuclear Generating Station panorama2.jpg
LocationClarington, Durham Region, Ontario
Coordinates43°52′22″N 78°43′11″W / 43.87278°N 78.71972°W / 43.87278; -78.71972Coordinates: 43°52′22″N 78°43′11″W / 43.87278°N 78.71972°W / 43.87278; -78.71972
Construction beganUnit 1: April 1, 1982
Unit 2: September 1, 1981
Unit 3: September 1, 1984
Unit 4: July 1, 1985
Commission dateUnit 1: November 14, 1992
Unit 2: October 9, 1990
Unit 3: February 14, 1993
Unit 4: June 14, 1993
Construction cost$14.4 billion CAD ($23 billion in 2020 dollars[1])
Owner(s)Ontario Power Generation (OPG)
Operator(s)Ontario Power Generation (OPG)
Nuclear power station
Reactor typeCANDU PHWR
Reactor supplierAECL
Cooling sourceLake Ontario
Thermal capacity4 × 2776 MWth
Power generation
Units operational4 × 878 MWe (NET)
Make and model4 × CANDU 850
Nameplate capacity3512 MW
Capacity factor63.22% (2017)
82.90% (lifetime)
Annual net output19,451 GWh (2017)
External links
WebsiteDarlington Nuclear
CommonsRelated media on Commons
Darlington Unit 1-4 Capability (Capacity Factor), 2003-2011[2][3][4]

Darlington Nuclear Generating Station is a Canadian nuclear power station located on the north shore of Lake Ontario in Clarington, Ontario. It is a large nuclear facility comprising four CANDU nuclear reactors with a total output of 3,512 MWe (capacity net) when all units are online. It is Canada's second-largest nuclear power plant and provides about 20 percent of Ontario's electricity needs, enough to serve a city of two million people.[5] It is named for the Township of Darlington (now part of Clarington), the name of the municipality in which it is located at the time of its planning.

Construction and operation[edit]

The facility was constructed in stages between 1981 and 1993 by the provincial Crown corporation, Ontario Hydro. Unit 2 was brought online in 1990, Unit 1 in 1992, and Units 3 and 4 in 1993. In April 1999 Ontario Hydro was split into 5 component Crown corporations with Ontario Power Generation (OPG) taking over all electrical generating stations. The Darlington reactors have been among the best performing in OPG's CANDU fleet, including a top year in 2008 in which the plant achieved a combined 94.5% capacity factor.[6] In June 2016, the World Association of Nuclear Operators (WANO) named Darlington one of the safest and top performing nuclear stations in the world - for the third time in a row.[7]

After public hearings, the Canadian Nuclear Safety Commission announced in December 2015 the renewal of Darlington’s power reactor operating licence, for a 10 year period from Jan. 1, 2016 until Nov. 30, 2025, to allow for the refurbishment of the Darlington station, which began in October 2016.[8]

In March 2017, Ontario Power Generation (OPG) and its venture arm, Canadian Nuclear Partners, announced plans to produce Plutonium-238 as a second source for NASA. Rods containing Np-237[9] will be fabricated by Pacific Northwest National Laboratory (PNNL) in Washington State and shipped to OPG's Darlington Nuclear Generating Station where they will be irradiated with neutrons inside the reactor's core to produce Pu-238.[10][11]

Cost overruns[edit]

The Darlington station incurred massive cost overruns during its construction. The initial cost estimate for the station was $3.9 billion CAD in the late 1970s, which increased to $7.4 billion in 1981 when construction was started.[12] A year-long period of public hearings and study by an Ontario government all-party committee finished in 1986 with the decision to proceed with the project, which had then risen to $7 billion in actual and committed costs.[13] The final cost was $14.4 billion CAD, almost double the initial construction budget.[14] The project was adversely affected by declining electricity demand forecasts, mounting debt of Ontario Hydro, and the Chernobyl disaster which necessitated safety reviews in mid-construction. Each delay incurred interest charges on debt, which ultimately accounted for 70% of the cost overruns.[15] Inflation during 1977 to 1981 was 46 percent, according to Canada's Consumer Price index. In addition interest rates were running at 20 percent. Improper choice of equipment and a six-month labour stoppage of electrical workers also yielded some of these costs and delays.[16] Discussion of who is to blame for the costs and subsequent debts associated with Darlington often arise during provincial election campaigns, and are often mentioned in anti-nuclear literature.[17]

Refurbishment project[edit]

On October 14, 2016, OPG began Canada’s largest clean infrastructure project – the refurbishment of all four of Darlington’s reactors. According to the Conference Board of Canada, the $12.8 billion investment will generate $14.9 billion in economic benefits to Ontario, including thousands of construction jobs at Darlington and at some 60 Ontario companies supplying components for the work.[18] The project is scheduled for completion by 2026, and will ensure safe plant operation through 2055.

The first reactor to be refurbished was Unit 2. In March 2020, it was announced that the refurbishment of Unit 2 was complete, and in April 2020, the reactor achieved criticality for the first time since being reassembled.[19][20] The reactor was reconnected to the grid in June.[21]

New build proposal[edit]

In 2006, OPG started the federal approvals process to build new nuclear units at the site of its Darlington Nuclear Station. The project proposal involved the construction and operation of up to four nuclear units, with capacity of up to 4,800 MW.

A request for proposals (RFP) process for design and construction resulted in bids from Areva NP, Westinghouse, and Atomic Energy of Canada Limited (AECL). In June 2009, the Government of Ontario put the RFP process on hold, citing unexpectedly high bids, and the uncertainty surrounding the future of the only compliant bidder (AECL).[22][23][24]

In August 2011, the three-member Joint Review Panel (mandated by the Ontario Ministry of the Environment and the Canadian Nuclear Safety Commission) released a report finding that the Darlington new build project would not result in any significant adverse environmental impacts (after taking into account mitigation measures). Following the report, the federal government approved the Environmental Assessment.[25]

In October 2013, the Ontario government declared that the Darlington new build project would not be a part of Ontario's long term energy plan, citing the high capital cost estimates and energy surplus in the province at the time of the announcement.[26]

In November 2020, Ontario Power Generation (OPG) announced plans to build a small modular reactor (SMR) at Darlington Nuclear Generating Station. It is expected to be operational by 2028 at the earliest.[27][28] OPG will work with GE Hitachi Nuclear Canada to build the SMR.[28]


Low and intermediate level waste from Darlington is stored at the Western Waste Management Facility (WWMF) at the Bruce nuclear site near Kincardine, Ontario. OPG has proposed the construction and operation of a deep geologic repository for the long-term storage of this low and intermediate level waste on lands adjacent to WWMF.

On May 6, 2015 the Joint Review Panel issued the Environmental Assessment (EA) Report recommending the approval of the Deep Geologic Repository for Ontario’s low and intermediate level waste to the federal government.[29]

In February 2016, the Federal Minister of Environment and Climate Change delayed a decision on OPG’s DGR, causing a pause in the timeline for the environmental assessment decision to be issued. OPG has since committed to completing further DGR studies by the end of 2016.[30]

The Darlington Waste Management Facility provides dry storage for the used fuel from Darlington, after an initial period in a water-filled storage bay. The facility was opened in 2007, reportedly on schedule and on budget.[31] The Nuclear Waste Management Organization is seeking a site in Canada for a permanent repository for used fuel from all of Canada's nuclear reactors.


2020: On Tuesday, September 15 Darlington Unit 1 broke the world record for continuous generation at 963 days, a record previous held by Pickering Unit 7 at 894 days for 22 years until it was broken in 2016 by Heysham 2 in the UK. As of September 28, 2020, Unit 1 was at 976 days.[32]
2021: On Thursday, February 4 at sometime after 11PM Darlington Unit 1 finally went down for maintenance after 1,106 continuous days of generation, setting the world nuclear operation record and world thermal plant generation record.[33]

Awards and recognition[edit]

2016: Corporate Community Leadership Award (Community Care Durham - Clarington) [34]

2014: Local Economic Impact Award (Clarington Board of Trade) [35]

2012: Environmental Achievement Award (Environmental Earth Angels) [36]

2011: In December 2011 Darlington achieved 12 million hours without a lost time injury [37]

2009: William H. Howard Conservation, Education and Outreach Award (Wildlife Habitat Council) [38]

2008: International Corporate Habitat of the Year Award (Wildlife Habitat Council) [39]

2007: Performance Improvement Award (Institute of Nuclear Power Operators) [40]

2007: 20th Anniversary Signatures of Sustainability Award (Wildlife Habitat Council)[41]

2005: International Corporate Habitat of the Year Award (Wildlife Habitat Council) [42]


On Dec. 21, 2009, Darlington nuclear staff over-filled a storage tank with lake water. The tank already contained purified (demineralized) water. This resulted in an overflow of about 210,000 liters of water to the environment. The amount of tritium released to the environment was less than 1 percent of the regulatory limit and consistent with normal operational activities.[43]

See also[edit]


  1. ^ 1688 to 1923: Geloso, Vincent, A Price Index for Canada, 1688 to 1850 (December 6, 2016). Afterwards, Canadian inflation numbers based on Statistics Canada tables 18-10-0005-01 (formerly CANSIM 326-0021) "Consumer Price Index, annual average, not seasonally adjusted". Statistics Canada. Retrieved April 17, 2021. and table 18-10-0004-13 "Consumer Price Index by product group, monthly, percentage change, not seasonally adjusted, Canada, provinces, Whitehorse, Yellowknife and Iqaluit". Statistics Canada. Retrieved April 17, 2021.
  2. ^ "Report on 2008 Performance" (PDF). Archived from the original (PDF) on 2013-10-29. Retrieved 2013-10-26.
  3. ^ "OPG 2010 Annual Report" (PDF). Archived from the original (PDF) on 2013-10-29. Retrieved 2013-10-26.
  4. ^ "OPG 2011 Annual Report" (PDF). Archived from the original (PDF) on 2013-10-29. Retrieved 2013-10-26.
  5. ^ "Darlington Nuclear". Archived from the original on 2009-03-26. Retrieved 2009-02-10.
  6. ^ Ferguson, Rob (9 Feb 2010). "'Tune-up' for Pickering, Overhaul at Darlington". Toronto Star. Retrieved 2010-02-10.
  7. ^ "Darlington Nuclear Plant Rated Among the World's Best". www.newswire.ca. Retrieved 2016-07-22.
  8. ^ "CNSC renews the Darlington Nuclear Power Reactor Operating Licence".
  9. ^ United States to ship neptunium to Canada as part of Pu-238 production. International Panel on Fissile Materials. 5 March 2017.
  10. ^ NASA Re-starts PU-238 Production at Two Sites, Neutron Bytes, March 5, 2017
  11. ^ NASA Doesn't Have Enough Nuclear Fuel For Its Deep Space Missions. Ethan Siegel, Forbes. 13 December 2018.
  12. ^ "The Canadian Nuclear FAQ - Section C: Cost and Benefits".
  13. ^ William Walker. "Ontario to complete huge nuclear plant." The Toronto Star, August 21, 1986.
  14. ^ Canadian Press: "Darlington price tag rises to $14.4 billion", The Toronto Star, March 4, 1993.
  15. ^ "The Canadian Nuclear FAQ - Section C: Cost and Benefits".
  16. ^ "Archived copy". Archived from the original on 2011-06-12. Retrieved 2011-10-15.{{cite web}}: CS1 maint: archived copy as title (link)
  17. ^ CBC News http://www.cbc.ca/ontariovotes2003/features/power_091703.html. {{cite news}}: Missing or empty |title= (help)
  18. ^ "Refurbishment of Darlington Nuclear Generating Station Would Boost Economic Activity And Employment". www.conferenceboard.ca. Retrieved 2016-07-22.
  19. ^ "OPG completes first Darlington rebuild : Corporate - World Nuclear News".
  20. ^ "First refurbished Darlington unit starts up : Corporate - World Nuclear News".
  21. ^ "Refurbishment of Canada's Darlington 2 completed - Nuclear Engineering International".
  22. ^ "Darlington plans on hold". World Nuclear News. 29 June 2009. Archived from the original on 3 March 2016. Retrieved 2009-07-16.
  23. ^ Hamilton, Tyler (July 14, 2009). "$26B cost killed nuclear bid". Toronto Star. Retrieved 2009-07-16.
  24. ^ Lawson, Don (February 2012). "CANDU at Darlington: Securing Jobs and Energy for the New Economy" (PDF). CCRE Commentary. Retrieved 2013-10-26.
  25. ^ "Darlington New Build Project Overview". Retrieved 2013-10-26.
  26. ^ ""Ontario nixes building two nuclear reactors" - Global News". Retrieved 2013-10-26.
  27. ^ "OPG Resumes Planning Activities for Darlington New Nuclear".
  28. ^ a b Delitala, Albert (2021-12-03). "Ontario's Darlington nuclear plant to receive first new reactor in decades". Global News. Archived from the original on 2021-12-03. Retrieved 2021-12-03.
  29. ^ "Joint Review Panel Submits Environmental Assessment Report for the Deep Geologic Repository Project". 6 May 2015.
  30. ^ "Ontario Power Generation | OPG Commits to Completing Further DGR Studies". www.opg.com. Retrieved 2016-07-22.
  31. ^ ""News from Ontario Power Generation", Nov 2, 2007" (PDF). Archived from the original (PDF) on 2011-06-12. Retrieved 2010-10-30.
  32. ^ https://www.opg.com/story/darlington-nuclears-unit-1-sets-world-record-for-continuous-operation/
  33. ^ https://www.opg.com/story/darlingtons-unit-1-heads-into-planned-outage-after-record-breaking-run/
  34. ^ "Community Care Durham - News". www.communitycaredurham.on.ca. Archived from the original on 2016-07-14. Retrieved 2016-07-22.
  35. ^ "Clarington Board of Trade - Economic Development Update - Summer 2014 (PDF)" (PDF).
  36. ^ "Ontario Power Generation | Corporate Awards". www.opg.com. Retrieved 2016-07-22.
  37. ^ "OPG "POWERNews", vol. 14, issue 1" (PDF). Archived from the original (PDF) on 2013-10-29. Retrieved 2013-10-26.
  38. ^ "OPG 2010 Sustainable Development Report" (PDF). Archived from the original (PDF) on 2013-12-30. Retrieved 2013-12-28.
  39. ^ "OPG 2009 Sustainable Development Report" (PDF). Archived from the original (PDF) on 2013-12-30. Retrieved 2013-10-26.
  40. ^ ""News from Ontario Power Generation", Dec 4, 2007" (PDF). Archived from the original (PDF) on 2013-10-29. Retrieved 2013-10-26.
  41. ^ "OPG 2009 Sustainable Development Report" (PDF). Archived from the original (PDF) on 2013-12-30. Retrieved 2013-10-26.
  42. ^ "OPG News Release, November 30, 2005". Archived from the original on 2013-10-29. Retrieved 2013-10-26.
  43. ^ "Nuclear plant spills tritium into lake" The Toronto Star. Author Jesse McLean.

External links[edit]