Editing CANDU reactor (section)

==Economics==
The neutron economy of heavy-water moderation and precise control of on-line refueling allow CANDU to use a wide range of fuels other than enriched uranium, e.g., natural uranium, reprocessed uranium, [[thorium]], [[plutonium]], and used LWR fuel. Given the expense of enrichment, this can make fuel much cheaper. There is an initial investment into the tonnes of 99.75% pure<ref>{{cite web |url=http://www.nuclearfaq.ca/cnf_sectionA.htm#e |title=Canadian Nuclear FAQ |work=The Canadian Nuclear FAQ by Dr. Jeremy Whitlock |access-date=5 March 2005 |archive-url=https://web.archive.org/web/20131101054647/http://nuclearfaq.ca/cnf_sectionA.htm#e |archive-date=1 November 2013 |url-status=dead }} [http://www.nuclearfaq.ca/cnf_sectionA.htm#e A. CANDU Nuclear Power Technology A.3 What is "heavy water"?]  "'reactor-grade' heavy water, nominally 99.75 wt% deuterium content".</ref> heavy water to fill the core and heat-transfer system. In the case of the Darlington plant, costs released as part of a [[freedom of information act]] request put the [[overnight cost]] of the plant (four reactors totalling 3,512&nbsp;MW<sub>e</sub> net capacity) at $5.117 billion CAD (about US$4.2 billion at early-1990s exchange rates). Total capital costs including interest were $14.319 billion CAD (about US$11.9 billion) with the heavy water accounting for $1.528 billion, or 11%, of this.<ref>[http://www.cleanairalliance.org/files/active/0/DarlingtonFOIresults.pdf "Final and Total Capital Costs of the Darlington Nuclear Generating Station"] {{Webarchive|url=https://web.archive.org/web/20120422220759/http://www.cleanairalliance.org/files/active/0/DarlingtonFOIresults.pdf |date=22 April 2012 }}, Ontario Power Generation, 27 April 2004.</ref>

Since heavy water is less efficient than light water at slowing neutrons,<ref>{{cite book |last1=Lewis |first1=Elmer E. |title=Fundamentals of Nuclear Reactor Physics |date=1 February 2008 |publisher=Academic Press |isbn=978-0-12-370631-7 |page=49 |edition=1}}</ref> CANDU needs a larger moderator-to-fuel ratio and a larger core for the same power output. Although a calandria-based core is cheaper to build, its size increases the cost for standard features like the [[containment building]]. Generally nuclear plant construction and operations are ≈65% of overall lifetime cost; for CANDU, costs are dominated by construction even more. Fueling CANDU is cheaper than other reactors, costing only ≈10% of the total, so the overall price per kWh electricity is comparable. The next-generation [[Advanced CANDU reactor]] (ACR) mitigates these disadvantages by having light-water coolant and using a more compact core with less moderator.

When first introduced, CANDUs offered much better [[capacity factor]] (ratio of power generated to what would be generated by running at full power, 100% of the time) than LWRs of a similar generation. The light-water designs spent, on average, about half the time being refueled or maintained. Since the 1980s, dramatic improvements in LWR outage management{{which?|date=November 2022}} have narrowed the gap, with several units achieving capacity factors ~90% and higher, with an overall US fleet performance of 92% in 2010.<ref>[http://www.nei.org/resourcesandstats/documentlibrary/reliableandaffordableenergy/graphicsandcharts/usnuclearindustrycapacityfactors/ "U.S. Nuclear Industry Capacity Factors (1971–2010)"] {{Webarchive|url=http://arquivo.pt/wayback/20090709004413/http://www.nei.org/resourcesandstats/documentlibrary/reliableandaffordableenergy/graphicsandcharts/usnuclearindustrycapacityfactors/ |date=9 July 2009 }}, Nuclear Energy Institute, 2010.</ref> The latest-generation CANDU 6 reactors have an 88–90% CF, but overall performance is dominated by the older Canadian units with CFs on the order of 80%.<ref>[http://media.cns-snc.ca/nuclear_info/candu_performance.html CANDU Lifetime Performance to 30 September 2009] {{Webarchive|url=https://web.archive.org/web/20120117215048/http://media.cns-snc.ca/nuclear_info/candu_performance.html |date=17 January 2012 }}, Canadian Nuclear Society.</ref> 
Refurbished units had historically demonstrated poor performance, on the order of 65%.<ref>Jack Gibbons, "Darlington Re-Build Consumer Protection Plan", Ontario Clear Air Alliance, 23 September 2010, p. 3.</ref> 
This has since improved with the return of Bruce units A1 and A2 to operation, which have post-refurbishment (2013+) capacity factors of 90.78% and 90.38%, respectively.<ref name="pris_iaea_org">{{Cite web|url=https://pris.iaea.org/PRIS/CountryStatistics/ReactorDetails.aspx?current=53|title=IAEA Power Reactor Data|date=4 October 2022|website=IAEA Power Reactor Data|language=en|access-date=5 October 2022}}</ref>

Some CANDU plants suffered from [[Darlington Nuclear Generating Station#Cost overruns|cost overruns]] during construction, often from external factors such as government action.<ref>{{cite web |url=http://www.cbc.ca/ontariovotes2003/features/power_091703.html |title=Ontario Votes 2003 – Features – Who's got the power? |publisher=CBC}}</ref> For instance, imposed construction delays led to roughly a doubling of the cost of the Darlington Nuclear Generating Station near Toronto, Ontario. Technical problems and redesigns added about another billion to the resulting $14.4 billion price.<ref>[http://www.magma.ca/~jalrober/CANcosts.htm "Can CANDU estimates be trusted?"] {{Webarchive|url=https://web.archive.org/web/20070206172421/http://www.magma.ca/~jalrober/CANcosts.htm |date=6 February 2007 }} by J. A. L. Robertson (2004).</ref> In 2002 two CANDU 6 reactors at Qinshan in China were completed on-schedule and on-budget, an achievement attributed to tight control over scope and schedule.<ref>{{cite web| url = https://canteach.candu.org/Content%20Library/20031701.pdf| title = Qinshan CANDU Project Construction Experiences}}</ref>
[[File:Pickering-nuclear-generating-station-001.jpg|upright=3|thumb|center|alt=Pickering Nuclear Generating Station| [[Pickering Nuclear Generating Station]] The station consists of four operating and four shut down CANDU reactors housed in domed containment buildings. The cylindrical Vacuum Building is an additional safety system where steam is condensed in the event of a major leak.]]