CANDU reactor - Revision history

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energy>Luisa at 15:33, 16 October 2021

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	[[fr:Réacteur CANDU]]		[[fr:Réacteur CANDU]]
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			[[es:Reactor CANDU]]
	[[File:Bruce-Nuclear-Szmurlo.jpg\|250px\|thumb\|Figure 1. The Bruce nuclear plant in Ontario uses 8 heavy water CANDU reactors, the most by any nuclear power plant in the world.<ref>Wikimedia Commons [Online], Available: http://en.wikipedia.org/wiki/CANDU_reactor#/media/File:Bruce-Nuclear-Szmurlo.jpg</ref>]]		[[File:Bruce-Nuclear-Szmurlo.jpg\|250px\|thumb\|Figure 1. The Bruce nuclear plant in Ontario uses 8 heavy water CANDU reactors, the most by any nuclear power plant in the world.<ref>Wikimedia Commons [Online], Available: http://en.wikipedia.org/wiki/CANDU_reactor#/media/File:Bruce-Nuclear-Szmurlo.jpg</ref>]]

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energy>Ethan.boechler at 17:45, 18 June 2021

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	[[Category:Done 2016-01-15]]		[[Category:Done 2016-01-15]]
			[[Category:Translated to French]]
			[[fr:Réacteur CANDU]]
	[[File:Bruce-Nuclear-Szmurlo.jpg\|250px\|thumb\|Figure 1. The Bruce nuclear plant in Ontario uses 8 heavy water CANDU reactors, the most by any nuclear power plant in the world.<ref>Wikimedia Commons [Online], Available: http://en.wikipedia.org/wiki/CANDU_reactor#/media/File:Bruce-Nuclear-Szmurlo.jpg</ref>]]		[[File:Bruce-Nuclear-Szmurlo.jpg\|250px\|thumb\|Figure 1. The Bruce nuclear plant in Ontario uses 8 heavy water CANDU reactors, the most by any nuclear power plant in the world.<ref>Wikimedia Commons [Online], Available: http://en.wikipedia.org/wiki/CANDU_reactor#/media/File:Bruce-Nuclear-Szmurlo.jpg</ref>]]

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2016-02-18T04:31:03Z

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Jmdonev at 20:23, 22 December 2015

2015-12-22T20:23:12Z

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	[[Category:Done ~~2015~~-10-15]]		[[Category:Done 2016-01-15]]
	[[File:Bruce-Nuclear-Szmurlo.jpg\|250px\|thumb\|Figure 1. The Bruce nuclear plant in Ontario uses 8 heavy water CANDU reactors, the most by any nuclear power plant in the world.<ref>Wikimedia Commons [Online], Available: http://en.wikipedia.org/wiki/CANDU_reactor#/media/File:Bruce-Nuclear-Szmurlo.jpg</ref>]]		[[File:Bruce-Nuclear-Szmurlo.jpg\|250px\|thumb\|Figure 1. The Bruce nuclear plant in Ontario uses 8 heavy water CANDU reactors, the most by any nuclear power plant in the world.<ref>Wikimedia Commons [Online], Available: http://en.wikipedia.org/wiki/CANDU_reactor#/media/File:Bruce-Nuclear-Szmurlo.jpg</ref>]]

	<onlyinclude>'''CANDU reactor''' is a type of [[nuclear reactor]] which was developed in Canada, and is currently used in [[nuclear power plant]]s for [[electrical generation]] in various countries around the world. CANDU stands for CANada Deuterium Uranium, which reflects the key role of [[deuterium]], or [[heavy water]], to acts as the reactor's [[neutron moderator]], a unique trait of the CANDU.</onlyinclude><ref name=hl>D. Jackson and H. Tammemagi, "CANDU, The Canadian Reactor" in ''Half-Lives: A Guide to Nuclear Technology in Canada'' 1st ed., Canada: Oxford University Press, 2009, ch.6, pp.75-90</ref> The reactors are also different from other reactors because are designed to utilize natural [[uranium]] as a [[fuel]] (as opposed to [[uranium enrichment\|enriched uranium]]).<ref name=Ref2>CANDU Owners Group, "CANDU Reactors: What is CANDU?," 2012. [Online]. Available: http://www.candu.org/candu_reactors.html</ref>		<onlyinclude>'''CANDU reactor''' is a type of [[nuclear reactor]] which was developed in Canada, and is currently used in [[nuclear power plant]]s for [[electrical generation]] in various countries around the world. CANDU stands for CANada Deuterium Uranium, which reflects the key role of [[deuterium]], or [[heavy water]], which acts as the reactor's [[neutron moderator]], a unique trait of the CANDU.</onlyinclude><ref name=hl>D. Jackson and H. Tammemagi, "CANDU, The Canadian Reactor" in ''Half-Lives: A Guide to Nuclear Technology in Canada'' 1st ed., Canada: Oxford University Press, 2009, ch.6, pp.75-90</ref> The reactors are also different from other reactors because they are designed to utilize natural [[uranium]] as a [[fuel]] (as opposed to [[uranium enrichment\|enriched uranium]]).<ref name=Ref2>CANDU Owners Group, "CANDU Reactors: What is CANDU?," 2012. [Online]. Available: http://www.candu.org/candu_reactors.html</ref>

	The use of these reactors in power plants in Canada provide the country with around 15% of its total [[electricity]] with 19 currently in operation.<ref>IEA (2014), "World energy balances", IEA World Energy Statistics and Balances (database). DOI: http://dx.doi.org/10.1787/data-00512-en (Accessed February 2015)</ref><ref name=wna>World Nuclear Association. (June 6 2015). ''Nuclear Power in Canada'' [Online], Available: http://www.world-nuclear.org/info/Country-Profiles/Countries-A-F/Canada--Nuclear-Power/</ref> 12 CANDU reactors are also in use in China, South Korea, Romania, India, Pakistan and Argentina.<ref name=wna/>		The use of these reactors in power plants in Canada provide the country with around 15% of its total [[electricity]] with 19 currently in operation.<ref>IEA (2014), "World energy balances", IEA World Energy Statistics and Balances (database). DOI: http://dx.doi.org/10.1787/data-00512-en (Accessed February 2015)</ref><ref name=wna>World Nuclear Association. (June 6 2015). ''Nuclear Power in Canada'' [Online], Available: http://www.world-nuclear.org/info/Country-Profiles/Countries-A-F/Canada--Nuclear-Power/</ref> 12 CANDU reactors are also in use in China, South Korea, Romania, India, Pakistan and Argentina.<ref name=wna/>

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Jmdonev at 03:10, 26 October 2015

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	[[Category:Done 2015-07-24]]		[[Category:Done 2015-10-15]]
	[[File:Bruce-Nuclear-Szmurlo.jpg\|250px\|thumb\|Figure 1. The Bruce nuclear plant in Ontario uses 8 heavy water CANDU reactors, the most by any nuclear power plant in the world.<ref>Wikimedia Commons [Online], Available: http://en.wikipedia.org/wiki/CANDU_reactor#/media/File:Bruce-Nuclear-Szmurlo.jpg</ref>]]		[[File:Bruce-Nuclear-Szmurlo.jpg\|250px\|thumb\|Figure 1. The Bruce nuclear plant in Ontario uses 8 heavy water CANDU reactors, the most by any nuclear power plant in the world.<ref>Wikimedia Commons [Online], Available: http://en.wikipedia.org/wiki/CANDU_reactor#/media/File:Bruce-Nuclear-Szmurlo.jpg</ref>]]

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	*'''Equipped with an ample supply of light water''' so that in the event of a LOCA, cool light water can be quickly mixed with the overheating heavy water coolant to promptly bring the system back down to proper operating temperatures.<ref name=Ref6/> This is only used as a last resort as mixing the light and heavy water would mean having to re-purify the heavy water coolant.		*'''Equipped with an ample supply of light water''' so that in the event of a LOCA, cool light water can be quickly mixed with the overheating heavy water coolant to promptly bring the system back down to proper operating temperatures.<ref name=Ref6/> This is only used as a last resort as mixing the light and heavy water would mean having to re-purify the heavy water coolant.

	For more information on CANDU reactors please ~~see [~~nuclearfaq.ca ~~Jeremy Whitlock's website]~~ or download a pdf of the e-book [http://teachnuclear.ca/wp-content/uploads/2013/05/Half-Lives14.pdf Half-lives].		For more information on CANDU reactors please visit www.nuclearfaq.ca or download a pdf of the e-book [http://teachnuclear.ca/wp-content/uploads/2013/05/Half-Lives14.pdf Half-lives].

	==References==		==References==
	{{reflist}}		{{reflist}}
	[[Category:Uploaded]]		[[Category:Uploaded]]

J.williams: 1 revision imported

2015-08-26T21:30:44Z

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J.williams at 22:46, 11 August 2015

2015-08-11T22:46:22Z

New page

[[Category:Done 2015-07-24]]
[[File:Bruce-Nuclear-Szmurlo.jpg|250px|thumb|Figure 1. The Bruce nuclear plant in Ontario uses 8 heavy water CANDU reactors, the most by any nuclear power plant in the world.<ref>Wikimedia Commons [Online], Available: http://en.wikipedia.org/wiki/CANDU_reactor#/media/File:Bruce-Nuclear-Szmurlo.jpg</ref>]]

<onlyinclude>'''CANDU reactor''' is a type of [[nuclear reactor]] which was developed in Canada, and is currently used in [[nuclear power plant]]s for [[electrical generation]] in various countries around the world. CANDU stands for CANada Deuterium Uranium, which reflects the key role of [[deuterium]], or [[heavy water]], to acts as the reactor's [[neutron moderator]], a unique trait of the CANDU.</onlyinclude><ref name=hl>D. Jackson and H. Tammemagi, "CANDU, The Canadian Reactor" in ''Half-Lives: A Guide to Nuclear Technology in Canada'' 1st ed., Canada: Oxford University Press, 2009, ch.6, pp.75-90</ref> The reactors are also different from other reactors because are designed to utilize natural [[uranium]] as a [[fuel]] (as opposed to [[uranium enrichment|enriched uranium]]).<ref name=Ref2>CANDU Owners Group, "CANDU Reactors: What is CANDU?," 2012. [Online]. Available: http://www.candu.org/candu_reactors.html</ref>

The use of these reactors in power plants in Canada provide the country with around 15% of its total [[electricity]] with 19 currently in operation.<ref>IEA (2014), "World energy balances", IEA World Energy Statistics and Balances (database). DOI: http://dx.doi.org/10.1787/data-00512-en (Accessed February 2015)</ref><ref name=wna>World Nuclear Association. (June 6 2015). ''Nuclear Power in Canada'' [Online], Available: http://www.world-nuclear.org/info/Country-Profiles/Countries-A-F/Canada--Nuclear-Power/</ref> 12 CANDU reactors are also in use in China, South Korea, Romania, India, Pakistan and Argentina.<ref name=wna/>

==Characteristics==
===Fuel===
[[File:Fuel_bundle_with_hands.jpg|250px|thumb|Figure 2. CANDU fuel bundle.<ref>From https://canteach.candu.org/Pages/Welcome.aspx (July 9th, 2015)</ref> Each bundle is roughly the size of a fireplace log and provides enough [[electricity]] for a Canadian family of four for 100 years.]]
CANDU reactors use natural uranium as their [[nuclear fuel]]. Natural uranium is composed of about 0.7% uranium-235, and the remaining 99.3% is mostly uranium-238 which cannot directly be used in a [[fission]] process to obtain [[energy]].<ref>World Nuclear Association. (July 6 2015). ''Uranium Enrichment'' [Online], Available: http://www.world-nuclear.org/info/Nuclear-Fuel-Cycle/Conversion-Enrichment-and-Fabrication/Uranium-Enrichment/</ref> The uranium-238 is [[fertile]] and can absorb high speed neutrons and convert to [[plutonium]]-239 which is [[fissile]] and then undergoes fission; this process accounts for around half of the energy produced within the reactor.<ref>From nuclearfaq.ca (July 9th, 2015) http://www.nuclearfaq.ca/cnf_sectionF.htm.</ref> CANDU reactors use about 25 to 30% less mined uranium than a comparable light water reactor (mostly because of the better use of [[neutron]]s in the reactor).

In CANDU reactors, fuel in the form of uranium oxide powder is packed into pellets and placed in the fuel rods. Thirty seven fuel rods are bunched together to complete a cylindrical fuel bundle, seen in Figure 2. The fuel bundle is approximately 50 cm in length and 10 cm in diameter.<ref name=Ref5>J. Gonyeau, "CANDU fuel and reactor specifics," 2005. [Online]. Available: http://www.nucleartourist.com/type/candu2.htm</ref> A fuel bundle remains in the reactor between 6 and 24 months, depending on its location within the core.<ref name=hl/>

===Moderator and Coolant===

The use of natural uranium for fuel is different than most other reactor designs which require the use of [[uranium enrichment|enriched uranium]] (which means that its concentration of fissile uranium-235 has been enhanced). The reason that the uranium does not need to be enriched is due to the '''heavy water moderator''' which doesn't absorb as many neutrons as the commonly used [[light water]] does. In fact, heavy water as a moderator is 1700 times more efficient than light water!<ref name=hl/>

Moderators work to slow down neutrons to speeds at which fissile elements can absorb them. This is required in nuclear reactors using uranium-235, and heavy water is one of the best moderators available. The moderator in the CANDU is kept at a relatively cool [[celsius|70°C]] using a separate cooling system and is circulated through purification systems to ensure a high quality.<Ref name=hl/> Learn more about neutron moderators on their page [[neutron moderator|here]].

The heavy water also acts as coolant in the CANDU; large amounts of [[heat]] are produced by the nuclear reactions, and the heavy water acts to [[heat transfer|transfer]] this heat away to an area where it can be made useful, at the same time as it cools the fuel down to safe [[temperature]]s. This useful area is known as the steam generator, and it acts as a [[heat exchanger]].<ref name=hl/> The hot heavy water flows through tubes inside of the steam generator, which contains ordinary water. The heat from the heavy water [[boiling point|boils]] the ordinary water into [[steam]], which can then be sent to a [[turbine]] to generate electricity.

===Steam Generator===
[[File:Utube.jpg|200px|thumb|Figure 3. The inverted U-tube bundle in a steam generator.<ref>Wikimedia Commons [Online], Available: https://upload.wikimedia.org/wikipedia/commons/8/89/Nuclear_steam_generator.jpg</ref>]]

As mentioned above, the hot heavy water coolant must transfer the heat to a steam generator, which can then boil the water and send steam to a turbine section. The reason that a steam generator is used is due to the fact that the heavy water coolant is [[radioactivity|radioactive]] from being in direct contact with the reactor core. If this radioactive water were to come in contact with the turbine section it would pose a safety harm to workers and potentially the public, and increased costs would be required for shielding and containment in these sections.<ref name=hl/> The coolant flows through inverted tubes submersed within the steam generator, visible in Figure 3. There are hundreds of these tubes to maximize [[heat transfer]] between the systems.

===On-line Refueling===

[[On-line refueling]] in a CANDU reactor is a unique trait that is a major advantage over other reactors such as the [[pressurized water reactor]]s and [[boiling water reactor]]s. The CANDU has the ability to refuel while the reactor is still running whereas other reactors must shut down completely, lowering their [[capacity factor]].<ref name=Ref8>J. Garland, "How and Why is a CANDU designed the way it is?," CANTEACH, 2003. [Online]. Available: https://canteach.candu.org/Content%20Library/20000101.pdf</ref>

This ‘on-power’ refueling can be accomplished because of the horizontal fuel loading design that allows for two remote fueling machines situated at opposite ends of a fuel channel. One fueling machine inserts new fuel bundles while the other receives the spent fuel bundles from the opposite end to be placed in the spent fuel storage bay (which is also done remotely).<ref name=hl/>

==Reactor Configuration==
[[File:CANDUUcore.png|300px|thumb|Figure 4. The face of a CANDU reactor core, with hundreds of pressure tubes that are able to be refueled during operation.<ref>Introduction to CANDU 6- Part 3 Moderator, HTS, Heavy Water, by D.A. Meneley and Y.Q. Ruan. [Online], Available: https://canteach.candu.org/Image%20Library1/Forms/DispForm.aspx?ID=285&RootFolder=/Image%20Library1/19980103-Intro_to_CANDU6_China</ref>]]

The reactor configuration of a CANDU differs from other typical reactors, as fuel bundles are arranged horizontally rather than vertically, and are placed inside pressure tubes within a vessel (called the [[calandria]]).<ref name=hl/> The core of a CANDU reactor needs to be larger than comparable light water reactors however if it wants to achieve the same output capacity, and this due to the CANDU's use of natural uranium. This reactor configuration can be seen in Figure 4.

There are several hundred pressure tubes within a CANDU, with exact amounts differing between reactors. The coolant flows through these pressure tubes, each of which are enclosed within a calandria tube. The pressure tubes and calandria tubes are separated by spacers, in order to keep the coolant and the moderator separate. The space between these two tubes is filled with [[carbon dioxide]], which acts as a thermal insulator in order to limit heat loss to the moderator.<ref name=hl/>

The [[reactor building]] that the CANDU is placed in is made of thick concrete and steel walls, with the walls of newer buildings also filled with hundreds of [[tonne]]s of water and thick steel balls to provide additional shielding.<ref name=hl/>

==Safety Features==

===Passive Safety Features===

The passive features in a CANDU include:

*'''Bending of the fuel channels in the event of overheating''' due to the CANDU's horizontal configuration, which will in turn slow down the rate of reaction. This is caused by the fact that the fuel rods are aligned in the ideal position for reactivity, and any bend in a fuel channel causes the reaction to slow because of wasted neutrons that do not hit their intended targets.<ref name=Ref6>CANDU 6 Program Team: Reactor Development Business Unit, CANDU 6 Technical Summary, 2005. Available: https://canteach.candu.org/Content%20Library/CANDU6_TechnicalSummary-s.pdf</ref>

*'''[[Control rod]]s held up by electromagnets''', which in the absence of a power signal are immediately released into the reactor core, making it impossible for the reaction to continue.<ref name=Ref6/> This is the primary shutdown system of a CANDU reactor.

===Active Safety Features===

*'''The injecting of neutron "poison"''' can be done to greatly diminish the nuclear reaction in the case of emergency.<ref name=hl/> This is done by pumps which are driven by a high pressure helium tank; When the reactor is required to shut down, valves between the high pressure helium tank and the gadolinium tanks are opened releasing the helium which drives the gadolinium into the reactor core.<ref name=Ref6/> Helium is appropriate for this job because it is doesn’t have the tendency to react.

*'''Equipped with an ample supply of light water''' so that in the event of a LOCA, cool light water can be quickly mixed with the overheating heavy water coolant to promptly bring the system back down to proper operating temperatures.<ref name=Ref6/> This is only used as a last resort as mixing the light and heavy water would mean having to re-purify the heavy water coolant.

For more information on CANDU reactors please see [nuclearfaq.ca Jeremy Whitlock's website] or download a pdf of the e-book [http://teachnuclear.ca/wp-content/uploads/2013/05/Half-Lives14.pdf Half-lives].
==References==
{{reflist}}
[[Category:Uploaded]]