Control rod - Revision history

Jmdonev: 1 revision imported

2021-10-18T16:14:41Z

1 revision imported

← Older revision	Revision as of 16:14, 18 October 2021
(No difference)

energy>Luisa at 15:33, 16 October 2021

2021-10-16T15:33:04Z

← Older revision		Revision as of 15:33, 16 October 2021
Line 2:		Line 2:
	[[Category:Translated to French]]		[[Category:Translated to French]]
	[[fr:Barre de contrôle]]		[[fr:Barre de contrôle]]
			[[Category:Translated to Spanish]]
			[[es:Barra de control]]
	[[File:controlrods.jpg\|360px\|thumb\|right\|Figure 1. A [[pressurized water reactor]] with control rods seen sticking out of the head of the reactor.<ref>Wikimedia Commons. (July 7, 2015). ''Reactor Vessel Head'' [Online]. Available: https://upload.wikimedia.org/wikipedia/commons/f/f8/Reactor_Vessel_head.jpg</ref>]]		[[File:controlrods.jpg\|360px\|thumb\|right\|Figure 1. A [[pressurized water reactor]] with control rods seen sticking out of the head of the reactor.<ref>Wikimedia Commons. (July 7, 2015). ''Reactor Vessel Head'' [Online]. Available: https://upload.wikimedia.org/wikipedia/commons/f/f8/Reactor_Vessel_head.jpg</ref>]]

Jmdonev: 1 revision imported

2021-09-27T00:03:01Z

1 revision imported

← Older revision	Revision as of 00:03, 27 September 2021
(No difference)

energy>Ethan.boechler at 19:07, 18 June 2021

2021-06-18T19:07:13Z

← Older revision		Revision as of 19:07, 18 June 2021
Line 1:		Line 1:
	[[Category:Done 2018-05-18]]		[[Category:Done 2018-05-18]]
			[[Category:Translated to French]]
			[[fr:Barre de contrôle]]
	[[File:controlrods.jpg\|360px\|thumb\|right\|Figure 1. A [[pressurized water reactor]] with control rods seen sticking out of the head of the reactor.<ref>Wikimedia Commons. (July 7, 2015). ''Reactor Vessel Head'' [Online]. Available: https://upload.wikimedia.org/wikipedia/commons/f/f8/Reactor_Vessel_head.jpg</ref>]]		[[File:controlrods.jpg\|360px\|thumb\|right\|Figure 1. A [[pressurized water reactor]] with control rods seen sticking out of the head of the reactor.<ref>Wikimedia Commons. (July 7, 2015). ''Reactor Vessel Head'' [Online]. Available: https://upload.wikimedia.org/wikipedia/commons/f/f8/Reactor_Vessel_head.jpg</ref>]]

Jmdonev: 1 revision imported

2018-05-18T22:53:07Z

1 revision imported

← Older revision	Revision as of 22:53, 18 May 2018
(No difference)

Jmdonev at 18:36, 11 May 2018

2018-05-11T18:36:47Z

← Older revision		Revision as of 18:36, 11 May 2018
Line 1:		Line 1:
	[[Category:Done ~~2015~~-07-24]]		[[Category:Done 2018-05-18]]
	[[File:controlrods.jpg\|360px\|thumb\|right\|Figure 1. A [[pressurized water reactor]] with control rods seen sticking out of the head of the reactor.<ref>Wikimedia Commons. (July 7, 2015). ''Reactor Vessel Head'' [Online]. Available: https://upload.wikimedia.org/wikipedia/commons/f/f8/Reactor_Vessel_head.jpg</ref>]]		[[File:controlrods.jpg\|360px\|thumb\|right\|Figure 1. A [[pressurized water reactor]] with control rods seen sticking out of the head of the reactor.<ref>Wikimedia Commons. (July 7, 2015). ''Reactor Vessel Head'' [Online]. Available: https://upload.wikimedia.org/wikipedia/commons/f/f8/Reactor_Vessel_head.jpg</ref>]]

Line 9:		Line 9:

	==Design==		==Design==
	Control rods are rods, plates, or tubes containing a material that ~~slows~~ neutrons.<ref>NRC Glossary. (July 7, 2015). ''Control Rods'' [Online]. Available: http://www.nrc.gov/reading-rm/basic-ref/glossary/control-rod.html</ref> Several of these control rods, about the size of [[nuclear fuel\|fuel rods]], are spaced evenly and connected on one end by a metal bracket known as a spider. Typical reactors can contain around 50 of these clusters with 20 individual control rods in each cluster.<ref name="RE2"/>		Control rods are rods, plates, or tubes containing a material (like boron or hafnium) that absorbs neutrons.<ref>NRC Glossary. (July 7, 2015). ''Control Rods'' [Online]. Available: http://www.nrc.gov/reading-rm/basic-ref/glossary/control-rod.html</ref> Several of these control rods, about the size of [[nuclear fuel\|fuel rods]], are spaced evenly and connected on one end by a metal bracket known as a spider. Typical reactors can contain around 50 of these clusters with 20 individual control rods in each cluster.<ref name="RE2"/>

	The ability of a control rod to absorb neutrons to control the fission chain reaction requires a choice of material that has high neutron-absorbing abilities. The measure of how well a material absorbs neutrons is known as its [[neutron absorption]] cross section, or <m> \sigma_a </m>, measured in [[barn]]s (equal to 10<sup>-28</sup> square meters).<ref name="RE2">James Grayson. (July 3, 2015). ''Control Rods in Nuclear Reactors'' [Online]. Available: http://large.stanford.edu/courses/2011/ph241/grayson1/</ref> Generally speaking, control rods are made using cadmium, hafnium, or enriched boron.<ref name="RE1"/>		The ability of a control rod to absorb neutrons to control the fission chain reaction requires a choice of material that has high neutron-absorbing abilities. The measure of how well a material absorbs neutrons is known as its [[neutron absorption]] cross section, or <math> \sigma_a </math>, measured in [[barn]]s (equal to 10<sup>-28</sup> square meters).<ref name="RE2">James Grayson. (July 3, 2015). ''Control Rods in Nuclear Reactors'' [Online]. Available: http://large.stanford.edu/courses/2011/ph241/grayson1/</ref> Generally speaking, control rods are made using cadmium, hafnium, or enriched boron.<ref name="RE1"/>

	Along with the choice in material, the mechanical properties and cost are important when designing a control rod. For example, boron-10 is one of the best neutron absorbers, however it is not ideal for building control rods as it is extremely brittle. Additionally, natural boron must be enriched to have reasonable absorption levels, which becomes very expensive.<ref name="RE2"/>		Along with the choice in material, the mechanical properties and cost are important when designing a control rod. For example, boron-10 is one of the best neutron absorbers, however it is not ideal for building control rods as it is extremely brittle. Additionally, natural boron must be enriched to have reasonable absorption levels, which becomes very expensive.<ref name="RE2"/>

J.williams: 1 revision imported

2015-08-26T21:30:57Z

1 revision imported

← Older revision	Revision as of 21:30, 26 August 2015
(No difference)

J.williams at 16:52, 12 August 2015

2015-08-12T16:52:59Z

New page

[[Category:Done 2015-07-24]]
[[File:controlrods.jpg|360px|thumb|right|Figure 1. A [[pressurized water reactor]] with control rods seen sticking out of the head of the reactor.<ref>Wikimedia Commons. (July 7, 2015). ''Reactor Vessel Head'' [Online]. Available: https://upload.wikimedia.org/wikipedia/commons/f/f8/Reactor_Vessel_head.jpg</ref>]]

<onlyinclude>A '''control rod''' is a device that is used to absorb [[neutron]]s so that the [[nuclear chain reaction]] taking place within the [[nuclear reactor|reactor]] core can be slowed down or stopped completely by inserting the rods further, or accelerated by removing them slightly.</onlyinclude><ref name="RE1">Ian Hore-Lacy. (July 7, 2015). ''Nuclear Energy in the 21st Century'', 2nd Ed. Burlington, MA, U.S.A: Elsevier Inc, 2006</ref> Essentially, control rods provide real-time control of the [[fission]] process, ensuring that it remains active while preventing it from accelerating out of control.

[[Uranium]]-235 fission releases 2.5 neutrons on average, but only one neutron is needed to sustain the nuclear chain reaction at a steady rate. The control rods absorb these extra neutrons and can be used to adjust the [[power]] output of the reactor. When inserted the standard amount, their position is at '''criticality''' and the power output remains the same.<ref name="RE1"/> If the rod is pushed in the number of neutrons decreases along with the power output and the reactor is below criticality. The opposite is true if the rods are pulled out slightly as fission goes beyond criticality. This is shown in Figure 2.

[[File:controlrodschematic.png|780px|framed|center|Figure 2. A schematic showing how reactor power output changes with how much the control rods (shown in green) are inserted. On the left, the control rods are inserted more than usual, reducing the power output of the reactor. On the right, the control rods are inserted less than usual, increasing the power output.<ref>Wikimedia Commons. (July 7, 2015). ''Control Rods S chematic'' [Online]. Available:https://commons.wikimedia.org/wiki/File:Control_rods_schematic.svg#/media/File:Control_rods_schematic.svg</ref>]]

==Design==
Control rods are rods, plates, or tubes containing a material that slows neutrons.<ref>NRC Glossary. (July 7, 2015). ''Control Rods'' [Online]. Available: http://www.nrc.gov/reading-rm/basic-ref/glossary/control-rod.html</ref> Several of these control rods, about the size of [[nuclear fuel|fuel rods]], are spaced evenly and connected on one end by a metal bracket known as a spider. Typical reactors can contain around 50 of these clusters with 20 individual control rods in each cluster.<ref name="RE2"/>

The ability of a control rod to absorb neutrons to control the fission chain reaction requires a choice of material that has high neutron-absorbing abilities. The measure of how well a material absorbs neutrons is known as its [[neutron absorption]] cross section, or <m> \sigma_a </m>, measured in [[barn]]s (equal to 10<sup>-28</sup> square meters).<ref name="RE2">James Grayson. (July 3, 2015). ''Control Rods in Nuclear Reactors'' [Online]. Available: http://large.stanford.edu/courses/2011/ph241/grayson1/</ref> Generally speaking, control rods are made using cadmium, hafnium, or enriched boron.<ref name="RE1"/>

Along with the choice in material, the mechanical properties and cost are important when designing a control rod. For example, boron-10 is one of the best neutron absorbers, however it is not ideal for building control rods as it is extremely brittle. Additionally, natural boron must be enriched to have reasonable absorption levels, which becomes very expensive.<ref name="RE2"/>

==Safety Precautions==
Control rods are important safety features of reactors as they allow the user to control the output of the reactor. In some types of reactors, most notably [[CANDU reactor]]s, the control rods are held up by electromagnets. This means that if there is some sort of power failure or loss of signal the control rods are immediately released and fall into the reactor core because of gravity.<ref>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> This prevents the fission reaction from continuing and acts as the primary shutdown system in case of emergency. This dropping motion can also be induced manually if the machinery holding the rods up fails in some way. When the control rods are dropped into the reactor, it is a process known as [[scramming]].<ref>Nuclear Power. (July 7, 2015). ''Control Rods'' [Online]. Available: http://www.nuclear-power.net/nuclear-power-plant/control-rods/</ref> In [[boiling water reactor]]s, the design is different as the control rods must be pushed up into the reactor since they are located on the bottom of the reactor in that design.

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