https://citizendium.org/wiki/index.php?title=Nuclear_reactor&feed=atom&action=historyNuclear reactor - Revision history2024-03-29T12:22:44ZRevision history for this page on the wikiMediaWiki 1.39.5https://citizendium.org/wiki/index.php?title=Nuclear_reactor&diff=877924&oldid=prevPat Palmer at 19:19, 24 January 20232023-01-24T19:19:30Z<p></p>
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<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>{{TOC|right}}</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>{{TOC|right}}</div></td></tr>
<tr><td class="diff-marker" data-marker="−"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div>A '''nuclear reactor''' is vessel in which controlled [[nuclear reaction]]s take place within one building or container. Nuclear reactions are controlled [[nuclear fission]] [[Chain reaction/Definition|chain reaction]]s with a [[neutron]] flux. Reasons for reactors existing include heat generation for electrical generation, [[marine propulsion]], or heating industrial plants or other facilities; breeding nuclear fuel; the preparation of [[radioactivity|radioactive]] [[isotope]]s for use in [[nuclear medicine]], industrial testing, or creating controlled sources of radiation; production of nuclear materials such as [[plutonium]] or [[tritium]]; or making materials temporarily [[radioactivity|radioactive]] for procedures such as [[neutron activation analysis]]. While there can be some overlap of functions, larger reactors tend to be optimized for a single purpose; part of the design failures causing the [[Chernobyl Disaster]] were that the reactor tried to be equally effective for electric power and plutonium generation.</div></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>A '''nuclear reactor''' is vessel in which controlled [[nuclear reaction]]s take place within one building or container <ins style="font-weight: bold; text-decoration: none;">with the ultimate goal of generating electricity (steam may first be produced, and then the steam is used to generate electrical power)</ins>. Nuclear reactions are controlled [[nuclear fission]] [[Chain reaction/Definition|chain reaction]]s with a [[neutron]] flux. Reasons for reactors existing include heat generation for electrical generation, [[marine propulsion]], or heating industrial plants or other facilities; breeding nuclear fuel; the preparation of [[radioactivity|radioactive]] [[isotope]]s for use in [[nuclear medicine]], industrial testing, or creating controlled sources of radiation; production of nuclear materials such as [[plutonium]] or [[tritium]]; or making materials temporarily [[radioactivity|radioactive]] for procedures such as [[neutron activation analysis]]. While there can be some overlap of functions, larger reactors tend to be optimized for a single purpose; part of the design failures causing the [[Chernobyl Disaster]] were that the reactor tried to be equally effective for electric power and plutonium generation.</div></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>==Fundamentals of nuclear fission reactors==</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>==Fundamentals of nuclear fission reactors==</div></td></tr>
</table>Pat Palmerhttps://citizendium.org/wiki/index.php?title=Nuclear_reactor&diff=876253&oldid=prevPat Palmer: removing "generally"2023-01-03T19:52:12Z<p>removing "generally"</p>
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<td colspan="2" style="background-color: #fff; color: #202122; text-align: center;">Revision as of 14:52, 3 January 2023</td>
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<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>{{TOC|right}}</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>{{TOC|right}}</div></td></tr>
<tr><td class="diff-marker" data-marker="−"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div>A '''nuclear reactor''' is vessel in which controlled [[nuclear reaction]]s take place within one building or container. Nuclear reactions <del style="font-weight: bold; text-decoration: none;">generally </del>are controlled [[nuclear fission]] [[Chain reaction/Definition|chain reaction]]s with a [[neutron]] flux. Reasons for reactors existing include heat generation for electrical generation, [[marine propulsion]], or heating industrial plants or other facilities; breeding nuclear fuel; the preparation of [[radioactivity|radioactive]] [[isotope]]s for use in [[nuclear medicine]], industrial testing, or creating controlled sources of radiation; production of nuclear materials such as [[plutonium]] or [[tritium]]; or making materials temporarily [[radioactivity|radioactive]] for procedures such as [[neutron activation analysis]]. While there can be some overlap of functions, larger reactors tend to be optimized for a single purpose; part of the design failures causing the [[Chernobyl Disaster]] were that the reactor tried to be equally effective for electric power and plutonium generation.</div></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>A '''nuclear reactor''' is vessel in which controlled [[nuclear reaction]]s take place within one building or container. Nuclear reactions are controlled [[nuclear fission]] [[Chain reaction/Definition|chain reaction]]s with a [[neutron]] flux. Reasons for reactors existing include heat generation for electrical generation, [[marine propulsion]], or heating industrial plants or other facilities; breeding nuclear fuel; the preparation of [[radioactivity|radioactive]] [[isotope]]s for use in [[nuclear medicine]], industrial testing, or creating controlled sources of radiation; production of nuclear materials such as [[plutonium]] or [[tritium]]; or making materials temporarily [[radioactivity|radioactive]] for procedures such as [[neutron activation analysis]]. While there can be some overlap of functions, larger reactors tend to be optimized for a single purpose; part of the design failures causing the [[Chernobyl Disaster]] were that the reactor tried to be equally effective for electric power and plutonium generation.</div></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>==Fundamentals of nuclear fission reactors==</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>==Fundamentals of nuclear fission reactors==</div></td></tr>
</table>Pat Palmerhttps://citizendium.org/wiki/index.php?title=Nuclear_reactor&diff=876252&oldid=prevPat Palmer at 19:51, 3 January 20232023-01-03T19:51:21Z<p></p>
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<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>{{TOC|right}}</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>{{TOC|right}}</div></td></tr>
<tr><td class="diff-marker" data-marker="−"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div>A '''nuclear reactor''' is vessel in which controlled [[nuclear reaction]]s take place<del style="font-weight: bold; text-decoration: none;">. A reactor may include associated equipment and material in the same </del>building or container. Nuclear reactions generally are controlled [[nuclear fission]] [[Chain reaction/Definition|chain reaction]]s with a [[neutron]] flux. Reasons for reactors existing include heat generation for electrical generation, [[marine propulsion]], or heating industrial plants or other facilities; breeding nuclear fuel; the preparation of [[radioactivity|radioactive]] [[isotope]]s for use in [[nuclear medicine]], industrial testing, or creating controlled sources of radiation; production of nuclear materials such as [[plutonium]] or [[tritium]]; or making materials temporarily [[radioactivity|radioactive]] for procedures such as [[neutron activation analysis]]. While there can be some overlap of functions, larger reactors tend to be optimized for a single purpose; part of the design failures causing the [[Chernobyl Disaster]] were that the reactor tried to be equally effective for electric power and plutonium generation.</div></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>A '''nuclear reactor''' is vessel in which controlled [[nuclear reaction]]s take place <ins style="font-weight: bold; text-decoration: none;">within one </ins>building or container. Nuclear reactions generally are controlled [[nuclear fission]] [[Chain reaction/Definition|chain reaction]]s with a [[neutron]] flux. Reasons for reactors existing include heat generation for electrical generation, [[marine propulsion]], or heating industrial plants or other facilities; breeding nuclear fuel; the preparation of [[radioactivity|radioactive]] [[isotope]]s for use in [[nuclear medicine]], industrial testing, or creating controlled sources of radiation; production of nuclear materials such as [[plutonium]] or [[tritium]]; or making materials temporarily [[radioactivity|radioactive]] for procedures such as [[neutron activation analysis]]. While there can be some overlap of functions, larger reactors tend to be optimized for a single purpose; part of the design failures causing the [[Chernobyl Disaster]] were that the reactor tried to be equally effective for electric power and plutonium generation.</div></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>==Fundamentals of nuclear fission reactors==</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>==Fundamentals of nuclear fission reactors==</div></td></tr>
</table>Pat Palmerhttps://citizendium.org/wiki/index.php?title=Nuclear_reactor&diff=875184&oldid=prevPat Palmer: /* Fundamentals of nuclear fission reactors */ unlinking "nuclear chain reaction", as it is covered by previous links "nuclear fission" and "chain reaction"2022-12-08T14:58:27Z<p><span dir="auto"><span class="autocomment">Fundamentals of nuclear fission reactors: </span> unlinking "nuclear chain reaction", as it is covered by previous links "nuclear fission" and "chain reaction"</span></p>
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<td colspan="2" style="background-color: #fff; color: #202122; text-align: center;">Revision as of 09:58, 8 December 2022</td>
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<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>==Fundamentals of nuclear fission reactors==</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>==Fundamentals of nuclear fission reactors==</div></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td></tr>
<tr><td class="diff-marker" data-marker="−"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div>For power generation, nuclear reactors are the centerpiece of [[nuclear power plant]]s. Up to this time, nuclear reactors for large scale power generation use energy released by [[nuclear fission]], which is highly [[exothermic]], meaning each fission releases a relative large amount of heat per atom split. These nuclear fission reactions take place by a controlled <del style="font-weight: bold; text-decoration: none;">[[</del>nuclear chain reaction<del style="font-weight: bold; text-decoration: none;">]] </del>in the '''reactor core''' inside the reactor. The material undergoing the fission in the core is considered the '''nuclear fuel'''. The nuclear fuel consists of [[fissile isotope]]s, atoms of [[isotope]]s of high [[atomic number]] and [[Atomic mass|mass]] which can readily undergo fission to produce a nuclear chain reaction. The three most common fissile isotopes are [[uranium]]-235 (<sup>235</sup>U or U-235), plutonium-239 (<sup>239</sup>Pu or Pu-239), and uranium-233 (<sup>233</sup>U or U-233). Material that can be bred into such fissile isotopes may also be considered nuclear fuel. For example, uranium-238 (<sup>238</sup>U or U-238) can be bred to produce plutonium-239 and [[thorium]]-232 (<sup>232</sup>Th or Th-232) can be bred to produce uranium-233. Nuclear reactors in which this sort of breeding takes place are called '''nuclear breeder reactors'''.</div></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>For power generation, nuclear reactors are the centerpiece of [[nuclear power plant]]s. Up to this time, nuclear reactors for large scale power generation use energy released by [[nuclear fission]], which is highly [[exothermic]], meaning each fission releases a relative large amount of heat per atom split. These nuclear fission reactions take place by a controlled nuclear chain reaction in the '''reactor core''' inside the reactor. The material undergoing the fission in the core is considered the '''nuclear fuel'''. The nuclear fuel consists of [[fissile isotope]]s, atoms of [[isotope]]s of high [[atomic number]] and [[Atomic mass|mass]] which can readily undergo fission to produce a nuclear chain reaction. The three most common fissile isotopes are [[uranium]]-235 (<sup>235</sup>U or U-235), plutonium-239 (<sup>239</sup>Pu or Pu-239), and uranium-233 (<sup>233</sup>U or U-233). Material that can be bred into such fissile isotopes may also be considered nuclear fuel. For example, uranium-238 (<sup>238</sup>U or U-238) can be bred to produce plutonium-239 and [[thorium]]-232 (<sup>232</sup>Th or Th-232) can be bred to produce uranium-233. Nuclear reactors in which this sort of breeding takes place are called '''nuclear breeder reactors'''.</div></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>Nuclear fission typically occurs when a neutron hits a fissile nucleus, splitting the nucleus into two smaller nuclei called [[nuclear fission products]] and a couple of neutrons. These newly released neutrons can then go on to cause further fission of other fissile nuclei, releasing more neutrons. A repetitive cycle of fissions and neutrons results in a chain reaction under the right conditions, which is the objective of a nuclear fission reactor. In such an operating reactor, there are many neutrons flying around in the core, and the concentration of these neutrons is often referred to as a ''neutron flux''. The numerous nuclear fissions in an operating reactor core release heat, which is used as thermal [[Power (physics)|power]], the usual ultimate goal of the reactor. A reactor has a number of '''control rods''' consisting of a material which [[Neutron capture|captures neutrons]]. These control rods can be withdrawn from or inserted into the core to control the nuclear chain reaction. Inserting all of the control rods into the core will capture the neutrons and stop the chain reaction, effectively shutting down the reactor. A quick insertion of the control rods into the core for an emergency shutdown of the reactor is called a '''scram'''. Withdrawing the control rods in a precise manner is used to start up the reactor. There are also other means used for controlling the power level of a nuclear reactor.</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>Nuclear fission typically occurs when a neutron hits a fissile nucleus, splitting the nucleus into two smaller nuclei called [[nuclear fission products]] and a couple of neutrons. These newly released neutrons can then go on to cause further fission of other fissile nuclei, releasing more neutrons. A repetitive cycle of fissions and neutrons results in a chain reaction under the right conditions, which is the objective of a nuclear fission reactor. In such an operating reactor, there are many neutrons flying around in the core, and the concentration of these neutrons is often referred to as a ''neutron flux''. The numerous nuclear fissions in an operating reactor core release heat, which is used as thermal [[Power (physics)|power]], the usual ultimate goal of the reactor. A reactor has a number of '''control rods''' consisting of a material which [[Neutron capture|captures neutrons]]. These control rods can be withdrawn from or inserted into the core to control the nuclear chain reaction. Inserting all of the control rods into the core will capture the neutrons and stop the chain reaction, effectively shutting down the reactor. A quick insertion of the control rods into the core for an emergency shutdown of the reactor is called a '''scram'''. Withdrawing the control rods in a precise manner is used to start up the reactor. There are also other means used for controlling the power level of a nuclear reactor.</div></td></tr>
</table>Pat Palmerhttps://citizendium.org/wiki/index.php?title=Nuclear_reactor&diff=875183&oldid=prevPat Palmer: fixing links2022-12-08T14:57:02Z<p>fixing links</p>
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<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>{{TOC|right}}</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>{{TOC|right}}</div></td></tr>
<tr><td class="diff-marker" data-marker="−"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div>A '''nuclear reactor''' is vessel in which controlled [[nuclear reaction]]s take place. A reactor may include associated equipment and material in the same building or container. Nuclear reactions generally are controlled [[nuclear fission chain reaction]]s with a [[neutron]] flux. Reasons for reactors existing include heat generation for electrical generation, [[marine propulsion]], or heating industrial plants or other facilities; breeding nuclear fuel; the preparation of [[radioactivity|radioactive]] [[isotope]]s for use in [[nuclear medicine]], industrial testing, or creating controlled sources of radiation; production of nuclear materials such as [[plutonium]] or [[tritium]]; or making materials temporarily [[radioactivity|radioactive]] for procedures such as [[neutron activation analysis]]. While there can be some overlap of functions, larger reactors tend to be optimized for a single purpose; part of the design failures causing the [[Chernobyl Disaster]] were that the reactor tried to be equally effective for electric power and plutonium generation. <del style="font-weight: bold; text-decoration: none;"> </del></div></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>A '''nuclear reactor''' is vessel in which controlled [[nuclear reaction]]s take place. A reactor may include associated equipment and material in the same building or container. Nuclear reactions generally are controlled [[nuclear fission<ins style="font-weight: bold; text-decoration: none;">]] [[Chain reaction/Definition|</ins>chain reaction]]s with a [[neutron]] flux. Reasons for reactors existing include heat generation for electrical generation, [[marine propulsion]], or heating industrial plants or other facilities; breeding nuclear fuel; the preparation of [[radioactivity|radioactive]] [[isotope]]s for use in [[nuclear medicine]], industrial testing, or creating controlled sources of radiation; production of nuclear materials such as [[plutonium]] or [[tritium]]; or making materials temporarily [[radioactivity|radioactive]] for procedures such as [[neutron activation analysis]]. While there can be some overlap of functions, larger reactors tend to be optimized for a single purpose; part of the design failures causing the [[Chernobyl Disaster]] were that the reactor tried to be equally effective for electric power and plutonium generation.</div></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>==Fundamentals of nuclear fission reactors==</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>==Fundamentals of nuclear fission reactors==</div></td></tr>
</table>Pat Palmerhttps://citizendium.org/wiki/index.php?title=Nuclear_reactor&diff=875182&oldid=prevPat Palmer at 14:55, 8 December 20222022-12-08T14:55:44Z<p></p>
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<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>{{TOC|right}}</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>{{TOC|right}}</div></td></tr>
<tr><td class="diff-marker" data-marker="−"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div>A '''nuclear reactor''' is <del style="font-weight: bold; text-decoration: none;">a unit or </del>vessel in which controlled [[nuclear reaction]]s take place. A reactor <del style="font-weight: bold; text-decoration: none;">includes </del>associated equipment and material. Nuclear reactions generally are controlled [[nuclear fission chain reaction]]s with a [[neutron]] flux. Reasons for reactors existing include heat generation for electrical generation, [[marine propulsion]], or heating industrial plants or other facilities; breeding nuclear fuel; the preparation of [[radioactivity|radioactive]] [[isotope]]s for use in [[nuclear medicine]], industrial testing, or creating controlled sources of radiation; production of nuclear materials such as [[plutonium]] or [[tritium]]; or making materials temporarily [[radioactivity|radioactive]] for procedures such as [[neutron activation analysis]]. While there can be some overlap of functions, larger reactors tend to be optimized for a single purpose; part of the design failures causing the [[Chernobyl Disaster]] were that the reactor tried to be equally effective for electric power and plutonium generation. </div></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>A '''nuclear reactor''' is vessel in which controlled [[nuclear reaction]]s take place. A reactor <ins style="font-weight: bold; text-decoration: none;">may include </ins>associated equipment and material <ins style="font-weight: bold; text-decoration: none;">in the same building or container</ins>. Nuclear reactions generally are controlled [[nuclear fission chain reaction]]s with a [[neutron]] flux. Reasons for reactors existing include heat generation for electrical generation, [[marine propulsion]], or heating industrial plants or other facilities; breeding nuclear fuel; the preparation of [[radioactivity|radioactive]] [[isotope]]s for use in [[nuclear medicine]], industrial testing, or creating controlled sources of radiation; production of nuclear materials such as [[plutonium]] or [[tritium]]; or making materials temporarily [[radioactivity|radioactive]] for procedures such as [[neutron activation analysis]]. While there can be some overlap of functions, larger reactors tend to be optimized for a single purpose; part of the design failures causing the [[Chernobyl Disaster]] were that the reactor tried to be equally effective for electric power and plutonium generation. </div></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>==Fundamentals of nuclear fission reactors==</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>==Fundamentals of nuclear fission reactors==</div></td></tr>
</table>Pat Palmerhttps://citizendium.org/wiki/index.php?title=Nuclear_reactor&diff=875181&oldid=prevPat Palmer: Rework of the opener to be less fidgety2022-12-08T14:54:45Z<p>Rework of the opener to be less fidgety</p>
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<td colspan="2" style="background-color: #fff; color: #202122; text-align: center;">Revision as of 09:54, 8 December 2022</td>
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<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>{{subpages}}</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>{{subpages}}</div></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>{{TOC|right}}</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>{{TOC|right}}</div></td></tr>
<tr><td class="diff-marker" data-marker="−"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div>A '''nuclear reactor''' is a unit or vessel<del style="font-weight: bold; text-decoration: none;">, including associated equipment and material, </del>in which controlled [[nuclear reaction]]s take place <del style="font-weight: bold; text-decoration: none;">for a variety of purposes</del>. <del style="font-weight: bold; text-decoration: none;">These </del>reactions generally <del style="font-weight: bold; text-decoration: none;">involve </del>controlled [[nuclear fission chain reaction]]s with a [[neutron]] flux. <del style="font-weight: bold; text-decoration: none;">These purposes may </del>include heat generation for electrical generation, [[marine propulsion]], or heating industrial plants or other facilities; breeding nuclear fuel; the preparation of [[radioactivity|radioactive]] [[isotope]]s for use in [[nuclear medicine]], industrial testing, or creating controlled sources of radiation; production of nuclear materials such as [[plutonium]] or [[tritium]]; or making materials temporarily [[radioactivity|radioactive]] for procedures such as [[neutron activation analysis]]. While there can be some overlap of functions, larger reactors tend to be optimized for a single purpose; part of the design failures causing the [[Chernobyl Disaster]] were that the reactor tried to be equally effective for electric power and plutonium generation. </div></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>A '''nuclear reactor''' is a unit or vessel in which controlled [[nuclear reaction]]s take place. <ins style="font-weight: bold; text-decoration: none;">A reactor includes associated equipment and material. Nuclear </ins>reactions generally <ins style="font-weight: bold; text-decoration: none;">are </ins>controlled [[nuclear fission chain reaction]]s with a [[neutron]] flux. <ins style="font-weight: bold; text-decoration: none;">Reasons for reactors existing </ins>include heat generation for electrical generation, [[marine propulsion]], or heating industrial plants or other facilities; breeding nuclear fuel; the preparation of [[radioactivity|radioactive]] [[isotope]]s for use in [[nuclear medicine]], industrial testing, or creating controlled sources of radiation; production of nuclear materials such as [[plutonium]] or [[tritium]]; or making materials temporarily [[radioactivity|radioactive]] for procedures such as [[neutron activation analysis]]. While there can be some overlap of functions, larger reactors tend to be optimized for a single purpose; part of the design failures causing the [[Chernobyl Disaster]] were that the reactor tried to be equally effective for electric power and plutonium generation. </div></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>==Fundamentals of nuclear fission reactors==</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>==Fundamentals of nuclear fission reactors==</div></td></tr>
</table>Pat Palmerhttps://citizendium.org/wiki/index.php?title=Nuclear_reactor&diff=740283&oldid=previmported>Henry A. Padleckas: wrote "Neutron moderators" section2012-11-11T09:30:11Z<p>wrote "Neutron moderators" section</p>
<table style="background-color: #fff; color: #202122;" data-mw="interface">
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<td colspan="2" style="background-color: #fff; color: #202122; text-align: center;">Revision as of 04:30, 11 November 2012</td>
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<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>{{TOC|right}}</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>{{TOC|right}}</div></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>A '''nuclear reactor''' is a unit or vessel, including associated equipment and material, in which controlled [[nuclear reaction]]s take place for a variety of purposes. These reactions generally involve controlled [[nuclear fission chain reaction]]s with a [[neutron]] flux. These purposes may include heat generation for electrical generation, [[marine propulsion]], or heating industrial plants or other facilities; breeding nuclear fuel; the preparation of [[radioactivity|radioactive]] [[isotope]]s for use in [[nuclear medicine]], industrial testing, or creating controlled sources of radiation; production of nuclear materials such as [[plutonium]] or [[tritium]]; or making materials temporarily [[radioactivity|radioactive]] for procedures such as [[neutron activation analysis]]. While there can be some overlap of functions, larger reactors tend to be optimized for a single purpose; part of the design failures causing the [[Chernobyl Disaster]] were that the reactor tried to be equally effective for electric power and plutonium generation. </div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>A '''nuclear reactor''' is a unit or vessel, including associated equipment and material, in which controlled [[nuclear reaction]]s take place for a variety of purposes. These reactions generally involve controlled [[nuclear fission chain reaction]]s with a [[neutron]] flux. These purposes may include heat generation for electrical generation, [[marine propulsion]], or heating industrial plants or other facilities; breeding nuclear fuel; the preparation of [[radioactivity|radioactive]] [[isotope]]s for use in [[nuclear medicine]], industrial testing, or creating controlled sources of radiation; production of nuclear materials such as [[plutonium]] or [[tritium]]; or making materials temporarily [[radioactivity|radioactive]] for procedures such as [[neutron activation analysis]]. While there can be some overlap of functions, larger reactors tend to be optimized for a single purpose; part of the design failures causing the [[Chernobyl Disaster]] were that the reactor tried to be equally effective for electric power and plutonium generation. </div></td></tr>
<tr><td colspan="2" class="diff-side-deleted"></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div><ins style="font-weight: bold; text-decoration: none;"></ins></div></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>==Fundamentals of nuclear fission reactors==</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>==Fundamentals of nuclear fission reactors==</div></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td></tr>
<tr><td class="diff-marker" data-marker="−"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div>For power generation, nuclear reactors are the centerpiece of [[nuclear power plant]]s. Up to this time, nuclear reactors for large scale power generation use energy released by [[nuclear fission]], which is highly exothermic, meaning each fission releases a relative large amount of heat per atom split. These nuclear fission reactions take place by a controlled [[nuclear chain reaction]] in the '''reactor core''' inside the reactor. The material undergoing the fission in the core is considered the '''nuclear fuel'''. The nuclear fuel consists of [[fissile isotope]]s, atoms of [[isotope]]s of high [[atomic number]] and [[Atomic mass|mass]] which can readily undergo fission to produce a nuclear chain reaction. The three most common fissile isotopes are [[uranium]]-235 (<sup>235</sup>U or U-235), plutonium-239 (<sup>239</sup>Pu or Pu-239), and uranium-233 (<sup>233</sup>U or U-233). Material that can be bred into such fissile isotopes may also be considered nuclear fuel. For example, uranium-238 (<sup>238</sup>U or U-238) can be bred to produce plutonium-239 and thorium-232 (<sup>232</sup>Th or Th-232) can be bred to produce uranium-233. Nuclear reactors in which this sort of breeding takes place are called '''nuclear breeder reactors'''.</div></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>For power generation, nuclear reactors are the centerpiece of [[nuclear power plant]]s. Up to this time, nuclear reactors for large scale power generation use energy released by [[nuclear fission]], which is highly <ins style="font-weight: bold; text-decoration: none;">[[</ins>exothermic<ins style="font-weight: bold; text-decoration: none;">]]</ins>, meaning each fission releases a relative large amount of heat per atom split. These nuclear fission reactions take place by a controlled [[nuclear chain reaction]] in the '''reactor core''' inside the reactor. The material undergoing the fission in the core is considered the '''nuclear fuel'''. The nuclear fuel consists of [[fissile isotope]]s, atoms of [[isotope]]s of high [[atomic number]] and [[Atomic mass|mass]] which can readily undergo fission to produce a nuclear chain reaction. The three most common fissile isotopes are [[uranium]]-235 (<sup>235</sup>U or U-235), plutonium-239 (<sup>239</sup>Pu or Pu-239), and uranium-233 (<sup>233</sup>U or U-233). Material that can be bred into such fissile isotopes may also be considered nuclear fuel. For example, uranium-238 (<sup>238</sup>U or U-238) can be bred to produce plutonium-239 and <ins style="font-weight: bold; text-decoration: none;">[[</ins>thorium<ins style="font-weight: bold; text-decoration: none;">]]</ins>-232 (<sup>232</sup>Th or Th-232) can be bred to produce uranium-233. Nuclear reactors in which this sort of breeding takes place are called '''nuclear breeder reactors'''.</div></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td></tr>
<tr><td class="diff-marker" data-marker="−"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div>Nuclear fission typically occurs when a neutron hits a fissile nucleus, splitting the nucleus into two smaller nuclei called [[nuclear fission products]] and a couple of neutrons. These newly released neutrons can then go on to cause further fission of other fissile nuclei, releasing more neutrons. A repetitive cycle of fissions and neutrons results in a chain reaction under the right conditions, which is the objective of a nuclear fission reactor. In such an operating reactor, there are many neutrons flying around in the core, and the concentration of these neutrons is often referred to as a ''neutron flux''. The numerous nuclear fissions in an operating reactor core release heat, which is used as thermal [[Power (physics)|power]], the usual ultimate goal of the reactor. A reactor has a number of '''control rods''' consisting of a material which captures neutrons. These control rods can be withdrawn from or inserted into the core to control the nuclear chain reaction. Inserting all of the control rods into the core will capture the neutrons and stop the chain reaction, effectively shutting down the reactor. A quick insertion of the control rods into the core for an emergency shutdown of the reactor is called a '''scram'''. Withdrawing the control rods in a precise manner is used to start up the reactor. There are also other means used for controlling the power level of a nuclear reactor.</div></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>Nuclear fission typically occurs when a neutron hits a fissile nucleus, splitting the nucleus into two smaller nuclei called [[nuclear fission products]] and a couple of neutrons. These newly released neutrons can then go on to cause further fission of other fissile nuclei, releasing more neutrons. A repetitive cycle of fissions and neutrons results in a chain reaction under the right conditions, which is the objective of a nuclear fission reactor. In such an operating reactor, there are many neutrons flying around in the core, and the concentration of these neutrons is often referred to as a ''neutron flux''. The numerous nuclear fissions in an operating reactor core release heat, which is used as thermal [[Power (physics)|power]], the usual ultimate goal of the reactor. A reactor has a number of '''control rods''' consisting of a material which <ins style="font-weight: bold; text-decoration: none;">[[Neutron capture|</ins>captures neutrons<ins style="font-weight: bold; text-decoration: none;">]]</ins>. These control rods can be withdrawn from or inserted into the core to control the nuclear chain reaction. Inserting all of the control rods into the core will capture the neutrons and stop the chain reaction, effectively shutting down the reactor. A quick insertion of the control rods into the core for an emergency shutdown of the reactor is called a '''scram'''. Withdrawing the control rods in a precise manner is used to start up the reactor. There are also other means used for controlling the power level of a nuclear reactor.</div></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>==Core==</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>==Core==</div></td></tr>
<tr><td class="diff-marker" data-marker="−"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div>A fission reactor core contains '''fuel elements''', which contain the nuclear fission fuel encased in '''cladding'''. The cladding is a solid material and pressure boundary which keeps the nuclear fuel and any fission products created inside each fuel element. The cladding is typically a metal alloy called [[zircalloy]] consisting largely of the metallic element [[zirconium]], which has a low [[neutron cross-section]], <del style="font-weight: bold; text-decoration: none;">an </del>affinity for absorbing neutrons. Zircalloy is reasonably strong, corrosion-resistant, and able to withstand high enough temperature for reactor operation. A common structure for a fuel element has been to have a zircalloy tube used as cladding to contain small cylindrical pellets of nuclear fuel throughout the tube length contained in the core. The fuel elements are commonly assembled into bundles called '''fuel modules'''; there are a number of such fuel modules inside a reactor core. Flowing reactor coolant fluid and a neutron moderator surround the fuel elements in the core. The same material may serve as both reactor coolant and moderator. One or more control rods, which can slide in and out, are commonly inserted into the fuel modules between fuel elements. To help the fuel in the core burn out more evenly, small neutron-absorbing poison "pellets", which typically contain boron-10, are often placed in some strategic locations inside the core. Although the initial fuel may not be particularly radioactive, once the reactor core has gone critical, the resulting fission products make the fuel elements very highly radioactive.</div></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>A fission reactor core contains '''fuel elements''', <ins style="font-weight: bold; text-decoration: none;">which are like "package structures" </ins>which contain the nuclear fission fuel encased in '''cladding'''. The cladding is a solid material and pressure boundary which keeps the nuclear fuel and any fission products created inside each fuel element. The cladding is typically a metal alloy called [[zircalloy]] consisting largely of the metallic <ins style="font-weight: bold; text-decoration: none;">[[chemical </ins>element<ins style="font-weight: bold; text-decoration: none;">]] </ins>[[zirconium]], which has a low [[neutron <ins style="font-weight: bold; text-decoration: none;">absortion </ins>cross-section]], <ins style="font-weight: bold; text-decoration: none;">a low </ins>affinity for absorbing neutrons. Zircalloy is <ins style="font-weight: bold; text-decoration: none;">also </ins>reasonably strong, corrosion-resistant, and able to withstand high enough temperature for reactor operation. A common structure for a fuel element has been to have a zircalloy tube used as cladding to contain small cylindrical pellets of nuclear fuel throughout the tube length contained in the core. The fuel elements are commonly assembled into bundles called '''fuel modules'''; there are a number of such fuel modules inside a reactor core. Flowing reactor coolant fluid and a neutron moderator surround the fuel elements in the core. The same material may serve as both reactor coolant and moderator. One or more control rods, which can slide in and out, are commonly inserted into the fuel modules between fuel elements. To help the fuel in the core burn out more evenly, small neutron-absorbing poison "pellets", which typically contain <ins style="font-weight: bold; text-decoration: none;">[[</ins>boron<ins style="font-weight: bold; text-decoration: none;">]]-10 (<sup>10</sup>B or B</ins>-10<ins style="font-weight: bold; text-decoration: none;">)</ins>, are often placed in some strategic locations inside the core. Although the initial fuel may not be particularly radioactive, once the reactor core has gone critical <ins style="font-weight: bold; text-decoration: none;">(been operating)</ins>, the resulting fission products make the fuel elements very highly radioactive.</div></td></tr>
<tr><td colspan="2" class="diff-side-deleted"></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div> </div></td></tr>
<tr><td colspan="2" class="diff-side-deleted"></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div><ins style="font-weight: bold; text-decoration: none;">The cladding of each fuel element must maintain its integrity, so as not to leak out any radioactive material into the coolant or the rest of the reactor plant. Cladding also should not swell up, narrowing the reactor coolant channel between the fuel elements, so as not to slow down coolant flow, which would allow heat and temperature to build up around that channel. This means the zircalloy cladding cannot reach excessively high temperature. For this reason and to prevent undesired boiling in pressurized water reactors, reactor power level is operationally limited.</ins></div></td></tr>
<tr><td colspan="2" class="diff-side-deleted"></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div> </div></td></tr>
<tr><td colspan="2" class="diff-side-deleted"></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div><ins style="font-weight: bold; text-decoration: none;">==Neutron moderators==</ins></div></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td></tr>
<tr><td class="diff-marker" data-marker="−"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div>The <del style="font-weight: bold; text-decoration: none;">cladding </del>of <del style="font-weight: bold; text-decoration: none;">each fuel element must </del>maintain <del style="font-weight: bold; text-decoration: none;">its integrity</del>, <del style="font-weight: bold; text-decoration: none;">so as not </del>to <del style="font-weight: bold; text-decoration: none;">leak out any radioactive </del>material <del style="font-weight: bold; text-decoration: none;">into </del>the <del style="font-weight: bold; text-decoration: none;">coolant or the rest </del>of the <del style="font-weight: bold; text-decoration: none;">reactor plant</del>, and to <del style="font-weight: bold; text-decoration: none;">not swell up</del>, <del style="font-weight: bold; text-decoration: none;">narrowing the reactor coolant channels between the </del>fuel <del style="font-weight: bold; text-decoration: none;">elements</del>, <del style="font-weight: bold; text-decoration: none;">so </del>as <del style="font-weight: bold; text-decoration: none;">not </del>to <del style="font-weight: bold; text-decoration: none;">slow down flow</del>, which <del style="font-weight: bold; text-decoration: none;">would allow heat and temperature </del>to <del style="font-weight: bold; text-decoration: none;">build up</del>. <del style="font-weight: bold; text-decoration: none;">This means </del>the <del style="font-weight: bold; text-decoration: none;">zircalloy cladding cannot reach excessively </del>high temperature. <del style="font-weight: bold; text-decoration: none;">For this reason and to prevent undesired boiling </del>in <del style="font-weight: bold; text-decoration: none;">pressurized </del>water <del style="font-weight: bold; text-decoration: none;">reactors, </del>reactor <del style="font-weight: bold; text-decoration: none;">power level is operationally limited</del>.</div></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>The <ins style="font-weight: bold; text-decoration: none;">probability </ins>of <ins style="font-weight: bold; text-decoration: none;">fission occurring depends on the type of fissile nucleus and the colliding neutron's kinetic energy, which is effectively proportional to the velocity of the neutron squared. Neutrons which are produced directly from fission are typically fast neutrons. To </ins>maintain <ins style="font-weight: bold; text-decoration: none;">a good, effective fission chain reaction</ins>, <ins style="font-weight: bold; text-decoration: none;">it is desirable for a neutron hitting a fissile nucleus to cause fission and </ins>to <ins style="font-weight: bold; text-decoration: none;">minimize the incidence of the fissile nucleus capturing the neutron. Slowly moving neutrons are more effective at causing fission. Collisions of faster neutrons with small nuclei slow down neutron. A </ins>material <ins style="font-weight: bold; text-decoration: none;">containing such nuclei which slow down neutrons is a '''neutron moderator'''. Slow neutrons that have a kinetic energy approximately equal to </ins>the <ins style="font-weight: bold; text-decoration: none;">thermal energy of surrounding molecules are referred to as ''thermal neutrons''. The process of slowing down faster neutrons to such thermal energy with a moderator can be called ''thermalization'' </ins>of the <ins style="font-weight: bold; text-decoration: none;">neutrons. </ins></div></td></tr>
<tr><td colspan="2" class="diff-side-deleted"></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div> </div></td></tr>
<tr><td colspan="2" class="diff-side-deleted"></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div><ins style="font-weight: bold; text-decoration: none;">The smallest nuclei are in [[hydrogen]]-1 (<sup>1</sup>H or H-1</ins>, <ins style="font-weight: bold; text-decoration: none;">also called light hydrogen or ''protium'') atoms </ins>and <ins style="font-weight: bold; text-decoration: none;">slow down neutrons for fission the best. H-1 nuclei have a small tendency </ins>to <ins style="font-weight: bold; text-decoration: none;">capture neutrons also</ins>, <ins style="font-weight: bold; text-decoration: none;">but are good enough to maintain a fission chain reaction anyway if modestly [[enriched uranium]] is used as a nuclear </ins>fuel<ins style="font-weight: bold; text-decoration: none;">. The easiest way to use H-1 as a moderator is to use purified</ins>, <ins style="font-weight: bold; text-decoration: none;">normal water (called ''light water'') </ins>as <ins style="font-weight: bold; text-decoration: none;">both a moderator and a coolant to carry away heat simultaneously. The hydrogen in such light water is practically 100% H-1. A nuclear reactor which uses such light water is called a ''light water reactor'', of course. </ins></div></td></tr>
<tr><td colspan="2" class="diff-side-deleted"></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div> </div></td></tr>
<tr><td colspan="2" class="diff-side-deleted"></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div><ins style="font-weight: bold; text-decoration: none;">The second smallest nuclei are in hydrogen-2 (<sup>2</sup>H, H-2, or D, also called ''heavy hydrogen'' or ''[[deuterium]]'') atoms and moderate neutrons for fission quite well also. The tendency for H-2 nuclei </ins>to <ins style="font-weight: bold; text-decoration: none;">capture neutrons is practically negligible</ins>, which <ins style="font-weight: bold; text-decoration: none;">is good enough </ins>to <ins style="font-weight: bold; text-decoration: none;">maintain a fission chain reaction even with unenriched uranium</ins>. <ins style="font-weight: bold; text-decoration: none;">Similarly, </ins>the <ins style="font-weight: bold; text-decoration: none;">easiest way to use H-2 as a moderator is to use purified, ''heavy water'' (deuterium oxide, often symbolized as D<sub>2</sub>O) as both a moderator and coolant. Heavy water contains H-2 atoms instead of H-1. A nuclear reactor using heavy water is analogously called a ''heavy water reactor''. </ins></div></td></tr>
<tr><td colspan="2" class="diff-side-deleted"></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div> </div></td></tr>
<tr><td colspan="2" class="diff-side-deleted"></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div><ins style="font-weight: bold; text-decoration: none;">[[Carbon]] of [[natural isotopic abundance]] is a solid mostly of carbon-12 (<sup>12</sup>C or C-12) and able to withstand very </ins>high temperature <ins style="font-weight: bold; text-decoration: none;">when in the absence of [[oxygen]]</ins>. <ins style="font-weight: bold; text-decoration: none;">Carbon can be used </ins>in <ins style="font-weight: bold; text-decoration: none;">the form of [[graphite]] as a moderator, but not as a coolant since a solid does not flow. Some fluid such as </ins>water <ins style="font-weight: bold; text-decoration: none;">would then be used as the reactor coolant to carry away the heat produced. [[RBMK </ins>reactor<ins style="font-weight: bold; text-decoration: none;">]]s of formerly [[Soviet Union]] countries used carbon as the moderator</ins>. <ins style="font-weight: bold; text-decoration: none;"> </ins></div></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td></tr>
<tr><td class="diff-marker" data-marker="−"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div><del style="font-weight: bold; text-decoration: none;">==Moderators==</del></div></td><td colspan="2" class="diff-side-added"></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>==Cooling==</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>==Cooling==</div></td></tr>
<tr><td colspan="2" class="diff-side-deleted"></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div><ins style="font-weight: bold; text-decoration: none;"></ins></div></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>Reactors of any appreciable size are liquid- or gas-cooled. The most common liquid coolant is highly purified [[water]], or "light water" to differentiate it from [[heavy water]]. Heavy water cooling, which plays a part in moderation, has specific applications in reactors that produce plutonium or tritium. For some power producing reactors, there has been continuing experimentation with liquid sodium, which has advantages for heat transfer.</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>Reactors of any appreciable size are liquid- or gas-cooled. The most common liquid coolant is highly purified [[water]], or "light water" to differentiate it from [[heavy water]]. Heavy water cooling, which plays a part in moderation, has specific applications in reactors that produce plutonium or tritium. For some power producing reactors, there has been continuing experimentation with liquid sodium, which has advantages for heat transfer.</div></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>==Output==</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>==Output==</div></td></tr>
</table>imported>Henry A. Padleckashttps://citizendium.org/wiki/index.php?title=Nuclear_reactor&diff=787546&oldid=previmported>Henry A. Padleckas: /* Core */ writing "Core" section2012-11-10T04:32:52Z<p><span dir="auto"><span class="autocomment">Core: </span> writing "Core" section</span></p>
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<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>==Core==</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>==Core==</div></td></tr>
<tr><td colspan="2" class="diff-side-deleted"></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div><ins style="font-weight: bold; text-decoration: none;">A fission reactor core contains '''fuel elements''', which contain the nuclear fission fuel encased in '''cladding'''. The cladding is a solid material and pressure boundary which keeps the nuclear fuel and any fission products created inside each fuel element. The cladding is typically a metal alloy called [[zircalloy]] consisting largely of the metallic element [[zirconium]], which has a low [[neutron cross-section]], an affinity for absorbing neutrons. Zircalloy is reasonably strong, corrosion-resistant, and able to withstand high enough temperature for reactor operation. A common structure for a fuel element has been to have a zircalloy tube used as cladding to contain small cylindrical pellets of nuclear fuel throughout the tube length contained in the core. The fuel elements are commonly assembled into bundles called '''fuel modules'''; there are a number of such fuel modules inside a reactor core. Flowing reactor coolant fluid and a neutron moderator surround the fuel elements in the core. The same material may serve as both reactor coolant and moderator. One or more control rods, which can slide in and out, are commonly inserted into the fuel modules between fuel elements. To help the fuel in the core burn out more evenly, small neutron-absorbing poison "pellets", which typically contain boron-10, are often placed in some strategic locations inside the core. Although the initial fuel may not be particularly radioactive, once the reactor core has gone critical, the resulting fission products make the fuel elements very highly radioactive.</ins></div></td></tr>
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<tr><td colspan="2" class="diff-side-deleted"></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div><ins style="font-weight: bold; text-decoration: none;">The cladding of each fuel element must maintain its integrity, so as not to leak out any radioactive material into the coolant or the rest of the reactor plant, and to not swell up, narrowing the reactor coolant channels between the fuel elements, so as not to slow down flow, which would allow heat and temperature to build up. This means the zircalloy cladding cannot reach excessively high temperature. For this reason and to prevent undesired boiling in pressurized water reactors, reactor power level is operationally limited.</ins></div></td></tr>
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</table>imported>Henry A. Padleckashttps://citizendium.org/wiki/index.php?title=Nuclear_reactor&diff=787542&oldid=previmported>Henry A. Padleckas: /* Fundamentals of nuclear fission reactors */ discussed neutron flux and control rods in fission chain reaction2012-11-08T06:48:31Z<p><span dir="auto"><span class="autocomment">Fundamentals of nuclear fission reactors: </span> discussed neutron flux and control rods in fission chain reaction</span></p>
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<td colspan="2" style="background-color: #fff; color: #202122; text-align: center;">Revision as of 01:48, 8 November 2012</td>
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<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br/></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>For power generation, nuclear reactors are the centerpiece of [[nuclear power plant]]s. Up to this time, nuclear reactors for large scale power generation use energy released by [[nuclear fission]], which is highly exothermic, meaning each fission releases a relative large amount of heat per atom split. These nuclear fission reactions take place by a controlled [[nuclear chain reaction]] in the '''reactor core''' inside the reactor. The material undergoing the fission in the core is considered the '''nuclear fuel'''. The nuclear fuel consists of [[fissile isotope]]s, atoms of [[isotope]]s of high [[atomic number]] and [[Atomic mass|mass]] which can readily undergo fission to produce a nuclear chain reaction. The three most common fissile isotopes are [[uranium]]-235 (<sup>235</sup>U or U-235), plutonium-239 (<sup>239</sup>Pu or Pu-239), and uranium-233 (<sup>233</sup>U or U-233). Material that can be bred into such fissile isotopes may also be considered nuclear fuel. For example, uranium-238 (<sup>238</sup>U or U-238) can be bred to produce plutonium-239 and thorium-232 (<sup>232</sup>Th or Th-232) can be bred to produce uranium-233. Nuclear reactors in which this sort of breeding takes place are called '''nuclear breeder reactors'''.</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>For power generation, nuclear reactors are the centerpiece of [[nuclear power plant]]s. Up to this time, nuclear reactors for large scale power generation use energy released by [[nuclear fission]], which is highly exothermic, meaning each fission releases a relative large amount of heat per atom split. These nuclear fission reactions take place by a controlled [[nuclear chain reaction]] in the '''reactor core''' inside the reactor. The material undergoing the fission in the core is considered the '''nuclear fuel'''. The nuclear fuel consists of [[fissile isotope]]s, atoms of [[isotope]]s of high [[atomic number]] and [[Atomic mass|mass]] which can readily undergo fission to produce a nuclear chain reaction. The three most common fissile isotopes are [[uranium]]-235 (<sup>235</sup>U or U-235), plutonium-239 (<sup>239</sup>Pu or Pu-239), and uranium-233 (<sup>233</sup>U or U-233). Material that can be bred into such fissile isotopes may also be considered nuclear fuel. For example, uranium-238 (<sup>238</sup>U or U-238) can be bred to produce plutonium-239 and thorium-232 (<sup>232</sup>Th or Th-232) can be bred to produce uranium-233. Nuclear reactors in which this sort of breeding takes place are called '''nuclear breeder reactors'''.</div></td></tr>
<tr><td colspan="2" class="diff-side-deleted"></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div><ins style="font-weight: bold; text-decoration: none;"></ins></div></td></tr>
<tr><td colspan="2" class="diff-side-deleted"></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div><ins style="font-weight: bold; text-decoration: none;">Nuclear fission typically occurs when a neutron hits a fissile nucleus, splitting the nucleus into two smaller nuclei called [[nuclear fission products]] and a couple of neutrons. These newly released neutrons can then go on to cause further fission of other fissile nuclei, releasing more neutrons. A repetitive cycle of fissions and neutrons results in a chain reaction under the right conditions, which is the objective of a nuclear fission reactor. In such an operating reactor, there are many neutrons flying around in the core, and the concentration of these neutrons is often referred to as a ''neutron flux''. The numerous nuclear fissions in an operating reactor core release heat, which is used as thermal [[Power (physics)|power]], the usual ultimate goal of the reactor. A reactor has a number of '''control rods''' consisting of a material which captures neutrons. These control rods can be withdrawn from or inserted into the core to control the nuclear chain reaction. Inserting all of the control rods into the core will capture the neutrons and stop the chain reaction, effectively shutting down the reactor. A quick insertion of the control rods into the core for an emergency shutdown of the reactor is called a '''scram'''. Withdrawing the control rods in a precise manner is used to start up the reactor. There are also other means used for controlling the power level of a nuclear reactor.</ins></div></td></tr>
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</table>imported>Henry A. Padleckas