{"id":257,"date":"2015-11-18T17:41:41","date_gmt":"2015-11-18T17:41:41","guid":{"rendered":"http:\/\/sitepourvtc.com\/?page_id=257"},"modified":"2022-11-14T08:46:15","modified_gmt":"2022-11-14T08:46:15","slug":"reactor-physics","status":"publish","type":"page","link":"https:\/\/sitepourvtc.com\/nuclear-power\/reactor-physics\/","title":{"rendered":"Reactor Physics"},"content":{"rendered":"<p style=\"text-align: center;\"><a href=\"#\" class=\"sue-icon\" style=\"font-size:25px;color:#333333;margin:0px 20px 20px 0px\" target=\"_self\"><i class=\"sui sui-arrow-circle-up\" style=\"font-size:30px;line-height:30px;background:#eeeeee;color:#777777;-webkit-border-radius:60px;-moz-border-radius:60px;border-radius:60px;padding:4px\"><\/i><span class=\"sue-icon-text\">Mega menu<\/span><\/a>\n<p style=\"text-align: center;\"><a href=\"#\" class=\"sue-icon\" style=\"font-size:25px;color:#333333;margin:0px 20px 20px 0px\" target=\"_self\"><i class=\"sui sui-arrow-circle-down\" style=\"font-size:30px;line-height:30px;background:#eeeeee;color:#777777;-webkit-border-radius:60px;-moz-border-radius:60px;border-radius:60px;padding:4px\"><\/i><span class=\"sue-icon-text\">Thematic menu<\/span><\/a>\n<div   id="8n9s8rpp6h"    class=\"sue-shadow-wrap sue-content-wrap sue-shadow-inline-no\"><div   id="8n9s8rpp6h"    class=\"sue-shadow sue-shadow-style-vertical\">\n<div   id="8n9s8rpp6h"    class=\"sue-panel\" data-url=\"\" data-target=\"self\" style=\"background-color:#ffffff;color:#333333;border-radius:0px;-moz-border-radius:0px;-webkit-border-radius:0px;box-shadow:none;-moz-box-shadow:none;-webkit-box-shadow:none;border:1px solid #cccccc\"><div   id="8n9s8rpp6h"    class=\"sue-panel-content sue-content-wrap\" style=\"padding:15px;text-align:left\">\n<div class=\"su-heading su-heading-style-modern-1-dark su-heading-align-left\" id=\"\" style=\"font-size:13px;margin-bottom:20px\"><div   id="8n9s8rpp6h"    class=\"su-heading-inner\">\n<h2>Reactor Physics<\/h2>\n<\/div><\/div>\n<h3>What is nuclear reactor physics?<\/h3>\n<p>Nuclear reactor physics is the field of physics that studies and deals with the applied study and engineering applications of neutron diffusion and fission chain reaction to induce a controlled fission rate in a nuclear reactor for energy production. The nuclear reactor theory is based on <strong>diffusion theory<\/strong> and <strong>reactor dynamics<\/strong>, which defines the \u201c<strong>criticality<\/strong>\u201d of the reactor.<\/p>\n<h3>Key Facts<\/h3>\n<ul>\n<li>The study of\u00a0<a href=\"http:\/\/sitepourvtc.com\/nuclear-power\/reactor-physics\/nuclear-engineering-fundamentals\/neutron-nuclear-reactions\/\"><strong>neutron nuclear reactions<\/strong><\/a>\u00a0and\u00a0<a title=\"Nuclear Reactions\" href=\"http:\/\/sitepourvtc.com\/nuclear-power\/nuclear-reactions\/\">nuclear reactions<\/a>, in general, is of paramount importance in the <a title=\"Reactor Physics\" href=\"http:\/\/sitepourvtc.com\/nuclear-power\/reactor-physics\/\">physics of nuclear reactors<\/a>.<\/li>\n<li><a href=\"http:\/\/sitepourvtc.com\/nuclear-power\/fission\/\"><strong>Nuclear fission<\/strong><\/a>\u00a0is a\u00a0<a title=\"Neutron Nuclear Reactions\" href=\"http:\/\/sitepourvtc.com\/nuclear-power\/reactor-physics\/nuclear-engineering-fundamentals\/neutron-nuclear-reactions\/\">nuclear reaction<\/a> or a decay process in which the heavy nucleus\u00a0<strong>splits<\/strong>\u00a0into smaller parts (lighter nuclei).<\/li>\n<li>In nuclear physics, the <a href=\"http:\/\/sitepourvtc.com\/neutron-cross-section\/\">nuclear cross-section<\/a> of a nucleus is commonly used to characterize the\u00a0<strong>probability<\/strong>\u00a0that a\u00a0<a title=\"Nuclear Reactions\" href=\"http:\/\/sitepourvtc.com\/nuclear-power\/nuclear-reactions\/\">nuclear reaction<\/a>\u00a0will occur.<\/li>\n<li><strong><a href=\"http:\/\/sitepourvtc.com\/glossary\/doppler-broadening\/\">Doppler broadening<\/a> of the resonance capture cross-sections<\/strong>\u00a0of the\u00a0<a title=\"Fertile Material\" href=\"http:\/\/sitepourvtc.com\/glossary\/fertile-material\/\">fertile material<\/a> (e.g.,,<a title=\"Uranium 238\" href=\"http:\/\/sitepourvtc.com\/nuclear-power-plant\/nuclear-fuel\/uranium\/uranium-238\/\">\u00a0<sup>238<\/sup>U<\/a>\u00a0or<a title=\"Plutonium 240\" href=\"http:\/\/sitepourvtc.com\/nuclear-power-plant\/nuclear-fuel\/plutonium\/plutonium-240\/\">\u00a0<sup>240<\/sup>Pu<\/a>) caused by the <strong>thermal motion of target nuclei<\/strong>\u00a0in the\u00a0<a title=\"Nuclear Fuel\" href=\"http:\/\/sitepourvtc.com\/nuclear-power-plant\/nuclear-fuel\/\">nuclear fuel<\/a> is of the highest importance for reactor stability.<\/li>\n<li>If the <strong><a href=\"http:\/\/sitepourvtc.com\/nuclear-power\/reactor-physics\/nuclear-fission-chain-reaction\/six-factor-formula-effective-multiplication-factor\/\">multiplication factor<\/a><\/strong> for a multiplying system is\u00a0<strong>equal to 1.0<\/strong>, the <a href=\"http:\/\/sitepourvtc.com\/nuclear-power\/reactor-physics\/nuclear-fission-chain-reaction\/\">chain reaction<\/a> will be<strong>\u00a0self-sustaining<\/strong>.<\/li>\n<li><a href=\"http:\/\/sitepourvtc.com\/nuclear-power\/reactor-physics\/neutron-diffusion-theory\/\"><strong>Neutron diffusion theory <\/strong><\/a>deals with the\u00a0<strong>spatial migration of neutrons<\/strong>\u00a0and helps to understand the relationships between\u00a0<strong>reactor size<\/strong>,\u00a0<strong>shape<\/strong>, and\u00a0<a title=\"Reactor Criticality\" href=\"http:\/\/sitepourvtc.com\/nuclear-power\/reactor-physics\/nuclear-fission-chain-reaction\/reactor-criticality\/\"><strong>criticality.<\/strong><\/a>\u00a0It is also used to determine the spatial flux distributions within power reactors.<\/li>\n<li><a href=\"http:\/\/sitepourvtc.com\/nuclear-power\/reactor-physics\/reactor-dynamics\/reactor-kinetics\/\"><strong>Nuclear reactor kinetics<\/strong><\/a> deals with transient\u00a0<strong>neutron flux changes<\/strong>\u00a0resulting from a departure from the critical state.<\/li>\n<li><a href=\"http:\/\/sitepourvtc.com\/nuclear-power\/reactor-physics\/reactor-dynamics\/\"><strong>Reactor dynamics<\/strong><\/a> is\u00a0also referred to as reactor kinetics\u00a0<strong>with<\/strong>\u00a0<a href=\"http:\/\/sitepourvtc.com\/nuclear-power\/reactor-physics\/nuclear-fission-chain-reaction\/reactivity-coefficients-reactivity-feedbacks\/\"><strong>feedbacks<\/strong><\/a>\u00a0and with spatial effects.<\/li>\n<li>Basic reactor operation physics includes these topics:\u00a0<strong><a title=\"Reactor Startup\" href=\"http:\/\/sitepourvtc.com\/nuclear-power\/reactor-physics\/reactor-operation\/reactor-startup\/\">Reactor Startup<\/a> (\u201c<a title=\"Criticality Approach \u2013 Startup to Minimum Load\" href=\"http:\/\/sitepourvtc.com\/nuclear-power\/reactor-physics\/reactor-operation\/reactor-startup\/criticality-approach-startup-to-minimum-load\/\">criticality approach<\/a>\u201d), <\/strong><strong><a title=\"Normal Operation \u2013 Reactor Control\" href=\"http:\/\/sitepourvtc.com\/nuclear-power\/reactor-physics\/reactor-operation\/normal-operation-reactor-control\/\">Control of the Reactor and Power Maneuvering<\/a><\/strong><a title=\"Normal Operation \u2013 Reactor Control\" href=\"http:\/\/sitepourvtc.com\/nuclear-power\/reactor-physics\/reactor-operation\/normal-operation-reactor-control\/\">,<\/a>\u00a0and\u00a0<a title=\"Spatial Xenon Oscillations\" href=\"http:\/\/sitepourvtc.com\/nuclear-power\/reactor-physics\/reactor-operation\/xenon-135\/spatial-xenon-oscillations\/\"><strong>Xenon Oscillations.<\/strong><\/a><\/li>\n<\/ul>\n<div   id="8n9s8rpp6h"    class=\"su-divider su-divider-style-dotted\" style=\"margin:10px 0;border-width:2px;border-color:#999999\"><\/div>\n<div   id="8n9s8rpp6h"    class=\"su-accordion su-u-trim\">\n<div   id="8n9s8rpp6h"    class=\"su-spoiler su-spoiler-style-modern-light su-spoiler-icon-plus su-spoiler-closed\" data-scroll-offset=\"0\"><div   id="8n9s8rpp6h"    class=\"su-spoiler-title\" tabindex=\"0\" role=\"button\"><span class=\"su-spoiler-icon\"><\/span>What is reactor physics used for?<\/div><div   id="8n9s8rpp6h"    class=\"su-spoiler-content su-u-clearfix su-u-trim\"><strong>What is reactor physics used for?<\/strong><\/p>\n<p>Facility operators, maintenance personnel, and technical staff can safely operate and maintain facility support systems only when they understand reactor physics.<\/p>\n<\/div><\/div>\n<div   id="8n9s8rpp6h"    class=\"su-spoiler su-spoiler-style-modern-light su-spoiler-icon-plus su-spoiler-closed\" data-scroll-offset=\"0\"><div   id="8n9s8rpp6h"    class=\"su-spoiler-title\" tabindex=\"0\" role=\"button\"><span class=\"su-spoiler-icon\"><\/span>What does reactor criticality mean?<\/div><div   id="8n9s8rpp6h"    class=\"su-spoiler-content su-u-clearfix su-u-trim\">\n<strong>What does reactor criticality mean?<\/strong><\/p>\n<p>If the multiplication factor for a multiplying system is\u00a0<strong>equal to 1.0<\/strong>, then there is\u00a0<strong>no change in neutron population<\/strong> in time, and the chain reaction will be<strong>\u00a0self-sustaining<\/strong>. This condition is known as\u00a0<strong>the critical state<\/strong>.<\/p>\n<\/div><\/div>\n<div   id="8n9s8rpp6h"    class=\"su-spoiler su-spoiler-style-modern-light su-spoiler-icon-plus su-spoiler-closed\" data-scroll-offset=\"0\"><div   id="8n9s8rpp6h"    class=\"su-spoiler-title\" tabindex=\"0\" role=\"button\"><span class=\"su-spoiler-icon\"><\/span>What are main types of nuclear reactions?<\/div><div   id="8n9s8rpp6h"    class=\"su-spoiler-content su-u-clearfix su-u-trim\">\n<strong>What is the difference between reactor kinetics and reactor dynamics?<\/strong><\/p>\n<p>In general:<\/p>\n<ul>\n<li><strong>Reactor Kinetics.\u00a0<\/strong>Reactor kinetics is the study of the time-dependence of the neutron flux for postulated changes in the macroscopic cross-sections. It is also referred to as reactor kinetics <strong>without feedbacks<\/strong>.<\/li>\n<li><strong>Reactor Dynamics.<\/strong> Reactor dynamics study the time-dependence of the neutron flux when the macroscopic cross-sections are allowed to depend in turn on the neutron flux level. It is also referred to as reactor kinetics <strong>with<\/strong>\u00a0<strong>feedbacks<\/strong>\u00a0and with spatial effects.<\/li>\n<\/ul>\n<\/div><\/div>\n<\/div>\n<\/div><\/div>\n<\/div><\/div>\n<div   id="8n9s8rpp6h"     class=\"lgc-column lgc-grid-parent lgc-grid-100 lgc-tablet-grid-100 lgc-mobile-grid-100 lgc-equal-heights \"><div   id="8n9s8rpp6h"     class=\"inside-grid-column\">\n<h2>Atomic and Nuclear Physics<\/h2>\n<figure id=\"attachment_120\" aria-describedby=\"caption-attachment-120\" style=\"width: 217px\" class=\"wp-caption alignright\"><a href=\"http:\/\/sitepourvtc.com\/wp-content\/uploads\/2014\/10\/nuclei_notation.jpg\"><img loading=\"lazy\" class=\"size-medium wp-image-120\" src=\"http:\/\/sitepourvtc.com\/wp-content\/uploads\/2014\/10\/nuclei_notation-227x300.jpg\" alt=\"Notation of nuclei\" width=\"227\" height=\"300\" srcset=\"https:\/\/sitepourvtc.com\/wp-content\/uploads\/2014\/10\/nuclei_notation-227x300.jpg 227w, https:\/\/sitepourvtc.com\/wp-content\/uploads\/2014\/10\/nuclei_notation-775x1024.jpg 775w, https:\/\/sitepourvtc.com\/wp-content\/uploads\/2014\/10\/nuclei_notation.jpg 880w\" sizes=\"(max-width: 227px) 100vw, 227px\" \/><\/a><figcaption id=\"caption-attachment-120\" class=\"wp-caption-text\">Notation of nuclei<br \/>Source: chemwiki.ucdavis.edu<\/figcaption><\/figure>\n<p>Knowledge of <strong>atomic and nuclear physics<\/strong> is essential to <strong>nuclear engineers<\/strong>\u00a0who deal with <a title=\"Nuclear Reactor\" href=\"http:\/\/sitepourvtc.com\/nuclear-power-plant\/nuclear-reactor\/\">nuclear reactors<\/a>. It should be noted that atomic and nuclear physics is a very extensive branch of science. Nuclear reactor physics belongs to applied physics, drawing from particle physics or nuclear chemistry. These branches have <strong>common fundamentals<\/strong>. Atomic and nuclear physics describe<strong> fundamental particles<\/strong> (i.e., electrons, protons, <a title=\"Neutron\" href=\"http:\/\/sitepourvtc.com\/nuclear-power\/reactor-physics\/atomic-nuclear-physics\/fundamental-particles\/neutron\/\" target=\"_blank\" rel=\"noopener\">neutrons<\/a>), structure, properties, and behavior. These physical fundamentals consist of:<\/p>\n<ul>\n<li><a title=\"Fundamental Particles\" href=\"http:\/\/sitepourvtc.com\/nuclear-power\/reactor-physics\/atomic-nuclear-physics\/fundamental-particles\/\" target=\"_blank\" rel=\"noopener\"><strong>Fundamental Particles<\/strong><\/a><\/li>\n<li><a title=\"Atomic and Nuclear Structure\" href=\"http:\/\/sitepourvtc.com\/nuclear-power\/reactor-physics\/atomic-nuclear-physics\/atomic-nuclear-structure\/\"><strong>Atomic and Nuclear Structure<\/strong><\/a><\/li>\n<li><a title=\"Nuclear Energy\" href=\"http:\/\/sitepourvtc.com\/nuclear-power\/nuclear-energy\/\" target=\"_blank\" rel=\"noopener\"><strong>Mass and Energy<\/strong><\/a><\/li>\n<li><a title=\"Radiation\" href=\"http:\/\/sitepourvtc.com\/nuclear-power\/reactor-physics\/atomic-nuclear-physics\/radiation\/\" target=\"_blank\" rel=\"noopener\"><strong>Radiation<\/strong><\/a><\/li>\n<li><a title=\"Nuclear Stability\" href=\"http:\/\/sitepourvtc.com\/nuclear-power\/reactor-physics\/atomic-nuclear-physics\/nuclear-stability\/\" target=\"_blank\" rel=\"noopener\"><strong>Nuclear Stability <\/strong><\/a><\/li>\n<li><a title=\"Radioactive Decay\" href=\"http:\/\/sitepourvtc.com\/nuclear-power\/reactor-physics\/atomic-nuclear-physics\/radioactive-decay\/\" target=\"_blank\" rel=\"noopener\"><strong>Radioactive Decay<\/strong><\/a><\/li>\n<li><a title=\"Nuclear Reactions\" href=\"http:\/\/sitepourvtc.com\/nuclear-power\/nuclear-reactions\/\" target=\"_blank\" rel=\"noopener\"><strong>Nuclear Reactions<\/strong><\/a><\/li>\n<li><a title=\"Binding Energy\" href=\"http:\/\/sitepourvtc.com\/nuclear-power\/reactor-physics\/atomic-nuclear-physics\/binding-energy\/\" target=\"_blank\" rel=\"noopener\"><strong>Binding Energy<\/strong><\/a><\/li>\n<\/ul>\n<p>See also: <a title=\"Atomic and Nuclear Physics\" href=\"http:\/\/sitepourvtc.com\/nuclear-power\/reactor-physics\/atomic-nuclear-physics\/\" target=\"_blank\" rel=\"noopener\">Atomic and Nuclear Physics<\/a><\/p>\n<h2>Interaction of Radiation with Matter<\/h2>\n<figure id=\"attachment_317\" aria-describedby=\"caption-attachment-317\" style=\"width: 164px\" class=\"wp-caption alignright\"><a href=\"http:\/\/sitepourvtc.com\/wp-content\/uploads\/2014\/11\/Alfa_beta_gamma_neutron_radiation.png\"><img loading=\"lazy\" class=\"size-medium wp-image-317\" src=\"http:\/\/sitepourvtc.com\/wp-content\/uploads\/2014\/11\/Alfa_beta_gamma_neutron_radiation-174x300.png\" alt=\"Interaction of Radiation with Matter\" width=\"174\" height=\"300\" srcset=\"https:\/\/sitepourvtc.com\/wp-content\/uploads\/2014\/11\/Alfa_beta_gamma_neutron_radiation-174x300.png 174w, https:\/\/sitepourvtc.com\/wp-content\/uploads\/2014\/11\/Alfa_beta_gamma_neutron_radiation-595x1024.png 595w, https:\/\/sitepourvtc.com\/wp-content\/uploads\/2014\/11\/Alfa_beta_gamma_neutron_radiation.png 680w\" sizes=\"(max-width: 174px) 100vw, 174px\" \/><\/a><figcaption id=\"caption-attachment-317\" class=\"wp-caption-text\">Interaction of Radiation with Matter<\/figcaption><\/figure>\n<p>The design of all <a title=\"Nuclear Reactor\" href=\"http:\/\/sitepourvtc.com\/nuclear-power-plant\/nuclear-reactor\/\"><strong>nuclear reactors<\/strong><\/a> and other nuclear systems depends fundamentally on how nuclear radiation interacts with matter. In a nuclear reactor, we typically encounter these<a title=\"Forms of Ionizing Radiation\" href=\"http:\/\/sitepourvtc.com\/nuclear-power\/reactor-physics\/atomic-nuclear-physics\/radiation\/forms-ionizing-radiation\/\" target=\"_blank\" rel=\"noopener\">\u00a0types of radiation<\/a>:<\/p>\n<ul>\n<li><strong><a title=\"Interaction of Heavy Charged Particles with Matter\" href=\"http:\/\/sitepourvtc.com\/nuclear-power\/reactor-physics\/interaction-radiation-matter\/interaction-heavy-charged-particles\/\">Interactions of heavy charged particles<\/a>\u00a0<\/strong><\/li>\n<li><a title=\"Interaction of Beta Radiation with Matter\" href=\"http:\/\/sitepourvtc.com\/nuclear-power\/reactor-physics\/interaction-radiation-matter\/interaction-beta-radiation\/\"><strong>Interactions of beta\u00a0radiation<\/strong><\/a><\/li>\n<li><a title=\"Interaction of Gamma Radiation with Matter\" href=\"http:\/\/sitepourvtc.com\/nuclear-power\/reactor-physics\/interaction-radiation-matter\/interaction-gamma-radiation-matter\/\"><strong>Interactions of gamma rays<\/strong><\/a><\/li>\n<li><a title=\"Interactions of Neutrons with Matter\" href=\"http:\/\/sitepourvtc.com\/nuclear-power\/reactor-physics\/atomic-nuclear-physics\/fundamental-particles\/neutron\/interactions-neutrons-matter\/\"><strong>Interactions of neutrons<\/strong><\/a><\/li>\n<li><a title=\"Nuclear Reactor as the Antineutrinos Source\" href=\"http:\/\/sitepourvtc.com\/nuclear-power\/reactor-physics\/atomic-nuclear-physics\/fundamental-particles\/antineutrino\/nuclear-reactor-antineutrino-source\/\"><strong>Reactor antineutrinos<\/strong><\/a><\/li>\n<\/ul>\n<p>See also: <a title=\"Interaction of Radiation with Matter\" href=\"http:\/\/sitepourvtc.com\/nuclear-power\/reactor-physics\/interaction-radiation-matter\/\">Interaction of Radiation with Matter<\/a><\/p>\n<h2>Neutron Diffusion Theory<\/h2>\n<p><strong>Neutron diffusion theory<\/strong> is the branch of science that studies the behavior and application of neutrons within the nuclear core or in various environments. Diffusion theory provides a theoretical basis for neutron-physical computer simulation of nuclear cores. The term <strong>theoretical <\/strong>has to be\u00a0emphasized.<\/p>\n<p>It is necessary to predict <strong>how the neutrons<\/strong> will be distributed throughout the system to<strong> design<\/strong> a <a title=\"Nuclear Reactor\" href=\"http:\/\/sitepourvtc.com\/nuclear-power-plant\/nuclear-reactor\/\"><strong>nuclear reactor<\/strong><\/a> properly. This, in general, is a difficult problem, for the neutrons move in a reactor in complicated paths as a result of <strong>repeated collisions<\/strong>. To a <strong>first approximation,<\/strong> the overall effect of these collisions is that the neutrons undergo a kind of diffusion in the reactor medium, much like the diffusion of one gas in another. This approximation allows solving such problems using <strong>the diffusion equation<\/strong>.<\/p>\n<h2>Nuclear Reactor\u00a0Theory<\/h2>\n<p>The nuclear reactor theory is based on <strong>diffusion theory<\/strong> and <strong>reactor dynamics<\/strong>, which defines the \u201c<strong>criticality<\/strong>\u201d of the reactor. Using the term \u201ccriticality\u201d may seem counter-intuitive as a way to describe normalcy. The word often describes situations with the potential for disaster. Nevertheless, in the context of nuclear power, \u201ccritical\u201d indicates that a reactor is operating safely, and the neutron flux and power level are stable. In a <strong>critical reactor<\/strong>, there is an exact balance between the number of neutrons produced in fission and the number lost, either by absorption in the reactor or by leaking from its surface. Nuclear reactor theory solves the central problem in the design of a reactor: calculation of the <strong>size and composition<\/strong> (<a title=\"Nuclear Fuel\" href=\"http:\/\/sitepourvtc.com\/nuclear-power-plant\/nuclear-fuel\/\" target=\"_blank\" rel=\"noopener\">nuclear fuel<\/a>) of the system required to maintain this balance.<\/p>\n<h2>Reactor Kinetics &#8211; Zero Power\u00a0Physics<\/h2>\n<figure id=\"attachment_228\" aria-describedby=\"caption-attachment-228\" style=\"width: 290px\" class=\"wp-caption alignright\"><a href=\"http:\/\/sitepourvtc.com\/wp-content\/uploads\/2014\/11\/reactor_criticality.png\"><img loading=\"lazy\" class=\"size-medium wp-image-228\" src=\"http:\/\/sitepourvtc.com\/wp-content\/uploads\/2014\/11\/reactor_criticality-300x258.png\" alt=\"Reactor criticality\" width=\"300\" height=\"258\" srcset=\"https:\/\/sitepourvtc.com\/wp-content\/uploads\/2014\/11\/reactor_criticality-300x258.png 300w, https:\/\/sitepourvtc.com\/wp-content\/uploads\/2014\/11\/reactor_criticality.png 387w\" sizes=\"(max-width: 300px) 100vw, 300px\" \/><\/a><figcaption id=\"caption-attachment-228\" class=\"wp-caption-text\">Reactor criticality. A &#8211; a supercritical state; B &#8211; a critical state; C &#8211; a subcritical state<\/figcaption><\/figure>\n<p>The nuclear reactor theory is concerned with <strong>critical<\/strong> nuclear reactors operating at constant power. But the reactor must not always be in a critical state. The reactor must be noncritical (supercritical or subcritical) to change the reactor power. The study of the behavior of neuron populations in a noncritical reactor is called <strong>reactor kinetics.<\/strong> This theory introduces a new unit &#8211; reactivity &#8211; of a nuclear reactor. The reactivity\u00a0characterizes the deflection of the reactor from the critical state.<\/p>\n<p>It should be noted this theory can be used for a reactor at low power levels, hence \u201c<strong>zero power criticality<\/strong>\u201d (i.e., a reactor without reactivity feedbacks, 10E-8% &#8211; 1% of rated power). The first periods of a reactor operation (reactor startup and power maneuvering at low power levels) are well described by this theory. Once the <a title=\"Reactor Core\" href=\"http:\/\/sitepourvtc.com\/nuclear-power-plant\/nuclear-reactor-core\/\" target=\"_blank\" rel=\"noopener\">reactor core<\/a> heats up (thermal power outweighs decay power), reactivity feedbacks change the dynamics of the reactor.<\/p>\n<h2>Reactor operation &#8211; Full Power Physics<\/h2>\n<figure id=\"attachment_322\" aria-describedby=\"caption-attachment-322\" style=\"width: 290px\" class=\"wp-caption alignright\"><a href=\"http:\/\/sitepourvtc.com\/wp-content\/uploads\/2014\/11\/Iodine_pit.png\"><img loading=\"lazy\" class=\"size-medium wp-image-322\" src=\"http:\/\/sitepourvtc.com\/wp-content\/uploads\/2014\/11\/Iodine_pit-300x212.png\" alt=\"Iodine pit - Xenon poisoning\" width=\"300\" height=\"212\" srcset=\"https:\/\/sitepourvtc.com\/wp-content\/uploads\/2014\/11\/Iodine_pit-300x212.png 300w, https:\/\/sitepourvtc.com\/wp-content\/uploads\/2014\/11\/Iodine_pit.png 400w\" sizes=\"(max-width: 300px) 100vw, 300px\" \/><\/a><figcaption id=\"caption-attachment-322\" class=\"wp-caption-text\">Iodine pit &#8211; Xenon poisoning<br \/>Source: wikipedia.org<\/figcaption><\/figure>\n<p>This branch of nuclear engineering is very specific and dependent on reactor type. This article focuses on the most common type of reactor &#8211; <a title=\"PWR \u2013 Pressurized water reactor\" href=\"http:\/\/sitepourvtc.com\/pwr-pressurized-water-reactor\/\">Pressurized Water Reactors<\/a>.\u00a0PWRs have much in common with <a title=\"BWR \u2013 Boiling water reactor\" href=\"http:\/\/sitepourvtc.com\/bwr-boiling-water-reactor\/\">Boiling Water Reactors<\/a>, but the operation of the reactors is not the same. On the other hand, for example, <a title=\"Fast Neutron Reactor\" href=\"http:\/\/sitepourvtc.com\/fast-neutron-reactor\/\" target=\"_blank\" rel=\"noopener\">fast neutron reactors<\/a> have completely different physics than PWRs and BWRs.<\/p>\n<p>The degree of criticality at high power levels (~1% &#8211; 100% of rated power) is influenced by many variables. The most important are summarized below.<\/p>\n<ul>\n<li><strong><a title=\"Nuclear Fuel\" href=\"http:\/\/sitepourvtc.com\/nuclear-power-plant\/nuclear-fuel\/\">Nuclear Fuel<\/a> and Fuel Loading Pattern<\/strong><\/li>\n<li><strong>Fuel Depletion<\/strong><\/li>\n<li><strong>Neutron Leakage<\/strong><\/li>\n<li><strong><a title=\"Control rods\" href=\"http:\/\/sitepourvtc.com\/nuclear-power-plant\/control-rods\/\">Control Rods<\/a> and Chemical Shim<\/strong><\/li>\n<li><strong>Reactivity Feedbacks<\/strong><\/li>\n<li><strong>Burnable Absorbers<\/strong><\/li>\n<li><strong>Xenon and Samarium Poisoning<\/strong><\/li>\n<\/ul>\n<p>Basic reactor operation physics includes these operation states:<\/p>\n<ul>\n<li><strong>Reactor Startup (\u201cgoing critical\u201d)<\/strong><\/li>\n<li><strong>Control of the Reactor and Power Maneuvering.<\/strong><\/li>\n<li><strong>Axial Offset Control.<\/strong><\/li>\n<li><strong>Xenon Oscillations<\/strong><\/li>\n<li><strong>Reactor Shutdown.<\/strong><\/li>\n<li><strong>Emergency Shutdown \u2013 SCRAM<\/strong><\/li>\n<\/ul>\n<h2>Thermohydraulics of Nuclear Core<\/h2>\n<figure id=\"attachment_329\" aria-describedby=\"caption-attachment-329\" style=\"width: 290px\" class=\"wp-caption alignright\"><a href=\"http:\/\/sitepourvtc.com\/wp-content\/uploads\/2014\/11\/DNB_critical_heat_flux.jpg\"><img loading=\"lazy\" class=\"size-medium wp-image-329\" src=\"http:\/\/sitepourvtc.com\/wp-content\/uploads\/2014\/11\/DNB_critical_heat_flux-300x225.jpg\" alt=\"critical heat flux and DNB (Departure from Nucleate Boiling)\" width=\"300\" height=\"225\" srcset=\"https:\/\/sitepourvtc.com\/wp-content\/uploads\/2014\/11\/DNB_critical_heat_flux-300x225.jpg 300w, https:\/\/sitepourvtc.com\/wp-content\/uploads\/2014\/11\/DNB_critical_heat_flux.jpg 600w\" sizes=\"(max-width: 300px) 100vw, 300px\" \/><\/a><figcaption id=\"caption-attachment-329\" class=\"wp-caption-text\">If the heat flux of a boiling system is higher than the critical heat flux, then DNB (Departure from Nucleate Boiling) may occur.<\/figcaption><\/figure>\n<p>Heat removal from nuclear reactors is also a key issue of reactor physics. For a reactor to operate in a steady state, with an internal power distribution that is independent of time, all of the heat released in the system must be removed as fast as it is produced. This is accomplished by passing a coolant (water in case of PWRs or BWRs) through the core and other regions where heat is generated.<\/p>\n<p>The thermohydraulics deals with thermal behavior (heat generation, heat removal) and the nuclear core\u2019s hydraulic behavior (Delta P, cross-flow issue, flow pattern). The nature and operation of this coolant system are some of the most important considerations in designing a nuclear reactor. In the PWR reactors, some phenomena must be avoided. Namely, DNB (Departure from Nucleate Boiling) and coolant saturation are very dangerous phenomena.<\/p>\n<h2>The behavior of Fuel Rod<\/h2>\n<p>The thermal and mechanical behavior of <a title=\"Nuclear Fuel\" href=\"http:\/\/sitepourvtc.com\/nuclear-power-plant\/nuclear-fuel\/\" target=\"_blank\" rel=\"noopener\">nuclear fuel<\/a> constitutes one of three key core design disciplines. Nuclear fuel is operated under inhospitable conditions (thermal, radiation, mechanical) and must withstand more than normal conditions operation. For example, temperatures in the center of fuel pellets reach more than 1000\u00b0C (1832\u00b0F), accompanied by fission-gas releases. The behavior of nuclear fuel is associated with many phenomena. The most important are summarized below.<\/p>\n<ul>\n<li><strong>Fuel swelling<\/strong><\/li>\n<li><strong>Fuel densification<\/strong><\/li>\n<li><strong>Thermal expansion<\/strong><\/li>\n<li><strong>Fuel relocation<\/strong><\/li>\n<li><strong>High Burnup Structure<\/strong><\/li>\n<li><strong>Pellet-Cladding Interaction<\/strong><\/li>\n<li><strong>Pellet-Coolant Interaction<\/strong><\/li>\n<li><strong>Fission-Gas Releases<\/strong><\/li>\n<\/ul>\n<h2>Applied Core Physics<\/h2>\n<p>Applied core physics is the branch of science that deals with studying the behavior of a <strong>specific reactor core<\/strong>, which depends on a specific refueling schema. As was written, during refueling, every 12 to 18 months, some of the fuel \u2013 usually <strong>one-third or one-quarter of the core<\/strong> \u2013 is removed to the\u00a0<strong>spent fuel pool. At the same time,<\/strong> the remainder is rearranged to a location in the core better suited to its remaining level of enrichment. The removed fuel (one-third or one-quarter of the core, i.e., 40 assemblies) must be replaced by <strong>fresh fuel assemblies<\/strong>.<\/p>\n<p>For every fuel reload, plant operators shall determine main core characteristics (e.g.,, power distribution). Plant operators shall verify that these main core characteristics do not violate the initial and boundary conditions used in the Safety Analyses Report (SAR).<\/p>\n<p>Full-scale physical computing of reactor core includes these types of computations:<\/p>\n<ul>\n<li>Core Design computing\n<ul>\n<li><strong>Fuel cross-section computing<\/strong>. <a title=\"Neutron cross-section\" href=\"http:\/\/sitepourvtc.com\/neutron-cross-section\/\" target=\"_blank\" rel=\"noopener\">Neutron cross-sections<\/a> must be calculated for new fuel assemblies, usually in two-Dimensional models of the fuel lattice.<\/li>\n<li><strong>Loading Pattern search<\/strong>.\u00a0The best <strong>arrangement<\/strong> of new fuel assemblies and used fuel assemblies are searched for in the core design from the viewpoints of <strong>safety<\/strong> and economy.<\/li>\n<li><strong>Fuel Cycle depletion<\/strong>. Each proposed fuel cycle\u2019s behavior and key safety parameters (power distribution, reactor kinetics parameters, control rods efficiency, etc.) must be analyzed for the entire duration of the proposed cycle.<\/li>\n<\/ul>\n<\/li>\n<li>Reload Safety Assessment\n<ul>\n<li><strong>Neutron-physical computing<\/strong><\/li>\n<li><strong>Thermal-hydraulic computing<\/strong><\/li>\n<li><strong>Fuel rod behavior computing<\/strong><\/li>\n<\/ul>\n<\/li>\n<\/ul>\n<h2>\u00a0Safety of Nuclear Reactors<\/h2>\n<p><strong>Meaning of \u2018(nuclear) safety\u2019\u00a0<\/strong><\/p>\n<p><a title=\"Definition of Safety\" href=\"http:\/\/www-ns.iaea.org\/standards\/concepts-terms.asp\">Definition by IAEA:<\/a><\/p>\n<p><em>\u2018Safety\u2019 is the achievement of proper operating conditions, prevention of accidents, and mitigation of accident consequences, resulting in the protection of workers, the public, and the environment from undue radiation hazards.<\/em><\/p>\n<p>Nuclear safety is a very broad branch of nuclear engineering. The three primary objectives of nuclear reactor safety systems as defined by the <a title=\"NRC\" href=\"http:\/\/www.nrc.gov\" class=\"broken_link\">U.S. Nuclear Regulatory Commission<\/a> are to shut down the reactor, maintain it in a shutdown condition, and prevent the release of radioactive material. Appropriate redundant and diverse safety systems are installed to ensure the safety of the nuclear reactor.<\/p>\n<p>Most nuclear power plants introduce a \u2018<b>defense-in-depth<\/b>\u2019 approach to achieve maximum safety. This approach is constituted of multiple safety systems supplementing the natural features of the reactor core.<\/p>\n<p>&nbsp;<\/p>\n<p>&nbsp;<\/p>\n<\/div><\/div>\n","protected":false},"excerpt":{"rendered":"","protected":false},"author":1,"featured_media":0,"parent":52,"menu_order":5,"comment_status":"closed","ping_status":"closed","template":"","meta":{"generate_page_header":""},"_links":{"self":[{"href":"https:\/\/sitepourvtc.com\/wp-json\/wp\/v2\/pages\/257"}],"collection":[{"href":"https:\/\/sitepourvtc.com\/wp-json\/wp\/v2\/pages"}],"about":[{"href":"https:\/\/sitepourvtc.com\/wp-json\/wp\/v2\/types\/page"}],"author":[{"embeddable":true,"href":"https:\/\/sitepourvtc.com\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/sitepourvtc.com\/wp-json\/wp\/v2\/comments?post=257"}],"version-history":[{"count":8,"href":"https:\/\/sitepourvtc.com\/wp-json\/wp\/v2\/pages\/257\/revisions"}],"predecessor-version":[{"id":35173,"href":"https:\/\/sitepourvtc.com\/wp-json\/wp\/v2\/pages\/257\/revisions\/35173"}],"up":[{"embeddable":true,"href":"https:\/\/sitepourvtc.com\/wp-json\/wp\/v2\/pages\/52"}],"wp:attachment":[{"href":"https:\/\/sitepourvtc.com\/wp-json\/wp\/v2\/media?parent=257"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}