{"id":26704,"date":"2020-03-14T12:19:39","date_gmt":"2020-03-14T12:19:39","guid":{"rendered":"http:\/\/sitepourvtc.com\/?page_id=26704"},"modified":"2023-07-14T09:14:52","modified_gmt":"2023-07-14T09:14:52","slug":"nuclear-instrumentation","status":"publish","type":"page","link":"https:\/\/sitepourvtc.com\/nuclear-power-plant\/nuclear-reactor\/nuclear-instrumentation\/","title":{"rendered":"Nuclear Instrumentation"},"content":{"rendered":"<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<p>In <a href=\"http:\/\/sitepourvtc.com\/nuclear-power-plant\/what-is-nuclear-reactor\/\">nuclear reactors<\/a>, the thermal power produced by nuclear fissions is proportional to the neutron flux level. Therefore, from a reactor safety point of view, it is of the highest importance to measure and control <strong>the neutron flux and the spatial distribution of the neutron flux <\/strong>in the reactor <strong>correctly <\/strong>and by appropriate instrumentation. For this purpose, various nuclear instrumentations are installed. These measurements are usually performed outside the reactor core, but there are also measurements performed from inside the core. Therefore, nuclear instrumentations are usually categorized as:<\/p>\n<ul>\n<li style=\"list-style-type: none;\">\n<ul>\n<li><strong><\/strong><strong><a href=\"http:\/\/sitepourvtc.com\/nuclear-power-plant\/nuclear-reactor\/nuclear-instrumentation\/excore-nuclear-instrumentation\/\">Excore Nuclear Instrumentation<\/a>.\u00a0<\/strong>The neutron flux is usually measured by <strong>excore neutron detectors <\/strong>installed outside the core. These detectors belong to the <strong>excore nuclear instrumentation system (NIS)<\/strong>. Since the neutron flux covers a wide range (about 12 decades), three ranges of instrumentation are used to obtain accurate flux level measurements:\n<ul>\n<li><a href=\"http:\/\/sitepourvtc.com\/nuclear-power-plant\/nuclear-reactor\/nuclear-instrumentation\/excore-nuclear-instrumentation\/source-range-detectors\/\"><strong>Source Range Detectors<\/strong><\/a><\/li>\n<li><a href=\"http:\/\/sitepourvtc.com\/nuclear-power-plant\/nuclear-reactor\/nuclear-instrumentation\/excore-nuclear-instrumentation\/intermediate-range-detectors\/\"><strong>Intermediate-Range \u00a0Detectors<\/strong><\/a><\/li>\n<li><a href=\"http:\/\/sitepourvtc.com\/nuclear-power-plant\/nuclear-reactor\/nuclear-instrumentation\/excore-nuclear-instrumentation\/power-range-detectors\/\"><strong>Power Range \u00a0Detectors<\/strong><\/a><\/li>\n<\/ul>\n<\/li>\n<li><strong><\/strong><strong><a href=\"http:\/\/sitepourvtc.com\/nuclear-power-plant\/nuclear-reactor\/nuclear-instrumentation\/incore-nuclear-instrumentation\/\">Incore Nuclear Instrumentation<\/a>.\u00a0<\/strong>The incore nuclear instrumentation system measures neutron flux distribution and temperatures in the reactor core. The purposes of the incore instrumentation system are to provide detailed information on neutron flux distribution and fuel assembly outlet temperatures at selected core locations. The incore instrumentation system includes:\n<ul>\n<li><a href=\"http:\/\/sitepourvtc.com\/nuclear-power-plant\/nuclear-reactor\/nuclear-instrumentation\/incore-nuclear-instrumentation\/incore-neutron-flux-monitoring-system\/\"><strong>Incore neutron flux monitoring system<\/strong><\/a><\/li>\n<li><a href=\"http:\/\/sitepourvtc.com\/nuclear-power-plant\/nuclear-reactor\/nuclear-instrumentation\/incore-nuclear-instrumentation\/incore-temperature-monitoring-system\/\"><strong>Incore temperature monitoring system<\/strong><\/a><\/li>\n<\/ul>\n<\/li>\n<\/ul>\n<\/li>\n<\/ul>\n<p>Both systems are based on the detection of neutrons. The neutron flux is usually measured by <strong>excore neutron detectors <\/strong>installed outside the core. These detectors belong to the so-called <strong>excore nuclear instrumentation system (NIS)<\/strong>. The <strong>neutron flux<\/strong> and its <strong>distribution<\/strong> within the core are usually measured by an <strong>incore system<\/strong>\u00a0installed inside the reactor. Although the <strong>nuclear instrumentation system<\/strong> provides a prompt response to neutron flux changes and it is an irreplaceable system, <strong>it must be calibrated<\/strong>. The <strong>accurate thermal power<\/strong> of the reactor can be measured only by methods based on the <strong>energy balance<\/strong> of the primary circuit or the energy balance of the secondary circuit. These methods provide accurate reactor power, but these methods are insufficient for safety systems. Signal inputs to these calculations are, for example, the hot leg temperature or the flow rate through the feedwater system, and these signals change<strong> very slowly<\/strong> with neutron power changes. In other words, the thermal power measured by colorimetric methods is accurate. In contrast, the nuclear power measured by excore neutron detectors is the only system capable of fast reactivity excursion detection.<\/p>\n<h2>Reaction Rate &#8211; Proportionality between Neutron Flux and Thermal Power<\/h2>\n<p>See also: <a href=\"http:\/\/sitepourvtc.com\/nuclear-power\/reactor-physics\/nuclear-engineering-fundamentals\/neutron-nuclear-reactions\/reaction-rate\/\">Reaction Rate<\/a><\/p>\n<p>Knowledge of the\u00a0<a href=\"http:\/\/sitepourvtc.com\/nuclear-power\/reactor-physics\/nuclear-engineering-fundamentals\/neutron-nuclear-reactions\/neutron-flux-neutron-intensity\/\"><strong>neutron flux<\/strong>\u00a0<\/a>(the\u00a0<strong>total path length<\/strong>\u00a0of all the neutrons in a cubic centimeter in a second) and the<a href=\"http:\/\/sitepourvtc.com\/nuclear-power\/reactor-physics\/nuclear-engineering-fundamentals\/neutron-nuclear-reactions\/macroscopic-cross-section\/\"><strong>\u00a0macroscopic cross sections<\/strong><\/a>\u00a0(the probability of having an interaction\u00a0<strong>per centimeter path length<\/strong>) allows us to compute the rate of interactions (e.g., rate of fission reactions).\u00a0<strong>This reaction rate<\/strong>\u00a0(the number of interactions taking place in that cubic centimeter in one second) is then given by multiplying them together:<\/p>\n<p><a href=\"http:\/\/sitepourvtc.com\/wp-content\/uploads\/2016\/01\/Reaction-Rate-Neutron-Flux.png\"><img loading=\"lazy\" class=\"aligncenter size-full wp-image-13513\" src=\"http:\/\/sitepourvtc.com\/wp-content\/uploads\/2016\/01\/Reaction-Rate-Neutron-Flux.png\" alt=\"Reaction Rate - Neutron Flux\" width=\"548\" height=\"77\" srcset=\"https:\/\/sitepourvtc.com\/wp-content\/uploads\/2016\/01\/Reaction-Rate-Neutron-Flux.png 548w, https:\/\/sitepourvtc.com\/wp-content\/uploads\/2016\/01\/Reaction-Rate-Neutron-Flux-300x42.png 300w, https:\/\/sitepourvtc.com\/wp-content\/uploads\/2016\/01\/Reaction-Rate-Neutron-Flux-540x77.png 540w\" sizes=\"(max-width: 548px) 100vw, 548px\" \/><\/a><\/p>\n<p>where:<\/p>\n<p><strong>\u0424 \u2013\u00a0<a href=\"http:\/\/sitepourvtc.com\/nuclear-power\/reactor-physics\/nuclear-engineering-fundamentals\/neutron-nuclear-reactions\/neutron-flux-neutron-intensity\/\">neutron flux<\/a>\u00a0(neutrons.cm<\/strong><strong><sup>-2<\/sup><\/strong><strong>.s<\/strong><strong><sup>-1<\/sup><\/strong><strong>)<\/strong><\/p>\n<p><strong>\u03c3 \u2013\u00a0<a href=\"http:\/\/sitepourvtc.com\/nuclear-power\/reactor-physics\/nuclear-engineering-fundamentals\/neutron-nuclear-reactions\/microscopic-cross-section\/\">microscopic cross section<\/a>\u00a0(cm<\/strong><strong><sup>2<\/sup><\/strong><strong>)<\/strong><\/p>\n<p><strong>N \u2013\u00a0<a href=\"http:\/\/sitepourvtc.com\/nuclear-power\/reactor-physics\/nuclear-engineering-fundamentals\/neutron-nuclear-reactions\/atomic-number-density\/\">atomic number density<\/a>\u00a0(atoms.cm<\/strong><strong><sup>-3<\/sup><\/strong><strong>)<\/strong><\/p>\n<p>The reaction rate for various types of interactions is found from the appropriate cross-section type:<\/p>\n<ul>\n<li style=\"list-style-type: none;\">\n<ul>\n<li style=\"list-style-type: none;\">\n<ul>\n<li><strong>\u03a3<\/strong><strong><sub>t<\/sub><\/strong><strong>\u00a0. \u0424 \u2013 total reaction rate<\/strong><\/li>\n<li><strong>\u03a3<\/strong><strong><sub>a<\/sub><\/strong><strong>\u00a0. \u0424 \u2013\u00a0<a href=\"http:\/\/sitepourvtc.com\/nuclear-power\/reactor-physics\/nuclear-engineering-fundamentals\/neutron-nuclear-reactions\/neutron-absorption\/neutron-absorption-cross-section\/\">absorption<\/a>\u00a0reaction rate<\/strong><\/li>\n<li><strong>\u03a3<\/strong><strong><sub>c<\/sub><\/strong><strong>. \u0424 \u2013\u00a0<a href=\"http:\/\/sitepourvtc.com\/nuclear-power\/reactor-physics\/nuclear-engineering-fundamentals\/neutron-nuclear-reactions\/neutron-capture-radiative-capture\/\">radiative capture<\/a>\u00a0reaction rate<\/strong><\/li>\n<li><strong>\u03a3<\/strong><strong><sub>f<\/sub><\/strong><strong>. \u0424 \u2013\u00a0<a href=\"http:\/\/sitepourvtc.com\/nuclear-power\/fission\/\">fission reaction<\/a>\u00a0rate<\/strong><\/li>\n<\/ul>\n<\/li>\n<\/ul>\n<\/li>\n<\/ul>\n<p>We must focus on the <strong>fission reaction rate <\/strong>to determine<strong> the thermal power<\/strong>. For simplicity, let&#8217;s assume that the <a href=\"http:\/\/sitepourvtc.com\/glossary\/fissionable-material\/\">fissionable material<\/a>\u00a0is uniformly distributed in the reactor. In this case, the\u00a0<a href=\"http:\/\/sitepourvtc.com\/nuclear-power\/reactor-physics\/nuclear-engineering-fundamentals\/neutron-nuclear-reactions\/macroscopic-cross-section\/\">macroscopic cross-sections<\/a>\u00a0are independent of position. Multiplying the\u00a0<strong>fission reaction rate<\/strong>\u00a0per unit volume (<strong>RR = \u0424 . \u03a3<\/strong>) by the\u00a0<strong>total volume<\/strong>\u00a0of the core (V) gives us the<strong>\u00a0total number of reactions<\/strong>\u00a0occurring in the\u00a0<a href=\"http:\/\/sitepourvtc.com\/nuclear-power-plant\/nuclear-reactor-core\/\">reactor core<\/a> per unit time. But we also know that the amount of<a href=\"http:\/\/sitepourvtc.com\/nuclear-power\/fission\/energy-release-from-fission\/\">\u00a0energy released per one fission reaction<\/a> is about <strong>200 MeV\/fission<\/strong>. It is possible to determine the <strong>rate of energy release<\/strong> (power) due to the fission reaction, and it is given by the following equation:<\/p>\n<p><strong>P = RR . E<\/strong><strong><sub>r<\/sub><\/strong><strong>\u00a0. V = \u0424 . \u03a3<\/strong><strong><sub>f<\/sub><\/strong><strong>\u00a0. E<\/strong><strong><sub>r<\/sub><\/strong><strong>\u00a0. V = \u0424 . N<\/strong><strong><sub>U235<\/sub><\/strong><strong>\u00a0. \u03c3<\/strong><strong><sub>f<\/sub><\/strong><strong><sup>235<\/sup><\/strong><strong>\u00a0. E<\/strong><strong><sub>r<\/sub><\/strong><strong>\u00a0. V<\/strong><\/p>\n<p>where:<\/p>\n<p><strong>P \u2013 reactor power (MeV.s<\/strong><strong><sup>-1<\/sup><\/strong><strong>)<\/strong><\/p>\n<p><strong>\u0424 \u2013 neutron flux (neutrons.cm<\/strong><strong><sup>-2<\/sup><\/strong><strong>.s<\/strong><strong><sup>-1<\/sup><\/strong><strong>)<\/strong><\/p>\n<p><strong>\u03c3 \u2013 microscopic cross section (cm<\/strong><strong><sup>2<\/sup><\/strong><strong>)<\/strong><\/p>\n<p><strong>N \u2013 atomic number density (atoms.cm<\/strong><strong><sup>-3<\/sup><\/strong><strong>)<\/strong><\/p>\n<p><strong>Er \u2013 the average recoverable energy per fission (MeV \/ fission)<\/strong><\/p>\n<p><strong>V \u2013 total volume of the core (m<\/strong><strong><sup>3<\/sup><\/strong><strong>)<\/strong><\/p>\n<p>&nbsp;<\/p>\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\"><div   id="8n9s8rpp6h"    class=\"su-spoiler su-spoiler-style-default 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>References:<\/div><div   id="8n9s8rpp6h"    class=\"su-spoiler-content su-u-clearfix su-u-trim\">\n<p><strong>Radiation Protection:<\/strong><\/p>\n<ul>\n<li style=\"list-style-type: none;\">\n<ul>\n<li style=\"list-style-type: none;\">\n<ol>\n<li>Knoll, Glenn F., Radiation Detection and Measurement 4th Edition, Wiley, 8\/2010. ISBN-13: 978-0470131480.<\/li>\n<li>Stabin, Michael G., Radiation Protection, and Dosimetry: An Introduction to Health Physics, Springer, 10\/2010. ISBN-13: 978-1441923912.<\/li>\n<li>Martin, James E., Physics for Radiation Protection 3rd Edition, Wiley-VCH, 4\/2013. ISBN-13: 978-3527411764.<\/li>\n<li>U.S.NRC, NUCLEAR REACTOR CONCEPTS<\/li>\n<li>U.S. Department of Energy, Instrumentation, and Control. DOE Fundamentals Handbook, Volume 2 of 2. June 1992.<\/li>\n<\/ol>\n<\/li>\n<\/ul>\n<\/li>\n<\/ul>\n<p><strong>Nuclear and Reactor Physics:<\/strong><\/p>\n<ul>\n<li style=\"list-style-type: none;\">\n<ul>\n<li style=\"list-style-type: none;\">\n<ol>\n<li>J. R. Lamarsh, Introduction to Nuclear Reactor Theory, 2nd ed., Addison-Wesley, Reading, MA (1983).<\/li>\n<li>J. R. Lamarsh, A. J. Baratta, Introduction to Nuclear Engineering, 3d ed., Prentice-Hall, 2001, ISBN: 0-201-82498-1.<\/li>\n<li>W. M. Stacey, Nuclear Reactor Physics, John Wiley &amp; Sons, 2001, ISBN: 0- 471-39127-1.<\/li>\n<li>Glasstone, Sesonske. Nuclear Reactor Engineering: Reactor Systems Engineering, Springer; 4th edition, 1994, ISBN: 978-0412985317<\/li>\n<li>W.S.C. Williams. Nuclear and Particle Physics. Clarendon Press; 1 edition, 1991, ISBN: 978-0198520467<\/li>\n<li>G.R.Keepin. Physics of Nuclear Kinetics. Addison-Wesley Pub. Co; 1st edition, 1965<\/li>\n<li>Robert Reed Burn, Introduction to Nuclear Reactor Operation, 1988.<\/li>\n<li>U.S. Department of Energy, Nuclear Physics and Reactor Theory. DOE Fundamentals Handbook, Volume 1 and 2. January 1993.<\/li>\n<li>Paul Reuss, Neutron Physics. EDP Sciences, 2008. ISBN: 978-2759800414.<\/li>\n<\/ol>\n<\/li>\n<\/ul>\n<\/li>\n<\/ul>\n<\/div><\/div><div   id="8n9s8rpp6h"    class=\"su-divider su-divider-style-dotted\" style=\"margin:15px 0;border-width:2px;border-color:#999999\"><\/div><\/div><\/div><div   id="8n9s8rpp6h"     class=\"lgc-column lgc-grid-parent lgc-grid-33 lgc-tablet-grid-33 lgc-mobile-grid-100 lgc-equal-heights \"><div   id="8n9s8rpp6h"     class=\"inside-grid-column\"><\/div><\/div><div   id="8n9s8rpp6h"     class=\"lgc-column lgc-grid-parent lgc-grid-33 lgc-tablet-grid-33 lgc-mobile-grid-100 lgc-equal-heights \"><div   id="8n9s8rpp6h"     class=\"inside-grid-column\">\n<h2>See above:<\/h2>\n<p>Nuclear Reactor<a href=\"http:\/\/sitepourvtc.com\/nuclear-power-plant\/nuclear-reactor\/\" class=\"su-button su-button-style-flat\" style=\"color:#606060;background-color:#ffffff;border-color:#cccccc;border-radius:10px;-moz-border-radius:10px;-webkit-border-radius:10px\" target=\"_self\"><span style=\"color:#606060;padding:7px 20px;font-size:16px;line-height:24px;border-color:#ffffff;border-radius:10px;-moz-border-radius:10px;-webkit-border-radius:10px;text-shadow:0px 0px 0px #000000;-moz-text-shadow:0px 0px 0px #000000;-webkit-text-shadow:0px 0px 0px #000000\"><i class=\"sui sui-link\" style=\"font-size:16px;color:#5d5d5d\"><\/i> <\/span><\/a><\/p><\/div><\/div><div   id="8n9s8rpp6h"     class=\"lgc-column lgc-grid-parent lgc-grid-33 lgc-tablet-grid-33 lgc-mobile-grid-100 lgc-equal-heights \"><div   id="8n9s8rpp6h"     class=\"inside-grid-column\"><\/div><\/div>\n","protected":false},"excerpt":{"rendered":"","protected":false},"author":1,"featured_media":0,"parent":100,"menu_order":0,"comment_status":"closed","ping_status":"closed","template":"","meta":{"generate_page_header":""},"_links":{"self":[{"href":"https:\/\/sitepourvtc.com\/wp-json\/wp\/v2\/pages\/26704"}],"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=26704"}],"version-history":[{"count":3,"href":"https:\/\/sitepourvtc.com\/wp-json\/wp\/v2\/pages\/26704\/revisions"}],"predecessor-version":[{"id":38380,"href":"https:\/\/sitepourvtc.com\/wp-json\/wp\/v2\/pages\/26704\/revisions\/38380"}],"up":[{"embeddable":true,"href":"https:\/\/sitepourvtc.com\/wp-json\/wp\/v2\/pages\/100"}],"wp:attachment":[{"href":"https:\/\/sitepourvtc.com\/wp-json\/wp\/v2\/media?parent=26704"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}