{"id":21994,"date":"2020-07-23T10:00:04","date_gmt":"2020-07-23T10:00:04","guid":{"rendered":"https:\/\/www.radiation-dosimetry.org\/o-que-e-o-calculo-da-dose-absorvida-problema-definicao\/"},"modified":"2020-07-23T10:00:04","modified_gmt":"2020-07-23T10:00:04","slug":"o-que-e-o-calculo-da-dose-absorvida-problema-definicao","status":"publish","type":"post","link":"https:\/\/www.radiation-dosimetry.org\/pt-br\/o-que-e-o-calculo-da-dose-absorvida-problema-definicao\/","title":{"rendered":"O que \u00e9 o c\u00e1lculo da dose absorvida &#8211; Problema &#8211; Defini\u00e7\u00e3o"},"content":{"rendered":"<div class=\"su-quote su-quote-style-default\">\n<div class=\"su-quote-inner su-u-clearfix su-u-trim\">C\u00e1lculo da dose absorvida &#8211; Problema.\u00a0Calcule a taxa de dose prim\u00e1ria de f\u00f3tons, em cinza por hora (Gy.h-1), na superf\u00edcie externa de uma blindagem de chumbo com 5 cm de espessura.\u00a0Dosimetria de Radia\u00e7\u00e3o<\/div>\n<\/div>\n<div class=\"su-divider su-divider-style-dotted\"><\/div>\n<div class=\"lgc-column lgc-grid-parent lgc-grid-100 lgc-tablet-grid-100 lgc-mobile-grid-100 lgc-equal-heights lgc-first lgc-last\">\n<div class=\"inside-grid-column\">\n<p><strong>Dose absorvida<\/strong>\u00a0\u00e9 definida como a quantidade de energia depositada pela radia\u00e7\u00e3o ionizante em uma subst\u00e2ncia.\u00a0<strong>Dose absorvida<\/strong>\u00a0\u00e9 dado o s\u00edmbolo\u00a0<strong>D<\/strong>\u00a0.\u00a0A dose absorvida \u00e9 geralmente medida em uma unidade chamada\u00a0<strong>cinza<\/strong>\u00a0(Gy), que \u00e9 derivada do sistema SI.\u00a0\u00c0s vezes, a\u00a0unidade n\u00e3o-SI\u00a0<strong>rad<\/strong>\u00a0tamb\u00e9m \u00e9 usada, predominantemente nos EUA.<\/p>\n<p><a href=\"http:\/\/www.radiation-dosimetry.org\/wp-content\/uploads\/2019\/12\/absorbed-dose-definition.png\"><img loading=\"lazy\" class=\"aligncenter size-full wp-image-25307 lazy-loaded\" src=\"http:\/\/www.radiation-dosimetry.org\/wp-content\/uploads\/2019\/12\/absorbed-dose-definition.png\" alt=\"dose absorvida - defini\u00e7\u00e3o\" width=\"180\" height=\"72\" data-lazy-type=\"image\" data-src=\"http:\/\/www.radiation-dosimetry.org\/wp-content\/uploads\/2019\/12\/absorbed-dose-definition.png\" \/><\/a><\/p>\n<p><a href=\"https:\/\/www.radiation-dosimetry.org\/wp-content\/uploads\/2019\/12\/Absorbed_Dose_definition-min.png\"><img loading=\"lazy\" class=\"alignright size-medium wp-image-25314 lazy-loaded\" src=\"https:\/\/www.radiation-dosimetry.org\/wp-content\/uploads\/2019\/12\/Absorbed_Dose_definition-min-300x267.png\" alt=\"Dose absorvida\" width=\"300\" height=\"267\" data-lazy-type=\"image\" data-src=\"https:\/\/www.radiation-dosimetry.org\/wp-content\/uploads\/2019\/12\/Absorbed_Dose_definition-min-300x267.png\" \/><\/a><\/p>\n<h2>C\u00e1lculo da taxa de dose protegida<\/h2>\n<p>Suponha a\u00a0<strong>fonte isotr\u00f3pica pontual<\/strong>\u00a0que cont\u00e9m\u00a0<strong>1,0 Ci de\u00a0<sup>137<\/sup>\u00a0Cs<\/strong>\u00a0, que tem uma\u00a0<a href=\"https:\/\/www.nuclear-power.com\/nuclear-power\/reactor-physics\/atomic-nuclear-physics\/radioactive-decay\/radioactive-decay-law\/half-life\/\">meia-vida<\/a>\u00a0de\u00a0<strong>30,2 anos<\/strong>\u00a0.\u00a0Observe que a rela\u00e7\u00e3o entre a meia-vida e a quantidade de\u00a0<a href=\"https:\/\/www.nuclear-power.com\/nuclear-power\/reactor-physics\/atomic-nuclear-physics\/atom-properties-of-atoms\/radionuclide-radioisotope\/\">radionucl\u00eddeo<\/a>\u00a0necess\u00e1ria para gerar uma atividade de\u00a0<a href=\"https:\/\/www.nuclear-power.com\/nuclear-engineering\/radiation-protection\/units-of-radioactivity\/curie-unit-of-radioactivity\/\">um curie<\/a>\u00a0\u00e9 mostrada abaixo.\u00a0Essa quantidade de material pode ser calculada usando \u03bb, que \u00e9 a\u00a0<a href=\"https:\/\/www.nuclear-power.com\/nuclear-power\/reactor-physics\/atomic-nuclear-physics\/radioactive-decay\/radioactive-decay-law\/decay-constant\/\">constante<\/a>\u00a0de\u00a0<a href=\"https:\/\/www.nuclear-power.com\/nuclear-power\/reactor-physics\/atomic-nuclear-physics\/radioactive-decay\/radioactive-decay-law\/decay-constant\/\">decaimento<\/a>\u00a0de determinado nucl\u00eddeo:<\/p>\n<p><a href=\"http:\/\/www.radiation-dosimetry.org\/wp-content\/uploads\/2019\/12\/Curie-Unit-of-Activity.png\"><img loading=\"lazy\" class=\"aligncenter size-full wp-image-24886 lazy-loaded\" src=\"http:\/\/www.radiation-dosimetry.org\/wp-content\/uploads\/2019\/12\/Curie-Unit-of-Activity.png\" alt=\"Curie - Unidade de Atividade\" width=\"378\" height=\"61\" data-lazy-type=\"image\" data-src=\"http:\/\/www.radiation-dosimetry.org\/wp-content\/uploads\/2019\/12\/Curie-Unit-of-Activity.png\" \/><\/a><\/p>\n<p>Cerca de 94,6% decai por\u00a0<a href=\"https:\/\/www.nuclear-power.com\/nuclear-power\/reactor-physics\/atomic-nuclear-physics\/radioactive-decay\/beta-decay-beta-radioactivity\/\">emiss\u00e3o beta<\/a>\u00a0em um\u00a0<a href=\"https:\/\/www.nuclear-power.com\/nuclear-power\/reactor-physics\/atomic-nuclear-physics\/atom-properties-of-atoms\/nuclides\/isomers\/\">is\u00f4mero nuclear<\/a>\u00a0metaest\u00e1vel\u00a0de b\u00e1rio: b\u00e1rio-137m.\u00a0O pico principal de f\u00f3tons de Ba-137m \u00e9\u00a0<strong>662 keV<\/strong>\u00a0.\u00a0Para esse c\u00e1lculo, suponha que todos os decaimentos passem por esse canal.<\/p>\n<p><strong>Determine a taxa de dose prim\u00e1ria do f\u00f3ton<\/strong>\u00a0, em cinza por hora (Gy.h\u00a0<sup>-1<\/sup>\u00a0), na superf\u00edcie externa de uma blindagem de chumbo com 5 cm de espessura.\u00a0A taxa de dose prim\u00e1ria de f\u00f3tons negligencia todas as part\u00edculas secund\u00e1rias.\u00a0Suponha que a dist\u00e2ncia efetiva da fonte do ponto de dose seja\u00a0<strong>10 cm<\/strong>\u00a0.\u00a0Tamb\u00e9m devemos assumir que o ponto de dose \u00e9 um tecido mole, que pode ser razoavelmente simulado pela \u00e1gua e usamos o coeficiente de absor\u00e7\u00e3o de energia em massa da \u00e1gua.<\/p>\n<p>Veja tamb\u00e9m:\u00a0<a href=\"https:\/\/www.nuclear-power.com\/nuclear-power\/reactor-physics\/interaction-radiation-matter\/interaction-gamma-radiation-matter\/gamma-ray-attenuation\/\">Atenua\u00e7\u00e3o de raios gama<\/a><\/p>\n<p>Veja tamb\u00e9m:\u00a0<a href=\"https:\/\/www.nuclear-power.com\/nuclear-power\/reactor-physics\/atomic-nuclear-physics\/radiation\/shielding-of-ionizing-radiation\/shielding-gamma-radiation\/\">Blindagem de raios gama<\/a><\/p>\n<p><strong>Solu\u00e7\u00e3o:<\/strong><\/p>\n<p>A taxa de dose prim\u00e1ria de f\u00f3tons \u00e9\u00a0<a href=\"https:\/\/www.nuclear-power.com\/nuclear-power\/reactor-physics\/interaction-radiation-matter\/interaction-gamma-radiation-matter\/gamma-ray-attenuation\/\">atenuada exponencialmente<\/a>\u00a0, e a taxa de dose de f\u00f3tons prim\u00e1rios, levando em considera\u00e7\u00e3o o escudo, \u00e9 dada por:<\/p>\n<p><a href=\"http:\/\/www.radiation-dosimetry.org\/wp-content\/uploads\/2019\/12\/dose-rate-calculation.png\"><img loading=\"lazy\" class=\"aligncenter size-full wp-image-25304 lazy-loaded\" src=\"http:\/\/www.radiation-dosimetry.org\/wp-content\/uploads\/2019\/12\/dose-rate-calculation.png\" alt=\"c\u00e1lculo da taxa de dose\" width=\"671\" height=\"307\" data-lazy-type=\"image\" data-src=\"http:\/\/www.radiation-dosimetry.org\/wp-content\/uploads\/2019\/12\/dose-rate-calculation.png\" \/><\/a><\/p>\n<p>Como pode ser visto, n\u00e3o consideramos o ac\u00famulo de radia\u00e7\u00e3o secund\u00e1ria.\u00a0Se part\u00edculas secund\u00e1rias forem produzidas ou se a radia\u00e7\u00e3o prim\u00e1ria mudar sua energia ou dire\u00e7\u00e3o, a atenua\u00e7\u00e3o efetiva ser\u00e1 muito menor.\u00a0Essa suposi\u00e7\u00e3o geralmente subestima a taxa de dose verdadeira, especialmente para blindagens espessas e quando o ponto de dose est\u00e1 pr\u00f3ximo \u00e0 superf\u00edcie da blindagem, mas essa suposi\u00e7\u00e3o simplifica todos os c\u00e1lculos.\u00a0Nesse caso, a taxa real de dose (com o ac\u00famulo de radia\u00e7\u00e3o secund\u00e1ria) ser\u00e1 mais de duas vezes maior.<\/p>\n<p><span>Para calcular a\u00a0<\/span><strong><span>taxa de dose absorvida<\/span><\/strong><span>\u00a0, precisamos usar a f\u00f3rmula:<\/span><\/p>\n<ul>\n<li><span>k = 5,76 x 10\u00a0<\/span><sup><span>-7<\/span><\/sup><\/li>\n<li><span>S = 3,7 x 10\u00a0<\/span><sup><span>10<\/span><\/sup><span>\u00a0s\u00a0<\/span><sup><span>-1<\/span><\/sup><\/li>\n<li><span>E = 0,662 MeV<\/span><\/li>\n<li><span>\u03bc\u00a0<\/span><sub><span>t<\/span><\/sub><span>\u00a0\/ \u03c1 = 0,0326 cm\u00a0<\/span><sup><span>2<\/span><\/sup><span>\u00a0\/ g (os valores est\u00e3o dispon\u00edveis no NIST)<\/span><\/li>\n<li><span>\u03bc = 1,289 cm\u00a0<\/span><sup><span>-1<\/span><\/sup><span>\u00a0(os valores est\u00e3o dispon\u00edveis no NIST)<\/span><\/li>\n<li><span>D = 5 cm<\/span><\/li>\n<li><span>r = 10 cm<\/span><\/li>\n<\/ul>\n<p><strong><span>Resultado:<\/span><\/strong><\/p>\n<p><span>A taxa de dose absorvida resultante em cinza por hora \u00e9 ent\u00e3o:<\/span><\/p>\n<p><a href=\"http:\/\/www.radiation-dosimetry.org\/wp-content\/uploads\/2019\/12\/absorbed-dose-rate-gray-calculation-1.png\"><img loading=\"lazy\" class=\"aligncenter size-full wp-image-25319 lazy-loaded\" src=\"http:\/\/www.radiation-dosimetry.org\/wp-content\/uploads\/2019\/12\/absorbed-dose-rate-gray-calculation-1.png\" alt=\"taxa de dose absorvida - cinza - c\u00e1lculo\" width=\"551\" height=\"153\" data-lazy-type=\"image\" data-src=\"http:\/\/www.radiation-dosimetry.org\/wp-content\/uploads\/2019\/12\/absorbed-dose-rate-gray-calculation-1.png\" \/><\/a><\/p>\n<p><span>Se queremos dar conta do ac\u00famulo de radia\u00e7\u00e3o secund\u00e1ria, precisamos incluir o fator de ac\u00famulo.\u00a0A\u00a0<\/span><strong><span>f\u00f3rmula estendida<\/span><\/strong><span>\u00a0para a taxa de dose \u00e9 ent\u00e3o:<\/span><\/p>\n<p><a href=\"http:\/\/www.radiation-dosimetry.org\/wp-content\/uploads\/2019\/12\/absorbed-dose-rate-gray-calculation.png\"><img loading=\"lazy\" class=\"aligncenter size-full wp-image-25303 lazy-loaded\" src=\"http:\/\/www.radiation-dosimetry.org\/wp-content\/uploads\/2019\/12\/absorbed-dose-rate-gray-calculation.png\" alt=\"taxa de dose absorvida - cinza\" width=\"693\" height=\"158\" data-lazy-type=\"image\" data-src=\"http:\/\/www.radiation-dosimetry.org\/wp-content\/uploads\/2019\/12\/absorbed-dose-rate-gray-calculation.png\" \/><\/a><\/p>\n<p>&nbsp;<\/p>\n<\/div>\n<p>&#8230;&#8230;&#8230;&#8230;&#8230;&#8230;&#8230;&#8230;&#8230;&#8230;&#8230;&#8230;&#8230;&#8230;&#8230;&#8230;&#8230;&#8230;&#8230;&#8230;&#8230;&#8230;&#8230;&#8230;&#8230;&#8230;&#8230;&#8230;&#8230;&#8230;&#8230;&#8230;&#8230;&#8230;&#8230;&#8230;&#8230;&#8230;&#8230;&#8230;&#8230;&#8230;&#8230;&#8230;&#8230;&#8230;&#8230;&#8230;.<\/p>\n<p>Este artigo \u00e9 baseado na tradu\u00e7\u00e3o autom\u00e1tica do artigo original em ingl\u00eas. Para mais informa\u00e7\u00f5es, consulte o artigo em ingl\u00eas. Voc\u00ea pode nos ajudar. Se voc\u00ea deseja corrigir a tradu\u00e7\u00e3o, envie-a para: translations@nuclear-power.com ou preencha o formul\u00e1rio de tradu\u00e7\u00e3o on-line. Agradecemos sua ajuda, atualizaremos a tradu\u00e7\u00e3o o mais r\u00e1pido poss\u00edvel. Obrigado.<\/p>\n<\/div>\n","protected":false},"excerpt":{"rendered":"<p>C\u00e1lculo da dose absorvida &#8211; Problema.\u00a0Calcule a taxa de dose prim\u00e1ria de f\u00f3tons, em cinza por hora (Gy.h-1), na superf\u00edcie externa de uma blindagem de chumbo com 5 cm de espessura.\u00a0Dosimetria de Radia\u00e7\u00e3o Dose absorvida\u00a0\u00e9 definida como a quantidade de energia depositada pela radia\u00e7\u00e3o ionizante em uma subst\u00e2ncia.\u00a0Dose absorvida\u00a0\u00e9 dado o s\u00edmbolo\u00a0D\u00a0.\u00a0A dose absorvida \u00e9 &#8230; <a title=\"O que \u00e9 o c\u00e1lculo da dose absorvida &#8211; Problema &#8211; Defini\u00e7\u00e3o\" class=\"read-more\" href=\"https:\/\/www.radiation-dosimetry.org\/pt-br\/o-que-e-o-calculo-da-dose-absorvida-problema-definicao\/\" aria-label=\"More on O que \u00e9 o c\u00e1lculo da dose absorvida &#8211; Problema &#8211; Defini\u00e7\u00e3o\">Ler mais<\/a><\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":[],"categories":[51],"tags":[],"yoast_head":"<!-- This site is optimized with the Yoast SEO plugin v15.4 - https:\/\/yoast.com\/wordpress\/plugins\/seo\/ -->\n<title>O que \u00e9 o c\u00e1lculo da dose absorvida - Problema - Defini\u00e7\u00e3o<\/title>\n<meta name=\"description\" content=\"C\u00e1lculo da dose absorvida - Problema. 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