{"id":22142,"date":"2020-07-24T10:55:39","date_gmt":"2020-07-24T10:55:39","guid":{"rendered":"https:\/\/www.radiation-dosimetry.org\/o-que-e-antineutrino-definicao\/"},"modified":"2020-07-24T10:58:58","modified_gmt":"2020-07-24T10:58:58","slug":"o-que-e-antineutrino-definicao","status":"publish","type":"post","link":"https:\/\/www.radiation-dosimetry.org\/pt-br\/o-que-e-antineutrino-definicao\/","title":{"rendered":"O que \u00e9 Antineutrino – Defini\u00e7\u00e3o"},"content":{"rendered":"
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Antineutrinos s\u00e3o as antipart\u00edculas dos neutrinos.\u00a0O antineutrino \u00e9 uma part\u00edcula subat\u00f4mica elementar com massa infinitesimal e sem carga el\u00e9trica.\u00a0Dosimetria de Radia\u00e7\u00e3o<\/span><\/div>\n<\/div>\n
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Antineutrinos<\/span><\/strong>\u00a0s\u00e3o as antipart\u00edculas dos\u00a0<\/span>neutrinos<\/span><\/a>\u00a0.\u00a0O antineutrino \u00e9 uma\u00a0<\/span>part\u00edcula subat\u00f4mica elementar<\/span><\/a>\u00a0com massa infinitesimal (menor que 0,3eV ..?) E sem carga el\u00e9trica.\u00a0Neutrinos e antineutrinos pertencem \u00e0 fam\u00edlia dos\u00a0<\/span>lept\u00f5es<\/span><\/strong>\u00a0, o que significa que eles n\u00e3o interagem por for\u00e7a nuclear forte.\u00a0Os neutrinos s\u00e3o\u00a0part\u00edculas subat\u00f4micas\u00a0gravitacionais e com\u00a0<\/span>fraca intera\u00e7\u00e3o<\/span><\/strong>\u00a0com \u00bd unidade de rota\u00e7\u00e3o.\u00a0Tamb\u00e9m os antineutrinos (como neutrinos) s\u00e3o part\u00edculas subat\u00f4micas muito penetrantes, capazes de passar pela Terra sem nenhuma intera\u00e7\u00e3o.\u00a0Atualmente (2015), n\u00e3o est\u00e1 resolvido se o neutrino e sua antipart\u00edcula n\u00e3o s\u00e3o part\u00edculas id\u00eanticas.<\/span>Os antineutrinos s\u00e3o produzidos no\u00a0<\/span>decaimento beta negativo<\/span><\/strong>\u00a0.\u00a0Em um\u00a0<\/span>reator nuclear<\/span><\/a>\u00a0ocorre especialmente o \u03b2\u00a0<\/span>–<\/span><\/sup>\u00a0decad\u00eancia, porque a caracter\u00edstica comum dos\u00a0<\/span>produtos de fiss\u00e3o<\/span><\/a>\u00a0\u00e9 um excesso de n\u00eautrons (veja\u00a0<\/span>Estabilidade Nuclear<\/span><\/a>\u00a0).\u00a0Um fragmento de fiss\u00e3o inst\u00e1vel com excesso de\u00a0<\/span>n\u00eautrons<\/span><\/a>\u00a0sofre \u03b2\u00a0<\/span>–<\/span><\/sup>\u00a0decaimento, onde o n\u00eautron \u00e9 convertido em pr\u00f3ton, el\u00e9tron e\u00a0<\/span>antineutrino<\/span><\/strong>\u00a0.\u00a0Portanto, cada reator nuclear \u00e9 uma fonte muito poderosa de antineutrinos e pesquisadores de todo o mundo investigam as possibilidades de uso de antineutrinos para o monitoramento de reatores.<\/span><\/p>\n

Por outro lado, a fonte mais poderosa de\u00a0<\/span>neutrinos<\/span><\/strong>\u00a0no sistema solar \u00e9 sem d\u00favida o pr\u00f3prio Sol.\u00a0Bilh\u00f5es de\u00a0<\/span>neutrinos solares<\/span><\/strong>\u00a0por segundo passam (principalmente sem intera\u00e7\u00e3o) por cada cent\u00edmetro quadrado (~ 6 x 10\u00a0<\/span>10<\/span><\/sup>\u00a0cm\u00a0<\/span>-2<\/span><\/sup>\u00a0s\u00a0<\/span>-1<\/span><\/sup>\u00a0) na superf\u00edcie da Terra.\u00a0No Sol, os neutrinos s\u00e3o produzidos ap\u00f3s a rea\u00e7\u00e3o de fus\u00e3o de dois pr\u00f3tons durante\u00a0<\/span>o decaimento beta positivo<\/span><\/strong>\u00a0do n\u00facleo de h\u00e9lio-2.<\/span><\/p>\n

\"_<\/p>\n

Detec\u00e7\u00e3o de antineutrinos<\/span><\/h2>\n

Como os neutrinos\u00a0<\/span>n\u00e3o ionizam a<\/span><\/strong>\u00a0\u00a0mat\u00e9ria, eles n\u00e3o podem ser detectados diretamente.\u00a0A detec\u00e7\u00e3o de antineutrinos\u00a0<\/span>(Pr\u00eamio Nobel de 1995 por Frederick Reines e Clyde Cowan)<\/span><\/strong>\u00a0\u00e9 baseada na rea\u00e7\u00e3o:<\/span><\/p>\n

\"\"<\/p>\n

Essa intera\u00e7\u00e3o \u00e9 sim\u00e9trica ao decaimento beta do\u00a0<\/span>n\u00eautron livre<\/span><\/a>\u00a0; portanto, \u00e0s vezes \u00e9 chamada de\u00a0<\/span>decaimento beta inverso<\/span><\/strong>\u00a0.\u00a0Todos os m\u00e9todos de detec\u00e7\u00e3o exigem que os neutrinos transportem um\u00a0<\/span>limiar<\/span><\/strong>\u00a0m\u00ednimo de\u00a0energia de 1,8 MeV<\/strong>\u00a0.\u00a0Somente antineutrinos com energia acima do limiar de 1,8 MeV podem causar intera\u00e7\u00f5es com os pr\u00f3tons na \u00e1gua, produzindo\u00a0<\/span>p\u00f3sitrons<\/span><\/a>\u00a0e\u00a0<\/span>n\u00eautrons<\/span><\/a>\u00a0.<\/span><\/p>\n

Reator nuclear como fonte de antineutrinos<\/span><\/h2>\n

Os reatores nucleares<\/span><\/a>\u00a0s\u00e3o a principal fonte de antineutrinos gerados pelo homem.\u00a0Isso se deve ao fato de que os antineutrinos s\u00e3o produzidos em uma\u00a0deteriora\u00e7\u00e3o\u00a0<\/span>beta<\/span><\/a>\u00a0negativa\u00a0.\u00a0Num reactor nuclear ocorre especialmente o \u03b2\u00a0<\/span>–<\/span><\/sup>\u00a0decaimento, porque a caracter\u00edstica comum dos\u00a0<\/span>fragmentos de fiss\u00e3o<\/span><\/a>\u00a0\u00e9 um excesso de\u00a0<\/span>neutr\u00f5es<\/span><\/a>\u00a0(ver\u00a0<\/span>Estabilidade Nuclear<\/span><\/a>\u00a0).\u00a0Um fragmento de fiss\u00e3o inst\u00e1vel com excesso de n\u00eautrons sofre \u03b2\u00a0<\/span>–<\/span><\/sup>\u00a0decaimento, onde o n\u00eautron \u00e9 convertido em pr\u00f3ton, el\u00e9tron e\u00a0<\/span>antineutrino<\/span><\/strong>\u00a0.\u00a0A exist\u00eancia de emiss\u00e3o de antineutrinos e sua\u00a0<\/span>se\u00e7\u00e3o transversal muito baixa<\/span><\/strong>\u00a0para qualquer intera\u00e7\u00e3o leva a um fen\u00f4meno muito interessante.\u00a0Aproximadamente<\/span>cerca de 5%<\/span><\/strong>\u00a0(ou cerca de 12 MeV de 207 MeV) da energia liberada por uma\u00a0<\/span>fiss\u00e3o<\/span><\/a>\u00a0\u00e9\u00a0<\/span>irradiada para longe<\/span><\/strong>\u00a0do reator na forma de antineutrinos.\u00a0Para um reator nuclear t\u00edpico com uma pot\u00eancia t\u00e9rmica de 3000 MW\u00a0<\/span>th<\/span><\/sub>\u00a0(~ 1000MW\u00a0<\/span>e<\/span><\/sub>\u00a0de energia el\u00e9trica), a pot\u00eancia total produzida \u00e9 de fato maior, aproximadamente 3150 MW, dos quais 150 MW s\u00e3o irradiados para o espa\u00e7o como radia\u00e7\u00e3o antineutrina.\u00a0Essa quantidade de energia \u00e9 perdida para sempre, pois os antineutrinos s\u00e3o capazes de penetrar em todos os materiais do reator sem nenhuma intera\u00e7\u00e3o.\u00a0De fato, uma afirma\u00e7\u00e3o comum nos textos de f\u00edsica \u00e9 que o caminho livre m\u00e9dio de um neutrino \u00e9 aproximadamente um\u00a0<\/span>ano-luz de chumbo<\/span><\/strong>.\u00a0Al\u00e9m disso, um neutrino de energia moderada pode penetrar facilmente mil anos-luz de chumbo (de acordo com\u00a0<\/span>JB Griffiths<\/span><\/em>\u00a0).<\/span><\/p>\n

Observe que bilh\u00f5es de neutrinos solares por segundo\u00a0<\/span>passam<\/span><\/strong>\u00a0(principalmente sem intera\u00e7\u00e3o) por cada cent\u00edmetro quadrado (~ 6 \u00d7 10\u00a0<\/span>10<\/span><\/sup>\u00a0) na superf\u00edcie da Terra e a radia\u00e7\u00e3o antineutrina n\u00e3o \u00e9 de modo algum perigosa.<\/span><\/p>\n

Exemplo – Quantidade de antineutrinos produzidos:<\/span><\/h2>\n

N\u00facleos est\u00e1veis<\/span><\/strong>\u00a0com o n\u00famero de massa mais prov\u00e1vel A da\u00a0fiss\u00e3o\u00a0<\/span>U-235<\/span><\/strong>\u00a0s\u00e3o<\/span>\"_\u00a0e\u00a0<\/span>\"_.\u00a0Esses n\u00facleos possuem juntos\u00a0<\/span>98 pr\u00f3tons<\/span><\/strong>\u00a0e\u00a0<\/span>136 n\u00eautrons<\/span><\/strong>\u00a0, enquanto\u00a0<\/span>os fragmentos de fiss\u00e3o<\/span><\/strong>\u00a0(\u00a0<\/span>n\u00facleos pais<\/span><\/strong>\u00a0) possuem juntos\u00a0<\/span>92 pr\u00f3tons<\/span><\/strong>\u00a0e\u00a0<\/span>142 n\u00eautrons<\/span><\/strong>\u00a0.\u00a0Isto significa que ap\u00f3s cada fiss\u00e3o U-235, os fragmentos de fiss\u00e3o devem sofrer,\u00a0<\/span>em m\u00e9dia, 6 decaimentos beta negativos<\/span><\/strong>\u00a0(\u00a0<\/span>6 n\u00eautrons devem decair para 6 pr\u00f3tons<\/span><\/strong>\u00a0) e, portanto,\u00a0<\/span>6 antineutrinos devem ser produzidos por cada fiss\u00e3o<\/span><\/strong>\u00a0.\u00a0Portanto, o reator nuclear t\u00edpico produz aproximadamente\u00a0<\/span>6 x 10\u00a0<\/span>20<\/span><\/sup>\u00a0antineutrinos por segundo<\/span><\/strong>\u00a0(~ 200 MeV \/ fiss\u00e3o; ~ 6 antineutrinos \/ fiss\u00e3o; 3000 MW\u00a0<\/span>th<\/span><\/sub>\u00a0; 9.375 x 10\u00a0<\/span>19<\/span><\/sup>\u00a0fiss\u00f5es \/ s).<\/span><\/p>\n

Refer\u00eancia: Griffiths, David, Introdu\u00e7\u00e3o \u00e0s Part\u00edculas Elementares, Wiley, 1987.<\/span><\/strong><\/p>\n<\/div>\n<\/div>\n

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\"decaimento<\/a>
Decaimento beta do n\u00facleo C-14.<\/span><\/figcaption><\/figure>\n
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\"Evento<\/a>
Fonte: wikipedia.org<\/span><\/figcaption><\/figure>\n
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\"Detector<\/a>
O interior de um detector de antineutrino cil\u00edndrico antes de ser preenchido com um cintilador l\u00edquido claro, que revela intera\u00e7\u00f5es antineutrino pelos muito fracos lampejos de luz que emitem.\u00a0Tubos fotomultiplicadores sens\u00edveis revestem as paredes do detector, prontos para amplificar e registrar os flashes indicadores.<\/span>
\nFoto: Roy Kaltschmidt, LBNL<\/span>
\nFonte: Experi\u00eancia de neutrinos do reator Daya Bay<\/span><\/figcaption><\/figure>\n
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\"detec\u00e7\u00e3o<\/a>
Fonte: Slides – Dr. Blucher, Instituto Enrico Fermi<\/span><\/figcaption><\/figure>\n
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\"Energia<\/a>
Energia da fiss\u00e3o de ur\u00e2nio<\/span><\/figcaption><\/figure>\n
<\/div>\n
\"Rendimento<\/a>
Rendimento do fragmento de fiss\u00e3o para diferentes n\u00facleos.\u00a0As massas de fragmentos mais prov\u00e1veis \u200b\u200bs\u00e3o em torno das massas 95 (Krypton) e 137 (B\u00e1rio).<\/span><\/figcaption><\/figure>\n<\/div>\n<\/div>\n
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……………………………………………………………………………………………………………………………….<\/p>\n

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":"

Antineutrinos s\u00e3o as antipart\u00edculas dos neutrinos.\u00a0O antineutrino \u00e9 uma part\u00edcula subat\u00f4mica elementar com massa infinitesimal e sem carga el\u00e9trica.\u00a0Dosimetria de Radia\u00e7\u00e3o Antineutrinos\u00a0s\u00e3o as antipart\u00edculas dos\u00a0neutrinos\u00a0.\u00a0O antineutrino \u00e9 uma\u00a0part\u00edcula subat\u00f4mica elementar\u00a0com massa infinitesimal (menor que 0,3eV ..?) E sem carga el\u00e9trica.\u00a0Neutrinos e antineutrinos pertencem \u00e0 fam\u00edlia dos\u00a0lept\u00f5es\u00a0, o que significa que eles n\u00e3o interagem por for\u00e7a … 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":"\nO que \u00e9 Antineutrino - Defini\u00e7\u00e3o<\/title>\n<meta name=\"description\" content=\"Antineutrinos s\u00e3o as antipart\u00edculas dos neutrinos. 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