{"id":11465,"date":"2016-01-13T12:08:59","date_gmt":"2016-01-13T12:08:59","guid":{"rendered":"http:\/\/sitepourvtc.com\/?page_id=11465"},"modified":"2022-10-13T06:35:16","modified_gmt":"2022-10-13T06:35:16","slug":"interactions-neutrons-matter","status":"publish","type":"page","link":"https:\/\/sitepourvtc.com\/nuclear-power\/reactor-physics\/atomic-nuclear-physics\/fundamental-particles\/neutron\/interactions-neutrons-matter\/","title":{"rendered":"Interactions of Neutrons with Matter"},"content":{"rendered":"
Neutrons have zero electrical charges and cannot directly cause ionization. Neutrons ionize matter only indirectly<\/strong>. For example, when neutrons strike the hydrogen nuclei, proton radiation (fast protons) results. This reaction is known as scattering. Neutrons can also be absorbed. Most absorption reactions result in the loss of a neutron coupled with the production of one or more gamma rays<\/a>\u00a0since the resulting nucleus is usually unstable. <\/div><\/div>\n

Neutrons<\/strong> are neutral particles. Therefore they travel in straight lines<\/strong>, deviating from their path only when they collide with a nucleus to be scattered into a new direction or absorbed. Neither the electrons surrounding (atomic electron cloud) a nucleus nor the electric field caused by a positively charged nucleus affect a neutron\u2019s flight. In short, neutrons collide with nuclei<\/strong>, not with atoms.\u00a0A very descriptive feature of the transmission of neutrons through bulk matter is the\u00a0mean free path length (\u03bb – lambda<\/b><\/strong>), which is the mean distance a neutron travels between interactions. It can be calculated from the following equation:<\/p>\n

\u03bb=1\/\u03a3<\/b><\/strong><\/p>\n

Neutrons may interact with nuclei in one of the following ways:<\/strong><\/p>\n

\"Neutron<\/a><\/p>\n

\n

Types of Interactions of Neutrons with Matter<\/h2>\n
<\/span>Elastic Scattering Reaction<\/div>
Generally, a neutron scattering<\/strong> reaction occurs when a target nucleus emits a single neutron<\/a> after a neutron-nucleus interaction. No energy is transferred into nuclear excitation in an elastic scattering<\/a> reaction<\/strong> between a neutron and a target nucleus.<\/div><\/div>
<\/span>Inelastic Scattering Reaction<\/div>
In an inelastic scattering<\/a> reaction<\/strong> between a neutron and a target nucleus, some energy of the incident neutron is absorbed into the recoiling nucleus, and the nucleus remains in the excited state<\/strong>. Thus while momentum is conserved<\/strong> in an inelastic collision, the kinetic energy of the \u201csystem\u201d is not conserved<\/strong>.<\/div><\/div>
<\/span>Neutron Absorption<\/div>
The neutron absorption reaction<\/strong><\/a> is the most important type of reactions that take place in a nuclear reactor<\/a>. The absorption reactions are reactions where the neutron is completely absorbed, and the compound nucleus is formed<\/a>. This is a very important feature because the decay mode<\/b>\u00a0of such a compound nucleus does not depend on how the compound nucleus was formed.<\/strong> Therefore a variety of emissions or decays may follow. The most important absorption reactions are divided by the exit channel into two following reactions:<\/p>\n