Search results
Results From The WOW.Com Content Network
An activation product is a material that has been made radioactive by the process of neutron activation.. Fission products and actinides produced by neutron absorption of nuclear fuel itself are normally referred to by those specific names, and activation product reserved for products of neutron capture by other materials, such as structural components of the nuclear reactor or nuclear bomb ...
Neutron activation is the process in which neutron radiation induces radioactivity in materials, and occurs when atomic nuclei capture free neutrons, becoming heavier and entering excited states. The excited nucleus decays immediately by emitting gamma rays , or particles such as beta particles , alpha particles , fission products , and ...
Free neutrons decay by emission of an electron and an electron antineutrino to become a proton, a process known as beta decay: [2] n 0 → p + + e − + ν e. Although the p + and e − produced by neutron decay are detectable, the decay rate is too low to serve as the basis for a practical detector system.
The number of neutrons produced per fission is multiplicatively modified by the dominant eigenvalue. The resulting value of this eigenvalue reflects the time dependence of the neutron density in a multiplying medium. k eff < 1, subcritical: the neutron density is decreasing as time passes; k eff = 1, critical: the neutron density remains ...
Like power reactors, the core needs cooling, typically natural or forced convection with water, and a moderator is required to slow the neutron velocities and enhance fission. As neutron production is their main function, most research reactors benefit from reflectors to reduce neutron loss from the core.
Some isotopes undergo spontaneous fission (SF) with emission of neutrons.The most common spontaneous fission source is the isotope californium-252. 252 Cf and all other SF neutron sources are made by irradiating uranium or a transuranic element in a nuclear reactor, where neutrons are absorbed in the starting material and its subsequent reaction products, transmuting the starting material into ...
Neutron capture is a nuclear reaction in which an atomic nucleus and one or more neutrons collide and merge to form a heavier nucleus. [1] Since neutrons have no electric charge, they can enter a nucleus more easily than positively charged protons , which are repelled electrostatically .
The unbound neutron has a half-life of 10 minutes and 11 seconds. The release of neutrons from the nucleus requires exceeding the binding energy of the neutron, which is typically 7-9 MeV for most isotopes. Neutron sources generate free neutrons by a variety of nuclear reactions, including nuclear fission and nuclear fusion. Whatever the source ...