Вопрос
Question 4: describe the interaction of neutrons in matter. Your description should include the following (i) the main categories of neutrons, (ii) the interaction cross section, (iii) the main interaction mechauisms contributing to the total cross section, and (iv) the implications for reactor design (10 Marks)
Решения
4.5
(273 Голоса)
Шамиль
мастер · Репетитор 5 лет
Ответ
(i) The main categories of neutrons are thermal neutrons, epithermal neutrons, and fast neutrons. Thermal neutrons are slow-moving neutrons with energies typically around 0.025 eV, which are most likely to cause fission in a nuclear reactor. Epithermal neutrons have energies between thermal and fast neutrons, while fast neutrons have energies greater than 10 keV.(ii) The interaction cross section is a measure of the probability of a neutron interacting with a particular type of nucleus or particle. It is usually expressed in units of barns (1 barn = 10^-24 cm^2). The interaction cross section varies depending on the type of interaction and the energy of the neutron.(iii) The main interaction mechanisms contributing to the total cross section are elastic scattering, inelastic scattering, and neutron absorption. Elastic scattering occurs when a neutron collides with a nucleus and is scattered without losing energy. Inelastic scattering occurs when a neutron collides with a nucleus and loses energy, which is transferred to the nucleus. Neutron absorption occurs when a neutron is captured by a nucleus, which can lead to fission or other reactions.(iv) The implications for reactor design are significant. The interaction cross section and interaction mechanisms determine the behavior of neutrons in the reactor, which in turn affects the efficiency and safety of the reactor. For example, a high interaction cross section for thermal neutrons is desirable for sustaining a chain reaction, while a low interaction cross section for fast neutrons is desirable for controlling the reaction. Additionally, the interaction mechanisms can lead to the production of radioactive isotopes, which must be managed and contained within the reactor.