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The decrease in the critical size of core required is known as the reflector savings. Neutron reflectors reduce neutron leakage, i.e., to reduce the neutron fluence on a reactor pressure vessel. Neutron reflectors reduce a coolant flow bypass of a core. Neutron reflectors serve as a thermal and radiation shield of a reactor core.
A neutron supermirror is a highly polished, layered material used to reflect neutron beams. Supermirrors are a special case of multi-layer neutron reflectors with varying layer thicknesses. [1] The first neutron supermirror concept was proposed by Ferenc Mezei, [2] inspired by earlier work with X-rays.
Moderation is the process of the reduction of the initial high speed (high kinetic energy) of the free neutron. Since energy is conserved, this reduction of the neutron speed takes place by transfer of energy to a material called a moderator. The probability of scattering of a neutron from a nucleus is given by the scattering cross section. The ...
In all of these cases, the use of a neutron reflector like beryllium can substantially drop this amount, however: with a 5 centimetres (2.0 in) reflector, the critical mass of 19.75%-enriched uranium drops to 403 kilograms (888 lb), and with a 15 centimetres (5.9 in) reflector it drops to 144 kilograms (317 lb), for example.
Zirconium(II) hydride is used as a thermal neutron moderator in nuclear reactors and as a material for neutron reflectors in fast reactors. [5] Zirconium(II) hydride in the form of a powder is used in powder metallurgy as a hydrogenation catalyst, vacuum tube getter, foaming agent in the production of metal foams and as a reducing agent. [5]
Nuclear graphite is any grade of graphite, usually synthetic graphite, manufactured for use as a moderator or reflector within a nuclear reactor.Graphite is an important material for the construction of both historical and modern nuclear reactors because of its extreme purity and ability to withstand extremely high temperatures.
The reflection is usually described in terms of a momentum transfer vector, denoted , which describes the change in momentum of a neutron after reflecting from the material. Conventionally the z {\displaystyle z} direction is defined to be the direction normal to the surface, and for specular reflection, the scattering vector has only a z ...
A subcritical reactor —regardless of neutron spectrum— can also "breed" fissile nuclides from fertile material, allowing in principle the consumption of very low grade actinides (e.g. Spent MOX fuel whose plutonium-240 content is too high for use in current critical thermal reactors) without the need for highly enriched material as used in ...