Regulator (nuclear)
See also: Moderating
Placé au heart of a Nuclear reactor, the moderating is the element which slows down the speed of the Neutron S, thus allowing a Chain nuclear reaction effective. The element selected to design the regulator of a nuclear reactor is generally of the Hydrogène, the Deutérium or the Carbone.
The principle of deceleration of the neutrons is theorized by the concept of Thermalization of the neutrons.
Principle
The deceleration of the neutrons is obtained by a shock between this neutron and the cores of atoms of the regulator. At the time of this shock, part of the energy of the neutron is transmitted to the core, which causes the deceleration. A good regulator must have a cross Section high for the elastic shock, but weakest possible for the neutron capture. Moreover, the deceleration will be all the more effective as the core has a mass close to that of the neutron.
Materials used
- Hydrogen: in the ordinary water shape (" light Water "), in a light Water reactor, for example the REFERENCE MARK. It is the most effective regulator, the mass of the core being very close to that of the neutron. However, the neutron capture is rather important, which leads to a great loss of neutrons. From where need for the uranium enriched to function.
- Deuterium: in the form of heavy Water, in a Heavy-water reactor, for example CANDU. Regulator less effective than hydrogen, but the neutron capture being weaker, the moderated engines with heavy water can use natural uranium. However heavy water is an expensive compound.
- Carbon: in the form of Graphite or pyrolytic Carbon, used for example on RBMK and the Engine with bed of balls. Some of these engines can use natural uranium.
- Beryllium: in metal form. Beryllium is expensive and toxic, this is why its use is limited.
External bonds
- AVN : The regulator: a brake for the neutrons
- ECA: The regulator
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