Thermal reactor
In a nuclear reactor , a chain reaction is sustained by neutrons , which are generated during nuclear fission and which themselves trigger new nuclear fission. The cross-section for nuclear fission depends on the speed of the neutron. In a thermal reactor , decelerated thermal neutrons with a kinetic energy of about 0.025 eV trigger the fission. (So the name of the reactor type has nothing to do with the fact that it delivers thermal power, heat output.)
A moderator is necessary to slow down the fast neutrons released during fission to thermal energy . Since the fission cross-section of the fissile nuclides for thermal neutrons is large, the chain reaction can be maintained even with a low number density of these nuclides. Thermal reactors can therefore be operated with slightly enriched uranium or, with a suitable moderator, even with natural uranium . Depending on the reactor type, normal (light) water, heavy water or graphite are used as moderators .
In contrast to the thermal reactor, however, in a “fast reactor” fast neutrons with an average kinetic energy of around 80 keV trigger the fission. The fast reactor has no moderator and therefore has a small reactor volume. The low probability of absorption of the fast neutrons and the relatively high yield of new neutrons in the fission reaction make the fast reactor suitable for breeding new fissile material ( breeding reactor ).
In addition to thermal nuclear reactors, so-called thermal reactors for post-oxidation of the exhaust gas existed in the motor vehicle sector before the introduction of catalyst technology .
Individual evidence
- ↑ Aleksey D. Galanin: Theory of thermal nuclear reactors . Teubner, Leipzig 1959, p. XII 382 .