Thermal-neutron reactor

In a nuclear reactor, a chain reaction is maintained by neutrons resulting from the fission trigger itself again and new fissions. The effective cross section for the core depends on the cleavage rate of the neutron. In a thermal reactor solve braked, thermal neutrons with a kinetic energy of about 0.025 eV from the divisions. ( The designation of the type of reactor has nothing to do with the fact that it provides thermal power, thermal power. )

For braking the released in the fission fast neutrons to thermal energy a moderator is required. Since the fission cross -section of the fissile nuclides is great for thermal neutrons, the chain reaction can be maintained even at low core number density of these nuclides. Thermal reactors can therefore be operated even with slightly enriched uranium or natural uranium suitable moderator. As moderators normal (light ) water, heavy water or graphite are used depending on the type of reactor.

In contrast to the thermal reactor, however, fast neutrons dissolve in a "fast reactor " having an average kinetic energy of approximately 80 keV, the cleavage from. 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 of new fissile material ( breeder reactor ).

• Type of reactor