Neutronøkonomi

Neutronøkonomi, often translated as neutron economy, is a concept primarily used in nuclear reactor physics. It refers to the efficient utilization of neutrons produced by nuclear fission within a reactor core. A high neutron economy means that a larger proportion of the neutrons produced are available to cause further fissions, sustain the chain reaction, and potentially be captured by fertile materials to produce new fissile fuel. Conversely, poor neutron economy implies that many neutrons are lost through unproductive processes.

Several factors influence neutron economy. Neutron leakage from the reactor core is a significant loss mechanism. The absorption of neutrons by non-fissile materials, such as structural components, control rods, or fission products, also reduces neutron availability. The probability of a neutron causing fission upon interacting with a fissile nucleus is another crucial aspect. Materials with a high fission cross-section for thermal neutrons, like Uranium-235, contribute positively to neutron economy.

Reactor design aims to optimize neutron economy. This can involve using neutron reflectors to bounce escaping neutrons back into the core, selecting materials with low neutron absorption cross-sections for construction, and carefully managing the concentration of fissile and fertile materials. The moderator material also plays a role; moderators slow down fast neutrons from fission to thermal energies, where they are more likely to cause fission in many common fissile isotopes. Efficient moderation without excessive absorption is key. Maintaining a good neutron economy is essential for the sustained operation and fuel breeding capabilities of nuclear reactors.