Subkriitiline

Subkriitiline (also known as "subcritical" in English) refers to a state in nuclear physics where a nuclear reaction, such as fission, is occurring but is not self-sustaining. In this state, the reaction relies on an external source of neutrons to maintain the chain reaction, as the number of neutrons produced does not exceed the number required to sustain the reaction on its own. This contrasts with a critical or supercritical state, where the reaction can propagate without external intervention.

Subkriitiline systems are commonly used in research and medical applications, such as neutron activation analysis and the production of medical isotopes. These systems are designed to operate below the threshold where a self-sustaining chain reaction could occur, ensuring safety by preventing uncontrolled reactions. The neutron flux in subkriitiline reactors is typically lower than in critical reactors, which reduces radiation exposure and minimizes the risk of accidents.

One notable example of a subkriitiline system is a neutron source reactor, which generates neutrons for scientific experiments or industrial applications. These reactors often use materials like uranium-238 or thorium, which can be converted into fissile isotopes when exposed to neutrons, but do not sustain a chain reaction on their own. The design of subkriitiline systems prioritizes safety by incorporating neutron absorbers, such as boron or cadmium, to control the reaction and prevent it from becoming critical.

In contrast to critical reactors, which are used for power generation, subkriitiline systems do not produce significant amounts of energy. Their primary purpose is to provide a controlled environment for neutron-related research or applications. The use of subkriitiline systems helps mitigate risks associated with nuclear reactions while enabling valuable scientific and medical advancements.