Criticaliteitsveiligheid

Criticaliteitsveiligheid, often translated as criticality safety, is a fundamental principle in nuclear reactor design and operation. Its primary goal is to prevent the unintended accumulation of fissile material in a configuration that could lead to a nuclear chain reaction. This unwanted reaction is known as criticality.

The concept of criticality safety is rooted in understanding neutron interactions. Fissile materials, like uranium-235 or plutonium-239, can undergo nuclear fission when they absorb a neutron. This fission process releases energy and more neutrons, which can then cause further fissions. If enough fissile material is present and arranged in a specific geometry, a self-sustaining chain reaction can occur, releasing a large amount of energy. This is the principle behind nuclear weapons, but in a controlled environment like a reactor, it is highly undesirable and dangerous outside of the intended core operation.

Criticality safety measures are implemented at every stage of handling fissile materials, from their fabrication and transport to their storage and disposal. These measures include controlling the amount of fissile material, its geometry, and the presence of neutron moderators or reflectors. For example, processing facilities might use neutron-absorbing materials in tanks or work surfaces to prevent the concentration of fissile solutions. Storage containers are designed to keep fissile units separated and at a safe distance from each other. The principles of criticality safety are rigorously applied to ensure that nuclear facilities operate without the risk of accidental criticality events.