Moderation, Neutron Economy, and Reactor Safety

Vocabulary flashcards covering key concepts related to moderation, neutron economy, and safety parameters in nuclear reactors.

Moderator

A material used to slow down fast neutrons in a nuclear reactor, increasing the likelihood of fission.

Neutron Economy

A measure of how efficiently a reactor uses neutrons to sustain chain reactions and breed new fuel.

Moderation

The process of slowing down neutrons to thermal energies, increasing their probability of causing fission.

Fissile Material

Materials that can sustain a fission chain reaction, such as U-235.

Light Water

Water used as a moderator in reactors, which absorbs neutrons, potentially lowering neutron economy.

Heavy Water

A type of water that has a superior moderator property, effectively slowing neutrons while absorbing few.

Graphite Moderator

A moderator that has low neutron absorption and can slow neutrons but requires careful design.

Dancoff Factor

A correction factor accounting for neutron escape and absorption due to shadowing effects of adjacent fuel pins.

Over-Moderation

A condition where excessive thermal neutrons lead to increased absorption in non-fuel materials, reducing reactivity.

Boron Coefficient

The change in reactivity per unit change in boron concentration, typically negative.

Control Rods

Devices used to absorb neutrons and control the fission rate in a nuclear reactor.

Burnup

A measure of how much energy is extracted from nuclear fuel, usually in gigawatt-days per ton.

Fission Products

Isotopes produced during fission that can absorb neutrons and poison the reactor core.

Doppler Effect

A phenomenon where an increase in fuel temperature leads to increased neutron absorption by U-238.

Power Peaking

A condition during fuel depletion where localized reactivity increases, risking overheating.

Neutron Spectrum

The distribution of neutron energies in a reactor, influencing reaction probabilities.

Chemical Shim Control

Using a soluble material like boron in the coolant for uniform reactivity control across the core.

Resonance Escape Probability

The likelihood that a neutron slows down without being absorbed in resonance, crucial for sustaining reactions.

Spectrum Hardening

A shift in neutron population towards higher energies, affecting fission efficiency.

Delayed Neutrons

Neutrons emitted seconds after fission, allowing time for reactor control systems to react.

Neutron Leakage

The loss of neutrons from the reactor core, which can affect reactivity and efficiency.

Neutron Flux Spectrum

A plot showing the number of neutrons at each energy level within a reactor.

Criticality

The condition of a nuclear reactor where the fission chain reaction is self-sustaining.

Transmutation of Waste

The process of converting nuclear waste into less harmful materials through fission.

Moderator Temperature Coefficient (MTC)

The change in reactivity due to changes in the moderator’s temperature.

Fuel Cladding

The material that encases nuclear fuel and helps to contain fission products.

Emergency Shutdown (SCRAM)

A rapid termination of fission reactions typically by inserting control rods.

Neutron Absorption Cross-section

A measure of the probability of a neutron being absorbed by a material.