Moderator
| Also Known As | Neutron moderator, nuclear moderator, thermal moderator |
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What is Moderator?
A neutron moderator is a material used in nuclear reactors to slow down (moderate) fast neutrons produced by fission to thermal energies, making them more effective at causing further fission in U-235. Good moderators have a low atomic mass (to efficiently transfer kinetic energy to neutrons) and low neutron absorption cross-section. Common moderators include ordinary water (H₂O), heavy water (D₂O), graphite, and beryllium.
Properties & Characteristics
Uses & Applications
Safety Information
Always consult the SDS/MSDS before handling any chemical. This information is for educational purposes only.
Key Facts
Frequently Asked Questions
A neutron moderator is a material used in nuclear reactors to slow down (moderate) fast neutrons produced by fission to thermal energies, making them more effective at causing further fission in U-235. Good moderators have a low atomic mass (to efficiently transfer kinetic energy to neutrons) and low neutron absorption cross-section. Common moderators include ordinary water (H₂O), heavy water (D₂O), graphite, and beryllium.
Light water reactors (LWR) — most common nuclear power plant type. CANDU reactors (heavy water moderator). Research reactors. Producing medical and industrial radioisotopes. Graphite-moderated reactors (historical — Windscale, Chernobyl).
Moderator materials have specific hazards. Graphite dust: fire risk. Beryllium: highly toxic by inhalation (chronic beryllium disease, carcinogen). Heavy water: see D₂O safety. Reactor moderator systems: radiation exposure, contaminated coolant. Graphite fires (Windscale 1957, Chernobyl 1986) demons…