Phrase guide

fast reactor

noun · 2 senses · updated from the 2026-07-25 local source snapshot

Definitions and examples are grouped by meaning. Pronunciation, history, word forms, translations, descendants, synonyms, antonyms, derived terms, and related words appear whenever the source provides them.

Sound

Pronunciation

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1

noun

Meaning 1

A nuclear reactor with no moderator, using fast neutrons directly in a controlled fission chain reaction without slowing them down, allowing for a much more compact reactor which uses fissile material much more efficiently and generates larger quantities of high-energy neutrons which can be used for breeding more fissile material or producing other useful radioactive nuclides, but requiring the use of highly-enriched uranium (at least 20% uranium-235) or other fuel containing a similarly high concentration of fissile material.

Definition source: English Wiktionary via Wiktextract

Qualifier: nuclear physics

Topics: engineering, natural-sciences, physical-sciences

No example sentence was provided for this meaning.

Meaning relationships

Synonyms: none provided

Antonyms: none provided

2

noun

Meaning 2

nuclear reactor in which nuclear fissions are caused by fast neutrons because little or no moderator is used

Definition source: Princeton WordNet 3.0

No example sentence was provided for this meaning.

Meaning relationships

Synonyms: none provided

Antonyms: thermal reactor

Broader terms: nuclear reactor, reactor

History

Etymology

Clipping of fast-neutron reactor.