thermal neutrons: meaning, definition, pronunciation and examples
C2Technical/Scientific
Quick answer
What does “thermal neutrons” mean?
Neutrons that have been slowed down to have an average kinetic energy similar to the thermal energy of their surrounding medium, making them effective at inducing nuclear fission in certain isotopes like uranium-235.
Audio
Pronunciation
Definition
Meaning and Definition
Neutrons that have been slowed down to have an average kinetic energy similar to the thermal energy of their surrounding medium, making them effective at inducing nuclear fission in certain isotopes like uranium-235.
In a broader physics context, thermal neutrons are a specific energy state of free neutrons crucial for nuclear reactors, scientific instrumentation (e.g., neutron scattering), and medical treatments. Their energy (approximately 0.025 eV at room temperature) corresponds to thermal equilibrium with their environment.
Dialectal Variation
British vs American Usage
Differences
No significant lexical or conceptual differences. Spelling conventions follow the regional norm (e.g., 'behaviour' vs. 'behavior' in surrounding text).
Connotations
Identical technical connotations in both varieties.
Frequency
Extremely low frequency in general language, but identical technical frequency in relevant fields.
Grammar
How to Use “thermal neutrons” in a Sentence
The [moderator] thermalises neutrons to produce thermal neutrons.Thermal neutrons induce fission in [uranium-235].The [reactor] operates on a thermal neutron spectrum.Vocabulary
Collocations
Examples
Examples of “thermal neutrons” in a Sentence
verb
British English
- The heavy water thermalises the neutrons efficiently.
- The reactor is designed to thermalise the neutron spectrum.
American English
- The graphite thermalizes the neutrons efficiently.
- The reactor is designed to thermalize the neutron spectrum.
adjective
British English
- The thermal neutron cross-section is measured in barns.
- They conducted a thermal neutron diffraction analysis.
American English
- The thermal neutron cross-section is measured in barns.
- They conducted a thermal neutron diffraction analysis.
Usage
Meaning in Context
Business
Virtually never used.
Academic
Exclusively used in physics, nuclear engineering, and materials science research papers and textbooks.
Everyday
Never used in everyday conversation outside of specific technical discussion.
Technical
The primary domain. Used in reactor design, neutron diffraction experiments, radiation therapy planning, and nuclear safety protocols.
Vocabulary
Synonyms of “thermal neutrons”
Neutral
Weak
Vocabulary
Antonyms of “thermal neutrons”
Watch out
Common Mistakes When Using “thermal neutrons”
- Using 'thermal neutrons' to refer to neutrons that generate heat (they are not inherently 'hot').
- Confusing 'thermal' with 'thermalised'.
- Treating it as a flexible phrase (e.g., 'very thermal neutrons' is incorrect).
FAQ
Frequently Asked Questions
No. 'Thermal' refers to their energy being in equilibrium with the thermal motion of the surrounding medium (room temperature), not that they generate heat. Their energy is very low (~0.025 eV).
Their primary use is in inducing nuclear fission in fissile isotopes like Uranium-235 in nuclear reactors, as these isotopes have a much higher probability (cross-section) of capturing slow, thermal neutrons.
They are produced by slowing down (moderating) fast neutrons emitted from fission events. This is done by making them collide with light atoms in a moderator material like water, graphite, or heavy water.
The key difference is kinetic energy. Fast neutrons are born from fission with energies in the MeV (million electronvolt) range. Thermal neutrons have been slowed to energies around 0.025 eV, making them far more likely to be captured by certain atomic nuclei.
Neutrons that have been slowed down to have an average kinetic energy similar to the thermal energy of their surrounding medium, making them effective at inducing nuclear fission in certain isotopes like uranium-235.
Thermal neutrons is usually technical/scientific in register.
Thermal neutrons: in British English it is pronounced /ˌθɜː.məl ˈnjuː.trɒnz/, and in American English it is pronounced /ˌθɝː.məl ˈnuː.trɑːnz/. Tap the audio buttons above to hear it.
Learning
Memory Aids
Mnemonic
Think of a hot cup of tea (THERMal) and a slow-moving sugar cube (NEUTRON) you drop in—it dissolves/fissions effectively only when both are at the same 'temperature' or energy level.
Conceptual Metaphor
NEUTRON AS A PROJECTILE: A thermal neutron is a bullet slowed down to just the right speed to be caught by a specific target nucleus, triggering a split.
Practice
Quiz
What is the approximate kinetic energy of a thermal neutron at room temperature (25°C)?