Difference between revisions of "Critical Mass"

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*[http://en.wikipedia.org/wiki/1919 1919]
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*[https://en.wikipedia.org/wiki/1919 1919]
 
==Definition==
 
==Definition==
 
*1: a size, [[number]], or amount large enough to produce a particular result  
 
*1: a size, [[number]], or amount large enough to produce a particular result  
 
==Description==
 
==Description==
A '''critical mass''' is the smallest amount of [http://en.wikipedia.org/wiki/Fissile fissile] material needed for a sustained [http://en.wikipedia.org/wiki/Nuclear_chain_reaction nuclear chain reaction]. The critical mass of a fissionable material depends upon its [[nuclear]] properties (e.g. the nuclear fission cross-section), its [[density]], its shape, its enrichment, its [[purity]], its [[temperature]] and its [[surroundings]].
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A '''critical mass''' is the smallest amount of [https://en.wikipedia.org/wiki/Fissile fissile] material needed for a sustained [https://en.wikipedia.org/wiki/Nuclear_chain_reaction nuclear chain reaction]. The critical mass of a fissionable material depends upon its [[nuclear]] properties (e.g. the nuclear fission cross-section), its [[density]], its shape, its enrichment, its [[purity]], its [[temperature]] and its [[surroundings]].
  
When a [http://en.wikipedia.org/wiki/Nuclear_chain_reaction nuclear chain reaction] in a [[mass]] of fissile material is self-sustaining, the mass is said to be in a ''critical state'' in which there is no increase or decrease in [[power]], [[temperature]] or [http://en.wikipedia.org/wiki/Neutron neutron] population.
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When a [https://en.wikipedia.org/wiki/Nuclear_chain_reaction nuclear chain reaction] in a [[mass]] of fissile material is self-sustaining, the mass is said to be in a ''critical state'' in which there is no increase or decrease in [[power]], [[temperature]] or [https://en.wikipedia.org/wiki/Neutron neutron] population.
  
A numerical measure of a critical mass is dependent on the [http://en.wikipedia.org/wiki/Nuclear_chain_reaction#Effective_neutron_multiplication_factor effective neutron multiplication factor k], the [[average]] number of neutrons released per fission [[event]] that go on to cause another fission event rather than being [[absorbed]] or leaving the material. When k = 1, the [[mass]] is ''critical'', and the chain reaction is barely self-sustaining.
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A numerical measure of a critical mass is dependent on the [https://en.wikipedia.org/wiki/Nuclear_chain_reaction#Effective_neutron_multiplication_factor effective neutron multiplication factor k], the [[average]] number of neutrons released per fission [[event]] that go on to cause another fission event rather than being [[absorbed]] or leaving the material. When k = 1, the [[mass]] is ''critical'', and the chain reaction is barely self-sustaining.
<center>For lessons on the [[topic]] of '''''Critical Mass''''', follow [http://nordan.daynal.org/wiki/index.php?title=Category:Critical_Mass '''''this link'''''].</center>
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<center>For lessons on the [[topic]] of '''''Critical Mass''''', follow [https://nordan.daynal.org/wiki/index.php?title=Category:Critical_Mass '''''this link'''''].</center>
 
A '''''subcritical''''' mass is a [[mass]] of fissile material that does not have the [[ability]] to sustain a fission chain reaction. A population of neutrons introduced to a subcritical assembly will [[exponentially]] decrease. In this case, k < 1. A steady rate of [[spontaneous]] fissions causes a [[proportionally]] steady level of neutron activity. The constant of proportionality increases as k increases.
 
A '''''subcritical''''' mass is a [[mass]] of fissile material that does not have the [[ability]] to sustain a fission chain reaction. A population of neutrons introduced to a subcritical assembly will [[exponentially]] decrease. In this case, k < 1. A steady rate of [[spontaneous]] fissions causes a [[proportionally]] steady level of neutron activity. The constant of proportionality increases as k increases.
  
A '''''supercritical''''' mass is one where there is an increasing [[rate]] of [http://en.wikipedia.org/wiki/Nuclear_fission fission]. The [[material]] may settle into [[equilibrium]] (i.e. become critical again) at an elevated temperature/power level or destroy itself, by which equilibrium is reached. In the case of ''supercriticality'', k > 1.[http://en.wikipedia.org/wiki/Critical_mass]
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A '''''supercritical''''' mass is one where there is an increasing [[rate]] of [https://en.wikipedia.org/wiki/Nuclear_fission fission]. The [[material]] may settle into [[equilibrium]] (i.e. become critical again) at an elevated temperature/power level or destroy itself, by which equilibrium is reached. In the case of ''supercriticality'', k > 1.[https://en.wikipedia.org/wiki/Critical_mass]
  
 
[[Category: Physics]]
 
[[Category: Physics]]

Latest revision as of 23:45, 12 December 2020

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Definition

  • 1: a size, number, or amount large enough to produce a particular result

Description

A critical mass is the smallest amount of fissile material needed for a sustained nuclear chain reaction. The critical mass of a fissionable material depends upon its nuclear properties (e.g. the nuclear fission cross-section), its density, its shape, its enrichment, its purity, its temperature and its surroundings.

When a nuclear chain reaction in a mass of fissile material is self-sustaining, the mass is said to be in a critical state in which there is no increase or decrease in power, temperature or neutron population.

A numerical measure of a critical mass is dependent on the effective neutron multiplication factor k, the average number of neutrons released per fission event that go on to cause another fission event rather than being absorbed or leaving the material. When k = 1, the mass is critical, and the chain reaction is barely self-sustaining.

For lessons on the topic of Critical Mass, follow this link.

A subcritical mass is a mass of fissile material that does not have the ability to sustain a fission chain reaction. A population of neutrons introduced to a subcritical assembly will exponentially decrease. In this case, k < 1. A steady rate of spontaneous fissions causes a proportionally steady level of neutron activity. The constant of proportionality increases as k increases.

A supercritical mass is one where there is an increasing rate of fission. The material may settle into equilibrium (i.e. become critical again) at an elevated temperature/power level or destroy itself, by which equilibrium is reached. In the case of supercriticality, k > 1.[1]