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The article needs clean-up?? It looks fine to me now, and especially since the main concern re: "fissile" is in stuff that you can manufacture in large quantities, like we can do for U-233, U-235, and Pu-239. Does anyone know of any more isotopes?? 74.249.92.92 ( talk) 06:57, 28 August 2008 (UTC)
“Several … isotopes are known to be fissile, all of them having … odd atomic mass numbers. These include: … Curium-244[2]”
I do not know the subject enough to relate oddness to fissilitude and, therefore, to fix the article. Oddly, my degree is in physics; I recall no rule postulating that only odd-weighing isotopes be fissile (no implication that there is no such rule). The reference [2] mentioning 244Cu as a fissile material is but a safety instruction, and it is OK for such documents to err on the “safe” side, so this reference is not convincing enough to me for a blank-minded edit.
“Several other transuranic isotopes are known to be fissile, all of them having… even atomic numbers…. These include: Neptunium-237[1] … Americium-241”
None of the nuclei 241Am, 237Np and 244Cm is fissile. All of them undergo fission after irradiation with fast neutrons, but not with thermal neutrons.
Furthermore, only 244Cm has an even mass number (244) and an even atomic number(96). Both 237Np and 241Am have an odd atomic number (93 and 95 respectively) and an odd mass number.
-- Pgrouse 11:04, 5 October 2006 (UTC)
The OE isotopes are unbalanced and less stable, and are fissable because they can be caused to fission by thermal neutrons. The EE isotopes are balanced and more stable (long halflived) and can only be fissioned with fast neutrons (>14Mev), and therefore are fissionable> WFPM ( talk) 02:11, 21 April 2011 (UTC)
The word fissile can be used to refer to any item which can be split. For example it is used in geology to refer to slates and shales. Should the definition be limited to the specific case of nuclear fission?? —Preceding unsigned comment added by 155.198.91.107 ( talk) 16:06, 4 March 2008 (UTC)
Neptunium-237 can sustain a chain reaction with fast neutrons, but rarely fissions with slow neutrons. Does this mean it is fissile or not? This also contradicts a sentence in the article stating that all fissile materials can sustain a chain reaction with both fast and slow neutrons. -- JWB ( talk) 05:16, 12 March 2009 (UTC)
In the technical sense Np-237 is not fissile, since it does not have a large fission cross section for thermal neutrons. But "fissile" material is commonly understood to mean material you can make a bomb from - i.e. that supports a fast fission chain reaction. In that sense NP-237 is fissile. NPguy ( talk) 19:23, 12 March 2009 (UTC)
What do we say in the articles then? And are there sources for either or both of the conflicting definitions? -- JWB ( talk) 03:27, 13 March 2009 (UTC)
I added a line to this article. See what you think. NPguy ( talk) 09:08, 15 March 2009 (UTC)
Good, but we need to address the second sentence of the article, and get references for each legitimate definition of "fissile". Also, is there commonly used terminology disambiguating being able to sustain thermal and fast neutron chain reactions?
Almost all transuranics seem to have a critical mass - see Critical mass#Critical mass of a bare sphere.-- JWB ( talk) 12:44, 15 March 2009 (UTC)
[2], one of the references in Critical mass, uses "thermal/fast spectrum fissile actinide nuclides". -- JWB ( talk) 13:12, 15 March 2009 (UTC)
hello all,
Did anyone notice that Jeopardy had a question last week relating the most important criteria in selecting U-235 was that it had an odd number of neutrons???
That whole section of the article is CONFUSING and, like someone said above, sounds way to much like a rule of thumb.
I am doing some research to try and clarify this point. Right now, from reading "Introduction to Nuclear Engineering" By J.R. Lamarsh (Prentice hall 3rd Edition) I can find no equivalent explanation for fissile behaviour and odd number of neutrons. He relates it solely to the number of neutrons per fission relased in a fuel mixture and the ratio of absorption to fission cross sections (See equation 3.51). of course, the underlying physics could still deal with # of nuetrons which is the point I am still researching.
In any case one line that DEFINITELY should be changed is the line about " More generally, elements with an even number of protons and an even number of neutrons, and located near a well-known curve in nuclear physics of atomic number vs. atomic mass number are more stable than others - and hence, less likely to undergo fission"
The well known line in nuclear physics is not a even to even neutron/ proton line... the line is # neutrons = # protons. As the Mass of the nuclei increases the "stable line" deviates further and further away from this line... regardless of if you have even or odd number of neutrons. what the line indicates is that as mass increases you need much more neutrons per proton in order to maintain stability. (i.e. you need the nuclear force to overcome the electromagnetic repulsion of the positeveloy charged protons). This includes isotopes with both even and odd numbers of neutrons thus it is not clear to me what point the article is trying to make. Do you mean closer to the line relative to isotopes of the same element?
Anyway, thank you. Sorry for the spelling... A.L. Daley —Preceding unsigned comment added by 192.75.48.150 ( talk) 12:30, 25 May 2009 (UTC)
Let's just hypothesize that An E isotope starts out with even number of proton/neutron pairs, so it can be balanced or not, depending on the number of extra neutrons. With an even number of extra extra neutrons you then have a relatively balanced EE type isotope which is the least unstable. However with an odd number of extra neutrons, you then have an unbalanced and therefor more unstable EO type isotope. In the case of an O type isotope, you start out with an odd number of proton/neutron pairs, which is unbalanced, and which cannot be completely balanced with extra neutrons, but can be less unbalanced with an odd number of extra neutrons (making an OE isotope) than it can with an even number of extra neutrons, (making an OO isotope). Of the 255 stable isotopes, approximately 150 are EE's, approximately 55 are OE's, and approximately 50 are EO's. So it's significant. WFPM ( talk) 02:29, 21 April 2011 (UTC)
Further research has told me that the odd-even concept in the article has some validity.
In the Lamarsh reference above see section 2.12 Nuclear Models, "Liquid Drop Model".
However, I beleive the concept as it relates to Fission (and thus fissile materials) is incomplete. I beleive a discussion of the formation of a Compound Nucleus, Binding Energy, and Fission is required... See Section 3.7 of Lamarsh "Fission". particularily useful is the table of "Critical Energies for Fission" is very useful. In this table, the change in Critical Energy as one alternates between even and odd numbers and the effect that this has on an isotope being fissile or fissionable is much mroe relavant than the generalized disucssion on stability that is now included in the article.
Thoughts?
A. Daley —Preceding unsigned comment added by 192.75.48.150 ( talk) 13:21, 25 May 2009 (UTC)
http://www.tpub.com/doenuclearphys/nuclearphysics26.htm
Seems to be an appropriate discussion of the phenomenon... I think it is a lot less confusing to disuss energy first, then bring in the odd-even concept. —Preceding unsigned comment added by 192.75.48.150 ( talk) 13:30, 25 May 2009 (UTC)
The result of the move request was: Move. Cúchullain t/ c 23:31, 10 February 2014 (UTC)
Fissile →
Fissile material – (1) "Fissile" is an adjective, not a noun or noun phrase; (2) the article's subject is material suitable for atomic fission, not cell division, secession, etc.
Sardanaphalus (
talk)
16:24, 1 February 2014 (UTC)
*'''Support'''
or *'''Oppose'''
, then sign your comment with ~~~~
. Since
polling is not a substitute for discussion, please explain your reasons, taking into account
Wikipedia's policy on article titles.Note that the target has a significant edit history, as the material from it was merged to this article. This history should be preserved for copyleft reasons. Andrewa ( talk) 17:59, 9 February 2014 (UTC)
I had a look at this article, and tried to wrap my head around the meaning of "fissile" and its relationship to "radioactive". I understand that they are very different (if related) events, but after making an attempt to write it down, realized that I just don't have the vocabulary at my fingertips to correctly explain the difference. Am putting in this section here on the talk page to request that someone more eloquent in nuclear physics than I give it a go. I think it might go well under the heading "Fissile vs. fusionable" (perhaps as "Fissile vs. fusionable vs. radioactive"?). Not that it needs this, of course, but for the the lay person, things just get confusing rather quickly at the quantum level. Please consider the request. Keep it simple. Thanks! KDS4444 Talk 14:58, 28 November 2015 (UTC)
Release two or more neutrons on average per neutron capture On average, it just needs to be enough above one to sustain the chain reaction. It doesn't seem that two is so special, though. At least some have to release two or more for the average to be above one. Gah4 ( talk) 14:56, 3 June 2016 (UTC)
From a recent edit, referencing the NRC, fissionable is: A nuclide that is capable of undergoing fission after capturing either high-energy (fast) neutrons or low-energy thermal (slow) neutrons. Seems to me that this is one of those you know what they meant, but not what they said. U238 is not capable of fissioning with slow neutrons, but is with fast neutrons, and that is the most confusing way to say it. As far as I know, there are no nuclides that will fission with thermal neutrons, but not with fast (prompt) neutrons, so there is no need to make the distinction what this quote seems to be making. Gah4 ( talk) 01:43, 25 January 2019 (UTC)
Article currently currently reads Although the terms were formerly synonymous... but no reference is given.
I'm dubious. The term fissile has always been a technical term, coined to distinguish materials that can sustain a fission chain reaction from those that can't.
The two terms have often been confused by people who think they know more than they do, and still are. That doesn't make them synonyms! But to state that they are or have been synonyms does serve to conceal the ignorance of these people, and even encourage such ignorance. Is that the idea? Andrewa ( talk) 23:40, 18 August 2020 (UTC)?
I have added a dubious template. I intended to add a a simple unsourced or citation needed template but then noticed that the dubious template is OK in cases such as this. Template:Dubious/doc#Incorrect uses reads in part to flag unsourced statements, unless you think they are incorrect. (my emphasis)
That is exactly the point here. The statement is not only unsourced, it is subtly politically charged, and likely to prove to be complete rubbish. Andrewa ( talk) 23:55, 18 August 2020 (UTC)
It's a dubious claim, but also unnecessary to the article, so I took the obvious step and deleted it. NPguy ( talk) 03:27, 21 August 2020 (UTC)
No nuclear bomb, fission or fusion, has ever been built or even AFAIK seriously proposed without a critical mass of fissile material. U-235 and Pu-239 and combinations of them have been used to date. U-233 has been used in combination with other fissile material, and in at least one very low yield but successful test.
No nuclear fission reactor, whether fast, moderated, or partly thermalised, can go critical without fissile material in the fuel. The only natural fissile material of any importance is U-235. All fission reactor programs to date have started with this material. Some have used enriched Uranium and some natural, but in either case it's the U-235 that is the fuel.
Our article does not make any of that clear at all, in my opinion. It has some political ramifications, and as a committed advocate of nuclear power I am unwilling to make any change to the article that is controversial. Andrewa ( talk) 17:03, 19 August 2020 (UTC)
I read at the Nuclear Regulatory Commission glossary ( currently at least):
Fissile material A nuclide that is capable of undergoing fission after capturing low-energy thermal (slow) neutrons. Although sometimes used as a synonym for fissionable material, this term has acquired its more-restrictive interpretation with the limitation that the nuclide must be fissionable by thermal neutrons. With that interpretation, the three primary fissile materials are uranium-233, uranium-235, and plutonium-239. This definition excludes natural uranium and depleted uranium that have not been irradiated, or have only been irradiated in thermal reactors. Page Last Reviewed/Updated Monday, June 29, 2020
This is I think at least part of our problem with the Fissile material article. Watch this space! Andrewa ( talk) 21:58, 24 August 2020 (UTC)
The following Wikimedia Commons file used on this page or its Wikidata item has been nominated for deletion:
Participate in the deletion discussion at the nomination page. — Community Tech bot ( talk) 04:38, 4 April 2023 (UTC)
Is the Ronen fissile rule actually useful? Looking at Uranium, for example, it tells me U-225 and U-229 are fissile but those are too light and not even included in the discussion of fissile isotopes. It gives us isotopes that are too light and unstable to be useful. 98.183.98.6 ( talk) 19:47, 11 May 2023 (UTC)
This is the
talk page for discussing improvements to the
Fissile material article. This is not a forum for general discussion of the article's subject. |
Article policies
|
Find sources: Google ( books · news · scholar · free images · WP refs) · FENS · JSTOR · TWL |
![]() | This article is rated C-class on Wikipedia's
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The article needs clean-up?? It looks fine to me now, and especially since the main concern re: "fissile" is in stuff that you can manufacture in large quantities, like we can do for U-233, U-235, and Pu-239. Does anyone know of any more isotopes?? 74.249.92.92 ( talk) 06:57, 28 August 2008 (UTC)
“Several … isotopes are known to be fissile, all of them having … odd atomic mass numbers. These include: … Curium-244[2]”
I do not know the subject enough to relate oddness to fissilitude and, therefore, to fix the article. Oddly, my degree is in physics; I recall no rule postulating that only odd-weighing isotopes be fissile (no implication that there is no such rule). The reference [2] mentioning 244Cu as a fissile material is but a safety instruction, and it is OK for such documents to err on the “safe” side, so this reference is not convincing enough to me for a blank-minded edit.
“Several other transuranic isotopes are known to be fissile, all of them having… even atomic numbers…. These include: Neptunium-237[1] … Americium-241”
None of the nuclei 241Am, 237Np and 244Cm is fissile. All of them undergo fission after irradiation with fast neutrons, but not with thermal neutrons.
Furthermore, only 244Cm has an even mass number (244) and an even atomic number(96). Both 237Np and 241Am have an odd atomic number (93 and 95 respectively) and an odd mass number.
-- Pgrouse 11:04, 5 October 2006 (UTC)
The OE isotopes are unbalanced and less stable, and are fissable because they can be caused to fission by thermal neutrons. The EE isotopes are balanced and more stable (long halflived) and can only be fissioned with fast neutrons (>14Mev), and therefore are fissionable> WFPM ( talk) 02:11, 21 April 2011 (UTC)
The word fissile can be used to refer to any item which can be split. For example it is used in geology to refer to slates and shales. Should the definition be limited to the specific case of nuclear fission?? —Preceding unsigned comment added by 155.198.91.107 ( talk) 16:06, 4 March 2008 (UTC)
Neptunium-237 can sustain a chain reaction with fast neutrons, but rarely fissions with slow neutrons. Does this mean it is fissile or not? This also contradicts a sentence in the article stating that all fissile materials can sustain a chain reaction with both fast and slow neutrons. -- JWB ( talk) 05:16, 12 March 2009 (UTC)
In the technical sense Np-237 is not fissile, since it does not have a large fission cross section for thermal neutrons. But "fissile" material is commonly understood to mean material you can make a bomb from - i.e. that supports a fast fission chain reaction. In that sense NP-237 is fissile. NPguy ( talk) 19:23, 12 March 2009 (UTC)
What do we say in the articles then? And are there sources for either or both of the conflicting definitions? -- JWB ( talk) 03:27, 13 March 2009 (UTC)
I added a line to this article. See what you think. NPguy ( talk) 09:08, 15 March 2009 (UTC)
Good, but we need to address the second sentence of the article, and get references for each legitimate definition of "fissile". Also, is there commonly used terminology disambiguating being able to sustain thermal and fast neutron chain reactions?
Almost all transuranics seem to have a critical mass - see Critical mass#Critical mass of a bare sphere.-- JWB ( talk) 12:44, 15 March 2009 (UTC)
[2], one of the references in Critical mass, uses "thermal/fast spectrum fissile actinide nuclides". -- JWB ( talk) 13:12, 15 March 2009 (UTC)
hello all,
Did anyone notice that Jeopardy had a question last week relating the most important criteria in selecting U-235 was that it had an odd number of neutrons???
That whole section of the article is CONFUSING and, like someone said above, sounds way to much like a rule of thumb.
I am doing some research to try and clarify this point. Right now, from reading "Introduction to Nuclear Engineering" By J.R. Lamarsh (Prentice hall 3rd Edition) I can find no equivalent explanation for fissile behaviour and odd number of neutrons. He relates it solely to the number of neutrons per fission relased in a fuel mixture and the ratio of absorption to fission cross sections (See equation 3.51). of course, the underlying physics could still deal with # of nuetrons which is the point I am still researching.
In any case one line that DEFINITELY should be changed is the line about " More generally, elements with an even number of protons and an even number of neutrons, and located near a well-known curve in nuclear physics of atomic number vs. atomic mass number are more stable than others - and hence, less likely to undergo fission"
The well known line in nuclear physics is not a even to even neutron/ proton line... the line is # neutrons = # protons. As the Mass of the nuclei increases the "stable line" deviates further and further away from this line... regardless of if you have even or odd number of neutrons. what the line indicates is that as mass increases you need much more neutrons per proton in order to maintain stability. (i.e. you need the nuclear force to overcome the electromagnetic repulsion of the positeveloy charged protons). This includes isotopes with both even and odd numbers of neutrons thus it is not clear to me what point the article is trying to make. Do you mean closer to the line relative to isotopes of the same element?
Anyway, thank you. Sorry for the spelling... A.L. Daley —Preceding unsigned comment added by 192.75.48.150 ( talk) 12:30, 25 May 2009 (UTC)
Let's just hypothesize that An E isotope starts out with even number of proton/neutron pairs, so it can be balanced or not, depending on the number of extra neutrons. With an even number of extra extra neutrons you then have a relatively balanced EE type isotope which is the least unstable. However with an odd number of extra neutrons, you then have an unbalanced and therefor more unstable EO type isotope. In the case of an O type isotope, you start out with an odd number of proton/neutron pairs, which is unbalanced, and which cannot be completely balanced with extra neutrons, but can be less unbalanced with an odd number of extra neutrons (making an OE isotope) than it can with an even number of extra neutrons, (making an OO isotope). Of the 255 stable isotopes, approximately 150 are EE's, approximately 55 are OE's, and approximately 50 are EO's. So it's significant. WFPM ( talk) 02:29, 21 April 2011 (UTC)
Further research has told me that the odd-even concept in the article has some validity.
In the Lamarsh reference above see section 2.12 Nuclear Models, "Liquid Drop Model".
However, I beleive the concept as it relates to Fission (and thus fissile materials) is incomplete. I beleive a discussion of the formation of a Compound Nucleus, Binding Energy, and Fission is required... See Section 3.7 of Lamarsh "Fission". particularily useful is the table of "Critical Energies for Fission" is very useful. In this table, the change in Critical Energy as one alternates between even and odd numbers and the effect that this has on an isotope being fissile or fissionable is much mroe relavant than the generalized disucssion on stability that is now included in the article.
Thoughts?
A. Daley —Preceding unsigned comment added by 192.75.48.150 ( talk) 13:21, 25 May 2009 (UTC)
http://www.tpub.com/doenuclearphys/nuclearphysics26.htm
Seems to be an appropriate discussion of the phenomenon... I think it is a lot less confusing to disuss energy first, then bring in the odd-even concept. —Preceding unsigned comment added by 192.75.48.150 ( talk) 13:30, 25 May 2009 (UTC)
The result of the move request was: Move. Cúchullain t/ c 23:31, 10 February 2014 (UTC)
Fissile →
Fissile material – (1) "Fissile" is an adjective, not a noun or noun phrase; (2) the article's subject is material suitable for atomic fission, not cell division, secession, etc.
Sardanaphalus (
talk)
16:24, 1 February 2014 (UTC)
*'''Support'''
or *'''Oppose'''
, then sign your comment with ~~~~
. Since
polling is not a substitute for discussion, please explain your reasons, taking into account
Wikipedia's policy on article titles.Note that the target has a significant edit history, as the material from it was merged to this article. This history should be preserved for copyleft reasons. Andrewa ( talk) 17:59, 9 February 2014 (UTC)
I had a look at this article, and tried to wrap my head around the meaning of "fissile" and its relationship to "radioactive". I understand that they are very different (if related) events, but after making an attempt to write it down, realized that I just don't have the vocabulary at my fingertips to correctly explain the difference. Am putting in this section here on the talk page to request that someone more eloquent in nuclear physics than I give it a go. I think it might go well under the heading "Fissile vs. fusionable" (perhaps as "Fissile vs. fusionable vs. radioactive"?). Not that it needs this, of course, but for the the lay person, things just get confusing rather quickly at the quantum level. Please consider the request. Keep it simple. Thanks! KDS4444 Talk 14:58, 28 November 2015 (UTC)
Release two or more neutrons on average per neutron capture On average, it just needs to be enough above one to sustain the chain reaction. It doesn't seem that two is so special, though. At least some have to release two or more for the average to be above one. Gah4 ( talk) 14:56, 3 June 2016 (UTC)
From a recent edit, referencing the NRC, fissionable is: A nuclide that is capable of undergoing fission after capturing either high-energy (fast) neutrons or low-energy thermal (slow) neutrons. Seems to me that this is one of those you know what they meant, but not what they said. U238 is not capable of fissioning with slow neutrons, but is with fast neutrons, and that is the most confusing way to say it. As far as I know, there are no nuclides that will fission with thermal neutrons, but not with fast (prompt) neutrons, so there is no need to make the distinction what this quote seems to be making. Gah4 ( talk) 01:43, 25 January 2019 (UTC)
Article currently currently reads Although the terms were formerly synonymous... but no reference is given.
I'm dubious. The term fissile has always been a technical term, coined to distinguish materials that can sustain a fission chain reaction from those that can't.
The two terms have often been confused by people who think they know more than they do, and still are. That doesn't make them synonyms! But to state that they are or have been synonyms does serve to conceal the ignorance of these people, and even encourage such ignorance. Is that the idea? Andrewa ( talk) 23:40, 18 August 2020 (UTC)?
I have added a dubious template. I intended to add a a simple unsourced or citation needed template but then noticed that the dubious template is OK in cases such as this. Template:Dubious/doc#Incorrect uses reads in part to flag unsourced statements, unless you think they are incorrect. (my emphasis)
That is exactly the point here. The statement is not only unsourced, it is subtly politically charged, and likely to prove to be complete rubbish. Andrewa ( talk) 23:55, 18 August 2020 (UTC)
It's a dubious claim, but also unnecessary to the article, so I took the obvious step and deleted it. NPguy ( talk) 03:27, 21 August 2020 (UTC)
No nuclear bomb, fission or fusion, has ever been built or even AFAIK seriously proposed without a critical mass of fissile material. U-235 and Pu-239 and combinations of them have been used to date. U-233 has been used in combination with other fissile material, and in at least one very low yield but successful test.
No nuclear fission reactor, whether fast, moderated, or partly thermalised, can go critical without fissile material in the fuel. The only natural fissile material of any importance is U-235. All fission reactor programs to date have started with this material. Some have used enriched Uranium and some natural, but in either case it's the U-235 that is the fuel.
Our article does not make any of that clear at all, in my opinion. It has some political ramifications, and as a committed advocate of nuclear power I am unwilling to make any change to the article that is controversial. Andrewa ( talk) 17:03, 19 August 2020 (UTC)
I read at the Nuclear Regulatory Commission glossary ( currently at least):
Fissile material A nuclide that is capable of undergoing fission after capturing low-energy thermal (slow) neutrons. Although sometimes used as a synonym for fissionable material, this term has acquired its more-restrictive interpretation with the limitation that the nuclide must be fissionable by thermal neutrons. With that interpretation, the three primary fissile materials are uranium-233, uranium-235, and plutonium-239. This definition excludes natural uranium and depleted uranium that have not been irradiated, or have only been irradiated in thermal reactors. Page Last Reviewed/Updated Monday, June 29, 2020
This is I think at least part of our problem with the Fissile material article. Watch this space! Andrewa ( talk) 21:58, 24 August 2020 (UTC)
The following Wikimedia Commons file used on this page or its Wikidata item has been nominated for deletion:
Participate in the deletion discussion at the nomination page. — Community Tech bot ( talk) 04:38, 4 April 2023 (UTC)
Is the Ronen fissile rule actually useful? Looking at Uranium, for example, it tells me U-225 and U-229 are fissile but those are too light and not even included in the discussion of fissile isotopes. It gives us isotopes that are too light and unstable to be useful. 98.183.98.6 ( talk) 19:47, 11 May 2023 (UTC)