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Nuclear fission has had a peer review by Wikipedia editors which is now archived. It may contain ideas you can use to improve this article.

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Is this sentence in the main text correct?: "...however this process works better for heavier elements which have room in outer nuclear orbitals for the necessary extra neutrons." Aren't orbitals "populated" by electrons?. How ever though i need to check still. --Vrrp 13:13, 11 July 2006 (UTC)

In reading this page, two questions were left unanswered for me: a) what makes uranium and plutonium so special that they are easily used for fission? and b) what's a "thermal neutron"? The term is used without any introduction. --joe (joe at xenotropic.net)

• Agree with b) --Chealer 17:10, 2004 Oct 1 (UTC)

b.) "Thermal neutrons" are at a lower energy level than the "fast neutrons" released from the fission process and are more likely to be absorbed into a U235 atom to continue the fission reactions. "Fast neutrons" are moderated in nuclear reactors by the coolant (usually DI water) to slow them down for more fissions to take place...thus the term "thermal reactor."

I think it looked much nicer the way it was, with the image on the right and the text flowing around it. What did you have against that? Mkweise 21:27 Mar 7, 2003 (UTC)

Because to some people including me the width of the image is little too long. -- Taku 21:29 Mar 7, 2003 (UTC)

I wonder what's "isobars". I thought this was a meteorological term only. --66.36.138.130 14:22, 1 Oct 2004 (UTC)

• It's atoms with the same number of nucleons, as the sentence describes. What confused me is that the sentence reads "giving several isobars" instead of for example "i.e. several isobars" so I was wondering if it was something else.--Chealer 16:26, 2004 Oct 28 (UTC)

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Removed text:

Uranium's most common isotope is U-235 (there being 235 total protons and neutrons in the nucleus).

That is just plain wrong, see Uranium. Andrewa 16:00, 6 Nov 2004 (UTC)

Contents 1 Criticality Issues 2 Huge loss of content? 3 Redundant Material 4 yow -- overhaul needed 5 Overhaul begun 6 Overhaul in progress - split out reactor physics page? 7 Overhaul finished. Reactor physics split out. 7.1 Peer review / FAC preparation 7.2 Bomb energetics 7.3 fast fission 7.4 Article rating 7.5 Misleading

[edit] Criticality Issues

Here or somewhere else with a link, needs a much more detailed discussion of chain reactions, criticality, delayed neutron-fraction and prompt criticality.

Linuxlad 09:59, 26 Nov 2004 (UTC)

ALSO going Prompt-critical does NOT equate to a nuclear bomb. (Most nuclear reactors are designed against a range of postulated reactivity excursions, some of which take them (briefly) 'prompt-critical' - most don't even fail the fuel clad). Nuclear weapons, to be worthy of the name, are ramped through prompt critical at a rate of knots.

I know; the article really needs an explanation. The point is, it's not enough to be above critical mass, a weapon needs to be above prompt critical mass. There are brief explanations of critical/prompt critical in various places, but there should be one here too. Still, a link to prompt critical is essential. --Andrew 18:13, Apr 11, 2005 (UTC)

[edit] Huge loss of content?

Take a look at the changes by 194.83.69.123 on 09:58 3 Nov 2004. Much of the article was deleted, and I don't think anyone caught this. Should it be restored?

Looks like pure vandalism which was not noticed in time. IMHO, the deleted lines should be reconciled with all the edits to date. We can't just revert to 3 Nov. pstudier 00:31, 2004 Dec 8 (UTC)

[edit] Redundant Material

"So, if we separate the U-235 from the U-238 and discard the U-238 (producing enriched uranium), we promote a chain reaction. In fact, the probability of fission of U-235 by high speed neutrons may be great enough to make the use of a moderator unnecessary once the U-238 has been removed.

U-235 is present in natural uranium only to the extent of about one part in 140. Also, the relatively small difference in mass between the two isotopes makes isotope separation difficult. Nevertheless, the possibility of separating U-235 was recognized early on in the Manhattan Project as being of the greatest importance to their success."

This appears twice in the article. I wasn't sure exactly how to resolve the issue, but I wanted to bring it to light for those who have a better idea.

[edit] yow -- overhaul needed

The current article is so disorganized that it is difficult to see where to begin. I just added a discussion on delayed neutrons, then realized that one already existed -- it was just hard to find. I reverted my changes rather than make things even worse, but someone really needs to overhaul this article. Maybe that someone is me -- I'll try to get around to it in the next week or so, but no promises. zowie 17:16, 28 October 2005 (UTC)

[edit] Overhaul begun

I overhauled the introduction. I'm planning next to insert a "physics" section to describe critical and subcritical chain reactions, prompt criticality, fuel selection, delayed neutrons, and reactor poisons. That will probably subsume much of the structure in the sections below the "history" section. zowie 23:36, 7 November 2005 (UTC)

[edit] Overhaul in progress - split out reactor physics page?

I've been working my way through summarizing fission reactor physics, and got a comment from DV8 XL2 (Hi, DV8 XL2) that the article is getting quite long. I agree, but feel that the discussion of reactor physics is useful as there really isn't one elsewhere. What do people think about splitting the (still-in-progress) reactor physics section out into its own page, or about trying to merge it with nuclear reactor? zowie 18:35, 11 November 2005 (UTC)

• Finish it up here zowie, and then deside. DV8 2XL 19:21, 11 November 2005 (UTC)

[edit] Overhaul finished. Reactor physics split out.

I believe the article reads much more smoothly now. I cut out a small amount of the historical discussion and merged the rest into the description of fission. We still probably need a small section on political importance (weapons + power) but maybe there's one somewhere else that we can just refer to? zowie 00:01, 19 November 2005 (UTC)

• Well done. You have produced a very readable and informative article. The only problem is you may have set the bar too high for yourself. ;) DV8 2XL 00:28, 19 November 2005 (UTC)

[edit] Peer review / FAC preparation

I've requested peer review for this page as it seems to be sort of stable and I'd like to get it polished enough for FA status. (Also: I got rid of the political relevance to-do item on this talk page, since politics are mentioned in the intro and thoroughly discussed in some of the linked-to articles). zowie 03:58, 19 February 2006 (UTC)

The article is good, but if you leave away everything which concerning U and Pu fission than not much is there anymore. Fission is also possible with other particls than neutrons and nearly all other cores can be cleaved with high energy particles. And this is the major us in physiks. The only real use is for sure is U and Pu fission so the article is OK but it should mention the other possibilities too.217.185.50.187 17:47, 19 February 2006 (UTC)

Thanks! That's a good point -- I'll add something by tomorrow night. zowie 18:10, 19 February 2006 (UTC)

[edit] Bomb energetics

The article notes that little boy had a yeild of 15,000 tons TNT with a 4 ton bomb (actually the yield was more like 13,000 tons but nevermind). That's still about 4,000 to 1, vs. TNT. The article says that modern weapons are "literally" thousands of times more energetic, but that's flat-out wrong. The most efficient bomb ever constructed was the Tsar Bomba, which had a yield of 50 MT and a weight of 26 tons. It would have had an identical weight but twice the yeild if a uranium-238 jacket instead of lead had been used (the lead was used as a substitute tamper to cut the yield of nasty fission products for the test). This gives a ratio 100,000,000/26 = about 4 million to 1 vs. TNT, which is at most 1000 times that for little boy. That's the best that has been done, and it has only been done at the increased efficiencies possible in a monster thermonuke. Modern smaller weapons (see the Wiki for W88) have efficiencies of about 475,000 tons/.36 tons = 1.3 million to 1, which is 1,300,000/4000 = 325 times that of little boy. I have therefore changed the statement to "hundreds of times," which is of the right order. Sbharris 20:25, 3 April 2006 (UTC)

[edit] fast fission

The phrase "fast fission" doesn't appear anywhere in the article, although it's an important type of fission. I think we need a mention and link to the article. Night Gyr 21:55, 19 April 2006 (UTC)

[edit] Article rating

I think this article is in very good shape, and probably meets the standards of Wikipedia:Good articles. However, I can't quite give it an A-class rating, because I think the overall structure of the article (what headings are used, etc.) could use some work, and there could be improvements in the references (more hard scientific literature). -- SCZenz 06:45, 6 June 2006 (UTC)

[edit] Misleading

The section on fission bombs contains the phrase: Modern nuclear weapons are literally hundreds of times more energetic for their weight than the first atomic bombs, so that a modern single missile warhead bomb weighing less than 1/8th as much as Little Boy (see for example W88) has a yield of 475,000 tons of TNT, and could bring destruction to 10 times the city area. True, but the W88 is not a pure fission weapon — it is a hydrogen bomb. I'm not sure how one would want to re-work the sentence to make this more clear (I can't recall offhand if any of the "modern" nuclear weapons are not hydrogen bombs). Ivy King is the standard example of the max limits of a pure fission bomb, though it is not really a "modern" weapon (1952). Just a thought... --Fastfission 01:58, 20 July 2006 (UTC)