Wikipedia:Featured article candidates/Chicago Pile-1/archive1

The following is an archived discussion of a featured article nomination. Please do not modify it. Subsequent comments should be made on the article's talk page or in Wikipedia talk:Featured article candidates. No further edits should be made to this page.

The article was promoted by Ian Rose via FACBot (talk) 15:12, 9 September 2016 [1].

---

Chicago Pile-1

Nominator(s): Hawkeye7 (talk) 23:16, 18 July 2016 (UTC)

I find it fascinating that you can pile rocks in a heap, and strange and wonderful things happen. Based on the science of neutrons, whose existence was demonstrated just ten years before, and which cannot be seen, only inferred. Hawkeye7 (talk) 23:16, 18 July 2016 (UTC)

Source review - spotchecks not done

• FN29-30: Atomic Heritage would be better described as the publisher rather than the author
• FN75: university is the publisher, shouldn't be italicized. Also, this citation includes "The" in the name but FN105 does not - which is correct? Nikkimaria (talk) 03:44, 26 July 2016 (UTC)

Both corrected. Hawkeye7 (talk) 04:50, 26 July 2016 (UTC)

Comments

• "The idea of chemical chain reactions was first put forth in 1913". "put forth" does not sound right to me. How about "suggested"?

  Done. Hawkeye7 (talk) 00:27, 12 August 2016 (UTC)

• "for a situation in which two molecules react to form not just the molecules of the final reaction products, but also some unstable molecules which can further react with the parent molecules to cause more molecules to react." I see this is referenced to a Nobel Prize speech, but it still seems to me obscure, with "molecule" repeated 5 times in one sentence, and it is not obvious what "parent molecule" refers to. The OED definition at [2] "a chemical or nuclear reaction forming intermediate products which react with the original substance and are repeatedly renewed" is far clearer.

  Re-worded to "a situation in which two molecules react to form not just the the final reaction products, but also some unstable molecules which can further react with the parent molecules to cause more to react" Hawkeye7 (talk) 00:27, 12 August 2016 (UTC)

• "neutron moderator" It might be helpful to explain that the moderator is needed (if I have understood correctly) to slow the neutrons down so that they are more likely to be absorbed by the uranium instead of escaping.

  Correct. Added words to that effect. Hawkeye7 (talk) 00:27, 12 August 2016 (UTC)

• I am showing my ignorance but I find the timing fascinating. So they drew up the letter to Roosevelt just before war broke out on 1 September, and he approved the proposal shortly afterwards. Is it known when they first saw the project as a reply to the treat of a German nuclear bomb?

  Not for certain, but some time between January and July 1939. Hawkeye7 (talk) 00:27, 12 August 2016 (UTC)

• " lending his fame to the proposal" "prestige" might be a better word.

  "prestige" is a great word. Hawkeye7 (talk) 00:27, 12 August 2016 (UTC)

• "Its first meeting on 21 October 1939, was attended by Szilard, Teller and Wigner, who persuaded the Army and Navy" Does "who" mean Wigner or the meeting?

  Mostly Wigner, but changed to "The scientists persuaded the Army and Navy" Hawkeye7 (talk) 00:27, 12 August 2016 (UTC)

• "In a nuclear reactor, criticality is achieved when the rate of neutron production is equal to the rate of neutron losses, including both neutron absorption and neutron leakage. Thus, in the simplest case of a bare, homogeneous, steady state nuclear reactor, the neutron leakage and neutron absorption must be equal to neutron production in order to reach criticality." I do not understand this. You apppear to say here that production must equal losses, in the next paragraph that production must exceed losses (which seems logical).

  You don't want a runaway chain reaction, which would be an atomic bomb. So production needs to equal loss. Clarified this. Hawkeye7 (talk) 00:27, 12 August 2016 (UTC)

• A very interesting article. Dudley Miles (talk) 21:26, 11 August 2016 (UTC)

  Thanks for your review! Hawkeye7 (talk) 00:27, 12 August 2016 (UTC)

• Support. A fine article. However, I think "parent molecules" is confusing and "original substance" clearer. Dudley Miles (talk) 09:17, 14 August 2016 (UTC)

  Changed accordingly. Hawkeye7 (talk) 23:52, 15 August 2016 (UTC)

Comments. As always, feel free to revert my copyediting. - Dank (push to talk)

• shake, "clothesline", etc.: I'm not taking a position on the italics or quote marks, here and elsewhere.
• "There was a fear of a catastrophic nuclear meltdown blanketing one of the United States' major urban areas in radioactive fission products": I'm not sure, but this sentence seems to fit more with the following paragraph than the one it's in.
• Support on prose per my standard disclaimer. These are my edits. - Dank (push to talk) 12:14, 12 August 2016 (UTC)

Comments.

• "In order for a chain reaction to occur, additional neutrons had to be emitted from fissioning uranium atoms": I think the point here is that unless more neutrons are emitted than absorbed from each reaction, the chain reaction can't get started because at anything less than 100% efficiency the reactions quickly die away to nothing. I know this is an article about the pile, not the theory, but I think a note at least is necessary to clarify this for readers unfamiliar with the idea. This would also clarify the phrase "neutron multiplication" later in the paragraph.

  Rephrased to "In order for a chain reaction to occur, fissioning uranium atoms had to emit additional neutrons to keep the reaction going" Hawkeye7 (talk) 13:08, 30 August 2016 (UTC)

• " As a back-up plan, he also considered where to find a few tons of heavy water; deuterium would not absorb neutrons like ordinary hydrogen, and was a better moderator than carbon, but heavy water was difficult and expensive to produce": suggest " As a back-up plan, he considered heavy water (deuterium), which would not absorb neutrons like ordinary hydrogen, and was a better moderator than carbon, but heavy water was difficult and expensive to produce, and several tons of it would be needed" to eliminate "where to find", which I think is implied.

  Changed to: "As a back-up plan, he considered heavy water. This contained deuterium, which would not absorb neutrons like ordinary hydrogen, and was a better neutron moderator than carbon; but heavy water was expensive to produce and difficult to produce, and several tons of it might be needed." Hawkeye7 (talk) 13:08, 30 August 2016 (UTC)

• "Fermi determined that a fissioning uranium nucleus produced 1.73 neutrons on average": I see below that the modern estimate for this is 2.4. It might be worth giving that in a note, or else changing the language to make it clear that this was Fermi's estimate with state-of-the-art data as of 1939, not Fermi establishing the currently accepted number.

  Changed to estimated, and added a parenthetical comment about the number of neutrons per uranium-235 fission. Hawkeye7 (talk) 23:01, 31 August 2016 (UTC)

• I'm not familiar with whatever the MoS requirements are for unit conversion, so perhaps you're just constrained by the MoS, but it's a bit ugly to give tonnes, long tons, and short tons, for a single quantity, especially when it occurs twice in a sentence. I see at least one case where there are no unit conversions (towards the end of "origins"). Can't we just give one unit with a link?

  It's just the default. Changed to use only one. Hawkeye7 (talk) 13:08, 30 August 2016 (UTC)

• "the neutron leakage and neutron absorption must be equal, on average": I don't follow this -- surely the requirement is that at least one emitted neutron is absorbed is the criticality requirement? Since the average number of emitted neutrons is 2.4, if 1.1 are absorbed and 1.3 leak, you have criticality, but leakage doesn't equal absorption. And isn't this the same as the discussion of k below? I think I must be missing something here.

  If it is less, then the reaction will die down. If it is more, then it will melt down. Hawkeye7 (talk) 13:08, 30 August 2016 (UTC)

• I think "migration area" and "unreflected" need either links or definitions, inline or in a note.

  Changed to "where M is the surface area and k is the average neutron multiplication factor" and linked neutron reflector. (If I had written it, I would have said "untamped") Hawkeye7 (talk) 13:08, 30 August 2016 (UTC)

• "the reaction power will increase slowly, with a long time constant, slow enough": since you're not presenting the math behind this, "time constant" doesn't really give the reader much, so I think you could cut this to "the reaction power will increase slowly enough".

  Done. Hawkeye7 (talk) 13:08, 30 August 2016 (UTC)

• "The nearby North Stands had a pair of ice skating rinks on the ground floor, which although unrefrigerated, seldom melted in winter": it's too easy to parse this so that "which" refers to the ground floor, so I'd suggest rephrasing. I'm also not clear why it's mentioned -- just to show that the location where the pile was built was extremely cold in winter? If so, I'd say that.

  Done. Hawkeye7 (talk) 13:08, 30 August 2016 (UTC)

• "Leona Woods completed her doctoral thesis and then was detailed to build boron trifluoride neutron detectors": suggest "Leona Woods was detailed to build boron trifluoride neutron detectors as soon as she completed her doctoral thesis".

  Done. Hawkeye7 (talk) 13:08, 30 August 2016 (UTC)

• The shake is only mentioned once; I think it should probably be relegated to a note.

  Removed. Hawkeye7 (talk) 13:08, 30 August 2016 (UTC)

• There's some repetition of the discussion of the delayed neutrons and their importance to criticality. Can this be reduced? The later discussion is written as if the earlier discussion did not exist.

  Somebody added the earlier explanation. Cut it back. Hawkeye7 (talk) 13:08, 30 August 2016 (UTC)

-- First pass completed. Mike Christie (talk - contribs - library) 21:37, 27 August 2016 (UTC)

One more point.

• You have "criticality is achieved when the rate of neutron production is equal to the rate of neutron losses, including both neutron absorption and neutron leakage" and "the neutron leakage and neutron absorption must be equal, on average, to neutron production in order to remain critical" -- I don't think the second instance really does more than repeat the information in the first.

-- Mike Christie (talk - contribs - library) 22:07, 30 August 2016 (UTC)

• Sure. Done. Hawkeye7 (talk) 01:52, 31 August 2016 (UTC)

Support. Looks good to me. Mike Christie (talk - contribs - library) 02:13, 31 August 2016 (UTC)

Oops; just realized you haven't addressed a minor point above; I won't strike the support, but could you look at that? Mike Christie (talk - contribs - library) 02:14, 31 August 2016 (UTC)

Addressed that too. Hawkeye7 (talk) 23:01, 31 August 2016 (UTC)

I think that's an improvement. Mike Christie (talk - contribs - library) 01:34, 1 September 2016 (UTC)

• Closing note: This candidate has been promoted, but there may be a delay in bot processing of the close. Please see WP:FAC/ar, and leave the {{featured article candidates}} template in place on the talk page until the bot goes through. Ian Rose (talk) 15:12, 9 September 2016 (UTC)

The above discussion is preserved as an archive. Please do not modify it. No further edits should be made to this page.