Talk:Demon core

message: There are some references on the net, that the "Daemon Core" was nicknamed "Rufus".
Is this true? Some References:
http://www.curtainup.com/louisslotinsonata.html
http://www.paulmullin.org/Slotin%20Sonata.htm
http://query.nytimes.com/gst/fullpage.html?res=9E06E7DA113FF930A35757C0A9679C8B63&sec=&spon=&pagewanted=2  —Preceding unsigned comment added by 77.49.82.116 (talk) 23:56, 13 March 2009 (UTC)
thread_title: Rufus

message: Shouldn't the innocent victims get a mention, and not just the man who caused their deaths?  One assumes they were lab techs.  —Preceding unsigned comment added by 71.185.20.180 (talk) 03:38, 22 January 2009 (UTC)
replies: text: The number was incorrect. There were 8 men in the lab, and only Slotin died. His quick reaction doubtless kept the other seven from receiving fatal radiation doses. SBHarris 06:50, 22 January 2009 (UTC)
replies: text: The other man in the room in Daghlian's accident is mentioned. I don't think saying who was present for Slotin's accident is unreasonable, and I'd like to see this sort of information preserved somewhere, so I'm going to add a paragraph similar to Daghlian's. SkoreKeep (talk) 18:08, 4 January 2013 (UTC)

text: Someone made a table out of the other people in the room.  OK, but if a table highlights them, the list should be exhaustive, even if a bit repeticious. SkoreKeep (talk) 16:21, 31 March 2014 (UTC)
replies: text:  Maybe something about that should be added to Human furniture. EEng 06:08, 22 December 2022 (UTC)
thread_title:  all but three? 

message: Seems like Demon Core should be capitalized  —Preceding unsigned comment added by 129.105.140.83 (talk) 02:15, 22 January 2009 (UTC)
thread_title:  Caps 

message: Hi there Rememberlands,
Thank you for locating the data on the demon core-did it refer to the core as "The Demon Core", as well when it was placed into ABLE?--Read-write-services (talk) 22:31, 29 November 2007 (UTC)
replies: text: Done--Read-write-services (talk) 21:31, 17 December 2007 (UTC)
thread_title:  Thanks for finding data! 

message: Were these two incidents the basis for the scene in Fat Man and Little Boy where Cusack's character is involved in a similar accident? Might be worth adding to the article, if so. 68Kustom (talk) 21:59, 3 May 2008 (UTC)
replies: text: Yes, these two incidents have been rolled into one for the film. There's some reference to the film in the separate discussion of the incidents (see the Slotin and Daghlian Wikis) but there's nothing here on this one. Feel free to add a short "Cultural reference" tag if you feel it's needed here. SBHarris 06:52, 22 January 2009 (UTC)
thread_title:  Demon core incidents 

message: Should there be a section with more detail about the composition of the Demon Core? Xitit (talk) 22:19, 3 July 2009 (UTC)
thread_title:  Composition? 

message: There is a discrepancy as to when the first victim died. This article says 25 days later but the plutonium article that linked me to this article said 28 days later.  —Preceding unsigned comment added by 68.174.194.98 (talk) 06:25, 29 November 2010 (UTC)
thread_title:  Time of Death 

message: I note an addition in the Cultural references section 
Joseph Kanon uses the first criticality incident as a key plot piece in his 1998 novel "Los Alamos".
which was reverted  as being "probably not notable." but asking for "a reference describing this allusion"
So I went over to Amazon  logged in there and used their 'look inside' feature; if you search for the word "dragon" the criticality accident is indeed mentioned.  Repeating the search on Google Books confirms this  and here is a NY Times book review, which is the kind of ref I think was requested: 
-- Limulus (talk) 05:39, 4 May 2011 (UTC)
thread_title:  Joseph Kanon's Los Alamos 

message: :I have added the direct link to document LA-3611 which describes the accident in detail. http://lib-www.lanl.gov/cgi-bin/getfile?00314607.pdf the differences between the movie "Fat Man and Little Boy" are essentially the date, the fact that in reality one screwdriver was used, and one hand was on the core when it happened, whereas in the movie, two screwdrivers were used, and both hands were on the safe side of the bricks at the time of the accident.  Otherwise, the movie is probably an accurate depiction. 167.142.46.244 (talk) 21:39, 25 July 2011 (UTC)
replies: text: Ummm, except that there was no metal brick barrier in the Slotin accident (see the recreation photos, one of which is on the page).  That was borrowed from Daghlian's accident, probably because it looked more sinister, where he was building such a wall when he dropped the fatal brick. SkoreKeep (talk) 03:34, 20 May 2014 (UTC)
thread_title:  Accurate 

message: Does anyone remember the "We were there" novels?  
http://en.wikipedia.org/wiki/We_Were_There
well, as I recall the one "We Were There at the Opening of the Atomic Era"  includes the tickling the dragons tail incident in the book.
Now I don't know if anyone can get a page and volume cite, to make it official,  but, I thought I would mention it.
http://www.amazon.com/were-there-opening-atomic-books/dp/images/B0007E1AAS  the cover art was actually pretty cool....
so at any rate, shouldn't the cultural references section include a reference to this?   Patbahn (talk) 05:18, 10 April 2012 (UTC)
thread_title:  Cultural Reference : We were there at the opening of the atomic age 

message: In the "Second Incident" section, after the burst of radiation, Slotin reportedly knocks the beryllium half-spheres apart, "stopping the chain reaction and likely saving the lives of the other men in the laboratory." But the article then says that "the heating of the core and shells stopped the criticality within milliseconds of its initiation." From the way it's written, it sounds like it's contradicting itself; first it says Slotin stopped it, then it says it stopped itself. I think it could use some improvement. Light Peak (talk) 20:47, 30 April 2013 (UTC)
replies: text: The second explanation came somewhat after the accident, and is by its nature something of a speculation, as no one ever has tried to experiment with it, as far as I know. Just how tightly did the spheres fit the core? How quickly did the core heat?  Was there any trapped air? Lots of questions there are no good answers to. Then there is a natural tendency to not want to take away from Slotin his correct action; had he not knocked the shell off, it likely would have repeatedly settled back onto the core as it cooled and cycled again.  See next question below. SkoreKeep (talk) 08:48, 19 January 2014 (UTC)

text: In response to User718499522 who complains 'The claim that "it is now known that the heating of the core and shells stopped the criticality within milliseconds of its initiation" is scientifically baseless and is not referenced and/proven in any of this articles sources.' The source is an article about Raemer Schreiber: "...it was stopped by the expansion of the core and the beryllium."  Dr. Schreiber, a physicist, was one of those in the room with Slotin when the accident occurred, and who probably knew more about the accident than any other person. Schreiber went on to work for the AEC/DoE until his retirement, and for one thing designed the remote system that replaced the hands-on methods used to such sorrow. However, I will continue looking for a more definitive statement about that, presumably one with numbers to back it up. I believe this statement should suffice in the meantime. Watch your "scientific baseless", if you please, and note that the Schreiber article was one of the article's sources from long before today. SkoreKeep (talk) 07:27, 18 May 2014 (UTC)
replies: text: I started a recent post about this under "The heating of the core and shells" but just saw this post so wanted to respond. Regarding the sentences, "Instantly, there was a flash of blue light and a wave of heat across Slotin's skin; the core had become supercritical, releasing an intense burst of neutron radiation estimated to have lasted about a half second. Slotin quickly twisted his wrist, flipping the top shell to the floor. The heating of the core and shells stopped the criticality within seconds of its initiation." Source 15 an interview by Dr. Schreiber doesn't mention the color blue, that Slotin felt heat on his skin, that it took seconds to stop, or that it was 'heat' that stopped the reaction but instead that, "It was stopped by the expansion of the core and beryllium, but it was enough to put out a lethal shot of radioactivity." You said, "had he not knocked the shell off, it likely would have repeatedly settled back onto the core as it cooled and cycled again" however I don't see a source saying it had opened before Slotin flipped the top reflector. If regarding Schreiber's comment about expansion and assuming the core's size expanded lifting the top reflector ajar but in nuclear reactions thermal expansion usually refers to heating reducing the core density reducing the core to subcritical and this is what it seems Schreiber is referring to. The "half second" line is referring to source 6 the Los Alamos Labs review of criticality incidents, 2000 Revision report, "The results of fission rate calculations in this sphere, as a function of time for several values of excess reactivity, are shown in Figure 43. Figure 44 represents the total number of fissions to be expected as a function of time for the same excess reactivities. These data are applicable to both accidents because the difference in reflector material has only a small effect on the neutron kinetics. In the first excursion, if the excess reactivity did not exceed 15 ¢, the assembly must have been together for several seconds, which is not unreasonable. In the second event, the experimenter was better prepared to disassemble the material, and it is thought that this was done in a fraction of a second, perhaps <1/2 second." I read it to say exposure calculations were based on the estimated half a second it took Slotin to remove the top reflector which 'implies' that is when the reaction stopped. But the reports analysis also says, "The study and understanding of initiating events and shutdown mechanisms associated with criticality accidents offer potential for limiting the frequency and consequences of such untoward events... These programs, which involved solutions of highly enriched uranium, are supplemented by a series of measurements at Los Alamos using the SHEBA assembly. This assembly is fueled with a 5% enriched uranium solution, that provides information on dose rates near excursions in systems of lower enrichment.88 Analysis of data from KEWB and CRAC has led to relatively simple computer codes that follow the early transient behavior well and rely on thermal expansion and the formation of radiolytic gas for the shutdown mechanisms." So this portion seems to say thermal expansion is a factor if not a key cause of such a shutdown. With out more information I think remarks regarding the color blue, that Slotin felt heat on his skin, and that it took seconds to stop, and even what stopped it, and instead use the reports' implied meaning, 'neutron radiation, the exposure of which was calculated based on the estimated half second between when the sphere closed to when Slotin removed the top reflector.' Also should remove the line, "while Slotin's reaction prevented a recurrence and ended the accident" since there is no source provided saying if it was shut down by thermal expansion if cooling would allow it to restart so at most could currently be described as a precaution but also regarding the phrasing "ended the accident" I don't think you can end an accident any more than you can end a murder, the classification wouldn't change and we still don't have a source in any case. Michaelbaribeau (talk) 19:23, 12 December 2023 (UTC)
thread_title:  Contradicting itself? 

message: It needs to be stated, preferably in the lead section, whether or not there was any possibility of a nuclear explosion in either of these incidents. When I first read "which went briefly critical" I thought it was saying that there was. Later on, when the article talks about "presumably saving the lives of the other men in the laboratory" (i.e. rather than saving the whole of Los Alamos and surrounding area), I began to think probably there wasn't. I think this should be clarified. 86.160.86.232 (talk) 04:20, 4 December 2013 (UTC)
replies: text: He saved them from further irradiation from the core.  It cannot explode in a nuclear sense, that takes careful timing, but it can pre-detonate, that is, get hot enough to melt quite quickly, spatter all over hell and gone, and at that point very likely loose critical geometry, but in the meantime it could irradiate everything within several hundreds of feet, perhaps out to a kilometer very thoroughly, and release limited amounts of fission products.  It could neutron-activate a lot of substances, making the whole area radioactive, just as the bomb does, but without the blast effects.  What it could do depends on dozens of external factors, and is difficult to predict with certainty. SkoreKeep (talk) 08:38, 19 January 2014 (UTC)
thread_title:  Clarification needed 

message: The article is short on details about the core itself. We know that a third core was produced and that it was due to leave Kirtland Field for Tinian on 15 August 1945, and that a fourth was scheduled for September. It therefore seems certain that this core was the one involved in Harry Daghlian's death. Can we find a source for this anywhere? Hawkeye7 (talk) 09:59, 4 April 2014 (UTC)
replies: text: OK, I have a fine source for that history, and I'll write it up today. SkoreKeep (talk) 15:39, 4 April 2014 (UTC)

text: Done. I'm not absolutely sure that the Demon core was the third or the fourth core; I don't know how strict keeping track of the four available hemispheres was at Los Alamos, but there is no indication that it was not. I doubt there were any distinguishing marks on the halves. According to Wellerstein's blog, there is a discrepancy of 1.376 kg in Hanford's and Los Alamos' assays of the shipped amounts (see footnotes on "Third core's revenge" article), and that lead to some investigations, the result unknown.  Mistakes were not unknown. SkoreKeep (talk) 22:38, 4 April 2014 (UTC)
thread_title:  Third Core 

message: The article says that Daghlian was "working alone" when the accident occurred, but then Hemmerly is listed as having also received radiation with no explanation of how/where.  The text should perhaps clarify somehow that Daghlian was the sole person working with the core, but Hemmerly was sitting nearby in the room as a security guard. - Ichneumon~enwiki (talk) 01:18, 15 August 2015 (UTC)
replies: text: Hawkeye7 (talk) 01:37, 15 August 2015 (UTC)

text: Me too.  Simultaneous edits.  SkoreKeep (talk) 01:50, 15 August 2015 (UTC)
thread_title:  Clarification? 

message: Surprisingly FORGIVING despite terminal recklessness by so-called "trained professionals"... kinda shocking how they only did so little damage. The people to feel sorry for are the enlisted guards who were under orders to be present and silently watch as the eggheads messed with lethal things without a second thought.  — Preceding unsigned comment added by 68.231.213.34 (talk) 08:17, 15 November 2015 (UTC)
thread_title:  shoulda been called "lucky" 

message: A recent article by Alex Wellerstein (who as far as I know is a well regarded nuclear historian) claims that the demon core was not used in Operation Crossroads: it had been scheduled to be used, but was still too radioactive by the time of the test and was later melted and used in a new bomb. Since there are cited claims to the contrary already in the article, it would be great if someone with the requisite knowledge in the field could look into this further and make the correction if necessary.
--Doncurzio (talk) 17:58, 22 May 2016 (UTC)
replies: text: Alex is so regarded, and if he says there are records stating such a fate for the core, then that quite likely the latest word on the core's fate. I will edit the article to comply, using Wellerstein's article as the source. SkoreKeep (talk) 19:58, 22 May 2016 (UTC)
replies: text: Agreed. I have also updated the articles on Harry Daghlian and Louis Slotin. Hawkeye7 (talk) 22:29, 22 May 2016 (UTC)

text: See  here for details. Hawkeye7 (talk) 23:44, 15 June 2017 (UTC)
thread_title:  Inaccuracy re: use in Operation Crossroads 

message: -5 cents of reactivity is an amount of reactivity equal to 5% of the delayed neutron fraction. This is pretty small, about 0.03% reactivity. The article mistakenly equates that to 5% reactivity. 5% reactivity is pretty huge ... for example, the NRC requires that the spent fuel pits are kept less reactive than -5%. If the demon core was -5% reactivity it could never have accidentally gone critical just like a spent fuel pit cannot accidentally go critical. 
When I fixed the error, my fix was reverted.
Beprepn (talk) 15:55, 27 February 2019 (UTC)
thread_title:  error in definition of reactivity 

message: Djkinney desires to add a parenthetical comment in the text to let the reader know that the facts of the case are only one historian's opinion.  I object to this on the grounds that while it is one historian's researched opinion on what happened, Wellerstein, very well regarded in this field, has backup from Glen McDuff, another scientist/historian working in the testing history.  Further, there is no alternative theory about where the core went.  The parenthetical comment is true enough, but has no place in this article; in this kind of esoteric field, it's often true that we are working on a single person's memories or logical conclusions.  It represents Djkinney's opinion about the paragraph contents (I presume), and that opinion is uncalled for in the actual article.  The references are there for the reader to draw his own conclusions.
I removed the comment.  SkoreKeep (talk) 17:14, 31 August 2019 (UTC)
thread_title: One historian's opinion 

message: Quote: The demon core was a solid sphere ... It consisted of three parts: two plutonium-gallium hemispheres and a ring
That's a direct contradiction. Was it a solid sphere or two hemispheres? And what's a "ring"? Thanks, Maikel (talk) 10:06, 18 July 2020 (UTC)
replies: text: The core was a solid sphere, as opposed to a hollow one. The grapefruit-sized core consisted of two hemisphere-shaped sections. If you put two hemispheres together, they can slip sideways, so in the middle was a ring with a triangular cross-section which prevented this. Putting the three together created a sphere. There was a small hole in the centre for the polonium-beryllium neutron initiator. The short half-life of polonium-210 (about 138 days) was why the core needed to be capable of being pulled apart.  Hawkeye7 (discuss) 19:14, 18 July 2020 (UTC)
thread_title:  Solid core hemisphere? 

message: The article claims that "Graves was hospitalized for several weeks with severe radiation poisoning and developed chronic neurological and vision problems as a result of the exposure" but I can't find any sources on this. The source provided for this claim does not say this, at all. The source says "After recovery from a six month episode of weakness following
exposure, Case 4 resumed his scientific duties. Except for mild hypertension, which predated the accident, he appeared to have recovered completely from the effects of the exposure." Also, he appeared to have some heart and thyroid problems (unclear if related to the incident) but neither of those are "chronic neurological and vision problems"  — Preceding unsigned comment added by 84.217.48.2 (talk) 15:15, 19 October 2021 (UTC)
thread_title:  Graves' health 

message: The introduction currently states:
: It was involved in two criticality accidents, on August 21, 1945, and May 21, 1946, each of which resulted in a fatality. [... cut unrelated sentence regarding the origin ...] As a result of two separate criticality experiments performed at the Los Alamos Laboratory attempting to show that the core was close to criticality, the device was accidentally placed into a supercritical configuration. As a result, scientists Harry Daghlian and Louis Slotin suffered acute radiation poisoning and died soon after.
So, is that two criticality accidents and another two criticality accidents after the previous ones (total four criticality accidents, four deaths)? That's how the introduction reads to me currently.
Maybe you should move the unrelated sentence a bit up and adjust the wording to fix it? --91.150.22.107 (talk) 12:24, 2 July 2022 (UTC)
thread_title:  confused by the introduction 

message: I would like to raise the question of perhaps adding a "Popular Culture" section to discuss the internet popularity of the incidents. In particular, the recent video by Kyle Hill about his previous video regarding the incident. Would it be feasible to discuss this element while still respecting the integrity of the accident's victims? If so, I would like someone more knowledgeable on the subject to make the edits, as I myself only possess a surface level understanding of the subject.
ZachT1234 (talk) 20:06, 2 August 2022 (UTC)
thread_title:  Possible "Popular Culture" Section in wake of current events 

message: In the Second incident content section, 3rd paragraph is the sentence, "The heating of the core and shells stopped the criticality within seconds of its initiation[15] while Slotin's reaction prevented a recurrence and ended the accident." Saying it was heating is too broad an explanation. In keeping with the actual quote from reference source 15 as well as this additional source, National Academies of Sciences, Engineering, and Medicine. 1995. Management and Disposition of Excess Weapons Plutonium: Reactor-Related Options. Washington, DC: The National Academies Press. https://doi.org/10.17226/4754. https://nap.nationalacademies.org/read/4754/chapter/4#30 and source, Study of the thermal expansion effects of a space nuclear reactor with an integrated honeycomb core design using OpenMC and ANSYS https://www.sciencedirect.com/science/article/abs/pii/S0306454923002207 I recommend updating that part of the sentence to read, 'Thermal expansion reduced the core's density to subcritical stopping the reaction while Slotin's removal of the top shell prevented a possible feedback restarting the reaction.' As for the part about Slotin ending the accident, I don't think one can end an accident, it's like saying one ended a murder, the classification doesn't end. I would just drop that part of the sentence. Michaelbaribeau (talk) 04:46, 8 December 2023 (UTC)
replies: text: My recommended sentence shouldn't use feedback as that term describes a slightly different process but also additional review of the sources already cited show other issues. Source 15 mentions a flash but neither source 15 or 6 says it was blue. Source 6 'implies' removing the shell stopped the radiation calculating exposure by how long the shell was closed but also says in criticality accidents thermal expansion is a shutdown factor. Neither source 15 or 6 mention thermal expansion shutdown would take a few seconds. I recommend the following change, 'Radiation exposure was calculated on the estimated half second the sphere was closed and removal of the top shell prevented the risk of the core going supercritical again.' Michaelbaribeau (talk) 23:05, 11 December 2023 (UTC)
replies: text: I found a related talk post "Contradicting itself?" and made this comment... I started a recent post about this under "The heating of the core and shells" but just saw this post so wanted to respond. Regarding the sentences, "Instantly, there was a flash of blue light and a wave of heat across Slotin's skin; the core had become supercritical, releasing an intense burst of neutron radiation estimated to have lasted about a half second. Slotin quickly twisted his wrist, flipping the top shell to the floor. The heating of the core and shells stopped the criticality within seconds of its initiation." Source 15 an interview by Dr. Schreiber doesn't mention the color blue, that Slotin felt heat on his skin, that it took seconds to stop, or that it was 'heat' that stopped the reaction but instead that, "It was stopped by the expansion of the core and beryllium, but it was enough to put out a lethal shot of radioactivity." You said, "had he not knocked the shell off, it likely would have repeatedly settled back onto the core as it cooled and cycled again" however I don't see a source saying it had opened before Slotin flipped the top reflector. If regarding Schreiber's comment about expansion and assuming the core's size expanded lifting the top reflector ajar but in nuclear reactions thermal expansion usually refers to heating reducing the core density reducing the core to subcritical and this is what it seems Schreiber is referring to. The "half second" line is referring to source 6 the Los Alamos Labs review of criticality incidents, 2000 Revision report, "The results of fission rate calculations in this sphere, as a function of time for several values of excess reactivity, are shown in Figure 43. Figure 44 represents the total number of fissions to be expected as a function of time for the same excess reactivities. These data are applicable to both accidents because the difference in reflector material has only a small effect on the neutron kinetics. In the first excursion, if the excess reactivity did not exceed 15 ¢, the assembly must have been together for several seconds, which is not unreasonable. In the second event, the experimenter was better prepared to disassemble the material, and it is thought that this was done in a fraction of a second, perhaps <1/2 second." I read it to say exposure calculations were based on the estimated half a second it took Slotin to remove the top reflector which 'implies' that is when the reaction stopped. But the reports analysis also says, "The study and understanding of initiating events and shutdown mechanisms associated with criticality accidents offer potential for limiting the frequency and consequences of such untoward events... These programs, which involved solutions of highly enriched uranium, are supplemented by a series of measurements at Los Alamos using the SHEBA assembly. This assembly is fueled with a 5% enriched uranium solution, that provides information on dose rates near excursions in systems of lower enrichment.88 Analysis of data from KEWB and CRAC has led to relatively simple computer codes that follow the early transient behavior well and rely on thermal expansion and the formation of radiolytic gas for the shutdown mechanisms." So this portion seems to say thermal expansion is a factor if not a key cause of such a shutdown. With out more information I think remarks regarding the color blue, that Slotin felt heat on his skin, and that it took seconds to stop, and even what stopped it, and instead use the reports' implied meaning, 'neutron radiation, the exposure of which was calculated based on the estimated half second between when the sphere closed to when Slotin removed the top reflector.' Also should remove the line, "while Slotin's reaction prevented a recurrence and ended the accident" since there is no source provided saying if it was shut down by thermal expansion if cooling would allow it to restart so at most could currently be described as a precaution but also regarding the phrasing "ended the accident" I don't think you can end an accident any more than you can end a murder, the classification wouldn't change and we still don't have a source in any case. Michaelbaribeau (talk) 19:24, 12 December 2023 (UTC)
thread_title:  The heating of the core and shells