# Talk:Harry Daghlian

How should the name Daghlian be pronounced? Is the gh silent? Winston.PL 19:17, 6 January 2007 (UTC)

Not that we know he used any Armenian, but in Armenian it's pronounced [hɑɾuˈtʰi̯un kʰɾiˈkʰoɾ dɑʁˈli̯ɑn] (Հարութիւն Գրիգոր Տաղլեան). As far as English is concerned, the MPHPA say it was pronounced 'dolly-an', make of that what you will. – Quoth (talk) 11:52, 13 April 2010 (UTC)

Criticality accidents makes it clear that such incidents do not produce enough thermal energy to raise the temperature of the sphere by much more than 100 degC, so how could it have been hot enough to nearly to melt? A reliable source is needed to back up that statement. Dan100 (Talk) 20:45, 4 October 2007 (UTC)

It doesn't matter what that article says, but what the truth is. Criticality accidents in assemblies like this will result in phase change to liquid or gas if reactivity is sufficiently high. The exact effective multiplication factor necessary to effect this is geometry and material dependent, but Los Alamos's analysis of the Arzamas-16 accident states that reactivity of greater than 120 cents will cause assembly vaporization. The demon core reached at least 100 cents.VmZH88AZQnCjhT40 (talk) 22:41, 19 February 2015 (UTC)

There are several errors in the page if you compare them to other pages that reference the accident (either that or the other pages are wrong).  Brick dropped?  What of the screwdriver?  What was the purpose of the experiment (to cause a nuclear chain reaction?  That's all I can figure out from this page.. which would kill everyone).
In any case there isn't enough information on this page that can be shown to be correct or even match up with other pages.  —Preceding unsigned comment added by Cs302b (talk • contribs) 09:49, 17 October 2007 (UTC) 

(I removed leading spaces from your question above) The screwdriver was used by Louis Slotin, not Daghlian. Could you list the errors? The source for the brick is in the Los Alamos reference la-1368.pdf page 74, which I quote in its entirety:

In the first accident, a critical assembly was being
created by hand stacking 4.4 kg tungsten carbide bricks
around the plutonium core. Figure 41 shows a reenactment*
of the configuration with about half of the
tungsten blocks in place. The lone experimenter was
moving the final brick over the assembly for a total
reflector of 236 kg when he noticed from the nearby
neutron counters that the addition of this brick would
make the assembly supercritical. As he withdrew his
hand, the brick slipped and fell onto the center of the
assembly, adding sufficient reflection to make the
system superprompt critical. A power excursion occurred.
He quickly pushed off the final brick and
proceeded to unstack the assembly. His dose was
estimated as 510 rem from a yield of 1016 fissions. He
died 28 days later.
An Army guard assigned to the building, but not
helping with the experiment, received a radiation dose of
approximately 50 rem. The nickel canning on the
plutonium core did not rupture.

On October 6th I reviewed this article against the above source and the tripod dedication website external link and I only changed the image caption to remove "simulated". I did notice minor discrepancies and claims without cites:
Los Alamos document states Harry died "28 days later", but other sources indicate 26 days.
As it stands, the article provides the date of the incident, the date of death, and the interval between them. These are inconsistent, so at least one is wrong and should be corrected. But which? PMLawrence (talk) 10:47, 17 December 2009 (UTC)
The tripod site, while quite believable generally, describes the three assembly attempts in a way that does not make sense from geometrical considerations. I was unable to follow the reading list (amazon books for sale) to track down the source.
I agreed with the call for citation for the near melting of the sphere claim since I found no source, only inconclusive estimates, look at "Re: fission question" posts in this 2004 thread for example. That thread also reconstructs the geometry of the assembly in a way better than the photograph, which shows a half-finished assembly.
If anyone has more sources please add them in the article, or here in Talk.
IANAP, but the answer your question as to the purpose of the experiment appears to be Los Alamos needed to know the size of the reflector needed around that core to make it just sub-critical (and not actually critical) so that when assembled in a bomb (of the Fatman design) it would remain subcritical (and not undergo a power excursion which would ruin the core, but note, not cause an explosion, IMO). The tech-archive.net thread I linked above has semi-technical talk on this. -Wikianon 15:26, 17 October 2007 (UTC)
Ok, I still see a couple of errors that are less severe now that you've explained them.. One being the description of the pieces that were being put together.  Another being whether or not the experiment was condoned by Los Alamos (in one of the two articles, sorry I only have a moment right now and can't search, it says the experiment was done late at night to avoid rules.  And in any case, has there been any explanation as to why several high ranking scientists didn't realize that standing in the room poking it with a screwdriver and not.. oh.. a few miles away from such an test might be a good idea?  I mean, seeing how close they can get it to going critical without doing it. It doesn't take an advanced physics degr... oh.
Not that that last one was on the fault of wikipedia, I havn't seen ANY explanation to this.
-cs302b  —Preceding comment was added at 04:17, 18 October 2007 (UTC) 

I, too, recall reading that it was an unauthorized experiment done at night. As for the reason these things were done by hand, this was pre-waldo days, without precise electronic control. Doing this any other way then by hand would have been a pain, and unmacho, and apparently Louis Slotin, among others, opposed the idea when it was brought up after Daghlian's death. (After Slotin's death, doing things remotely became policy.)--Prosfilaes (talk) 23:59, 30 April 2010 (UTC)

The article refers to the core going 'prompt critical' and the reference cited states 'super prompt critical' however the link to prompt critical states that it is a special case  of super criticality occurring over microseconds and resulting in explosive disassembly. This does not seem to have occurred.
Is the term 'prompt critical' incorrect or is the linked definition incorrect?  —Preceding unsigned comment added by 203.31.40.71 (talk) 02:44, 28 January 2008 (UTC) 

"Prompt critical" means critical on the basis of prompt_neutrons alone.  "Super critical" means more than critical.  Since the total neutron production is formed by prompt neutrons plus delayed neutrons, a prompt critical assembly is by definition super critical when delayed neutrons are added.  The prompt critical link is a bit overstated when it comes to explosive disassembly in microseconds, but the time constant for neutron multiplication is correct.  JohnAspinall (talk) 00:51, 30 April 2008 (UTC)
The reference states that the assembly was "superprompt critical." This is a technical term which specifically means that the assembly is supercritical on prompt neutrons alone. Reactivity significantly in excess of prompt criticality is necessary to cause fuel vaporization (~>1.2 times prompt criticality). See LA-13600. Just because a nuclear power reactor would be destroyed by a prompt criticality doesn't mean a bare sphere would. VmZH88AZQnCjhT40 (talk) 22:57, 19 February 2015 (UTC)

If he was working alone, how is it possible for anyone to describe the accident in detail? "As he was moving the final brick over the assembly, neutron counters alerted Daghlian to the fact that the addition of this brick would render the system supercritical. As he withdrew his hand, he accidentally dropped the brick onto the center of the assembly." Then, we are told that he panicked. Next, we know exactly what he did after he panicked. All of this must be the result of rational inference, but it is not a certain description of the actual events. How could it be?Lestrade (talk) 00:59, 11 December 2009 (UTC)Lestrade

Presumably they got a full debrief report from Daghlian ASAP after the accident. He would have been conscious and (at least for some hours) not even in much pain. Then his hands would have started to swell and hurt, he'd have had nausea, and so on. SBHarris 02:44, 11 December 2009 (UTC)
I had assumed that he would have been incapacitated or incommunicable after the accident.Lestrade (talk) 17:45, 11 December 2009 (UTC)Lestrade

Oh, no, not after a whole body dose of 5 gray. That's barely 50% fatality level (he would probably have survived today). It takes doses of 80 Gy or 16 times that dose to incapacitate soldiers from CNS-swelling effects, in a few hours, as (for example) with a "neutron bomb." Daghlian should have had little more than nausea, diarrhea, and some hand pain for at least several days, and been completely coherent otherwise (if somewhat anxious, knowing he had a good chance of eventually dying from infection and bleeding as his bone marrow failed). SBHarris 02:41, 12 December 2009 (UTC)

This review is transcluded from Talk:Harry K. Daghlian, Jr./GA1. The edit link for this section can be used to add comments to the review.
Reviewer: Ian Rose (talk · contribs) 09:40, 7 August 2015 (UTC)
Actually heard of this poor fella, should be able to review this w/e. Cheers, Ian Rose (talk) 09:40, 7 August 2015 (UTC)

Apologies for not getting to this sooner...
Toolbox checks -- no dab or EL issues.
Prose/structure/detail -- split longish first sentence, no other issues I could see.
Images -- licensing looks fine.
Referencing

I'd have expected his birth date to mentioned/cited in the Early life section.
 Done Added. Hawkeye7 (talk) 10:10, 16 August 2015 (UTC)
Would Dion really be considered an RS?
According to source 7, he was "an adjunct professor of bioscience and biotechnology at Drexel University, Philadelphia, [who] has spent four years gathering information on early nuclear fatalities". I've replaced all the Dion footnotes with other sources, but left it as footnote 10 so readers can see images of the memorial and the ceremony. Hawkeye7 (talk) 10:10, 16 August 2015 (UTC)
Okay, checked everything added since I last looked at it and happy to pass as GA. Cheers, Ian Rose (talk) 11:58, 16 August 2015 (UTC)
Cheers, Ian Rose (talk) 06:39, 16 August 2015 (UTC)


### Postscript
Thanks for the close, BD2412.  The original move (here) had nothing unusual about it, and was several days after the close of the RFC and revision of WP:JR that said no-comma is preferred, so I'm wondering why you added "Whether the move was correct as a matter of process in the first place" to your closing statement.  As far as I know, I did nothing questionable there.  Let me know if you see an issue, otherwise I'll consider it water under the bridge.  Thanks again. Dicklyon (talk) 01:24, 22 April 2016 (UTC)

I only meant to underscore that irrespective of the original state of the page, there is a clear consensus for the title sans comma. bd2412 T 02:24, 22 April 2016 (UTC)
Cool.  Thanks.  Dicklyon (talk) 02:50, 22 April 2016 (UTC)

This may not be the right place but what I'm wondering about is what specifically this early criticality experiment sought to find out.
In a "normal" quantitative science experiment, what you do is keep all parameters constant except one, which you vary in order to obtain different results. These results then make it possible to arrive at formulas or algorithms to describe the interrelations between the different parameters.
For example, a simple experiment about the electrical conductivity of liquid solutions would be to dip two electrodes into a sample solution, apply a current and measure the voltage. In a series of experiments you could then vary the distance between the electrodes, or the concentration of the solution, or the current, or the voltage etc, and even do multiple series for different electrolytes to compare those to each other, and arrive at the specific conductivity of given electrolytes.
Now it is clear that in the criticality experiment, they measured neutron flux. But the variable parameter in the Daghlian experiment seems to have been the "number of reflector blocks" which seems oddly undspecific; the results would seem to be applicable only to his sepcific experimental set-up. Cancun (talk) 12:10, 23 November 2021 (UTC)