Talk:Harry K. Daghlian, Jr.

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

[edit] "Enough to melt the sphere"

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)

[edit] errors

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.
  • 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)

[edit] prompt critical ?

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)