Thank you both for your reply.
Your theory of how the event might have happened seems very reasonable -- the only problems with it are that (1) reports from Japan talk of the "blue flash," a sure sign of a "strong" supercritical fission burst (though not necessarily one involving a powerful fluid expulsion), and (2), that a non-burst or oscillating extended duration criticality - such as would be required to "cook up" lots of steam and gases - would have set off radiation alarms all over the plant long before the explosion (or in the unlikely event that there were no alarms anywhere, the radiation dose to the workers from such an extended critical run would likely have been a lot more than 8 Sieverts - they would not have come out alive).
Of course its also possible that the blast that blew the lid off the tank & tore open the roof occurred some time (minutes ? hours ?) after the initial fission burst and after the workers ran away & the plant was evacuated.
We'll just have to wait & see "what the facts is."
By the way Glen, Chernobyl is known to have been caused by a very high yield supercritical fission burst - thousands of times normal operating power over a duration of some milliseconds - although steam/gases also played an important role.
jaro
frantaj@aecl.ca
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Thomas Gleich Harrison[SMTP:tomh@jove.acs.unt.edu] wrote on Friday, October 01, 1999 1:31 AM
Undoubtedly a steam/vapor powered explosion within an enclosed container.
If the Keff was estimated to be approx 1.044 it wouldn't take much of an
expulsion of material from the tank to reduce the Keff to less than one
and kill the fission process, which is probably what has happened.
<snip>
.... if the blast was sufficient to remove a portion of a roof then death would probably result from trauma injuries prior to radiation sickness if the workers
were the same distance from the tank.
The tank cap may be what tore a hole in the roof...
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and Glen Vickers, Gv1@aol.com[SMTP:Gv1@aol.com] wrote on Thursday, September 30, 1999 8:12 PM
The explosion does not sound like a "low-yield burst", but more like a
standard industrial tank explosion. It is more likely caused by a good old
fashion vessel over-pressure caused by gases liberated by heat of the
reaction. I would think that the heated Uranyl Nitrate or steam is the
culprit. I believe the explosion at Chernobyl was caused by steam/H2. As
you mention, [if] the material seems to still be in the tank fissioning, this
would suggest that the source of the explosion was in the void space in the
tank above the material and not within the body of the material itself. I
think that if the blast originated within the material itself, then the
material would indeed be just about everywhere except for the bottom of the
tank.