RE: Cherenkov radiation [ incl. blue flash and criticality ]

[glen.vickers@exeloncorp.com]

Could it be that the Cesium Chloride salt cristal has scintillative
properties?  Doesn't sound too physically different from NaI.  I wouldn't
think the 662 keV photon would have enough energy to liberate an electron
with enough energy to create Cherenkov.  Of course, I'm not sure what the
speed of light through that medium is either.

Glen Vickers
glen.vickers@exeloncorp.com

> -----Original Message-----
> From:	J. J. Rozental [SMTP:joseroze@netvision.net.il]
> Sent:	Friday, November 17, 2000 10:06 AM
> To:	Multiple recipients of list
> Subject:	Re: Cherenkov radiation [ incl. blue flash and criticality ]
> 
> Dear Jaro,
> 
> In my message it was mentioned a reference about the Cherenkov effect
> detected during the Radiological Accident in Goiania. Research was carried
> out by the Radiation Emergency Assistance Center in Oak Ridge and I would
> like to ask to Dr. Robert Ricks or any colleague  from the REAC/TS to
> comment the research that was made by the REAC/TS .
> Now, about your comment that the tritium exit signs or radium watch dials
> isn't Cherenkov radiation, I do agree, however isn't blue color too, as
> the
> Goiania Accident.
> 
> Jose Julio Rozental
> joseroze@netvision.net.il
> Israel
> 
> 
> 
> ----- Original Message -----
> From: "Franta, Jaroslav" <frantaj@aecl.ca>
> To: "Multiple recipients of list" <radsafe@romulus.ehs.uiuc.edu>
> Sent: Monday, November 13, 2000 7:20 PM
> Subject: RE: Cherenkov radiation [ incl. blue flash and criticality ]
> 
> 
> > J.J. Rozental wrote :
> >
> > On 3 September 1987, a shielded, strongly radioactive caesium-137 source
> > (50.9 TBq, or 1375 Ci, at the time) was removed from its protective
> housing
> > in a teletherapy machine in an abandoned clinic in Goiania, Brazil, and
> > subsequently ruptured. The radioactive source was in the form of cesium
> > chloride salt, which is highly soluble and readily dispersible.
> >
> > After the source capsule was ruptured, the remnants of the source were
> sold
> > for scrap to a junkyard owner. He noticed that the source material
> glowed
> > blue in the dark, and over a period of days friends and relatives come
> and
> > saw the phenomenon, fascinated. Fragments of the source the sizes of
> rice
> > grains were distributed to several families attracted by the
> > glow-in-the-dark radioactive caesium chloride salt ...Thus began one of
> the
> > most serious radiological accidents ever to have occurred.
> >
> > In USA, this Charenkov effect was studied by the REAC/TS Director Robert
> > Ricks.
> > <><><><><><><><><><><><>
> >
> > COMMENT / QUESTION :
> >
> > Perhaps another Radsafer can confirm this, but I very much doubt that
> the
> > glow seen with this cesium source was Cerenkov radiation - just as the
> glow
> > of tritium exit signs or radium watch dials isn't Cerenkov radiation
> either.
> > The obvious observable difference is that the Cerenkov radiation is
> emitted
> > in the surrounding (transparent) medium (such as water), whereas the
> > aforementioned fluorescing objects emit the light directly.
> > I'm no expert, but I believe this has to do with the chemistry of the
> > material -- the pure metal, be it cobalt-60 or cesium137 or a spent fuel
> > rod, does NOT glow, nor does it cause Cerenkov radiation to be emitted
> if
> > its in dry air (for example, in the recent Co-60 incident in Thailand
> there
> > were never any reports of the sources glowing.... in this case an
> > unfortunate lack of a feature that might have acted as warning sign to
> some
> > ! ). But - as already stated by Doug Minnema - we have all seen bright
> > Cerenkov light emitted in pools storing Co-60 sources at food
> irradiation
> > facilities and the like....
> >
> > As for taking photographs of a blue flash (or, no doubt, its absence)
> from
> a
> > criticality in air, I think the key here is an OUTDOOR experiment
> > photographed or filmed from a great distance with a telephoto lens -- as
> I
> > mentioned before, the old Jackass Flats desert tests of nuke rocket
> engines,
> > or outdoor tests of Pu & HEU critical assemblies (for indoor photography
> its
> > possible to use periscope-type arrangements with adequate shielding for
> the
> > camera....)
> >
> > Regarding Arnold Dion's posting saying that,
> >
> > "More to the point, a rerun of the Daghlian accident was performed on
> > October 2, 1945 by Aebersold, Frisch and Slotin. They were not able to
> > see a blue glow in a darkened room in which 6 X 10E15 fissions occurred
> > and the intensity of prompt gammas increased within "several seconds."
> >
> > ....presumably the three who performed the rerun experiment were well
> away
> > and/or shielded from the ionizing radiation, so that the Cerenkov blue
> flash
> > could not form inside their eyes & so they didn't see anything - proving
> the
> > point ( did they use the
> > periscope-type arrangement suggested above ? ).
> >
> > Thank you.
> >
> > Jaro
> > frantaj@aecl.ca
> 
> 
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