RE: Plasma Torch Cutting

["NIXON, Grant (Kanata)" <GNIXON@MDS.Nordion.com>]

I do not have much to offer other than to say that I believe that there are

a number of graphite-moderated reactors in the US, none of which are of the

same design or hazard as Chernobyl.



Go to the IAEA website. It contains a list of each type of reactor currently

in use in the world.



http://www.iaea.org/programmes/a2/  





Best regards,



Grant

-----Original Message-----

From: Flanigan, Floyd [mailto:Floyd.Flanigan@nmcco.com]

Sent: Friday, August 15, 2003 9:23 AM

To: Franz Schoenhofer; NIXON, Grant (Kanata); Dave Biela;

radsafe@list.vanderbilt.edu

Subject: RE: Plasma Torch Cutting





Forgivr me if this is a bit off thread, but something in your reply brought

up a question. To what extent are graphite modeartors still used in

reactors, ala Chernobyl Nuclear Power Plant? I'm sure I could get the

numbers if I looked hard enough, but I'm asking on the off chance someone

already has done the leg-work.

Floyd W. Flanigan B.S.Nuc.H.P.



-----Original Message-----

From: Franz Schoenhofer [mailto:franz.schoenhofer@CHELLO.AT]

Sent: Thursday, August 14, 2003 3:48 PM

To: NIXON, Grant (Kanata); 'Dave Biela'; radsafe@list.vanderbilt.edu

Subject: AW: Plasma Torch Cutting









-----Ursprüngliche Nachricht-----

Von: owner-radsafe@list.vanderbilt.edu

[mailto:owner-radsafe@list.vanderbilt.edu]Im Auftrag von NIXON, Grant

(Kanata)

Gesendet: Mittwoch, 13. August 2003 23:45

An: 'Dave Biela'; radsafe@list.vanderbilt.edu

Betreff: RE: Plasma Torch Cutting







Dear Dave,



(1) Chemistry: You are non-specific on the type of contamination on the

surface. But this item is important in order to understand the possible

chemical reactions that can take place.



As an example, C-14 contamination in an oxygen-rich environment (air) (+

heat) would prove a much different sort of radiological hazard (e.g., via CO

and CO2 formation) than would, say, Cs-137 contamination.



(2) The physics describing the release of contaminants or other particles

adhered to surfaces due to heating is a fairly well-known subject (adhesion

w.r.t. volatiles). This is a surface physics item that ought to be familiar

to semiconductor and optics people.



------------------------------------------------------



Dave,



Unfortunately I cannot give you a straight answer, but only a few hints.



A contamination by C-14 will be a very low radiological hazard, because both

CO and CO2 are gaseous and will be diluted extremely fast. A very small

fraction will be absorbed in the lung, but I guess that most of those gases

will be immediately exhaled. In any case the radiotoxicity of C-14 is very

low.



Cs-137 (or rather Cesium-compounds) are volatile above a temperature of

about 450 C, so they will volatilize at the heat of a plasma torch. The same

is true for quite a few other radionuclides. You may take as a guide the

emissions from the Chernobyl Nuclear Power Plant, which were caused not only

by the explosion and the meltdown of nuclear fuel, but mostly because of the

graphite burning for about 10 days.



I agree, that the type of contamination will of most importance, but you

have to consider the radiotoxicity of radionuclides as well.



Franz





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