From: dpe@inel.gov (Don Palmrose)
Subject: Re: Notch another one up for the Greennazis
Organization: INEL EG&G Idaho
Date: Wed, 23 Dec 92 15:06:06 GMT

In article <1992Dec23.030636.6041@sugra.uucp>, ken@sugra.uucp (Kenneth Ng) writes:
>
 
> I assumed the 0.5 nanogram value was a realistic value to kill a person.  I
> then figured out how frequent one would encounter such particles.  Since the
> number was rather frequent, I surmised either: we are all dead and don't
> realize it, my modeling has some rather significant errors (and I am still
> not ruling them out, and I encourage those really interested in doing the
> math more accurately and post the numbers), or the original assumption is
> incorrect.  What I did not try to evaluate is the true lethality of
> plutonium.
> 
> :Pu is easily detected by its characteristic gamma energy -
> 
> Plutonium is mostly an alpha and beta emitter.  However, I do note in the
> CRC, there is an entry on the far right hand side indicating gamma energy
> intensity.  The legend says something about annialiation with positrons,
> but I'm not sure exactly what that is and when it is prevalent.
> 
> -- 
> Kenneth Ng
> Please reply to ken@eies2.njit.edu for now.
> Apple and AT&T lawsuits: Just say NO!
> 
> 

Your assumption of 0.5 nanograms of Pu in killing someone is your mistake.
I am looking at page 208 of the Radiolgical Health Handbook and it gives a 
maximum permissible concentration in air for a 168 hr week exposure of 1.0e-11
microcuries per cubic centimeter.  This could well be where the 0.5 nanograms
comes from (I do not have time to go through the math but it is not difficult).
HOWEVER, the maximum permissible concentration is a limit not to exceed **to 
guarantee no damage** and NOT a value that will guarantee death.

I have not been able to find any value of either inhalation or ingestion of
Pu that will guarantee death even within a certain period of time of several
years.

As for decaying, it will give off positrons.  This will eventually make 
contact with an electron, annialating each other leaving behind two 0.511 MeV
gamma rays.  It is a well known characteristic of decay by positron emission.
However, many other radionuclides decay by positron emission.  Pu can give off
regular gamma rays but the percentage of total number of decays is very small
(less than 1.0e-2 %, yes %).  So Pu could be determined by these gamma ray
emissions, but it may take the counting equipment a long time to get enough
data points for that determination.

Hope this helps.

Don Palmrose






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