RE: Deadly Plutonium ?

["Bradshaw, Keith" <Keith.Bradshaw@nnc.co.uk>]

> What I find interesting is the belief that an alpha particle from
> Plutonium
> is much more hazardous than an alpha particle from Uranium.  If you
> compare
> the ALI in 10CFR20 you only get a factor of about 12 between Pu and U with
> Pu being the lower value.  The news article states that there might have
> been as much as 328 grams of Pu present in 89,000 metric tons of Uranium
> feed.  When you do the specific activity conversions for Pu and U you get
> about 328 Ci of Pu (conservative estimate based on the isotopic
> distribution
> on recycle Pu rather than weapons grade Pu) and 63,000 Ci of Uranium
> (natural Isotopic).  No matter how I look at it I can not see how the Pu
> contribution would dominate the internal health effects.
> 
	<CUT>

	Just thought I'd share some ideas on this:

	About a year ago we had a discussion on RADSAFE about DU and what
else it might contain (other than 238/235/234U).  About that time I did some
calculations which I have just found again.

	When you take into account the dose coefficients for INHALATION of
insoluble species and for members of the public,  by my reckoning it takes
only approx. 1ppm by mass of Pu-239 in DU to double its overall Sv/Bq rating
and hence reduce its DAC by a factor of 2. The presence of 238 and 240-Pu
(which is usual in civil Pu) would give a figure below 1ppm because of their
greater alpha activity per unit mass.

	Nat-U has about 1.7 times the U alpha activity of DU (of Rand Report
isotopic composition) so about 1.7ppm of Pu-239 in nat-U would approximately
double the radiological hazard weight for weight.

	(These are my own back-of-envelope calculations and have not been
verified by anyone else).

	Regards

	keith.bradshaw@nnc.co.uk











	END


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