Re: radioactivity from fossil fuel power stations

[BERNARD L COHEN <blc+@PITT.EDU>]

	My treatment of the radiation exposures from coal burning, given

in HEALTH PHYSICS 40:19;1981, adds up effects over hundreds of thousands

or millions of years -- very near future doses are negligible by

comparison. Radon administers dose by percolating up thru the ground from

roughly the top one meter, so that top meter is what we are concerned

with. The ground surface erodes away at a rate of about one meter per

20,000 years, so all material in the ground will eventually spend about

20,000 years in this top meter, administering doses from radon which is

killing, according to NCRP, ICRP, etc, about 15,000 Americans every year.

If you figure out how much uranium is in the top meter of U.S. soil, and

consider the fact that it kills 15,000 people per year for 20,000 years,

this works out to be 3.7 deaths per ton of uranium before it is eroded

away into the oceans. This toll will eventually be taken by every ton of

uranium in the ground. For example, when coal is burned to generate

electricity, the uranium (+Th + Ra) released from impurities in the coal

(average 1 ppm) will kill 11 people per GWe-year, with these deaths

occurring over the next 100,000 years. That is the "short term" effect.

>From the longer term perspective, if the coal had not been mined it would

eventually reach the top meter of the ground -- if it came from 100 meters

deep, this would occur after 100 x 20,000 = 2 million years. During its

20,000 years in the top meter, the carbon in the coal would produce no

radon, but if the coal had been mined out, in the 20,000 years during

which it would have been in the top one meter, it is replaced by average

rock which does contain uranium (2.7 ppm) and thus releases radon. This

extra uranium (+Th +Ra) causes 30 deaths per GWe-year. To calculate this,

coal burning consumes 3 E6 tons/ GWe-year so the extra uranium producing

radon is 3 E6 x 2.7 E-6 = 8.1 tons of uranium; with 3.7 deaths per ton of

uranium, this gives 8.1 x 3.7 = 30 deaths.

	Note that mining uranium out of the ground to produce nuclear

electricity - 160 tons / GWe-year - *saves* 160 x 3.7 = 590 lives per

GWe-year. With a correction for mill tailings, this is reduced to 420

lives saved.

	If you object to this treatment because we shouldn't be worried

about deaths millions of years in the future, note that this was not my

idea to do so -- that is what the anti-nukes insist on. Similarly for my

use of linear-no threshold theory in the calculation. my viewpoint on

these matters is expressed in my paper on "Discounting in assessment of

future radiation risks", HEALTH PHYSICS 45:687ff;1983. 

	 

	



Bernard L. Cohen

Physics Dept.

University of Pittsburgh

Pittsburgh, PA 15260

Tel: (412)624-9245

Fax: (412)624-9163

e-mail: blc+@pitt.edu





On Fri, 3 Aug 2001, Susan Gawarecki wrote:



> Technically, once the coal is gone and burned, nothing "replaces" it in

> the ground.  For strip mines, the landscape is permanently altered

> because material is missing.  For subsurface mines, voids remain that

> may fill with water or that may collapse causing subsidence at the

> surface.

> 

> I doubt that an area mined for coal would then become a higher radon

> source.  In fact, that coal itself contains uranium and thorium means

> that coal is at least a minor radon source.  Most important rock types

> for radon are granites, phosphates, and various sedimentary rocks (such

> as shales, sandstones, and limestones) that have become somewhat

> enriched in radionuclides via exposure to uranium-bearing groundwater

> (generally due to a significant organic content which seems to

> preferentially capture uranium).

> 

> Only if the other rock types associated with coal have relatively high

> uranium contents, and these are fractured or exposed to the extent that

> trapped radon is released, might your argument hold much weight.  These

> negative effects are probably negligable compared to the acidification

> of groundwater and surface water caused by the exposure of the iron

> sulfides commonly associated with coal.

> 

> Regards,

> Susan

> 

> Bernard L Cohen wrote:

> > 

> > On Fri, 3 Aug 2001, Susan Gawarecki wrote:

> > 

> > > Dr. Cohen,

> > >

> > > I'm a geologist, but I don't understand what you mean by this statement:

> > >

> > > > When coal is mined out of the ground and

> > > > made to "disappear" as carbon dioxide, its carbon is replaced in the

> > > > ground by other rock which contains U, Th, Ra.....

> > 

> >         -- My statement here is a simplification of a much more

> > complicated analysis, given in the paper cited, but I will try.

> >         When the carbon in the coal is burned, it disappears from the

> > ground. The volume of the ground that it occupied is then taken by other

> > rock or soil which contains uranium, and therefore eventually serves as a

> > source of radon. The carbon in the coal cannot serve as a source of radon.

> > The uranium impurity in the coal is returned to the ground eventually.

> >         In other words, the carbon in the coal takes up a volume in the

> > ground which produces no radon, while the rock that takes up that volume

> > when the coal is removed does produce radon.

> 

> -- 

> .....................................................

> Susan L. Gawarecki, Ph.D., Executive Director

> Oak Ridge Reservation Local Oversight Committee

>                        -----                       

> A schedule of meetings on DOE issues is posted on our Web site

> http://www.local-oversight.org/meetings.html - E-mail loc@icx.net

> .....................................................

> 



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