bill22-ga.
Man, you ask some tough, intense questions.
Radioactivity is a very tricky topic since it's hard to make
meaningful measurements...there are many different types of
radioactivity, and not all are alike in terms of their energy
intensities, or potential effects.
Nonetheless, concerns over radionuclide emissions from power plants
have led to some study and benchmarking of radioactive emissions, and
I have summarized these here.
In a nutshell, though, there appears to be very little concern over
this topic. Not because there isn't a lot of radioactive material
naturally present in coal (on the contrary, there's quite a bit!), but
because most of the radioactive materials are captured by pollution
control devices in the US, and do not end up as direct atmospheric
emissions.
Most....but not all. The US Environmental Protection Agency conducted
what is considered the definitive study on this topic in 1998:
http://www.epa.gov/ttn/caaa/t3/reports/eurtc1.pdf
Study of Hazardous Air Pollutant Emissions from Electric Utility Steam
Generating Units -- Final Report to Congress
This is a 500-page report with several tons of detail, but one table,
in particular has the key details you asked about. Table 9-3 (on page
330) gives the radionuclide emissions in units of miliCuries per
billion KWh of electric generation. Check the report itself for the
full details of the table, but I've excerpted some of the key emitters
below:
Table 9-3. Average Annual Radionuclide Emissions per Operating
Boiler Unit and per Billion Kilowatt-Hour Electricity Generated
Radionuclide............................mCi/billion KWh
Rn-220......................................1.1 x 10^2 = 110
Rn-222......................................2.0 x 10^2 = 220
U-238........................................1.5 x 10^0 = 1.5
U-234........................................1.5 x 10^0 = 1.5
Ra-226......................................1.2 x 10^0 = 1.2
Po-218......................................3.8 x 10^0 = 3.8
Pb-214......................................3.8 x 10^0 = 3.8
Po-214.....................................3.8 x 10^0 = 3.8
Pb-210.....................................3.8 x 10^0 = 3.8
Po-210.....................................3.8 x 10^0 = 3.8
Po-216.....................................2.4 x 10^0 = 2.4
Pb-212.....................................2.4 x 10^0 = 2.4
K-40........................................5.3 x 10^0 = 5.3
The biggest emission source of radioactivity comes from Radon
isotopes, which collectively (Rn-220 + Rn-222) account for 330 mCi for
every billion KWh of electricity generated.
No other radionuclide makes much of a contribution, adding only about
another 30 mCi all told, with K-40, and isotopes of lead and polonium
accounting for most of the remainder.
You mentioned uranium and thorium in your question, but by themselves,
they are fairly minor emission sources. Instead, they decompose, and
their breakdown products are the key emitters.
The total radiation from air emissions at coal fired power plants, on
average, is about 360 mCi per billion KWH.
Since you asked about BTUs as well as KWh, we can convert using the
conversion factors found here:
http://www.uwsp.edu/CNR/wcee/keep/Mod1/Whatis/energyresourcetables.htm
1 kilowatt hour of electricity = 3413 BTUs
Hence, there is an average of 360 mCi per 3.413 trillion BTUs, or
approximately 105 mCi per trillion BTUs.
I hope that fully answers your question.
However if there's anything else you need, here, just let us know (my
son, James, helped me out on this one, and we're both at your service
should you need anything else).
All the best,
pafalafa-ga and james
search strategy -- Used my knowledge of the issue to search the EPA
website for [ radionuclides coal power plants emissions ] |
Clarification of Answer by
pafalafa-ga
on
08 Nov 2006 08:48 PST
bill22-ga,
After conducting a fair amount of additional research, I can say with
some confidence that there does not seems to be a ready source of
information on radiation emissions from coal-fired powered plants in
developing countries.
In general, the impacts from more conventional pollutants
(particulates, sulfur dioxide, and so on) are so overwhelming --
especially from plants without adequate pollution control equipment --
that little attention has been paid to radioactive releases.
Most observers seem to agree that overall radioactivity from coal
power plants is rather small, and a minor contribution compared to
radiation from other sources. The concerns that do arise have to do
with the use of power plant fly ash as a building material -- the fly
ash concentrates some of the radioactive elements in the coal, and its
use in buildings can then create a sustained low-level exposure. An
example of one such study in a developing country is here:
http://ibe.sagepub.com/cgi/reprint/15/2/187.pdf
Radon Dosimetry in Typical Indian Dwellings Using Plastic Track Detectors
As for air emssions, though, I could find no compelling research.
One observation that may be useful, however, is that modern pollution
controls on coal-fired power plants are generally 99.5 - 99.9%
efficient in removing particles. As a rule of thumb, then, we can
estimate that uncontrolled emissions would generally be anywhere from
100 to 1,000 times greater than controlled emissions.
Using that rule of thumb as a guide, then, the figures that I provided
in my original answer can be increased by a factor of 100 and 1,000 to
provide a range of estimates for releases from a coal-fired plant with
little or no pollution control:
Radionuclide................................mCi/billion KWh
Rn-220...................................... 11,000 - 110,000
Rn-222...................................... 22,000 - 220,000
U-238....................................... 150 - 1,500
U-234...................................... 150 - 1,500
Ra-226...................................... 120 - 1,200
Po-218...................................... 380 - 3,800
Pb-214...................................... 380 - 3,800
Po-214..................................... 380 - 3,800
Pb-210..................................... 380 - 3,800
Po-210..................................... 380 - 3,800
Po-216..................................... 240 - 2,400
Pb-212..................................... 240 - 2,400
K-40........................................ 530 - 5,300
Two other useful resources that you might want to look over are these:
http://www.ornl.gov/info/ornlreview/rev26-34/text/colmain.html
Coal Combustion
http://greenwood.cr.usgs.gov/energy/factshts/163-97/FS-163-97.html
Radioactive Elements in Coal and Fly Ash: Abundance, Forms, and
Environmental Significance
I hope this additional information, even as a rough estimate, is
useful to you in your work.
If there's anything else I can do for you on this, don't hesitate to let me know.
All the best,
paf
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Clarification of Answer by
pafalafa-ga
on
29 Nov 2006 18:42 PST
Bill,
Thanks so much, for so many things, including your collection of
challenging questions, your clarity, and your generosity.
Yes, Google Answers will be missed by many. And even though you've
broken the rules by posting a contact address, I'm guessing it will
serve you well just the same.
Perhaps other customers will be tempted to do the same. They
shouldn't, of course, but....
All the best to you in the holiday season and the new year coming...
David Sarokin
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