From: ken@sugra.uucp (Kenneth Ng)
Newsgroups: sci.environment
Subject: Re: Is nuclear energy "polluting"? (was Re: Is car pooling for real?
Date: 29 Jul 92 05:08:57 GMT
Organization: Private Computer, Totowa NJ

In article <131128@lll-winken.LLNL.GOV>, shaw@s119.es.llnl.gov (Henry Shaw 510 423-4645) writes:
:In article <1992Jul21.042941.2278@sugra.uucp>, ken@sugra.uucp (Kenneth Ng) writes:
:|> In the research I have done on the toxicity of nuclear waste, it seems that
:|> the waste is less toxic than the ore it comes from in between 300 and 1200
:|>years, depending on how you measure toxicity (its a lot more complicated than
:|> you would think).  Therefore, I've often said to some of my environmentalist
:|> friends that nuclear power is really cleaning up the planet on a long
:|> term basis :-).
:This is incorrect.  For unreprocessed spent fuel, the toxicity does not fall
:below that of the original ore until approximately 3,000,000 years after
:discharge, according to the latest ICRP evaluations (ICRP-46).  For a nuclear
:fuel cycle that includes reprocessing to extract the fissionable actinides,
:followed by "burning" of these elements in reactors, the toxicity curves for
:the ore and the reprocessing waste cross at about 20,000 years.  These values
:have increased significantly from the ICRP's previous assessments.

Fascinating, someone else who actually reads these reports (and hopefully
understands them better than I do, you didn't think I was an expert at nuclear
energy did you?).  Did the ICRP reports also indicate what was wrong with
the previous models?  Different outcomes in the actinides in reprocessing?
Did the older models assume removal of Stronium 90 for other uses?  Did the
older simulations only consider fission products?  I am not questioning the
numbers (yet), I'm just trying to find out the causes of the discrepencies,
which is the first thing I need resolved when seeing new numbers.

By the way, I do have one request of you, PLEASE set the word wrap to 80
characters or so.  Some day we may have automated mechanisms to reformat
text to whatever window we have, but until then, reliance on antiquated
standards is generally the best thing.

My most recent material on nuclear waste is "Geology of High-Level Nuclear
Waste Disposal" by I.S. Roxburgh, 1987, ISBN 0-412-29910-0.  It appears to
be a rather thorough book, even though I admit that parts go straight over
my head.  Hm, going through this book, it looks like I quoted the wrong
number for the high end.  The graph it looks like I quoted from has a decay
time of between 1K and 10K years for the number of curies to come down
to that of ore (don't ya love log scales?).  (Original reference Ewart, F.T.
"Fuel Inventories and Derived Parameters for the Reactor Systems CDFR,
LWR, AGR and Magnox.  Report AERER-R10037.)  The correct graph appears
to be on page 29.  It estimates 10K to 100K years (again a log graph)
to return to the toxicity of 0.17% uranium ore.  (Original reference is
Hamstra, J. and Van der Feer, Y 1981, "New ICRP norms and underground
disposal of radioactive wastes".  Energie Spectrum, 81, 4, I have not
read it, its in Dutch.).  Looking at the graph is especially interesting.
Sn90 and Cs137 appear to dominate toxicity for the first 100-1000 years,
and then they practically disappear off the graph (must be the effects of
the log scale).  After that Am241 and Am243 keep the toxicity over that
of Uranium ore until the 10K to 100K crossover.  Could this have been
what was missing from the older estimations?

:In any case, toxicity is a poor measure of the risks associated with nuclear
:waste.  It grossly overestimates the actual risks by assuming that the waste
:is totally dissolved in water, which is then consumed by someone.

I agree totally.  Toxicity is a function of the element, what compound it
becomes, the intake method (ingestion, inhalation), the concentration, the
presence of other elements (often element B can increase or decrease the
toxicity of element A, according to "The Toxicology of Inorganic Substances",
I forgot the author), and a myraid of other factors.  Its only real use is
in absolute comparisions, like the chlorine in a city waterworks could
theoritically kill X thousand people if everyone stands in line and inhales
the proper dosage and then takes no corrective action like exhaling.

:References:
[edit]

Some people have asked me where I got my numbers, a few have accused me
of making them up.  Here are some of the ones I could find just by
scanning my library:

"Nuclear Waste Disposal: Is There a Safe Solution?" Civil Engineering, ASCE
May 1979, page 78.  Values given are: ~1K years for recycled wastes, ~20K
years for spent fuel.

"The Fight Over Nuclear Power" by Fred Schmidt and David Bodansky, page 69.
Value given here is 300 years.

"The Nuclear Energy Option" by Benard L. Cohen 1990, page 181.  Yet another
log graph shows about 10K years.

Now, does anyone here have access to the databases that are used to generate
these graphs?  I'd like to see the effects of removing the stronium 90
component, since these element could be used for a literally uninterruptable
power source.

-- 
Kenneth Ng
Please reply to kdn5669@hertz.njit.edu for now.
AT&T and Apple: Just say NO!
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