Re: A real solution

["Jerry Cohen" <jjcohen@prodigy.net>]

I believe I am the one who is responsible/guilty ( U pick) for  deriving
sets of curves relating the ingestion radiotoxicity  and/or chemical
toxicity of spent fuel as a function of decay time. This was part of a
project for DOE and related to the Yucca Mountain project. It was intended
to address the question of when a nuclear waste repository becomes less
hazardous than a undisturbed uranium ore deposit.The study was done during
the early 1980's. I found the curves in my old files and can summarize them
as follows: [1] Using ICRP-2 data
(I told you these were old), spent fuel (33,000 MWD burnup) does indeed
become less toxic than uranium ore in ~300 yr, [2] using ICRP-30 data, it
takes about 10,000 years, and [3] with ICRP-48 data it becomes more like
~100,000years. Another interesting relationship that we calculated in this
study assumed that at time zero we had 1.0 Kilogram of natural uranium and
had a choice of either fissioning every atom to produce nuclear power, or we
could leave it alone let it decay "naturally". We followed the toxicity
index of this one kilogram of material ,i.e. fission products vs natural
decay products ( considering both radio and chem toxicity- the stable end
product of natural decay being mostly toxic lead) and found a crossover at
about one million years. In other words, if you wait long enough, the world
becomes toxic as a result of nuclear power production. But who cares!


-----Original Message-----
From: Michael McNaughton <mcnaught@lanl.gov>
To: Multiple recipients of list <radsafe@romulus.ehs.uiuc.edu>
Date: Friday, August 18, 2000 2:37 PM
Subject: Re: A real solution


>At 02:54 PM 8/18/00 -0500, you wrote:
>>Some years ago I was told by someone whose opinions I respect that the
>>oft-used 10,000 year worry period is way off and that spent fuel will
decay
>>to being no more radioactive than the original unirradiated fuel in about
>>300 years.
>
>I have seen this presented as a graph, but with essentially no
>justification, no references, and no technical details. The graph is
>"ingestion toxicity" versus time; Pu is assigned a low ingestion toxicity
>because it is insoluble. After almost 1000 years, the total ingestion
>toxicity of the high-level waste from a LWR is shown as less than the total
>ingestion toxicity of the original uranium ore used to make that fuel. Many
>years ago I tried and failed to find the origin of the graph so I could
>check the details.
>
>mike
>
>Mike McNaughton
>email: mcnaught@LANL.gov or mcnaughton@LANL.gov
>phone: (505)667-6130
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