[ RadSafe ] RE : Spent fuel and decay
Jerry Cohen
jjcohen at prodigy.net
Thu Jul 26 17:54:23 CDT 2007
I believe the code you refer to is ORIGEN. It comes from ORNL.
----- Original Message -----
From: "John R Johnson" <idias at interchange.ubc.ca>
To: "Jim Hardeman" <Jim_Hardeman at dnr.state.ga.us>; "Mike (DOH) Brennan"
<Mike.Brennan at DOH.WA.GOV>; <radsafe at radlab.nl>
Sent: Thursday, July 26, 2007 3:31 PM
Subject: Re: [ RadSafe ] RE : Spent fuel and decay
> Jim and Mike
>
> I knowl that there was a computer program that gave the isotope
> concentrations in spent fuel as a function of time, and burn up, since the
> spent fuel was removed from the reactor. I don't know what it was called
> but it may be referenced in
> DOSE CONVERSION FACTORS USED IN THE CURRENT CANADIAN HIGH LEVEL WASTE
> DISPOSAL ASSESSMENT STUDY
>
> J. R. Johnson
>
> AECL-7869, Radiation Protection Dosimetry 3 No. ½ (1982) 47-50.
>
>
>
> John***************
> John R Johnson, PhD
> CEO, IDIAS, Inc.
> Vancouver, B. C.
> Canada
> (604) 222-9840
> idias at interchange.ubc.ca
>
>
> ----- Original Message -----
> From: "Jim Hardeman" <Jim_Hardeman at dnr.state.ga.us>
> To: "Mike (DOH) Brennan" <Mike.Brennan at DOH.WA.GOV>; <radsafe at radlab.nl>
> Sent: Thursday, July 26, 2007 3:15 PM
> Subject: RE: [ RadSafe ] RE : Spent fuel and decay
>
>
>> Mike --
>>
>> Good observation. As I recall, the primary driver for long-term isolation
>> of spent fuel is dose through the groundwater pathway. I'd have to go
>> back and look not only at 10 CFR 63 but EPA's standards, but I believe
>> EPA wants groundwater concentrations of radionuclides to be less than
>> their Maximum Contaminant Level (MCL) over the entire period over which
>> consequences are assessed -- I think that's now up to 100,000 years.
>>
>> I don't know much about the geology of Washington State, but if your
>> geology is anywhere like Georgia's, you'll find quite a few places that
>> exceed MCL for naturally-occuring radionuclides (Ra-226, Ra-228, uranium
>> being the ones currently regulated -- plus total alpha activity
>> (excluding uranium) and total beta activity) . While the MCL for
>> beta-emitters is based on dose (i.e. 4 mrem/yr assuming 2 liter per day
>> consumption rate), the actual dose from Ra-226, Ra-228 and uranium at MCL
>> concentrations will be substantially greater. The MCL for uranium, for
>> example, is in ug/l (30 ug/l as I recall) rather than pCi/l. We've
>> noticed that the U-234 / U-238 ratio in groundwater isn't constant, and
>> that the dose associated with a concentration of 30 ug/l can vary
>> considerably based on the U-234 / U-238 ratio.
>>
>> What I'm getting at here is that the regulatory framework for spent fuel
>> actually regulates risk through the groundwater pathway at a value far
>> less than the risk associated with groundwater that might be associated
>> with natural uranium deposits.
>>
>> My $0.02 worth --
>>
>>>From the piney woods of northern Michigan (on vacation)
>>
>>
>>
>> Jim Hardeman, Manager
>> Environmental Radiation Program
>> Environmental Protection Division
>> Georgia Department of Natural Resources
>> 4220 International Parkway, Suite 100
>> Atlanta, GA 30354
>> (404) 362-2675
>> Fax: (404) 362-2653
>> Personal fax: (678) 692-6939
>> E-mail: Jim_Hardeman at dnr.state.ga.us
>>
>>
>>>>> "Brennan, Mike (DOH)" <Mike.Brennan at DOH.WA.GOV> 7/26/2007 17:49 >>>
>>>From the information I have and the interesting site Leo linked to, I
>> agree that driver for activity in the long run is Pu. I just ran a
>> spread sheet looking at the U235-U238-Pu239 ratios and the effect on
>> total activity, and it is clear that once the fission fragments have
>> decayed away enough (a couple hundred years, more or less) the total
>> activity is mostly driven by how much U238 was changed into Pu239, and
>> how much of the Pu239 was in turn destroyed by fission. While these
>> numbers would all depend on the original make-up of the fuel and its
>> history with a reactor, it seems reasonable to say that the fuel would
>> reach its original activity after around 10,000 years (fairly wide band
>> "around"), and that it would be low enough activity to handle without
>> special precautions several thousand years before then.
>>
>> All in all, while spent fuel presents non-trivial challenges for
>> storage/disposal, the claims that it must be kept isolated for 100,000
>> (or 1,000,000, as I heard recently) years is clearly not based on actual
>> risk.
>>
>>
>>
>> -----Original Message-----
>> From: radsafe-bounces at radlab.nl [mailto:radsafe-bounces at radlab.nl] On
>> Behalf Of Pete_Bailey at fpl.com
>> Sent: Thursday, July 26, 2007 10:32 AM
>> To: radsafe at radlab.nl
>> Subject: [ RadSafe ] RE : Spent fuel and decay
>>
>>
>>> ... how long it takes spent fuel to decay to the Aactivity level it
>>> had before going into the reactor?
>>
>> If by 'activity level', you mean 'curies', one very very long time.
>>
>>> I realize it is highly dependant on factors such as level of
>>> enrichment, amount of burn-up, activation of cladding, etc, and
>>> breeding of Pu.
>>
>> Level of enrichment & 'burn-up'(MWT/MTU) drive the length of time.
>> Most activation products (active...of clad) fizz out in a decade or
>> so...
>> The breeding of Pu....it ain't there to
>> start with (for all intent and purposes), and has mega-year half-life.
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