[ RadSafe ] Global Warming

[Brennan, Mike (DOH)]

Hi, Peter.

First, thank you for presenting me with a reason to look at this subject
again.  It has been a while since I paid more than passing attention to
fission fragments, and it is an interesting topic, core to some of the
worst (from a technical aspect, anyway) of the arguments surrounding
nuclear power.  

>small ?
>99Tc: 6.05% thermal 235U fission yield
>135Cs: 6.33%
>129I: 0.66% only
>93Zr: 6.30%

OK, so about 1/5th.  Depends, I guess, on your definition of "small".
On the other hand, if you look at activity when the fuel comes out of
the reactor, the long lived fission products (LLFP) are by anyone's
definition a small fraction of the total.  As an example, 135Cs and
137Cs both account for about 6.3% of the atoms in the fission fragment
inventory.  Because of the difference in their half lives, however, in
fresh spent fuel 137Cs produces about 76,000 times as much radiation as
the 135Cs in the fuel.  The 137Cs decay is also about 4 times as
energetic.  

I might concede "small" and go up to "modest" on the % of atoms in fresh
spent fuel that are LLFP.  On the other hand, I would revise the % of
activity from "small" to "vanishingly small" or "trivial" in comparison
the short half life fission products.  

I am now uncertain when the total activity of the spent fuel becomes
less than the total activity of the fuel before going into the reactor,
but I am pretty confident of two things: (1) It is a long time; long
enough that I won't be personally concerned, and (2) in a much shorter
time frame, a couple of hundred years or so, the activity of the fuel
will have decreased to the point where the greatest danger is from one
of our less sophisticated descendants taking a length of fuel rod and
beating someone over the head with it. 

As for transmutation of LLFP, I've seen some articles speculating on it,
but I frankly don't see the need.  If it happens when spent fuel is put
in a fast flux reactor to burn more of the fissile material, cool, but I
just don't see that in and of itself transmutation (with any foreseeable
tech) is worth the effort.

Thanks again for pointing my attention this way. 

-----Original Message-----
From: Peter Bossew [mailto:Peter.Bossew at reflex.at] 
Sent: Wednesday, December 09, 2009 12:04 PM
To: Brennan, Mike (DOH)
Cc: radsafe at radlab.nl
Subject: Re: [ RadSafe ] Global Warming

"Brennan, Mike  (DOH)" <Mike.Brennan at DOH.WA.GOV> writes:
>There aren't actually a lot more isotopes after the etc.


this is true.


>, but yes, there
>are some fission fragments that have long half lives.  However, they
>represent a small fraction of the inventory of fission products in
>"fresh" spent fuel, either on an atom basis or an activity basis.  They
>also generally represent a small fraction, again on an activity or atom
>basis, of the fissile material that was consumed by the reaction (the
>exact ratio is dependent on many factors). 


small ?
99Tc: 6.05% thermal 235U fission yield
135Cs: 6.33%
129I: 0.66% only
93Zr: 6.30%

while 99Tc and 129I can be subjected to transmutation (in principle; if
someone is willing to pay for this), 135Cs and 93Zr cannot, to my
knowledge.

Has anybody calculated what a system - certainly scientifically
beautiful,
on paper -  would cost (e.g. in Euro / MWh) which includes advanced
reactors, reprocessing of high burn-up fuel, actinide burning,
transmutation of fission products, and including probably decades of
development until it works large scale ? Any figures available ?

Peter Bossew



> In most cases, even with the
>long lived fission fragments mentioned, somewhere in the 300 to 500
year
>range the spent fuel will probably become less radioactive than the
>fresh fuel was, even including the unused fuel and fissile
transuranics.
>It gets even better with reprocessing.
>
>So, if the assumption is that radioactive material is bad, and that we
>need to be willing to sacrifice now in order to protect less
>technologically sophisticated later generations, it is clear that the
>ethically sound choice is to use as much uranium as possible now to
make
>electricity, so that there will be less radioactive material in the
>world later.
>
>-----Original Message-----
>From: radsafe-bounces at radlab.nl [mailto:radsafe-bounces at radlab.nl] On
>Behalf Of Peter Bossew
>Sent: Wednesday, December 09, 2009 3:47 AM
>To: gstanford at aya.yale.edu
>Cc: radsafe at radlab.nl
>Subject: Re: [ RadSafe ] Global Warming
>
>George Stanford <gstanford at aya.yale.edu> writes:
>
>(...)
>>
>>
>>     Then the only waste would consist of fission 
>>products, which can be easily isolated in various 
>>ways for 300 - 500 years, by which time their 
>>radioactivity has decayed below any reasonable level of concern.
>
>(...)
>
>129I: half life 1.57e7 a
>99Tc: 2.11e5 a
>135Cs: 2.3e6 a
>etc.
>
>
>Peter Bossew
>
>_