Newsgroup sci.environment 114077

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Mike Pelletier wrote:
> I was under the impression that plutonium at its normal density could not
> be assembled into a critical mass, which is why they used the implosion
> design to increase the density of the plutonium core to force it to a
> higher, supercritical density.
> 
> Is this incorrect?
It is a function of total mass, form, and moderation.
1.  Total quantity of material is also a function of shape - sphere being 
optimum - and density
2.  Pure metal has a different quantity requirement than oxide
3.  Moderation reduces the total mass required - a subcritical mass in air can 
be a critical mass under water
This is why Pu dust that gets by HEPA filters and coats HVAC ductwork, while 
being a deplorable operations condition, is not fixing to blow up Denver.
-- 
_______________________________________________________
There is none so blind as they that won't see.--Jonathan Swift: Polite
Conversation, dialogue iii.
rbsmith@home.ifx.net

jac@margit.scri.fsu.edu (Jim Carr) wrote:
>dewey@televar.com writes:
>>
>>In the past, low-level radioactive liquids were discharged into
>>unlined trenches.  The radionuclides were promptly adsorbed onto
>>the native soils, which have a rather large ion exchange
>>capacity, and there they sat while decaying.  Today, these
>>trenches are considered radioactive waste storage units.
>
> Although it is not entirely true that everything in these "units" 
> can be considered to be in a permanently fixed location.  But it 
> is true that these low-level disposal areas are a minor problem
> compared to the high-level waste in the tanks -- particularly 
> at Hanford where no records were kept of what went in the tanks. 
Wrong.
I refer you to http://twins.pnl.gov:8001/ to see the records of
what is in the tanks.  You will find gigabytes of online
information including photographs, reams and reams of analytical
data, operations records, etc. etc. that will tell you whatever
you might want to know about what is in the tanks - at Hanford,
Savannah River, and INEL.
> I am told by a friend who works at Savannah River that, although 
> they have their share of sins, the chemical company that ran that 
> facility 
That would be DuPont, I think.
>at least kept records and tended to put X in one tank 
> and Y in another.  
As they did at Hanford.  The difference here between Hanford and
Savannah River is that Hanford had at least four different
production processes running at different times, each of which
made waste with different chemistries. Savannah River only used
one process, and so for the most part, their wastes are all the
same.
[snip]
> But the one think to note in the information from the DOE about 
> cleanup are some of the dates, like 1970 and 1986.  These places 
> were run for 30 to 40 years without any realistic waste management 
> plan in place, probably because cleanup would be the DOE's problem 
> since a contractor had no long-term responsibility for the place. 
The contractors managed the waste just like DOE (or ERDA, or AEC)
told them to.  The issue of waste management was not really very
important to our government when the Russians and were sending
their nukes to Cuba and threatening to annihilate us.
>>     ...             The tank wastes will be separated into a
>>low-level fraction and a high level fraction, both of which will
>>be vitrified (turned into glass).  The low-level fraction will be
>>disposed on the Hanford site, and the high-level fraction will be
>>stored in steel canisters again awaiting permanent disposal at
>>Yucca Mountain.
>
> Note the key word "awaiting".  Here is where there is some bit 
> of controversy.  Although it is good that that the DOE has a plan 
> (not bad after 50 years, right?) I would not characterize it as 
> "very viable".  The alternative, accelerator-driven transmutation 
> of the high-level fraction on site, should be considered before 
> vitrification makes that approach more difficult. 
Fine.  Just consider how you can put a hundred million gallons of
liquid waste into a transmutation accelerator and do it before
even the double shelled tanks start leaking.  We need to do
something *now* and vitrification is the only technology that has
been successfully demonstrated on this kind of waste.
>>   ...      I just hope the public interest "watchdogs" don't
>>become rabid at the prospect of thier reason for existance being
>>eliminated and blow the whole scheme again with thier incessant
>>whining against everything the DOE proposes.
>
> There is a difference between constructive criticism and simply 
> opposing all that is proposed.  The latter poses an environmental 
> risk of its own, since the stability and safety of the tanks at 
> Hanford -- sitting on the banks of the Columbia -- are a legitimate 
> concern.  Doing nothing is not a good option in this case. 
ALL of the tanks at Hanford are at least 8 miles from the river.
They are not "sitting on the banks of the Columbia."  Nobody is
proposing to do nothing.  Your alternative of accelerator
transmutation is just another pie-in-the-sky reason to delay the
implementation of a proven technology - vitrification - that is
ready and waiting to go, right now.
>
>-- 
> James A. Carr        |  "The half of knowledge is knowing
>    http://www.scri.fsu.edu/~jac/       |  where to find knowledge" - Anon. 
> Supercomputer Computations Res. Inst.  |  Motto over the entrance to Dodd 
> Florida State, Tallahassee FL 32306    |  Hall, former library at FSCW. 
dewey@televar.com

In article <32D1437E.517B@rand.nidlink.com>, swilley@rand.nidlink.com wrote:
snip
> source, I believe, of that instruction not to turn on and off, is that
> the bulb life is shortened each time it heats and cools. So with cheap
> electricity, your economic interest in combined cost of power and bulbs
> may be served by not turning it on and off frequently. Same for
> fluorescent lights, TV, computer etc. But from an energy use standpoint,
> turning off at every opportunity does save energy.
snip
Your conclusions from the energy viewpoint are not correct.
The bulb itself represents an energy investment in its manufacture (and
that of the materials from which it is made) and distribution.
Also one cannot directly equate cost to the end user with energy efficiency 
As bulbs are made in large numbers, and the materials from which it is
made in even larger quantities, it is likely that the cost of energy per
unit used during its manufacture is lower than the cost per unit paid by
the end user. This means that the bulb represents a larger energy
investment than its cost to buy would indicate.
If turning a bulb off and on shortens its life (which is probable) then
there will be one answer to the minimum overall cost (to the end user) and
a different answer to the minimum overall energy used which, if my
proposition above is correct, would suggest that the bulb be kept on for
longer periods.
I do not know the details, but i have seen manufacturers data on
fluorescent tubes where the stated life was qualified with a statement as
to the frequency of switching (on and off that is) and the variation of
life with switching frequency was also quoted
-- 
John Shotton