🚀 go-pugleaf

"D.A.Kopf" wrote:
> 
> Don Libby wrote:
> >
> > "D.A.Kopf" wrote:
> > >
> > > Murray Love wrote:
> > > >
> > > > "D.A.Kopf" <dak@dakx.com> wrote in message
> > > > news:3942D053.82030642@dakx.com...
> > > > > Murray Love wrote:
> > > > > <snip>
> > > > > >
> > > > > > I have another question for the "clean energy" proponents.  Assume for the
> > > > > > sake of argument that a nuclear energy technology is developed that
> > > > > > a) Cannot melt down;
> > > > > > b) Produces a vastly reduced amount of unusable waste;
> > > > > > c) Operates passively to shut down the reaction if anything goes wrong;
> > > > > > d) Produces inexpensive 24/7 baseload.
> > > > > > e) Is scalable (can be very large or quite small)
> > > > >
> > > > > Is this hypothetical process also sustainable, or just a short-term fix
> > > > > that makes it easy to postpone long-term thinking?
> > > >
> >
> > Perhaps if you were more specific about the time-frame you are using to
> > determine the meaning of "sustainable" and "long-term".  
> 
> I'd relate sustainable and long-term to the longer known biological lifetimes,
> say a few thousand years.

Letting Joshua Trees set the standard, eh?  It's tough to do anything
but speculate way out there in the future uncertain, but a few thousand
years is a problem that must be grappled with where permanent isolation
of long-lived isotopes is concerned, so I can go with that.  Yes, with
breeding and sea-water extraction, nuclear power is sustainable for a
few thousand years.

Since I see climate change as perhaps the major looming threat to
sustainability, especially as that relates to the sustainability of
biological diversity, I would opt for a time frame more on the order of
decades to centuries when it comes down to practical matters of energy
policy in the here-and-now.  A large increase in atmospheric GHG
accumulation over the next 100 years would set the stage for major
climatic change in 300 years' time (or so says IPCC).

Basically, my view comes down to (1) nuclear power can help reduce GHG
emissions to the large extent necessary to avoid climate catastrophe,
(2) with very low fertility rates, human population could gradually
decline from a peak of 8 Billion in 2050 to 2 Billion around the year
2200 time frame, therefore (3) right now we probably don't need to worry
much about whether nuclear power is sutsainable for more than a few
hundred years, though we should be mindful of the long-term (several
thousand year) legacy of nuclear waste, so (4) the quantity of
long-lived isotopes should be reduced if doing so does not increase the
risk of biological harm.

> 
> >
> > 3,500 GW of nuclear electricity would be sustainable for hundreds of
> > years using Thorium,  Uranium, and Plutonium as fuel with a modified
> > fuel cycle.  If folks in the 22nd century act so as to gradually reduce
> > human population from 10 B to, say, 2 B by the year 2300, then there
> > will be no need to sustain 3,500 GW of nuclear electricity more than a
> > few hundred years.
> 
> Yes, hundreds of years would be my guess too. But you seem to be agreeing that
> during this period, folks would be wise to reduce community energy usage?

Yes indeed.  A huge proportion (near 70%) of electricity generated is
lost through transmission and distribution.  I suspect that fuel
requirements for electric power would be greatly reduced with improved
transmission and distribution techniques and organization.  

Sticking to the main storyline, the IPCC LESS scenario assumes that the
amount of energgy consumed per unit of world GDP will be reduced about
95% through conservation and efficiency gains, and through
"dematerialization" of economic value creation (i.e. the new
"information economy").  GDP is expected to be 25 times higher than 1990
levels in the year 2100 with no increase in primary energy consumption
in the (currently) developed world.

> 
> >
> > Since a closed nuclear fuel cycle is adequate to handle this load
> > indefinitely, and since CO2 emissions would be curtailed to avoid
> > massive global climate change, then yes, the nuclear option is
> > sustainable, if it can be packaged in a form that is socially acceptable
> > to all but committed anti-nuclear fundamentalists.
> 
> Now, now, we agreed to discuss a hypothetical process satisfying a) thorough
> e). You are getting unfairly close to the assertion that they can become true for
> nuclear energy.

I haven't signed on to Murray Love's terms yet, but to avoid disrupting
what seems to be a fruitful discussion, I'll hold my tounge for now
(except to remind you of my threads last month about the "New Clear
Reactor" and "A better nuclear fuel cycle" :o)

> 
> I am not so optimistic about extraction of fission fuel from granite or sea
> water, but would welcome some small pilot plants to demonstrate actual net
> energy production from such processes.

Yeah, me too.  Grahm Cowan posted the URL of a Japanese demonstration
project recently.  It's been done.  I'm sure if the process can be
scaled up to commercial production economically, the Japanese will find
a way to do it.

> >
> > >
> > > Well, current nuclear production has a rather poor thermal efficiency, putting
> > > two units of heat energy into the plant environs for every one unit of
> > > electricity produced. Consumption of this one unit of course also ultimately
> > > ends up as heat.
> >
> > Waste heat can cause local environmental disturbances, hence cooling
> > towers.  A ten-fold increase in nuclear generation per the IPCC LESS
> > scenario outlined above would throw off 10 times the heat, to be sure.
> 
> Cooling towers are not without environmental disturbance. For one thing they
> are classed as consumptive use of water as opposed to non-consumptive river or
> pond heat exchange. And water shortages do seem to be becoming more frequent
> in the US.

Not to mention water-vapor contributing to local heat islands.  Another
note:  cooling towers have a range of operating temperatures that have
in some cases been exceeded in recent extreme heat waves, causing plants
to shut down.  This is true for thermal coal plants too.  Climate change
may influence power plant design sooner than we think.


> 
> >
> > I once calculated that painting an area the size of Europe and Australia
> > white would be the extent of albedo control required to offset global
> > warming -- probably more practical just to build ten times more nuclear
> > power generating capacity (of the extremely safe, socially acceptable
> > variety, of course).
> 
> I agree assisted cooling of the earth is not a farfetched idea. According to
> some atmospheric models a relatively simple injection of solar-absorbing,
> hence self-lofting, fine soot particles into the upper atmosphere would do the
> job. Of course you might have to deal with fanatical nature lovers screaming
> about the loss of stars in the night sky. If any remain at that time.

You mean stars or fanatical nature lovers?  Yes, years ago in
sci.environment we discussed the virtues of orbiting parasols the size
of Mexico to block incoming solar radiation.  Not too popular with the
amateur astronomers.

-dl