🚀 go-pugleaf

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".  If human
> population levels off at 10 Billion in 2100 as expected, then about
> 3,500 GW of nuclear electricity could provide about half of projected
> electricity demand while allowing the global GDP to grow 25 times 1990
> levels and stabilizing atmospheric CO2 concentrations at or below twice
> pre-industrial levels (according to IPCC LESS scenario).

I'd relate sustainable and long-term to the longer known biological lifetimes,
say a few thousand years.

> 
> 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?

> 
> 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 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.
> 
> >
> > 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.
> I'm not enough of a physicist to be able to calculate whether that is a
> non-trivial addition to Earth's radiation budget, but Cesar Marchetti
> has suggested that 10^12 people could be sustained indefinitely using
> nuclear power as long as they used albedo control to maintain the
> Earth's heat balance.

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.

> 
> 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.