Re: new n-plant siting [was Re: Another study shows CO2 lagging, not leading, temperature rise [Stott et al, Science, Oct 19, 2007]

Whata Fool wrote:
bill <ford_prefect42@xxxxxxxxxxx> wrote:

To illustrate, coal plants run at a maximum temp of 370 °C (643K)
and 3,200 psi (http://en.wikipedia.org/wiki/Fossil_fuel_power_plant)
using an ambient temperature of 20c (293k) gives a max theoretical
efficiency of 54%. we can come pretty close to this with modern
plants.

a PWR nuclear plant uses a high side of 315 °C (588K) and the same
ambient. the max efficiency is therefore 50%. so, why then are the
best nuclear reactors running half this? Well, the heat exchanger
eats a good part of the difference. Now, you can see here that losing
a mere 55 degrees c cost us 4% efficiency. so, what temperature were
you considering running the primary loop at? Can you provide a link
to a design that uses your planned lower T/P units?

The pressure you mention sounds right, are you sure
those are the temperatures? I thought I have seen higher
planned.


That is about right for the primary side temperature in a PWR (actually about 325 degrees C). The steam temperature, obviously, is lower (there must be a temperature differential across the heat exchanger for heat transfer to occur). The drop at full load typically is about 40 degrees C. Steam pressure is about 1000 psi.


Tearing everything down and completely rebuilding is
not always the best way, steam is steam, and nuclear does
produce steam, and there is no reason to change the
generators unless the life cycle time is nearly used up.
As for the generators themselves, you may be right. Heck, even
some of the turbines may be able to be recycled. however, here is
where it becomes pretty obvious that you aren't an engineer, those
turbines and all the periphery equipment were designed and specified
for a *very specific* set of temperature, pressure and flow
parameters, simply saying "steam is steam" neglects everything related
to power plant design, steam at what temperature? what pressure? how
many CFM? saturated or superheated steam? There will therefore be
redesign of the *reactors themselves* required to mate them with any
given set of turbines in an existing coal plant, design changes which
will need to be reviewed by literally thousands of engineers before
they can be approved and implemented. how much simpler to simply site
a new reactor with a preapproved design that is in use in hundreds of
other locations all over the world, all of the bugs of which have been
ironed out, operators of which are already well trained, etc., etc.,
etc.

My mindset is probably nullified by the fact that not much
in the way of switching from coal to nuclear will happen.

No turbine plant uses saturated steam, it would destroy
the turbine.


That is not correct. A PWR produces saturated steam (about 285C at 1000 psi at full load). BWRs are about the same. That is why turbines (along with their auxiliary systems) for nuclear plants are not the same as for fossil plants. They must be designed to operate at lower pressures and temperatures and various means must be provided to remove moisture from the steam just so that it does not destroy the turbine. Even the electrical generators are different because PWR/BWR plant turbine-generators turn at half the speed of those in fossil plants (so that the low pressure turbines can have a larger diameter). You could not redesign a PWR or BWR to produce steam characteristics to match a fossil turbine-generator.

It might be a different story with gas cooled reactors. One might be able to use something like a PBMR to generate steam that is usable in a fossil turbine. The PBMR designs under development, however, are not intended to be steam plants, rather they will use the hot gas directly in gas turbines, not steam turbines (http://www.pbmr.com/index.asp?Content=4&;). The savings in reusing existing turbine generators would be swamped by the lower efficiency of the steam generation process vs the direct use of the gas in a gas turbine. It does not matter that efficiency is less important for a nuclear plant vs a fossil plant (because of the lower fuel costs)--in a given plant if you generate more electrical power you make more money.


My statement addresses the "crisis", where as many
coal boilers as possible could be replaced in the least
possible time, but with environment feet dragging, there
will be very few nuclear plants built, they like the idea
of providing more CO2 for their trees to eat.
Yes. Nimby and the "NO" mindset are totally capable of
overwhelming even the best of engineering arguments. which is why I
maintain that we are in fact fucked. because the chinese have a very
strong "yes" mindset, no nimby, and the will to power. AGW... well,
sorry, but it's a lost cause. only nuclear war can reduce co2 output.

That would be definite except for the fact that PV production,
and also solar thermal-electric plant building is increasing at a rapid
pace, possibly as much as 50 percent a year globally.
And the new battery technologies will make a huge difference.

I saw a site that shows where power plants are installing
storage units of 2 megawatts for 6 hours or more to increase peak
load, and utilize off peak capacity better.

Perhaps more plants will start selling exhaust steam instead
of condensing it, that would be the same as a new source of energy,
and provide more revenue for more improvements.

If enough of these energy ideas are implemented, the issue
of any AGW can be more or less ignored because with the new
technologies, carbon emissions will be reduced more than any
agreement calls for.



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