Posted by The Natural Philosopher on December 9, 2008, 12:24 pm
David Hansen wrote:
> On Mon, 08 Dec 2008 01:44:58 -0500 someone who may be Neon John
>
>> So the answer is "no", then. Fair enough. End of discussion. It would be
>> like me trying to debate with a heart surgeon about what type of stint was
>> best. He'd laugh at my ignorance and I'd be the fool. so it goes here.
>
> Nice try. Your bluster may convince some, but it will not convince
> many. Meanwhile I'll stick with discussing the subject.
>
>
It convinces all but the Faithful Greenpissers.
>
Posted by harry on December 8, 2008, 7:11 pm
> On Sun, 07 Dec 2008 18:07:36 +0000, David Hansen
> >On Sun, 07 Dec 2008 12:40:28 -0500 someone who may be Neon John
> >>People just don't understand the magnitude of the energy problem.
> >Don't assume that anyone who disagrees with you, "just don't
> >understand the magnitude of the energy problem."
> >No form of electricity generation produces electricity continuously
> >at full output. It is necessary to understand their individual
> >foibles to understand the issues.
> Before we go on, might I ask if you have any utility experience at all? As a
> retired nuclear engineer, I like to know about the folks I debate with.
> >"Different types of generators operate at a range of capacity
> >factors - during 2004, gas power stations had a capacity factor of
> >around 60 per cent, nuclear 71 per cent, hydro 37 per cent, pumped
> >hydro 10 per cent, and coal 62 per cent. Meanwhile, the overall
> >average capacity factor (or load factor) for the UK electricity
> >network is around 55 per cent.
> What I see is gross incompetence. Especially in the nuclear area. Perhaps
> some of your engineers ought to come over here and talk to some of our
> engineers. As an example of what CAN be done:
> http://www.usnuclearenergy.org/2007_Plant_Production.htm
> the juicy part:
> "he 104 nuclear plants operating in 31 states also achieved a record-setting
> average capacity factora measure of on-line availability of power. The 2007
> average of 91.8 percent surpassed the 2004 record of 90.1 percent, according
> to preliminary figures. Capacity factor is the ratio of electricity actually
> produced compared to the theoretical maximum electricity a power plant can
> produce operating at full power year-round."
> Executive Summary:
> US: 92%
> YOU: 71%
> Sounds like some operators need to go to nuclear Special Ed training. Neon
> John's College of Nucklar Knowledge is open for business....
> Here's a little tip from inside the industry over here. Capacity factors are
> going UP because both because refueling outages are being extended past the
> traditional 18 months and because the plants and procedures are getting even
> more reliable.
> Since most of the rest of your article is quoted from something and someone
> whom I've never heard of and does not represent your knowledge, I'll end this
> round of debate at this point.
> BTW, we have quite a number of pumped storage plants, among the largest being
> Raccoon Mountain near Chattanooga, TN. I happened to have a large involvement
> with that plant, from working heavy equipment moving dirt and hauling the
> turbine wheels on TVA's private railroad during construction to operations
> training before I decided to become an engineer. I've "been there, done that
> and have the belt buckle"
> http://www.neon-john.com/Nuke/TMI/TMI_buckle.jpg
> John
> --
> John De Armond
> See my website for my current email addresshttp://www.neon-john.comhttp://www.johndearmond.com<-- best little blog on the net!
> Tellico Plains, Occupied TN
> Serenity: That feeling of knowing that your secretary will never tell either of your wives.
This arises because the nuclear plants are run as "base load". as
they can't be quickly started and shut down. Ie they run all the
time. In the UK peak loads are met with gas turbines which can be
started up in minutes.
The world's first commercial / nuclear power plant was in the UK. we
know all about nuclear power and are still the world's leading
reprocessor of fuel.
http://en.wikipedia.org/wiki/Sellafield#Calder_Hall_nuclear_power_station
Posted by Jim Wilkins on December 10, 2008, 5:43 pm
> ...
> ...Through faulty instrumentation and to a lesser extent faulty operator
> training, the core was allowed to go dry and remain dry for almost 24 hours.
> And then when cooling water was turned back on it shocked the then-white-hot
> core pieces into fracturing.
> ...about the
> central one third melted and slumped down into the rest of the core. But the
> preliminary reporters didn't know and could not know until the core remains
> were removed several years later, is that part of that core actually liquefied
> and ran down into the bottom of the reactor vessel where it was quenched into
> a solid glasslike substance.
> ...
Thank you very much for this description.
My limited amateur understanding was that without water to slow down
neutrons, fission would decrease and decay would be the major heat
source.
jw
Posted by Neon John on December 11, 2008, 12:11 am
wrote:
>Thank you very much for this description.
You're most welcome.
>My limited amateur understanding was that without water to slow down
>neutrons, fission would decrease and decay would be the major heat
>source.
That is true. However, realize that a core with a few million megawatt-hours
on it produces about 10% of its full rated power from decay heat at the
instant of SCRAM. This power output decays rather rapidly so that in a few
hours it is not significant in terms of a percentage of full output. Still a
lot of heat, of course.
Another thing to be aware of is that a core does not instantly shut down when
SCRAMed. The control rods can't absorb even a small fraction of the available
neutrons - just enough to shut the core down with a great deal of margin. It
takes a little while - minutes - for the nuclear reaction to taper off. The
decay is exponential and it nearly asymptotes for quite some time from delayed
neutron emissions as part of the short lived fission product decay process.
This has no effect on the core's behavior during an accident, for it will be
cooled passively for longer than that but it is a bit of knowledge that is
handy to have. That is, understanding that a nuke is neither turned on or off
instantly as if a switch were thrown.
In a PWR, the turbine and reactor trips are intertied (post-TMI
lessons-learned) so that the initial decay heat is handled by the condenser
bypass, or if the condenser vacuum is lost, via atmospheric vents (spectacular
in both sight and sound). As the decay heat declines, other systems take over
until ultimately the RHR (residual heat removal) system assumes the duty of
carrying away the little heat still being produced when the system is
de-pressurized.
In a BWR during a SCRAM, part of the steam drives the HPSI (pronounced
"Hipsy") pump (that takes water from the torous or suppression pool, depending
on the MK number) and injects it directly into the reactor. This is a steam
driven pump and all the valves fail open so it cannot fail to run. Plus there
is quadruple redundancy. As the decay heat lessens and the pressure drops,
cooling is transferred to the LPSI ("Lipsy") pump. Pretty much identical in
function to the HPSI, those turbine driven (and one electric for each type for
diversity) pumps provide cooling water as long as steam is being made.
When the steam production stops, the core is cool enough for the RHR system to
take over. The RHR consists of simple water to water heat exchangers and
pumps, one side receiving primary water and the other side river water from
the Vital Service Water supply. This is a multiply redundant source of
cooling water that can be drawn from the river or from the condensate storage
tanks (typically 2 - 1 million gallon tanks per unit).
Well, enough brain dumping for one day.
Later,
John
--
John De Armond
See my website for my current email address
http://www.neon-john.com
http://www.johndearmond.com <-- best little blog on the net!
Tellico Plains, Occupied TN
Multitasking: Reading in the bathroom!
Posted by Chris J Dixon on December 11, 2008, 7:45 am
Neon John wrote:
>In a PWR, the turbine and reactor trips are intertied (post-TMI
>lessons-learned) so that the initial decay heat is handled by the condenser
>bypass, or if the condenser vacuum is lost, via atmospheric vents (spectacular
>in both sight and sound).
When working on a coal fired 500 MW set, I was fascinated to see
the sizeable explosion diaphragms fitted to the LP turbine
casings. Basically a foil disk about 300 mm dia, with a sharp
point poised to pierce it if it ever bulged upwards. Later I was
commissioning a relay rack which controlled the turbine hall
windows. They were opened just before all condenser vacuum was
lost. I would not have wanted to be there.
Chris
--
Chris J Dixon Nottingham UK
chris@cdixon.me.uk
Have dancing shoes, will ceilidh.
>
>> So the answer is "no", then. Fair enough. End of discussion. It would be
>> like me trying to debate with a heart surgeon about what type of stint was
>> best. He'd laugh at my ignorance and I'd be the fool. so it goes here.
>
> Nice try. Your bluster may convince some, but it will not convince
> many. Meanwhile I'll stick with discussing the subject.
>
>