Heat Wave Shuts Down Alabama Reactor

mdsolar writes "In a first for the US, one of three nuclear reactors at the Browns Ferry nuclear plant in Alabama has been shut down because the Tennessee River is too hot to provide adequate cooling for the waste heat produced by the reactor. This is happening as the TVA faces its highest demand for power ever, reports the Houston Chronicle. This effect has been seen in Europe in the past, forcing reduced generation, but the US has until now been immune to the problem. The TVA will buy power elsewhere and impose higher rates, blaming reduced river flow as a result of drought."

This is actually really good news

[Anonymous Coward]

As for a while, they were planning to use one engineer's idea of cooling it with ice cold beer.

Re:

[__aaclcg7560]

Nah... They need to build another nuclear reactor to run the chiller for both the reactors AND the beer.

Re:This is actually really good news

[Bloke down the pub]

s/ice cold beer/frosty piss/

If the beer's Bud, don't bother - there's no difference.

Re:

[ericrost]

Says the AC

In Soviet Russia

[davidwr]

In Soviet Russia, overheating nuclear reactor [wikipedia.org] shuts down YOU!

Meanwhile Back In Alabama

[cluckshot]

A little noted fact of the cold war is that a very large amount of the US total electrical generation capacity is in the TVA region (Tennessee River - Dependent) The loss of this reactor is serious as the whole USA has no reserve capacity at peak load and with the heat wave over the East USA this is a critical loss. If it were the only reactor in danger this might be of no concern. The US TVA operates 5 big reactors and numerous coal fired plants all of which have the Tennessee River at thermal capacity to cool them and the river is dropping daily.

If heavy sustained rain does not fall on the Tennessee River Valley over the next 3 to 4 months an event which is historically unlikely, the loss of something close to 15 times the Browns Ferry reactor in capacity is likely to hit the USA. There is nothing to pick up the load. The loss of this one reactor is nearly equal to all the wind energy the USA generates. This loss threatens the operations of every one of the 48 US States. With the possible loses in Alabama Power pools and their reactors etc as well as Georgia Power, this poses the very real risk of cutting the energy supply of the USA by a very large fraction. As I write the North Alabama region is short 60 inches of rain over the past 18 months. The US TVA has been drawing down storage for 5 years now. There is no reserve and little prospect of one for some years to come.

I had warning of this imminent event when the City of Huntsville requested from TVA more water for its treatment plant and was turned down for supply. I knew then that the supply was gone.

Re:Meanwhile Back In Alabama

[yusing]

Huh. Gosh. See, if we'd invested in a MIX of power instead of depending so heavily on coal and nuclear (which the industry is trying to bump up in significance), we wouldn't be facing such a predicament.

Germany has wisely seen fit to invest one-seventh of its power money in wind energy. And it has legislated, and many Germnans have benefited for years already, from a solar-energy subsidy.

Too bad we don't have uncorrupted, uncronyed leadership in the US with the courage and vision to diversify the energy portfolio. Pay now or pay MUCH MUCH more later.

Nuke-lovers are always griping that wind-energy is too unreliable. Huh, guess what?

Re:

[UbuntuDupe]

Too bad we don't have uncorrupted, uncronyed leadership in the US with the courage and vision to diversify the energy portfolio

What do you call the energy futures market?

Re:Meanwhile Back In Alabama

[Ecks]

TFA has the engineering wrong. The problem isn't the river temperature as much as the air temperature. A nuclear power plant needs to be located near a river so it can have a large supply of relatively cool water to use as a working fluid. The river water gets boiled into steam by reactor water in the nuclear reactors primary coolant loop. This is steam is what turns the turbines and generates the electricity. When it exits the turbines it's still steam, it's just cooler and wetter. You can't return it in this state because doing that would dramatically raise the river's temperature. You have to cool it down before you can put it back. To do that you use a passive air to water heat exchanger. But they're having a heatwave down there. Between the starting temperature of the river and the reduced efficiency of the passive heat exchanger using all three reactors in the plant would heat the river to unacceptable levels.

Unacceptable is not boiling it's probably something in low 90F range because if the mean temperature of the river was over 90F for any period of time you raise the risk of algae blooms and fish kills.

Physical conditions are not preventing the plant from running, environmental considerations are. And if the river's temperature is close to or exceeds the contracted discharge temperature without being heated by the plant then reevaluating the environmental decision may be in order.

-- Ecks

using this to impeach nukes is profoundly wrong

[arete]

Using this to impeach nukes is profoundly wrong.

I'm in favor of alternative, renewable energy sources, but each source has varying degrees to which it is useful in particular situations for technology and production cost reasons. (For example, many places just don't make a good wind farm - and some places make an extremely mediocre and very expensive one.) I think we're going to have a bloom of much better solar at some point, but there's definitely still some room for improvement there.

I'm also certainly

Re:In Soviet Russia

[Belacgod]

Soviet Russia doesn't refer to USSR. It's to distinguish it from Tsarist Russia, or Kievan Russia, or any of the other regimes that ruled Russia. Similar usages in other countries: Napoleonic France, Imperial Rome, Colonial America, Nazi Germany.

Re:In Soviet Russia

[Oktober Sunset]

Actually, it's to distinguish it from Russia now. The original joke just said Russia, it was only after the collapse of the USSR that it changed.
There's not really much worry about people think the jokes are about Tsarist Russia is there?

(After writing this bit, it bacame clear to me that subconciously, I envision 1st Dude to be Brian Griffin, and 2nd Dude to be Stewie.)
1st Dude: "In Russia overheating reactor shuts down YOU."
2nd Dude: "Oh yea, thats funny, I get it, cos like, they just used uranium for yellow pottery glave back in Tsarist times right? Thats funny. No wait, Don't get that, that makes no sense"
1st Dude: "No, like I mean the Soviet era, like Chernobyl blowing up"
2nd Dude: "oh right, like why didn't you say"
1nd Dude: "I dunno, I figured it was obvious"
2nd Dude: "wasn't umm wasn't Chernobyl in the Ukraine"
1st Dude: "What am I like, a geography teacher now?"
2nd Dude: "that's like pretty poor taste man, a lot of people died"
2nd Dude: "That's not really funny at all"
1st Dude: "In Soviet Russia, taste poors YOU! heh heh"
2nd Dude: "that one wasn't even a sentence"

not immune

[thhamm]

>but the US has, until now, been immune to the problem.
no, not immune. it just hasn't happend until now.

Re:not immune

[johnpaul191]

i'm immune to zombie attacks.

Re:not immune

[Oktober Sunset]

so, you have no brain? No juicy juicy brain?

Reasons right?

[Anonymous Coward]

I work at a nuclear power plant. We have a limit for the temperature of the river downstream of our returned cooling water for environmental reasons, not reasons related to the power generation process. I suspect the TVA has a similar requirement.

I noted from the nrc website (www.nrc.gov) that their other reactors are operating at reduced load, which is what our reactors must do to limit the heat input into the river.

So this is nothing remarkable.

Re:Reasons right?

[Toad-san]

I see those huge cooling towers and water cooling systems .. and I have to wonder ...

How efficient is a power generation plant that throws away gigawatts of power as waste heat?

Isn't it about time you find a more efficient way to generate power, turbines and generators that don't waste so much heat that we just went to all that trouble to make in the first place?

I don't expect 100% efficiency, but what we're doing now is crazy.

Re:Reasons right?

[Wonko the Sane]

Physics: It's not just a good idea, it's the law [wikipedia.org].

Some people sell their "waste" heat

[Colin Smith]

To heat domestic water, space heating and even to power adsorption chillers which can reduce AC requirements. Even coal power stations can hit 88% efficient.

http://www.helsinginenergia.fi/en/tuotanto/benefit s.html [helsinginenergia.fi]

US power stations are still only 40% efficient because ... Well you decide for yourself.

 

Re:

[Wonko the Sane]

You are just playing word game with the definition of "efficient". There is a fundamental limit of how much work can be extracted by heat flow between two temperatures.

I would expect a country with a colder climate to be able to extract more work out of a nuclear reactor. Those super-efficient reactors won't do so well with a 90 Fahrenheit cooling medium

Re:

[Colin Smith]

You are just playing word game with the definition of "efficient".

No. I am not. It's energy used for a useful purpose.

There is a fundamental limit of how much work can be extracted by heat flow between two temperatures.

And extracting work isn't the only use for heat...

 

Re:

[Waffle Iron]

That works great assuming that you're close enough to a power plant so that it makes economic sense to dig a tunnel full of big fat steam pipes to your house. Unfortunately, only a tiny fraction of the population lives that close.

Re:

[Colin Smith]

Unfortunately, only a tiny fraction of the population lives that close.

Not necessarily the case.

In Denmark they have a truly *huge* "district heating" network.

e.g.
http://www.dbdh.dk/ [www.dbdh.dk]

 

Re:Some people sell their "waste" heat

[Waffle Iron]

That's because so many people in Denmark are close enough to a power plant to run steam tunnels to their locations. The trend in the US over the past decades has been to build huge power plants in the middle of nowhere, so it just wouldn't work here.

Recently, a new trend has been to build smaller cogeneration facilities in populated areas in the US, but due to valid political and environmental concerns, the only viable fuel for these is natural gas. That fuel is already in short supply and dwindling fast, so that's not going to solve the problem by itself.

Re:Some people sell their "waste" heat

[fabu10u$]

Some people sell their "waste" heat
To heat domestic water, space heating and even to power adsorption chillers which can reduce AC requirements.

Try selling the US public on steam heat from a nuke. Yes, the coolant loop neither touches the core nor picks up radioactive ions, but see if you can get the unwashed masses to believe they'll be safe with it!

Re:Some people sell their "waste" heat

[clovis]

Even more unlikely, try selling people on the idea of placing nuke plants in large metropolitan areas so they can buy piped in heat from the plant.

Now if you presented to the American public with the word "free" heat, then we might get something going.

Re:

[Kadin2048]

Nuclear plants are expensive, but we build them anyway because they produce energy at a marketable cost. They don't line steam tunnels with thermocouples, because the electricity that they produce would be too expensive to be marketable.

The reason that power plants throw away lots of heat is because it's not economically feasible to do anything with it. In time, as the cost of energy increases, it might be worthwhile to extract more from it, using more expensive methods. But at the moment, it's not.

Trying t

Re:

[timeOday]

Physics: It's not just a good idea, it's the law.

Oh brother. It's past time for a Godwin's Law [wikipedia.org]-style rule about thermodynamics on slashdot. Every time [google.com] somebody propses conserving wasted energy, somebody else retorts that perpetual machines are impossible or something to that effect.

Re:Reasons right?

[hankwang]

How efficient is a power generation plant that throws away gigawatts of power as waste heat?

From the heat source to electrical power output is usually in the range 35--50%, depending on the plant design. A fundamental problem is the theoretical limit of the efficiency of a heat engine, a device that converts a temperature difference into mechanical power. It is 1 - Tcold/Thot, where Tcold and Thot are the temperatures of the cold and hot parts, in kelvin. For a steam-operated heat engine, the cold end is around the boiling point of water (373 K), and the hot end might be 1000 K, which limits the efficiency to 63% if there are no other losses. But one can use the waste heat for other purposes in a cogeneration plant [wikipedia.org], for example for residential heating in cold climates or for the industry.

Re:

[Colin Smith]

The "waste" heat can power adsorption chillers in hot climates.
 

Re:

[Wonko the Sane]

You want to cool the water just a little bit below the condensing point, so that your pumps to do not cause the water to boil again (rough on the impellers). Any cooling below the condensing point is waste, so you want to minimize it to a little as practical,

A common error is to forget that the boiling and condensing temperature are highly dependent on pressure. Inside a condenser, the temperature and flow rate of the cooling water will determine the condensing temperature and pressure of the steam.

Re:

[Wonko the Sane]

Sorry, there are several types of "water" in these systems...

The steam that drives your turbines is condensed, then is pumped back into your boiler. (secondary water)

The condenser is cooled by the river water.

You don't mix the secondary water and the river water, because the boilers require very pure water with a controlled chemistry.

Excessive cooling of the secondary water is a waste which must be minimized.

Re:Reasons right?

[Cyberax]

Nope. You can't beat http://en.wikipedia.org/wiki/Carnot_cycle [wikipedia.org] in efficiency. The practical upper limit for nuclear power plants is about 50%. And we're already getting closer to this limit.

We can use some insane things like high temperature (thousands degrees) reactors with gas cooling to get another 10%-15% of efficiency, but it is just not practical.

Re:

[Chandon Seldon]

We can use some insane things like high temperature (thousands degrees) reactors with gas cooling to get another 10%-15% of efficiency, but it is just not practical.

Never, ever, ever dismiss that sort of technique (i.e. engineering problems) as "not practical". It may not currently be a good business decision under the evaluation rules being used by the management at a particular company, but that doesn't mean that a significant performance improvement that requires new techniques isn't a viable (and essen

Re:

[turgid]

Isn't it about time you find a more efficient way to generate power, turbines and generators that don't waste so much heat that we just went to all that trouble to make in the first place?

There is a British design called the AGR [wikipedia.org] which operates at thermal efficiencies of up to 40% compared with 30-33% in a PWR (what they used in the USA). The thing is, it's terribly expensive and no more will ever be built.

As another poster has already stated, look up the Carnot Cycle to learn about thermal efficiency of

You're right it is insane. 88% is possible

[Colin Smith]

Especially considering the coming energy crunch.

 

paddle wheels in the heat stream

[Quadraginta]

Heat is disorganized motion, right? Atoms and molecules just bumping around any which way. If you want organized motion, which is useful energy -- such as an organized motion of electrons, a.k.a. electricity -- then you have to get that heat motion organized, flowing in one direction.

You do this by making the heat flow from one place to another. But here's the catch: you need a source and a sink to have a flow. The hot reactor core is the source. The river is the sink. Heat flows from the former to th

Re:paddle wheels in the heat stream

[Quadraginta]

Sure. Now if only someone in Alabama living close to the power plant needed to heat his house in the middle of a heat wave...

Re:paddle wheels in the heat stream

[QuickFox]

Are you thinking a forest of insulated two-foot steam pipes running all around town? Sounds pretty ugly, noisy, expensive and environmentally disruptive.

Here in Sweden we've had this in the cities forever. It's not ugly, noisy, expensive and environmentally disruptive. Instead it's underground.

Generally they don't transport steam, they transport hot but liquid water.

See, engineers are not idiots.

You must be new here.

Re:

[Quadraginta]

You need to google "Maxwell's Demon."

Re:

[mdsolar]

According to the article, this is different from environmental requirements on the down stream temperature. This is a lack of cooling capacity problem. The the energy transfer rate for the waste heat is just not high enough with the river temperature at 90 F.
--
Better electricity: http://mdsolar.blogspot.com/2007/01/slashdot-users -selling-solar.html [blogspot.com]

Re:

[TheLink]

Sounds strange to me.

In other countries it's usually because the water _released_ will be too hot. I bet the reactors could take water in as long as it's liquid, release steam and not blow up, but the stuff in the river won't be happy.

90F is pretty cold compared to the temperatures the turbines run at, not even comparing the reactor core. I'd thought the safety margins would be higher.

If the river has too little water, then it's a bigger problem.

Re:

[Wonko the Sane]

The temperature inside your condenser is always higher than temperature of the water you send back into the river.

The temperature of your condenser is directly related to the pressure of saturated steam/condensate mixture. Higher temperatures correlate to higher pressures in the condenser.

1. Condensers are only designed to withstand a certain amount of pressure
2. The work your turbine can produce is directly proportional to the difference in pressure between the steam supply and the condenser.

Re:Reasons right?

[Dachannien]

Actually, if you really do read the article carefully, nowhere does it state that the water itself is incapable of cooling the reactor. It merely states that the river water is "too hot", which could just as well indicate that adding more warm water - especially in drought conditions where the river level is probably lower than normal - would make the river temperature too hot to safely sustain its ecosystem.

Re:

[mdsolar]

I agree. I was reading the article saying that the intake was too warm. But, another article gives more detail http://www.decaturdaily.com/decaturdaily/news/0708 17/power.shtml [decaturdaily.com] saying that it is the down stream temperature that is considered important. So, if the intake temperature exceeds the maximum down stream temperature they are hosed.

Other Options?

[pavon]

Yeah the big question to me is what other options are there for cooling a power plant other than using river water, and are they more sustainable / resilient to climate change? I don't think that underground cooling would be sufficient. I looked at how some of the desert plants operate and they too use running water - from the sewage lines of "nearby" cities, which is treated before use in the plant and then returned for reuse.

Seeing as how nuclear is really the only option we have for decreasing our power-

Re:

[Wonko the Sane]

BWRs have the advantage of NOT being Xenon-precluded because the Void coefficient of reactivity is non-existent.

What you are saying might be true for a specific reactor design, but zero void coefficient is by no means inherent to all BWRs.Not to mention that void coefficient has nothing whatsoever to do with xenon-precluded startups

River too hot?

[MMC Monster]

Why not just run the river through a refrigerator to cool it down? After all, you can generate the electricity for the refrigerator in the plant.

(I'd patent the idea, but the patent office has a silly rule regarding perpetual motion machines that gets in the way...)

Re:

[Anonymous Coward]

Why not just run the river through a refrigerator to cool it down? After all, you can generate the electricity for the refrigerator in the plant.

Actually, it would be quite possible to do such a thing and you wouldn't even violate the second law of thermodynamics since you are only pumping the heat. One example of such a mechanism is the electrically powered fan on radiators in cars that improve cooling when the car is not moving.

However, it wouldn't change the problem: Where to dump the waste heat. Inste

Re:

[NeverVotedBush]

You mean like a cooling tower already does?

Re:

[mforbes]

Think about what you're proposing. The river temp is likely in the 80s, and the air temp is in the 100+ range for the last two weeks. A radiator only exchanges heat (in this case warming the water, rather than cooling it). It doesn't cool the source flowing through the radiator unless the temperature outside the radiator is cooler than inside.

End effect: You end up with water that's even warmer than before.

Not too unusual for power plants

[Anonymous Coward]

This is not that unusual for power plants. Some coal fired units are off as well, for example Dynegy's Wabash River is currently experiencing similar problems. Obviously this hurts everyone (the company loses generation during times when wholesale power prices are high and, if load gets too high, the consumer might experience brown outs or black outs). This problem will likely get worse as well as global warming takes hold.

Re:

[FooAtWFU]

By what mechanism will global warming make rivers sooooo much warmer? I mean, I'm hearing about projections that say it will be about half a degree (C) warmer by 2030.....and, mapping this directly to the river as well, I just doubt that this sort of pathetic little increase in water temperature is enough to prevent the proper operation of their reactor (or its compliance with environmental regulations limiting how hot their cooling processes are allowed to make the river). Do you propose an alternative mec

This is the insiduous impact of Climate Change

[NeutronCowboy]

To anyone arguing that Climate Change is actually a good thing - in general, it isn't, and this is an example. Especially in the US, our entire infrastructure, agriculture and manufacturing is built and created under the assumption that things will stay the same. Pipelines in Alaska were built under the assumption that permafrost was, well, permanent. Nuclear reactors were built under the assumption that the temperature changes of rivers are known and won't change. Levies are built with certain assumptions

sounds like life

[Quadraginta]

Um...isn't this the nature of time, life, existence, et cetera? Things change. Even if there were no such thing as man-made global warming, the Sun would still vary its output, the continents would continue to drift, evolution would continue to produce new and interesting diseases, et cetera and so forth.

What do we call individuals who run their lives under the assumption that things will always stay the same? That they'll never get old or sick, that their job will never disappear or their skills become

TVA net metering policy

[mdsolar]

The cooling problem is a result of TVA's interest in building more reactors. Browns Ferry is now operating with two reactors instead of three because they recently added a reactor. They are also planning on adding a reactor upstream at Watts Bar http://www.tva.gov/news/releases/julysep07/wbu2.ht m [tva.gov] adding to the heat load on the Tennessee River. So, next time, they may have to take two Browns Ferry reactors off line at seasonal peak demand. This makes electricity more expensive because it requires buying rather than selling electricity when it is most expensive.

But, the fairly natural solution to the problem, reducing summer demand through net metering of customer generated solar power, a solution being implemented in 41 states and DC, is hampered in the TVA service territory by TVA's net metering policy: http://www.tva.gov/purpa/net_metering.htm [tva.gov] which is a billing period-by-billing period policy rather than an annual carryover policy used in net metering states. Adopting a reasonable net metering policy would allow TVA to become a summer time peak demand power exporter and gain by arbitrage, reducing the risk of higher overall rates it is building for itself by not paying attention to the capacity of the river system to handle the 60% of wasted energy nuclear power generation creates.
--
Power when you want it most: http://mdsolar.blogspot.com/2007/01/slashdot-users -selling-solar.html [blogspot.com]

Re:

[b0s0z0ku]

Can't they use air cooled condensers (aka cooling towers) rather than using river water to cool the steam directly? River water is only one way to cool a power plant.

-b.

Re:

[Wonko the Sane]

Almost always the river water is cooler than the air temperature and has a much larger specific heat capacity. If the plant was modified to run completely on air cooling, it would be far less efficient 99.9% of the time,

Re:

[b0s0z0ku]

If the plant was modified to run completely on air cooling, it would be far less efficient 99.9% of the time,

But nonetheless, there are air cooled plants that were designed as such and work just fine.

As far as river water, yes on the higher specific heat, but no on it being almost always cooler than the air -- in winter, it's normally warmer. A static body of water will have the same year around average temperature as the air, but the instantaneous temperature will lag the air temperature due to the he

Re:

[Wonko the Sane]

A static body of water will have the same year around average temperature as the air, but the instantaneous temperature will lag the air temperature due to the heat capacity of the water.

Not true; besides the effect of snow melt you mentioned there is the effect of evaporation which keeps the river cooler that the ambient air on average.

Re:

[mdsolar]

Cooling towers are usually part of the design of a power plant, but they need to be run hot enough to to get a good energy flow rate and cool enough so that steam is properly condensed. Final cooling is usually handled by the river or tidal system. Apparently what is happening here is that the cooling towers can't do the last stage. More cooling towers might help but this increases costs so looking at other options for power generation becomes important.
--
A better way: http://mdsolar.blogspot.com/2007/ [blogspot.com]

Re:

[mdsolar]

You'd save money with solar if you had proper net metering. You don't need batteries in that case. Check http://mdsolar.blogspot.com/2007/01/slashdot-users -selling-solar.html [blogspot.com] to see how things work in Georgia and Luisiana.

They avoid mentioning Global Warming...

[Asmor]

River's too hot to adequately cool their equipment, yet they're...

blaming reduced river flow as a result of drought.

Curious, no?

Re:

[mdsolar]

The drought in the southeastern US has not yet been conclusively linked to global warming. The problems described in Europe have been linked. It takes time to get that stuff figured out and it was not until the most recent IPCC report (this year) that the heat wave deaths in Europe were strongly linked. The main problem is that TVA is overloading the capacity of the river system as it is by over reliance on nuclear power so that it is increasing costs for rate payers.

Because nuclear power involves such

Renewables question....

[fantomas]

Interesting in the article that the journalist doesn't include power generated by hydroelectric dams as renewable energy...

"TVA gets about 60 percent of its electricity from coal-fired power plants, 30 percent from nuclear plants and 10 percent from its 29 hydroelectric dams. Renewable energy sources such as wind and solar account for less than 1 percent."

Any idea why that might be? Political slant? ignorance?

Umm, I mean the water flows through the dam, it goes out to sea, it evaporates, and it rains back up in the mountains and comes through the dam again. Seems pretty renewable to me.... at least some of it is coming back up through that cycle if not all...

Journalists ain't scientists

[camperdave]

Interesting in the article that the journalist doesn't include power generated by hydroelectric dams as renewable energy...

Journalists ain't scientists, and scientists ain't journalists... in general. So if you're reading something in the news that's science related, don't count on it being accurate.

Re:

[belg4mit]

It's renewable in some sense, but not others. More specfically, big hydro genereally ends up not being sustainable:
fish spawning, methane, changes to the microclimate. On the other hand, we've not done enough with run-of-river.

Re:

[Oktober Sunset]

fish spawning, methane and changes to the micro climate don't effect the dam's ability to generate electricity, so it is still renewable energy.
Renewable != earth loving hippy compatible.

Atmospheric vortex engine cooling

[Baldrson]

It sounds like its time for the nuclear industry to do some testing of the atmospheric vortex engine (see slide 18 (warning PowerPoint) [vortexengine.ca]:

• delivers the performance of a $60 million natural draft tower at the cost of a $15 million mechanical draft tower
• eliminates need for fans, saving 1% of the energy produced by a power plant
• eliminates need for tall chimney, saving 2/3 of the capital cost
• replaces conventional cooling towers
• delivers the heat to the upper atmosphere where it radiates into space
• solves probl

Browns Ferry Unit 1

[tetrahedrassface]

I have supported the restarting of Browns Ferry Unit 1 for a long time. Because despite the issues nuclear power is an immediatly available and fairly clean power source. Browns Ferry Unit 1 has had a bumpy road to travel since it was commissioned, and then shut down, and then restarted. Since its restart it has contributed clean energy at a time when the Tennessee Valley has been hammered by record high temperatures.record rainfall deficits that have severely curtailed hydroelectric production and made for conditions calling for record power demand levels.

One occurance that also recently occured at Browns Ferry [wate.com]was the automatic shutdown of the reactor due to a coolant leak. TVA reported to the NRC that an unknown amount of reactor cooling water had indeed leaked and they spent last weekend repairing it. After restart the high water temps forced this shutdown. In fact this is nothing new though. We had the Sequoyah reactor [tva.gov]using its cooling towers last year due to elevated water temps.

But yeah its been hot for sure. Also of interest is it looks like we are going to get the newest reactor in the US and that it be at Watts Bar [nrc.gov]. Unit 1 has been online there since 1996, and produces enough juice for 250,000 homes. Unit 2 at Watts Bar was roughly 80% complete when construction stopped. TVA is currently and exploring finishing the construction of Unit 2 giving us yet another clean power source. In September 2000 Watts Bar Unit 1 set a record for continuous operation of TVA reactors of similar design.

Actually...

[danwesnor]

The reactor was shut down because the water exiting the plant's cooling system exceeded an average of 90 degrees F over a 24 hour period. The plants have an agreement with the state to limit the temperature of the water they put into the river. The water in the river is not even remotely 90 degrees F.

Brown's Ferry also just recently started one of its reactors after a long downtime, so this only kicked us back a few months. It's not a big impact to the nation's grid, not even to the local area.

As for why we don't recapture the energy in the heated water to make even more power, well, they just didn't think it was necessary back when we used to build power plants back in the 60's. Investing money in anything nuclear in the US is political suicide.

Re:

[NeverVotedBush]

They are already red states. Might as well make them glowing red.

It would give a whole new meaning to Louisiana Hot Sauce...

It is about boiling rivers

[SmallFurryCreature]

It ain't about problems with the cooling itself, for that the rivers would need to be far hotter. The problem is enviromental, if you add extra heat to an already warm river you risk that it rises to the point were you destroy the eco-system. Simply put, the fishes get cooked and the algea grow out of control.

This is considered to be a bad thing.

Re:

[Sponge Bath]

...need to be engineered to carry more of the work of cooling their water

They need to be engineered in parallel with a large reservoir
to provide a more stable source of cooling water.

Re:

[Artifakt]

The Carnot cycle determines the theoretical maximum efficency of heat transfer. There are basic topside limits (In a pipe that's uncapped at the end going into the river, water can't be hotter than 100 C or it's not water anymore). Practically, all the heat exchange systems, even ones with molten sodium and such, have absolute thermal upper limits. These are usually above the sensible ecological limits, so engineers normally design for the more restrictive, environmentally safe limits.

Re:

[b0s0z0ku]

Sir we have been in a global warming cycle since the last ice age ended.

The sign of a trend (upward or downward) matters. However, so does the MAGNITUDE of the trend, and the magnitude of temperature increase has gone up over the past few decades.

-b.

Re:

[Evilest Doer]

Correlation does not imply causation.

Sigh. Learn to use actual logic instead of mindlessly quoting logical fallacies. The GP was mentioning a bunch of things, which are well known, that give a preponderance of evidence for global warming. Add to that the fact that the mechanism causing the problems are well known.

To give you an example. Someone starts screaming in public that they are going to kill you. They show up at your house with a large handgun and force the door. A couple minutes later, seve

Re:

[Ajehals]

I would hope you would parrot the rule saying "Correlation is not causation", or rather I would hope that any other alternatives are also investigated (like suicide or possibly even that a third person did the shooting) sure Its unlikely, but its worth the effort to prevent a miscarriage of justice.

How this applies to climate change though isn't all that clear. We are sure that temperatures are rising, we are fairly sure that they will continue to rise, and we are inclined to believe that the changes are b

Re:

[gardyloo]

Because "heat" is the most difficult form of energy to convert to other forms. Not difficult in an engineering sense, but difficult from a basic thermodynamics perspective. In order to convert heat into another form of energy, you have to have a reservoir available with lower heat density -- temperature. Otherwise your process won't spontaneously go (and that's the problem with energy; non-spontaneous conversion to another form only _appears_ non-spontaneous; thermodynamics guarantees that you've just overl

Quick thought

[Khyber]

Heat rises. Vertical turbines in the nuclear reactor towers might work if they could figure out how to circulate the heated water around inside the towers?

Re:Waste heat?

[Wonko the Sane]

If only it were that simple.

Imagine one of those old-style water wheels. Your question is akin to asking, "Why not figure out a way to use the energy of that flowing water without wasting it by allowing it to flow away?"

Re:

[hairykrishna]

Assuming that by 'into energy' you mean 'into electricity', I'm afraid you're running into thermodynamics limitations, the heat-steam-electricity process is about as efficient as it's going to get. It has been developed over many years, for example exiting steam is used in re-heaters to boost efficiency (along with a bunch of other neat tricks). The river is not being heated up 'unnecessarily'. You think nobody ever considered this? It's sort of the whole essence of power plant engineering...

You can claw s

Re:

[xxMSAxx]

Why not just pump it into a giant tower and we can all have hot water despite the jackass taking a 2hr shower!!!!

Re:

[sjames]

A nuclear plant is just a big heat engine like all others. Only the source of the high temperature side differs. Like all heat engines, the useful work derives from the thermal energy difference from the hot side to the cold side. If you attempt to insert a secondary stage on the "cold" side (which is still hotter than the environment), you can easily end up reducing the efficiency of the primary. Net result is twice the complexity and maintainence and no gain in energy output at all.

Re:

[Waffle Iron]

As the difference in temperature between engine input and output gets less, the physical size of the engine you'd need to create a given amount of power goes up exponentially (not exactly, but much faster than linearly anyway). This waste heat mostly comes from the steam condensers for the turbines, so the input temperature available is very low. Due to the laws of physics, a sterling engine that could significantly boost the efficiency of a nuclear plant would be too large and costly to make economic sense

Re:What "waste heat"?

[Wonko the Sane]

In practice this is an engineering problem

You misspelled "fundamental limit of thermodynamics"

Re:

[NeverVotedBush]

It would sure be nice if more people had a better grasp of basic scientific principles, wouldn't it?

Re:

[Wonko the Sane]

It's really amazing that these basic principals of thermodynamics were all figured out in the early 1800s [wikipedia.org], but almost 200 years later people still don't get it.

Re:

[mi]

In practice this is an engineering problem

You misspelled "fundamental limit of thermodynamics"

No, dear, I did not. You are struggling with the Second Law of Thermodynamics [wikipedia.org], which — in the form most applicable to the situation — is spelled as "It is impossible to convert heat completely into work."

My point was, that a better-engineered reactor would convert more energy into work. This increase of the work/heat ratio is a purely engineering problem — the only "fundamental limit of ther

Re:

[Wonko the Sane]

the only "fundamental limit of thermodynamics" is that the ratio be below 1...

Assume the reactor produces steam at a temperature of 500 fahrenheit (530 kelvin).

If the temperature of your cooling medium is 50 fahrenheit (280 Kelvin)

Your process can never be more than 47% efficient. No amount of engineering can change this fact.

Now if the temperature of your cooling medium rises to 90 fahrenheit, then you are stuck below 42%.

Thermodynamics not only says that the ratio must be below 1, it also says exactly by

Re:

[mi]

Assume the reactor produces steam at a temperature of 500 fahrenheit (530 kelvin). [...] Now if the temperature of your cooling medium rises to 90 fahrenheit, then you are stuck below 42%.

A nuclear reaction can produce much higher temperatures than that. Finding a good medium, and a good way to contain/control the reaction is an engineering problem.

Thermodynamics not only says that the ratio must be below 1, it also says exactly by how much it must be below 1.

Uhm, no, it does not. The equation you are r

Re:

[Wonko the Sane]

A nuclear reaction can produce much higher temperatures than that. Finding a good medium, and a good way to contain/control the reaction is an engineering problem.

Yes, you can engineer reactors to produce steam at higher temperatures.

As the "spent" medium is hotter than fresh (and it always is), its heat could be used again in another cycle. And so on (assuming "endless" supply of fresh medium, which river provides), until the difference in temperatures make another cycle impractical. This is how efficiency

Re:What "waste heat"?

[Wonko the Sane]

A carnot cycle [wikipedia.org] is indeed a closed cycle, but:

Carnot's theorem is a formal statement of this fact: No engine operating between two heat reservoirs can be more efficient than a Carnot engine operating between the same reservoirs.

Your open-cycle system will never be more efficient than a carnot cycle at the same temperatures.

Re:What "waste heat"?

[SEMW]

I'm afraid Wonko's right. The total efficiency converges to Carnot's. If there is any *usable* waste heat left at the end of a cycle to put into another heat engine, then the first cycle wasn't running at full (reversible) Carnot efficiency.

BTW, if a heat engine were ever to be used in a closed system, then its efficiency would quickly converge to 0%, since the hot source would cool down and the cold source would heat up! The Carnot cycle, as I said in my other post, assumes infinite, constant temperature hot and cold sources, i.e. effectively the same as a system where heat is constantly added to the hot source (by a nuclear reactor) and taken away from the cold source (by a running river) to maintain a constant temperature.

Re:

[NeverVotedBush]

Mi - Wonko and SMNW are both right and know their Carnot cycle, thermodynamics, etc.

If you want to continue to beat this dead horse, I think your best bet would be to educate yourself about thermodynamics, the Carnot cycle, and what it means to have inifinite temperature reservoirs.

Just as real world efficiencies can only approach the Carnot cycle, your answers can only approach the previous postings as you learn more about what you are talking about.

Re:

[mdsolar]

Thanks. I do know the difference but often fail to catch the error.

The overly-simplified solution

[westlake]

Eliminate nuclear and coal power in favor of solar and wind power, and replace the stupid cars with bikes.

The bicycle as a commuter vehicle works only under ideal conditions and only for the young and fit. You won't be taking a bicycle into Buffalo, NY in mid-winter. You won't be taking a bicycle into Houston, TX in mid-summer.

Re:

[sessamoid]

The bicycle as a commuter vehicle works only under ideal conditions and only for the young and fit. You won't be taking a bicycle into Buffalo, NY in mid-winter. You won't be taking a bicycle into Houston, TX in mid-summer.

Bollocks. Go visit the Netherlands. Or Seattle for that matter. Lots of old people commuting on bicycles in the Netherlands, and it rains a hell of a lot there. It doesn't freeze there, but there are plenty of places in the US that bicycle commuting would be viable if we had the infrast

Re:

[Guppy06]

"Before air conditioning, yankees stayed in yankeeland. After air conditioning they moved to places where they weren't welcome."

Actually, refrigeration technology took off in the South before the North. The Yankees you so deride didn't need large plants to manufacture ice for their iceboxes, they had the Great Lakes.

As for electricity generation, you'll note that the New Deal and the Tennessee Valley Authority (TVA in TFA) was interested in improving electricity generation in the South long before consumer

Re:Air conditioning ruined the South

[couchslug]

"The South never had a "carbon footprint" before yankee glutons moved to Miami and Atlanta."

It sure burned the heck out of wood, Bo! The spelling is "Yankee gluttons", BTW.

"Most of us grew up without air conditioning and were happy that way. We used clothes lines to hang and dry our clothes, not electric driers. Life was good."

HAHAHAHA! When I see local folks volunteering to go back to an AC-free life I'll buy the connection between "no AC" and "happiness".
I still use clothes lines to dry clothes (clothes smell fresher besides the energy savings), but there is good reason AC is popular among non-Yankees. I don't see any nostalgia for doing washing in wooden tubs and ironing it with (aptly named) "sad irons" either. The tubs are planters and the irons are doorstops, the shotgun shacks whose layout helped somewhat with cooling are empty, and (most) of the people don't look the the folks in a James Agee book.

I'm a "Damn Yankee" (the ones that came and stayed) myself, though I'm far more genuinely countrified (and right wing) than most locals.

If you wanted to keep out the sort of Yankees that wouldn't fit, not selling them everything at fire-sale prices would have done it. The Southeast got rich and is getting richer by urban and suburban sprawl, so if ya want things the way they used to be, move into the Deep South and away from the coast.