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Post by eclipse on Jun 7, 2012 21:12:51 GMT 9.5
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Post by anonposter on Jun 7, 2012 23:02:41 GMT 9.5
Cooling towers aren't that expensive (at least compared with the rest of the power plant) and could be retrofitted onto plants which don't have them (and the Gen IV reactors which will probably end up doing most of the work of solving global warming will be able to be air cooled). Putting new power plants nearer the coast is probably also going to turn out to be a good idea (could also use them for desalination as well).
It's also possible that we'll just end up deciding that having the plant operating is more important than the temperature of the water discharged. Piping water from elsewhere whilst a bit expensive might also be a possible solution. MODERATOR Please supply links/refs to support your assertion. Thankyou.
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Post by eclipse on Jun 9, 2012 22:26:48 GMT 9.5
My friend replies.... *******
Do you have any links to credible discussions of air-cooled reactors?
"Putting new power plants nearer the coast is probably also going to turn out to be a good idea" Near the coast, but high enough to avoid SLR for the next hundred+ years... (12 of 19 of the UK's current nuclear sites are vulnerable to SLR as well as dozens of US sites).
"deciding that having the plant operating is more important than the temperature of the water discharged" So, more important for us to keep our plasma TVs on than to have any living fish downstream? The temperature limits on water discharge are there for a reason.
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Post by anonposter on Jun 9, 2012 23:57:37 GMT 9.5
Do you have any links to credible discussions of air-cooled reactors? The possibility of air cooling seems to be mainly mentioned in passing with regard to higher temperature reactors. Though I understand that PRISM was designed to be air-cooled. Near the coast, but high enough to avoid SLR for the next hundred+ years... (12 of 19 of the UK's current nuclear sites are vulnerable to SLR as well as dozens of US sites). That would probably mean at least a few metres high, this might mean putting it a few kilometres inland and running pipes (or even just digging a canal) to the shore (should be doable). Building a wall around the plant to hold out the water might also work. So, more important for us to keep our plasma TVs on than to have any living fish downstream? The temperature limits on water discharge are there for a reason. To most people, yes it is more important to keep the plasma TVs on (i.e. if you want the limits to still exist you'll need to find a way to meet the power demand without needing to exceed them).
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Post by eclipse on Jun 10, 2012 14:12:22 GMT 9.5
So any links to the PRISM reactors having air-cooling? I tried the wiki but it didn't seem to mention what kind of cooling tower they would use.
PS: Thanks for all your help on this, I really appreciate it.
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Post by quokka on Jun 10, 2012 15:37:27 GMT 9.5
The B&W mPower SMR can use air or water cooling. See last paragraph on the brochure for mention of air cooling. www.bechtel.com/assets/files/news/bw/mPower.pdfI think most of the SMRs under development are intended to be used (optionally) with air cooled condensers.
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Post by Graham Palmer on Jun 10, 2012 18:51:37 GMT 9.5
I note that the Nature article was a discussion of all thermal plants, including coal, nuclear, steam-cycle gas, (and although not explicitly stated) also biomass, and solar thermal. Water cooling via evaporation is used because it is the most efficient and practical way to remove waste heat, hence the reason for all those water cooling towers on the top of city buildings which cool the condenser of the air-conditioning systems. Water cooling is used despite the increased regulatory and maintenance requirements due to the performance in a limited area, but air-cooling is still widely used of course for air-conditioning.
Of all the thermal plants, nuclear is the least limited in terms of siting (compare solar thermal - must be a long way inland to avoid high humidity and cloud cover, and usually arid/semi-arid) and is the most suited to large-scale desal. For all thermal plants, there is no fundamental reason why low-water use cooling can't be accommodated in a context of reduced water availability, but at lower efficiency. My interpretation is that, of all the thermal plants, water shortage clearly falls in favour of nuclear.
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Post by eclipse on Jun 10, 2012 21:34:10 GMT 9.5
Excellent point.
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Post by anonposter on Jun 11, 2012 12:34:00 GMT 9.5
On the subject of PRISM it was a while ago since I last read something that went into depth about it (i.e. I don't actually have any links) but it did say it was designed to be underground sited and with air cooling.
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Post by David B. Benson on Jun 17, 2012 15:10:45 GMT 9.5
I see no obstacles to refitting any NPP with air cooling. The only effect is a lower net thermal efficiency which hardly matters for an NPP.
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Post by anonposter on Jun 17, 2012 20:33:39 GMT 9.5
Lower thermal efficiency does mean a power downrate (at least if you keep thermal power the same).
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Post by grlcowan on Jun 18, 2012 6:14:30 GMT 9.5
The THTR-300 power station was air-cooled.
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Post by David B. Benson on Jun 19, 2012 12:42:21 GMT 9.5
Yes I should have stated a lower net power rating. With air cooling some of the electricity is used to run the fans.
Holcomb's new SMR is designed to have air cooling as an option.
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Post by David Walters on Jun 21, 2012 23:56:15 GMT 9.5
Folks, you're drifting. The issue is existing thermal plants, most notably nuclear, and what can be done given expected increases in inlet cooling temperatures/higher outlet temperatures for once through cooling.
High temp reactors are years away, a decade at least, from mass deployment. Hight temp reactors of the brayton cycle can do *well* with air cooling. The effiecncy hit for a nuke would be around 8% of generation I'd calculate. Very high, very expensive.
I see cooling towers with natural draft air flow as the most natural fix to this issue.
France should expand their very few coast side plants with multi unit parks.
David
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Post by cyrilr on Jun 22, 2012 2:01:03 GMT 9.5
This is another silly argument not well thought through by the anti-nukes.
It is not hard to build cooling towers if necessary. We're talking decades long times to decide what to do.
It is also not hard to add more seawater pumps to do more water flow for once through cooling. This means you get the same water temperature discharge. The hidden notion is apparently that we can't add a few more pumps to nuclear plants. Which is absurd. It shows how poorly devised the anti nuclear/nuclear hyperbole arguments are.
Decades is a long time to do anything, such as building dikes. I live in the Netherlands, below seawater level. It is not hard for us to add height and weight to the dikes and engineered protections. The only nuclear plant we have can take a much higher level of seawater rise than the worst case IPCC scenarios of 2080.
The problem will not be with nuclear plants. It will be with poor countries that can't afford expensive dikes and engineered seawalls. Such as Bangladesh. But no one cares about Bangladesh because Bangladesh has no nuclear plants.
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Post by David B. Benson on Jun 25, 2012 9:26:09 GMT 9.5
Bangladesh is in some stage of having a Russian built NPP.
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Post by eclipse on Aug 14, 2012 21:02:28 GMT 9.5
Here is another one. HARTFORD, Conn. (AP) — Connecticut's nuclear power plant shut one of two units on Sunday because seawater used to cool down the plant is too warm.
Unit 2 of Millstone Power Station has occasionally shut for maintenance or other issues, but in its 37-year history it has never gone down due to excessively warm water, spokesman Ken Holt said on Monday.
Water from Long Island Sound is used to cool key components of the plant and is discharged back into the sound. The water cannot be warmer than 75 degrees and following the hottest July on record has been averaging 1.7 degrees above the limit, the Nuclear Regulatory Commission said. www.seattlepi.com/business/article/Warm-seawater-forces-Conn-nuclear-plant-shutdown-3784259.php
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Post by trag on Aug 16, 2012 4:21:54 GMT 9.5
Here is another one. HARTFORD, Conn. (AP) — Connecticut's nuclear power plant shut one of two units on Sunday because seawater used to cool down the plant is too warm.
The water cannot be warmer than 75 degrees and following the hottest July on record has been averaging 1.7 degrees above the limit, the Nuclear Regulatory Commission said. Any idea whether that temperature limit is a technical limit or an environmental quality limit? In other words, does the plant actually have trouble with water at that high a temperature, or is it just that they aren't allowed to add more heat to an already overhot body of water? I also note that the publication is quoting from a UCS representative as if they were a disinterested authority on the topic. NPR in the USA has also done that a number of times. It's irritating. How is the UCS managing to worm its way into the media as anything other than an advocacy group?
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Post by David Walters on Aug 16, 2012 6:18:05 GMT 9.5
My view on this.
I worked in power plants with thermal limits placed on them for water temp.
Most water temp regulations, like with heavily river-cooled French reactors are primarily regulatory issues that can be adjusted upward. It's political and not unimportant, but it is not an engineering limitation.
The real problem is when inlet water temps really go high and one has to curtail the unit. But they can still run. This happened to my plant a few times every year based on salt-water/bay water cooling temps during extra low tides. Load in these cases is completely a function of maintaining back pressure/vacuum on the low end of the turbine. You can also get into bearing cooling water problems which are cooled with the same seawater (directly or indirectly through a HX).
Towers: don't like 'em. They actually consume a lot of water and this becomes an issue. There are major restriction on how much power plants consume, as opposed to use. Reservoir extention/expansion is a much better way to go and provides water for recreation (fishing!) and irrigation if really needed. Thus it simply extends the once-through cooling for river water based nukes.
Ocean. Oceans are the best as the ultimate sink. They are simply always cold and even with global warming, temperatures here are expected to rise at a lower rate than overall atmospheric temps.
No one has run a large ranking turbine on air. It can be done but you are talking a 5 to 10% efficiency stab. Go to you nearest combined cycle power plant and ask to see the air-cooled condensers. You can see them on any google statelite photo. A very long row of towers with fans on top. each fan the size of a Huey helicopter blade. Now, multiply this by a factor of 10 and you will see your future AP1000 cooling towers used for air cooled condensers. Huge.
David
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Post by David B. Benson on Aug 16, 2012 10:12:01 GMT 9.5
trag --- I'm reasonably certain that there is some maximum cooling water temperature beyond which the condenser fails to function properly.
David Walters --- I've read an account of the experience of the plant operator running a coal burner with air cooling for the Rankine cycle. The plant is somewhere in Europe. The report indicated that the operator was quite happy with the performance, being somewhat more reliable the the water cooled coal burner that he had run earlier in his career.
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Post by quokka on Aug 16, 2012 15:16:23 GMT 9.5
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Post by BGS on Aug 16, 2012 20:50:17 GMT 9.5
I am the friend that Eclipse mentioned above. Thanks for your replies to my queries. Please note, I am not anti-nuclear. My comments about water cooling are genuine questions seeking to understand the possibilities and limits of power generation from a non-technical expert.
A couple of comments in reply to David Walters:
"Most water temp regulations, like with heavily river-cooled French reactors are primarily regulatory issues that can be adjusted upward. It's political and not unimportant, but it is not an engineering limitation."
I'm afraid this is not true. These are not merely political limits. Yes, they are defined politically, but such political decisions are (or ought to be) made on the basis of hard ecological limits. Above certain temperatures marine creatures die. Once temperatures rise above certain non-negotiable biophysical limits, operating a thermal plant becomes a choice: temporary downtime for plant or dead river (with basically zero possibility of returning the ecosystem to how it was, even if a new (generally less complex and productive))? Our political system has decided that the dead river is worse than temporary loss of power from a plant.
"Oceans are the best as the ultimate sink. They are simply always cold" That's what I thought - until the article above. There are also biophysical limits to water temperatures in ocean ecosystems. While it is true that the oceans are a far, far greater heat sink than rivers or lakes, their capacity is not infinite and rising ocean temperatures are already having devastating effects on marine ecosystems around the planet. Warmer oceans raise the baseline from which local heat events become threatening.
As for sea level rise, yes, it is likely to be slow and sea defences are possible. But they are expensive. If more new plants are going to be situated near coasts rather than inland waterways due to concerns about rising water temps, then the costs of sea defences needs to be included in planning considerations from the outset (alternatively and/or additionally, the cost of cooling towers as well).
Also remember that the IPCC AR4 sea level rise predictions explicitly excluded "future changes in dynamical ice flow" and so were known at the time to underestimate likely SLR by a considerable (but then unknown) margin. More recent studies suggest that something like double the upper margin mentioned in the AR4 is fairly middle of the range, and remember (perhaps counterintuitively) this is not distributed evenly around the globe, so some places will see considerably more than this. This field of research continues to be very active and of much interest. Recent events in Greenland and the Arctic continue to exceed modelled outcomes.
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Post by BGS on Aug 16, 2012 20:54:10 GMT 9.5
Oops - dropped the end of a sentence.
"even if a new (generally less complex and productive) ecosystem is re-established"
I.e. It is widely recognised within ecology that once ecosystem complexity has been diminished, it is not usually very easy or quick for it to return. Complexity usually correlates with productivity. So once you overcook a river or lake system, the ecological damage is generally long-lasting.
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Post by anonposter on Aug 16, 2012 21:01:36 GMT 9.5
Our political system has decided that the dead river is worse than temporary loss of power from a plant. Mainly because other power plants can step in to fill the load, if that weren't the case then the priorities of the political system could be rather different.
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Post by davidm on Aug 17, 2012 0:59:05 GMT 9.5
Our political system has decided that the dead river is worse than temporary loss of power from a plant. Mainly because other power plants can step in to fill the load, if that weren't the case then the priorities of the political system could be rather different. If the heat problem covered a broad region like we have seen in the US, but at a higher heat level, where would the other power sources come from?
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Post by proteos on Aug 17, 2012 5:48:20 GMT 9.5
Just to add my 2 cents. As said by Graham Plamer, this problem can affect all thermal power plants. Thermal plants are in effect all we can build in the way of dispatchable capacity bar hydro (which in Europe is pretty much maxed out). To put things in perspective, during a parliamentary hearing (french only, sorry), someone reminded french senators, that during the 2003 heat wave, out of 13 requested exemptions, 6 were for non-nuclear power plants. And most french nuclear plants on riversides are already using cooling towers of course. The only riverside nuclear power plant that has none is Fessenheim. The question can be turned in many ways: but in the end if push came to shove, despite having adopted all technical measures to lower the temperature of the discharged water, the temperature would be above the limit for aquatic life with the plant running, a choice would have to be made: should it be Grand'ma or the fishes that should die because of the heat wave? In that case, my bet is that grand'ma's life will be chosen over the fishes'. We should also remember that if those cases keep coming up ecosystems will change in the vicinity of the plant. And organisms that cope with warmer waters will come from warmer parts of the world. It is what is going to happen anyway because of climate change by the way.
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Post by David B. Benson on Aug 17, 2012 7:27:08 GMT 9.5
David M --- ERCOT, the Texas grid has little interconnection to other grids. As water becomes increasingly unavailable in Texas it may well be necessary to add air cooling to the thermal generators.
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Post by davidm on Aug 17, 2012 11:44:05 GMT 9.5
David M --- ERCOT, the Texas grid has little interconnection to other grids. As water becomes increasingly unavailable in Texas it may well be necessary to add air cooling to the thermal generators. Hmmm, it would seem to me if you could do air cooling of thermal generators in Texas you could do it just about anywhere. This does raise a question I brought up on one of the preforum comment sections which I still lack clarity on. We know that increased solar radiation warms the oceans creating increased water vapor and CO2, generating in turn their own positive feedbacks. In principle why is that any different from heat generated from any fossil fuel or nuclear source. Since the effect of solar radiation and heat waste would seem to be the same I'm not as yet comfortable with the response I got that seemed to say they are different, with the latter being trivial in its effects. Okay I checked it out on skeptical science. Waste heat makes about a 1% contribution to global warming. www.skepticalscience.com/waste-heat-global-warming.htmStill I assume waste heat operates like a surrogate sun, releasing stored ghg.
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Post by David B. Benson on Aug 17, 2012 11:57:38 GMT 9.5
David M --- Running the numbers does indeed show that reject heat loss is a triviality.
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Post by eclipse on Aug 18, 2012 12:04:42 GMT 9.5
David M --- Running the numbers does indeed show that reject heat loss is a triviality. Trivial, for now. If we keep growing the economy at 2.3% per year for 400 years the planet would reach boiling temperature just from the waste heat from thermal plants. At that 2.3% growth rate, we would be using energy at a rate corresponding to the total solar input striking Earth in a little over 400 years. We would consume something comparable to the entire sun in 1400 years from now. By 2500 years, we would use energy at the rate of the entire Milky Way galaxy—100 billion stars! I think you can see the absurdity of continued energy growth. 2500 years is not that long, from a historical perspective. We know what we were doing 2500 years ago. I think I know what we’re not going to be doing 2500 years hence. physics.ucsd.edu/do-the-math/2012/04/economist-meets-physicist/
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