If you're talking about end of the pipe immediate ecological impact (or ecological alteration depending how you look at it) nuclear may have even hydro beat... some warm water effluent and steam may due less ecological harm than altering a whole river ecosystem (i.e. changing a flowing river into a ponded resevoir) as most dams do.  Another benefit is bang for ecological footprint... nukes take up relatively little space to create relatively large amounts of power (100s of megawatts on few acres).. Though, there's always that nagging radio-actve potential.  Also, uranium mining is damaging similarly to coal mining (perhaps even moreso?). Also, it's my understanding that we could stretch the nuke-fuel by reconstituting the spent fuel as they do in Europe.  

puh-leeze.  what kind of environmentalist can't say "neither?"  oh, right, you have actually highlighted one of the biggest greenwashing scams being perpetrated by so-called "green" politicians and "environmentalists!"

here's a little tip:  ALL REMOTE GENERATION AND TRANSMISSION ON PREVIOUSLY UNDEVELOPED LAND IS BLACK, NOT GREEN, SO WE ALL NEED TO OPPOSE IT.  PERIOD.

i am, of course, in favor of giving all the "renewable energy" subsidies, tax breaks, low-interest financing and guaranteed power buy-backs - which are currently being traded for bribes from Big Power to our government - to US, AS INDIVIDUAL LOCAL DECENTRALIZED POWER GENERATORS ON OUR HOMES AND BUSINESSES.

trouble is, Sierra Club, NRDC, and several other fake environmentalists seem to think that dynamiting, bulldozing, paving over, developing and poisoning wilderness for utility profits from remote power generation and long-distance transmission is somehow the best way to do things.  kind of like deforesting the amazon, bleaching coral reefs and demolishing old-growth forests is the right way to do things, eh?

time to stop the FAKE ARGUMENTS and get down to WHAT IS BEST.  nobody can deny that paying folks a great price for totally clean and green power they generate is best, so let's just give a flat NO to everything else, including anything that kills wilderness.  NO MORE HALF-STEPPING TO PROFIT BIG POWER.  they had their moment - now it's our turn.

Umbra deserves recognition and thanks for her brilliant answer to the person who asked her whether it was better to die by guns or knives. (The late John Gofman gets credit for that, not me, but it is still good). To amplify a bit for the writer: we need to stress that nuclear power plants will not be capable of solving the global warming problem in the requisite time frame, nor can the billions of dollars required be justified since the same money, if applied to wind energy and efficiency,  would reduce our reliance on fossil fuels far more quickly. Furthermore, nukes only provide electricity (about 20% of our TOTAL electric demand), whereas our major problem lies in the field of liquid fuels, which are used for industry, transportation and home and commercial heating. So nukes are essentially useless to solve the global warming problem, aside from the huge dangers that Umbra so well describes. We won't get the right answers unless we ask the right questions!

one nuke vs coal issue you don't hear much is that of the embodied energy of the nuke plant itself, because the plant is made of a whole lot of concrete and concrete requires a whole lot of energy to make.  The numbers I heard were that building the nuke plant uses so much concrete that the greenhouse gases emitted in its concrete production won't begin to be offset by the non-greenhouse gas electricity it produces  for 20 years.  That is, the plant doesn't become carbon neutral for 20 years.   While I haven't verified those numbers (maybe you can, Umbra?) they make a lot of sense from what I know about embodied energy and concrete production.  

another less-bandied issue is that of opportunity costs.   Nuke is SO expensive (even not including the costs the government takes on for regulation, covering risks, paying for the eventual storage of  waste whenever we actually do it., etc, etc..) that we can get a lot more benefits from that money ($/KWHr) by putting it into other options like energy  efficiency  (now about 3-5cents/kw) and wind power (now cost competitive with natural gas powered electricity).  Both of these are obviously safer and cleaner.

Good answer.  Would have liked to see a little more about the best alternative: EE - energy efficiency.  The less you use, the less these plants get used, the fewer get built.

Unfortunately, nukes run all the time (except when they are shut down to disgorge their toxic fuel onto the local landscape), so you won't effect them much - and coal plants are so cheap (because the true costs to public health and natural resources etc. are not measured or charged for) that they are pretty much first on to the grid as well.

But if we can really cut down our hunger for electrons, we can make a difference.

I really think nukes are worse, because of the amount of CO2 released in construction (as triskele notes above) and in taking care of the spent fuel, and the GHGs released during fuel processing, and in "decommissioning" - and because they really are trying to make a case for being OK, which coal plants don't have a shot at doing.  But I'm happy to settle for "neither".

Given the magnitude of possible harm climate change could cause, I don't think we can dismiss nuclear as an option so easily. If you ask why the average American produces 22 tonnes of greenhouse gases a year while the average person in France produces 8.7, nuclear power is a big part of the answer.

One other aspect to consider in this false dichotomy is the time it takes to implement these plans.  It takes 3-5 or more years to bring a major power plant online, and much longer for nuclear because of all the safety regulations that apply.  Energy efficiency projects are the fastest way to match supply and demand, with many forms of renewable power also being quicker than a big coal plant.  So for people who are in a hurry to put up nuke plants, they should face the fact that a 4 year presidential term isn't long enough to bring them along and the project might well be squashed before they're done, while investing in efficiency or renewables works faster to solve the problem.

Don't know why this is such a challenge.  The answer is neither and will always be neither but that's not what you say.  You can talk about trading clean air for coal power, or water supply for nukes until you're blue in the face, but I don't believe in presenting problems without solutions.  Explain how geothermal, solar and hydro can reduce the need for baseload capacatiy, which means we won't need more coal or nuclear which both have major drawbacks.  Talk about conservation, that the cheapest power is what we dont' use.  Explain that more than 50% of energy used in homes is from appliances NOT being used...but for pete's sake don't get stuck in the mud!!!  It doesn't matter which came first chicken, egg, nuclear waste or global warming we need to be solution oriented.

I have replaced all my lights with CFL, have no air conditioning or electric heat, and have a solar water heater and my electric consumption is still over 1500 kwhr/mo.  My employer has replaced the old electric motors with the high efficiency ones and have speed controllers on them.  We have installed high efficiency lighting and still suck a megawatt out of the grid.  What do we tell all these employees, "Sorry you have no job because there in not electricity today"?  Not everyone can be a internet column writer.  Manufacturing jobs are the best paying jobs for most of blue collar America.  The only way to provide the massive amounts of power for industry is with large power plants and the least damaging ones are nuclear.  
PS Nuclear was can be recycled into new fuel reducing the waste by 98%.

Bravo! We do not have to choose between two evils.  Indeed, the only way our society is going to start thinking and acting creatively when it comes to power is if we take these dreadful options off the table.  
One tour around the coalfields of Appalachia, or a trip through the Hanford Nuclear Reservation will show you that the terrible consequences of these forms of power are not just abstract notions of looming disasters and carbon emissions.  Coal and nuclear have devastated the American landscape. And they will continue to do so until there is a drastic change in U.S. energy policy.  That change, for better or worse, will start with us, as individuals.  There are better options, as Grist readers know: efficiency, conservation, solar, wind, geothermal, even hydro. We need to choose them - all of them - in order to take coal and nuclear out of the picture.

Great damage has been done, but we still have 8 years before natural positive
feedbacks lead to our extinction.   Sea level will continue to rise even if we
disappear right now, but that is "minor" compared to poison gas bubbling out of
the ocean and killing almost everything including all of the people.
See the chart on page 274 of "Six Degrees" by Mark Lynas.   We have until 2015
to BEGIN REDUCING our total CO2 output and we have until 2050 to actually
reduce our CO2 output by 90%.   The curve has to start down by 2015, not we
have to think about it by then.   The peak of our CO2 production has to happen in
the next 8 years.  
How are YOU going to do it?   Go ahead and invest YOUR money.

If we don't follow the schedule in Six Degrees, we will encounter positive
feedbacks which will take the control of the climate out of our hands.  
Civilization may fall anyway well before 2050, but we can avoid going extinct by
2100.   We have to hold the CO2 level to 400 parts per million to have a 75%
chance of avoiding the positive feedbacks.   The natural positive feedbacks are
explained in Six Degrees.

We don't recycle nuclear fuel because spent fuel is valuable and people steal it.  
The place it went that it wasn't supposed to go to is Israel.   This happened in a
small town near Pittsburgh, PA circa 1970.   A company called Numec was in the
business of reprocessing nuclear fuel.   I almost took a job there, designing a
nuclear battery for a heart pacemaker.   [A nuclear battery would have the
advantage of lasting many times as long as any other battery, eliminating many
surgeries to replace batteries.]   Numec did NOT have a reactor.   Numec "lost"
half a ton of enriched uranium.   It wound up in Israel.   The Israelis have fueled
both their nuclear power plants and their nuclear weapons by stealing nuclear
"waste."   It could work for any other country, such as Iran or the United States.  
It is only when you don't have access to nuclear "waste" that you have to do the
difficult process of enriching uranium, unless you have a Canadian "Candu"
reactor that runs on unenriched uranium.  
Numec is no longer in business.   The reprocessing of nuclear fuel in the US
stopped.   That was the only politically possible solution at that time, given that
private corporations did the reprocessing.   My solution would be to reprocess the
fuel at a Government Owned Government Operated [GOGO] facility.   At a
GOGO plant, bureaucracy and the multiplicity of ethnicity and religion would
disable the transportation of uranium to Israel or to any unauthorized place.  
Nothing heavier than a secret would get out.

OK, in the best of all possible worlds we would dismantle all our coal-fired and nuclear generators and get by on renewables and natural gas fired plants, which together amount to about 30% of US generation right now.  We can improve conservation and reduce per capita consumption by maybe 3% per year (still pretty aggressive), but people still keep having babies and immigrants keep coming in so total electric emissions are going to be very hard to reduce in absolute terms. Even CA hasn't been able to do it yet, despite the most aggressive energy efficiency programs in the nation.

So what is our transition fuel to keep CO2 from balooning in the next few decades? It had better be nuclear, and we had better get with the Europeans and settle on failsafe designs that allow waste reprocessing at lower costs than current designs, or we are, as they say, cooked.

The good news is all that concrete can be made with way less greenhouse gas emissions, by using - guess what - coal flyash and also slag in up to 50% in the mix, it even increases the strength of the concrete (and the cure time).

Wind is lovely (except to that idiot senator from MA), but also unpredictable, except in CA where it always peaks in the middle of the night and requires billion-dollar transmission lines to get it to where the load is. And yes, those transmission lines take 10 yrs to plan and build because of NIMBYism (among other things), just like a nuke plant.

We are not going to survive as a species without going full court press on ALL the low-GHG technologies, and that includes nuclear. Carbon capture is a lot further off, so for the next 10 years I'd "just say no" to new coal plants.

This too is a false dichotomy. The answer to conservation is keep at it.  The 2 percent solution to global warming being advocated by Sierra Club involves taking steps each year to continue to reduce your consumption demand.  You've done a lot already, congratulations!  Look at closing the loop in your production process to reduce or eliminate waste generation. Reuse stuff to avoid it becoming waste. Have you eliminated disposable packaging waste in your products? Have you worked with suppliers to do the same on your raw materials? Do you use sustainable raw materials?  Is there a way to make your product with less embodied energy? When you've done that iteration for this year, offset your consumption with green tags.  Sell your product to customers and employees as sustainable and green-based.  Most of the time the answers to more progress are right under your nose, in your own employees brains. Empower them to help make more changes in the workplace to advance the effort. Your culture will be one of inspiring sustainability, and you will have no problems retaining and inspiring workers and investors.  Understand the links to sustainability and the triple bottom line in your company operations.  Quantify and report your efforts to investors, in a meaningful way.  Look at the Dow Jones Sustainability Index for more clues on how you may focus efforts.  Realize we are all on a continuum and sustainability is a goal, rarely a complete destination.
Renewable (preferably, local, distributed) energy is the only correct answer to the question being posed to Umbra.

A decent wriggle would at least have provided this important fact:  the whole nuclear life cycle, including energy-intensive enrichment and energy-intensive concrete/steel production has been evaluated at between 30 and 60 grams of CO2 per kWh of electricity produced ... not far from what wind turbines do in terms of CO2.  

Coal directly emits about a kilo of CO2 (1,000 grams) per kWh, and that's WITHOUT a full life-cycle analysis (energy in mining, energy in transporting, handling fly ash, etc.).  

In addition, coal emits a witches brew of radioactive and nonradioactive toxins, especially mercury -- and this after requiring mountaintop removal to get at the coal.  

At least the nuclear waste starts in a contained space; the radioactive materials released from coal are nicely distributed throughout the atmosphere and enter the food chain in many places.

Both plants produce the same thermal pollution to rivers or put the same amount of water into the atmosphere from cooling towers.

Given a stable climate, we can work on solutions to nuclear waste; destabilize the atmosphere and there base of our food chain (acidify the oceans) and it's game over.

The "guns or knives" is a cute rhetorical device, but an easy choice when you recognize that coal is a machine gun firing at us while we're in a phone booth; the nuclear knife is a probabilistic knife that may not turn out to be used against us at all.

It's true that we must respond to climate change must faster than nukes can be built (if they can be built at all) to respond, so they are actually kind of irrelevant -- but many folks run around saying we should shut down existing nukes, even at the cost of seeing a coal burner built in its stead.  That is truly insane.

Bottom line is that, in priority order, we must get rid of all the coal plants, starting in efficiency order (or, in inefficiency order actually).  Once we've shown we can conserve and boost our efficiency enough to shut down all the coal plants, then we can continue by closing nukes if we wish.

So, no, your wriggle is bunk.  There is a clear order to what we have to do if we want to survive.

Nuclear power is clean, safe and the waste problem only exists thanks to enviro-extremists.
Coal inputs radioactive waste directly into the atmosphere as a matter of course. Coal releases radioactive carbon isotopes, as well trace amounts of uranium. Both end up in forms that can enter the environment and be metabolized. Nuclear power plants do not do this.
The latest enviro-obsession over apocalyptic climate change is a distraction that will only serve to waste yet more time and money getting to clean power.

I have one question for you: could you tell us please of these Israeli nuclear power plants ? point them out ? If you could prove they exist, I would believe your facts. unfortunate for you, you can't. Israel doesn't have nuclear power plants. our entire grid runs on Fuel Oil and Diesel, currently. in the near future gas will be in the picture. regrettably, we have nuclear weapons research, development and building facilities. I agree with you totally on the subject of the spread of nukes to other countries, but an Israeli nuclear power plant just doesn't exist, although many times they were proposed. the main reason is the cost, which is huge for a small country with a history of sub-par safety culture.
by the way, if you're so concerned with the spread of nukes, how come you didn't mentioned Pakistan ? or do you have a hidden agenda that you would like to share with the group?
I would like to make it clear that I am against nuclear weapons and their development everywhere in the world including my homeland, and I'm certainly against nuclear or coal power plants. I believe that saving power is the immediate desired solution.
good day lier.

It is a false choice.

First of all they are both antiquated thermoelectric technologies; one burns coal and oil, one splits atoms. Coal is about 40% thermally efficient or 60% waste heat, nuclear is about 33% efficient, dumping most of its heat from the fission reaction into the atmosphere or water. The Coal,Oil Nuclear (CON)job is run by pretty much the same club as demonstrated by Cheney's secret meetings early in Bush Administration. They have already agreed as to how to cut the pie, including by war---without cutting each other out.

The same corporations are looking to burn more of it all, not displace one for the other. Take for example, nuclear power is proposed to increase oil production from the Canadian tar sands of Alberta to Saudia Arabia.

Like, choose one:
a) global warming
b) global warming and nuclear winter
c) none of the above

In fact, the nuclear choice increases the chances of having both global warming and nuclear winter.

First of all, nuclear power is such an economic loser that it takes governments, not markets, to finance and build them. Here, there, and everywhere. The massive investment to build enough reactors to displace significant levels of carbon would not only squander enormous resources that could go toward quicker, cheaper, safer, cleaner renewables but would also waste what precious little time is left. All this on an industry already historically notorious for its ridiculously high cost overruns and failure to meet completion on time, if at all. In the US, as many nuclear reactor projects were cancelled as completed.

Secondly, the nuke industry is shot full of so many holes that it looks like swiss cheese; no accepted longterm nuclear waste facility anywhere in the world; increasingly deteriorating and unsafe reactor operations; domestic pre-deployed weapons of mass destruction; a internal threat to civil liberities and democratic society; and most importantly, the easiest way to build the nuclear bomb is to construct the atomic power infrastructure around it.

More nuclear power means more nuclear weapons materials around the world. Thirteen Middle East countries are bidding on nuclear power today---loading the region with nuclear materials ostensibly for electricity and atomic bombs.  The United States Nuclear Regulatory Commission is actively promoting nuclear infrastructure around the world including the military regime of Burma.

Recent scientific studies using NASA climate change models show that a limited nuclear war between Pakistan and India involving a total of 100 Hiroshima-sized bombs would loft enough smoke into the stratosphere to affect a prolonged global nuclear winter. More people globally would likely die from starvation than from the nuclear blasts and ensuing radiation sickness.

Renewable energy, energy efficiency and conservation are the 21st Century energy policy.

Look almost anywhere you like on the web and you will find that it is always less costly to reduce consumption by a megawatt than it is to produce an additional megawatt.  Nuclear plants are phenomenally expensive, even after they foist much of the costs on taxpayers, the environment, and future generations.  Coal is just outright stupid.  Far better to buy solar hot water systems for everyone, insulate their homes, levy a substantial energy tax on homes larger than 1000 square feet per occupant, exercise some self-discipline & stop increasing our population way beyond sustainable levels, live closer to work, etc. etc.    

Ok, for all those who try to dodge the question with "right eye or left" sophistry, try this one:  If we embark on an aggressive, effective conservation and efficiency initiative as you propose, which type plants should be shut down first, or do you propose just letting the utilities decide that for us?

All you posters who've relpaced their parents mystical religion with "religious anti-anything", go back and re-read Asteroid-Miner's "Umbra is WRONG and paranoid, as usual", esp. the references which are legitimate.  Coal burning electrical plants continuously spew out more radioactives per year than comparable-power nuclear plants contain.  Then read that statement AGAIN, until you understand it!

I've invested my entire life savings and years of mathematical modelling in developing a new solar-powered Stirling thermal engine-generator which is still in prototype and may not work, but looks good so far.  BUT i STILL KNOW that almost all "conservation and efficiency gains" made in the past few decades have been simply shipping the heavy manufacturing industries to third-world countries which cannot afford our strict environmental regulations.  And yes, nuclear (and solar thermal) power CAN replace personal transport fuel, but switching all cars to PHEV's which will actually improve generator efficiency as well, by enabling a flatter load curve.

I hate reading junk about "Conservation Is The Only Solution" posted by people who couldn't mathematically calculate their way out of a wet paper bag, drink energy drinks (or WATER for crap sake!) from plastic or aluminum containers, while they post anti-nuke diatribes from their IPods or IMacs using wireless links because they'rs fashionable.  Shut the heck up for a while, maybe get some technical education, couldn't hurt and would sure make your speeches a lot more sensible, less childish.

Good choice, Umbra, die by bullet or die by knife.  A better, more modern choice, would be "Die quickly by action, or slowly by inaction?"  The status quo is untenable and a choice has to be made now, with the risk of dying quickly duly considered, and provided for in future plans, or else we should prepare for global drought (the Sahara and other deserts are measurably expanding in exponential rates), global flooding (melting sea-ice, glacial ice and snow cover [not snow amounts] is measurable along coastal areas, especially noticeable in places like Bangladesh and the Netherlands), fresh-water depletion, deforestation, and other long-term ills.

Yes indeed, nuclear power can be dangerous but it is the only energy source that can produce  sustainable, steady, emissionless electricity in the prodigious amounts 6 billion of us require to live on the planet.  Many small reactors feeding into a grid, co-generating heat and electricity for home and industry and pumping power into batteries to replace the internal combustion engine make the most sense to get us out of our present decline toward disaster.  Big is not always beautiful, and survival, not cost, should be the deciding factor in choosing our path.