How much CO2 for current US fission plants?

HarryWertM

There is an interesting book out - I believe the title is "COOL IT" - which points that much "green energy " talk is nonsense. For example, the production of concrete necessitates the release of CO2. When you figure in the amount of CO2 generated for the manufacture of the concrete used in building a typical windmill, you realize the windmill must run for umpteen years before any "carbon free" energy is produced.

How about current US fission plants? How many tons concrete used on average? How long before energy produced is really "carbon free"?
-harry wertmuller

berkeman

Doesn't the book give you numbers that you can use to figure this out? It's not a very useful book if it doesn't present some numbers, IMO. I doubt the number is close to umpteen -- more likely a quick ROI, carbon-wise. There are plenty more things to go into the calculation anyway. You'd need to look at the construction and materials that go into a typical nuclear plant versus a typical other-power plant, I would think.

Interesting question, though, I wonder if there's much difference in the construction between a nuclear plant and a hydraulic plant...

russ_watters

I've seen this argument a bunch of times and it sets off my crackdar (crackpot radar), but I'm curious, so I'll run some numbers myself....

Here's a link that says making concrete produces .75 tons of CO2 per ton of concrete and curing it is .5 tons per ton for a total of 1.25 tons per ton. http://www.buildinggreen.com/feature.../appendixa.cfm

Anthracite coal is 32.5 MJ/kg (wiki) and produces a 4:1 ratio of CO2 (basic chemistry). Assuming a 60% combined cycle power plant efficiency, that's 0.8 tons of CO2 per MWH of electricity produced.

So every mWh of non coal power offsets 0.64 tons of concrete.

So how much concrete does a power plant have in it? According to this link, 190 cubic meters per megawatt: http://www.futurepundit.com/archives/004449.html and according to this one, its density is 2400 kg/m^3. http://hypertextbook.com/facts/1999/KatrinaJones.shtml

So that's 502 tons of concrete per megawatt. So 502 / .64 = 784 hours, or just over 1 month (please check my math!).

Yeah, looks like a crackpot myth to me.

russ_watters

Btw, the hoover dam has a capacity of 2078 mw and contains 3.3 million cubic meters of concrete. That's 1905 tons per mW or just over 4 months.

The concrete required for a windmill will be highly dependent on the particulars of the location (ie, out at sea = more, on bedrock in Pennsylvania = less), but I can't imagine it would be more than the concrete in a nuclear plant, much less a hydro dam.

HarryWertM

Thanks for the links . FUTUREPUNDITis excellent.

Given climate problems; economic problems; the current low cost of capital; the Obama administration's approval and publicity for a new nuclear plant is pure genius. At $5 billion apiece we cold have bought 36 plants with the $180 billion used to bail out AIG.

gmax137

Try googling 'externe' (with the extra 'e' on the end). This quantifies life cycle costs, including (I believe) the CO2 emissions.

mheslep

Probably not much concrete, but wind uses about 20X more steel for per MW than an equivalent nuclear plant, if these estimates we did some time ago are reasonable.

bonzoboy

A typical "fossil" coal plant can produce about 1 tonne of CO2 per MWh.
A typical "combined cycle" gas plant can produce about 1/3rd of a fossil coal plant

I say, can produce, because it is based on cycle efficiency. At part load ( a situation that occurs in the evening), the CO2 mass emission per MWh increases as the efficiency of the plant drops.

A brand new,out-of-the box coal plant, operating at supercritical conditions, will generate about 0.9 tonne/MWh. But add cycling up and down, and that figure will only increase.

minerva

There are many different studies out there that look at whole-of-life-cycle analysis of greenhouse gases for nuclear power, as well as other energy systems.

I'm sure if you have a look around on the NEI web site or something similar you will find many references on the subject.

Basically... it's essentially negligible, almost zero, just as it is for, say, wind or hydro power.
There is no energy generation technology of any kind that can practically have truly zero whole-of-life-cycle greenhouse gas emissions.

Also... I should mention that there is a lot of disinformation and nonsense out there on this subject from anti-nuclear activists, claiming that nuclear power actually has large whole-of-life-cycle greenhouse gas emissions comparable to fossil fuels. This is without any realistic evidence of any kind, is contradictory to mountains of evidence, and is complete baloney.

mgb_phys

Add in that CO2 isn't a big deal greenhouse wise compared to methane. Then work out how much methane is generated from flooding a few hundred sq km of woodland to build hydro.

mheslep

That one time methane shot is tiny compared to CO2 volumes released from the coal plant built in place of that hydro, not to mention the other pollutants.

mgb_phys

True, I meant that hydro wasn't as green as it looked if you just compared concrete to a nuclear plant.

mheslep

Oh, good point.

Mech_Engineer

Water vapor is a much stronger greenhouse gas than CO2, and the reservoir behind a dam has to add a significant amount of it to the atmosphere through evaporation...

mheslep

As I understand the theory, additional water vapor is not relevant to changes in scattering long wave radiation, i.e. the greenhouse effect, because water vapor already blocks nearly all radiative cooling - near the surface. Yes water vapor is a better long wave block than the other gases - but only near the surface (troposphere) where the water vapor is located. Thus heat escapes the troposphere mainly by convection. The increase, or possible change in the green house effect comes at the higher altitudes where there is almost no water vapor, but there is the standard atmospheric percentage of CO2 and/or methane. At the higher altitudes radiative cooling is in play, and more or less CO2 can change it.

gmax137

You're not serious, are you? The largest hydro lakes in the US are Lake Mead (640 km^2) and Lake Powell (658), and even the three gorges in China is only 1045 km^2. Compared to the rest of the planet's water surface (335,258,000 km^2), all of these dams are a few parts per million. I just don't see how that can be a "significant" contributor to the evaporation rate or the atmospheric content of water vapor.

Mech_Engineer

I was simply pointing out that there are much larger environmental effects than the methane output from a new reservoir.

Of course if I'm wrong, feel free to post a link to a study on the subject.