Monday, June 12, 2006

Why Nuclear Power Cannot Be A Major Energy Source


/ not that cheap /
A very interesting analysis on the limitations of nuclear power:

"It takes a lot of fossil energy to mine uranium, and then to extract and prepare the right isotope for use in a nuclear reactor. It takes even more fossil energy to build the reactor, and, when its life is over, to decommission it and look after its radioactive waste.

As a result, with current technology, there is only a limited amount of uranium ore in the world that is rich enough to allow more energy to be produced by the whole nuclear process than the process itself consumes. This amount of ore might be enough to supply the world's total current electricity demand for about six years.
Moreover, because of the amount of fossil fuel and fluorine used in the enrichment process, significant quantities of greenhouse gases are released. As a result, nuclear energy is by no means a 'climate-friendly' technology."


The article also explains why proposed alternatives to Uranium, such as Thorium, are a long way down the road (despite recent developments and publicity)
See also this discussion over at Eurotrib about "peak Uranium".

15 comments:

lazopolis said...

Nuclear fusion could, on the other hand, give us an almost final solution to the energy problem. But, of course, fusion research projects are relatively (to the potential importance of the application) underfunded.

lazopolis said...

And opposed - occasionaly - by Greenpeace.

talos said...

Yes it could, but that's filed under "future technologies", which are rather difficult to plan for. I mean when do you expect to have a commercially viable fusion generator, that produces more energy than it consumes, consistantly and controlably? It might be as they say in the 2030s but then again it might not. And 12 billion Euros isn't underfunded. Really. What's better funded these days?

Anyway, any environmentalist who's against nuclear fusion knows very little about fusion. I do understand the problem, though, that fusion will be and is branded as an excuse to not do anything about greenhouse gas emmissions today - but that doesn't have much to do with funding fusion research...

Renegade Eye said...

We keep hearing nuclear power is an alternative to fossil fuel.

Good post.

lazopolis said...

-What's better funded these days?

Apparently the International Space Station (but i shouldn't be complaining about that).

ITER is finally funded and going, but I meant funding for the whole research sector for nuclear fusion, at a university level. The field is disproportionally (relatively to the possible outcome) small: according to me it should have been the highest priority research goal in the whole positive science sector, globally. And it should have been there (with media promotion etc.) 20 years ago.

In the last seminar on the topic i followed it was mentioned that the earliest date for a plant connected with the grid and meeting the production constraints, is 2050 (according to some estimates, that's not much before the fosil fuel resources run out)!

I, too, understand the fears of Greenpeace, but they should, in turn, understand that, by mixing political with scientific arguments this way, they loose their credibility within the scientific community.

talos said...

lazopolis: yeah, you're right, I think the reasons for not investing in and publicising the fusion effort have more to do with entrenched interests than anything else.

Greenpeace is clueless, just read this:

Fusion energy - if it would ever operate - would create a serious waste problem, would emit large amounts of radioactive material and could be used to produce materials for nuclear weapons. A whole new set of nuclear risks would thus be created.

Rather spectacularly misinformed...

Anonymous said...

CANDU reactors operating with deuterium don't require enriched uranium since the control material is denser (hence more collisions). I should think that the same applies to graphite pebble bead reactors. As for the fast fusion (unregulated) reactors ,I recently read some estimates that thet will be operational by the 30's. These could really be a sustainable solution as their waste products would include plutonium, which is of course a nuclear fuel.

Yochanan

cosmix said...

Nuclear Fission is ok, compared to oil or coal, and I cannot accept the cost of mining uranium as an argument against it. The only problem I can see is lacking an eco-friendly way to dispose of waste and I am sure we could come up with something if we cared a bit more about that. The problem is that we don't care enough.

I agree with lazopolis that the funds going towards Nuclear Fusion are very limited, if one puts the whole thing into perspective. While it is true that a lot of public funds (mostly from the EU) are spent on ITER, it is by no means 'a lot' considering that the project has been in preparation/negotation/planning for more than 20 years. It is also meagre when compared to the total amount of money spent on other academic and industrial research portfolios in the US and Europe (one of the most important, a prime 'academic' and, somewhat theoretical I might add, example might be CERN's LHC that currently is expected to cost US$8Bn according to Wikipedia -- Note: I am not discounting the scientific or social value of LHC here).

Regarding the date one would expect a 'working' fusion generator, well, among other things, it kind of depends on how much you try to reach that point doesn't it? It's not about theory anymore, it's way beyond that. If ITER were working in 1995, we'd already have 10 years of a head-start and despite the possible shortcomings of that preliminary design there is a significant chance we might be better off. Mind you, it took 4.5 years between agreeing on a design and agreeing on a site to build the damn thing!

In the end, while this may seem like a bad attempt at overdramatising it, achieving the SciTech breakthrough is only one part of the challenge. There will be political/economic obstacles in releasing fusion technology to the world, I am afraid.

Anonymous said...

Well, they are right about fusion producing nuclear waste. Fusion produces neutrons; neutrons go until they hit something. When they do hit something, that something becomes radioactive.

The original article seems to have two points (1) nuclear power produces C02 during the mining, processing, etc.; (2) we will run out of uranium.

Putting (2) aside, (1) seems rather weak. /All/ forms of energy generation use energy to build the generator. Early windmills used more electricity to build their (mostly aluminum) hulls than they could ever produce. (N.B., this has not been the case for years, but one still sees the factoid tossed around sometimes.)

By the article's own terms, nuclear power generates between 1/6 and 1/3 as much CO2 per unit of energy generated as fossil fuels. My reaction to that is not exactly outrage.

Every form of energy production has consequences. I'm a huge fan of windpower, but I acknowledge the studies that show it could cause wide-scale climate change. (Yes, really. Put up enough windmills to run a country, and you're sucking a lot of energy out of the air. Recent models suggest that this could quite noticeably affect wind patterns, weather, and climate.)

Unless we move away from our current energy-intensive mode of civilization, we're left with choosing what consequences we want to live with.


Doug M.

talos said...

Well Doug, yes neutrons will produce radioactive nuclei, but a (depending on their energy) not too much and not long-lived. If they radioactive material produced has short lifetimes - on the order of days f.e. Thus nuclear waste disposal ceases to be a problem.

Re: Wind Power. We're talking about a rather minimal effect comparatively. See this for example:

Will climate change due to wind turbines be noticeable in the face of other climate changes caused by humans?

Our results suggest that on a global scale the answer to this question is no. Unless the use of wind power grows so large that it supplies roughly as much power as the entire current global electric power system, the large-scale climatic effects of wind power will likely be negligible. It is plausible, however, that significant local climate change could occur in areas where wind farms are concentrated even if wind supplies a small fraction of global electricity demand.


Finally about the Greenhouse Gas Emissions from the Nuclear cycle. The issue isn't mainly *now*. It's the future when only lower quality Uranium ore will be available. I quote:

The advantage of nuclear power in producing lower carbon emissions holds true only as long as supplies of rich uranium last. When the leaner ores are used - that is, ores consisting of less than 0.01 percent (for soft rocks such as sandstone) and 0.02 percent (for hard rocks such as granite), so much energy is required by the milling process that the total quantity of fossil fuels needed for nuclear fission is greater than would be needed if those fuels were used directly to generate electricity. In other words, when it is forced to use ore of around this quality or worse, nuclear power begins to slip into a negative energy balance: more energy goes in than comes out, and more carbon dioxide is produced by nuclear power than by the fossil-fuel alternatives.

piglet said...

Regarding fusion: it is an illusion to think that waste disposal will not be a problem. The main problem is the material of the reactor itself which will have to be replaced frequently. Fusion advocates are claiming that with the right choice of materials, this waste will have to be cared for only for about 100 years. This is much less than for fission but its not insignificant. And those are the most optimistic estimates. We simply have no idea how accurate they are.

The real question, however, is whether there will ever be a technically viable fusion reactor and truth be told, there is absolutely no rational reason to assume that the answer to that is yes. Technical progress in the past decades has been abysmal, despite lots of funding, and even now, even with ITER, scientists are still very far from even adressing the real technical difficulties. They don't even know whether they will ever be able to sustain a controlled fusion reaction and keep in check the resulting extreme conditions. Don't let yourself be blinded by illusionism.

Anonymous said...

The solution to limited uranium supplies already exists in breeder reactors. Needless to say, these are dangerous high-tech monsters that operate in ways that are far, far more unsafe than traditional reactor types. Also needless to say, there IS NO WAY to dispose of super-toxic waste that will last for millions of years. Conscious human culture is only a few thousand years.

The question is one of giving in to the industrial mafia, or working towards real sustainable, not dangerous energy sources.

Anonymous said...

Well Doug, yes neutrons will produce radioactive nuclei, but a (depending on their energy) not too much and not long-lived.

The most plausible reaction for commercial use is the D-T, which produces an alpha particle at 3.5 MeV and a single neutron at 14.1 MeV. In other words, roughly half the energy output is in the form of neutrons!

Some of this can be recaptured in secondary reactions, but still: you end up with a buttload of neutrons and a lot of radioactivity.

There are aneutronic fusion reactions. Unfortunately, they either (1) involve energies so high as to be completely implausible, or (2) involve lots of Helium-3. Until we start mining the surface of the Moon (seriously) He3 is going to be very rare and expensive. It can be created in breeder reactors from Deuterium, but -- guess what -- you got it -- the breeding reactions produce lots of high-energy neutrons.

Until we know exactly how a fusion reactor will look -- what reactions, what energies, and what secondary cycles -- it's impossible to say how much radioactivity it will produce. However, all plausible models in play at this time produce significant amounts. And by significant I mean "same order of magnitude as existing fission plants".


Doug M.

talos said...

piglet: waste disposal will be a problem, but much less of a problem than with fission reactors.

Concerning the feasibility of a working fusion reactor - well if you talk to people involved with the physics they are fairly optimistic. The point is you can't know until you try doing it - and it is indeed possible that it will lead nowhere, so its a matter of risk assessment. ITER will give us a better idea about the feasibility of fusion.

DM: You missed the point, I quote from the relevant Wikipedia article:

The large flux of high-energy neutrons in a reactor will make the structural materials radioactive. The radioactive inventory at shut-down may be comparable to that of a fission reactor, but there are important differences. The half-life of the radioisotopes produced by fusion tend to be less than those from fission, so that the inventory decreases more rapidly. Furthermore, there are fewer unique species, and they tend to be non-volatile and biologically less active. As opposed to nuclear fission, where there is hardly any possibility to influence the spectrum of fission products, the problems can be further reduced by careful choice of the materials used. "Low activation" materials like vanadium, for example, would become much less radioactive than stainless steel. This involves the design of new alloys with unusual chemical compositions, which is a complex process as the chemical composition also affects the materials' mechanical properties. However rather than the thousands of years for radioactive waste produced from fission, such low activation materials would have half-lives of tens of years and rapidly approach the radioactivity of coal ash.

Note: it's all in the future, as possibilities. We won't know more unless we try (invest, risk whatever)...

Anonymous said...

Color me skeptical. Remember when fission power, "too cheap to meter", was going to solve the world's problems?

Again: we don't even know for sure what reaction we'll be using. D-T is the lead candidate, but D-D is in there too, along with some more exotic stuff. We don't know what energies will be involved. Ergo, we don't know what sorts of neutrons will be produced (other than "a lot") nor at what energy levels.

So when I see an article saying "oh, no biggie, we'll just use vanadium", I'm instantly skeptical. That assumes knowledge that we /do not have/.

That's before we even get to the physical structure of the reactor. Any engineer will tell you that the interactions between mechanical, chemical and radioactive properties get hair-raisingly complex. It took decades to get a reasonably firm grasp on this for fission reactors. We don't know what the nuclear island (the reactor core) will be made of. As in, we really have no idea. And we don't know what the blanket will be made of: tungsten? graphite? Something else?

I'll quote from that same article:

Developing materials for fusion reactors has long been recognized as a problem nearly as difficult and important as that of plasma confinement, but it has received only a fraction of the attention. The neutron flux in a fusion reactor is expected to be about 100 times that in existing pressurized water reactors (PWR). Each atom in the blanket of a fusion reactor is expected to be hit by a neutron and displaced about a hundred times before the material is replaced. Furthermore the high-energy neutrons will produce hydrogen and helium in various nuclear reactions that tends to form bubbles at grain boundaries and result in swelling, blistering or embrittlement. One also wishes to choose materials whose primary components and impurities do not result in long-lived radioactive wastes. Finally, the mechanical forces and temperatures are large, and there may be frequent cycling of both.

The problem is exacerbated because realistic material tests must expose samples to neutron fluxes of a similar level for a similar length of time as those expected in a fusion power plant. Such a neutron source is nearly as complicated and expensive as a fusion reactor itself would be. Proper materials testing will not be possible in ITER, and a proposed materials testing facility, IFMIF, is still at the design stage in 2005.


In other words, we don't know what it will be made of because we don't even have the ability to test materials yet. All discussions of island and blanket materials to date are _purely and entirely theoretical_.

So, again, saying "we can use low activation materials" involves so many assumptions as to be pretty close to an empty statement.

Doug M.