Saturday, May 30, 2009

The world needs greatly increased access to power, not a reduction

I liked this comment by DaveMart from the EfT discussion section, so I decided to ask his permission to post it. Dave has graciously complied with my request.

The world needs greatly increased access to power, not a reduction
By DaveMart

'Looking at the alternatives conservation will be very important - but although savings can be made on North American levels of consumption, the vast majority of the world needs greatly increased access to power, not a reduction.

The obstacles to providing this by solar are non-trivial, and at minimum involve vast power grids being built and depend on breakthroughs in generation and importantly storage.
Certainly for Europe the power would have to be generated in North Africa, which is not necessarily reliable, and even there sunshine is much lower just when it is needed in the winter so you either have to vastly overbuild or convert to hydrogen or similar which entails massive losses.

Wind power also needs a huge grid, and a debatable degree of back-up.

The issue with all of these power sources is that they are low energy, and widely dispersed. Very large amounts of materials, including rare earths, would be needed to build them, and they are often most available where they are least needed.

I don't mean to totally dismiss these power sources, as they and things like geothermal can help a lot, for instance in hot climes solar on the roof producing power right where it is needed, especially for the poor, or for the rich in air conditioning in Arizona.

It is just a tough call to see them running the whole of an industrial society, and even tougher to see them helping the world's poor to a reasonable standard of living.

Fusion sounds like an ideal counterbalancing power source, as it is very dense and you can make it where it is needed.

The problem is that we are still a long way from being able to do it, and it is much more than a simple engineering issue to get there,

If you look at most of the proposed ways of doing so, they are truly vast structures, and hardly hold out the hope of cheap power, even if we learn to do it.

The authors here point out the disadvantages of nuclear power as it is presently generated, pointing to the cost, waste issues and proliferation concerns.

Most of the cost of nuclear plants arises from regulatory issues, their custom build, and the fact that these huge installations have almost all their cost up-front, and it may take many years to build.

Liquid fluoride thorium reactors (LFTR) can be built in all sizes from very large, and 100MW units can fit on the back of a lorry, so that they can be factory built and road delivered.

You can link several for generation of larger amounts of power - they can be modular.

Proliferation: the US had a demo molten salt reactor in the 60's. One of the main reasons it was killed was because it was not good enough at proliferation! It did not produce enough waste for the weapons program. Whilst we are talking about waste, not only would LFTRs produce far less and far less dangerous waste, but would be able to burn up present wastes, disposing of them without the need for Yucca mountain, so that is a multi billion gain to start with.

A 1 GWe reactor would need around 1 tonne of fuel per year, compared to 250 tonnes for a conventional reactor, and the tiny amount of waste produced decays far quicker.

They burn fuel at nearly 100% efficiency, compared to the 0.7% of conventional reactors.
That means a near infinite resource for practical purposes, and energy security.

The biggest difference between this technology and fusion is that it is a right now technology.
Of course there are engineering issues, but they are in no way on the same level as those needed for fusion, or even for the systems integration of a largely renewable economy.
The main one is dealing with corrosive salts at high temperature, in some design variants as high as 800C.

This was identified in the 60's, and even using the technology of the era was considered very doable.

There are a number of materials, including alloys and fibres, which should cope.
If that is more difficult than expected, there are also design variants of the basic concept which would operate at lower temperatures, or even variants which use solid thorium instead of liquid and so avoid the issue altogether.

So why aren't we doing it?

When it was being demoed it did not appeal for the production of weapons, as it is poor for this.

It did not appeal to much of the current nuclear industry, as they had a vested interest in LWR designs and made a lot of their money by the production of fuel rods, which is a cost that you avoid altogether.

It did not appeal to the miners, as the amounts needed are altogether trivial, and the coal industry would not like a technology which is likely to undercut them in cost before you consider the cost of carbon dioxide emissions or the huge wastes emitted by the coal industry, and which could even be fitted to coal stations, using all their generating equipment and throwing out the coal burn!

Supporters included Teller, and many of the founding fathers of the nuclear industry.
Here is the site for technical discussion of the technology:

'It's cheap, it solves the energy and global warming problems and throws in a solution of the nuclear waste issue, and the technology is right now.'


David Walters said...

I thought a conventional reactor uses about 25 tons of fuel?


DaveMart said...

I took the figures from the 'Aim High' presentation, one of the latter slides:
It gives the figures as 35 tonnes of enriched uranium for a 1GW reactor, and 215 tonnes of unenriched.
Perhaps you were thinking of the enriched figure?

Alex P. said...

It seems right. It takes about 35 tonn/year of enriched uranium (~ 3%) per GWe installed, with today LWR burn-up (~ 33 MWd per kg of LEU), that means 200-230 tonns of natural uranium. For newer LWR versions, 5% of enrichment, 55 MWd/kg,it takes about 25 tonn/year of LEU per GWe, the natural uranium need is quite the same

David Walters said...

Ah...ok...the problem is that I "translate" fuel in to waste out so it seemed high. But I understand now...and I completely forgot about the need for enrichment for most plants out there.

So in uranium production figures, always given in yellow-cake weight...this mine can produce 220 tons of fuel per year, we are talking un-enriched tonnage then?


Alex P said...

Yes, obviously. More precisely, as you certainly just know,uranium production figures are given in *heavy metal* weight of the yellow coke (U/U3O8 ratio is about 85%).
Of course, besides Candus, all reactors use low enriched uranium, so the real uranium "used" inside the reactor depends on many factors, for example tecnology choiced, BUP, or uranium enrichment tails (the lower it is, the higher the Swu, separative work units, you have to spend, but the better use of natural uranium you do); for example, to produce 1 kg of LEU at given 5 % (with 0,2 enrichment in tails, 0,71% "enrichment" of pure uranium) you have to consume (5-0,2)/(0,71-0,2) = 9,4 kg of natural uranium, even if only one kg goes into the reactor

Of course as nuclear operator, you well know all these facts so much better than me!

Finrod said...

I think from memory that Dave's power plant experience is actually with natgas, rather than nukes.


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