Tuesday, 21 December 2010

Nuclear manana

Dylan Jones Evans drew attention last week to an article in the Economist which suggested that a series of small "travelling wave" nuclear reactors would be a preferable alternative to a number of the larger 'traditional' nuclear stations.  At first sight it looks like an attractrive option, with Bill Gates claiming that it would solve all the usual problems with nuclear energy.

I'm not so sure though.  My biggest objection has long been over the issue of long-lived nuclear waste; it's a problem to which there is, as yet, no solution.  Gates claims that the travelling wave reactor solves even that problem, although the detail is light, to say the least.  I'd need a lot more explanation, rather than a simple bland statement, before I'd be convinced.

The other big problem is the one of timescales.  As this site indicates, the 'travelling wave' reactor is at this stage a design concept.  No-one has yet built one, and it looks like being another ten years before anyone does - and five years after that before there's any commercial application.  As is so often the case with the big technological fix to our energy problems, it's some time in the future, even by the optimistic projections of its backers.

That isn't an argument for not continuing research and debate; but it's a very strong argument for not depending on it.  We need answers sooner than that, and those answers, realistically, will come from existing renewable technologies and from those renewable technologies whch can be rapidly developed.  Assuming that new untried technologies will be our salvation is a recipe for continuing to ignore the need to act now.

8 comments:

Siônnyn said...

I don't know if you have seen Bill Gates at Ted" where he does quite a good job of explaining the process (at about 12 minutes in) . Economically - as it uses spent fuel as a source fuel - fuel which is effectively free as it costs a lot to store it at the moment- it appears that there is a huge economic incentive to actually get this working. Reactors are expected to be built with 60 years worth of fuel inbuilt, and once that is exhausted, it can be re-used!

So, in principle, this technology could address all your reservations about nuclear waste, and according to Gates, there is enough spent fuel in the USA to supply all its energy needs for the next 200 years.

As for the time delay - seeing how co2 reduction targets are generally set for 2050, this could definitely be an important ingredient in the mix!

I believe they can also be configured as micro reactors, so every town could have one or more, reducing the need for a national grid, and making the whole energy profile of a country much more resilient than at present.

And - as it doesn't involve enriched uranium or plutonium, there is no risk of the fuel being used - by terrorists or anyone else - for nuclear weapons.
Seems like a better bet than windmills to me!

John Dixon said...

Siônnyn,

Yes, I understand the principle of using non-enriched uranium which is in plentiful supply, of course. But the nuclear processes involved are rather more complex than that. And actually, the process does involve Plutonium - the Uranium is converted to Plutonium in the reactor before being involved in further nuclear reactions.

I do not understand how this eliminates the problem of nuclear waste, although it may change the nature of the problem. You still end up with highly radioactive reactors which have to be decommissioned at some point.

It's an interesting technology, and deserves to be studied further; but I have a feeling that the problems are being somewhat glossed over presently.

I'm not really sure why you think that not having a National Grid improves energy resilience. There are certainly arguments for some 'off-grid' generation, but the grid is an essential part of the current levels of resilience.

Wind turbines are a tried and tested technology today; putting wind energy on hold in the hope that there would be a new nuclear alternative twenty years from now would look like a huge mistake to me.

We cannot, of course, depend totally on wind, for a number of reasons; but it will inevitably have a significant part to play in any low-carbon energy future.

Siônnyn said...

The plutonium is created on the fly, as it were,during the reaction, and not transported or stored anywhere, and would be far too hot to actually procure. As I understand it, one of the ideas is to have these reactors deep underground, so that the reactor effectively absorbs the radiation.

The spent fuel can be reprocessed and used again a fuel, it seems.

The national grid is still a fairly monolithic architecture, in my understanding, and a small number of adverse events (gernerator outages for instance) can bring the whole thing down. We have seen this in Europe, and often in the US.

If instead of a few very powerful base reactors, we have thousands of smaller reactors, more evenly spread though out the country,(UK) the effectsd of outages would be very much reduced.

As I think I have said before on here - I am a believer in Nuclear power as a relatively clean source of energy ( the residual waste is less harmful, and more easily contained, I believe, than the CO2 that other generators pump out), but I don't think that Wales as a country needs it! Still, it is interesting to keep up with current thinking on these matters!

Siônnyn said...

PS I still have not seen a proper energy audit of the effectiveness of wind to reduce CO2. Do you have a link?

Photon said...

Nuclear waste disposal is something that the goevernment/industry cabal are trying to incorporate into the costings. But, there's little real idea how much disposal will actually cost if and when we get a UK-based repository. We can guess, according to what other countires do, but we can't factor for the costs of difficult geology or other unexpected hiccoughs.

Nuclear fission has, to some degree, be seen as a technology in its infancy. It's probably never going to grow up, as nuclear fusion will overtake it in the next decades. This leaves the very real possibility that, when a fusion reactor finally reaches commercial viability, it will leave a string of expensive, obsolete fission stations in its wake. What does that mean about the financial viability of fission reactors? I'm not sure, but it probably means there's less money to be made out of them than we currently believe is the case.

John Dixon said...

Siônnyn (1),

"The plutonium is created on the fly, as it were,during the reaction, and not transported or stored anywhere"

Agreed. My only point was that it was an oversimplification to state that "it doesn't involve enriched uranium or plutonium" as you did in your original comment.

The plutonium "would be far too hot to actually procure"

Not convinced about that. They way it is produced might well make it not worth trying to procure, but all the world's stockpiles of Plutonium were created in and procured from nuclear reactors. As it happens, though, I don't object to the user of Plutonium in reactors anyway - far better to burn it up for energy than store it for weapons - provided we can solve the waste problem.

"one of the ideas is to have these reactors deep underground, so that the reactor effectively absorbs the radiation"

Putting the reactor underground wouldn't make 'the reactor' absorb the radiation any more than having it above ground. It might make it possible to simply seal off the reactor after use though. But isn't that just another version of deep burying nuclear waste? If deep burial is considered a safe means of disposal than it cna be used for wastre from existing stations, can't it? I'm not currently convinced, though, that deep burial is a safe disposal route. If I were to be so convinced, I'd be reconsidering my position on nuclear energy anyway.

"The national grid is still a fairly monolithic architecture, in my understanding, and a small number of adverse events (gernerator outages for instance) can bring the whole thing down."

I think you may be understimating the load balancing and management capabilities of the grid. Smaller local networks would in some ways be even more liable to failure; the failures would be more total, but more contained to a local area.

The tendency is currently to 'extend' the grid by having interconnectors with other 'national' grids. The UK Grid is connected to France currently, and will shortly be connected to the Netherlands and Ireland as well. The possible European supergrid would provide further resilience.

I understand the argument for a certain amount of off-grid activity for some purposes; but I do not understand how anyone can argue that the grid reduces resilience.

"the residual waste is less harmful, and more easily contained, I believe, than the CO2 that other generators pump out"

Now if that were to be established as a fact, it would be one of the best arguments that I could think of for nuclear generation. It falls down, though, if there are other low carbon options available, such as wind, tide, solar...

John Dixon said...

Siônnyn (2),

"I still have not seen a proper energy audit of the effectiveness of wind to reduce CO2. Do you have a link?"

That sounds like an entirely reasonable and simple question. Sadly, it isn't quite as straightforward as that. There are really three aspects to it.

1. I think it's reasonably well established that a wind farm operating at normal capacity will pay back the carbon cost of its construction in a reasnable short period - I've seen figures of between 1 and 3 years.

2. I think it's also reasonably clear that energy produced by wind, if it displaces energy produced by burning fossil-fuel will reduce total carbon emissions.

3. The area of dispute is whether, and to what extent, the use of wind energy requires 'spinning' backup, so that instead of switching off the fossil-fuel stations, they continue to emit just as much CO2 even if their output is not being used. This is a difficult question, marred by assumptions and misunderstandings which are frequently not spelled out by those using them. And since ALL generation capacity requires a degree of backup for energy security, it isn't easy to sort out which is there specifically to cover wind energy.

This link has a theoretical discussion and calculation of the back-up requirement. And the National Grid itself has produced a report suggesting that wind energy does not require additional back-up capacity.

The use of, say, wind energy is another reason for having an 'extended' grid. Opponents of wind point out that wind is highly variable, and common sense observation supports that view. It's only true, though, when looked at at a micro level. If turbines are dispersed over a wide enough area, that variability is much less of an issue. The wind doesn't just stop, suddenly, over the whole of northern Europe.

I'm convinced that wind is a worthwhile technology, and does contribute to emissions reduction; but neither I, nor anyone else, is suggesting a 'wind-only' energy policy.

John Dixon said...

Photon,

"nuclear fusion will overtake it in the next decades"

When I was in school in the 1960s, fusion energy was just twenty years away. 50 years on, and it's still twenty years away. Whilst I'm quite happy that research should continue, I put this in the same category as the mini-reactors - we really can't depend on an as yet unproven technology to solve our problems. We can continue to research them, but also need to act now on those technologies which are proven.