Wednesday, August 15, 2007

Laser Fusion - Techno-fix to World Energy Crisis?

The latest putative technological ray of salvation from the imminent energy crisis that confronts the world is Laser-Fusion. At an expected cost of half a billion Euros, a mighty laser is to be constructed which can create enormous temperatures at which nuclei will fuse. Lasers are currently used to heat plasmas, normally containing tritium and deuterium nuclei, above the ignition temperature of 40 million degrees required to overcome the electrostatic forces whereby the positive charges on these nuclei repel them from one another, getting them close enough that they can fuse-together, releasing energy in the process. The ignition temperatures that must be achieved for other hydrogen nuclei to fuse are far greater than this, hence the focus on the deuterium-tritium couple. However, in all cases I am aware of, it takes more energy to run the laser than is extracted from the plasma itself. This is partly a result of limitations in laser technology, but if an extremely powerful laser can be built, and which furthermore can fire sequentially at a sufficiently rapid rate, scientists believe that a sustainable working fusion reactor might be a possibility. The world's most powerful lasers need several minutes to recover for a second burst, but the HiPER laser will need to fire several times a second.

It is not thought that a commercial reactor will happen any time yet, and I am reminded of the ITER project at Cadarache in France: an experimental thermal fusion reactor project costing ten billion Euros, which it is thought might produce a working reactor in about 60 years, allowing for the various development stages planned. The laser-fusion HiPER project has been earmarked as "priority" by the European Union, and is intended to overtake the US-funded imperative known as the National Ignition Facility (Nif) in Livermore, California. When Nif is built in 2010, physicists are confident that the laser will be sufficiently powerful to start a fusion reaction, and experiments undertaken using underground nuclear explosives in the Nevada desert have provided evidence in regard to just how much energy the laser will need to provide to do this.

Mike Dunne, who is director of the Central Laser Facility in Oxfordshire and where the world's currently most powerful laser, Vulcan, is housed said: "The world is going to take notice when this happens. Politicians are going to look around and say, 'So what are you going to do about it? What is the next step?' This is how to take it from a scientific demonstration to a commercial reality. The trick now is, can we get it to work without throwing a nuclear bomb at the thing?"

Fair enough, but the engineering challenges are huge. Indeed in neither ITER or HiPER have the materials been devised that can withstand either massively energetic neutrons or a mighty laser beam, and without them any commercial development seems unlikely. It is often said that nuclear fusion is an attempt to replicate the processes going on in stars, e.g. the Sun, and yet Earth-bound plasmas are of very low density compared to the huge gravitational pressures in stars which dramatically increase the probability of fusion occurring, e.g. the solar proton-proton cycle which probably could not be reproduced sustainably on Earth.

The world will begin to run short of fossil fuels: first oil, then gas and finally coal, beginning within just a decade for oil. Unless more nuclear fuel is found, nuclear power has only a limited lifetime too, without the development and implementation of breeder technology based on uranium or thorium. The energy clock is ticking away, and I wonder, even if these behemoths can be made to work, not just at all but commercially, how quickly might this be done in reality. 60 years for ITER will almost certainly be too late to come to our aid in the impending energy crisis, and if HiPER has a similar projection in timescale then both may be regarded in the future as white elephants, similar to those architectural follies that pebble-dash the British landscape, which finally served no practical purpose.


Related Reading.
"Laser fusion - the safe, clean way to produce nuclear energy," by James Randerson, The Guardian. http://www.guardian.co.uk/nuclear/article/0,,2091037,00.html

9 comments:

John Parris said...

Thanks for your comments Chris. The HiPER project has indeed been identified by the EC as meriting priority consideration for development funding, and this will take place during the coming Autumn, with a decision hopefully around Christmas 2007. There is increasing evidence that this process will be workable as the technologies advance and, mindful of your point that long development times are pointless because the world faces a serious energy crisis in a much shorter time scale, the key thing is to be ready when NIF in the USA demonstrates first ignition (expected at the Lawrence Livermore Lab approx 2010/2011)to respond to the inevitable questions from politicians... not with a long time scale to research the next step, but with a plan fully researched and ready to go, to build a laser driven "fast ignition" demonstration reactor, which will make the process feasible at the commercial/industrial level for large scale power production without the bi-products of CO2 or serious radioactivity.
The recently started European ITER project, now under construction at Cadarache in France is the other approach to the search for fusion energy on the industrial scale. Nobody can predict which process will first deliver a result, nor indeed precisely when, but it is absolutely clear that as we face a huge energy crisis, linked to a looming environmental crisis, the right way forward is to fully support both approaches to the problem in parallel. Both methods hold out great hopes for success when there is no viable long term alternative in large scale energy production to meet the huge energy appetite of the human race.
Given the expected development times, it seems certain that we must rely on 4th generation nuclear fission to provide the bulk of our power if we are to stop burning fossil fuels before the environmental crisis runs completely out of control. Equally, everything possible must be done to develop renewables, simply to help bridge the time gap before the heavyweight clean energy technologies can be brought to bear. Finally, with developing nations such as India and China racing ahead to construct heavily polluting power stations at a rate far exceeding anythig happening in the West, we must educate the world about the lunacy of turning a blind eye to the energy/environment link... otherwise, with rather more force, nature is likely to "educate" us all in its own good time. John Parris.

energybalance said...

Thank you, John!

I am encouraged by your comments that the technology might be brought on-line on a much shorter timescale than the 60 years say that I have heard about for ITER.

We will need alternative energy technologies in very short order to address the imminent threats from the shortfall in fossil fuels and from climate change, and 4th generation nuclear power does seem to be key here.

The biggest problem seems to me of how we will provide transportation fuel on the level that we currently use petroleum for that purpose. My conclusions are that in the short term we may not be able to, resulting in a dramatic fall in the number of vehicles on the road and in the air especially. I think we would be pushed to match that amount from renewable sources e.g. biofuels, again because of the scale involved. i.e. There are issues of food crops competing with fuel crops.

I like the idea of a huge energy resource from fusion, but as you say, time will tell whether these become commercially functioning power-stations or hopefully not white elephants.

There is no doubt humankind is facing a gargantuan cocktail of problems, and I wonder which (climate change or fuel supplies) will get us first if nothing is done!

Best regards,
Chris.

John Parris said...

Chris,

You are right that hydrogen (or other portable fuel for transport) is a big issue for the future.
We have all got very comfortable with the idea of driving around carrying a handy tank of petrol to give us a few hundred miles' range, and the option to top up almost everywhere we might want to go. Unless we can solve the portable fuel problem soon, I think we will gradually be forced to change our travel habits.
In the UK most people regard public transport as very much the second choice... unreliable, unpleasant and expensive ! They value their freedom to move around cheaply and at will.
It's interesting that the fusion process, burning deuterium and tritium fuel is expected to produce both helium AND hydrogen as well as lots of energy, although I'm not sure if the quantities of hydrogen come anywhere near what would make the transport equation balance in the future. I suspect there has to be another way.
With regard to the timescale, I think the scientists who really know would regard 60 years as probably pessimistic, but don't let anyone think that laser fusion is a "magic bullet" either. There remain a number of technical challenges to be solved before this can be made industrially effective, so perhaps 20 to 30 years might be more realistic !
That's why both these projects need and deserve serious funding and long term political support... support which extends far beyond the natural life span of any one government.
What we really need everyone to agree on is that ignloring the double-edged crisis we now face is no longer an option.
It's time for the politicians to go a step further than waking up and talking about it. Politicians are voted in to make sure that the work that really matters gets done, and few things on this planet have a higher priority than fixing this one before it fixes us !!! JP

Dezakin said...

It still needs to be less expensive than wind, solar, or fission power. Stories like these don't inspire me, and usually are traced back to some lab fishing for grant renewal. Given the absolutely huge resources of fissionable materials (1 trillion tons of uranium for light water reactors, 120 trillion tons for breeder reactors) fission is good enough to illustrate that the term 'energy crisis' in the long term is alarmist bull.

More interesting to me is laser enrichment; If that ever gets refined it will make fission and waste remediation much cheaper. Of course, it also makes weapons production much cheaper too.

energybalance said...

Very interesting comments Dazakin (as usual from you)!

I agree, and as noted, there is that dark period when fossil fuels run scarce to be dealt with, even if the technology can be got up and running in 30 years say, since there will be no oil and debatable amounts of gas by then.

Now you talk about nuclear, and I think undoubtedly that will play a large role in future energy provision. I am interested in where the amounts of nuclear fuel you refer to come from. Are you referring to the amount in the earth's Crust, or in the oceans?

Breeders can use effectively all the uranium - the 99.3 or so % of U-238, and yet there seems to have been little investment in this technology compared to fission, which seems strange doesn't it?

As you say, laser-enrichment is another very interesting technology, which could be used for good or evil!

When you put the case like this re. nuclear, there really does seem to be light at the end of the tunnel. But I still think the greatest immediate issue to hit us will be how to keep our transportation running without oil.

Regards,

Chris.

Dezakin said...

I doubt ocean retrieval of uranium will be economic in any timeframe we can reasonably discuss because theres so much more of it in the crust.

http://nuclearinfo.net/Nuclearpower/UraniuamDistribution

In shales and phosphates there are some 1 trillion tons of uranium avaliable above ore concentrations of 20 ppm. Thats well enough to recover for positive energy gain of 16-32 to run all of the worlds energy needs for 25000 years on light water reactors alone. In breeder reactor regimes the energy gain is hundreds of times higher and you can use ore grades as poor as they go, as well as thorium giving you some 120 trillion tons of fissionable material. If you burned all that fissionable material as fast as you can without significantly slagging the earth from waste heat it would still last millions of years.

I fully expect we will develop something to replace nuclear on economic grounds sometime in the next several centuries, but I'm hard pressed to see it as a matter of survival.

Replacing oil for liquid fuel production however, yes it certainly will be painful. Trillions of dollars have been invested in such infrastructure after all.

energybalance said...

I wrote a posting "Not Enough Uranium for Nuclear Expansion?" March 23rd, referring to a conclusion by a group at MIT, but concluding myself there is plenty of it to be had.

My fear is that because it takes other resources, oil, gas and water, to extract it and to make the fuel rods etc., it may be we will run out of these before we do uranium.

I suggested that if we were to feed-back some of the electricity from using it in a nuclear power plant into the uranium production process, that might help, but it does seem a very intricately interconnected web of resources.

By the way, what are your thoughts on the hydrogen vs electron economy? You know, that paper by Ulf Bossel that has caused so much angst? He thinks we should either store the electrons made using renewable methods in some kind of advanced battery technology or use it to make liquid fuels like methanol from CO2. I worry about the latter process because you are also throwing some of those electrons away to make water as well as the fuel, or the same (maybe worse) by converting it with H2 to fuel, if there are the energy losses incurred that he suggests.

I have also read a report by a German firm of analysts that suggest the losses he thinks are associated with H2 are an overestimate, but still the problem of switching-over to a hydrogen economy is massive. It is an awkward material to work with too. I was a chemist at one time and have handled H2, and retain a respect for the material!

As we spoke too in earlier days, I was shocked to read that platinum is such a rare metal and that only limited amounts of it might be brought on stream... it seems almost like betting the farm on the favourite and which may then fall in the final furlong, even if all other matters can be overcome, without the fuel cells ultimately...

Regards,

Chris.

Dezakin said...

As for the other resources required for uranium mining, this doesn't overly concern me. By far the most energy intensive process in uranium mining is the milling, which can easily be run by nuclear electric motors. Most of the other resources required are functions of energy, which nuclear power gives in ample supply.

I don't see hydrogen being a substantial energy carrier any time in the near future however. Hydrocarbons are just too damned convenient, and yes you can just manufacture them from limestone and water when the coal runs dry; Using limestone for a carbon source leaves quicklime as a waste product which absorbs CO2 from the atmosphere anyways, so it seems to work.

Hydrogens best utility seems to be as a rocket fuel and perhaps someday in hypersonic aviation. For general transport, I never see it taking off; either batteries will be used or hydrocarbons. Trillions of dollars of infrastructure have a lot of inertia, in addition to diesel fuel being just about the densest way to store hydrogen/energy that doesn't have unpleasant effects like decaying into a nerve gas.

Jerry said...

Great blog and comments! I just found this page!

I know I'm a little late getting into this, but here goes..

The solution to portable fuel for transport seems, to me, to almost take care of itself with introduction of more nuclear plants producing electricity.

Plug-in hybrid vehicles can be refined over the next few years to a point of commercial viability. You would simply plug in your hybrid at night to an existing electrical outlet, utilizing the excess nighttime energy on the grid. Your vehicle would also have a tank for gasoline for longer trips than your batteries can hold.

The beauty of this scheme is that no new infrastructure is needed!

Another use of nighttime excess energy can be used to refine biofuels. The current program of biofuel production here in the US is a ridiculous political boondoggle, using more oil to refine corn than energy achieved. Using excess nuclear energy would help sequester not only that nuke energy, but also solar energy stored in the plants used for the biofuels. This would reduce our reliance on petroleum even more.

It's really not a great technological challenge.. it is merely a problem of management and having the will to do it!