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January 20, 2010

Summarizing how Better Nuclear Fission and New Nuclear Fusion Can Lower Energy Costs

Eric Drexler wrote an article about why he believes that nuclear fusion will not provide power. Eric is an expert in molecular nanotechnology and has deep knowledge in chemistry, physics and space technology (among other things).

He is pointing out studies which indicate the cost problems even if the tokomaks of the ITER project are successful.

It appears that Eric has not taken a deep look at nuclear fission and nuclear fusion technologies and the economics of the current potential systems.

UPDATE: Eric clarified his position. Emphasized that yes it is Tokomaks that are no good, but also why he doubts the alternative fusion methods.

As several of you have noted, what I say about “fusion power” is really about tokamaks, the dominant approach to fusion today. I’ve been following the evolution of fusion power concepts, including the many alternative approaches, for decades now. All machines that look more-or-less like current tokamaks (stellarators, for example) would have similar capital-cost problems.

Laser-driven inertial confinement schemes are different, but have led to sketches of power plants that again seem highly implausible. The research machines are, however, of scientific interest for studying the properties of various kinds of matter at extreme pressures and temperatures of interest in astrophysics. Plasma fusion machines, unfortunately, are good for little but studying fusion plasmas.

Bussard suggested several fusion-machine concepts, including a scheme for a very different kind of tokamak (with a small, disposable core), and, of course, the entirely different Polywell approach. There’s not much in print about Polywell, at a technical level, but from what I‘ve read, (1) I’d give long odds against the proposition that the scheme actually makes physical, technological sense, and (2) I’m glad to see that it’s being investigated more closely.

The famous Bussard ramjet, by the way, is a non-starter because hydrogen is virtually inert as a fusion fuel, no matter what the temperature and pressure may be. The first reaction on the road to helium produces deuterium (1H + 1H –> 2H + positron + neutrino). This is very slow because it requires the conversion of a proton to a neutron during the nuclear collision (a weak-interaction process). That’s why the Sun has lasted for several billion years, and puts out less power per unit mass than a good compost pile.

Using a fusion machine as part of a fission fuel cycle would be a very challenging way to solve a problem that doesn’t need to be solved. The cost of uranium is such a small component of the cost of fission power that existing, practical schemes for using it more efficiently, such as breeder reactors, haven’t been widely deployed.

My response to Eric's comment -

Closing the fuel cycle matters if you are looking to scale nuclear fission usage up by one hundred times. Driving down costs by five to ten to fifty times is needed to drive that demand and to transform civilization. Yes, if we are doing things pretty much as we are now then no we do not need to change for several decades or longer.

If I want to get nuclear fission costs to one cent per kwh then the 0.7 cents per kwh for fuel becomes an issue. Better and cheaper enrichment and better burnup help those matters. Fuel fabrication and enrichment are the major parts of making the fuel and there are several ways to make huge differences there either with the fuel or with reactor designs.

Existing reactors can have fuel retrofits with annular or dual cooled fuel for up to 50% more power from the same reactors. (cylinders -more surface area - instead of rods)

Deep burn would also help with the public relations issue of "what about all of the nuclear waste?". Nuclear waste mostly being unburned fuel. If I want to scale up, I have to solve the public relations issue. Of course this is less of a problem in China and outside the OECD where 75% of the new reactors are likely to go. In China it is straight up engineering questions. So a transition to moderately deeper burn pebble bed from 2020-2035 (starts 2013 but not a major part until 2020) and then a shift to breeders 2030-2050+.

Russia has its 600 MWe breeder that it has been running for that last 30 years in Beloyarsk and is completing a 880 MWe reactor for 2012. Burnup is only about 100-150 Gwd/t. China is buying two fo the 880 MWe breeders and China is making one of their own. India should have five breeders from 2010-2020. The first one is firing up shortly. Russia has 2-3 other kinds of breeder reactors that they are building or will be building. A promising system is the SVBR-100 reactor which would be factory mass produced and would be fast breeder. India, China and Russia all plan to export the reactors that they develop. China is initially focused massive internal build but will get to exporting. Hyperion Power Generation is working on small uranium nitride and then uranium hydride factory mass produced nuclear reactors.

So substantial significant deployment on second generation breeders is coming.

In 2008, I had made an analysis of what it would take to get mainstream nuclear fission to the cost level of about 1.3-1.7 cents per kwh (including construction costs)

$1000/kw capital costs, 2 year construction, 80 year life, reduced fuel costs 2 cents/kwh for new construction, plus less waste handling with deep burn. I believe this will achievable in China and possibly with Russian reactors (with capital costs of about $1400-1600 per kw now). The faster two year construction times are coming.

One of my many articles that detail nuclear fusion technology discusses the potential for breakthroughs in energy costs from the most promising nuclear fusion projects.



The World Nuclear Association has breakdowns on the economics of existing nuclear fission reactors. The price per Kwh is about 3.4-7 cents

Cost breakdown nuclear fission

A big factor is interest rates and the time for construction. Longer time to construct means longer time before revenue while carrying the costs of building. Then there is the factor of how long the plant lasts. 60+ year life means more time to spread out the construction costs. A 5 year build with 60 year life gets down to 3.4 cents.

At 45,000 MWd/t burn-up this gives 360,000 kWh electrical per kg, hence fuel cost: 0.71 c/kWh.

Enriched fuel prices could be cut in half by using laser enrichment. GE is making such a plant with scheduled 2012 opening.

Burnup can go up 20 times (various kinds of breeder reactors – like the liquid fluoride reactor that others have told you previously to investigate. 900,000+ MWD/t is possible). If burnup goes up then more KWH per kg and lower cents per KWh.

China is looking to factory mass produce pebble bed reactors with 2 year or less construction times. Walkaway safe from meltdown because they will not exceed 600 MW thermal power per module using the pebble bed system.

Higher temps mean easier use of “waste heat” for industrial purposes (co-generation). Idaho national labs has achieved 19% burnup of pebbles. Up to 65% burnup is possible with more highly enriched pebbles. Better electricity conversion efficiency is possible with higher temps. China plans to build them by the dozen and share a control center and upgrade to the higher temps, higher burnup, more efficient brayton cycle turbines later. By their 300th reactor module they will be quite advanced.

An inferior fusion reactor can perform transmutation of U238 (waste as it is not fissile like U235 but just fissionable) into plutonium to help 10 regular fission reactors achieve 100% burnup. Transmutation does not require the 20-50 times energy return of a commercial fusion reactor. get to energy breakeven or close to it or just over and you have good enough transmutation. You can also get away with 50% availability (uptime).

So fusion is an alternative to close the nuclear fission fuel cycle.

Some of the leading candidates for nuclear fusion described below may succeed in a faster time than the time it would take to develop and commercialize the superior breeder or acceletor drive systems to enable deep burn fission. There is still technical risk (maybe the new fusion systems do not work as well as planned) so deep burn fission should be developed in parallel.

Leading candidates for fusion
Inertial electrostatic fusion – robert bussard before his death got rid of the magnetic grids to enable 100,000 times lower losses. They now have 8 million in US Navy funding. Dr Nebel now leads the project and indicates two years to confirm fusion only commercializability. IEC reactor would be very small. This system could lower energy costs by five times.

Tri-alpha energy and Helion energy- Working on field reversed configuration colliding beam fusion. Tri-alpha got funded with over $40 million and has been secretive but may make some announcements this year. Helion built a one third demo and is raising more funds. Note: Helion energy’s reactor would be far smaller than ITER. As tall as a man but about 50 meters long.

General Fusion in Canada with about $30 million. A magnetized target fusion variant.

Dense Plasma Focus fusion- $1.2 million project 2009-2010. Lawrenceville plasma physics. using plasmoid nuclear pinch with about a billion gauss to get high temperatures overcome x-ray losses. This system directly converts to electricity (does not use thermal conversion). It would potentially be the cheapest system if it is successful. Fifty times lower energy cost is possible.

Muon fusion continues in Japan. 40% energy return now. They are trying to tweak it to achieve better return.

The big laser fusion projects and ITER tokomak are multi-decade projects. I think ITER is inferior to deep burn fission by itself.

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