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January 29, 2012

What if we get super cheap D-D (Deuterium-Deuterium fusion power?

A guest article by
Joseph Friedlander

What if thermonuclear power was as easy to build as a plasma torch, or rocket engine-- some simple electromechanical assembly (with precise electronic controls) that could be built in a home workshop and unleash a horrific fusion plasma with the power output of a rocket engine not in vacuum but from induced direct fusion of D-D (Deuterium-Deuterium fusion power--using just a tiny feed line of gas from a bottle of D.?)

Knowledgable readers will know this is quite a what if-- [this article will only be considering if the end result happens and not how it could be achieved.)

First of all no prospective fusion reactor exceeds breakeven (all take huge multiples of the energy they produce, in grid electricity, to even keep the machine running)




Second of all these huge uneconomical machines are often the size of a shopping mall, (sometimes a small one)

Third of all they need exquisite vacuum and pumpdown, not ambient atmosphere

Fourth of all they would rapidly consume themselves (heat and neutron radiation) in ordinary environment

Fifth of all they use the easy and scarce D-T (Deuterium Tritium) reaction, with Tritium bred from scarce Lithium-6, (look up Peak Lithium, whether true or not the prospective shortage boosts the price of natural lithium)

Sixth of all even with a functioning fusion reactor it would be very expensive per BTU because of all the anciliary equipment which has to be paid for an amortized, even if R and D is paid for already--(barring a revolution in fusion design, I am speaking of classical designs)

Brian has covered many potentially revolutionary designs --(this link is to all articles with the fusion label on Nextbigfuture)

Lets compare the potential cheapness of thermonuclear power to coal

(cheapest chemical fuel) in $ per gigajoules, not megajoules, because of

the quantities involved (1000 megajoules = 1 gigajoule) going first

for reference to--
www.euronuclear.org/info/encyclopedia/coalequivalent.htm -.
13 Jan 2011 – 1 kg coal equivalent corresponds to a value specified

as 7000 kilocalories (7000 kcal ~ 29.3 MJ ~ 8.141 kWh)


29.3 gJ/ton coal at $80 ton gives $2.73 a gigajoule coal


1 million tons of coal equivalent 29.3 million gJ/(almost a gigawatt year) would be $80 million.
http://www4c.wolframalpha.com/input/?i=tons+of+coal+equivalent+in+3+gigawatt+years

3.23 million tons coal is 3 thermal gigawatt years (22.6 million tons tnt equivalent)
at $80 a ton $258.4 million dollars for 3 gigawatt years thermal coal

1 GWyr is (3.15 x 10^16 J)

7.537 megatons tnt factor of 3 for ordinary steam conversion 22.611 megatons TNT equivalent thermal

http://www.convertunits.com/from/gigawatt+hour/to/megaton

1 GWyr = 8.76 x 10^9 kWh.

http://www.unitconversion.org/energy/gigajoules-to-megatons-conversion.html

4184000 gigajoules per megaton equivalent
2.4 megatons are equivalent to the efficient fusion of 29 kilograms of D-D.Deuterium is say $500 a kilogram, so that is $14500 for 29 kg.

this is 10041600 gigajoules (29 kg of D.)
273.2265774379848 kg of D is enough D for 3 thermal gigawatt years
$136613.2887189924 is cost at $500 a kilogram of enough D for 3 thermal gigawatt years

vs. $258.4 million dollars for 3 gigawatt years thermal coal

So Deuterium is 1891 times cheaper than coal if we could burn it with impunity. This is not merely less than a penny a thermal kilowatt hour, it is a couple thousand times less. If--IF we could make some assembly for a few dozen dollars a kilowatt (think the price of a gasoline engine) that burned D-D the world would be completely different.


The key thing to remember is that D-D fusion is very neutron rich so transmutation (for good--medical isotopes) and bad (bomb plutonium) would be everywhere easy. Not saying that Pu239 could not be used for reactors, it could-- but why would you need it if fusion was that easy?

It would pay to melt local soil to lava and mold a neolithic cave for a house for a few hundred dollars, an entire fused soil superhighway (1000 km long and 20 meters wide) for a few hundred thousand dollars fuel cost. We would be living in a new stone age of cheap fused soil structures (assuming good annealing)

It would pay to have fusion tunnelers melting underground tunnel complexes in place of present structures.

It would pay to seastead because you would have unlimited cruising range and power draw for a given kilowattage and could probably extract D in a home unit from the oceans as you cruised, as well as power to light and heat a greenhouse in the coldest foulest weather. So food, water, utilities (obviously distilled water) would be easy and given the availabliity of bomb plutonium (insert depleted uranium near the D-D reactor and wait) probably a good idea to be at sea.

It would pay to colonize the moon and melt tunnel complexes, and heat and power everything during the lunar night. Anywhere in the solar system, in fact. Since under a ton of D could power a colony for a year, it would be shipped to places where it was hard to mine.

Comets could be steered (with sunshield to keep cold) to high Earth orbit using their own D and water as fuel and reaction mass.

Rocket power would be cheap with no mass ratio problems--assuming a light enough rig. The Saturn V first stage put out 190 gigawatts for 4.5 minutes--

en.wikipedia.org/wiki/Orders_of_magnitude_(power)
but here the exhaust velocity could be far higher. It would probably pay to energize ordinary water at first for maximum thrust, then get really hot as the rocket lightened to save reaction mass.

The biggest problem would be the neutrons.
(need to protect the atmosphere from Carbon 14 formation)--so rocket travel for a few minutes going o space would be OK, unshielded endless airplane travel not so much. Shielded trains and ships and subs OK, large landcrawlers and hovercraft OK, but not small fusion vehicles (given the EROEI, synthetic oil would be 10 x cheaper than today, but 100x the power cost of large fusion vehicles)


It would pay to heat the outside in major cities wastefully, so you did not need a parka during winter, to melt the snow extravagantly, to de-ice runways all winter and make it impossible for snow to stick to the ground.

(And to drive heat pumps for whole city cooling in summer though the waste heat would be a problem then)

Readers are invited to suggest other extravagant uses for individual power in the comments below.


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