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http://www.gizmag.com/water-nuclear-bat … sis/33844/
http://www.nature.com/srep/2014/140611/ … 05249.html
Unfortunately, there's nothing about power density. Well, aside from the report saying they were getting 75 microwatts/cm^2.. So 750mW/m^2, but without saying what the mass or thickness of it is, that's not very helpful. RTGs seem to manage at least 3.5W/kg, and this one is supposed to be better... if it's supposed to be viable as a replacement for car batteries, then it should be at least 50W/kg? That would mean 2 tonnes for a 100kWe system. Competable* with solar? I don't expect people to be happy with launching nuclear reactors, but radioisotope generators..?
*Buffy speak
Use what is abundant and build to last
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Actually, when you get right down to it, a radioisotope generator is a nuclear reactor. One that uses decay instead of fission, and presents roughly the same risk of radioactive materials dispersal in some kind of accident.
Also actually, we've been launching reactors and radioisotope generators into space for decades now. All probes to Jupiter and beyond are powered this way, as solar is just ineffective that far from the sun. And, a great many of the spy satellites circling the earth are powered this way, and have been, since the beginning in the 1960's.
The Cosmos 954 crash in Canada in the 1970's was a Russian spy satellite powered by a plutonium reactor. There's a whole lot of those cores in very high orbits around the earth today. That was the design disposal method for that series of "Cosmos" craft. Not many folks want to face this fact, but it is true.
Kinda makes the fears about a nuclear explosion drive ship seem silly, doesn't it?
One day, we humans will have to go to high orbit and retrieve that radioactive junk for proper disposal. But there's time. Centuries, in fact.
GW
GW Johnson
McGregor, Texas
"There is nothing as expensive as a dead crew, especially one dead from a bad management decision"
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However, a Strontium battery is less complex than a fission reactor, and it gives of beta radiation rather than gamma, so if the core is exposed, you don't need heavy shielding for cleanup - and you don't need to park it a hundred metres away, either. Perhaps these aspects would make it's overall power density comparable to a fission reactor..?
Plus, it will probably be much easier to launch one without massive protests.
Use what is abundant and build to last
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I still think we should look at SAFE-400 as a substitute for SP-100 for Mars Direct. It does the same thing, same power, but lower mass. SP-100 was the newest design at the time. SAFE-400 development ended 2007.
If you want new, high-tech designs, then look at Potassium-40. Some research showed that a modulated magnetic field can induce much more rapid radioactive decay. It releases beta radiation. Without the magnetic field, it decays so slowly that this isotope isn't regulated. This allows fuel to be controlled: release radiation when needed, so fuel is consumed only when needed. Safe and efficient.
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That sounds interesting, could you provide a link? If true, it would provide a potential source of power for colonies as well...
I can't really find much on the power density of betavoltaics. Tritium is another potential fuel, and may allow for a higher power density. But finding figures for the power density is difficult. Each decay produces 0.018590 MeV. After 12.32 years (3.89e8 seconds), half of the mass will decay. If we start off with 3 tonnes of Tritium, then we'll have 6.02e28 particles to start with, so the total energy produced over those 12.32 years will be (3.01e28 * 0.018590 MeV * 1.6e-13) = 8.95e19J. Which doesn't make much sense, because the average power output should be... 2.3e11W, or 230GW. Now, 3 tonnes is a ridiculously large amount at the moment, but if we wanted to we could mass produce it from Lithium. But still, the figure sounds ridiculously high. Even if we only tapped a tenth of the power, we'd have over 20GW available...
I'm sure my calculations are wrong somewhere.
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Okay, to figure out the answer another way...
1.5kg of Tritium contains 3.01e26 particles, according to Avogadro's constant. That means the average decay rate in a 3kg pile, over 12.3 years, will be (3.01e26/3.89e8) = 7.74e17 decays/second. Each decay produces 1.86e4 eV of energy, which is (1.60e-19 * 1.86e4) = 2.98e-15J. So our average power output will be (7.74e17 * 2.98e-15) = 2.3kW. Meaning our 3 tonne pile will produce 2.3MW, rather than 2.3TW, an error of a 6 orders of magnitude (I misremembered Avogadro's constant before).
I knew there was something wrong with the above figures, since they seemed to imply nuclear warheads would melt...
Since the researchers I linked to managed 55% efficiency, it would not surprise me if we could get 1MW out of our 3 tonnes. Maybe even get a power density of 100W/kg...
Start mass producing it from Lithium, maybe? Have we been so focused on fusion that we've neglected a potent power source that's been here all along?
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Well, it looks like it won't provide net energy, due to the requirement for neutrons that Josh pointed out to me, but it looks promising as a... well, as a battery, providing power to ships and initial colonies.
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Here is a link to the paper. They require you to purchase the paper, but I have a .PDF copy.
http://iopscience.iop.org/0295-5075/81/ … /fulltext/
Observation of the acceleration by an electromagnetic field of nuclear beta decay
H. R. Reiss 2008 EPL 81 42001. doi:10.1209/0295-5075/81/42001
Received 9 September 2007, accepted for publication 7 December 2007. Published 11 January 2008.
Europhysics Letters Association
Abstract
Measurements are reported of the acceleration of the first-forbidden beta decay of 137Cs by exposure to intense, low-frequency electromagnetic fields. Two separate experiments were done: one in a coaxial cavity, and the other in a coaxial transmission line. The first showed an increase in the beta decay rate of (6.8±3.2)×10−4 relative to the natural rate, and the other resulted in an increase of (6.5±2.0)×10− 4. In addition, a Fourier analysis of the rate of 662 keV gamma emission following from the beta decay in the standing-wave experiment showed a clear indication of the frequency with which the external field was switched on and off. A simultaneously detected gamma emission from a placebo nucleus showed no such peak.
Exponents don't show in this quote. And this paper deals with caesium, while power production has looked at 40K (Potassium 40). But the same techniques apply. And this is a real science paper, peer reviewed and published. So it demonstrates intense, low-frequency electromagnetic fields can affect rate of beta decay.
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One way of altering the rate of decay of a radio isotope is to take advantage of relativistic effects. Put an isotope in a particle accelerator. From the observers viewpoint, the rate of decay will decline. Unfortunately, the energy required to create and maintain the relativistic plasma vastly exceeds any energy that you could store in this way.
Check out Metastable isomers:
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There are a couple that come to mind in the LENR and with the E-Cat. plus Hot E-CAT both fitting in the radio-isoptic reactions....with the incoming materials tranmutating in slightly different ones at the end of the process....
It appears like fussion but it is just a redioactive decay exchange....
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An example is the natural decay chain of 238U,(Protons 92, Neutrons 146) which is as follows:
http://en.wikipedia.org/wiki/File:Decay … eries).svg
decays, through alpha-emission, with a half-life of 4.5 billion years to thorium-234,(Protons 90, Neutrons 144)
which decays, through beta-emission, with a half-life of 24 days to protactinium-234,(Protons 91, Neutrons 143)
which decays, through beta-emission, with a half-life of 1.2 minutes to uranium-234,(Protons 92, Neutrons 142)
which decays, through alpha-emission, with a half-life of 240 thousand years to thorium-230,(Protons 90, Neutrons 140)
which decays, through alpha-emission, with a half-life of 77 thousand years to radium-226,(Protons 88, Neutrons 138)
which decays, through alpha-emission, with a half-life of 1.6 thousand years to radon-222,(Protons 86, Neutrons 136)
Ect...
which decays, through alpha-emission, with a half-life of 3.8 days to polonium-218
which decays, through alpha-emission, with a half-life of 3.1 minutes to lead-214
which decays, through beta-emission, with a half-life of 27 minutes to bismuth-214
which decays, through beta-emission, with a half-life of 20 minutes to polonium-214
which decays, through alpha-emission, with a half-life of 160 microseconds to lead-210
which decays, through beta-emission, with a half-life of 22 years to bismuth-210
which decays, through beta-emission, with a half-life of 5 days to polonium-210
which decays, through alpha-emission, with a half-life of 140 days to lead-206, which is a stable nuclide.
Last edited by SpaceNut (2014-11-04 18:50:09)
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