# Electric cars

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How many miles could an electric car go on a single charge with plutonium batteries?. The Voyagers are still running on them.

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Van Chocstraw
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Van Chocstraw wrote in news:ds2dnbDvWsm14SjUnZ2dnUVZ snipped-for-privacy@giganews.com:

None.

You don't 'charge' plutonium 'batteries'.

Plutonium (under the right conditions) is a source of heat (along with a lot of dangerous radiation).

By using thermocouples and a heat source (along with a heat sink [for Voyager, the 'sink' is "space"]) you can generate electricity.

So, to power a car with plutonium, you would need enough plutonium to produce heat at the rate needed to power the car. Exercise for the reader: calculate the amount of plutonium needed to produce the power needed to produce the horsepower of YOUR car. Lookup the amount of power needed by Voyager. Compare.

The 'battery' would produce that amount of heat ALL the time[unless there was a mechanism to control the fission rate of the plutonium, say by separating the parts of the nuclear reactor and shielding them from each other]. A difficult and complicated mechanical task.

It would produce a hazardous amount of neutrons and other radiation, requiring a LOT of heavy shielding. Making the car heavier, and thus requiring MORE energy to power the car.

It would need a way to get rid of the heat produced. (Voyager radiates the heat into space). Imagine a car with two car sized, black, wing shaped "radiators" that would add to the aerodynamic drag and be an accident hazard. Or perhaps you would rather carry a tank of water and let the production of steam cool the plutonium. What happens if your tank runs dry? Meltdown!

The reactor would be a major hazard if broken open in an wreck. Plutonium is a potent source of radiation and very 'poisonous'.

It would be a weapon that terrorists could use. They could open it, take out the plutonium and scatter it around. They could collect the plutonium from several batteries and build a 'suitcase' bomb.

There are many very good reasons to NOT use 'plutonium batteries' in cars, here, on earth.

I can't think of ANY good reasons to use 'plutonium batteries' to power cars. There are good reasons to use them for some space missions.

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bz    	73 de N5BZ k

please pardon my infinite ignorance, the set-of-things-I-do-not-know is an ```
• posted

bz wrote in news:Xns9BCA4F30EE258WQAHBGMXSZHVspammote@130.39.198.139:

Uh,wrong. Pu doesn't have a "lot of dangerous radiation".

Plutonium-238 has a half-life of 88 years and emits alpha particles. It is a heat source in radioisotope thermoelectric generators, which are used to power some spacecraft.

alpha particles are NOT "dangerous radiation".

Alpha particle emission, which is the release of high-energy helium nuclei, is the most common form of radiation given off by plutonium.[3] Heat given off by the release of and deceleration of these alpha particles make a mass of plutonium the size of a softball warm to the touch while a somewhat larger mass can boil a liter of water in a few minutes, although this varies with isotopic composition.

Uh,RTGs are not "reactors". Or have you changed the subject and are now talking about actual fission reactors?

not in RTGs.

Again,NOT a "potent source of radiation". Poisonous,yes.

doubtful;wrong isotope,in RTGs.

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Jim Yanik
jyanik```
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In article , snipped-for-privacy@abuse.gov says...>

About as poisonous as lead. If you're in the EU don't make electronics out of it.

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krw wrote in news: snipped-for-privacy@news.individual.net:

Pu oxide is pyrophoric,too.And it oxidizes easily. If you ingest it,THEN the alpha particles become a serious problem. So,don't eat it. ;-)

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Jim Yanik
jyanik```
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How far can you go on a power source that delivers only about 300 watts? (Hint: 1 horsepower = 746 watts). The Voyager "battery" uses thermocouples to produce the electricity. While very efficient, with no moving parts it is very reliable.

The Voyager Pu-238 batteries use 11 kg of the toxic Pu-238 stuff. Assuming 33% conversion efficiency, to build a 100 horsepower vehicle, you would need 6,500 kg of Pu-238 using the same technology. Not every useful. You would probably be better off using the heat to boil water and power your vehicle with a steam engine.

Incidentally, 11 kg is very close to the critical mass for Pu-238, so anything bigger would probably cause control and safety issues.

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# Jeff Liebermann 150 Felker St #D Santa Cruz CA 95060
# 831-336-2558            jeffl@comix.santa-cruz.ca.us```
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Jeff Liebermann wrote in news: snipped-for-privacy@4ax.com:

of course,that is only if you have the Pu in just ONE mass,instead of dividing it into subcritical cells and summing the outputs.

BTW,a "battery" is a number of individual CELLS, wired together for a higher output.

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Jim Yanik
jyanik```
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Fear mongers is why we don't have plutonium batteries.

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Van Chocstraw
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We don't have to make them like Voyager. Use plutonium like lithium as an electron producer what doesn't deplete. Cells can be ganged up like regular batteries except that they would last 100 times as long. I don't know about recharging only reprocessing.

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Van Chocstraw
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I believe it was you that suggested "The Voyagers are still running on them." More on the Pu-238 battery design:

Note: I are not an expert on fizzix, thermodynamics, or nuclear power.

If not like Voyager, what are you suggesting? With an energy density of 0.57 watts/gram, the 11kg of Pu-238 should produce 6,270 watts. Of course, your (Carnot) heat engine isn't going to be 100% efficient. For example, the Voyager thermopile appears to be about 5% efficient. If you take my suggestion and build a steam engine, you might get about 20% efficiency (including gear losses), which should be barely adequate to run a very small vehicle. Of course, it may take several weeks to build up enough steam pressure to go anywhere.

I think you have successfully blundering upon the basic problem with energy conversion and transportation. Transportation devices want concentrated energy, available on demand, and lots of it. Most natural sources of energy are not very concentrated. That's for good reason as if they were concentrated, they would have disappeared or diffused long ago. It's like solar power. There's lots of it around, but it's not very concentrated (1Kw/sq-meter). The best you can do is accumulate some diffuse source of energy (solar, wind, nuclear battery), into some manner of energy storage (pressure, phase changes, battery, air pressure, etc), and use it in its concentrated form when needed.

Incidentally, there's a small problem with operating temperature. The Voyager Pu-238 battery only operates in space, where the ambient temperature is near absolute zilch (-273C) with a differential operating temperature of about 300C at the thermocouples. If you try to operate it at 25C, the thermocouples will run mighty hot, and the entire assembly end up at about 1200C. As heat loss is energy loss, I hope your proposed vehicle battery design is very well thermally insulated.

I don't want to discourage you from revolutionizing automobile design, but I think it might be useful if you did some calculations or back of the envelope estimates before you proceed.

Pu-238 decay produces lots of alpha particles but no electrons.

If one cell of Pu-238 has a half life of 87.7 years, 100 cells have a half life of 87.7 years, 1,000,000 cells have a half life of 87.7 years, etc.

Half the battery warranty expires after 87.7 years. Drop in a new lump of Pu-238 and drive off in a smog of alpha particles.

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Jeff Liebermann     jeffl@cruzio.com
150 Felker St #D    http://www.LearnByDestroying.com```
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True for critical mass, but not so true for thermal meltdown. It really depends on insulation. If the outside of the battery were properly insulated, Pu-238 will continue to pump energy into an almost adiabatic (perfectly insulated) system until it gets hot enough to melt. The heat has to go somewhere. As built, the Cassini and Voyager batteries run at about 1000K. The space probes radiate the surplus heat into outer space (the ultimate heat sink), but that's not practical on the planet. As a result of this radiation, the themocouples run at a differential temperature of only about 300K to preserve the themocouple junctions.

I like to call it a "pile" or in this case, a "thermopile".

I also like to call a collection a web pages a "web pile" for the same reason.

It appears that space missions will consume the entire supply of Pu-238 from Russia by 2017, as the US isn't making any. So much for the neighborhood Pu-238 filling station.

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Jeff Liebermann     jeffl@cruzio.com
150 Felker St #D    http://www.LearnByDestroying.com```
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Oh, I thought the plutonium atom had plenty of loose electrons.

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Van Chocstraw
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Jeff Liebermann wrote in news: snipped-for-privacy@4ax.com:

Pu melts at 912.5K.

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Jim Yanik
jyanik```
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That's for metallic Plutonium 238. Plutonium Dioxide melts at 2240C.

However, there's still a problem. What I did was read:

and accept the numbers without questioning them. Quoting:

"Cassini will use three RTGs, which convert thermal energy from plutonium decay into electrical energy. Each RTG contains 72 small pellets of plutonium-238 dioxide, each about the size of a marshmallow and weighing 150 grams. Each pellet is encased in many layers of protective materials, and the complete unit is called a general purpose heat source (GPHS) module. All together these 72 heat sources put out 4400 watts of thermal energy at an operating temperature of 1200°C to 1300°C. Using a set of thermocouples, the RTG converts this heat energy to about 285 watts of electricity."

Note the 1200C to 1300C operating temperature. However, furthur down, it says: "Each RHU weighs only 40 grams and generates one watt of thermal energy through radioactive decay, operating at about body temperature (35°C-40°C)."

Well, one of those operating temperatures is wrong, or I'm perhaps I'm missing something. The photo of the Pu-238 slug self-heating to incandescence suggests that its running fairly hot. I'll dig through the available literature and see if I can excavate something definitive.

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# Jeff Liebermann 150 Felker St #D Santa Cruz CA 95060
# 831-336-2558            jeffl@comix.santa-cruz.ca.us```
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A marshmallow-sized lump of Pu would weigh rather more than 40g (I believe), and it approaches the size where it runs quite hot, if not quite incandescent (which I think it hits at around golfball-size).

Clearly these numbers are wildly inconsistent.

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Maybe they're both right if I make an assumption. If the 1200C is the temperature of the Plutonium Dioxide marshmallow, but the 40C is the temperature of the thermocouples, it might make sense. The temperature gradient between the Pu-238 and outer space is substantial. By positioning the thermocouples in the desired place along this gradient, almost any operating temperature can be selected. I would be more worried about melting the thermocouples than the Pu-238.

Disclaimer: I'm guessing.

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Jeff Liebermann     jeffl@cruzio.com
150 Felker St #D    http://www.LearnByDestroying.com```
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IDIOT.

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You're talking complete drivel, probably intentionally.

Graham

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