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Nuclear Battery That Runs 10 Years
Jenny writes "A battery with a lifespan measured in decades is in development at the University of Rochester, as scientists demonstrate a new fabrication method that in its roughest form is already 10 times more efficient than current nuclear batteries -- and has the potential to be nearly 200 times more efficient. Similar to the way solar panels work by catching photons from the sun and turning them into current, the science of betavoltaics uses silicon to capture electrons emitted from a radioactive gas, such as tritium, to form a current. As the electrons strike a special pair of layers called a 'p-n junction,' a current results. I can imagine lots of applications for this new battery including my own laptop."
How does tritium affect people's health?
As with all ionizing radiation, exposure to tritium increases the risk of developing cancer. However, tritium is one of the least dangerous radionuclides because it emits very weak radiation and leaves the body relatively quickly. Since tritium is almost always found as water, it goes directly into soft tissues and organs. The associated dose to these tissues are generally uniform and dependent on the tissues' water content.
How does tritium change in the environment?
Tritium readily forms water when exposed to oxygen. As it undergoes radioactive decay, tritium emits a very weak beta particle and transforms to stable, nonradioactive helium. Tritium has a half-life of 12.3 years.
How do people come in contact with tritium?
People are exposed to small amounts of tritium every day, since it is widely dispersed in the environment and in the food chain. People who live near or work in federal weapons facilities or nuclear fuel cycle facilities may have increased exposure. People working in research laboratories may also come in contact with tritium.
How does tritium get into the body?
Tritium primarily enters the body when people swallow tritiated water. People may also inhale tritium as a gas in the air, and absorb it through their skin.
What does tritium do once it gets into the body?
Tritium is almost always found as water, or "tritiated" water. Once tritium enters the body, it disperses quickly and is uniformly distributed throughout the body. Tritium is excreted through the urine within a month or so after ingestion. Organically bound tritium (tritium that is incorporated in organic compounds) can remain in the body for a longer period.
Obliteracy: Words with explosions
p-n junction can be so much more than a diode. A diode is in many cases composed of a single p-n junction, but diode != junction. I totally agree with the poster for calling it that way.
You don't call two p-n junctions in the transistor a diode. You don't call the p-n junction in the solar cell a diode...
The term "diode" can also be applied to a vacuum diode, Schotky diode, etc. neither of which is composed of a p-n junction.
Disclaimer: I am a nuclear engineering graduate student.
This seems like a rather nifty extention of the technology. However, note that the fuel source, tritium, is rather hard and expensive to come by. (The total world supply of the stuff is < 40 kg.) So I see this as a great boon for, say, space probes or other fancy applications where getting your hands on some tritium gas aren't the biggest of concerns on the budget. It'd be interesting to see how they compare to other nuclear batteries that rely on heat from alpha-decay of heavy isotopes like plutonium to generate electrical currents.
As far as all the jokes about a nuclear laptop battery using this technology causing sterility, note that tritium decays via beta emission (i.e. an electron), with a range in solid materials of a few mm, so those energetic electrons will stay in the battery. Your primary concern would be if you somehow cracked the thing open and inhaled the tritium gas -- then those few mm of exposure in your lungs etc. aren't the best things to have around energetic particles. (And, as far as having to ingest nuclear sources, tritium is probably one of the better ones, since not only does it have a relatively short half-life of ~12 years, but it gets flushed out of the body rather rapidly as it diffuses into the bloodstream/water in tissues, leading to a much shorter effective biological half-life of 11 days.)
There is another way to make a "nuclear battery", which was discussed in the september 2004 issue of IEEE's Spectrum magazine (could not get a link...): by ionizing a bit of matter, it gets attracted to other matter (think static electricity). So you ionize a flat, piezoelectric part that's attached at one end over an unmovable base plate. The attraction makes the loose end of the part strain down to the base, and the piezoelectric nature of the part makes it generate electricity on the way.
You're not old until regret takes the place of your dreams.
In terms of increasing amounts of information (least to greatest):
http://en.wikipedia.org/wiki/David_Hahnl b .html
http://www.dangerouslaboratories.org/radscout.htm
http://laplace.physics.ubc.ca/Students/borthwic/r
Depends. Both U-235 and Pu-239 decay via alpha emission, which is easily blocked by almost anything. The risk for detection is beta, gamma, and neutron emission, which the daughter products can release. U-235 is especially bad because not only is its half life 30,000 times slower than Pu-239's, but the principal gamma radiation released in the decay sequence is low energy (a millimeter of lead should be enough to shield most of it).
Purity is important, of course. Your typical reactor-grade plutonium has sizable amounts of Pu-240, which is a lot more detectable. Likewise, if the uranium wasn't created with the intent of making it smuggled, it probably has contamination of U-232, which has a very high energy daughter product decay that wouldn't be realistic to shield. There have actually been proposals to deliberately contaminate all uranium produced (to the extent that international cooperation allows) with U-232 to make smuggling unrealistic.
Stale pastry is hollow succor to one who is bereft of ostrich.
Well, troll is a little strong I think, the concern is valid but should be alleviated with some background knowledge :)
These batteries won't be detected by radiation detectors, anyway. No pulling you off public transport for that.
Not only will the weak beta radiation not get out of the battery, even if the battery does leak, you can pour millicuries of tritium all over detectors, be it badges or geigers or whatever. The weak beta radiation won't even develop film.
Now, medicinal doses of I131 or wahtever- those show up loud and clear. I had a friend who had to have his thyroid zapped- he pegged out lab geiger from 5 feet away.
Weak beta emitters like tritium that are really almost no concern- I'd like it if they were more dangerous as then you can monitor them more easily (they show up on things like a geiger).
The onyl way to "detect" weak betas like tritium is to mix it with some other substance that glows just a tiny bit when hit with low energy beta particles, and then load it into a special very sensitive machine to look for that emitted light.
All that said, I'd like to know if they are loading their battery with millicurie quantities or what- if it leaked, that could be an ingestion hazard. I've not RTFA to see though :)
HTH.
HTH.