EETimes: radioisotope battery

[Dr Mordrid]

http://www.eetimes.com/at/news/OEG20021104S0040

Since the isotope used, Nickel 63, has a half life of ~100 years the battery should last decades.

Uses: military, remote sensing, implantable medical devices etc. etc.

Dr. Mordrid

[agallag]

Now that's some cool stuff... How soon until I can get a PDA that runs for 20 years between charges?

[Marshmallowman]

Radioactive decay processes have been used in satelites for a long time, and probably in quite a few miltitary things as well (they use the heat from the decay process, i vaguely recall).

This one differs in that it uses a direct conversion to motion.

It sounds like its going to be great for a lot of remote sensors used in science/metrology/seismic stuff..

But I think you may find the quantity of material needed to run a PDA may give out a bit to much radiation for you to leave it in your hip pocket.

[Dr Mordrid]

The generators used in satellites use a different principle: the thermocouple. Heat from decay causes a current flow across two dissimilar metals. As you noted this one directly converts to mechanical motion.

The radiation from such a device is usually alpha or beta, meaning you can shield it with aluminum foil or thick paper.

Dr. Mordrid

[GNEP]

Yeah, but imagine the tabloid press headlines:

NOKIA TRIES TO SELL KIDS CHERNOBYL FOR THEIR POCKETS

[Sethos]

it's about time that we get a fule cell that lasts more than an hour and half. Problem is we'll be glowing green LOL.

~Sethos

[Marshmallowman]

The isotope they use is a beta emitter, not as biologically damaging as alpha particles.

I am trying to remember back to my physics..... I think a sheet of paper will stop most alpha particles, a sheet of aluminum foil(thick) will stop most beta particles, and a couple feet of lead will stop most gamma particles.

I guess a chunk of this stuff may be usable as portable power source with a small aluminum box for shielding.
But not in the configuration they use as it is set for mechanical energy conversion.

beta particles are electrons so if you use the block of isotope as the anode and an "beta particle/electron catcher" as a kathode you should be able to generate some current, but I think the current would not be enough to power a PDA, maybe it could power a watch for 50 years or so .

[Dr Mordrid]

Alpha (helium nuclei) can usually be stopped by paper/cardboard.

Beta (fast electrons) can be stopped by varying thicknesses of aluminum.

Gammas (photons whose energies start just beyond ultraviolet) are usually shielded by a few millimeters of lead at the 20 KeV to 120 KeV energies used for diagnostic radiology, but can require 3 feet of concrete + several inches of lead or more at the 1.13 to 1.5 MeV energies used for most radiation therapy.

Ni63's beta (electron) energy is only 0.067 MeV beta.

Dr. Mordrid

[Marshmallowman]

yes that sounds right,. but for nonmedical gamma ray sources you get some energies well of over 10MeV.

X ray equipment(high voltage generating of gamma rays) can produce gama rays in the range form 0.020Mev to 25 Mev, the higher end would only used for industrial x-raying.

Some Radiactive isotopes produce gamma rays of a lot higher energies

the range of gammas is 1 MeV - 10 GeV

anything over that is classed as cosmic rays.

In some areas of astronomy/astrophysics they are talking about energies for cosmic rays over a TeV.

but I digress...I will see if I can calculate the required amount of Ni63 to power a PDA...lets say about 100ma.

[Marshmallowman]

for 1watt PDA (something like 100ma consumption)

approx 0.5grams for 100 year lifetime, or 0.0625grams for 12.5 year lifetime, assumeing perfect conversion of energy and no perfect capture of all particles.

Realistically you would be lucky to use 0.1%(0.1% capture may be a bit optimistic) of the available electrons since most would lose the energy inside the bulk of the material so you would need somthing like 60 grams, then factor in conversion inefficiencies gives you about a 100 grams of NI63 per battery to power a PDA for about 10 years...

My simple electron catcher which lost most of the electrons energy and only used the equivlent of approx 10 volts per electron would require 2000 kg for a 100year lifetime , or only 250 kg for 12 years. ....damn no prize for me