Radioactive diamonds as small batteries that last 5000+ years

[magnemoe]

  On 1/18/2017 at 11:04 PM, PB666 said:

You have just enough power to send a message into deep space like 'here is why we blew ourselves to kingdom come'.

In seriousness, however it could be used to send an reactivation signal or charge a capacitor that then activates recovery from dormancy. For example you could have two long lived radioisotopes that then when combined can generate power for dormant systems, thaw frozen cells, bring an artificial  prenatal incubator online,  . . . . . . . .add water and get humans.

This then makes interstellar travel for periods of 10,000s years possible (the halflife of C-14 is about 5000 years and its essentially useless after 40,000 years for dating).

 

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Think they used C14 as its easier to test this with something who is not highly radioactive. For anything practical they would use an far more radioactive material. 
Plutonium used in bombs has an 24000 year half life, the one in rtg has an 14 year half life. 
Think diamond is used because of the crystal structure, purpose here is to extract electricity directly from the alpha or beta decay. 
 

[p1t1o]

  On 1/19/2017 at 3:07 PM, wumpus said:

From the article, that is the idea.  You get the carbon from graphite rods used in [fission] reactors, then turn them into diamonds.

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Im not sure if that is it - what I got from the article was that diamond was exposed to radioactivity [of some flavour or another] and C14 recovered from spent fuel rods was one source of the radiation. Other tests used Nickel-63 as the source.

  On 1/19/2017 at 3:07 PM, wumpus said:

Which made me suspicious of the whole diamond business, although you would think "anything but plutonium*" would be enough for most people.  But diamond does have an extreme index of refraction (only some seriously exotic materials have more) so it might have advantages for at least trapping gamma rays (except that wiki claims that C14 decay involves beta emissions, which is unlikely to be effected).

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I dont recall any pertinent mathematics at the moment, but my gut says gamma refraction is unlikely, the absorption cross-section for gamma rays is just too small. I think it is more likely to involve the movement of charged particles, diamond having a nice covalent macro-structure seems to offer plenty of interaction pathways in that case. Its hard to tell though, without a journal reference.

  On 1/19/2017 at 3:07 PM, wumpus said:

* isn't the Plutonium used in RTGs a different isotope than the one used in bombs?  While there is the wildly hyped toxicity, it really isn't as bad as the 4-4-4 dangers you read about in "Ignition" (some of which are still used).

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Correct, Pu239 is used for bombs, Pu238 for things like RTGs. However, note that Pu238 is the *more* radioactive isotope - this makes it less suitable for bombs as it is more prone to "fizzle", ie: burst apart before significant chain reaction has occurred.

[wumpus]

  On 1/19/2017 at 4:01 PM, p1t1o said:

I dont recall any pertinent mathematics at the moment, but my gut says gamma refraction is unlikely, the absorption cross-section for gamma rays is just too small. I think it is more likely to involve the movement of charged particles, diamond having a nice covalent macro-structure seems to offer plenty of interaction pathways in that case. Its hard to tell though, without a journal reference.

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I was thinking more in terms of total internal refraction, but that would require the gamma rays coming from 25 degrees or less from the surface.  Possibly "gem cuts" will maximize this (except that they are designed for external light and get to angle it around coming in), but I'd still figure that any internally produced gamma-ray will have *tiny* chance of hitting this value (although it might be enough to melt the diamond without cooling, it just would be a relatively tiny percentage).  There is also the issue of internal refraction as well, but that would only multiply the standard chance of absorption by a relatively small integer.

[p1t1o]

  On 1/19/2017 at 4:28 PM, wumpus said:

I was thinking more in terms of total internal refraction, but that would require the gamma rays coming from 25 degrees or less from the surface.  Possibly "gem cuts" will maximize this (except that they are designed for external light and get to angle it around coming in), but I'd still figure that any internally produced gamma-ray will have *tiny* chance of hitting this value (although it might be enough to melt the diamond without cooling, it just would be a relatively tiny percentage).  There is also the issue of internal refraction as well, but that would only multiply the standard chance of absorption by a relatively small integer.

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You can bounce it around inside a diamond as much as you like, but it is going to have a very low probability of interacting with anything before it escapes. In order to create a potential difference, something with a charge has got to be moved.

***

Ah, this might help clear things up:

  Quote

Researchers are trying to improve the efficiency and are focusing on use of radioactive C-14, which is a minor contributor to the radioactivity of nuclear waste.^[8]

C-14 undergoes Beta decay giving non-radioactive Nitrogen and high energy Beta particles .

 614C → 714N + -10β

^[9]

These Beta particles having an average energy of 50keV on inelastic collisions with other carbon atoms create electron-hole pairs which then contribute to electric current. This statement can be restated in terms of band theory saying that due to high energy of the Beta particles, electrons in valance band of carbon crystal jump to its conduction bandleaving behind holes in the valance band where electrons were earlier present. ^[10] [11]

C-14 has been chosen as the source of radioactivity mainly because its beta-particle radiation is easily absorbed by any solid. The use of diamond, (one of the hardest solids on earth) will not only increase the quantity of current generated but will also prevent dangerous radiation from leaking out of the battery.^[12]

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I think a formal peer-reviewed paper yet to be published.

Edited January 19, 2017 by p1t1o

[John FX]

Pretty much no device needs maximum power all the time. Mostly they do nothing waiting for an time when they do a lot very quickly.

As someone above said, why not use them to trickle charge a storage device which is then used for powering the device?

Portable solar power works the same way, often you spend a week charging batteries for just a few hours usage.

If it saves even a few percent of weight and provides longer term power it`s a winner.

[wumpus]

  On 1/19/2017 at 4:34 PM, p1t1o said:

You can bounce it around inside a diamond as much as you like, but it is going to have a very low probability of interacting with anything before it escapes. In order to create a potential difference, something with a charge has got to be moved.

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My point was that at 25 degrees or less, it *doesn't* escape.  The issue is that very few photons will hit with such a shallow angle (I'm guessing something like sin(whatever 25 degrees is in radians)**2 will be a close percentage).  What interested me is that this angle is larger on diamond than just about any other substance.

[p1t1o]

  On 1/19/2017 at 4:41 PM, wumpus said:

My point was that at 25 degrees or less, it *doesn't* escape.  The issue is that very few photons will hit with such a shallow angle (I'm guessing something like sin(whatever 25 degrees is in radians)**2 will be a close percentage).  What interested me is that this angle is larger on diamond than just about any other substance.

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Well, mostly Im not convinced that gamma rays will be refracted in the same manner as lower frequencies, IIRC the refractive index of a material is specific to frequency. Diamond has a high refractive index for visible light, I dont think this holds all the way across the spectrum.

[Shpaget]

  On 1/19/2017 at 4:34 PM, p1t1o said:

C-14 has been chosen as the source of radioactivity mainly because its beta-particle radiation is easily absorbed by any solid. The use of diamond, (one of the hardest solids on earth) will not only increase the quantity of current generated but will also prevent dangerous radiation from leaking out of the battery

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But when beta particles slam into shielding they generate gamma rays.