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How do plutonium-powered pacemakers work?

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Re: How do plutonium-powered pacemakers work?

#61

Post by sargun »

acidburnNSA wrote: post #12
ComputerGuru wrote: post #9

Earlier quoted context omitted.

It wouldn’t really be feasible, the power requirements would require a large amount.

It probably wouldn't be feasible, mostly because if it got smashed by a car, a fairly potent alpha emitter would possibly be released, which is an ingestion and inhalation hazard. The radioisotope usually used (Pu238) is also not produced very much right now so it's in short supply. You make it in special Neptunium-237 targets inside nuclear reactors. In terms of power you can get well up into the hundreds of Watts f…

I wish it was easier to get your hands on refined isotopes. I believe it'd spawn quite a bit of interesting industrial research that's being held back right now. A lot of this waste is a nuisance, but I believe if it was easier to get access to it, we'd see someone start to solve the waste problem.

Re: How do plutonium-powered pacemakers work?

#64

Post by Retric »

gji wrote: post #24
shagie wrote: post #14

Earlier quoted context omitted.

Not that long... or rather, it could work for a very long time but wouldn't be that useful because of the low power provided. From Wikipedia - https://en.wikipedia.org/wiki/Radioisotope_thermoelectric_ge... Plutonium-238 has a half-life of 87.7 years, reasonable power density of 0.54 watts per gram - that's heat energy.And then there's math on that which has a rather low efficiency (somewhere around 23% for a stirlin…

Those numbers aren't that bad, actually. A cell phone's peak power draw isn't much more than 5W, so you'd need 10g / efficiency. At 10% efficiency, that's 100g, which is 5 cm^3 for plutonium. A cell phone battery is about 3 times that size, assuming 3000 mAh and an energy density of 600 Wh/L. Of course you'd have to build in a heat engine, but perhaps even a peltier would work given the generous efficiency allowance.

It's better than that. Normal iPhones have less than 8 watt hours of battery life, they simply don't need peak power much. 8/24 = 0.333w, you lose some to overhead but you also reduce power draw by 0.33w so that's a reasonable estimate. @ 20% efficient that's 1.65w of heat, but your also storing .3w so really only 1.35w of waste heat. That's a 30% heat production increase at peak which doesn't seem like a deal killer.

7 Plus has a ~30% larger battery, but can dump heat ever more area so not a big deal.

Re: How do plutonium-powered pacemakers work?

#65

Post by effie »

perlgeek wrote: post #47
acidburnNSA wrote: post #6

Earlier quoted context omitted.

The half-life of Pu-238 (the isotope used in these) is 87.7 years [1]. So they pretty much last a lifetime. For the same reason, Voyager 1 is still kicking even though it's out of the solar system [2]. [1] https://en.wikipedia.org/wiki/Plutonium-238 [2] https://en.wikipedia.org/wiki/Voyager_1

Still, Voyager 1 is slowly shutting down its scientific instruments due to decreased power supply. I highly recommend this podcast episode with one of the Voyager project managers: https://www.listentospacepod.com/episodes/2016/8/5/episode-5... (about 20 minutes long, iirc) (In fact, I'd highly recommend the whole podcast, not just this episode, but this one actually talks about power consumption and battery life of…

The project manager Suzy Dodd talks a lot about shutting down instruments in order to save the power. But the power output of radioisotope thermoelectric generator does not depend on how much power is drawn. Is there a conventional electric battery on the Voyagers that the instruments draw their power from instead?

Re: How do plutonium-powered pacemakers work?

#66

Post by joshschreuder »

rplnt wrote: post #60
Kelbit wrote: post #15

Earlier quoted context omitted.

Easier to replace the whole pacemaker than the battery, for a couple of reasons: * Pacemakers are hermetically sealed, usually laser-welded in a titanium case. Adding a replaceable battery with seals would complicate this arrangement. * By the time the battery winds down, there may be a newer, better pacemaker on the market that fits the patient's needs. * Since a battery replacement necessitates surgery, you might a…

Wouldn't wireless charging pad work well for this? Or is it unnecessary complicated considering how long batteries last?

I think the main problem is the giant meat sack sitting between the charging pad and battery :)

Re: How do plutonium-powered pacemakers work?

#67

Post by rplnt »

joshschreuder wrote: post #66
rplnt wrote: post #60

Earlier quoted context omitted.

Wouldn't wireless charging pad work well for this? Or is it unnecessary complicated considering how long batteries last?

I think the main problem is the giant meat sack sitting between the charging pad and battery :)

The main problem might be patents :)

Samsung includes charging of medical device[1] in their wireless charging patent. Although the patent[2] seems to focus on the charging method/devices, rather than where they are located.

1. http://patentimages.storage.googleapis.com/US20140084858A1/U...

2. http://www.google.com/patents/US20140084858

Re: How do plutonium-powered pacemakers work?

#68

Post by [deleted] »

WalterBright wrote: post #58
wolfgang42 wrote: post #18

Earlier quoted context omitted.

I went to a lecture recently by a researcher who is investigating the mechanisms of photosynthesis. The chlorophyll uses the energy from the photon to pump an electron, which (after a long and poorly-understood chain of reactions, which is what he was studying) creates an energy gradient which powers ATP synthase to produce ATP. Presumably if we understood and could recreate this reaction, we could create the electro…

Biochemists at Caltech were studying photosynthesis back in the 70s, with an eye towards artificially replicating the process. I see not much progress has been made.

[deleted]

Re: How do plutonium-powered pacemakers work?

#69

Post by maxerickson »

Rjevski wrote: post #5
fratlas wrote: post #4

Dumb question, but would it be possible to have a nuclear-powered object in your body producing energy for your body to use?

Keeping nuclear material (safely) in your body is the easy part, the hard part is converting that energy into something your body can use. The issue is, our (badly designed) meat-hardware runs on glucose instead of heat or electricity, and there's no easy (or any way that I know of really, but then I'm not a scientist) to convert heat/electricity into glucose.

You could "just" make a nuclear liver that snapped metabolic byproducts back together.

I guess you might not directly target the production of glucose, but there should be some places in the metabolism where food energy could be replaced with energy from the plutonium.

Re: How do plutonium-powered pacemakers work?

#70

Post by ianhowson »

rplnt wrote: post #60
Kelbit wrote: post #15

Earlier quoted context omitted.

Easier to replace the whole pacemaker than the battery, for a couple of reasons: * Pacemakers are hermetically sealed, usually laser-welded in a titanium case. Adding a replaceable battery with seals would complicate this arrangement. * By the time the battery winds down, there may be a newer, better pacemaker on the market that fits the patient's needs. * Since a battery replacement necessitates surgery, you might a…

Wouldn't wireless charging pad work well for this? Or is it unnecessary complicated considering how long batteries last?

Chest cavities aren't especially space-constrained, and another commenter mentioned that electrodes wear out fairly quickly (single-digit years), so it appears that a fixed non-rechargeable battery has enough capacity to last the lifetime of the device.

Wireless charging (for a pacemaker) has the issue that you've got to push the energy through quite a lot of flesh, with consequent efficiency and heat issues.

Wireless charging is absolutely an option for other devices implanted closer to the skin, though.

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