author seemed a bit concerned about Pu-238 being used for weapons, but I think that's the wrong isotope (238 being not fissile, as well as physically hot)
How do plutonium-powered pacemakers work?
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Re: How do plutonium-powered pacemakers work?
#12I did not know about these. They are so cool! I wonder how long a plutonium-powered cell phone could operate...
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 fairly easily but it can get big. Here's the one used in Mars Curiosity rover [1].
[1] https://en.wikipedia.org/wiki/Multi-Mission_Radioisotope_The...
People talk about using isotopes from nuclear waste for this kind of thing a lot but they're usually considered too expensive.
Re: How do plutonium-powered pacemakers work?
#13Dumb 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.
That's true but isn't 80% of our energy usage used to heat and regulate our body temp? I was wondering if we would then need less "food" for daily calories...
Re: How do plutonium-powered pacemakers work?
#14I did not know about these. They are so cool! I wonder how long a plutonium-powered cell phone could operate...
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 stirling engine approach). And well... its hot. And how old is your phone? I don't think my 20 year old phone would still work... why charge power it with something that would last 30 years when the technology that drive it is gone in half a decade.
Re: How do plutonium-powered pacemakers work?
#15How long to these pacemakers last? Have people had to get the plutonium "batteries" replaced?
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 as well replace the whole unit and get all new parts rather than put an old one back in that may be reaching MTTF.
As for how long the cells last, modern Lithium Thionyl Chloride cells last 5-10 years depending on the pacemaker. They probably actually last longer, manufacturers are pretty conservative with lifetime estimates.
As for plutonium supplies like those in the article, they don't really die since they're thermoelectric. The amount of current you can draw will be proportional to the amount of heat generated by the isotope and the temperature gradient. Since the heat is related to the amount of isotope remaining, the power available will follow an exponential decay. The half-life of Pu-238 is about 88 years, so the battery will last a very long time. The exact lifetime depends on how much current the pacemaker takes to operate.
Most people had these devices replaced with more modern versions, but there are still a few people who have the old plutonium devices which were implanted decades ago.
Re: How do plutonium-powered pacemakers work?
#16FTA: > I wondered if there wasn't also worry about plutonium being recovered for weapons use, but the risk seems much smaller The answer here is a simple "nope." Plutonium in radioisotopic thermal generators is always Plutonium-238 with a 87.7 year half-life. You can't make bombs out of it. The fissile isotopes of Plutonium are 239 (24,000 year half-life) and 241 (14 year half-life, but a beta emitter instead of alph…
It sounds to me like it's only a simple "nope" if the only weapons you are worried about are nuclear weapons.
Pu-238 could still be useful for radiological weapons such as dirty bombs. If you're worried about them then it becomes a (slightly) more nuanced, "How many morgues do I have to raid, and can I do it before the authorities catch on to the Crematorium Bandit?"
Re: How do plutonium-powered pacemakers work?
#17Earlier quoted context omitted.
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.
That's true but isn't 80% of our energy usage used to heat and regulate our body temp? I was wondering if we would then need less "food" for daily calories...
Isn't heat essentially a by-product of muscles "burning" the glucose? I'm not sure we actually need more heat besides what's already being generated as a by-product.
Re: How do plutonium-powered pacemakers work?
#18Dumb 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.
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 electrochemical gradient directly, and then use it to power the ATP synthase and subsequent glucose-production mechanisms.
Re: How do plutonium-powered pacemakers work?
#19FTA: > I wondered if there wasn't also worry about plutonium being recovered for weapons use, but the risk seems much smaller The answer here is a simple "nope." Plutonium in radioisotopic thermal generators is always Plutonium-238 with a 87.7 year half-life. You can't make bombs out of it. The fissile isotopes of Plutonium are 239 (24,000 year half-life) and 241 (14 year half-life, but a beta emitter instead of alph…
I don't think adding half lifes here has any point. Fission is (as you mentioned yourself correctly) initiated by an external agent and half life (to my knowledge) has no relationship with "fissility" (as it relates to chain reaction)
Re: How do plutonium-powered pacemakers work?
#20FTA: > I wondered if there wasn't also worry about plutonium being recovered for weapons use, but the risk seems much smaller The answer here is a simple "nope." Plutonium in radioisotopic thermal generators is always Plutonium-238 with a 87.7 year half-life. You can't make bombs out of it. The fissile isotopes of Plutonium are 239 (24,000 year half-life) and 241 (14 year half-life, but a beta emitter instead of alph…
In fact to create weapons-grade Pu, you need to remove as much Pu-238 as you can, because if Pu-238 is contaminating your Pu, its high fission rate means the bomb explodes too early in the implosion process.