Couldn’t we have a lead box lined with these radiation to electricity converters with a small amount of radioactive material in the center, and have an energy generating device that would last for thousands or even millions of years? Imagine putting the sun in a box lined with solar cells, but on a much smaller scale.
Is there a reason this wouldn’t work?
Yep, it's called a "radioisotope thermoelectric generator". Mostly used on satellites.
Related accident: https://en.wikipedia.org/wiki/Lia_radiological_accident
Three men in forest in Georgia during winter found mysterious sources of heat and decided to warm up using them. They turned out to be unlabeled RTG cores. One of the three died as a result of exposure.
The youtube channel @PlainlyDifficult has a whole playlist about "sources in the wild" that also covered this one and many other nuclear accidents and incidents.
Lot of comments about RTGs, but I don't think that's what OP is asking. RTGs convert heat to electricity, same as a conventional power plants — they just do it in a solid state way instead of steam. In RTGs it doesn't matter where the heat comes from; they are not really analogous to solar cells, as the title asks.
In fact, there are consumer products that use the same technology — you can buy a little electric fan that sits on top of a wood stove and, once up to temp, will start spinning. The electricity is generated by the thermal gradient using heat from the stove, essentially the same as an RTG.
No one has directly answered your question.
The answer is yes, you can create photovoltaic cells better optimise to pick up high energy light such as that from nuclear decay (gamma radiation). However, the power generated by photovoltaics is limited more by intensity of the light, and not the energy per photon (wavelength). For physical reasons is hard to capture the energy of high energy light, so gamma photovoltaics are low power concepts.
There is an idea going around to grow diamond with c14 and also harvest that c14 decay with a diamond based photovoltaic. Making everlasting batteries, albeit radioactive and microwatt. (Specifics are probably wrong, working from memory.)
Just mentioned the diamond thing in another comment, assuming you're also talking about the nano/nuclear diamond battery thing
Looking into it, it should be theoretically possible to get a material that decay into beta particles trapped in sphere that would gather these particles and thus electrically charge the sphere.
I don't see how you turn it on or off though, which might be a problem.
I think there a similar concept for providing energy to space missions built around a plutonium isotope.
And why turn it off? Even if the maximum output was only seldomly required, convert the excess energy into a reserve (like green hydrogen) would make sense.
There is the nano/nuclear diamond battery thing too, which is supposed to work like this but apparently produces very little energy if any
I worked up the energy to google. Turns out it's not a photovoltaic (gamma-voltaic?) anyway, it's a betavoltaic. I guess that makes more sense than the rubbish capture cross section of high energy light.
Scintillaton is another option. Use alpha and beta decay to push electrons up in their orbits, to decay and release a photon. Then capture and convert that photon to electricity with photovoltaics.
Yup, RTGs exist, but they're impractical for most terrestrial use cases. The problem is that any isotope that's energetic enough to generate meaningful amounts of energy is also going to be somewhere between quite dangerous and insanely dangerous if the container is breached. And unless there are very strong protocols in place for handling the RTG, on a long enough timeline, there's basically guaranteed to be a nuclear accident.
Since they also rely on the radioactive decay, the power output isn’t constant. It will also decay as time goes on. Sure, it will stay hot (not to mention completely lethal) for a very long time, but that might not be enough for all applications.
Maybe it was enough to keep a lighthouse operational for decades, but eventually it won’t be enough for that. What do you do with an RTG like that? Instead of powering a large light with that, you could probably power a smaller light or a small water pump. After a few more decades, that small pump is once again too powerful for your legacy RTG, so you’ll have to settle for running a smaller pump or a street light with it. It’s going to take a very long time until you get to that point, so it’s highly likely that the RTG will be forgotten, abandoned or stolen by then.
Yes and we already have and use them. Albeit only on NASA probes leaving earth.
Both of the curiosity rovers use this as their power plant. A bunch of plutonium sits in that little tail like stub on them and generates perpetual power for them.
To add to your answer, the reason they're not used on Earth, besides the radioactivity dangers, is that they just can't produce very much power.
Would it be a way to reuse nuclear waste?
The recycling process that France currently uses recovers about 96% of the radioactive material remaining in nuclear waste and produces new fuel rods usable in conventional reactors. Spent fuel rods from conventional reactors can also be used in other types of reactors. For whatever reason, we in the US just shove all of our nuclear waste in old mines like it's still 1950 but technology has continued to develop and places that are more invested in nuclear energy have much better ways of dealing with the waste.
Yes, with RTGs. They are used on mars rovers, for example.
