why cant we dispose our nuclear waste in this way?
A Nuclear Probe to Explore Earth’s Interior
31–40 of 67 posts
Re: A Nuclear Probe to Explore Earth’s Interior
#32What a fascinating proposition. FYI: This blog article is from 2013 and is about scientific papers written in 2008 and 2005. A few minutes of cursory Googling turns up nothing else.
"... and they were never heard from again!"
Re: A Nuclear Probe to Explore Earth’s Interior
#33"Subsequent re-crystallisation of the molten material will generate intense acoustic signals." Why would it make any noise?
I imagined to be like ice which does make crackling noises when it freezes due to expansion, except cooling rocks will shrink causing the same. Re-solidifying rock would probably sound louder and the acoustic signature may travel further.
Re: A Nuclear Probe to Explore Earth’s Interior
#34Did this go anywhere? The only papers if find that reference the original ideas (2005 and 2008) mention nuclear waste that melts itself into the Earths core.
Probably not. That's a scary thing to build. Cobalt-60 gammas are hard to shield, and 2000K is really hot. The laws of physics don't forbid building such a thing, but I wouldn't want to be in the same building with it. Okay, so you have something that's so self-heating that it'll easily melt rock. In fact, it's hot enough that it self-liquifies quickly at STP. Cobalt reacts weakly with oxygen, but you'll still have t…
I spoke too-quickly regarding the radioactive shielding requirements, they're more manageable than I thought [1]. For the 10-cm thick tungsten wall, following [1], it looks like the shielding factor is ~25,000. That's more significant than it sounds, because only the gammas emitted at the surface of the cobalt see that shielding factor. The rest are better shielded, up to factors of 10^11 in the best case (propagating all the way across the sphere).
It's still a spooky thing to assemble, but it does appear that if the shielding is preserved, that it could be done without ridiculous quantities of assembly/launch shielding.
Re: A Nuclear Probe to Explore Earth’s Interior
#35A Caltech professor, David Stevenson, proposed a temperature-resistant probe immersed in a blob of molten iron: Stevenson, David J. Mission to Earth's Core - A Modest Proposal. Nature, 423, 239-240, 2003a. No radioactivity necessary, and the PDF is here: http://mathcs.albion.edu/~mbollman/Honors/ToTheCore!.pdf
Re: A Nuclear Probe to Explore Earth’s Interior
#36"transform some of the energy from radioactive decay" Not so simple. You need a hot source and a cold sink to transform energy. Where's your cold sink? This thing is intended to melt what's around it, and the outside of the probe is not that different in temperature from the inside.
Erm. If it's melting the rock around it, then the rock is your cold sink. By the time the temperature of the rock catches up with the probe, it's already molten anyway.
The rock would not work as a cold sink - the cold rock is too far from the probe. The rock right near the probe is at almost the exact same temperature.
Re: A Nuclear Probe to Explore Earth’s Interior
#37The article also suggests using the probe to analyze the composition of other planets. Is that doable? It seems pretty tough to me to carry on a space ship a nuclear probe hot enough to melt rocks.
If we're to the point where we're even considering this, presumably we're in a position to obtain the materials from either local sources, or possibly asteroid sources. This presumes a level of tech much higher than our current one since at our current one we can barely land probes that can drill semi-aimlessly into rocks. (And don't get me wrong, that's a hell of an achievement that gives me the Warm Science Fuzzies that we can pull it off... but it's also a long way from being able to do this sort of probe on other planets.)
Re: A Nuclear Probe to Explore Earth’s Interior
#38"transform some of the energy from radioactive decay" Not so simple. You need a hot source and a cold sink to transform energy. Where's your cold sink? This thing is intended to melt what's around it, and the outside of the probe is not that different in temperature from the inside.
Co-60 decays via beta (and then gamma) decay. It's a straightforward matter to convert the beta decay into electrical power.
Is it really that simple? You can't have any active electronics - they would melt.
And the tungsten is touching the cobalt, with no air gap (i.e. to opportunity to harvest power from the electrons returning to the cobalt to neutralize charge).
How would you harvest the electrons?
Re: A Nuclear Probe to Explore Earth’s Interior
#39Earlier quoted context omitted.
Co-60 decays via beta (and then gamma) decay. It's a straightforward matter to convert the beta decay into electrical power.
Is it really that simple? You can't have any active electronics - they would melt. And the tungsten is touching the cobalt, with no air gap (i.e. to opportunity to harvest power from the electrons returning to the cobalt to neutralize charge). How would you harvest the electrons?
Of course it's not simple, it's a very challenging project. But in terms of providing electrical power, if it's possible to have electronics that work at all then it would be possible to power them via beta decay. This is already an established technology in the form of "betavoltaics", which have powered existing devices (such as pace makers) in the past.
Re: A Nuclear Probe to Explore Earth’s Interior
#40> As the probe descents deeper, the rate of descent will gradually slow until the probe reaches a depth of 100 km after ~30 years The article doesn't mention - why will the probe stop descending?
Increase in density as you get closer to the core.
On top of which gravity is going to lessen as you get to the center of mass, so even a little resistance will eventually become extremely significant...