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There are two directions within the energy world that I don't completely get. One of them is hydrogen storage, the other nuclear fusion. From what I always und

There are two directions within the energy world that I don't completely get. One of them is hydrogen storage, the other nuclear fusion. From what I always understood is that the high-energy neutrons produced by the fusion reaction irradiate the surrounding structure and that there is still considerable nuclear waste (although lifetimes are better than with nuclear fission). Do the scientists not care or is this outdated info?

openasocket 9y ago
You're thinking of https://en.wikipedia.org/wiki/Neutron_activation https://en.wikipedia.org/wiki/Neutron_activation You need to use materials that stand up well to neutron bombardment. Many materials upon neutron capture have a half life measured in seconds, which isn't a big deal. As nuclear waste disposal goes, this really isn't a concern.
- MrQuincle 9y ago
  On this EU site they state that a site remains active for 50-100 years, https://www.euro-fusion.org/faq/does-fusion-give-off-radiation/ https://www.euro-fusion.org/faq/does-fusion-give-off-radiati.... I know it's better than fission, but still not nice. If is indeed seconds, then it doesn't matter of course. I was kind of hoping to understand more about material design in the recent scientific past with this question.
pm90 9y ago
The comparison is not b/w fusion and a hypothetical waste free source of energy. Its b/w fusion and fission. The waste products of fission are much more dangerous, expensive to handle and we still haven't found foolproof, effective ways of disposing them. OTOH, danger from irradiated materials (whatever that is, this is the first time I'm hearing this TBH) doesn't seem very pressing. I highly doubt any of the irradiated stuff would have a half life of millions of years.
- wbl 9y ago
  Half life is inversely proportional to radiation intensity. The big issue with fission waste products are the nucleotides radioactive enough to kill and long lived enough to be annoying, not the nasty ones that go away in a few decades or the almost inert ones.
  - xrange 9y ago
    Might as well put a Wikipedia link here about the fission product isotopes and their half lives: https://en.wikipedia.org/wiki/Nuclear_fission_product#Radioactivity_over_time https://en.wikipedia.org/wiki/Nuclear_fission_product#Radioa...
Symmetry 9y ago
The neutrons coming from the fusion reactor do have the potential to make the surrounding material radioactive. But that depends on exactly what the surrounding material is, some elements will become dangerous when exposed to neutrons and some won't. An important part of designing a fusion powerplant, and one of the reasons it is difficult, is that you have to make sure that the materials you use can safely handle the neutrons coming from the fusion reaction without transmuting into dangerously radioactive forms. This is in contrast to a fission reactor where the fuel itself turns into dangerously radioactive elements when exposed to neutrons. EDIT: The exception is that fusion powerplant designers will want to surround the reactor with lithium in the hopes that it will absorb a neutron and turn into tritium. The tritium is then carefully gathered because it forms the the fuel for the reactor and it's hard to get except in a nuclear reactor.
DennisP 9y ago
I saw a presentation by the head of MIT's fusion department, in which he said that the waste would only need to be contained for several decades. It's very different from fission, where the fuel itself produces long-lived high level waste. With the reactor discussed in this article, the situation is even better, because it would use boron fusion. That reaction doesn't produce neutron radiation at all. There'd just be a tiny amount from side reactions.

openasocket 9y ago

You're thinking of https://en.wikipedia.org/wiki/Neutron_activation https://en.wikipedia.org/wiki/Neutron_activation You need to use materials that stand up well to neutron bombardment. Many materials upon neutron capture have a half life measured in seconds, which isn't a big deal. As nuclear waste disposal goes, this really isn't a concern.

MrQuincle 9y ago
On this EU site they state that a site remains active for 50-100 years, https://www.euro-fusion.org/faq/does-fusion-give-off-radiation/ https://www.euro-fusion.org/faq/does-fusion-give-off-radiati.... I know it's better than fission, but still not nice. If is indeed seconds, then it doesn't matter of course. I was kind of hoping to understand more about material design in the recent scientific past with this question.

pm90 9y ago

The comparison is not b/w fusion and a hypothetical waste free source of energy. Its b/w fusion and fission. The waste products of fission are much more dangerous, expensive to handle and we still haven't found foolproof, effective ways of disposing them. OTOH, danger from irradiated materials (whatever that is, this is the first time I'm hearing this TBH) doesn't seem very pressing. I highly doubt any of the irradiated stuff would have a half life of millions of years.

wbl 9y ago
Half life is inversely proportional to radiation intensity. The big issue with fission waste products are the nucleotides radioactive enough to kill and long lived enough to be annoying, not the nasty ones that go away in a few decades or the almost inert ones.
- xrange 9y ago
  Might as well put a Wikipedia link here about the fission product isotopes and their half lives: https://en.wikipedia.org/wiki/Nuclear_fission_product#Radioactivity_over_time https://en.wikipedia.org/wiki/Nuclear_fission_product#Radioa...

Symmetry 9y ago

The neutrons coming from the fusion reactor do have the potential to make the surrounding material radioactive. But that depends on exactly what the surrounding material is, some elements will become dangerous when exposed to neutrons and some won't. An important part of designing a fusion powerplant, and one of the reasons it is difficult, is that you have to make sure that the materials you use can safely handle the neutrons coming from the fusion reaction without transmuting into dangerously radioactive forms. This is in contrast to a fission reactor where the fuel itself turns into dangerously radioactive elements when exposed to neutrons. EDIT: The exception is that fusion powerplant designers will want to surround the reactor with lithium in the hopes that it will absorb a neutron and turn into tritium. The tritium is then carefully gathered because it forms the the fuel for the reactor and it's hard to get except in a nuclear reactor.

DennisP 9y ago

I saw a presentation by the head of MIT's fusion department, in which he said that the waste would only need to be contained for several decades. It's very different from fission, where the fuel itself produces long-lived high level waste. With the reactor discussed in this article, the situation is even better, because it would use boron fusion. That reaction doesn't produce neutron radiation at all. There'd just be a tiny amount from side reactions.