What are the waste products from a deuterium and tritium fusion reaction?

In summary: Warren,Thanks for clearing that up. So the waste products from fusion reactions are not as dangerous as those from traditional fission reactions. However, we don't know what the waste products from a deuterium and a tritium reaction are yet.
  • #1
paulhunn
34
0
I have managed to find out that waste products from fusion reactions are far less dangerous than those from traditional fission reactions but i cannot find anywhere that states what the waste products actually are. Can somone please tell me what the waste products from a deuterium and a tritium reaction are?

Thanks

Paul
 
Engineering news on Phys.org
  • #2
paulhunn said:
I have managed to find out that waste products from fusion reactions are far less dangerous than those from traditional fission reactions but i cannot find anywhere that states what the waste products actually are. Can somone please tell me what the waste products from a deuterium and a tritium reaction are?
Paul,

We can't really say that right now.

First, the deuterium - tritium or D-T reaction that you are referring to is:

1D2 + 1T3 --> 2He4 + 0n1 + 17.6 MeV

That is deuterium + tritium --> Helium-4 + a neutron + energy.

The direct "waste products" are Helium-4 and the neutron. The Helium-4 is
nothing to be concerned about - it's ordinary stable Helium.

What is of concern is that 14.1 MeV neutron - or more specifically - what
that 14.1 MeV neutron hits. That's where the "waste" of a fusion reactor
is going to come from - the radioactivity induced by the neutron that comes
out ot the reaction. Since the designs aren't finalized - we're still trying to get
the reaction to work - we don't know what will be used to stop that neutron.

So unlike fission - where the waste products are the direct result of the reaction,
in fusion, the waste products are an indirect result of the reaction - so we can't
really say what they will be with 100% certainty as of yet.

Dr. Gregory Greenman
Physicist
 
  • #3
From the fusion reaction itself, there are no 'waste' products, in the sense that the products can be used. He (helium) can be collected and the neutrons provide energy in whatever they absorbed.

D + T -> n (14.1 MeV) + He4 (3.5 MeV).

The 14.1 MeV neutrons irradiate the surrounding structure, and when the neutron is ultimately absorbed, the absorbing nuclide generally becomes radioactive In this sense, fusion does produce waste products in the form of irradiated (and activated) structural materials, which ultimately have to be disposed in some appropriate facility.

In a DT plasma, there will like be some D+D reactions, of which half produce p + T and the other half produce n + He3.

T is radioactive by the way, and it must be kept out of the environment.
 
Last edited:
  • #4
Thanks for the replies. I understand it now.
 
  • #5

My understanding is that the entire fusion reactor is a 'nuclear fusion waste product'.
 
Last edited:
  • #6
How much Helium will be produce by fusion process in fusion power generator (assuming they are operational)? Will it be a lot? Because this might lead to increase concentration in atmosphere after a lot of year of running like CO2. High concentration of helium can be dangerous because helium is a simple asphyxiant(http://en.wikipedia.org/wiki/Asphyxiant) [Broken].

What to do with those Helium after they are collected?

Related:
http://en.wikipedia.org/wiki/Helium#Precautions
 
Last edited by a moderator:
  • #7
darkar said:
How much Helium will be produce by fusion process in fusion power generator (assuming they are operational)? Will it be a lot?
darkar,

If we assume a typical 1000 Mw(e) generator; meaning a 3000 Mw(t) thermal heat
source which is the fusion reactor; then in one year it will produce about 450 kgs
or less 1000 lbs of He-4.

This amount is TRIVIAL compared to the thousands of TONS of exhaust gases in
fossil plants.

Helium is non-toxic. The only way Helium hurts you is if the concentration is so high
that it displaces the oxygen you need.

Helium is a non-problem here.

Dr. Gregory Greenman
Physicist
 
  • #8
The "waste helium" is not an issue at all, and certainly not because it's an asphyxiant. Futhermore, helium released to the atmosphere escapes very quickly into space.

If anything, helium is becoming a precious substance. Our current supply of helium is dependent upon fossil fuels (nuclear reactions in the somewhat radioactive oil deep underground releases helium, which becomes trapped in pockets with the oil and natural gas). When the fossil fuels are gone, so will be our direct source of helium.

- Warren
 
  • #9
Astronuc said:
... In this sense, fusion does produce waste products in the form of irradiated (and activated) structural materials, which ultimately have to be disposed in some appropriate facility.

...

Allow me to qualify for benefit of the OP: There are 'aneutronic' reactions, or reactions that do not produce any neutrons; the energy is released instead by alpha particles which can be captured by electromagnetic fields and in general are much less of radiation hazard. Examples include proton + Boron 11. Note that ITER type Tokamaks are not capable of burning these fuels because they require higher reaction energies, hence the reason one doesn't here much discussion of aneutronic fuels. Example ~110keV for P-11B vs ~15KeV for D-T.
 
Last edited:
  • #10
mheslep said:
Allow me to qualify for benefit of the OP: There are 'aneutronic' reactions, or reactions that do not produce any neutrons; the energy is released instead by alpha particles which can be captured by electromagnetic fields and in general are much less of radiation hazard. Examples include proton + Boron 11. Note that ITER type Tokamaks are not capable of burning these fuels because they require higher reaction energies, hence the reason one doesn't here much discussion of aneutronic fuels. Example ~110keV for P-11B vs ~15KeV for D-T.
Not to mention Z(B) = 5, which means fairly high brehmstrahlung losses for a given plasma temperature, and high electron pressures if one tries to fully ionize B, and also recombination and cyclotron rad losses. P-B11 would be great, but for the limitations.

Another aneutronic reaction D-He3 still has other issues, such as there is still the D-D reaction which does produce He3+n in 50% of reactions and T+p in the other half. T+D would still lead to [tex]\alpha[/tex] + n.
 
  • #11
darkar said:
How much Helium will be produce by fusion process in fusion power generator (assuming they are operational)? Will it be a lot? Because this might lead to increase concentration in atmosphere after a lot of year of running like CO2. High concentration of helium can be dangerous because helium is a simple asphyxiant(http://en.wikipedia.org/wiki/Asphyxiant) [Broken].

What to do with those Helium after they are collected?

Related:
http://en.wikipedia.org/wiki/Helium#Precautions
Helium is a noble gas. How can it be an asphyxiant? If you breathe it, it just makes you talk funny. CO2, on the other hand, in sufficient concentration (eg. 5%) will interfere chemically with hemoglobin transport of oxygen in the blood. I don't see how Helium can do this. If you breathe nothing but He for long enough, of course, you will die from lack of oxygen.

AM
 
Last edited by a moderator:
  • #12
Andrew Mason said:
How can it be an asphyxiant? ...
If you breathe nothing but He for long enough, of course, you will die from lack of oxygen.
Andrew,

You answered your own question. You don't need a chemical reaction to have an
asphyxiant. If the gas just displaces enough oxygen; it will asphyxiate you.

That's how a lot of fire-suppression systems protecting computers, electronic equipment...
whatever; work. The system pumps in enough nitrogen, CO2, ...anything but oxygen;
and the fire is "smothered" which is the analog to asphyxiation.

Asphyxia is merely the lack of oxygen that results in unconsciousness or death.

Dr. Gregory Greenman
Physicist
 
  • #13
Astronuc said:
Not to mention Z(B) = 5, which means fairly high brehmstrahlung losses for a given plasma temperature, and high electron pressures if one tries to fully ionize B, and also recombination and cyclotron rad losses. P-B11 would be great, but for the limitations.

Another aneutronic reaction D-He3 still has other issues, such as there is still the D-D reaction which does produce He3+n in 50% of reactions and T+p in the other half. T+D would still lead to [tex]\alpha[/tex] + n.

I found this forum looking for info on plasma physics, info that I need to understand a little the works of a IEC fusor of the Bussard type, i.e. a Polywell*. I think that Bussard claims that the Bremsstrahlung losses in the core of the polywell are very low, as the high electron density make the electron cloud (Wiffle Ball) in the center of the device to behave as a diamagnetic medium, and expelling the magnetic field used to create the virtual cathode. As I have formal education on nuke physics and technology, but not on high-energy nor plasma physics, I don't know if that claim is reasonable.

What are the thoughts of the forum?

Thanks a lot.

Caveat: I'm not sure about Bussard work, or its interpretation by his followers, not being junk science. There are rumors about Bussard preparing a 120-page paper to expose his last 11 years work.

* See http://askmar.com/ConferenceNotes/Should%20Google%20Go%20Nuclear.pdf" [Broken] for the paper presented in 57th International Astronautic Congress. The paper is very skimpy, as it doesn't contain the "hard" physics required to explain how the thing works.
 
Last edited by a moderator:
  • #14
sunday said:
I found this forum looking for info on plasma physics, info that I need to understand a little the works of a IEC fusor of the Bussard type, i.e. a Polywell*. I think that Bussard claims that the Bremsstrahlung losses in the core of the polywell are very low, as the high electron density make the electron cloud (Wiffle Ball) in the center of the device to behave as a diamagnetic medium, and expelling the magnetic field used to create the virtual cathode. As I have formal education on nuke physics and technology, but not on high-energy nor plasma physics, I don't know if that claim is reasonable.
sunday,

It's GARBAGE!

Bremsstrahlung doesn't require magnetic fields; it only requires that the charge is
accelerated. With lots of electron-electron interaction at high electron density; there
certainly is going to be Brehmsstrahlung losses.

Dr. Gregory Greenman
Physicist
 
  • #15
Morbius said:
Paul,

We can't really say that right now.

First, the deuterium - tritium or D-T reaction that you are referring to is:

1D2 + 1T3 --> 2He4 + 0n1 + 17.6 MeV

That is deuterium + tritium --> Helium-4 + a neutron + energy.

The direct "waste products" are Helium-4 and the neutron. The Helium-4 is
nothing to be concerned about - it's ordinary stable Helium.

What is of concern is that 14.1 MeV neutron - or more specifically - what
that 14.1 MeV neutron hits. That's where the "waste" of a fusion reactor
is going to come from - the radioactivity induced by the neutron that comes
out ot the reaction. Since the designs aren't finalized - we're still trying to get
the reaction to work - we don't know what will be used to stop that neutron.

So unlike fission - where the waste products are the direct result of the reaction,
in fusion, the waste products are an indirect result of the reaction - so we can't
really say what they will be with 100% certainty as of yet.

Dr. Gregory Greenman
Physicist


Could radioactive nuclear waste absorb these neutrons, becoming less radioactive or perhaps even be used as fuel?
 
  • #16
ensabah6 said:
Could radioactive nuclear waste absorb these neutrons, becoming less radioactive or perhaps even be used as fuel?
ensabah6,

YES - in fact one of the goals of the GNEP - Global Nuclear Energy Partnership is to
produce fast "actinide burner" reactors. A reactor along the road of the design of
Argonne's Integral Fast Reactor or IFR, which was canceled back in 1994; would go
along way in reducing radioactivity of nuclear waste.

First, nuclear fuel should be reprocessed - it's really DUMB to have nuclear waste which
is 90+% U-238; no more radioactive than when it was dug out of the ground.

Secondly, plutonium in spent nuclear waste should be recycled to power reactors as fuel
to eliminate a constituent of nuclear waste with a 24,000 year half life.

Third, we should have "burner" reactors along the lines of the Argonne IFR concept.

This would alleviate much of the nuclear waste problem.

If the only waste that we have to dispose of is fission products; the longest lived fission
product of any consequence Cs-137; has a half-life of just 30 years.

For more on the Argonne IFR, see the transcript of an interview PBS's Frontline did with
Argonne's Dr. Charles Till:

http://www.pbs.org/wgbh/pages/frontline/shows/reaction/interviews/till.html

Dr. Gregory Greenman
Physicist
 
  • #17
Morbius said:
You answered your own question. You don't need a chemical reaction to have an
asphyxiant. If the gas just displaces enough oxygen; it will asphyxiate you.

It could be somewhat worse than that. The breathing mechanism is, I understand, not driven by lack of oxygen, (even if that is the body's crying need), but by level of CO2. A real good lungfull of any inert gas asphyxiant could leave one incapable of re-starting if partly overcome, and without resuscitation help.

Breathing Xenon to get the deep low voice effect is now questionable as a teaching experiment, though the same concerns maybe do not extend to squeaky-voice helium.

I am also not so sure about chroot's belief - though I don't know for sure..
Futhermore, helium released to the atmosphere escapes very quickly into space.
Helium is lighter than air, but would only get to rise to the top of the atmosphere if enough were contained in a balloon or something to displace more than its weight in atmosphere. Released straight into the air, it seems to simply mix with it.

While leak testing a vacuum furnace, I was impressed how very little helium, less than needed for a party balloon, could ping around the whole 2 industrial factory units and the car park also, in less than a second. We had to wait 20 minutes for it to disperse before the mass spectrometer instrument stopped squealing!

I guess atmospheric gases are lost into space, but I don't think we will run out anytime soon.
 
  • #18
Waste amount

"This theory is what someone else told me". I'd like to know the actual possibility of this. (Radiation effects on the structural materials are the critical problem with commercial level fusion power (although tritium sequestration from the environment is important as well). High energy neutron bombardment of the vacuum containment shell both converts the material to long life radionuclides and causes the material to *swell* (microscopic gas bubbles) and become brittle.
Even using steels with high rare Earth alloy percentages, a production fusion reactor would have to be shut down for replacement of its containment shell every few years, and the radioactive removed materials stored as nuclear waste.
The only option is free space shielding -- keeping the fusion reaction far enough away that the radiation is at acceptable levels. 93 million miles is generally accepted as a known safe point, as long as we also have a functioning ozone belt.)
 
  • #19
GTrax said:
Helium is lighter than air, but would only get to rise to the top of the atmosphere if enough were contained in a balloon or something to displace more than its weight in atmosphere. Released straight into the air, it seems to simply mix with it.

...

I guess atmospheric gases are lost into space, but I don't think we will run out anytime soon.

Helium is different because it has low atomic mass - not only does it rise above air, it will escape from the atmosphere. The rate of loss is very sensitive to atomic mass: the distribution of particle speeds has an exp(-m*v^2) term, so it is exponentially sensitive. The rate of loss is (I assume) proportional to the fraction that is above escape velocity.

http://en.wikipedia.org/wiki/Maxwell-Boltzmann_distribution#Distribution_of_speeds

Hence, oxygen and nitrogen, but negligible helium (even though helium is generated continuously in the Earth's crust).
 
  • #20
mheslep said:
Allow me to qualify for benefit of the OP: There are 'aneutronic' reactions, or reactions that do not produce any neutrons; the energy is released instead by alpha particles which can be captured by electromagnetic fields and in general are much less of radiation hazard. Examples include proton + Boron 11.

This is not entirely achievable because the components will also react in unwanted, neutronic reactions. For instance, in p+11B, you have p+p->D+e+v and D(n,y)T, hence D+T fusion on the side.

Edit: it seems other side reactions are more important

http://en.wikipedia.org/wiki/Aneutronic_fusion#Residual_radiation_from_a_p.E2.80.9311B_reactor
 
  • #21
signerror said:
This is not entirely achievable because the components will also react in unwanted, neutronic reactions. For instance, in p+11B, you have p+p->D+e+v and D(n,y)T, hence D+T fusion on the side.

Edit: it seems other side reactions are more important

http://en.wikipedia.org/wiki/Aneutronic_fusion#Residual_radiation_from_a_p.E2.80.9311B_reactor
The p+p->D cross section is extremely low relative to p+11B so we get less than 0.1% residuals, which practically does away w/ the activated first wall problem in D+T, D+D fusion.
 
  • #22
Astronuc said:
From the fusion reaction itself, there are no 'waste' products, in the sense that the products can be used. He (helium) can be collected and the neutrons provide energy in whatever they absorbed.

D + T -> n (14.1 MeV) + He4 (3.5 MeV).

The 14.1 MeV neutrons irradiate the surrounding structure, and when the neutron is ultimately absorbed, the absorbing nuclide generally becomes radioactive In this sense, fusion does produce waste products in the form of irradiated (and activated) structural materials, which ultimately have to be disposed in some appropriate facility.
This may be a dumb question but why would one let the 14.1 MeV neutron be absorbed by a heavy nucleus and create useless/dangerous radioactive elements? Why not surround the reactor with a moderator of light or heavy water the to absorb the 14.1 MeV neutron energy and produce heat and then eventually capture the slowed neutron (to produce deuterium or tritium which can then be used for more fusion)? It should be a zero sum - for each neutron produced from a D-T reaction you can produce another D or T nucleus which can then be fed into the fusion reactor.

AM
 
  • #23
Andrew Mason said:
This may be a dumb question but why would one let the 14.1 MeV neutron be absorbed by a heavy nucleus and create useless/dangerous radioactive elements? Why not surround the reactor with a moderator of light or heavy water the to absorb the 14.1 MeV neutron energy and produce heat and then eventually capture the slowed neutron (to produce deuterium or tritium which can then be used for more fusion)? It should be a zero sum - for each neutron produced from a D-T reaction you can produce another D or T nucleus which can then be fed into the fusion reactor.

AM
Two reasons:
1. Some kind of higher Z wall is required to hold the water/ or whatever.
2. The neutrons must be used to breed tritium to maintain the fuel cycle (as you suggest). Current plan is do this with a lithium blanket behind the wall. I had thought fast neutrons were needed for that, but I don't know.
 
  • #24
mheslep said:
Two reasons:
1. Some kind of higher Z wall is required to hold the water/ or whatever.
2. The neutrons must be used to breed tritium to maintain the fuel cycle (as you suggest). Current plan is do this with a lithium blanket behind the wall. I had thought fast neutrons were needed for that, but I don't know.
That's pretty much it. There needs to be a 'first wall' or structural vessel that encases the plasma, which operates in a vacuum. Water (or similar fluid) would simply evaporate in the vacuum and quench the plasma. And the first wall materials will eventually become activated.

Stainless steels are affected by (n,p), (n,α) and the p's and α's accumulate interstially, although H forms metal hydrides. The other effect is clusters of dislocations, which can be annealed out. Ni-58 can undergo an (n,p) reaction which produces Co-58, or Ni-58 absorbs the n, and produces Ni-59 which decays to Co-59, which can absorb a neutron and become Co-60.

There has been a big research project at ORNL on first wall materials, which also has relevancy to traditional steel pressure vessels and core structures of LWRs and fast reactors.

Lithium could actually flow inside the first wall, but that's tricky. The issue is the n(6Li,α)T and the effect of the α on the plasma, which is why it would be necessary to confine it outside the first wall. There's also the issue of confining T, and recovering it. Li-7 can be used as a coolant since it has a lower cross-section for n-absorption.

An aneutronic reaction e.g. d+3He would be ideal, but it's problematic given the cost and low abundance of 3He.
 
  • #25
Astronuc said:
That's pretty much it. There needs to be a 'first wall' or structural vessel that encases the plasma, which operates in a vacuum. Water (or similar fluid) would simply evaporate in the vacuum and quench the plasma. And the first wall materials will eventually become activated.

Stainless steels are affected by (n,p), (n,α) and the p's and α's accumulate interstially, although H forms metal hydrides. The other effect is clusters of dislocations, which can be annealed out. Ni-58 can undergo an (n,p) reaction which produces Co-58, or Ni-58 absorbs the n, and produces Ni-59 which decays to Co-59, which can absorb a neutron and become Co-60.

There has been a big research project at ORNL on first wall materials, which also has relevancy to traditional steel pressure vessels and core structures of LWRs and fast reactors.

Lithium could actually flow inside the first wall, but that's tricky. The issue is the n(6Li,α)T and the effect of the α on the plasma, which is why it would be necessary to confine it outside the first wall. There's also the issue of confining T, and recovering it. Li-7 can be used as a coolant since it has a lower cross-section for n-absorption.

An aneutronic reaction e.g. d+3He would be ideal, but it's problematic given the cost and low abundance of 3He.
I can see lithium working because the nuclear mass is low, so it has a moderating effect - converting neutron energy into heat. That was my point. You don't want nuclei that will absorb the fast neutrons. You want to have material inside the first wall that will convert neutron energy to heat.

AM
 
  • #26
Andrew Mason said:
I can see lithium working because the nuclear mass is low, so it has a moderating effect - converting neutron energy into heat. That was my point. You don't want nuclei that will absorb the fast neutrons. You want to have material inside the first wall that will convert neutron energy to heat.
Andrew,

If you absorb the neutron - you are going to get the heat energy. Where else would the energy
of the neutron go?

You have a fast moving neutron, and it is absorbed by a nucleus - so now you have just a new
compound nucleus. Where did the momentum and kinetic energy of the neutron go?

It has to go to that compound nucleus. The nucleus is going to originally get that energy; and
if you have a solid; the new compound nucleus is constrained from moving too far by its neighbors;
so the kinetic energy of the nucleus will diffuse to the neighbors, which are also constrained by their
neighbors, so the energy diffuses - and all the atoms now have a bit more energy.

That's heat. It's not just light nuclei that give you heat.

Dr. Gregory Greenman
Physicist
 
  • #27
Andrew Mason said:
I can see lithium working because the nuclear mass is low, so it has a moderating effect - converting neutron energy into heat. That was my point. You don't want nuclei that will absorb the fast neutrons. You want to have material inside the first wall that will convert neutron energy to heat.

AM
There are two possible results from a neutron interaction with a nucleus, either it scatters or it is absorbed. The vast majority of high energy neutrons will scatter, and in doing so, the neutron loses some energy and goes on to his other nuclei. Now the nuclei that get struck are displaced in the metal crystals, and that is the radiation damage that embrittles a metal. We refer to displacements per atom (dpa) as a measure of irradiation damage in a metal, and it is this measurement which is correlated with mechanical behavior and degradation of mechanical properties of metal, particular low temperature embrittlement. The neutron and gamma radiation will certainly heat the first wall, and that is one reason that the material must have high temperature strength and melting point. One deleterious effect of irradiation damage is spalling in which the first wall flakes and falls into the plasma chamber. The objective is to use materials which do not spall.

As for neutron absorption, the issue there is activation of the structural material, which become radioactive, and also changes the chemical nature of the nucleus upon beta decay, or ejection of a charged particle, p or α.
 
  • #28
Morbius said:
Andrew,

If you absorb the neutron - you are going to get the heat energy. Where else would the energy of the neutron go?

You have a fast moving neutron, and it is absorbed by a nucleus - so now you have just a new compound nucleus. Where did the momentum and kinetic energy of the neutron go?

It has to go to that compound nucleus. The nucleus is going to originally get that energy; and if you have a solid; the new compound nucleus is constrained from moving too far by its neighbors; so the kinetic energy of the nucleus will diffuse to the neighbors, which are also constrained by their neighbors, so the energy diffuses - and all the atoms now have a bit more energy.

That's heat. It's not just light nuclei that give you heat.
Quite right. But I was thinking more of the efficiency. Neutrons bouncing off heavy nuclei would not impart much energy per collision so one would need many more collisions to absorb that energy - ie. a much thicker wall of heavy nuclei would be needed in order to convert the neutron energy into heat. Perhaps one could put a thick shield of depleted uranium around the core to absorb the fast neutrons - at least then the neutron capture could produce useable plutonium fuel for a fission reactor. But I expect that the DU would not withstand the high temperature.

AM
 
  • #29
Andrew Mason said:
...Perhaps one could put a thick shield of depleted uranium around the core to absorb the fast neutrons - at least then the neutron capture could produce useable plutonium fuel for a fission reactor. But I expect that the DU would not withstand the high temperature.

AM
The major selling points of fusion over fission include nearly eliminating radioactive waste and little or no weapons proliferation risk. Take that away and as I understand the issue there's little to recommend fusion over fission at all until all the U and Th deplete in, what, 500 years?
 
  • #30
mheslep said:
... until all the U and Th deplete in, what, 500 years?
At current rates of extraction we have about 30 years supply in known reserves so we probably will have 40-50 years supply before serious shortages occur. That is, unless we start reprocessing fuel - then we have probably 10000 years supply.

AM
 
  • #31
Andrew Mason said:
Quite right. But I was thinking more of the efficiency. Neutrons bouncing off heavy nuclei would not impart much energy per collision so one would need many more collisions to absorb that energy
Andrew,

So then you need 0.0001 sec to absorb the energy instead of 0.00001 sec to absorb the energy.

What's the problem?

Dr. Gregory Greenman
Physicist
 
  • #32
Andrew Mason said:
Perhaps one could put a thick shield of depleted uranium around the core to absorb the fast neutrons - at least then the neutron capture could produce useable plutonium fuel for a fission reactor.
Andrew,

Or you could do what the LIFE program at Lawrence Livermore National Laboratory proposes; you put
a layer of fuel pebbles - the same pebbles that are used in a pebble bed reactor. The layer of fuel pebbles
is a sub-critical assembly; but it is driven by the high energy neutrons from the fusion reaction. Rather
than just absorbing the energy of the fast neutrons; you use those neutrons to trigger more fissions so
that you MULTIPLY the production of energy by the sub-critical multiplication factor of the sub-critical
assembly of fuel pebbles:

https://lasers.llnl.gov/missions/energy_for_the_future/life/ [Broken]

https://lasers.llnl.gov/missions/energy_for_the_future/life/how_life_works.php [Broken]

Dr. Gregory Greenman
Physicist
 
Last edited by a moderator:
  • #33
mheslep said:
The major selling points of fusion over fission include nearly eliminating radioactive waste and little or no weapons proliferation risk.
mheslep,

Actually, if a nation wants to develop nuclear weapons; they can use neutrons from a fusion reactor
to make plutonium every bit as effectively as with a fission reactor.

It is a MYTH that fusion is inherently more proliferation resistant, or waste resistant than fission.

That myth comes from people that look at the byproducts of a fusion reaction and see, for example;
a He-4 and a neutron. They stop thinking right there and say - Helium-4 and neutrons are not long
lived waste nor useful for weapons - therefore fusion is waste-resistant and proliferation-resistant.

However, if you think one more step; whatever that neutron hits will most likely be activated and hence
constitute a radioactive material that needs to be dealt with. Additionally, that neutron can be used to
breed plutonium and hence can be used for nuclear weapons proliferation.

Dr. Gregory Greenman
Physicist
 
  • #34
Morbius said:
mheslep,

Actually, if a nation wants to develop nuclear weapons; they can use neutrons from a fusion reactor
to make plutonium every bit as effectively as with a fission reactor.

It is a MYTH that fusion is inherently more proliferation resistant, or waste resistant than fission.

That myth comes from people that look at the byproducts of a fusion reaction and see, for example;
a He-4 and a neutron. They stop thinking right there and say - Helium-4 and neutrons are not long
lived waste nor useful for weapons - therefore fusion is waste-resistant and proliferation-resistant.

However, if you think one more step; whatever that neutron hits will most likely be activated and hence
constitute a radioactive material that needs to be dealt with.
IIRC in comparison to spent fuel rods D-T fusion waste from high Z first wall materials is still low rad, short half life material.

Additionally, that neutron can be used to
breed plutonium and hence can be used for nuclear weapons proliferation.

Dr. Gregory Greenman
Physicist
An argument for more aneutronic fusion research? IRC that was Lidsky's argument in the 'The Trouble with Fusion'.

I don't agree the two, fission and fusion, are equivalent in proliferation risk. Granted one can make Pu by inserting U into a neutron producing fusion reactor (though the practicality is not clear to me). The point is practical weapons production regardless of the process still requires U up front. Fusion power completely eliminates the need for U; thus a country attempting to acquire U is unmistakably stating "I am making a weapon" and can be dealt with accordingly. More importantly it robs the enablers, like a Russia or China, from pretending otherwise when they sell fission technology and materials to want to be weapons states.
 
  • #35
mheslep said:
I
I don't agree the two, fission and fusion, are equivalent in proliferation risk. Granted one can make Pu by inserting U into a neutron producing fusion reactor (though the practicality is not clear to me). The point is practical weapons production regardless of the process still requires U up front. Fusion power completely eliminates the need for U; thus a country attempting to acquire U is unmistakably stating "I am making a weapon" and can be dealt with accordingly.
mheslep,

If you think they are not an equivalent risk - then you are not up on the studies that labs such as LLNL
have conducted. Besides, the proliferation concern is really a "red herring". The number of nuclear armed
nations that got to be nuclear armed by co-opting a commercial nuclear power program is exactly ZERO!
When nations decide they want to have nuclear weapons - they build purpose-built facilities like production
reactors to produce bomb fuel. Getting bomb fuel out of a commercial power program is just too expensive
and technically demanding.

Uranium is EVERYWHERE! Uranium is one of the most UNIFORMLY distributed elements in the
Earths crust. Dig up a football field sized area to a depth of about 6 feet practically anywhere and you
can can get a few kilograms of Uranium.

No country would have ANY problem obtaining natural uranium - which is what can be transmuted into
weapons grade material. Practically ANY country has enough uranium within its own borders for bombs.

The only reason countries need Russia or China is to get enriched uranium - either slightly enriched for
power reactors or something of higher enrichment for research reactors.

Dr. Gregory Greenman
Physicist
 
Last edited:
<h2>What are the waste products from a deuterium and tritium fusion reaction?</h2><p>The waste products from a deuterium and tritium fusion reaction are mainly helium and neutrons.</p><h2>Why are helium and neutrons the main waste products?</h2><p>During a deuterium and tritium fusion reaction, the nuclei of these two elements combine to form a helium nucleus, releasing a large amount of energy. Additionally, neutrons are also produced due to the high energy collisions between the nuclei.</p><h2>Are there any other waste products besides helium and neutrons?</h2><p>In addition to helium and neutrons, small amounts of other elements such as tritium, helium-3, and hydrogen may also be produced as byproducts of the fusion reaction. However, these are typically present in very small quantities.</p><h2>What happens to the waste products after a fusion reaction?</h2><p>The helium and other byproducts from a deuterium and tritium fusion reaction are typically released into the surrounding environment. The neutrons, on the other hand, can be captured by a surrounding material to produce heat, which can then be used to generate electricity.</p><h2>Are the waste products harmful to the environment?</h2><p>The waste products from a deuterium and tritium fusion reaction are not considered harmful to the environment. Helium is a non-toxic and non-reactive gas, while the other byproducts are produced in such small quantities that they do not pose a significant threat. The neutrons, however, can be dangerous if not properly contained, but measures are taken to ensure their safe capture and use in generating electricity.</p>

What are the waste products from a deuterium and tritium fusion reaction?

The waste products from a deuterium and tritium fusion reaction are mainly helium and neutrons.

Why are helium and neutrons the main waste products?

During a deuterium and tritium fusion reaction, the nuclei of these two elements combine to form a helium nucleus, releasing a large amount of energy. Additionally, neutrons are also produced due to the high energy collisions between the nuclei.

Are there any other waste products besides helium and neutrons?

In addition to helium and neutrons, small amounts of other elements such as tritium, helium-3, and hydrogen may also be produced as byproducts of the fusion reaction. However, these are typically present in very small quantities.

What happens to the waste products after a fusion reaction?

The helium and other byproducts from a deuterium and tritium fusion reaction are typically released into the surrounding environment. The neutrons, on the other hand, can be captured by a surrounding material to produce heat, which can then be used to generate electricity.

Are the waste products harmful to the environment?

The waste products from a deuterium and tritium fusion reaction are not considered harmful to the environment. Helium is a non-toxic and non-reactive gas, while the other byproducts are produced in such small quantities that they do not pose a significant threat. The neutrons, however, can be dangerous if not properly contained, but measures are taken to ensure their safe capture and use in generating electricity.

Similar threads

Replies
3
Views
1K
  • Nuclear Engineering
Replies
9
Views
1K
  • Nuclear Engineering
Replies
4
Views
2K
  • High Energy, Nuclear, Particle Physics
Replies
14
Views
900
  • High Energy, Nuclear, Particle Physics
Replies
1
Views
1K
Replies
14
Views
2K
  • Science Fiction and Fantasy Media
Replies
16
Views
2K
  • Nuclear Engineering
Replies
7
Views
2K
  • High Energy, Nuclear, Particle Physics
Replies
4
Views
2K
  • High Energy, Nuclear, Particle Physics
Replies
6
Views
2K
Back
Top