Fusion Energy is Dirty: Learn about Negative Implications

[Enthalpy]

Hello nice people!

As we all know, nuclear fusion energy in a tokamak power plant has to regenerate the tritium it burns, if fusion is to replace most fission reactors.
We all now as well that this implies a neutron multiplier at the blankets, for which lead seems to be the only candidate.

Sadly, nuclear fusion including tritium regeneration is as dirty as fission, because neutrons bombarding lead make radioactive products.

Here it goes.

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In the desired reaction, one 14MeV neutron produced by D-T fusion hits a lead nucleus, two neutrons emerge, and are absorbed at low energy by one ⁶Li each to make two tritium atoms. The neutron-lithium reaction also adds its own 5MeV, so one tritium cycle brings 25MeV now.

Tables of reactions, neutron cross-sections, radioisotopes there:
- Handbook of Chemistry and Physics, sure
- The Inaugural-Dissertation by Peter Reimer (= PhD thesis, as English Pdf on the web)
- http://www.matpack.de/Info/Nuclear/Nuclids/P/Pb.html

You guessed, the shaken lead atom leaves other products... Here are just two undesireable reactions, roughly estimated by hand; investigating more would bring more cases.

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²⁰⁴Pb makes 1.4% of natural Pb. The neutron doubling process is efficient (2.1b over 5.3b at 14MeV) and leaves ²⁰³Pb, which decays in 2.2 days by electron capture of 0.97MeV with gamma emission.

²⁰⁶Pb makes 24% of natural Pb. When hit by a 14MeV neutron, it sometimes emits an alpha to leave ²⁰³Hg, which decays in 47 days by beta- with a 0.28MeV gamma. Section for this production is only 0.7mb over 5.3b at 14MeV but ²⁰⁶Pb is abundant.

1.4% abundance or 0.7mb reaction section may look rather small, but:
- ²³⁵U gives ¹³¹I in 2.8% and ¹³⁷Cs in 6.1% of the fission events;
- Fission of ²³⁵U brings 200MeV. It takes 8 times more D-T and n-Li reactions to produce as much heat and electricity.
Combine both, you get as much ²⁰³Pb as ¹³¹I per MW of electricity output.

Now, one may argue that isotopes 204 and 206 could be removed from Pb...
- Well, no. Never completely. Changing a concentration by a factor of 10 is already a big effort, but 10 times less pollutants is still far too much.
- I'm confident other pollutants are produced by the isotopes 207 and 208, like ²⁰⁴Tl.
- I only checked neutrons with 14MeV as they're emitted. As they thermalise before being used by ⁶Li, more reactions occur.
- Such reactions look inherent to tritium regeneration.

In a leak of hot coolant, a 16% Li / 84% Pb eutectic, I imagine lithium ignites in air (or doesn't it?), with the fire releasing in the atmosphere the contained pollutants.

-----

This pollution is known from fusion researchers, as for instance the PhD thesis by Peter Reimer concentrates on such reactions - but maybe this aspect hasn't been publicized enough up to now...

So we should reach the consensual conclusion:
Stop wasting the valuable time of precious researchers on ITER! Fusion needs unavailable fuel or is dirty. Instead of unrealistic dreams, concentrate on serious technology, like renewable energy.

Marc Schaefer, aka Enthalpy

 

[Joseph Chikva]

Fusion energy will be cleaner than fission but you are right is not totally clean.

In the desired reaction, one 14MeV neutron produced by D-T fusion hits a lead nucleus, two neutrons emerge, and are absorbed at low energy by one ⁶Li each to make two tritium atoms. The neutron-lithium reaction also adds its own 5MeV, so one tritium cycle brings 25MeV now.

We need only about 25% neutrons breeding not 100% as you mentioned.

Instead of unrealistic dreams, concentrate on serious technology, like renewable energy.

Renewable technologies impact environment as well.
Now while we don't feel that as the share of renewable energy in our power balance is small.
For example HPP plants break ecology of reservoirs.
Wide use of wind and sun power will entail climate change. As they consume the energy that usually before was used in natural climate cycles. So, break of those cycles.
Besides all last two demand very big room for placing. That is reduces the sowed areas and therefore we inevitably will get a rise of prices on foodstuff.

 

[Borek]

Instead of unrealistic dreams, concentrate on serious technology, like renewable energy.

You are assuming renewable energy is not an unrealistic dream, and you are stating it as a fact. Do you have any sources to support this statement?

 

[aquitaine]

Renewable energy is an even bigger pipe dream than fusion ever was. At least with fusion once the engineering challenges have been overcome it offers major benefits that will make it worthwhile. It's really about effectively controlling the enormous amounts of energy produced.

Do you have any sources to support this statement?

As I recall this was almost exactly what Greenpeace said about fusion a few years back. Could have been that.

 

[cloa513]

Hello nice people!

As we all know, nuclear fusion energy in a tokamak power plant has to regenerate the tritium it burns, if fusion is to replace most fission reactors.
We all now as well that this implies a neutron multiplier at the blankets, for which lead seems to be the only candidate.

Sadly, nuclear fusion including tritium regeneration is as dirty as fission, because neutrons bombarding lead make radioactive products.

Here it goes.

-----

In the desired reaction, one 14MeV neutron produced by D-T fusion hits a lead nucleus, two neutrons emerge, and are absorbed at low energy by one ⁶Li each to make two tritium atoms. The neutron-lithium reaction also adds its own 5MeV, so one tritium cycle brings 25MeV now.

Tables of reactions, neutron cross-sections, radioisotopes there:
- Handbook of Chemistry and Physics, sure
- The Inaugural-Dissertation by Peter Reimer (= PhD thesis, as English Pdf on the web)
- http://www.matpack.de/Info/Nuclear/Nuclids/P/Pb.html

You guessed, the shaken lead atom leaves other products... Here are just two undesireable reactions, roughly estimated by hand; investigating more would bring more cases.

-----

²⁰⁴Pb makes 1.4% of natural Pb. The neutron doubling process is efficient (2.1b over 5.3b at 14MeV) and leaves ²⁰³Pb, which decays in 2.2 days by electron capture of 0.97MeV with gamma emission.

²⁰⁶Pb makes 24% of natural Pb. When hit by a 14MeV neutron, it sometimes emits an alpha to leave ²⁰³Hg, which decays in 47 days by beta- with a 0.28MeV gamma. Section for this production is only 0.7mb over 5.3b at 14MeV but ²⁰⁶Pb is abundant.

1.4% abundance or 0.7mb reaction section may look rather small, but:
- ²³⁵U gives ¹³¹I in 2.8% and ¹³⁷Cs in 6.1% of the fission events;
- Fission of ²³⁵U brings 200MeV. It takes 8 times more D-T and n-Li reactions to produce as much heat and electricity.
Combine both, you get as much ²⁰³Pb as ¹³¹I per MW of electricity output.

Now, one may argue that isotopes 204 and 206 could be removed from Pb...
- Well, no. Never completely. Changing a concentration by a factor of 10 is already a big effort, but 10 times less pollutants is still far too much.
- I'm confident other pollutants are produced by the isotopes 207 and 208, like ²⁰⁴Tl.
- I only checked neutrons with 14MeV as they're emitted. As they thermalise before being used by ⁶Li, more reactions occur.
- Such reactions look inherent to tritium regeneration.

In a leak of hot coolant, a 16% Li / 84% Pb eutectic, I imagine lithium ignites in air (or doesn't it?), with the fire releasing in the atmosphere the contained pollutants.

-----

This pollution is known from fusion researchers, as for instance the PhD thesis by Peter Reimer concentrates on such reactions - but maybe this aspect hasn't been publicized enough up to now...

So we should reach the consensual conclusion:
Stop wasting the valuable time of precious researchers on ITER! Fusion needs unavailable fuel or is dirty. Instead of unrealistic dreams, concentrate on serious technology, like renewable energy.

Marc Schaefer, aka Enthalpy

Those are pretty short half lives not the some really long half lives of the wide range of radioactive fission products (far more than the two you mentioned) let alone the heavily irradiated plant.
Sure the fusion plant will need shielding and sealing off- its a high energy plant.
The Lead won't decay as given as its constantly being irradiated with neutrons. I assume they would use a thin layer to maximise effectiveness.

 

[Joseph Chikva]

Those are pretty short half lives not the some really long half lives of the wide range of radioactive fission products (far more than the two you mentioned) let alone the heavily irradiated plant.
Sure the fusion plant will need shielding and sealing off- its a high energy plant.
The Lead won't decay as given as its constantly being irradiated with neutrons. I assume they would use a thin layer to maximise effectiveness.

Absolutely right!

 

[cloa513]

Radiation damage of lead would be incredibly well studied- along with steel and concrete its been the radiation particular X-ray shield of choice for over 50 years.

 

[Drakkith]

I can fix this thread real quick.

"Fusion energy is cleaner than fission in the long run, is much safer, but still has its own hazards to deal with just like anything."

 

[Joseph Chikva]

By the way I recall that tritium is produced just now for firearms tritium sights:
http://en.wikipedia.org/wiki/Tritium_illumination
http://xssights.com/index.php?nID=sights&cID=Sights&pID=sights&sID=tactical
And many modern armies widely use those.
I think that tritium is produced by using of neutron flux of existing fission reactors.
And considered here difficulties in its production by my opinion are exaggerated and not so dangerous and dirty as it paint here.

 

[clancy688]

"Fusion energy is cleaner than fission in the long run, is much safer, but still has its own hazards to deal with just like anything."

Probably the best and most truthful statement regarding fusion energy I've ever heard.

 

[Drakkith]

Could a D-D fuel be used as a "source" for tritium? Meaning that could we efficiently produce tritium using the fusion products from D-D and also a lithium blanket while using any produced heat and alpha particles to provide some source of electricity, making the process more efficient? This of course assumes equal containment and such as a D-T reactor that could produce net power output.

 

[Joseph Chikva]

Could a D-D fuel be used as a "source" for tritium? Meaning that could we efficiently produce tritium using the fusion products from D-D and also a lithium blanket while using any produced heat and alpha particles to provide some source of electricity, making the process more efficient? This of course assumes equal containment and such as a D-T reactor that could produce net power output.

Yes we can produce tritium in D-D reactor using lithium blanket.
Also we can build hybrid fusion-fission reactors. But the last would make a little sense.

 

[Drakkith]

Would it make sense to retrofit current plants with something to produce tritium?

 

[Joseph Chikva]

Would it make sense to retrofit current plants with something to produce tritium?

I doubt that that for economic reason that would expedient.
But if we need tritium for some applications (e.g. firearms tritium sights), so we need neutrons source. And we can produce tritium in existing nuke plants.

 

[Drakkith]

I meant retrofit existing nuke plants to produce it.

 

[Joseph Chikva]

I meant retrofit existing nuke plants to produce it.

I think you are late as tritium sights are already used by hunters and soldiers of many armies.

 

[Drakkith]

*sigh* nevermind.

 

[westfield]

Hello nice people!

As we all know, nuclear fusion energy in a tokamak power plant has to regenerate the tritium it burns, if fusion is to replace most fission reactors.
We all now as well that this implies a neutron multiplier at the blankets, for which lead seems to be the only candidate.

Sadly, nuclear fusion including tritium regeneration is as dirty as fission, because neutrons bombarding lead make radioactive products.

snip >

Marc Schaefer, aka Enthalpy

Isn't it rather unfair to brand fusion power in general as "dirty" while only referring to tokamak designs?

Correct me if I'm mistaken as I'm not up on the very latest in fusion power research but at this point in time we really cannot say with any certainty which design\s will prove to be practical for fusion power production, let alone which technology\s will end up being commercially viable.

So it's a little premature to make such pronouncements and call for an end to research isn't it? Doesn't seem very scientific at all.

 

[Joseph Chikva]

Isn't it rather unfair to brand fusion power in general as "dirty" while only referring to tokamak designs?

Correct me if I'm mistaken as I'm not up on the very latest in fusion power research but at this point in time we really cannot say with any certainty which design\s will prove to be practical for fusion power production, let alone which technology\s will end up being commercially viable.

So it's a little premature to make such pronouncements and call for an end to research isn't it? Doesn't seem very scientific at all.

Regardless the design more easy for realization D-T reaction requires neutron multiplying; its 14.1MeV neutron flux produces secondary radiation of first wall and support structures.
We already know that.
But as mentioned here those threats are much lower in comparison with existing fission reactors.
And instead of long-live high radioactivity wastes we will have lower quantity of short-live lower radioactivity.
Also fusion reactors will be less dangerous in case of accident if we take into account that fuel loading in fission reactors has a few years reserve and wastes also remain there till further reloading vs. in fusion reactor only current load of much less radioactive fuel is required and practically no wastes.
And so by realization fusion we can achieve the new much higher standard of industrial safety.

Renewable are not competitive to fusion as I mentioned earlier. Also wide usage of renewables would impact environment while fusion or fission reactors impact only in case of accidents.

 

[Khashishi]

The difference is that with fusion, the radioactivity will be gone in a few years, while with fission, you will still have radioactivity left over when the sun consumes the Earth.

Possibly, one of the alternative fusion devices will eventually use B11 + H reaction, which won't produce neutrons. But this seems pretty distant.

 

[Joseph Chikva]

Possibly, one of the alternative fusion devices will eventually use B11 + H reaction, which won't produce neutrons. But this seems pretty distant.

• D+He3 gives 18.3MeV having cross section resonance at 250keV
• p+B11 about 9MeV and resonance at 500keV
But yes - B11 is more available than He3

 

[Enthalpy]

About production of tritium by uranium reactors, please refer to the other thread:
https://www.physicsforums.com/showthread.php?t=422576
Fission produces much heat and little tritium (limited by the absolute maximum number of neutrons), using this tritium in a fusion reactor would add very little electricity to what the uranium reactors already produce - hence not worth it.

That's why people want to regenerate tritium at tokamaks, using lithium blankets.

These blankets need neutron multiplication because of a simple neutron bookkeeping problem.

Hence neutron multiplication by lead, which is dirty - the subject of the present thread.

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Lead blankets were used against gamma rays, but aren't the natural choice against neutrons. 14MeV neutrons aren't as widely studied as fission neutrons or as thermal neutrons. Hence the PhD thesis by Peter Reimer, in 2002 - not so old.

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I took here two examples only of radionuclides produced in these blankets. For instance ²⁰⁴Tl would have a longer life. Compare with ¹³¹I which has 8 days half-life and is enough of a problem, so a quick decay isn't a good excuse.

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Aneutronic fusion is completely out of reach of tokamaks for now, as is D-D. They may exist in encyclopaedia and courses, but tokamak researchers don't even indicate a number of centuries to harness these reactions. Sorry for the nice dreams.

Laser inertial fusion doesn't publish much about using such reactions, but Z-striction does, yes. Though, I'm very cautious about the Z-machine's results, because exploring electricity production is not its aim, and because people there seem to like sensational results.

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ITER is sold to the public as "limitless and clean energy" and this doesn't fit with the huge radioactivity (not just "its own difficulties": please check the activity produced, it's equal to a uranium reactor!) produced when regenerating the lacking tritium.

 

[Joseph Chikva]

About production of tritium by uranium reactors, please refer to the other thread:
https://www.physicsforums.com/showthread.php?t=422576
Fission produces much heat and little tritium (limited by the absolute maximum number of neutrons), using this tritium in a fusion reactor would add very little electricity to what the uranium reactors already produce - hence not worth it.

That's why people want to regenerate tritium at tokamaks, using lithium blankets.

These blankets need neutron multiplication because of a simple neutron bookkeeping problem.

Hence neutron multiplication by lead, which is dirty - the subject of the present thread.

-----

Lead blankets were used against gamma rays, but aren't the natural choice against neutrons. 14MeV neutrons aren't as widely studied as fission neutrons or as thermal neutrons. Hence the PhD thesis by Peter Reimer, in 2002 - not so old.

-----

I took here two examples only of radionuclides produced in these blankets. For instance ²⁰⁴Tl would have a longer life. Compare with ¹³¹I which has 8 days half-life and is enough of a problem, so a quick decay isn't a good excuse.

-----

Aneutronic fusion is completely out of reach of tokamaks for now, as is D-D. They may exist in encyclopaedia and courses, but tokamak researchers don't even indicate a number of centuries to harness these reactions. Sorry for the nice dreams.

Laser inertial fusion doesn't publish much about using such reactions, but Z-striction does, yes. Though, I'm very cautious about the Z-machine's results, because exploring electricity production is not its aim, and because people there seem to like sensational results.

-----

ITER is sold to the public as "limitless and clean energy" and this doesn't fit with the huge radioactivity (not just "its own difficulties": please check the activity produced, it's equal to a uranium reactor!) produced when regenerating the lacking tritium.

As i know Z-machine is more promoted as X-rays source. And not as fusion concept. A number of Tungsten wires gives very intensive pinch but due to high atom number very intensive braking radiation. I heard about idea to combine Z-machine with pulse light ions accelerators. But do not know will that idea be checked or no.

It would be difficult for me to speak more about other fusion concepts as I am proposing a new one. And sure in its viability. Even in more complicated D-He3 reaction case. That would not be a nice dream.

 

[Drakkith]

ITER is sold to the public as "limitless and clean energy" and this doesn't fit with the huge radioactivity (not just "its own difficulties": please check the activity produced, it's equal to a uranium reactor!) produced when regenerating the lacking tritium.

You must be misunderstanding something that was designed for the average person. ITER can LEAD to limitless and clean energy. It itself will NOT be producing any electricity for use. It is merely a stepping stone to future breakthroughs and such. In addition, it is already well known that D-T fuel produces a huge neutron flux. Materials are being researched and developed that can accommodate this flux while staying less dangerous than current materials.

Hence neutron multiplication by lead, which is dirty - the subject of the present thread.

You clearly show that your view of "clean" is NOT what is meant when fusion is referred to as clean energy. Looking at the long term situation fusion is MUCH cleaner than fission. Even the isotopes released in an incident are far less dangerous than fission is.

There is no such thing as "clean" energy in the absolute context. Making solar panels, windmills, dams, ETC all require the manufacturing of materials. None of this is perfectly clean.

Edit: After closer reading of your posts, it seems to me that nuclear power, whether fission or fusion, will never be clean enough for you as long as ANY radiation is produced. If that is your view then you should go away and stop posting this nonsense. This isn't a forum for your personal views, but for scientific fact. Evidence has shown that Fusion is MUCH cleaner than Fission in every realistic use of the term "Cleaner". Unless you have actual questions about something, then go away.

 

[minerva]

Could you elucidate exactly why the lead blanket is required?

For every tritium nucleus consumed in D-T fusion, a neutron is emitted, which can regenerate another triton in a reaction with Li-6 - or two neutrons, in a reaction with Li-7.

In a leak of hot coolant, a 16% Li / 84% Pb eutectic, I imagine lithium ignites in air (or doesn't it?), with the fire releasing in the atmosphere the contained pollutants.

Li is less chemically reactive than Na, so the safety concerns with liquid Li are even less than those associated with the present use of liquid Na in fast-spectrum fission reactors, and we have plenty of experience with doing that safely.

The difference is that with fusion, the radioactivity will be gone in a few years, while with fission, you will still have radioactivity left over when the sun consumes the Earth.

Nonsense. There is no radioactivity left over from the 1.7 billion-year-old fission reactors at Oklo.

 

[nikkkom]

I meant retrofit existing nuke plants to produce it.

A CANDU reactor produces about a kilogram of tritium per year.