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Enthalpy

Fusion pollution (split from Where is deuterium and tritium found?)

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More fusion reactions exist, yes. But D-T is the only accessible to tokamaks presently. It's far less difficult than any other one because only one proton in D repels one proton in T. D-D reacts too but produces little heat as it releases the less stable 3He or T, and the reaction rate is 100 times less than D-T. Other fuels like Li or 3He are hugely more difficult. They work in hydrogen bombs, in some inertial confinement setups, but as a means of controlled net energy production they are out of reach.

==========

After ITER got >10 years late because of Covid-19, some sort of assembly was celebrated recently (2020, who cares about the month meanwhile).

As for the cost, present figures by the promoters fluctuate between 20 and 30G€. But the DOE, not significantly involved in this huge squandering, includes also the hardware developed by the participating countries and brought to ITER, to get >60G€ instead.

For an energy source as polluting as uranium fission and available half a century after wind turbines, ITER is an expensive scam.

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4 hours ago, Enthalpy said:

More fusion reactions exist, yes. But D-T is the only accessible to tokamaks presently. It's far less difficult than any other one because only one proton in D repels one proton in T. D-D reacts too but produces little heat as it releases the less stable 3He or T, and the reaction rate is 100 times less than D-T. Other fuels like Li or 3He are hugely more difficult. They work in hydrogen bombs, in some inertial confinement setups, but as a means of controlled net energy production they are out of reach.

==========

After ITER got >10 years late because of Covid-19, some sort of assembly was celebrated recently (2020, who cares about the month meanwhile).

As for the cost, present figures by the promoters fluctuate between 20 and 30G€. But the DOE, not significantly involved in this huge squandering, includes also the hardware developed by the participating countries and brought to ITER, to get >60G€ instead.

For an energy source as polluting as uranium fission and available half a century after wind turbines, ITER is an expensive scam.

 If it is a scam, that might tell us more about European Union than about nuclear fusion. From this single failure (of ITER) my first thought is that governments are incompetent, and only then that fusion might be a scam.... It will take several failures coming from different parties to convince me that fusion does not pay.

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4 hours ago, Enthalpy said:

For an energy source as polluting as uranium fission

Citation needed

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Posted (edited)
1 hour ago, Strange said:

Citation needed

Locally it's pretty hardcore.. I read just yesterday, after Dounray reactor is dismantled, the land won't be usable for 300 years or so.

Edited by StringJunky

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10 minutes ago, StringJunky said:

Locally it's pretty hardcore.. I read just yesterday, after Dounray reactor is dismantled, the land won't be usable for 300 years or so.

That wasn't a fusion reactor, though (which was what was being claimed).

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23 minutes ago, Strange said:

That wasn't a fusion reactor, though (which was what was being claimed).

Eh? Enthalpy said, to which I assumed you was replying: "For an energy source as polluting as uranium fission"

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1 hour ago, StringJunky said:

Eh? Enthalpy said, to which I assumed you was replying: "For an energy source as polluting as uranium fission"

The end of that referred to ITER. The citation needed is one showing that fusion is as polluting as fission.

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13 minutes ago, swansont said:

The end of that referred to ITER. The citation needed is one showing that fusion is as polluting as fission.

OK.

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On 8/21/2020 at 2:04 PM, John Cuthber said:

DD reactors exist. I'm thinking of making myself one as a toy.

https://en.wikipedia.org/wiki/Fusor

Hi JC!

D-D reactors, including fusors, achieve fusion. But they are energy consumers, not producers.

I've suggested smaller tokamaks fed with D only that consume energy to produce radioisotopes, especially for hospitals
http://www.scienceforums.net/topic/107732-tokamak-produces-radioisotopes/

Though, ITER claims to explore the way to energy production, then not with the too difficult D-D but with D-T.

 

On 8/21/2020 at 2:37 PM, Strange said:

Citation needed [for Enthalpy's "an energy source as polluting as uranium fission"]

The link to my estimates was in my message of November 30, 2014 but the website is closed meanwhile. So here is the full text, minimally rewritten.

==========

Examples here of pollutant production at a Pb–Li coolant meant to regenerate tritium. Doc in the Handbook of Chemistry and Physics and in Peter Reimer 's PhD thesis:
  kups.ub.uni-koeln.de   [In this folder]

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

206Pb makes 24% of natural Pb. When hit by a 14MeV neutron, it can emit an α to leave 203Hg, decaying in 47 days by β− with a 0.28MeV γ. Section for this production is only 0.7mb over 5.3b at 14MeV but 206Pb is abundant.

Investigating more would bring more cases.

1.4% abundance or 0.7mb reaction section may look rather small, but:

  • 235U produces 131I in 2.8% and 137Cs in 6.1% of the fission events;
  • Fission of 235U brings 200MeV. It takes 8× more D–T and n–Li reactions to produce as much heat. Combine both, you get as much 203Pb as 131I per MW.

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× less pollutants is still far too much.
  • I'm confident other pollutants are produced by 207Pb and 208Pb, 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, I imagine the 16% lithium ignite in air (or don't they?), with the fire releasing in the atmosphere the contained pollutants.

Marc Schaefer, aka Enthalpy

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25 minutes ago, Enthalpy said:

The link to my estimates was in my message of November 30, 2014 but the website is closed meanwhile. So here is the full text, minimally rewritten.

==========

Examples here of pollutant production at a Pb–Li coolant meant to regenerate tritium. Doc in the Handbook of Chemistry and Physics and in Peter Reimer 's PhD thesis:
  kups.ub.uni-koeln.de   [In this folder]

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

So it’s essentially gone in a few weeks, creating Tl -203, which is stable. Not a pollutant

 

25 minutes ago, Enthalpy said:

206Pb makes 24% of natural Pb. When hit by a 14MeV neutron, it can emit an α to leave 203Hg, decaying in 47 days by β− with a 0.28MeV γ. Section for this production is only 0.7mb over 5.3b at 14MeV but 206Pb is abundant.

Where are the 14 MeV neutrons coming from?

 

25 minutes ago, Enthalpy said:

Investigating more would bring more cases.

1.4% abundance or 0.7mb reaction section may look rather small, but:

  • 235U produces 131I in 2.8% and 137Cs in 6.1% of the fission events;
  • Fission of 235U brings 200MeV. It takes 8× more D–T and n–Li reactions to produce as much heat. Combine both, you get as much 203Pb as 131I per MW.

But 203 isn’t a pollutant, since it decays rapidly.

 

25 minutes ago, Enthalpy said:

Now, one may argue that isotopes 204 and 206 could be removed from Pb…

206 is stable. Why would it need to be removed?

 

25 minutes ago, Enthalpy said:
  • Well, no. Never completely. Changing a concentration by a factor of 10 is already a big effort. But 10× less pollutants is still far too much.
  • I'm confident other pollutants are produced by 207Pb and 208Pb, like 204Tl.
  • I only checked neutrons with 14MeV as they're emitted.

Emitted from what?

 

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3 hours ago, Enthalpy said:

But they are energy consumers, not producers.

OK.

We need to sort something out.
A single fusion event releases energy.

Without the fusor, you wouldn't have that energy..
So, any fusor is a net producer of heat.
If all you want to do is  heat your house then, by using a fusor, you can put about 1KW of power in and get about 1.0000000001 KW of heat out of it.

Obviously, that's not terribly economical- especially given the cost of heavy water. It's only really a very expensive toy.


But it's a net producer.

3 hours ago, swansont said:

Emitted from what?

Presumably D T fusion.

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1 hour ago, John Cuthber said:


So, any fusor is a net producer of heat.

“net production of heat” is not the same as “net production of energy” 

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1 hour ago, swansont said:

“net production of heat” is not the same as “net production of energy” 

Well, yes...

One of them is impossible because mass/ energy is a conserved quantity.

But, if you want to run a power station, what you need is a net release of heat.
Burning coal is a net producer of heat, but the energy was already there as chemical energy- stored up from when it was solar energy

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2 minutes ago, John Cuthber said:

Well, yes...

One of them is impossible because mass/ energy is a conserved quantity.

But, if you want to run a power station, what you need is a net release of heat.
Burning coal is a net producer of heat, but the energy was already there as chemical energy- stored up from when it was solar energy

A necessary but insufficient requirement. Your power station will go broke. 

And I can’t believe this has to be explained to you.

 

 

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19 hours ago, swansont said:

A necessary but insufficient requirement. Your power station will go broke. 

And I can’t believe this has to be explained to you

if I was building a power company...
But I'm building heaters.

It's a bit like using a heat  pump to heat the room- the "wasted" heat is still used so it isn't wasted and the overall efficiency is over 100%
Though I have to admit the CoP is not as good as a conventional air source heat pump (by about 9 orders of magnitude)

You don't need to explain things I already know. You need to explain to yourself what I'm seeking to achieve.

 

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!

Moderator Note

In order to avoid the need for another split I suggest to keep on-topic or start a new topic on heating systems.

 

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I am a big proponent of Fusion reactor power, and believe it is our future.
There are many technological obstacles in the way of that future.

The biggest obstacle is that we cannot replicate the solar process here on Earth.
That process relies on the vast central pressures generated by the gravity/mass of the Sun, and extremely high temperatures, to produce relatively harmless Helium.
We can however, react Deuterium-Deuterium much more readily, and Deuterium-Tritium even more so ( 24 orders of magnitude more reactive than H-H ).
So, naturally, if we are just going to investigate the concept, we start with Deuterium-Tritium, which requires the least pressure/temperature for reaction, but, has many associated problems.

See here        https://thebulletin.org/2017/04/fusion-reactors-not-what-theyre-cracked-up-to-be/

Once problems are ironed out, and technology develops sufficiently, we can move to investigating Deuterium-Deuterium fusion Reactors.
With the ultimate goal ( technology permitting eventually ) to realise Hydrogen-Hydrogen fusion Reactors.

If you're just learning to swim, you don't jump into the deep end of the pool.

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