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Alternative for lithium in Deuterium-Tritium fusion power

  1. Mar 14, 2019 at 8:48 AM #1
    Is there alternative ways for producing Tritium for fusion power plants other than using lithium?. In the wiki article about fusion power I read that Deuterium-Deuterium fusion produce Tritium so I wonder if this can be used as a way to produce tritium for Deuterium-Tritium fusion power plants in case there is a problem with lithium resources. Is Deuterium-Deuterium fusion even possible with current technology?.
     
  2. jcsd
  3. Mar 15, 2019 at 1:47 AM #2

    mfb

    Staff: Mentor

    D-D fusion is much harder to achieve than D-T. We don't even have D-T fusion at levels useful for a power plant.
     
  4. Mar 15, 2019 at 9:29 AM #3
    so D-D fusion is impossible with current technology or it is so problematic that we can't even do it to harvest tritium in a way that will be useful for D-T fusion power plants?. technological advancement might make D-D fusion a source for tritium for D-T fusion power plant without needing to figure out how to produce energy from D-D fusion?.
     
  5. Mar 15, 2019 at 9:38 AM #4

    anorlunda

    Staff: Mentor

    You don't need fusion to produce tritium. At one time, it was produced in bulk to make glow-in-the-dark watch hands.

    https://en.wikipedia.org/wiki/Tritium#Production_history
     
  6. Mar 15, 2019 at 10:57 AM #5

    mfb

    Staff: Mentor

    It is possible to get some fusion, but not in relevant quantities with existing or planned reactors.
    If we can use D-D fusion we can just leave the tritium in the plasma or put it back in (if it is kicked out), it will easily fuse with another deuterium nucleus.
    Not enough. A 1 GW (electric) power plant would need about 200 kg per year. All the tritium the US produced in 40 years could power a single reactor for a single year. Fusion power plants have to produce their own tritium, there is no other practical source for such a large amount.
     
  7. Mar 15, 2019 at 1:58 PM #6

    anorlunda

    Staff: Mentor

    Thank you @mfb. You are a valuable source of key numbers when we need them.
     
  8. Mar 16, 2019 at 12:24 PM #7

    Astronuc

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    Staff Emeritus
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    There is no practical alternative to lithium for tritium production. Other reactions are possible, but they require more energy input.

    Adding to what mfb stated above, I found a comment on one of my textbooks (Robert A. Gross, Fusion Energy, John Wiley & Sons, 1984) that a 1 GW (thermal) reactor would consume about 140 grams of T per day, or 51.1 kg T/year. So a larger plant (~1 GWe) with an efficiency of about 0.34 would require ~150 kg/yr, which is in the ballpark of 200 kg indicated by mfb. In 1981, T cost about $9000/g. Also, 1 g of T represents about 9600 Ci.

    D-D fusion would be ideal, however, whereas D-T fusion achieves a peak at a plasma temperature of ~ 50 keV (~58 million K), D-D doesn't achieve comparable activity until beyond 1000 keV (11.6 billion K). D-He3 has a peak reactivity of about 300 keV (3.5 billion K), but one has to content with greater radiation losses. Also, higher plasma temperature, the plasma density has to decrease for a given pressure. The plasma pressure is limited by the magnetic field strength. So even if fusion can be demonstrated scientifically, there are numerous engineering challenges.
     
  9. Mar 16, 2019 at 10:42 PM #8

    Astronuc

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    Staff Emeritus
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    The statement from Wikipedia is inaccurate. Rod containing lithium do no replace control rods. Rather lithium contain rods are place in assemblies that do not sit under control rods, or are rather in uncontrolled locations. They basically behave as burnable absorbers, which would have boron if they were used for reactivity control. Watts Bar uses Westinghouse fuel, in which some fuel rods have ZrB2 coating on the fuel pellets (so-called IFBA, for integral fuel burnable absorber), which has been used for a little over 3 decades now.

    Control rods do use silver-indium-cadmium (AIG) or boron in the form of B4C, but not Hf, since Hf can absorb hydrogen from the coolant (hydrogen diffuses through stainless steel) and swell. In PWRs, control rods sit out of the core, with the tips located in just above the plenum region. They are not used in the core during full power operation, although some PWRs (B&W types) have been designed to use axial power shaping rods, but those would have a moderate (grey) absorber, e.g., Inconel, instead of Hf or B. As far as I know, most if not all B&W plants stopped using APSRs.
     
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