NO radioactive waste, detailed calculations

Focus Fusion – fusion running on aneutronic fuels within a dense plasma focus (DPF) device, is safe and environmentally sound. No neutrons are produced in the main reaction.  No neutrons produced means no nuclear waste is produced either.  Secondary reactions between helium and boron nuclei do produce a few neutrons—1/500th of the total energy—but these neutrons are too low-energy to produce radioactive waste within the machine structure. An electrode that had been in the machine for a month would have no radioactivity above background level. A short-lived radioactive isotope, carbon-11, is produced by another secondary reaction, but it decays so swiftly , dropping by 50% every 20 minutes, that 9 hours after a fusion generator is turned off, it could be safely opened and serviced by someone with no protective gear. Again no radioactivity above background level would exist. And of course, there are no greenhouse gases, with the only by-product being useful helium gas.

Radioactive waste means material with radioactivity at a level that is dangerous to organisms. Everything contain some radioactivity, even us. But Focus Fusion generators produce no radioactive waste.

Here is a small, rough, calculation about the amount of radioactivity produced in the beryllium electrodes during the month they are in a Focus Fusion generator.

Rate of aneutronic reactions:
7×1018/s

Secondary neutrons per aneutronic reaction (our calculation—some other estimates are as low as 1/1000)
1/200

Proportion of neutrons absorbed by Be9 electrode to produce Be10 (cross section 0.1 mbarns; average depth of Be 1cm)
1/75,000

Rate of Production of Be10 nuclei
4.7×1011/s

Total Be10 nuclei produce in 1 month
1.2×1018

Rate of decay of this many Be10 nuclei (Be10 half life 1.4My)
2.9×104 decay/s

Equals 0.8 microcuries of radioactivity in each used set of electrodes.

Radioactivity of human child—about 0.2 microcuries

Radioactivity of classroom of 25 children—5 microcuries

This is why we won’t need to worry about the radioactivity of the Be electrodes before they are recycled.

Let’s just look at the tritium numbers.

3.5 billion neutrons for each J of fusion produced.

9 million Li6 nuclei from reactions with Be9 in the electrodes. (cross section 20 mbarns)

In a month in a 5MW generator, about 350 of those Li6 nuclei will be hit by neutrons and react to produce tritium nuclei. (cross section 250 mbarns)

So we have 350 tritium nuclei per J of fusion energy with focus fusion versus, for example, 430 billion tritium nuclei per J of fusion energy with a tokamak.

The tritium will mostly end up in the helium exhaust or helium cooling fluid of the Focus Fusion generator. Total tritium production in a month: 44 nanograms or 630 microcuries. The safety limit for tritium in drinking water in the U.S. is 20 nanocuries per liter of water. So just diluting the tritum (and the helium it is with) in 1,000 gallons a day of water would make it safe. That’s the water usage of 3 typical U.S. families. Less than 1 microcurie will still be left in the Be electrodes. So this is why we don’t worry about tritium.

Bottom line—NO radioactive waste.

The reactions are on page 6 of  (this link will download a PDF document to your computer) “Beryllium – A Unique Material In Nuclear
Applications.”
You can use this website https://www-nds.iaea.org/exfor/exfor.htm to check cross sections. DOE Safety guidelines

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