Lapin Dormant said:
Probably my error, as I did NOT read the paper, but in the manufacture of tritium, isn't that done by nuclear bombardment using radioactive isotopes?
Hence a 'use' for some of the waste?
To the best of my knowledge, the easiest way to produce Tritium is to put some Li-6 inside of a reactor. The high-neutron flux in the reactor will produce Tritium using the reaction: Li-6 + n -> He4 + H-3. In spent fuel rods, there will be some residual neutron flux, but it's going to be considerably less than what you'd get inside of a reactor.
In an operating nuclear reactor, only about 0.7% of the neutron flux come from sources other than the fissions (we call these delayed neutrons and they're actually critical to our ability to control fission reactors.) Most of these delayed neutron sources have quite short half-lives though, typically less than 1 minute, so in spent fuel the neutron flux would fall off significantly after only a short period of time.
This isn't to say there aren't uses for nuclear waste though. We could pull about 99% of the material from spent fuel rods (the Uranium and Plutonium) plus a few other select isotopes which are useful for medical or commercial purposes (radioisotopic tracing and food irradiation for example.) Unfortunately, in order to do that we'd have to reprocess the waste and our current policy in the U.S. is that we don't recycle our fuel.
Back to the initial article, I noticed one item that I missed on my first initial skim. It completely ignores the problems associated with storing tritium-deuterium gas in a warhead. First, by it's very nature tritium is difficult to store as a pure gas. It tends to escape through the walls of most common storage materials (glass, steel) over a period of time. It's also radioactive, with a half-life of 12.3 years. The result is that after a period of time, your weapon will have considerably less yield than it did when it was first produced, giving it a fairly short shelf-life.
In the earliest thermonuclear weapons, they had to periodically disassemble the warhead, remove the pit, and refill it with tritium. This was less than desirable, so a solution was devised to use Li-D, which is stable, in the pit instead of D-T. When the first-stage (fission) trigger was ignited, it would provide the neutron flux to produce tritium from the Li to be used in the reaction. In the case of a conventional trigger, like the FGNW's, you wouldn't have the neutron flux so you'd have to use D-T gas in the pit. Has our technology improved enough that this is no longer a significant obstacle?
No, actually that should be plastic, not glass.
