I know I said last question, but I want to be be clear about this.
“highly radioactive light elements”
Half-life for these?
Sorry, I never was a nuclear physicist, been out of school for decades.
Half-life for these?
There are many of them. Probably hundreds to thousands. They all have different half-lives. I can't possibly name them all here. Some are particularly bad actors.
Longer explanation.
When anything fissions (U-235, U-233, Pu-239) it produces "fission fragments" plus a few neutrons. The neutrons are what make the fission reaction self-sustaining, the fission fragments are the "highly radioactive light elements", or more properly, the nuclei of these elements. Many of these lighter elements are produced, and each fission reaction has its own distribution of relative quantities.
When I say some are "bad actors" what I mean is that they are more biologically active than others. Anything that has a long enough half-life so that it is likely to be absorbed by a human or animal before most of it decays is biologically active. If the half-life is short enough so that a large fraction of it will decay during the lifetime of that human or animal it is going to have bad consequences. You want to minimize the amount of radioactive decay inside your body.
This is the most difficult to handle part of what is called "nuclear waste". The absolute quantity per unit energy produced of this material is very similar from any fission reactor. Now the particular mix produced in the Thorium cycle may be easier to handle than average, but that certainly doesn't mean it is "easy" or that there isn't any.
To use an analogy, would you rather have a lion, a tiger, or a cougar suddenly appear in your living room? None of these would be considered "good" but the cougar would be "less bad" than the lion or tiger.