I recently stumbled across an internet discussion of the idea of transforming thorium 232 into uranium 233 in a reactor. The term breeding was used, and this lead to confusion. Someone mentioned plutonium. There is a natural linguistic association between the term "breeder reactor" and the word "plutonium".
The word "breeder" is "breeder reactor" is used metaphorically. What happens inside reactors is arguably nothing at all like the biological process of reproducing. Nothing new is produced in the nuclear transformation process, but something is changed. So not only are the words "breeding" and "breeder" problematic from the standpoint of associations, they represent a weak metaphor.
A breeder is someone who selects animals for desirable characteristics to reproduce in offspring, and who controls the reproductive process. But what happens inside reactors is that certain physical processes occur, that lead to the transformation of isotopes of one element into isotopes of another element. Is there an appropriate name for the transformation process? The word alchemy comes to mind. The goal of alchemy was the transformation of elements as understood by the alchemist. Such a transformation takes place inside a reactor. Thus the term nuclear alchemy would seem appropriate for the nuclear processes that transforms one element into another. In fact it is quite possible to turn lead to gold inside a reactor.
Thus the word "alchemy" captures something about the nuclear process that the term breeding misses, but the word is awkward to use in some expressions. Nuclear alchemy takes place in all reactors. Describing a reactor designed to produce more new fuel than it burns as an alchemy reactor thus is to say the least confusing.
Since we are talking about a process that transforms one element into another we could I suppose call the reactor a transformer. But everyone knows that transformers are toys that change from one thing into another. How about a changer? I don't think so. That leaves with converter.
Former Presidential science advisor, John (Jack) H. Gibbons uses the term converter to describe a reactor that produces hydrogen, but the term converter could also be used for a reactor that transforms thorium 232 into uranium 233. Although the term converter is not without problems, it seems to work better than anything else I have considered. Of course conversion suggests something religious happens, but we should not speak of conversion, rather we should speak of something magical that happens inside a reactor. I would say magical in the way the greatest of all alchemists, Francis Bacon used the term, as in "practical magic," that is science.
The reactor enables us to achieve the goal of the ancient science of alchemy, that is the conversion of atoms of an otherwise useless material, into atoms of a material that is of value.
Thus the term converter reactor would seem the best to use for a reactor which transforms Thorium into nuclear fuel. Nuclear alchemy is the name of the process, and is the name of any process by which elements are transformed as a consequence of controlled nuclear fission.