Lojban should already contain semantic primes in its gismu space. Example, "ckaji" ("kai"); we have the abstractor "ka".
I had to look up "semantic prime". In linguistics, it seems to refer to a "core" meaning that isn't further analyzed, analogous to a prime number that can't be further factored. It's associated with theories that all meanings are built up out of some small set of semantic primes. It looks like the term is due to Anna Wierzbicka. Sounds related to the Gismu Deep Structure hypothesis. mi'e jezrax
la nitcion. puzu cusku di'e
It remains to be seen to what extent Lojban can find, let alone enforce, a native semantic map, founded on its morphological primitives.
fo zoivy. http://www.lojban.org/files/papers/nsn_semantics_paper .vy