Given the complete lack of shielding that we get from the magnetosphere and atmosphere I am guessing that a few kg of scattered enriched uranium is going to be

Given the complete lack of shielding that we get from the magnetosphere and atmosphere I am guessing that a few kg of scattered enriched uranium is going to be background noise on the moon. The target is small, the moon is (relatively) big and we can bury the reactor; a meteor strike on the reactor is probably less of a concern than a similar strike on any habitat to which the reactor it meant to provide power. A recent Chinese probe has shown that lunar regolith is radioactive just from cosmic ray bombardment, so as a general rule I am guessing that future lunar operations will treat the entire lunar environment the same way we treat places like Chernobyl. Shield everything, watch your dosage and exposure, and do everything possible to prevent inhalation/ingestion of particles from the external environment.