Did you mean "RISC-V" + "core" + "prison" ? Or something like "rCore" (an educational OS kernel for RISC-V, used in the清华 rCore OS course) plus a "prison" concept (e.g., FreeBSD jails / Linux containers)? There's no known project called "rcore prison".
: Officers can quickly punish rule-breakers by sending them to solitary, which resets any active escape progress and clears the player's inventory [1, 6]. rcore prison docs