SMR
Some folks here looked into these.
Believe that the idea of using a two-fluid MSR is also being floated.
The mechanism with these is using a liquid fluoride salt in a conventional reactor pin, with any gases evolved being vented under controlled
conditions. The outer salt which is the primary coolant is less harmful as it has no nuclear fuel within.
A somewhat more radical variant uses a modified liquid metal reactor with the fuel suspended within the liquid as tiny capsules
so that criticality only takes place within the highly optimized core that also has control and neutron reflective elements included.
Hybrid design that relies on very thin layers of moving metal driven by gravity, so if anything goes wrong they simply cut off or divert
the fuel flow around the core and it shuts off. Fully throttled and far safer due to minimum inventory of potentially dangerous actinides.
It could feasibly be adapted for space use as parts can be sent up by rocket, with far lower risk than sending up a conventional
fully stocked core if the empty re-entry proof Ir fuel capsules are reused between launches (hey there SpaceX)