Sub reactors can dump excess heat into the water. Radiating heat off in space is presumably much more difficult and inefficient . Also not clear if the working

Sub reactors can dump excess heat into the water. Radiating heat off in space is presumably much more difficult and inefficient . Also not clear if the working fluid is included in that 100t number. It has to be fully closed system in space. Solar has additional advantages in cost, redundancy and simplicity of maintenance. That should but be discounted either