purplemonday
commented
6 years ago i think your refering to actualy inworld liquid, much like cryotium the problem with it is that helium cools by evaporation, so you would constandly need to add more. then the presence of noble gasses like helium in a reactor is not realy smart. in short. helium ocurs in nuclear decay its one of the reasons reactors cant be run for long at max power.. the gasses decay to krypton witch basicly go into the rods and saturate them so they wont fision heat and radiation will speed things up. reallife reactors that get worked hard will eventualy endup with krypton poisening and need to be powered down for the krypton to decay into rubdium to get below a level that things will chain again. or replace there fuel.
you dont want to introduce any noble gasses as they will eventually interact with the uranium after they decayed (a few times)
so id say the idea of helium in a fission reactor is a tad fubar, other non-noble gasses might do the trick. but i think the future lays in more dense metal like fluids.
fusion & helium (3) however.. thats a difrent story. tho for fission its poisen
Add 'liquidhelium' to the list of fluids that can be used in the reactor - it is, naturally, incredibly cold, so absorbs heat well, but does not moderate radiation as well. It is the ideal coolant (IRL), if ever there was one.