Our waterways are becoming more and more polluted due to PFAS, plastics, medicines, drugs, and new chemicals made by companies that just hand over the responsibility of cleaning to plants paid for by public moneys. Detecting the different chemicals and filtering them out if getting harder and harder. Could the simple solution of heating up past a point where even PFAS/forever chemicals decomposes (400C for PFAS, 500C to be more sure about other stuff) be alright?
Ok so i think the disconnect here is that you are visualizing the water literally passing into the reactor and out the otherside.
In reality the water would pass around the outside of the shielding, where it is still plenty hot, but the radiation from the reactor isnt passing through.
This is more or less how a nuclear power plant operates today. We sont get the power directly from the reaction, we get it by using the heat fenerated to boil water to operate steam turbines. In fact, they are just steam engines with the coal replaced with nuclear fission.