> So, in a conventional reactor, you use nuclear fission to heat/pressurize water and then use your hot, slightly radioactive steam turn a turbine.
I was under the impression that there was a heat exchanger in the path - that is the reactor turns water into slightly radioacive steam, which is sent through a heat exchanger to turn different water into non (or way less anyway)- radioactive steam for the turbines. So both are indirect.
(This is just a nit comment, I think your main points about efficiency still hold, and your materials questions are good!)
There are two kinds of conventional light water reactor. In the pressurized water reactor (PWR), the most common, there is indeed an additional heat exchanger between the water in the core and the water that turns to steam. In the boiling water reactor (BWR), the second most common, the slightly radioactive steam from the core goes directly to a turbine.
Also, AFAIK, those high-temperature reactors are normally made with a molten metal intermediate cycle (normally sodium) and a gas-only external cycle (normally CO2).
Water enters only to cools the cold side of the external cycle.
I think I was confused by news stories about situations where the reactor has failed in some way, and then there are stories of how radioactive water needs to be stored / disposed of somehow.
In those historical cases, the priority was cooling the core, the easiest method (especially if a substantial amount of plumbing is wrecked or questionable) is dumping water into it.
Which then becomes irradiated, and pools via gravity in any lower voids, and then eventually needs to be dealt with.
I was under the impression that there was a heat exchanger in the path - that is the reactor turns water into slightly radioacive steam, which is sent through a heat exchanger to turn different water into non (or way less anyway)- radioactive steam for the turbines. So both are indirect.
(This is just a nit comment, I think your main points about efficiency still hold, and your materials questions are good!)