[bulltale]

In addition, in the step before where the heat is transferred away from the reactor walls to the turbines, a heat flux is needed of 100MJ/s. Assuming a contact surface of 100m2, that is 1MJ/s per m2. That sounds like a huge flux and I am not sure if there is any medium that could do this.

Or are my assumptions way off?

[wcoenen]

I think I was editing my comment to add an estimate of the heat flux while you wrote this, and we arrived at the same number.