The IHX itself, constructed of austenitic stainless steel, consists of an upper and lower tube sheet separated by straight tubes with a central downcomer for incoming intermediate sodium and a riser for outgoing intermediate sodium.
Primary sodium from the hot upper reactor pool, which enters the IHX at 485[Degrees]C (905[Degrees]F) and is cooled to 338[Degrees]C (640[Degrees]F) by the time it leaves, flows into a reactor lower plenum.
The IHX is structurally designed on a faulted basis to withstand the full 7.0-MPa (1000-psig) steam pressure that could reach the IHX during a sodium/water-reaction event in the steam generator.