It made a lot of sense. Sodium is an amazing coolant. It was also a relatively easy to implement design for a breeder reactor, with all the related advantages (much better way of using uranium fuel with no enrichment step, burning of plutonium and high-activity "waste", etc).

> I would like to know how cooling intensive it was compare to PWR. And what operating temperature.

Cooling should be overall similar to a PWR operating at the same power. The temperature in the core is higher than in PWRs (around 500 to 600°C instead of 300°C), but they have 3 cooling loops instead of 2. I can't remember the temperature in the most external loops off the top of my head but I don't expect them to be very different in both designs. They use similar steam turbines, so they should have similar operating regimes, but I could be wrong.

> Also, some of the Sodium reactor technology and materials is now used by companies like Moltex Energy.

Yes, the materials are quite different from PWRs because of the different neutron fluxes and spectra, but some of this knowledge can be applied to other fast reactor designs like the fast MSRs. Some of the corrosion mechanisms (which are a large hurdle to clear for MSRs still) also have some similarities.

> Molten Salt reactors are the likely future in my opinion, but not sure yet what form.

That is where the wind is blowing. It's difficult to say more at the moment, because there are very different designs (fast or thermal, uranium, thorium, or MOX, large or small and modular, etc), but there is a lot of activity around MSRs.