Moltex Energy agrees with you on pumping fuel salt. They keep their liquid fuel in a fuel rod, open at the top, no pumping. All the rods are immersed in a pool of liquid salt coolant, which just sits there. Secondary coolant in pipes through through that.
(I didn't answer your previous points about the NRC process, but for the record, I completely agree with you.)
> Moltex Energy agrees with you on pumping fuel salt. They keep their liquid fuel in a fuel rod, open at the top, no pumping. All the rods are immersed in a pool of liquid salt coolant, which just sits there. Secondary coolant in pipes through through that.
Yes, Moltex is an interesting design. The main drawback, AFAICS, is that since the fuel concentration in the fuel salt is quite low compared to solid fuel designs, they have to use pretty enriched fuel. I think their current plans call for 40% Pu. And the breeding ratio is poor, around 0.5 according to a paper I skimmed through a while ago.
Yes, they also have the thermal design which I'm quite sure requires much lower enrichment, but AFAICT is more a concept than something they're actively developing. It makes sense of course to focus on one design at a time, unless they have infinite money.
One of the other fast spectrum MSR startups, Elysium, also proposes using spent fuel + maybe leftover military Pu for startup. The interesting thing about Elysium is that their design at least breeds, so they only need enriched fuel for starting up. They're saying that they can run up to 40 years before needing to reprocess the fuel, just by adding U238 online to the salt.
I don't know. MSR's are certainly interesting, but they have downsides as well as upsides.
Some of the PWR SMR's like NuScale also sport passive safety features, which should make it simpler and safer. Being a PWR, it's still a high pressure design, of course, which MSR's avoid.
While MSR are very cool, in some ways they're pretty scary too. I mean, you're pumping around tonnes of super-radioactive goop. What if you have a leak? At least with a traditional design you have a couple of extra protective layers, with fuel being contained in solid pellets contained in tubes. And you have to be very careful with the chemistry of the fuel salt; IIRC one of the early MSR's (ARE?) had to be shutdown since they messed up their redox chemistry which lead to fissiles plating out on the heat exchangers. Eek!
There's the famous Rickover quote that anybody can design a paper reactor, but real reactors tend to be complicated, over budget, and over schedule.