[LarsJorgensen]

The high temperature limits the materials we can choose from. We've elected to stick with known materials (stainless steel) for the first generation to keep our schedule short. As someone noted below highly corrosive depends on the material you are in. The fuel salt is actually pretty modestly corrosive as long as the chemistry is kept right. Specifically, we have to keep the fuel salt reducing - we don't want any free fluorine running around. We keep a balance between UF3 and UF4 (roughly 99% UF4). It's like keeping the chemical balance in your swimming pool. Under those conditions the vessel will last a very long time indeed (>60 years). But it takes a long time to prove this and we have to swap out the graphite anyway so we swap out all critical components every four years. They get disassembled, cleaned, and normally put back into service with a new graphite load. This is kindof like your laser printer cartridge.

[jmcmahon443]

Stainless steel. Could you go into more depth about who's making your pipes and fittings? What surface treatments will you be using, etc? Will you be putting a cooling jacket, insulation, or anything over the pipes? Very interesting in the metallurgy you're using since it appears to be the BIGGEST problem of the MSRE at Oakridge.

Also, what happened to that experimental reactor? Didn't Obama send it to Norway or something?

[LarsJorgensen]

The challenge with metallurgy for MSRE was two fold. First was the neutron interaction with nickle forming helium that migrated to the grain boundaries. We avoid this problem altogether by having a single fluid design with a protective shield of B4C absorbing neutrons before they hit the wall.

The second problem was with tellerium penetrating the Hastalloy and weakening it at the grain boundaries. This isn't a problem with stainless steel.

The stainless steel planned is SS316 which is available from multiple sources.

The primary loop does not have insulation surrounding it but it does have a 1m thick graphite reflector to bounce most of the neutrons back to the core then a layer of B4C to absorb the rest before they get to the vessel.

The MSRE was shutdown decades ago and recently had its fuel salt removed. The vessel and piping are still in Oak Ridge inside its concrete silo.

[jmcmahon443]

Great, grain boundaries are really what it gets down to.

I only have two things to say: 1.) Good luck testing and gathering data on these ideas. You'll need it. 2.) Are you hiring mechanical engineers?

[woah]

What happens when something goes very wrong and corrosion happens? Does the fuel leak into groundwater?

[LarsJorgensen]

The primary loop (that contains all the fuel salt and fission products) is inside a can so if we get a leak in the primary loop the salt will be contained inside the can. The can drains to the fuel dump tank (FDT). Both the can and FDT get passively cooled by the membrane and all entrance pipes come in from above so there is no weakness at the bottom.

These in turn are inside a silo, which is inside the silo hall. All total there are four barriers to break through before we get radioactive release.

Further, the fission products are combined with fluoride upon forming (when you fission UF4 the uranium is split into two fission products and the F4 is available for recombining with the fission products). Most of the fission products like to stay in the salt so even if the salt gets spilled the fission products won't wander farther than the salt spill.

[ginko]

And what will happen to the solidified salt spill? Could it be safely cleaned up or would it be too radioactive to approach?

[LarsJorgensen]

It will be rather intensely radioactive. A person cannot approach it. A cleanup like this would have be done robotically. If the spill is contained in the can then the whole can is designed to be sealed and shipped back to the can recycling center where there are facilities for cleaning up the can. The main point though is that the spill is contained within the building and does not spread to the environment. A worst case accident becomes an economic loss of the reactor rather than a mass evacuation.