The primary system holds the core in a pool of liquid sodium at near atmospheric pressure. Pumps with no moving parts drive the sodium, heat exchangers hand the heat to a clean loop, and a second vessel catches any leak.
The reactor vessel is a stainless-steel tank that holds the core and the sodium pool. It operates near atmospheric pressure because sodium boils at 883 °C, far above operating temperature.
| Material | 316H stainless steel |
|---|---|
| Height | ≈ 5.5 m |
| Diameter | ≈ 2.4 m |
| Design pressure | Near atmospheric |
A second steel vessel surrounds the reactor vessel with a small gap. If the inner vessel leaks, the guard vessel catches the sodium and keeps the core covered.
| Gap | ≈ 150 mm, argon filled |
|---|---|
| Material | Stainless steel |
| Leak detection | Gap sensors and level probes |
| Function | Second barrier for sodium |
Liquid sodium fills the vessel and carries heat from the core to the heat exchangers. It conducts heat very well and stays liquid from 98 °C to 883 °C.
| Core inlet | ≈ 400 °C |
|---|---|
| Core outlet | ≈ 550 °C |
| Inventory | ≈ 20 tonnes |
| Cover gas | Argon at ~1 atm |
EM pumps drive sodium with magnetic fields instead of impellers. They have no moving parts, no seals, and nothing to wear out.
| Count | 2 |
|---|---|
| Type | Annular linear induction |
| Flow | ≈ 150 kg/s each |
| Backup | Natural circulation |
The IHX moves heat from the radioactive primary sodium to a clean intermediate loop. Thousands of thin tubes give the two fluids a large contact area without mixing.
| Count | 2 |
|---|---|
| Type | Shell-and-tube, counter-flow |
| Duty | ≈ 15 MWt each |
| Secondary fluid | Sodium or molten salt |
The head closes the vessel and carries every penetration. Rod drives, instrument lines, and pipe nozzles pass through it, and a rotating plug gives access for refueling.
| Deck thickness | ≈ 300 mm steel |
|---|---|
| Rotating plug | ≈ 1.8 m diameter |
| Penetrations | Rod drives, IHX nozzles, instruments |
| Shield plug | Borated steel and concrete below deck |