Water in Magnet Cryogenics
Superconducting magnets need refrigeration, and the cryoplant's heat rejection is a real but modest and closed-loop water term.
Both machines rely on high-field superconducting magnets — 16.84 T peak in the breeder (Hyperion), 26.49 T plug and 17 T throat in the burner (Aegis / MetroVolt). Superconductors must be held at cryogenic temperature, which means a refrigeration plant that consumes power and rejects heat. That heat rejection is a genuine cooling duty and belongs in an honest water account.
Scale and character
Cryoplant heat rejection is modest compared to a steam condenser and is naturally handled by closed loops or air cooling. The cryogen inventory itself is largely helium in a sealed circuit, not water. So the water term is limited to the warm-side heat exchanger, which can be dry-cooled.
Why it is worth stating
Naming the cryoplant load prevents the false impression that superconducting magnets are thermally free. They are not: refrigeration costs power and rejects heat. But because the reject duty is modest and closed-loop, it does not reintroduce the river-scale water demand that direct conversion removed. This is the pattern throughout the water case — small, honestly named residual loads that do not overturn the architecture-level claim.
- Cryogen is sealed helium, not consumed water.
- Warm-side rejection can be dry-cooled.
- Parasitic refrigeration power is an efficiency term, not a water term.
It is also worth noting that cryoplant heat rejection is steady and predictable, unlike a condenser duty that swings with load and ambient conditions. A steady, modest load is exactly what a compact air-cooled exchanger handles best, which is why the cryogenic system does not reintroduce a water dependence even though it is a continuous heat source.
The parasitic refrigeration power is the honest cost here: holding coils at cryogenic temperature consumes electricity, an efficiency term that both machines carry. It is not a water term, and we keep the two ledgers separate rather than conflating power and water.