High-Temperature Heat-Transfer Fluid Pump
Electromagnetic (EM) / Canned-Motor Molten-Salt Pump
Electromagnetic or canned-motor circulator pump moving the heat-transfer fluid (molten salt or liquid metal) through the HEX-tank-Stirling loop, with no shaft seals (zero-leak design) and rated for 300+ °C continuous service.
Purpose
Drive the circulating loop that connects the PCM tank to the Stirling converter and reactor charging path; the absence of rotating shaft seals eliminates a major failure mode in high-temperature service.
Context
Sits in the L3-ESS-THRM thermal loop, commanded by L3-ESS-THRM-CTRL. Receives DC power from L1-PDM. Coordinates speed/flow with charge/discharge rate requested by L2-ESS-MGMT.
Principles
- ▸Electromagnetic (EM) pumps use a traveling magnetic field to push electrically-conductive liquid (sodium, NaK, salt) — no moving parts in the fluid path
- ▸Canned-motor pumps enclose the rotor in the fluid; only stator windings outside — no shaft seal needed
- ▸Permanent-magnet brushless DC motors with sealed windings preferred for long life
- ▸Pump head and flow scale with motor speed; closed-loop control via flow meter feedback
- ▸Bearing options: hydrodynamic (fluid-lubricated, no wear), ceramic ball, or magnetic levitation
- ▸Catastrophic failure mode minimised by no-shaft-seal architecture
Typical implementations
- ▸AECL CANDU heavy-water primary pumps (canned motor heritage)
- ▸Sodium-cooled fast reactor EM pumps (Russian BN-600, BN-800)
- ▸CSP molten-salt pumps (Andasol-1 — vertical cantilever style)
- ▸NASA Glenn high-temperature liquid-metal pump testbeds
- ▸Sunpower / Infinia Stirling working-fluid circulators
Lunar considerations
- ▸1/6 g may affect NPSH (net positive suction head) for centrifugal designs — EM pumps unaffected
- ▸Long mission requires bearing wear minimization — hydrodynamic bearings preferred over ball bearings
- ▸Salt freezing in the loop is a serious failure mode — trace heating mandatory on standby
- ▸Pump motor thermal isolation from hot fluid maintained via canned construction; cold-soak protected by trace heaters
- ▸Radiation-tolerant brushless DC controllers required
- ▸Maintenance access via L1-MNT quick-disconnect with isolation valves
Specifications
Functional
| primary function | Circulate heat-transfer fluid through thermal storage loop |
| inputs | DC power from L1-PDM, Speed setpoint from L3-ESS-THRM-CTRL |
| outputs | Fluid flow at rated head and temperature, Pump telemetry: speed, flow, temperature, motor current |
| rated flow lpm | 200 |
| rated head m | 15 |
| operating temperature c | 50, 350 |
| fluid type | Molten salt (NaNO3/KNO3) or liquid metal (NaK) |
| pump type | Canned-motor or EM pump |
| motor efficiency percent | 80 |
| lifetime years | 15 |
| design starts min | 5000 |
Physical
| mass kg | 25 |
| dimensions | 400 × 250 × 300 mm |
| materials | 316L SS pump body and impeller (for salt service), Inconel 800H high-temperature variant, Permanent-magnet brushless DC motor (samarium-cobalt magnets — high-T stable), Hydrodynamic bearings with self-lubricating fluid, Stainless steel can / inner sleeve, Ceramic thermal isolators between motor and fluid |
| operating temperature c | 50, 350 |
| ambient temperature c | -40, 50 |
Operational
| power consumption w continuous | 500 |
| power consumption w peak | 1000 |
| thermal range c | -40, 350 |
| lifetime years | 15 |
| mtbf hours | 80000 |
Interfaces
Provides
- Heat-transfer fluid circulation
- Pump telemetry
Requires
- DC power ~500 W continuous
- Speed/flow setpoints
- Motor cooling (~50 W)
Cite this entry
Lunar Ark Codex. "High-Temperature Heat-Transfer Fluid Pump" (L3-ESS-THRM-PUMP). Retrieved 10 September 2026, from https://lunarark.com/entry/L3-ESS-THRM-PUMP
Licensed CC-BY-SA 4.0. You may reuse and adapt this entry with attribution, under the same licence.