Argonne tests gravity-driven passive cooling for advanced nuclear reactors

Researchers at the US Department of Energy's Argonne National Laboratory evaluated the Reactor Cavity Cooling System, a passive setup that circulates water by buoyancy and gravity without pumps or electricity. Tests on the 59-foot NSTF facility mapped how decay heat and tank inlet height affect cooling stability.

• At 2.4 MW, steam reached the upper chimney 20 minutes after boiling began
• At 1.75 MW it took 90 minutes; at 1.4 MW steam never reached the chimney
• A mid-level tank inlet stabilized flow within 15 minutes, while a lower inlet caused constant surges
• The RCCS cools a reactor without pumps, electricity or human intervention