Reactor Decay Heat After Shutdown

A reactor SCRAM stops the fission chain reaction instantly, but the fuel keeps producing heat — from the radioactive decay of fission products built up while the reactor was running. This simulator renders a 3D fuel-rod core whose colour tracks real-time temperature, driven by the Way–Wigner decay-heat curve fighting against a coolant-flow control you set yourself. Push flow too low after SCRAM and the core heats toward the cladding-damage threshold, the same mechanism behind a loss-of-coolant meltdown; keep flow high and decay heat bleeds away safely over hours. Three controls — pre-shutdown operating time, rated thermal power, and post-SCRAM coolant flow — plus live readouts for decay heat, core temperature, elapsed time and risk status turn a textbook formula into something you can break.