⚠ HOW THIS WORKS & ITS LIMITS: You set a target power; the tool checks whether the core can (1) reach criticality with control margin, (2) be shut down, (3) remove that heat via ṁcₚΔT, and (4) keep fuel/clad/structure below temperature limits. Neutronics use a calibrated four-factor + diffusion-leakage proxy with separate operating and shutdown k_eff — useful for trends and slider intuition, not a substitute for Monte-Carlo transport (OpenMC/MCNP) or thermal-hydraulics codes (RELAP/TRACE). Fuel-temperature and heat-flux figures are coolant-side first-order estimates. Treat all numbers as order-of-magnitude.