k-effective
Effective neutron multiplication factor (k), ratio of neutrons in one generation to previous.
k=1 defines criticality; calculated via codes like MCNP accounting for geometry, moderation, absorption. Used in reactor design, fuel cycle analysis, and waste criticality checks. Typical PWR operating k ~1.000-1.005.
Why it matters now
k-effective modeling essential for 2025-2026 SMR licensing and HALEU optimization, ensuring safe margins amid advanced fuel trials.