RBMK Positive Scram Effect: 2D Core Reactivity Map

This is a 2D-native counterpart to the 3D RBMK "positive scram effect" model: a top-down grid of 36 fuel-channel cells is colour-mapped live from blue (water) through amber (graphite front) to dark grey (absorber front) as each rod's insertion fraction advances, a strip chart tracks total core reactivity against time since AZ-5 was pressed, and a phase-portrait panel plots reactivity against insertion fraction to reveal the characteristic positive-then-negative loop directly in state space. Hover any channel cell for its individual front positions and reactivity contribution. Adjust rod drive speed, graphite displacer length, and how many rods are actually available to the scram — including an "1986 scenario" preset — to see how the loop's shape and peak change.