Reactor Point Kinetics & Reactivity Insertion

This simulator solves the one-group point-kinetics equations exactly — not by numerical integration but by diagonalising the linear neutron-population/precursor system analytically every time reactivity changes — so it stays stable no matter how small the prompt generation time Λ is set. Insert a step reactivity change in dollars (units of β, the delayed-neutron fraction) and watch the reactor core's glow track the resulting power trajectory: the fast "prompt jump" that follows any reactivity step, the slower exponential rise or fall set by delayed-neutron precursors, and — if you push past prompt critical (ρ ≥ β) — the millisecond-scale runaway that real reactors are engineered to keep impossible. A control-rod bank animates in and out with the reactivity you dial in, and an automatic trip scrams the reactor if power exceeds 100× nominal.