Neutron Moderation Simulator

Fission releases neutrons at roughly 2 MeV — far too energetic to reliably trigger the next fission in a thermal reactor, where the fission cross-section is largest near 0.025 eV. A moderator slows them down through repeated elastic collisions with light nuclei. This simulator fires neutrons into a 3D lattice of moderator nuclei and applies the real two-body elastic-scattering energy formula at every collision, so switching between hydrogen, deuterium, carbon and lead visibly changes how many bounces it takes to reach thermal energy — matching the textbook logarithmic-energy-decrement formula ξ and the collision-count formula N = ln(E₀/E_th)/ξ shown live in the readout.