This course is designed to introduce fundamental reactor analysis related with neutron reaction, nuclear fission and chain reaction system. Major subjects are: neutron slowing down in infinite medium, neutron diffusion theory, approximation of few neutron energy group and criticality calculation, hetrogeneous reactor, dynamics and reactivity feedback effects, and projects running computer code systems of reactor analysis (neutron moderation, two-group neutron diffusion equation, depletion calculation, dynamics, etc).