The work proposed in this thesis deals with, application of fuzzy logic controller (FLC)to control nuclear reactors, pecifically for the first Egyptian Research Reactor (ET -RR 1) at Inshass. The problems that FLC solves in order to control the nuclear reactor are:• Power level control for either change of set point or reactivity perturbation of reactor.• Automatic power level setting due to loss of primary coolant flows (one pumpout of three).• The seasonal temperature changes affecting the average core temperature and initial start up positions of the control rods.The following topics are comprised to solve the above mentioned FLC problems:Initiation of dynamic equations describing the reactor kinetics with six-groups of delayed neutrons.Initiation of dynamic equations describing the reactor thermo hydrodynamics.Proposition FLC system including the object of regulation (fuzzification,inference machine with rule base, deffuzification) to solve the peviously mentioned problems.