Control of quasistatic distributed parameter (d.p.) systems is considered in this paper. Singular perturbation techniques and calculus of variations are the main tools employed to achieve a control procedure consisting of two iterative schemes. The procedure is applied to control the xenon oscillations found in large thermal nuclear reactors. The linearized kinetic equations which depict the xenon phenomenon along with temperature effects are first identified to be a quasistatic diffusive system and then suitable manipulations are made on them to make- direct use of the two iterative schemes for obtaining the control.