[en] A technique is presented for optimizing a cyclic regime of the IRT-2000 pool type reactor with the account of xenon poisoning under conditions of limited reactivity. The technique is based on the maximum principle. The experimental part of the investigation consists in measuring reactivity of the reactor operated on a dayly cycle with overnight outages. The results have shown, that the point reactor model accounting for spatial effects can be used to describe xenon transients in the IRT-2OO0 type reactors. The experiments have proved the validity of the calculations. The technique developed reduces the duration of forced outages due to xenon overpoisoning more than twice and is applicable not only to the IRT type reactors but to other reactors operating in a cyclic regime as well