A new materials irradiation facility with improved control capabilities has been installed at the Kyoto University Reactor (KUR). Several deficiencies of conventional fission neutron material irradiation systems have been corrected. The specimen temperature is controlled both by an electric heater and by the helium pressure in the irradiation tube without exposure to neutrons at temperatures different from the design test conditions. The neutron spectrum is varied by the irradiation position. Irradiation dose is changed by pulling the irradiation capsule up and down during irradiation. Several characteristics of the irradiation field were measured. The typical irradiation intensity is 9.4 x 10(12) n/cm(2) s ( > 0.1 MeV) and the irradiation temperature of specimens is controllable from 363 to 773 K with a precision of +/- 2K. (C) 2003 Elsevier Science B.V. All rights reserved.