A material capsule system has been developed for irradiation tests of nuclear materials in the core region of the high-flux advanced neutron application reactor (HANARO) and has been actively utilized for the various material irradiation tests requested by numerous users. For an irradiation test in the reactor, nuclear characteristics and irradiation temperature of the capsule parts are essential for the safety analysis of the capsule and for the detailed capsule design. The irradiation temperature and neutron fluence of the specimens are key parameters required by a user to analyze any neutron irradiation damage effects. Based on a basic design of a capsule, the reactivity effect, neutron flux/fluence, and gamma heating of specimens are calculated by the MCNP code. To compare the calculated neutron fluence of the specimens, thermal and fast fluence monitors (F/Ms) are installed in a capsule. After an irradiation, the F/Ms are dismantled and analyzed to obtain a neutron spectrum. The experimental fast neutron fluences (E > 1.0 MeV) derived by using the SAND II code were found to lie within about 20% of the predicted values calculated by the MCNP code. The irradiation temperature of the specimens is analyzed preliminary by using the GENGTC or ANSYS codes based on the basic design of a capsule and gamma heating. During an irradiation test, the temperatures of the specimens in a capsule are measured and monitored by thermocouples. The displacement per atom (DPA) and activation of the irradiated specimens are also evaluated by using the SPECTER and ORIGEN2 codes, respectively, at HANARO.