[en] Studies on the target irradiation for fission Mo production at HANARO have been steadily progressed. Low enriched uranium foil, which is the most promising LEU target for fission Mo production and is now under development here, is adopted as a target. Physics concerns are reviewed in some detail with an assumption that the LEU foil target is being irradiated at the OR irradiation hole in HANARO. The LEU foil target geometry is decided considering the OR hole size and the domestic demand for Mo-99 activity. It is an annulus type and its thickness is 100μm. Reactivity change due to target loading is examined to confirm the reactor safety. It is estimated to be less than 0.8mk with a standard deviation of 0.24mk. Even the irradiation of the two targets gives only 1.6mk of a reactivity change including an uncertainty. This is much lower than the safety limit of an experiment. The target will be loaded and unloaded during the reactor operation. Considering the small reactivity effect of the target, the irradiation activities of the target will not cause severe reactivity induced accidents. The thermal neutron fluxes at the vertical irradiation holes and horizontal beam tubes in the reflector should not be perturbed much due to the target irradiation. Most of the fluxes are maintained within a 2% fluctuation. The calculated powers at one target are in the range of 30∼36kW. This power can produce a specific activity of 45∼54 Ci Mo-99/gU at the end of irradiation. (author)