Most of the concrete shielding walls and pipes around a reactor pressure vessel of a light water reactor become low level radioactive waste at decommission phase because they contain radioactive nuclide by thermal-neutron irradiation during its operation. The radioactivity of some low level radioactive wastes is close to the clearance level. It is very desirable in terms of life cycle cost reduction that the radioactivity of those low level radioactive wastes is decreased below clearance level. Recently, low activation concretes are partly used for some of the small proton accelerators to produce radiopharmaceutical. In case of light water reactors, however, methodology of low activation design of a nuclear plant has not been established yet because the reactor is a large-scale facility and has various structural materials. Database for low activation material production, tools of radioactivity estimation in a reactor and large-scale production technique of low activation structural materials such as cement and reinforced steel bars are required.