Clearance levels for solid materials. Review for the clearance levels derived by international organizations and the Nuclear Safety Commission

There are concepts of exclusion, exemption and clearance in the regulation of radiation protection. Radioactive materials with negligible human risk are subjected to the ''clearance'' and clearance materials are to be disposed and/or capable of being re-utilized which, are, e.g., formed by decommissioning of a nuclear facility. This review described clearance levels of radioactivity for solid materials investigated by IAEA (TECDOC-855 and -1000), EC, OECD/NEA and the Nuclear Safety Commission in Japan. The latter's report (March, 1999) included the sort of the object to be assessed, measure of dose, assessment pathway, calculation model and parameters, results of calculation for clearance level which showed some difference from TECDOC-855 in 55Fe, 3H, 14C, 129I, 36Cl and 99Tc, and listing of the important radionuclides (3H, 54Mn, 60Co, 90Sr, 134Cs, 137Cs, 152Eu, 154Eu and all α-emitters). Technology is now necessary for measuring clearance materials rapidly and precisely and for re-utilizing the materials. (K.H.)