Answer ao The intent of this categorization is not clear. os For example, tn the activities of nuclear reactors, large numbers of curies of radionuclides are generated but few curies are released. In underground nuclear tests, ‘large numbers of curies of radionuclides are generated and remain buried . forever. Fuel reprocessing operations generate none and release few, but store almost all of those generated by the reactors. Finally radionuclides used in medical and industrial operations are generated in a nuclear reactor and a certain small quantity is released to the environment. The reference to "natural radionuclides liberated in fuel mining" is | subject to several interpretations. It may refer either to underground uranium mining operations releasing radon and its daughters te the mining environment; or to the radioactive tailing residues from such mining 7 operations; or to the natural radionuclides liberated in burningfossil fuels such as coal. If this refers to release of radon and its daughters in underground mining operations AEC is a purchaser of uranium oxide but does not have regulatory control over mining operations. Radon-222 and its daughters are released into the mine atmosphere dur ing these operations. and the unit concentration must be controlled through ventillation to protect uranium miners. Federal regulations require maintenance of records of the concentration of radon and its daughters in the underground work spaces. In the event of increased concentration above a stated level of radon and its daughters work will cease in the area until restoration to safe radiation levels for the miners to work. problem. Radon in mines is primarily an occupational If this refers to radioactive tailing residue from such operations,