Actually, the only environmental threat from warm water effluents of nuclear power plants is warm water. No radioactive material is released from a nuclear power plant during normal operation (not to minimize the occasional accidents that have occurred, sometimes with release of radiation). The cooling water doesn not come into contact with radioactive material at any time. Also, no chemicals are added to the cooling water that passes through the plant. The water coming out of such a plant is essentially as clean as the water that went in. The one thing that is added to the cooling water is heat, and quite a lot of it, and that can cause environmental problems. An increase of five degrees over a short period of time, in the annual average water temperature of a river, can cause major metabolic and reprodictive changes in cold blooded organisms. Paul M.