Waste water from a plant operating reactors and processing spent fuel contains many radionuclides, formed both by neutron capture and by fission. Methods of analysis and typical findings are reported for a variety of aqueous samples including: reactor coolant, water from a settling basin and pits, seepage from pits, underground water, and water from a river. Analysis by radiochemical methods is described, and considerable attention is given to measurement of gamma-emitters by scintillation spectrometry, a versatile technique for identification and quantitative determination. Most of the materials described are characterized by moderate levels of radioactivity. A brief description is given of techniques for measuring extremely small concentrations of radioelements.