Determination of 60Co in high volumes of water samples

The average annual release of 58Co and 60Co from a WWER-440 nuclear power plant where it is generated as a corrosion product is within 0.37 GBq to 3.7 TBq. Samples of water and sediment were taken from the waste water channel of the Jaslovske Bohunice nuclear power plant and from the Dudvah river. The method of coprecipitation with iron hydroxide and subsequent selective precipitation by 1-nitroso-2-naphthol after dissolving the hydroxides in hydrochloric acid was used for concentrating the 60Co. The chemical yield of cobalt separation was 66+-2%. For comparison the method was simultaneously tried of concentrating cobalt on Na pectate. After drying the sorbent was gamma-spectrometrically measured, as was the resulting precipitate from the first procedure. Samples of the sediment were dried and gamma-spectrometrically measured using a well type scintillation NaI(Tl) crystal. The values of volume activity of the measured water are mostly statistically significant and exceed several times the value of minimum detectable water activity. The activity of 60Co in the sediment is 10 to 30 times higher than the volume activity of the water. (E.F.)