Dissolved stable noble gas measurements from primary water of Paks NPP

Monitoring of dissolved noble gases in the primary water of a VVER type NPP can provide relevant information about the kilter of heating rods and detailed additional information about some working parameters. A sampling and measuring method of noble gases from the primary circuit was developed. The helium concentrations and 3He/4He ratios can be used to estimate the content of tritium and alpha emitting isotopes of the primary water. By argon content measurements the air penetration and the required hydrazine amount for the oxygen absorption can be estimated with high accuracy. Continuous monitoring of the concentration and isotope ratios of Xe and Kr in the dissolved gas is a good tool for high sensitivity detection of small leakage of fuel elements. In case of Unit 3, xenon surplus was detected. Considering the isotope composition results of xenon about 76% of its total amount is uranium fission origin. These results indicate possible leakage of fuel rods. (R.P.)