Activity estimation of noble gases released from nuclear power plants

The activities of noble gases in airborne effluents released from normally operating nuclear power plants are generally lower than the corresponding detection limits. Thus the statistic report using the halves of the detection limits as the releases probably overestimates the radioactive levels of nuclides, which may be higher than that of the similar PWRs worldwide, and eventually weaken the rationality of the releases evaluation. Since the monitoring data of the released noble gases has been seldom publicly reported, their activity concentrations are theoretically calculated based on the primary coolant source terms, and the monitoring ability is evaluated by comparing the calculated results with the detection limits of both on-line monitoring systems and sampling measurement systems. Some suggestions are provided on the effluents monitoring and the release data statistics. (authors)