Efficiency Assessment of Sanitary-Technical Barriers in Nuclear Facilities by Means of Adhesive Decontaminating Foils

The efficiency of sanitary-technical barriers in Kozloduy NPP, Bulgaria, is investigated for the first time with adhesive decontaminating foils. The duration of use and retention coefficient are assessed using gamma-ray spectroscopy. The retained activity increases linearly up to a saturation point at 250 controlled persons. About 6% of the radioactive mechanical fraction is fixed on the adhesive. For three successive sanitary-technical barriers in the controlled zone, the activity is reduced by one to two orders of magnitude on each barrier towards the sanitary complex exit. The total activity released during annual maintenance is estimated to be 105 Bq. The radioactive contamination in the controlled zone is studied and correlations are established between two groups of isotopes, generated by the release of fission products and by neutron activation.Our investigation demonstrates that the sanitary technical barriers prevent efficiently the release of radioactivity from the controlled zone to the environment.