title: A fence line noble gas monitoring system for nuclear power plants.
abstract: A noble gas monitoring system has been installed at Ontario Power Generation's Pickering Nuclear Generating Station (PNGS) near Toronto, Canada. This monitoring system allows a direct measure of air kerma from external radiation instead of calculating this based on plant emission data and meteorological models. This has resulted in a reduction in the reported effective dose from external radiation by a factor of at least ten. The system consists of nine self-contained units, each with a 7.6 cm x 7.6 cm (3 inch x 3 inch) NaI(TI) detector that is calibrated for air kerma. The 512-channel gamma ray spectral information is downloaded daily from each unit to a central computer where the data are stored and processed. A spectral stripping procedure is used to remove natural background variations from the spectral windows used to monitor xenon-133 (133Xe), xenon-135 (135Xe), argon-41 (41Ar), and skyshine radiation from the use of radiography sources. Typical monthly minimum detection limits in air kerma are 0.3 nGy for 133Xe, 0.7 nGy for 35Xe, 3 nGy for 41Ar and 2 nGy for skyshine radiation. Based on 9 months of continuous operation, the annualised air kerma due to 133Xe, 135Xe and 41Ar and skyshine radiation were 7 nGy, 8 nGy, 26 nGy and 107 nGy respectively.
authors.affiliation: GAMMA-BOB Inc, Gloucester, Ontario, Canada.
authors.forename: R L
authors.initials: RL
authors.lastname: Grasty
authors.forename: J
authors.initials: J
authors.lastname: Hovgaard
authors.forename: J R
authors.initials: JR
authors.lastname: LaMarre
mesh_terms: D000388:Air; D001417:Background Radiation; D002138:Calibration; D009010:Monte Carlo Method; D005741:Noble Gases / Q000032:analysis*; D009688:Nuclear Reactors; D011210:Power Plants; D011834:Radiation Monitoring / Q000379:methods*; D012815:Signal Processing, Computer-Assisted; D013051:Spectrometry, Gamma
chemical_list: D005741:Noble Gases