FIELD-MEASUREMENTS OF BETA-RAY ENERGY-SPECTRA IN CANDU NUCLEAR GENERATING STATIONS

Field measurements of beta ray energy spectra have been carried out at various locations in CANDU nuclear generating stations operated by On tario Hydro. The beta ray energy spectrometer consists of a 5 cm diame ter x 2 cm thick BC-404 plastic scintillator situated behind a 100 mum thick, totally depleted, silicon detector. Photon events are rejected by requiring a coincidence between the two detectors. The spectromete r is capable of measuring electron energies from 125 keV to 3.5 MeV. B eta ray energy spectra have been measured for uncontaminated and conta minated fueling machine components. fueling machine swipes and a react or containment vault. The degree of protection afforded by various art icles of protective clothing has also been investigated for the variou s fueling machine components. Monte Carlo calculations have been used to estimate beta factors for 100 mg.cm-2 and 240 mg.cm-2 LiF-TLD chips , which are used as 'skin- and 'extremity' dosemeters in the Ontario H ydro Radiation Dosimetry Programme.