Characterization of the Radiochemical Activity in CANDU Steam Generators

The scope of mid-life refurbishment activities at some CANDU plants includes replacement of the existing steam generators. Shipment of the discarded steam generators for interim storage, intact disposal or for recycling via metal melting requires an assessment of dose rates and the inventory of radionuclides within the components. Kinectrics was contracted by CANDU utility owners to develop such data. This paper presents the detailed methodology employed to develop dose rate and radionuclide inventory data for radionuclides within both in-service and the out-of-service (in-storage) steam generators. The data were developed as follows: a) archived tube sections from various steam generators were characterized; scaling factors were derived using the detailed alpha and beta activity data obtained, b) in-situ gamma spectrometry (using germanium and cadmium zinc telluride detectors) and dose rate surveys were performed at various steam generators and c) a detailed assessment of the tritium inventory in various primary and secondary side components was performed.