Radiation Field Control in Ontario Hydro Reactors

Abstract

The main contributor to radiation fields found during maintenance of the Primary Heat Transport (PHT) System components of Ontario Hydro reactors is Cobalt-60. Techniques have been developed to control these radiation fields. This paper discusses two of these techniques with reference to the 8 unit Pickering Nuclear Generating Station (PNGS). For newer reactors (Units 5-8) reducing the amount of Cobalt-59, the Cobalt-60 precursor, in the materials of construction has successfully reduced Cobalt-60 radiation fields. For older reactors (Units 1-4) where reduced Cobalt-59 was not specified, chemical decontamination of the PHT system has effectively reduced radiation fields when required.