Relaxation of Containment - Pickering NGS-A Unit 3 Rehabilitation Outage

Abstract

A reactor containment system provides designed barriers between radioactive sources in reactor systems and the general public. Normally, access to the reactor systems is controlled via airlocks in the Reactor Building so that the containment system integrity can be maintained unimpaired. During reactor retubing, however, a more direct access to the reactor is necessary in order that retubing operations can be conducted efficiently. The Pickering NGS Containment System is described briefly together with the detailed strategy adopted to relax the guidelines governing containment, which permits a less restrictive access to the reactor. Topics discussed include prerequisite work, the control strategy and procedures employed during relaxation as well as supporting analyses. Of particular importance is the need to maintain quality and operational standards , where required, so that the containment envelope can be reestablished quickly when and if required. This paper will be of interest to all CANDU owner/operators regardless of containment design and is potentially of interest to operators of other containment designs. It is anticipated that future containment relaxations at other CANDU sites in Canada will follow this strategy as a baseline.