Pickering Unit-1 and -4 Fuel Channel Reconfiguration

Abstract

For CANDU® reactors, pressure tube growth requires that one end of the Fuel Channel (FC) is fixed while the other is free to float on bearings. As the FCs run out of bearing length on the free end, two maintenance solutions exist: Reconfiguration reverses the fixed and free ends, allowing growth in the opposite direction, and Repositioning, which involves shifting FCs back towards the locked end, thus providing additional bearing length at the free end.Pickering ‘A’ Large Scale Fuel Chanel Replacement (LSFCR) only installed Positioning Assemblies (PAs) on one side of the reactor, as end-of-life projections indicated that bearing length could be managed by Repositioning only. The opposite reactor face was left without PA installation to minimize risks associated with feeder clearances and additional unit outage.With life extension of Pickering Unit-1 and -4 beyond 2014 however, there was risk that feeder clearances would be insufficient to support shifting of the channels. To combat this dilemma, a new PA design was commissioned that allowed installation on each channel’s free end allowing for reconfiguration.While advantageous, the modified PA reconfiguration presented significant challenges: major design modifications to the reactor, timely design and manufacturing of ASME code components, and critical development of tooling, methods and procedures.A partial installation of these modified PAs in 2012 provided lessons-learned for working with the new PA designs. This OPEX was fully leveraged, and in 2015 Unit-1 reconfiguration was completed successfully, followed by Unit-4 in 2016. Both reconfiguration projects were executed with a composite team lead by OPG IMS. Both were completed safely, and within schedule, cost and dose targets.This technical paper will review the salient reactor modification design considerations, the development of the execution methodology (tooling, procedures and training), and a survey of outage results and OPEX applicable to future reactor maintenance projects.