Refurbishment of Point Lepreau Generating Station

Abstract

NB Power is conducting an 18-month maintenance outage of the Point Lepreau Generating Station (PLGS) which began on March 28, 2008 (Reference-1). The major activity is the replacement of all 380 Fuel Channel & Calandria Tube Assemblies and the connecting feeder pipes. This activity is referred to as Retube (Reference 2). NB Power is also taking advantage of this outage to conduct a number of repairs, replacements, inspections & upgrades (such as rewinding or replacing the generator, replacement of shutdown system trip computers, replacement of certain valves & expansion joints, inspection of systems not normally accessible, etc). These collective activities, as well other regular maintenance and inspection activities are referred to as Refurbishment. This would allow the station to operate for an additional 25 to 30 years. Work on the project began in early 2000. The scope was determined from the outcome of a two-year study involving a detailed condition assessment of the station that examined issues relating to ageing and obsolescence (Reference-3). The majority of the plant components were found to be capable of supporting extended operation without needing replacement or changes. In addition to the condition assessment, a detailed review of Safety & Licensing issues associated with extended operation was performed. This included a review of known regulatory and safety issues, comparison of the station against current codes and standards, and comparison of the station against safety related modifications made to more recent CANDU 6 units. Benefit cost analyses (BCA) (Reference-4) were performed to assist the utility in determining which changes were appropriate to include in the project scope. As a Probabilistic Safety Assessment (PSA) for PLGS did not exist at the time, a risk baseline for the station had to be determined (Reference-5) for use in the BCA. Extensive dialogue with the Canadian Nuclear Safety Commission staff was also undertaken during this phase. A comprehensive Licensing Framework was produced upon which the CNSC provided feedback to NB Power. This feedback was important in terms of achieving clarity of the regulatory position and thus to minimize the financial risk associated with regulatory uncertainty.