Refurbishment of Point Lepreau Generating Station

NB Power is planning to conduct an 18-month maintenance outage of the Point Lepreau Generating Station (PLGS) beginning in April 2008. The major activity would be the replacement of all 380 Fuel Channel and Calandria Tube Assemblies and the connecting feeder pipes. This activity is referred to as Retube. NB Power would also take advantage of this outage to conduct a number of repairs, replacements, inspections and upgrades (such as rewinding or replacing the generator, replacement of shutdown system trip computers, replacement of certain valves and expansion joints, inspection of systems not normally accessible, etc). These collective activities are referred to as Refurbishment. This would allow the station to operate for an additional 25 to 30 years. The scope of the project 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. 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 and 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) 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 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. The Refurbishment outage is preceded by a detailed Engineering Project Phase that includes: Finalizing details of the Retube process including modeling, tooling development, site facilities and training of personnel; Perform Engineering activities related to design modifications, safety analysis and level II PSA; Construction of new waste storage structures to house Retube Waste and other additional waste storage structures for the extended life of the station; Setup necessary temporary construction facilities (offices, storage areas, change rooms, decontamination and maintenance areas); Perform detailed outage planning; Initiate development of detailed layup, commissioning and return to service procedures; Procure equipment and components. Although final project approval is still pending, NB Power has been carrying on a limited scope of activities that are important in reducing overall project financial risk. A number of these up-front activities relate to safety analysis and licensing issues related to life extension. In particular, a level II PSA along with additional safety analyses are being performed to complement that which currently support the existing Operating License for the station. This paper discusses the Safety and Licensing activities that were involved in defining the project scope and outlines the safety analysis related activities that will be performed in support of the Refurbishment project and extended operation. (author)