[en] Safety analysis activities at Gentilly 2 nuclear power plant are described, including historical record of the plant operation and safety approach guidelines. 1 figs

[en] A station specific version of the code SMOKIN is being set up at Hydro-Quebec for the Gentilly-2 Nuclear Generating Station. The original version of the code was developed by Ontario Hydro and is based on lambda mode expansion of the neutron flux. The code has been restructured, and a full set of the Reactor Regulating System routines is implemented in it. Preliminary results of simulations of shutdown system 1 and a power manoeuvre from 80% to 100% are presented. A first application to computer assisted training is described

[en] Managing safety and safety aspects of aging at CANDU nuclear power plants are discussed

[en] An integral representation is derived for the Coulomb amplitudes in the generator coordinate theory of nuclear reactions. A numerical application is given for the s-wave of α-α scattering. (orig.)

[en] As reported at the 1996 CNS Annual Conference, in mid-1995 the CANDU industry began to develop validation matrices for CANDU power plants. Of the eight matrices required to address all physical phenomena that could occur in all relevant accident categories, two have been prepared and tabled with the Atomic Energy Control Board, and the remaining six are targeted for submission during 1997. The matrices provide the generic, code-independent knowledge base that will be used to validate major safety analysis codes over the next four years. The unique achievement reported in this paper is the identification and listing of all physical phenomena in all relevant accident categories. (author)

[en] 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)

[en] New Brunswick Power Nuclear Corp. (NBPNC) 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 Nuclear 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 comprehensive 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. The work pertaining to Plant Life Extension was divided into design review and analysis review. The design review encompassed specific studies associated with safety margin improvements, studies to determine whether addition safety improvements should be made, and possible economic improvement related changes. The intent was to conduct a review to identify potential changes. For those potential changes that were deemed appropriate for further consideration, preliminary design packages were prepared. These packages included a Benefit Cost Analysis (BCA) to assist the project team in determining which changes were appropriate to include in the project scope. One of the specific tasks identified under the sub-category of safety margin improvements is the determination of potential upgrades to Shutdown Systems (SDS) to improve trip coverage. The project consolidation and review process resulted in potential shutdown system upgrades that include the installation of SDS2 high pressure trip on outlet headers 3 and 7, modifications to set-points of some existing trips to enhance coverage, and addition of high and low moderator level trips on both shutdown systems. Although final project approval is still pending, NB Power Nuclear 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 pertain to safety analysis and licensing issues related to life extension. Included in these up-front activities are trip coverage preliminary design assist analyses for the loss of primary heat transport system flow and moderator events to support the design changes to be implemented during the refurbishment outage. This paper provides a highlight of the process used to establish the trip coverage related design changes to be implemented as part of the refurbishment program. A discussion of the trip coverage improvements is also presented. (author)

[en] Since the 1960s, the CANDU industry has been developing and using scientific computer codes, validated according to the quality-assurance practices of the day, for designing and analyzing CANDU power plants. To provide a systematic framework for the validation work done to date and planned for the future, the industry has decided to adopt the methodology of validation matrices, similar to that developed by the Nuclear Energy Agency of the Organization for Economic Co-operation and Development for Light Water Reactors (LWR). Specialists in six scientific disciplines are developing the matrices for CANDU plants, and their progress to date is presented. (author) 1 ref., 5 tabs., 1 fig

[en] Since the 1960s, the CANDU industry has been developing and using scientific computer codes for designing and analysing CANDU power plants. In this endeavour, the industry has been following nuclear quality-assurance practices of the day, including verification and validation of design and analysis methodologies. These practices have resulted in a large body of experience and expertise in the development and application of computer codes and their associated documentation. Major computer codes used in safety analyses of operating plants and those under development have been, and continue to be subjected to rigorous processes of development and application. To provide a systematic framework for the validation work done to date and planned for the future, the industry has decided to adopt the methodology of validation matrices for computer-code validation, similar to that developed by the Nuclear Energy Agency of the Organization for Economic Co-operation and Development and focused on thermalhydraulic phenomena in Light Water Reactors (LWR). To manage the development of validation matrices for CANDU power plants and to engage experts who can work in parallel on several topics, the CANDU task has been divided into six scientific disciplines. Teams of specialists in each discipline are developing the matrices. A review of each matrix will show if there are gaps or insufficient data for validation purposes and will thus help to focus future research and development, if needed. Also, the industry is examining its suite of computer codes, and their specific, additional validation needs, if any, will follow from the work on the validation matrices. The team in System Thermalhydraulics is the furthest advanced, since it had the earliest start and the international precedent on LWRs, and has developed its validation matrix. The other teams are at various stages in this multiphase, multi-year program, and their progress to date is presented. (author)

[en] Computer codes are used in the Canadian nuclear industry for design support and safety analysis of CANDU reactors and small reactors, and in the provision of analysis services to its internal and external customers. Many of these codes were brought into service during the growth years of the nuclear power industry in Canada (mid 1970's to late 1980's). Typically, validation was conducted during the development of the codes to ensure their adequacy, however the validation process followed was not formalized. Similarly, the software engineering processes employed during their development and subsequent maintenance were not necessarily consistent with modern standards. In the mid-1990's the Canadian nuclear industry undertook a number of projects to upgrade the quality of safety analysis software. Atomic Energy of Canada Limited (AECL) established a safety analysis code Validation Project and Ontario Power Generation Incorporated (OPGI) - formerly Ontario Hydro - established a Verification and Validation of Safety Analysis Software Project as part of its Integrated Improvement Program (IIP). Underlying forces driving these projects included concerns raised by the regulator regarding the quality of safety analysis software and the need to conform to newly-issued Canadian quality assurance standards, specifically CSA N286.7. These projects involve establishing either formal software validation or software verification and validation methods, together with design recovery of the software and its documentation. The objectives of the projects are to ensure: - that there is a low likelihood of errors being introduced into safety analysis that are due to deficiencies in the software, - a documentation base exists for the codes that would demonstrate to the regulator that acceptable quality exists and - that the codes are formally qualified for their intended applications. As these projects were being established it was recognized that developments to enhance capabilities, verification, validation, qualification and maintenance of these codes represents a large commitment of resources from organizations within the industry. Furthermore, there was the definite likelihood of redundant work being executed at the different organizations. Compounding these considerations was the fact that the timeliness and effectiveness of review by the regulator of licensing submissions based upon results obtained with these codes could be detrimentally affected by the number and diversity of codes. Therefore, in order to achieve benefits from more efficient resource utilization and reduced licensing risk, an initiative has been undertaken to establish a consolidated common set of computer codes for safety analysis, referred to as the Industry Standard Toolset (IST) initiative. (authors)