Applying operating experience to design the CANDU 3 process

The CANDU 3 is an advanced, smaller (450 MWe), standardized version of the CANDU now being designed for service later in the decade and beyond. The design of this evolutionary nuclear power plant has been carefully planned and organized to gain maximum benefits from new technologies and from world experience to date in designing, building, commissioning and operating nuclear power stations. The good performance record of existing CANDU reactors makes consideration of operating experience from these plants a particularly vital component of the design process. Since the completion of the first four CANDU 6 stations in the early 1980s, and with the continuing evolution of the multi-unit CANDU station designs since then, AECL CANDU has devised several processes to ensure that such feedback is made available to designers. An important step was made in 1986 when a task force was set up to review and process ideas arising from the commissioning and early operation of the CANDU 6 reactors which were, by that time, operating successfully in Argentina and Korea, as well as the Canadian provinces of Quebec and New Brunswick. The task force issued a comprehensive report which, although aimed at the design of an improved CANDU 6 station, was made available to the CANDU 3 team. By that time also, the Institute of Power Operations (INPO) in the U.S., of which AECL is a Supplier Participant member, was starting to publish Good Practices and Guidelines related to the review and the use of operating experiences. In addition, details of significant events were being made available via the INPO SEE-IN (Significant Event Evaluation and Information Network) Program, and subsequently the CANNET network of the CANDU Owners' Group (COG). Systematic review was thus possible by designers of operations reports, significant event reports, and related documents in a continuing program of design improvement. Another method of incorporating operations feedback is to involve experienced utility personnel in the early design stages of a project. This has been accomplished in a variety of ways for the CANDU 3 design, including visits to nuclear utilities, exchange of staff with utilities, and hiring of utility staff as consultants. Input from equipment manufacturers is also a key item, particularly in the area of the technical specifications that are produced by designers. CANDU 3 approached this by requesting comments on technical specifications from traditional or established suppliers and by pre-selecting major equipment suppliers in advance - to permit early discussions on equipment details, and by giving consulting contracts to suppliers to establish major design parameters. Design reviews have long been a traditional part of the design process. For the CANDU 3 participation of utility representatives has been actively solicited in order to incorporate their comments at an early stage. Some obvious benefits of this approach were in the areas of operational testing, maintainability, and that of the fuel channel design. The application of a more formal human factors program to CANDU 3 design has led to the development of a functional design methodology which requires designers in key areas to evolve their designs from operating procedures, and thus produce designs which are easier for operators and maintainers. This is the reverse of the traditional approach where operating procedures produced after design completion have had to adapt to design features. The paper includes an outline of the application of the functional design methodology to the design of an advanced control centre for CANDU 3. It also shows how operating and maintainability considerations have been factored in at all design stages based on inputs from operating utilities