CSA N285.0.1-18 pdf download – Commentary on CSA N285.0-17, General requirements for pressure-retaining systems and components in CANDU nuclear power plants.
1.2 Historical background The requirements in the Standard are based on provincial and federal regulations, practices developed in the design and construction of CANDU nuclear power plants, and the proven and widely adopted rules of ASME BPVC, Section III, Division 1. Their fundamental goal is to ensure public safety. Since the first Standard in the CSA N285 series was issued, regulations and best practices have evolved as the industry gained design, construction, commissioning, and operational experience. However, the basic pressure boundary requirements have not changed significantly and are based on the long-standing ASME and industrial practices. Where such changes have occurred, they are described in the appropriate sections. The first CSA N285 Standard, a preliminary edition, was issued in 1975 and included both general requirements and specific requirements for Class 1, 2, and 3 components. Because provincial acts and regulations took precedence over ASME BPVC, Section III, Division 1, the 1975 edition included an appendix that listed the ASME BPVC, Section III, Division 1 paragraphs that was not applicable to nuclear power plants in Canada. These paragraphs dealt with authorization, stamping, and reports. In 1981, the content of CSA N285 were divided between two Standards, with general requirements in CSA N285.0 and requirements for Class 1, 2, and 3 systems and components in CSA N285.1.
CSA N285.1, CSA N285.2, and CSA N285.3 were incorporated into CSA N285.0 so that all the technical requirements for pressure-retaining systems and components would be in one Standard. This also had the benefit of lowering overhead costs for CSA Group in terms of number of staff required to manage the program and the cost of publication. Because it was desirable to maintain the numbering system of the various material Standards in CSA N285.6, it was not possible to incorporate them into CSA N285.0. Therefore, CSA N285.6 has been published as a companion document to CSA N285.0 since CSA N285.0-08 as these material Standards are closely related to the design rules in CSA N285.0. CSA N285.0 and ASME BPVC, Section III, Division 1 set forth requirements for pressure-retaining components. CSA N285.0-17 is based on years of experience in designing, fabricating, installing, and operating pressure-retaining systems and components that have a high degree of integrity and safety. However, codes and standards cannot consider and address every circumstance. Consequently, whether a circumstance is addressed or not, the designer, certificate holder, installer, and operator are still expected to use good engineering judgment to ensure that nuclear power plants are constructed and operated reliably and safely.
In Canada, all nuclear reactors for power production are of the CANDU design at this time. There are both single-unit and multi-unit station configurations. The CANDU reactor is a pressurized heavy water reactor that makes use of multiple horizontal zirconium alloy pressure tubes in its high-pressure heat- transport system, through which the pressurized heavy water coolant flows over natural uranium fuel bundles, removing the heat of the fission reaction. CANDU designs feature a calandria which houses a low-pressure heavy water moderator, and a relatively low-pressure containment system in existing plants. In contrast, the fuel in the pressurized water reactor (PWR) and boiling water reactor (BWR) designs is located in a single large pressure vessel through which the coolant flows over the enriched uranium fuel. ASME BPVC, Section III, Division 1 was developed based on the PWR and BWR concepts. Also, ASME BPVC and CSA N285.0 were developed according to different philosophies. ASME BPVC, Section III, Division 1 is written at a component level and only covers the technical requirements for the construction of new components and supports after they have been classified, whereas CSA N285.0 includes requirements for classification of systems and components, plant and system documentation, and registration. Once the systems have been classified and the classification boundaries have been identified, then the components and supports adopt the classification of the system. The construction of these items is based on technical requirements that are either the same or similar to those in ASME BPVC, Section III, Division 1.CSA N285.0.1-18 pdf download.
