12.11. In a broad sense, the term quality assurance includes all actions necessary to provide adequate confidence that a component, structure, or system will perform satisfactorily in service. Engineering codes and stand­ards are an important aspect of quality assurance, since they represent the recognized practice for assuring acceptable levels of quality and perform­ance in materials and components. A number of preexisting codes, such as the ASME Boiler and Pressure Vessel Code (§7.26), have been im­proved, supplemented, or completely revised to satisfy requirements of the nuclear industry.

12.12. Standards have played a vital role in the practice of all branches of engineering for many years. These are generally developed by profes­sional society committees and represent a consensus for acceptable pro­cedures, quality requirements, or performance criteria. Often, uniform testing and evaluation methods are prescribed. Such development is co­ordinated by the American National Standards Institute (ANSI) (§8.42).

12.13. Hundreds of standards are relevant to the practice of nuclear engineering. These cover all aspects of nuclear power plant design, con­struction, equipment performance, and instrumentation, as well as the manufacturing of nuclear fuels. Many standards also deal with computer codes and information transfer. Since standards document accepted prac­tice, it is important for a nuclear reactor engineer to become familiar with those standards that are relevant to a given professional assignment. These are generally available in technical libraries or through ANSI.

12.14. Special code requirements are established for nuclear safety grade components, which are considered vital to plant safety. When such com­ponents such as valves are manufactured to meet these stringent require­ments, they may be labeled with an “N” stamp. Categorization into classes, depending upon safety significance, with differing requirements for quality assurance and in-service inspections is as follows:

Safety Class 1. This, the most vital category applies to components of the primary coolant system, whose failure would cause a major coolant loss.

Safety Class 2. In this category, we have structures and components that are required to fulfill a safety function such as shutting down the reactor, cooling other safety systems, and controlling the release of radioactivity.

Safety Class 3. This applies to systems whose failure would allow release to the environment of gaseous radioactivity that would normally be held for decay within the plant.

Nonsafety grade components must meet “high-quality industrial stand­ards.” Since a significant additional expense is associated with safety grade components, there has been in the past a design incentive to specify such components only for essential safety functions.

12.15. Many standards have been incorporated into Federal Regulations and Regulatory Guides issued by the U. S. Nuclear Regulatory Commission (NRC). General quality assurance criteria are specified in Title 10 of the Code of Federal Regulations, Part 50, Appendix В (10 CFR 50). Specific quality assurance requirements appear in the Regulatory Guide dealing with the particular topic considered.

12.16. There are five major aspects of a quality assurance program:

1. The actual formulation of the program itself includes specific detailed pol­icies and procedures.

2. Should design be required, quality control of the necessary practices is needed.

3. Component and material procurement activities require the enforcement of quality assurance requirements.

4. Inspection and test procedures are prescribed to assure that all specifications are met.

5. Auditing and record-keeping procedures are provided to assure adherence to requirements.