General requirements for design

SSCs and software for instrumentation and control that are important to safety shall be first specified and then classified according to their function and 

This classification reflects the significance for nuclear safety of the SSCs. Its purpose is to establish a gradation in the appUcation of the requirements for design and the requirements for quality assurance. There are other possible classifications or categorizations of SSCs according to other aspects (e.g. the seismic categorization of SSCs). 

Codes and standards applicable to SSCs shall be identified and their use shall be in accordance with their classification (see paras 6.12 and 6.13). In particular, if different codes and standards are used for different types of items (e.g. for piping and for electrical systems), consistency between them shall be demonstrated. 

In the case of SSCs for which there are no appropriate established codes or standards, an approach derived from existing codes or standards for similar equipment may be applied, or, in the absence of such codes and standards, the results of experience, tests, analysis or a combination of these may be applied, and this results based approach shall be justified. 

An analysis of the postulated initiating events shall be made to establish all those internal events that could affect the safety of the research reactor facility. These events may include equipment failures or malfunctions. 

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NFPA 86 (sections 4-3.2, 4-4.5, and 5-6) provides general requirements for designing oxygen-enriched combustion air pipelines. The following are specific concerns related to the air main pipeline design. 

In Switzerland there are two BWR units. One plant, a GE BWR-4 type, was taken into operation in 1971, the other, a GE BWR-6 type plant, is operating since 1984. Regulatory guidelines are provided by the HSK, the Swiss Federal Nuclear Inspectorate. Generally, requirements for design and analysis are in accordance with ASME HI. Requirements for inspection are defined in the NE-14 regulation provided by the SVTT, the Swiss Association for Technical Inspections. 

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