Environmental qualification for class 1E electric equipment in nuclear power plant

This paper describes, from the view point of defense in depth, the significance and key points as well as procedures and approaches to environmental qualification for class 1E electric equipment in nuclear power plants. Principles presented in standards, such as IEEE323, R.G.1.89, and IEC780, are detailed to the extent of being operable. Meanwhile, expanded descriptions based on practices and experiences are presented upon the aging evaluation, which is a critical point in the whole job, to avoid misinterpretation of above principles. (author)