Division 1 of ASME Section III contains requirements for piping classified as ASME Class 1, Class 2, and Class 3. ASME Section III does not delineate the criteria for classifying piping into Class 1, Class 2, or Class 3; it specifies the requirements for design, materials, fabrication, installation, examination, testing, inspection, certification, and stamping of piping systems after they have been classified Class 1, Class 2, or Class 3 based upon the applicable design criteria and Regulatory Guide 1.26, Quality Group Classifications and Standards for Water-Steam, and Radio-Waste- Containing Components of Nuclear Power Plants. Subsections NB, NC, and ND of ASME III specify the construction requirements for Class 1, Class 2, and Class 3 components, including piping, respectively. Subsection NF contains construction requirements for component supports, and a newly added Subsection NH contains requirements for 1 Class 1 Components in Elevated-Temperature Service. Subsection NCA, which is common to Divisions 1 and 2, specifies general requirements for all components within the scope of ASME Section III.
Division 3 of ASME Section III is a new addition to the code and contains requirements for containment systems and transport packaging for spent nuclear fuel and high–level radioactive waste.
The construction requirements for ASME Class 1, Class 2, and Class 3 piping are based on their degree of importance to safety, with Class 1 piping being subjected to the most stringent requirements and Class 3 to the least stringent requirements. It is noted that a nuclear power plant does have piping systems other than ASME Class 1, Class 2, and Class 3, which are constructed to codes other than ASME Section III. For example, the fire protection piping systems are constructed to National Fire Protection Association (NFPA) standards, and most of the nonnuclear piping systems are constructed to ASME B31.1, Power Piping Code.
When joining piping systems or components of different classifications, the more restrictive requirements shall govern, except that connections between piping and other components such as vessels, tanks, heat exchangers, and valves shall be considered part of the piping. For example, a weld between an ASME Class 1 valve and ASME Class 2 piping shall be made in compliance with the requirements of Subsection NC, which contains rules for ASME Class 2 components, including piping (refer to Fig. A4.2).
Effective Edition, Addenda, and Code Cases
Selection of effective editions and addenda of ASME Section III shall be based upon the following guidelines:
Only the approved edition(s) and addenda of ASME Section III, incorporated by reference in 10 CFR 50.55a, Paragraph (b) (1) are to be used for construction of items within the scope of ASME Section III.
The latest published edition and addenda of ASME Section III may not be approved by the U.S. NRC; therefore, their use can only be made after seeking special permission from the U.S. NRC. Refer to 10 CFR 50.55a, Codes and Standards from time to time to find which edition and addenda of ASME Section III have been approved by the U.S. NRC.
As per Subsubarticle NCA-1140, in no case shall the code edition and addenda dates established in the design specifications be earlier than three years prior to the date the nuclear power plant construction permit application is docketed. In addition, the guidelines of preceding paragraphs shall apply.
Code editions and addenda later than those established in the design specification and documents per the above-delineated approach may be used provided they are approved for use. Also, specific provisions within an edition or addenda later than those established in the design specifications and documents may be used provided all related requirements are met.
All code items, including piping systems, may be constructed to a single code edition and addenda, or each item may be constructed to individually specified code editions and addenda.
The use of code case(s) is optional. Only the U.S. NRC–approved code cases with or without limitations or additional requirements published in the following regulatory guides may be used without a specific request to the U.S. NRC for approval:
Regulatory Guide 1.84: Design and Fabrication Code Case Acceptability ASME Section III, Division 1.
Regulatory Guide 1.85: Materials Code Case Acceptability ASME Section III, Division 1.
The code cases not listed as approved in Regulatory Guides 1.84 and 1.85 may be used only after seeking permission from the U.S. NRC for the specific application. #Little_PEng