Document: NRC Regulatory Guide
Document ID: a4944d20-ef6e-480b-a45d-14425bedd2e5
Document Type: regulatory_guide
Title: ASME Code Cases Not Approved for Use (Rev. 8)
Source: NRC Regulatory Guide Division 1
Source URL: https://www.nrc.gov/docs/ML2219/ML22196A065.pdf
Revision Date: 2023-05
Chapter: 
Section ID: RG-1.193
CFR Part: 
CFR Title: 

Content:
cal basis for the exclusion of data from the analysis to develop the FOIs as presented in Code Case N-909. 7/19E DG-1408, Page 22 3. Unacceptable OM Code Cases The NRC determined that the following OM Code Cases were unacceptable for use by licensees in their inservice testing programs. To assist users, new and revised Code Cases are shaded in grey to distinguish them from those listed in previous versions of this guide. Table 3. Unacceptable OM Code Cases CODE CASE NUMBER TABLE 3 UNACCEPTABLE OM CODE CASES SUMMARY OF BASIS FOR EXCLUSION EDITION/ ADDENDA OMN-10 Requirements for Safety Significance Categorization of Snubbers Using Risk Insights and Testing Strategies for Inservice Testing of LWR Power Plants The method used for categorizing snubbers could result in certain snubbers being inappropriately categorized as having low safety significance. These snubbers would not be adequately tested or inspected to provide assurance of their operational readiness. In addition, unexpected extensive degradation in feedwater piping has occurred which would necessitate a more rigorous approach to snubber categorization than presently contained in this Code Case. Note: The 2006 Addenda does not include Pages C-31 through C-34 of Code Case OMN-10. 2000 Addenda 2001 Edition 2003 Addenda 2004 Edition 2006 Addenda (see Note) 2009 Edition 2012 Edition 2015 Edition 2017 Edition 2020 Edition OMN-15 Requirements for Extending the Snubber Operational Readiness Testing Interval at LWR Power Plants The following list summarizes the issues that the NRC has identified: (1) The basis for the snubber degradation rate that is assumed in the White Paper for the Code Case is not clear. (2) The Code Case does not address snubber service life monitoring requirements when using the 1995 Edition of the OM Code. (3) The Code Case does not address the assignment of unacceptable snubbers in the failure mode group. (4) The Code Case does not address the treatment of isolated snubber failures. (5) The