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:
ER TABLE 1 UNACCEPTABLE SECTION III CODE CASES SUMMARY DATE OR SUPPLEMENT/ EDITION N-818-1 Use of NDE and Fracture Mechanics for Acceptance of Full Penetration Butt Welds in Lieu of Weld Repair, Class 1 and Class 2, Section III, Division 1 Code Case N-818-1 contains provisions for applying the results of nondestructive examinations and fracture mechanics calculations to accept flaws in full penetration butt welds of ferritic vessels and austenitic and ferritic piping in lieu of repair in accordance with the ASME Code, Section III, when the radiography indicates that the welds cannot satisfy NB-5000 or NC-5000 of Section III during preservice examinations. The NRC staff has the following concerns regarding the provisions of UT and other issues in this code case. 1. The code case applies to ferritic, austenitic stainless steel, and dissimilar metal welds. However, UT in lieu of radiograph testing (RT), at this time, has only been qualified as described in Code Case N-831) for ferritic materials. The NRC staff has reviewed and approved relief requests for UT in lieu of RT that utilized the qualification approach described in CC N-831 for ferritic materials only. To date, the technical basis for the use of UT in lieu of RT for austenitic welds has not been sufficiently developed to allow The NRC staff to accept UT in lieu of RT on austenitic stainless steel or dissimilar metal welds. 2. Single side access in not acceptable for fabrication examinations because some flaws are only detectable from one direction. 3. Second leg of UT V-path may be acceptable to use on a limited basis for ferritic material, but will not be acceptable for austenitic stainless steel or dissimilar metal welds. 4. Surface preparation needs to be addressed. Welds must be conditioned without any gap more than 1/32-inch between transducer and weld. 5. Paragraph (g) of the code case seems to be the discussion of a calibration block, not a qualification block. 6. Paragraph I-3.2(d) states that