NRC SFST ISG-4: Cask Closure Weld Inspections

The closure weld for the outer cover plate for austenitic stainless steel designs may be
inspected using either volumetric or multiple pass dye penetrant techniques subject to the
following conditions:
• Dye penetrant (PT) examination may only be used in lieu of volumetric
examination only on austenitic stainless steels. PT examination should be done
in accordance with ASME Section V, Article 6, “Liquid Penetrant Examination.”
• For either ultrasonic examination (UT) or PT examination, the minimum
detectable flaw size must be demonstrated to be less than the critical flaw size.
The critical flaw size should be calculated in accordance with ASME Section XI
methodology; however, net section stress may be governing for austenitic
stainless steels, and must not violate Section III requirements. Flaws in
austenitic stainless steels are not expected to exceed the thickness of one weld
bead.
• If PT examination alone is used, at a minimum, it must include the root and final
layers and sufficient intermediate layers to detect critical flaws.
• The inspection of the weld must be performed by qualified personnel and shall
meet the acceptance requirements of ASME B&PV Code Section III, NB-5350 for
PT examination and NB-5332 for UT examination.
• If PT examination alone is used, a design stress-reduction factor of 0.8 must be
applied to the weld design.
• The results of the PT examination, including all relevant indications, shall be
made a permanent part of the licensee’s records by video, photographic, or other
means providing a retrievable record of weld integrity. Video or photographic
records should be taken during the final interpretation period described in ASME
Section V, Article 6, T-676

Revision 1