The following was received via fax and is summarized below:
The attachment to this letter provides a report in accordance with 10 CFR 21.21 pertaining to deviations and potential defects in structural module CA33 for the Vogtle Unit 3 AP 1000r project. This issue was previously described in interim reports submitted by Greenberry in letters dated June 24, 2016 (NRC Log No. 2016-36-00, Accession No. ML16188A160) and July 26, 2016 (NRC Log No. 2016-36-01, Accession No. ML16229A180).
During fabrication of other submodules for CA35, it was discovered by Greenberry personnel that some weld cracking had occurred. During metallurgical examination, a second condition was discovered of presence of a heat affected zone and cracks in plate edges induced by plasma cutting in an area not to be welded. In order to evaluate the extent of the condition, Greenberry Industrial requested that the purchaser, WECTEC LLC, return the CA33 submodules that had already been delivered. The returned components have been inspected and it was determined that weld deviations were also present in the previously delivered submodules. Due to the use of the same plasma cutting method on CA33, it is expected that the plate edges on the returned CA33 modules also have cracks on the unwelded edges from the plasma cutting. The plasma cutting induced cracks on subsequently welded edges are typically mitigated by the welding processes for the affected edges. The cracks remaining in unwelded edges may not be a detrimental condition. This will be determined as part of further analysis of the identified conditions.
The affected material with weld defects has been returned by the purchaser, WECTEC LLC, to the supplier, Greenberry Industrial. Identification and resolution of other affected modules due to plate edge cracking will be performed when the technical evaluation of that condition is complete. The plate edge cracking may not be detrimental to the component performance.
If you have any questions pertaining to this information, please contact Mark Stapleton, Nuclear Operations Manager, at 360-567-0006 Ext. 1018.