Thursday, October 25, 2007

Center of the storm

For over one year, my life has revolved around some of the issues addressed in this NRC letter. A PDF of the letter is available at the NRC's ADAMS document management system. Perform an Advanced Search and enter "Babcock Wilcox" in the Search: box and "10/09/2007" in the Document Date box to view the document (I have not been able to create a direct link).

To stay on the safe side of a confidentiality agreement I will not be commenting on this matter. Below is a relevant excerpt, you may draw your own conclusions.

Note to John Sullivan, I think this is the information you were fishing for this past March.
b.2 Implementation of the Welding Procedures

The inspectors interviewed a BWC Weld Operator who worked on the Palisades RRVCH. The weld operator described that the Section 6.2.6 visual inspection was to be performed after all grinding was complete on a weld layer. The weld operator noted surface defects were visually identifiable on many welds before grinding. The weld operator would then grind the surface of the weld layer to remove all visual indications. On average, the weld operator stated that he is required to remove approximately 30 percent of the weld layer. The weld operator stated that he would go beyond the estimated 30 percent material removal if a flaw was still visible. Once he had completed all grinding, he would do a visual inspection with a magnifying glass to look for any cracks in accordance with Section 6.2.6 of SIS 259695. The weld operator noted when he performed this visual inspection that no cracks were identified on any weld layer he inspected.

The inspectors identified a failure of BWC weld operators to follow the requirements of Section 6.2.6 of SIS 295695. If, as performed by weld operators working on the Palisades head, grinding was performed until all visual evidence of cracking was removed from the weld layer surface to any depth, then the visual examination for cracking after the grinding operation was complete would find no flaws. Section 6.2.6 stated the layer was to be ground and visually examined by the operator for any cracking. This issue is identified as one example of Nonconformance 99900067/2007-201-02.

The inspectors found that the grinding step described in Section 6.2.6 would be reasonably interpreted to be grinding to a sufficient depth to remove the oxide layer and prep for welding. Removal of 30 percent or more of the weld layer necessary for the removal of all visible flaws goes beyond a general grinding procedure to prep a weld surface for the next layer to be applied. Further, the statement in Section 6.2.6 to "ground remove” flaws, if identified, implied a difference in intended grinding operations. The inspectors found the weld operator’s definition of grinding to go beyond oxide layer removal, to a point of flaw removal was incorrect given the wording of Section 6.2.6. Grinding to remove a flaw should reasonably imply, as stated in Section 6.2.6, a step to perform a PT inspection to verify flaw removal.

c. Conclusions
The inspectors determined through a review of welding and inspection activities associated with the production of the butter weld layers for the Calvert Cliffs and Palisades RRVCHs that BWC is in accordance with the requirements of ASME Code.

1 comment:

Dad29 said...

So B&W had this little problem in addition to their built-in heat-sink?

Were those design engineers grads of MATC, or what?