05000255/FIN-2011012-01
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| Description | Palisades has three safety-related SW pumps that draw water from Lake Michigan to provide cooling to safety-related and non-safety-related components. Each pump has eight couplings to connect shaft sections. In 2009, the plant began a material change for the couplings and shafts from carbon steel to 416 Martensitic SS due to erosion issues of the carbon steel material. The material would be changed in series in of pumps P-7A, P-7C, and P-7B respectively. The timeline (Attachment 3) includes specific dates. In 2009, SW pump P-7C failed due to cracked coupling #7, resulting into entry a TSAC, requiring the plant to shut down if the pump was not returned to service within 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />. Metallurgical data on the failed coupling revealed the coupling hardness was significantly higher than the design specification. The specified hardness range was Rockwell C value of 28-32 Rc. Hardness readings on the failed coupling ranged from 37-41 Rc. The vendor, HydroAire, had supplied the couplings with certifications that the couplings were within the specified hardness. This failure was entered into the licensees corrective action program and identified as a significant condition adverse to quality (SCAQ). At the time of the failure, no spare couplings were available. Immediate discussions with HydroAire ensued to obtain replacement couplings within the 72-hour timeframe. Based on the hardness data received on the failed coupling, which conflicted with the certification received from the vendor, the licensee verbally imposed additional requirements to obtain independent laboratory hardness checks on the replacement couplings. The requirement for independent hardness checks on the replacement couplings was not incorporated into the procurement process. Procurement documents were not updated with this additional requirement, and procurement personnel, such as the licensee procurement manager at the vendor site or the plant receipt inspection personnel, were not made aware of the additional requirement. Procedure EN-MP-100, Critical Procurements, was not implemented even though criteria in the procedure, such as previous vendor issues, how critical the couplings were on plant operation, and the short procurement timeframe, appear to have been satisfied. Eight replacement couplings were received and immediately installed in the pump; the pump was returned to service within the 72-hour requirement. Soon after the pump was returned to service, the licensee discovered that independent hardness checks were not performed. The vendor did provide certifications indicating that the couplings had hardness values in the specified range. An additional ten couplings were ordered and received soon after the pump was returned to service. Independent hardness checks completed on these spare couplings agreed with vendor hardness results, thus providing some assurance to the licensee that the couplings currently installed in pump P-7C were of the correct hardness. On August 9, 2011, SW pump P-7C was declared inoperable due to the failure of coupling #6. This failure was entered into the licensee corrective action program and identified as a SCAQ. The cause of the failure had not been determined at the time this SIT report was completed. However, hardness results obtained from an independent metallurgical lab from four of the in-service couplings, including the coupling that failed, were found to have at least one spot of higher hardness than specified, greater than Rockwell Hardness value of 32 Rc. No hardness values approached the 37-41 Rc observed in the 2009 failure (the values were less than 34Rc). Therefore, the inspectors were concerned that the licensee did not ensure the vendor-supplied couplings with correct hardness values in 2009. Pending final results and conclusions from the metallurgical analysis and root cause analysis, the licensee may have failed to take measures in 2009 to assure that purchased material and equipment conform to the procurement documents, including provisions for, as appropriate, objective evidence of quality furnished by the contractor as required by Appendix B. The 2009 coupling failure root cause evaluation was focused on the material hardness. It did not fully evaluate the effect of other material properties, such as toughness which is discussed in the operating experience, nor the change of material properties from heat treatment on the susceptibility of the couplings to IGSCC. Corrective actions after the 2009 failure did not address the heat treatment process. The inspectors were concerned that the licensee may not have adequately addressed operating experience in the design of the original 416SS couplings or the 2009 replacement couplings as required by Appendix B, Criteria III. And the corrective actions taken after the 2009 failure may not have prevented recurrence of this SCAQ as required by Appendix B, Criteria XVI. These concerns will be further evaluated as part of the NRC baseline inspection program, after the final metallurgical results are issued and the licensee root cause evaluation is completed. |
| Site: | Palisades  |
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| Report | IR 05000255/2011012 Section 4OA5 |
| Date counted | Sep 30, 2011 (2011Q3) |
| Type: | URI: |
| cornerstone | Mitigating Systems |
| Identified by: | NRC identified |
| Inspection Procedure: | IP 93812 |
| Inspectors (proximate) | D Passehl J Ellegood J Giessner J Jandovitz N Valos T Taylor D Betancourtj Jandovitza Shaikh P Smagacz |
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Finding - Palisades - IR 05000255/2011012 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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Finding List (Palisades) @ 2011Q3
Self-Identified List (Palisades)
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