SBK-L-09232, Notification of Deviation from MRP-139 Inspection Requirement
| ML093430131 | |
| Person / Time | |
|---|---|
| Site: | Seabrook  |
| Issue date: | 11/23/2009 |
| From: | St.Pierre G NextEra Energy Seabrook |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| MRP-139, SBK-L-09232 | |
| Download: ML093430131 (3) | |
Text
NEXTera November 23, 2009 Docket No. 50-443 SBK-L-09232 U.S. Nuclear Regulatory Commission Attn: Document Control Desk Washington, D.C. 20555 - 0001 Seabrook Station Notification of Deviation from MRP-139 Inspection Requirement
References:
- 1. NEI 03-08, Materials Guidelines Implementation Protocol, Revision 3, Addendum E, April 2008
- 2. MRP-139, "Material Reliability Program: Primary System Piping Butt Weld Inspection and Evaluation Guideline (MRP-139, Revision 1)," EPRI, Palo Alto, CA, 2008 In accordance with Reference 1, NextEra Energy Seabrook, LLC (NextEra) is providing notification of a deviation from MRP-139, Material Reliability Program (Reference 2).
This notification is provided for information only and no response is expected.
The deviation involves the mandatory requirement to perform ultrasonic testing following application of stress improvement to a reactor vessel outlet nozzle Alloy 82/182 weld.
The deviation applies to the outlet nozzle to safe end weld at 158 degrees, which has been mitigated by the Mechanical Stress Improvement Process (MSIP). Specifically, MRP-139, Section 6.7.2, requires that 100% of treated welds shall be volumetrically inspected before return to service. In lieu of this requirement, NextEra will perform an examination for axial and circumferential indications from the inside diameter of the nozzle during refueling outage 14 in the spring of 2011. NextEra's evaluation of this deviation concluded that the deviation meets the same objective and intent, or level of conservatism exhibited by the MRP-139 requirement. The deviation will remain in effect from the fall 2009 refueling outage until the refueling outage in the spring of 2011 when a complete inspection of the inside diameter of the nozzle weld will be performed.
In October 2009, the ten-year In Service Inspection identified an axial indication in the dissimilar metal weld at the reactor outlet nozzle at 158 degrees. A flaw evaluation for the indication determined that the weld could remain in service for at least one 18-month
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NextEra Energy Seabrook, LLC, P.O. Box 300, Lafayette Road, Seabrook, NH 03874
Nuclear Regulatory Commission SBK-L- 09232 / Page 2 operating cycle before repair would be necessary. However, NextEra conservatively mitigated the indication utilizing the MSIP. Because the mitigation was an emergent issue, the activity occurred following refueling and after the reactor was assembled.
Performing a volumetric inspection of the nozzle weld following the MSIP to meet the requirement of MRP-139 would have required disassembling the reactor and removing all fuel assemblies. Such an effort would have required more than 10-days duration and would have resulted in radiation exposure to personnel in excess of 9 man-Rem.
The purpose of the post-MSIP volumetric inspection is to establish a baseline for successive examinations. Follow-on examinations, required by MRP-139, verify that the mitigation has arrested propagation of the indication. However, unlike examinations following repair or replacement by welding or flaw removal, the post-MSIP examination does not provide any acceptance or verification of the mitigation process. Consequently, performing the post-MSIPO inspection in the spring of 2011 with two subsequent follow-on inspections will provide the same level of assurance that the flaw has been arrested as performing the inspection during the 2009 refueling outage.
In summary, an evaluation performed in accordance with ASME Section XI and MRP-
.139 found that the flaw identified during a qualified examination of the inside diameter of the nozzle is acceptable for at least 18-months of operation. Nonetheless, NextEra mitigated the flaw indication with the MSIP to impart a favorable stress profile to the inner surface of the dissimilar metal weld. As a result, performing the post-MSIP volumetric inspection from the inside diameter of the nozzle weld during the spring 2011 refueling outage satisfies the intent of MRP-139.
Consistent with the requirements of NEI 03-08, the justification for this deviation has received an independent review and is in the station corrective action program. The Chief Nuclear Officer and a knowledgeable materials expert independent of NextEra concurred with this deviation.
If you have any questions regarding this information, please contact Mr. Michael O'Keefe, Licensing Manager at (603) 773-7745.
Sincerely, NextEra Energy Seabrook, LLC Gene St. Pierre Vice President North
cc:
S. J. Collins, NRC Region I Administrator D. L. Egan, NRC Project Manager W. J. Raymond, NRC Senior Resident Inspector M. G. Evans, Director, Division of Component Integrity