ML20316A026
| ML20316A026 | |
| Person / Time | |
|---|---|
| Site: | Ginna  |
| Issue date: | 11/11/2020 |
| From: | David Gudger Exelon Generation Co |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| Download: ML20316A026 (6) | |
Text
10 CFR 50.55a November 11, 2020 U.S. Nuclear Regulatory Commission Attn: Document Control Desk Washington, DC 20555-0001 R.E. Ginna Nuclear Power Plant Renewed Facility Operating License No. DPR-18 NRC Docket No. 50-244
Subject:
Proposed Alternative to Use the Successive Inspection Requirements of IWB-2420(c) of the 2017 Edition of ASME Section XI In accordance with 10 CFR 50.55a(z)(1), Exelon Generation Company, LLC (Exelon) is requesting a proposed alternative to the American Society of Mechanical Engineers (ASME)
Boiler and Pressure Vessel Code (B&PV), Section Xl, "Rules for Inservice Inspection of Nuclear Power Plant Components," on the basis that the proposed alternative would provide an acceptable level of quality and safety. Specifically, Exelon is requesting to use the successive inspection requirements of paragraph IWB-2420(c) of the ASME B&PV Code Section XI, 2017 Edition for the 270-degree lower radial support clevis insert in lieu of paragraph IWB-2420(b) of the 2004 Edition and 2013 Edition. This relief request applies to the fifth and sixth ten-year Inservice Inspection (ISI) intervals for the Ginna Nuclear Power Plant.
There are no regulatory commitments in this letter.
Exelon requests approval of this relief request by October 3, 2021.
If you have any questions concerning this letter, please contact Tom Loomis at (610) 765-5510.
Respectfully, David T. Gudger Senior Manager, Licensing Exelon Generation Company, LLC
Attachment:
Relief Request I6R-06 cc: Regional Administrator - NRC Region I NRC Senior Resident Inspector - R.E. Ginna Nuclear Power Plant NRC Project Manager - R.E. Ginna Nuclear Power Plant A. L. Peterson - NYSERDA
Attachment Relief Request I6R-06
10 CFR 50.55a RELIEF REQUEST Revision 0 (Page 1 of 4) 10 CFR 50.55a Relief Request I6R-06 Proposed Alternative to Use the Successive Inspection Requirements of IWB-2420(c) of the 2017 Edition in Accordance with 10 CFR 50.55a(z)(1)
--Alternative Provides Acceptable Level of Quality and Safety--
- 1. ASME Code Component(s) Affected:
Code Class: Class 1
==
Description:==
Core Support Structure*
Examination Category: B-N-3 Item Number: B13.70 Component ID: RPV Core Support Structure
- Specifically, the 270-degree lower radial support clevis insert which is part of the core support structure.
2. Applicable Code Edition and Addenda
PLANT INTERVAL EDITION START END R. E. Ginna Nuclear Fifth 2004 Edition, No Addenda January 1, 2010 December 31, 20191 Power Plant Sixth 2013 Edition January 1, 2020 December 31, 2029 Note 1: The fifth Inservice Inspection (ISI) interval for the Ginna Nuclear Power Plant (Ginna) was extended by approximately 4 months as allowed by Paragraph IWA-2430(d)(2) of the 2004 Edition, No Addenda of ASME Section XI, in order to perform reactor vessel internal inspections for Examination Categories B-N-1, B-N-2, and B-N-3 during the Spring 2020 refueling outage.
This interval extension only applied to Examination Categories B-N-1, B-N-2, and B-N-3.
3. Applicable Code Requirements
IWB-2420(b), Successive Inspections, [2004/2013 Edition] states that If a component is accepted for continued service in accordance with IWB-3132.3 or IWB-3142.4, the areas containing flaws or relevant conditions shall be reexamined during the next three inspection periods listed in the schedule of the inspection program of IWB-2400.
IWB-2420(c), Successive Inspections, [2004 Edition] states that If the reexaminations required by IWB-2420(b) reveal that the flaws or relevant conditions remain essentially unchanged for three successive inspection periods, the component examination schedule may revert to the original schedule of successive inspections.
IWB-2420(c), Successive Inspections, [2013 Edition] states that If the reexaminations required by (b) reveal that the flaws or relevant conditions remain essentially unchanged, or that the flaw growth is within the growth predicted by the analytical evaluation, for three successive inspection periods, then the component examination schedule may revert to the original schedule of successive inspections or the inspection interval defined by the analytical evaluation, whichever is limiting.
IWB-3142.4, Acceptance by Analytical Evaluation, [2004 Edition] states that A component containing relevant conditions is acceptable for continued service if an analytical evaluation
10 CFR 50.55a RELIEF REQUEST Revision 0 (Page 2 of 4) demonstrates the components acceptability. The evaluation analysis and evaluation acceptance criteria shall be specified by the Owner. A component accepted for continued service based on analytical evaluation shall be subsequently examined in accordance with IWB-2420(b) and (c).
IWB-3142.4, Acceptance by Analytical Evaluation, [2013 Edition] states that A component containing relevant conditions is acceptable for continued service if an analytical evaluation demonstrates the components acceptability. The evaluation analysis and evaluation acceptance criteria shall be specified by the Owner. A component accepted for continued service based on analytical evaluation shall be subsequently examined in accordance with IWB-2420(b) and IWB-2420(c).
IWB-2420(c), Successive Inspections, [2017 Edition] states that If a component is accepted for continued service in accordance with IWB-3142.4, successive examinations shall be performed, if determined necessary, based on an evaluation by the Owner. The evaluation shall be documented and shall include the cause of the relevant condition, if known. If the cause of the relevant condition is unknown or if the relevant condition has previously occurred, successive examinations shall be performed during each successive inspection period until the relevant condition remains essentially unchanged from the previous inspection.
4. Reason for Request
Exelon Generation Company, LLC (Exelon) requests the use of the provision of IWB-2420(c) from the 2017 Edition of ASME Section XI which permits successive examinations be performed, if determined necessary, based on an evaluation by the Owner. This provision will be used in lieu of IWB-2420(b) from the 2004 Edition and 2013 Edition of ASME Section XI which requires the area containing relevant conditions to be reexamined during the next three inspection periods, regardless of the evaluation by the Owner. All related requirements of the 2004 or 2013 Edition, as applicable, will be maintained.
The provisions of IWB-2420(c) of the 2017 Edition of ASME Section XI will be used to define the successive inspection requirements, if any, for the 270-degree lower radial support clevis insert that was accepted by analytical evaluation in accordance with IWB-3142.4 of the 2004 Edition of ASME Section XI during the Spring 2020 refueling outage. Use of IWB-2420(c) from the 2017 Edition may prevent the need to perform successive inspections of the 270-degree lower radial support clevis insert which would require a full core offload during the Fall 2021 outage.
Successive inspections of the clevis insert during the sixth Interval, as determined to be required by analytical evaluation, performed in accordance with IWB-3142.4 of the 2004 Edition of ASME Section XI, will be performed in accordance with the requirements of the 2013 Edition of ASME Section XI. The acceptance of the clevis insert during successive inspections performed during the sixth interval will be by analytical evaluation performed in accordance with IWB-3142.4 of the 2013 Edition of ASME Section XI. In this situation, the provisions of IWB-2420(c) of the 2017 Edition of ASME Section XI will be used in lieu of IWB-2420(b) of the 2013 Edition of ASME Section XI to define the successive inspection requirements for the clevis insert.
10 CFR 50.55a RELIEF REQUEST Revision 0 (Page 3 of 4)
5. Proposed Alternative and Basis for Use
During G1R42 (Spring 2020), the 270-degree lower radial support clevis insert (B-N-3, B13.70) was found disengaged from the clevis and radially displaced. The most-likely cause of the clevis insert displacement was determined to be Primary Water Stress Corrosion Cracking (PWSCC) of the clevis bolts. This resulted in a loss of insert retention and a combination of Flow Induced Vibrations (FIV) and differential thermal expansion during plant cooldowns reduced the interference fit allowing the observed radial displacement to occur. This clevis insert as-found condition was accepted for the next operating cycle by analytical evaluation in accordance with IWB-3142.4, 2004 Edition. It was determined that the as-left configuration of the four clevis inserts can maintain the core support function to meet design requirements. This evaluation will be provided as part of the G1R42 OAR-1 as required by IWB-3144(b).
This exam was performed as part of the fifth interval which complied with the 2004 Edition, no Addenda. The fifth ISI interval for Ginna was extended by approximately 4 months as allowed by Paragraph IWA-2430(d)(2) of the 2004 Edition, No Addenda of ASME Section XI, in order to perform reactor vessel internal inspections for Examination Categories B-N-1, B-N-2, and B-N-3 during the Spring 2020 refueling outage. This interval extension only applied to Examination Categories B-N-1, B-N-2, and B-N-3.
IWB-2420(b) of the 2004 Edition of ASME Section XI requires if a component is accepted for continued service in accordance with IWB-3142.4, the areas containing relevant conditions shall be reexamined during the next three inspection periods listed in the schedule of the Inspection Program of IWB-2400. Reexamination of the 270-degree lower radial support clevis insert in accordance with IWB-2420(b) of the 2004 Edition of ASME Section XI would require a full core offload and removal of the core barrel resulting in an extended outage and additional dose each of the next three inspection periods. Implementing IWB-2420(c) of the 2017 Edition of ASME Section XI may prevent the need to perform successive inspections provided acceptable evaluation results as required by the ASME Code are obtained to justify continued operation.
Exelon proposes the use of IWB-2420(c) of the 2017 Edition of ASME Section XI in lieu of IWB-2420(b) of the 2004 Edition of ASME Section XI to define the successive inspection requirements of the 270-degree lower radial support clevis insert that was accepted by analytical evaluation during the Spring 2020 outage for one operating cycle. This proposed alternative will be applied only to the successive inspections of the clevis insert and will remain in effect for the remainder of the sixth interval. Ginna is currently performing an analytical evaluation in accordance with IWB-3142.4, Acceptance by Analytical Evaluation, 2004 Edition, to determine if continued operation beyond the current operating cycle is permitted. This evaluation will address the successive examination requirements of IWB-2420(c) of the 2017 Edition of ASME Section XI as described in this proposed alternative. This evaluation will be provided to the NRC as required by IWB-3144(b).
Exelon will perform successive inspections in accordance with IWB-2420(c) of the 2017 Edition as determined necessary by an analytical evaluation performed in accordance with IWB-3142.4 of the 2004 Edition of ASME Section XI. Successive inspections, if necessary, will be performed during the sixth interval in accordance with the 2013 Edition of ASME Section XI.
The continued acceptance of as-found conditions for any successive inspections required during the sixth interval will be performed in accordance with IWB-3142.4 of the 2013 Edition of ASME Section XI. Exelon proposes the use of IWB-2420(c) of the 2017 Edition of ASME
10 CFR 50.55a RELIEF REQUEST Revision 0 (Page 4 of 4)
Section XI in lieu of IWB-2420(b) of the 2013 Edition of ASME Section XI to define the continued successive inspections of the clevis insert for the remainder of the sixth Interval.
The 2017 Edition of ASME Section XI has been approved for use by the NRC in 10 CFR 50.55a, Codes and standards. There are no NRC limitations, modifications, or conditions placed on paragraph IWB-2420(c) of the 2017 Edition of ASME Section XI in 10 CFR 50.55a.
Based on the above, use of IWB-2420(c) of the 2017 Edition of ASME Section XI in lieu of IWB-2420(b) of the 2004 and 2013 Editions will provide an acceptable level of quality and safety in accordance with 10 CFR 50.55a(z)(1).
6. Duration of Proposed Alternative
The proposed alternative will remain in effect for the remainder of the sixth Inservice Inspection Interval.
- 7. Precedent:
None