RS-14-044, Proposed Alternative to Utilize Code Case N-786, Alternative Requirements for Sleeve Reinforcement of Class 2 and 3 Moderate-Energy Carbon Steel Piping Section XI, Division
| ML14119A289 | |
| Person / Time | |
|---|---|
| Site: | Calvert Cliffs, Dresden, Peach Bottom, Nine Mile Point, Oyster Creek, Byron, Three Mile Island, Braidwood, Limerick, Ginna, Clinton, Quad Cities, LaSalle |
| Issue date: | 04/28/2014 |
| From: | Jim Barstow Exelon Generation Co |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| RS-14-044, RS-14-146, TMI-14-064 | |
| Download: ML14119A289 (10) | |
Text
10 CFR 50.55a RS-14-146 RA-14-044 TMI-14-064 April 28, 2014 U.S. Nuclear Regulatory Commission Attn: Document Control Desk Washington, DC 20555-0001 Braidwood Station, Units 1 and 2 Facility Operating License Nos. NPF-72 and NPF-77 NRC Docket Nos. STN 50-456 and STN 50-457 Byron Station, Units 1 and 2 Facility Operating License Nos. NPF-37 and NPF-66 NRC Docket Nos. STN 50-454 and STN 50-455 Clinton Power Station, Unit 1 Facility Operating License No. NPF-62 NRC Docket No. 50-461 Dresden Nuclear Power Station, Units 2 and 3 Renewed Facility Operating License Nos. DPR-19 and DPR-25 NRC Docket Nos. 50-237 and 50-249 LaSalle County Station, Units 1 and 2 Facility Operating License Nos. NPF-11 and NPF-18 NRC Docket Nos. 50-373 and 50-374 Limerick Generating Station, Units 1 and 2 Facility Operating License Nos. NPF-39 and NPF-85 NRC Docket Nos. 50-352 and 50-353 Oyster Creek Nuclear Generating Station Renewed Facility Operating License No. DPR-16 NRC Docket No. 50-219 Peach Bottom Atomic Power Station, Units 2 and 3 Renewed Facility Operating License Nos. DPR-44 and DPR-56 NRC Docket Nos. 50-277 and 50-278 Quad Cities Nuclear Power Station, Units 1 and 2 Renewed Facility Operating License Nos. DPR-29 and DPR-30 NRC Docket Nos. 50-254 and 50-265
U.S. Nuclear Regulatory Commission Response to Request for Additional Information Proposed Alternative to Utilize Code Case N-786 April 28, 2014 Page 2 Three Mile Island Nuclear Station, Unit 1 Renewed Facility Operating License No. DPR-50 NRC Docket No. 50-289 Calvert Cliffs Nuclear Power Plant, Units 1 and 2 Renewed Facility Operating License Nos. DPR-53 and DPR-69 NRC Docket Nos. 50-317 and 50-318 Nine Mile Point Nuclear Station, Units 1 and 2 Renewed Facility Operating License Nos. DPR-63 and NPF-69 NRC Docket Nos. 50-220 and 50-410 R. E. Ginna Nuclear Power Plant Renewed Facility Operating License No. DPR-18 NRC Docket No. 50-244
Subject:
Proposed Alternative to Utilize Code Case N-786, .. Alternative Requirements for Sleeve Reinforcement of Class 2 and 3 Moderate-Energy Carbon Steel Piping Section XI, Division 1..
References:
- 1) Letter from M. D. Jesse (Exelon Generation Company, LLC) to U.S.
Nuclear Regulatory Commission, .. Proposed Alternative to Utilize Code Case N-786, .. Alternative Requirements for Sleeve Reinforcement of Class 2 and 3 Moderate-Energy Carbon Steel Piping Section XI, Division 1, .. dated February 27, 2013
- 2) E-mail from J. Wiebe (U.S. Nuclear Regulatory Commission) toT.
Loomis (Exelon Generation Company, LLC), .. Preliminary RAI for Proposed Alternative to Use Code Case N-786, .. dated April 30, 2013
- 3) Letter from J. Barstow (Exelon Generation Company, LLC) to U.S.
Nuclear Regulatory Commission, .. Response to Request for Additional Information- Proposed Alternative to Utilize Code Case N-786,
.. Alternative Requirements for Sleeve Reinforcement of Class 2 and 3 Moderate-Energy Carbon Steel Piping Section XI, Division 1,.. dated June 24, 2013
- 4) E-mail from J. Wiebe (U.S. Nuclear Regulatory Commission) toT.
Loomis (Exelon Generation Company, LLC), .. Preliminary Additional RAI Questions Regarding Use of Code Case N-786, .. dated November 6, 2013
- 5) Letter from J. Barstow (Exelon Generation Company, LLC) to U.S.
Nuclear Regulatory Commission, .. Response to Request for Additional Information - Proposed Alternative to Utilize Code Case N-786,
.. Alternative Requirements for Sleeve Reinforcement of Class 2 and 3 Moderate-Energy Carbon Steel Piping Section XI, Division 1,.. dated December 12, 2013
U.S. Nuclear Regulatory Commission Response to Request for Additional Information Proposed Alternative to Utilize Code Case N-786 April 28, 2014 Page 3 In the Reference 1 letter, Exelon Generation Company, LLC (Exelon) requested a proposed alternative to the American Society of Mechanical Engineers (ASME) Boiler and 11 Pressure Vessel Code,Section XI, Rules for lnservice Inspection of Nuclear Power Plant Components,~~ on the basis that compliance with the specified requirements would result in hardship or unusual difficulty without a compensating increase in the level of quality and safety. In the Reference 2 and 4 e-mails, the U.S. Nuclear Regulatory Commission requested additional information. References 3 and 5 were our responses to those requests.
Based on further review, the relief request has been revised to include additional conditions for the full-structural Type B reinforcing sleeves. In particular, as discussed in the relief request, for completed full-structural Type B reinforcing sleeves, thickness monitoring inspections will be performed at a minimum of every refueling outage for the life of the repair. These new changes are included in the attached relief request as identified by the revision bars.
Additionally, due to the recent transfer of the operating licenses for the above nuclear units (Calvert Cliffs Nuclear Power Plant, Units 1 and 2, R.E. Ginna Nuclear Power Plant, Nine Mile Point Nuclear Station, Units 1 and 2) from Constellation Energy Nuclear Group, LLC to Exelon Generation Company, LLC, these stations have been added to this relief request. All conditions discussed in this relief request will be applied to these stations.
There are no commitments contained in this submittal.
If you have any questions, please contact Tom Loomis at 610-765-5510.
Respectfully, James Barstow Director - Licensing and Regulatory Affairs Exelon Generation Company, LLC Attachments: Revised Relief Request (Revision 3) cc: Regional Administrator- NRC Region I Regional Administrator- NRC Region Ill NRC Senior Resident Inspector- Braidwood Station NRC Senior Resident Inspector- Byron Station NRC Senior Resident Inspector- Calvert Cliffs Nuclear Power Plant NRC Senior Resident Inspector - Clinton Power Station NRC Senior Resident Inspector- Dresden Nuclear Power Station NRC Senior Resident Inspector- R.E. Ginna Nuclear Power Plant NRC Senior Resident Inspector- LaSalle County Station NRC Senior Resident Inspector - Limerick Generating Station
U.S. Nuclear Regulatory Commission Response to Request for Additional Information Proposed Alternative to Utilize Code Case N-786 April28, 2014 Page 4 cc (cont'd)
NRC Senior Resident Inspector - Nine Mile Point Nuclear Station NRC Senior Resident Inspector- Oyster Creek Nuclear Generating Station NRC Senior Resident Inspector- Peach Bottom Atomic Power Station NRC Senior Resident Inspector- Quad Cities Nuclear Power Station NRC Senior Resident Inspector- Three Mile Island Nuclear Station, Unit 1 NRC Project Manager - Braidwood Station NRC Project Manager - Byron Station NRC Project Manager - Calvert Cliffs Nuclear Power Plant NRC Project Manager- Clinton Power Station NRC Project Manager - Dresden Nuclear Power Station NRC Project Manager- R.E. Ginna Nuclear Power Plant NRC Project Manager - LaSalle County Station NRC Project Manager - Limerick Generating Station NRC Project Manager - Nine Mile Point Nuclear Station NRC Project Manager- Oyster Creek Nuclear Generating Station NRC Project Manager- Peach Bottom Atomic Power Station NRC Project Manager- Quad Cities Nuclear Power Station NRC Project Manager- Three Mile Island Nuclear Station, Unit 1
Attachment Revised Relief Request (Revision 3)
10 CFR 50.55a Relief Request (Revision 3)
Page 1 of 5 Request to Use Code Case N-786 in Accordance with 10 CFR 50.55a(a)(3)(ii)
- 1. ASME Code Component(s) Affected:
All ASME Class 2 and 3 moderate energy (i.e., less than or equal to 200°F (93°C) and less than or equal to 275 psig (1.9 MPa) maximum operating conditions) carbon steel piping systems.
2. Applicable Code Edition and Addenda
PLANT INTERVAL EDITION START END Braidwood Station, 2001 Edition, through 2003 July 29, 2008 July 28, 2018 Third Units 1 and 2 Addenda October 17, 2008 October 16, 2018 Byron Station, 2001 Edition, through 2003 Third January 16, 2006 July 15, 2016 Units 1 and 2 Addenda Calvert Cliffs Nuclear Power Plant, Units 1 and Fourth 2004 Edition October 10, 2009 June 30, 2019 2
Clinton Power Station, Third 2004 Edition July 1, 2010 June 30, 2020 Unit 1 Dresden Nuclear Power 2007 Edition, through 2008 Fifth January 20, 2013 January 19, 2023 Station, Units 2 and 3 Addenda R. E. Ginna Nuclear Fifth 2004 Edition January 1, 2010 December 31, 2019 Power Plant LaSalle County Stations, 2001 Edition, through 2003 Third October 1, 2007 September 30, 2017 Units 1 and 2 Addenda Limerick Generating 2001 Edition, through 2003 Third February 1, 2007 January 31, 2017 Station, Units 1 and 2 Addenda Nine Mile Point Nuclear Fourth 2004 Edition August23,2009 August22,2019 Station, Unit 1 Nine Mile Point Nuclear Third 2004 Edition April 5, 2008 April 4, 2018 Station, Unit 2 Oyster Creek Nuclear 2007 Edition, through 2008 Fifth January 15, 2013 January 14, 2023 Generating Station Addenda Peach Bottom Atomic 2001 Edition, through 2003 Power Station, Fourth November 5, 2008 November 4, 2018 Addenda Units 2 and 3 Quad Cities Nuclear 2007 Edition, through 2008 Power Station, Fifth April 2, 2013 April 1, 2023 Addenda Units 1 and 2 Three Mile Island Nuclear Fourth 2004 Edition April 20, 2011 April 19, 2022 Station, Unit 1
10 CFR 50.55a Relief Request (Revision 3)
Page 2 of 5
3. Applicable Code Requirement
ASME Code,Section XI, IWA-4400 of 2001 Edition through 2003 Addenda, 2004 Edition, and 2007 Edition through 2008 Addenda provides requirements for welding, brazing, metal removal, and installation of repair/replacement activities.
4. Reason for Request
In accordance with 10 CFR 50.55a(a)(3)(ii), Exelon Generation Company, LLC (Exelon) is requesting proposed alternatives from the requirement for replacement or internal weld repair of wall thinning conditions resulting from degradation in Class 2 and Class 3 moderate energy carbon steel piping systems in accordance with IWA-4000. Such degradation may be the result of mechanisms such as localized erosion, corrosion, cavitation, and pitting, but excluded are conditions involving any form of cracking. IWA-4000 requires repair or replacement in accordance with the Owner's Requirements and the original or later Construction Code.
One reason for this request is to permit installation of technically sound temporary repairs, in the form of Type A or partial-structural Type B reinforcing sleeves, to provide adequate time for evaluation, design, material procurement, planning and scheduling of appropriate permanent repair or replacement of the defective piping, considering the impact on system availability, maintenance rule applicability, and availability of replacement materials.
The other reason for this request is to permit installation of long-term repairs, in the form of full-structural Type B reinforcing sleeves, for locally degraded portions of piping systems. The design, construction, and inservice monitoring of such sleeves provide a technically sound equivalent replacement for the segment of degraded piping that is encompassed.
- 5. Proposed Alternative and Basis for Use:
Exelon proposes to implement the requirements of ASME Code Case N-786, "Alternative Requirements for Sleeve Reinforcement of Class 2 and 3 Moderate-Energy Carbon Steel Piping Section XI, Division 1," for repair of degradation in Class 2 and 3 moderate energy carbon steel piping systems resulting from mechanisms such as localized erosion, corrosion, cavitation, or pitting, but excluding conditions involving any form of cracking. These types of defects are typically identified by small leaks in the piping system or by pre-emptive non-code required examinations performed to monitor the degradation mechanisms. Code Case N-786, which is included as part of this relief request, is attached.
This code case invokes the design requirements of the original Construction Code or ASME Code, Section Ill. Reconciliation and use of editions and addenda of ASME Section Ill will be in accordance with ASME Section XI, IWA-4220, and only editions and addenda of ASME Section Ill that have been accepted by 10 CFR 50.55a may be used. The Code of Record for the specific 10-year lSI interval at each nuclear unit as identified under Section 2 above, will be used when applying the various IWA paragraphs of Section XI unless specific regulatory relief to use other editions or addenda is approved.
The alternative repair technique described in Code Case N-786 involves the application of Type A and Type B full encirclement sleeve halves welded together with full penetration longitudinal seam welds to reinforce structural integrity in the degraded area. In the case of Type B reinforcing sleeves, the ends are also welded to the piping in order to restore pressure integrity.
10 CFR 50.55a Relief Request (Revision 3)
Page 3 of 5 This repair technique will be utilized when it is determined that this repair method is suitable for the particular defect or degradation being resolved without flaw removal. Use of this repair method will be limited to pipe and fittings; as a result the following condition shall apply to the application of Code Case N-786:
Reinforcing sleeves may not be applied to pumps, valves. expansion joints, vessels, heat exchangers, tubing, or flanges; and may not be applied over flanged joints. socket welded or threaded joints, or branch connection welds.
The Code Case requires that the cause of the degradation be determined and that the extent and rate of degradation in the piping be evaluated to ensure that there are no other unacceptable locations within the surrounding area that could affect the integrity of the repaired piping. Surrounding areas showing signs of degradation shall be identified and included in the Owner's plan for thickness monitoring for full-structural reinforcing sleeves. The area of evaluation will be dependent on the degradation mechanism present. but shall extend at least 0.75-.J RTr,:,rr1 beyond the edge of any sleeve attachment weld. If the cause of the degradation is not determined, the maximum permitted service life of any reinforcing sleeve shall be the time until the next refueling outage. In addition, the following condition shall apply to the application of Code Case N-786:
The initial degradation rate selected for design of all sleeves shall be equal to or greater than two (2) times the maximum rate observed at the location of the repair. If the degradation rate for that location is unknown, four (4) times the estimated maximum degradation rate for that or a similar system at the same plant site for the same degradation mechanism shall be applied. If both the degradation rate for that location and the cause of the degradation are not conclusively determined, four (4) times the maximum degradation rate observed for all degradation mechanisms for that or a similar system at the same plant site shall be applied.
"Full-structural Type B" means that the sleeve and attachment welds alone maintain full capability to withstand structural (mechanical) and pressure loading for which the piping is presently designed without need for additional support or reinforcement, and without reliance on any piping that is encased by the sleeve. Type A and partial-structural Type B sleeves rely on the encased underlying piping to provide some structural (mechanical) and/or pressure retaining integrity.
Type B reinforcing sleeves may be applied to leaking systems by installing a gasket or sealant between the sleeve and the pipe as permitted by the Code Case, and then clamping the reinforcing sleeve halves to the piping prior to welding. Residual moisture is then removed by heating prior to welding. If welding of any type of sleeve occurs on a wet surface, the maximum permitted life of the sleeve shall be the time until the next refueling outage.
The Code Case requires that the Owner shall prepare and implement a plan for thickness monitoring by inspection of full-structural reinforcing sleeves and their attachment welds. To accomplish this, a baseline thickness examination will be performed for completed full-structural Type B reinforcing sleeves, partial penetration attachment welds, and surrounding areas, followed by similar thickness monitoring inspections performed at a minimum of every refueling outage for the life of the repair. More frequent thickness monitoring examinations will be scheduled based on the maximum degradation rates observed during these inspections, such
10 CFR 50.55a Relief Request (Revision 3)
Page 4 of 5 that the required design thicknesses will not be infringed upon before each subsequently scheduled thickness monitoring examination.
Partial-structural Type B reinforcing sleeves and Type A reinforcing sleeves completely encompass the degraded areas. These sleeves are designed to accommodate predicted maximum degradation and must be removed at the next refueling outage. Accordingly, the Code Case does not require inservice monitoring for these sleeves. However, because of NRC concerns discussed in the May 10, 2012, NRC Safety Evaluation Report for the Exelon Generation Company, LLC, sites concerning the approval to apply Code Case N-789 (ML12121A637), the following condition shall apply to the application of Code Case N-786:
Type A reinforcing sleeves and partial-structural Type B reinforcing sleeves shall be visually observed at least once per month to monitor for evidence of leakage. If the areas containing these sleeves are not accessible for direct observation, then monitoring will be accomplished by visual assessment of surrounding areas or ground surface areas above such sleeves on buried piping, or monitoring of leakage collection systems, if available.
When used on buried piping, the area of full-structural Type B reinforcing sleeves will need to be physically accessible for the required examinations, which could necessitate installation of removable barriers at the repair location in lieu of backfilling the pipe at that location. For Type A and partial-structural Type B reinforcing sleeves installed on buried piping, the monitoring will be based on visual assessment as discussed above.
Type A reinforcing sleeves and partial-structural Type B reinforcing sleeves shall have a maximum permitted service life of the time until the next refueling outage, when *a permanent repair or replacement must be performed. Neither the Type A nor the partial-structural Type B reinforcing sleeve may remain in service beyond the end of the next refueling outage after they are installed, unless specific regulatory relief is obtained. This means that if such a repair is performed in mid-cycle (e.g., one month before the scheduled refueling outage) the reinforcing sleeve would be removed no later than the upcoming refueling outage (e.g., in one month) unless specific regulatory relief is obtained. Even if removal during the next scheduled refueling outage becomes challenging (e.g., it is installed on a system required to be functional during the refueling outage), it would still need to be removed when the system is not required to be functional and prior to the conclusion of the next scheduled refueling outage after it was installed.
A similar situation exists with common cooling lines that require a dual unit outage in order to remove them from service. Unless a full-structural Type B reinforcing sleeve is installed, specific regulatory approval would need to be obtained in order to defer removal of a Type A or partial-structural Type B reinforcing sleeve beyond the next upcoming refueling outage of either unit.
Full-structural Type B reinforcing sleeves will be removed and an IWA-4000 repair or replacement will be performed prior to the time that inservice monitoring indicates that pressure integrity (leak tightness) or structural integrity could be impaired based on measured degradation between monitoring activities. Additional requirements for design, installation, examination (including volumetric examination in accordance with NC-5200 and NC-5300, or ND-5200 and ND-5300), pressure testing, and inservice examination of reinforcing sleeves are provided in Code Case N-786, with the following additional condition:
10 CFR 50.55a Relief Request (Revision 3)
Page 5 of 5 Branch connections may be installed on reinforcing sleeves only for filling or venting purposes during installation or leakage testing of the sleeve. and shall be limited to Nominal Pipe Size (NPS) 1 or smaller in size.
All other ASME Section XI requirements for which relief was not specifically requested and authorized by the NRC staff will remain applicable including third party review by the Authorized Nuclear lnservice Inspector.
Performing code repair/replacement in lieu of implementing this Relief Request would in some cases necessitate extending Technical Specification Actions to install a permanent repair/replacement, putting the plant at higher safety risks than warranted compared with the short time necessary to install a technically sound sleeve repair. Without the use of this Code Case in some situations. it may be necessary to shut the plant down in order to perform a code repair/replacement activity; however. this results in an unnecessary plant transient and the loss of safety system availability as compared to maintaining the plant online.
Implementing this Relief Request during refueling outages will enable a greater number of scheduled corrosion inspections during the outages. The ability to install non-intrusive repair sleeves rather than scheduling contingency plans for piping replacement. will enable longer corrosion inspection windows. increased scope of inspection. and improved overall plant safety.
Based on the above, the use of Code Case N-786 for full-structural Type B reinforcing sleeves and for Type A and partial-structural Type B reinforcing sleeves will apply when compliance with the specified Code requirements of ASME Section XI would result in hardship or unusual difficulty without a compensating increase in the level of quality and safety.
Code Case N-786 was approved by the ASME Board on Nuclear Codes and Standards on March 24, 2011; however, it has not been incorporated into NRC Regulatory Guide 1.147 11 11 1nservice Inspection Code Case Acceptability, ASME Section XI, Division 1, and thus is not available for application at nuclear power plants without specific NRC approval. Therefore, Exelon requests use of the alternative repair techniques described in the Code Case via this relief request.
- 6. Duration of Proposed Alternative:
The proposed alternative is for use of the Code Case for the remainder of each plant's 10-year inspection interval as specified in Section 2. Installation of reinforcing sleeves in accordance with this request cannot take place after the end of the 10-year lSI interval for the unit. Any Type A and partial-structural Type B reinforcing sleeves installed before the end of the 10-year inservice inspection interval will be removed during the next refueling outage, even if that refueling outage occurs after the end of the 10-year lSI interval.
- 7. Precedent:
A similar Exelon relief request, for Code Case N-789 (Reinforcing Pads for Class 2 and Class 3 Moderate Energy Raw Water Systems) was approved by NRC Safety Evaluation dated May 10, 2012, ADAMS Accession No. ML12121A637.