ML23019A348

Issuance of Relief Request No. SC-I5R-221 for the Alternative Repair for Service Water System Piping

ML23019A348
Person / Time
Site:	Salem
Issue date:	02/02/2023
From:	Hipolito Gonzalez Plant Licensing Branch 1
To:	Carr E Public Service Enterprise Group
Kim J
References
EPID L-2022-LLR-0040
Download: ML23019A348 (10)

Text

February 2, 2023 Mr. Eric Carr President and Chief Nuclear Officer PSEG Nuclear LLC - N09 P.O. Box 236 Hancocks Bridge, NJ 08038

SUBJECT:

SALEM NUCLEAR GENERATING STATION, UNITS 1 AND 2 - PROPOSED ALTERNATIVE TO THE ASME CODE REQUIREMENTS FOR DEFECT REMOVAL IN BURIED SERVICE WATER PIPING (EPID L-2022-LLR-0040)

Dear Mr. Carr:

By letter dated April 7, 2022, (Agencywide Documents Access and Management System (ADAMS) Accession No. ML22097A186), PSEG Nuclear LLC (PSEG, the licensee) proposed an alternative (Request for Relief SC-I5R-221) to the requirements of the American Society of Mechanical Engineers Boiler and Pressure Vessel Code (ASME Code),Section XI, IWA-4422.1 and Title 10 of the Code of Federal Regulations (10 CFR) 50.55a(b)(2)(xxv), at Salem Generating Station, Units 1 and 2 (Salem 1 and 2).

Specifically, pursuant to Title 10 of the Code of Federal Regulations (10 CFR) 50.55a(z)(2), the licensee requested to implement a mechanical repair using a WEKO seal with structural backing plate to restore the pressure boundary integrity of degraded bell and spigot joints in the buried portions of service water (SW) system piping in lieu of the defect removal requirements in the ASME Code,Section XI, Subparagraph IWA-4422.1. The NRC staff concludes that the proposed alternative to install a WEKO seal with structural backing plate to restore the pressure boundary integrity of degraded bell and spigot joints in the SW supply and discharge headers acceptable for contingency planning if degraded bell and spigot joints are found during the fifth inservice inspection interval at Salem 1 and 2. The licensee has determined that performing an ASME Code-compliant repair/replacement on the degraded portion of SW piping in accordance with ASME Code,Section XI, IWA-4000 represents a hardship or unusual difficulty without a compensating increase in the level of quality and safety. In addition, the NRC concludes that the installed WEKO seal with structural backing plate is a permanent repair for the licensed life of the plant since the repair provides an acceptable level of quality and safety based on the material used, inspections performed during installation, stress analysis and inservice inspections to be performed.

Accordingly, the NRC staff concludes that the licensee has adequately addressed all of the regulatory requirements set forth in 10 CFR 50.55a(z)(2). Therefore, the NRC authorizes the use of the proposed alternative in Request for Relief SC-I5R-221 for the fifth 10-year ISI interval at Salem 1 and 2. Once the alternative repair is installed during the fifth 10-year lSI interval, the installed alternative may remain in place for the life of the plant. Should the licensee desire to install the alternative during a subsequent 10-year lSI interval, the licensee must seek authorization from the NRC staff for that interval.

E. Carr All other requirements of the ASME Code,Section XI for which an alternative was not specifically requested and approved remain applicable, including third party review by the Authorized Nuclear Inservice Inspector.

If you have any questions, please contact the Salem Project Manager, James Kim, at 301-415-4125 or by email to James.Kim@nrc.gov.

Sincerely, Hipólito J. González, Chief Plant Licensing Branch I Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket Nos. 50-272 and 50-311

Enclosure:

Safety Evaluation cc: Listserv Hipolito J.

Gonzalez Digitally signed by Hipolito J. Gonzalez Date: 2023.02.02 18:13:15 -05'00'

Enclosure SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION PROPOSED ALTERNATIVE TO ASME CODE REQUIREMENTS FOR DEFECT REMOVAL IN SERVICE WATER BURIED PIPING PSEG NUCLEAR LLC CONSTELLATION ENERGY GENERATION, LLC SALEM NUCLEAR GENERATING STATION, UNITS 1 AND 2 DOCKET NOS. 50-272 AND 50-311

1.0 INTRODUCTION

By letter dated April 7, 2022, (Agencywide Documents Access and Management System (ADAMS) Accession No. ML22097A186), PSEG Nuclear LLC (PSEG, the licensee) submitted request for relief SC-I5R-221, which proposed an alternative to the requirements of the American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code (ASME Code),Section XI, Rules for Inservice Inspection of Nuclear Power Plant Components, for the repair of buried portions of the service water system piping at Salem Nuclear Generating Station, Units 1 and 2 (Salem 1 and 2). Specifically, pursuant to Title 10 of the Code of Federal Regulations (10 CFR) 50.55a(z)(2), the licensee requested to implement a mechanical repair using a WEKO seal with structural backing plate to restore the pressure boundary integrity of degraded bell and spigot joints in the buried portions of service water (SW) system piping in lieu of the defect removal requirements in the ASME Code,Section XI, Subparagraph IWA-4422.1.

2.0 REGULATORY EVALUATION

Adherence to Section XI of the ASME Code is mandated by 10 CFR 50.55a(g)(4), which states, in part, that ASME Code Class 1, 2, and 3 components must meet the requirements, except the design and access provisions and the pre-service examination requirements, set forth in the ASME Code,Section XI.

Paragraph 50.55a(z) of 10 CFR states, in part, that alternatives to the requirements of 10 CFR 50.55a(b)-(h) may be used, when authorized by the Director, Office of Nuclear Reactor Regulation, if (1) the proposed alternatives would provide an acceptable level of quality and safety or (2) compliance with the specified requirements would result in hardship or unusual difficulty without a compensating increase in the level of quality and safety. The licensee has submitted the request on the basis that compliance with the specified requirements of 10 CFR 50.55a would result in hardship or unusual difficulty without a compensating increase in the level of quality and safety.

3.0 TECHNICAL EVALUATION

3.1 ASME Code Component(s) Affected The ASME Code,Section III, Class 3 buried portions of the 11, 12, 21, and 22 nuclear SW supply and discharge header at Salem 1 and 2 are affected. The SW design pressure and temperature are 200 psig and 160°F, respectively. The buried SW piping at Salem 1 and 2 consists of 24-inch internal diameter concrete piping with an integral carbon steel core. The pre-stressed concrete cylinder pipe (PCCP) segments with steel cylinder pre-stressed with wire are connected to each other with bell and spigot joints to provide adequate flexibility (extensibility and articulation) to accommodate pipe movement during operation and design basis scenarios. Some locations would only have one pre-stressed pipe that connects to another component (e.g., elbows, tees, and flange adapters) that are not pre-stressed, and are referred as PCCP-Specials.

Axial piping loads are carried by a series of harness bolts which span the bell and spigot joints between piping segments. Harness bolts range from a few feet in length up to 48 feet in length, depending on the pipe configuration. Long harness bolts may consist of up to three sections of 2-inch diameter threaded rod joined together by couplings. It is noted that the bell housing is credited with the safety function of carrying the axial piping loads due to normal operating and seismic conditions. As described below, under certain conditions addressed by this alternative, the safety function of carrying axial piping loads will shift from the bell housing to the harness bolts.

3.2

Applicable Code Edition and Addenda

The Code of record for the fifth 10-year ISI interval at Salem 1 and 2 is the 2013 Edition of the ASME Code,Section XI. The fifth 10-year ISI interval is currently scheduled to end on December 31, 2030. American Water Works Association (AWWA) C301-64 is the original construction code for the buried SW piping at Salem 1 and 2 and is designated an ASME Code Class 3 system.

3.3 Applicable Code Requirements For ASME Code,Section III, Class 3 components, the repair/replacement activity, and reexamination shall comply with the requirements of Article IWA-4000 of ASME Code,Section XI. ASME Code,Section XI, Article IWA-4422.1 requires that defects be removed in accordance with IWA-4411, IWA-4412, IWA-4461, or IWA-4462.

3.4 Reason for request The licensee found degraded bell and spigot joints in the SW supply and discharge headers during previous inspections performed under the preventative maintenance program and in accordance with Generic Letter (GL) 89-13, Service Water Problems Affecting Safety Related Equipment. The original construction code for the buried SW system does not provide an appropriate repair for the degraded bell and spigot joints other than to excavate and replace the components. These previous degraded SW system bell and spigot joints (9 total) were repaired using a mechanical repair, WEKO seal with structural backing plate (WEKO seal), installed on the inside diameter of the piping to restore the pressure boundary integrity in the SW supply and discharge headers that was approved by NRC Letter, Salem Nuclear Generating Station, Units 1 and 2 - Safety Evaluation of Relief Request No. SC-I4R-133 for the Alternative Repair for Service Water System Piping (TAC Nos. MF1875 and MF1376), dated April 8, 2014 (ML14097A029). In addition, all other bell and spigot joints in the SW supply and return headers had WEKO seals without structural backing installed as a preventative measure. To date all WEKO seals installed have not leaked or exhibited degradation. This alternative repair was approved by the NRC staff for use during the fourth 10-year ISI interval at Salem 1 and 2. The licensee requests to use this alternative repair (WEKO seal with structural backing) as a contingency if degraded bell and spigot joints (including previously installed WEKO seals) are found by inspections performed during the fifth 10-year ISI interval at Salem 1 and 2 for the SW supply and discharge headers.

Due to the overlapping pipe segment design, replacement of the degraded joint is not possible with removing the entire system or would require cutting piping segments and redesigning the system to include flanged joints. In addition, the SW piping is buried 8 feet below grade and would require a large excavation that would uncover other adjacent piping that could be damaged and are necessary to be in service. In addition, sections of the SW piping that are located under the Independent Spent Fuel Storage Installation (ISFSI) pads and the SW accumulator tank buildings would require excavation of these sites with potential damage and adverse effects to the ISFSI and accumulator tank buildings.

This proposed alternative has been developed because repair/replacement options that would involve removing the degraded portions of piping in accordance with IWA-4422.1 creates a hardship or unusual difficulty without a compensating increase in the level of quality and safety.

3.5 Alternative and Basis for Use The licensee has requested to perform mechanical repairs (WEKO seal) of SW system bell and spigot joints that are found degraded during the fifth 10-year ISI interval at Salem 1 and 2 as a contingency. The WEKO seal repair will be installed on joints that are not water-tight during their 36-month physical inspection (air leakage testing). The WEKO seal repair is performed on the inside diameter of the piping but leaves the degraded bell and spigot joint in place while the WEKO seal provides the pressure boundary and structural integrity of the ASME Code piping.

The WEKO seal repair is designed to the original construction code and Section III of the ASME Code.

The WEKO seal consists of a 316 stainless steel backing plate centered over the joint gap which is then covered by an ethylene propylene diene monomer (EPDM) double-wide rubber seal. Two 2-inch wide, 1/8 inch thick radially expanding retaining bands are installed at each end of the seal. The outer set of retaining bands, which are forced against the seal using a hydraulic expander, compress the seal into the concrete core while the inner set of bands compresses the seal and steel sleeve into the core. This design allows for both radial and axial growth in the pipe. The WEKO seal repair provides an alternate load path to ensure structural adequacy of the repaired pipe in addition to eliminating additional degradation or expansion of the degraded joint by preventing exposure to the SW environment. The licensee also provided specific information regarding the design, installation, examination, testing and monitoring of the WEKO seal to be installed as a permanent repair. The WEKO seal repair consists of the following:

1. Identify degraded piping joints by visual inspection.

2. Clean the joint and quantify degradation by inspection of that portion of the bell housing which is accessible from the ID of the pipe using nondestructive examination techniques.

3. Categorize the repair based on the thickness of the bell housing:

a. Category A - Bell housing thickness greater than the minimum wall thickness of 0.1 inches. All code requirements met.

b. Category B - Bell housing thickness greater than 0.042 inches but less than 0.1 inches. ASME Code requirements for axial loads are met. ASME Code requirements for circumferential loads are not met. Repair the joint using the WEKO seal.

c. Category C - Bell housing thickness less than 0.042 inches. ASME Code requirements for axial and circumferential loads are not met. Repair the joint using the WEKO seal.

4. For Category A and B repairs (WEKO seal installation):

a. Apply sealant in degraded joint.

b. Apply coating to the sealant.

c. Install stainless steel backing plate.

d. Install rubber seal material.

e. Install 4 AL6XN retaining rings.

5. For Category C repairs only (in addition to the seal installation):

a. Excavate outside of pipe.

b. Visually inspect outside of degraded pipe joint.

c. Visually inspect harness bolts.

d. If the entire harness bolt has not been exposed for visual inspection, to the maximum extent possible, nondestructively examine those portions of the harness bolts which have not been visually inspected.

e. If indicated by the inspection results, excavate entire harness bolt and visually inspect.

6. Pressure test the repaired pipe.

7. lnservice Inspections of the installed WEKO seal:

a. Inspect the installed seal every 36 months.

b. If technically justified, inspection frequency may be extended.

c. Monitor service water system per NRC GL 89-13, "Service Water Problems Affecting Safety Related Equipment."

3.6

NRC Staff Evaluation

3.6.1 Structural Integrity - Hoop and Axial Loads Structural evaluation of the bell and spigot joint demonstrates that a minimum mean bell wall thickness of 0.1 inches provides sufficient capacity for all design pipe loads (both axial and hoop). For bell housings with wall thickness below 0.1 inches, the mechanical repair system (WEKO seal with structural backing plate) provides hoop and radial strength and leak-tightness at the joint and prevents exposure of the degraded joint to the SW environment. NRC staff finds reasonable assurance that the structural integrity of the repaired pipe in regard to carrying hoop load is acceptable based on the stress calculations performed and found acceptable in previous NRC letter, dated April 8, 2014 (ML14097A029).

The seal repair (WEKO seal with structural backing plate) does not provide any axial strength to the joint. Axial piping loads due to internal pressure or seismic shifting are carried by the external harness assembly and the bell housing. The harness assembly is designed to carry the full design basis seismic loading. The bell and spigot joint provides axial restraint in the event of a failure of the harness assembly. Implementation of the WEKO seal repair requires verification that the pipe joint (either bell or harness assembly) is capable of carrying the axial pipe load.

This is accomplished by measuring the bell housing wall or inspection of the external harness assembly. As such, use of this repair to restore pressure boundary integrity requires verification that the joint remains capable of carrying axial pipe loads. Finite element analyses were performed and demonstrate that both configurations of the bell and spigot joint (PCCP and Special) are capable of carrying the design basis axial pipe load with a minimum cross-sectional steel area of 3.62 sq. inches (mean bell wall thickness of 0.042 inches). As such, installation of a WEKO seal with structural backing plate in a joint with mean bell wall thickness less than 0.042 inches requires verification that the harness assembly is intact and capable of carrying the design axial pipe load.

NRC staff finds reasonable assurance that the structural integrity of the repaired pipe in regard to carrying axial load is acceptable based on the stress calculations performed and found acceptable in previous NRC letter, dated April 8, 2014 (ML14097A029). The NRC staff finds that for piping in which the bell housing exceeds 0.042 inches, the bell housing is structurally sufficient to carry the required axial loads, while for piping in which the bell housing is less than 0.042 inches, the harness bolts are structurally sufficient to carry the required axial loads. The structural integrity of the repair is based on the stress calculations performed of the bell housing and harness assemblies and were found acceptable in previous NRC letter, dated April 8, 2014 (ML14097A029).

3.6.2 Material and Examination during Installation The NRC staff finds that the rubber seal, EPDM, used in the repair is resistant to the SW environment. In addition, AL6XN, a stainless steel alloy containing 6 percent molybdenum, is used for the retaining rings that compress the rubber seal to make a leak tight joint. The NRC staff confirms that AL6XN is also resistant to the SW environment and is therefore acceptable.

The 316 stainless steel backing plate is between the rubber seal and the carbon steel pipe and therefore is not exposed to the SW environment. The 316 stainless steel is resistant to ground water and therefore is acceptable for this application. Therefore, the NRC staff finds that the materials used in the repair are compatible with the SW environment to minimize degradation.

A condition of installation of the WEKO seal with steel backing plate requires that prior to installation of the WEKO seal, the degraded joint must be thoroughly cleaned and re-coated with an approved epoxy sealant. Cleaning and re-coating, in conjunction with seal installation, prevents future exposure of the joint to the SW environment, ensuring that there will be no additional degradation of the joint. The NRC staff finds that joint cleaning provides additional assurance of the leak tightness and structural integrity of the repair, while prevent further degradation of the bell and spigot joint.

The NRC staff finds pressure testing after installation of the WEKO seal with steel backing plate, to be acceptable to verify that the repair is leak tight. In addition, the NRC finds measurement of the bell wall thickness ensures the proper repair process is used and ensures the repaired pipe joint will have structural integrity to carry the appropriate loads in the piping system. Piping joints with a bell wall thickness less than 0.042 inches requires verification by visual examination that the harness assembly is intact and capable of carrying the design axial pipe loads. If through-wall leakage was found prior to the installation of the repair, inspection of as much of the harness bolts that may have been corroded by the SW leaking from the joint will be performed. Additionally, a VT-2 examination of the exposed portion of piping is to be performed for evidence of leakage after the repair is made. Based on the above inspections, the NRC staff finds that there is reasonable assurance of the structural integrity of the repaired pipe because either the bell wall thickness, or harness assembly will be examined and verified to perform its function of carrying the appropriate loads.

Therefore, the NRC staff considers the repair materials and installation examinations to be acceptable since the materials are compatible with the operating environment, and the examinations ensure leak tight and structural integrity while meeting and exceeds the construction code requirements.

3.6.3 Inservice Inspection and Monitoring To ensure pressure boundary and structural integrity, the licensee will perform inservice inspections, once every three years, of all joints and also all installed WEKO seals in conjunction with GL 89-13 inspections to ensure that (1) degradation of the joints has not taken place, and (2) the WEKO seals are intact and undamaged. In addition, if at any time an external harness assembly is exposed, an examination of the rod and underlying exposed joint externals will also be accomplished. The NRC staff finds the inservice inspection and monitoring of the repair acceptable since it meets and exceeds the requirements of Section XI of the ASME Code and GL 89-13. In addition, the inservice inspections ensures the structural integrity of the piping system is still bounded by the analysis for carrying the appropriate piping loads, and to be considered as a permanent repair. Therefore, the NRC staff finds the repair provides an acceptable level of quality and safety to be a permanent repair for the licensed life of the plant based on the material used, inspections performed during installation, stress analysis and inservice inspections.

3.6.4 Operational and Repair Risks The licensee has determined that performing an ASME Code-compliant repair/replacement on the degraded portion of SW piping in accordance with ASME Code,Section XI, IWA-4000 represents a hardship or unusual difficulty without a compensating increase in the level of quality and safety. The hardship cited by the licensee deals with the unusual location and configuration of the piping to affect a repair that creates operational risks. Due to the overlapping pipe segment design, replacement of the degraded joint is not possible with removing the entire system or redesigning the system. In addition, the SW piping is buried 8 feet below grade and would require a large excavation that would uncover other adjacent piping that could be damaged. These adjacent piping are necessary to be in service in order to perform their safety function. In addition, potential damage and adverse effects to the ISFSI and accumulator tank buildings may occur if the piping would be required to be excavated.

Therefore, the NRC staff finds that the plant-specific operational issues and repair risks provides a valid basis for establishing hardship without a compensating increase in the level of quality and safety with respect to implementing an ASME Code-compliant repair/replacement. In regard to the lifespan of the alternative repair, the NRC staff finds that the alternative repair provides an acceptable level of quality and safety to be a permanent repair for the life of the plant based on the material used, inspections performed during installation, stress analysis and inservice inspections.

Based on the review of the information provided above, the NRC staff finds that there is reasonable assurance of adequate protection based on (1) the repair designed to the construction code of record and Section III of the ASME Code, (2) the repair designed to carry all applicable loads, (3) use of corrosion resistant material and associated coatings to minimize corrosion from service water, (4) enhanced inspections and pressure testing of the repair during installation, and (5) enhanced inservice inspections and monitoring ensuring the structural integrity requirements of ASME Code continue to be met.

Therefore, the NRC finds the alternative will provide reasonable assurance of structural integrity in Salem 1 and 2 SW supply and discharge headers, and its intended safety function will be maintained in that the licensee will ensure the piping continues to meet the structural integrity requirements of the construction code and the ASME Code.

4.0 CONCLUSION

The NRC staff concludes that the proposed alternative to install a WEKO seal with structural backing plate to restore the pressure boundary integrity of degraded bell and spigot joints in the SW supply and discharge headers acceptable for contingency planning if degraded bell and spigot joints are found during the fifth inservice inspection interval at Salem 1 and 2. The licensee has determined that performing an ASME Code-compliant repair/replacement on the degraded portion of SW piping in accordance with ASME Code,Section XI, IWA-4000 represents a hardship or unusual difficulty without a compensating increase in the level of quality and safety. In addition, the NRC concludes that the installed WEKO seal with structural backing plate is a permanent repair for the licensed life of the plant since the repair provides an acceptable level of quality and safety based on the material used, inspections performed during installation, stress analysis and inservice inspections to be performed.

Accordingly, the NRC staff concludes that the licensee has adequately addressed all of the regulatory requirements set forth in 10 CFR 50.55a(z)(2). Therefore, the NRC authorizes the use of the proposed alternative in Request for Relief SC-I5R-221 for the fifth 10-year ISI interval at Salem 1 and 2. Once the alternative repair is installed during the fifth 10-year lSI interval, the installed alternative may remain in place for the life of the plant. Should the licensee desire to install the alternative during a subsequent 10-year lSI interval, the licensee must seek authorization from the NRC staff for that interval.

All other ASME Code,Section XI requirements for which an alternative was not specifically requested and approved remain applicable, including third-party review by the Authorized Nuclear Inservice Inspector.

Principal Contributor: John Honcharik, NRR Date: February 2, 2023

ML23019A348 OFFICE NRR/DORL/LPL1/PM NRR/DORL/LPL1/LA NRR/DNRL/NPHP/BC NRR/DORL/LPL1/BC NAME JKim KEntz MMitchell HGonzalez DATE 01/19/2023 01/20/2023 01/13/2023 02/02/2023