ML110060442

Relief Request I3R 06, Temporary Non-Code Repair of Service Water Supply System Piping

ML110060442
Person / Time
Site:	Harris
Issue date:	04/21/2011
From:	Doug Broaddus Plant Licensing Branch II
To:	Burton C Carolina Power & Light Co
Mozafari B, NRR/ADRO/DORL, 415-2020
References
TAC ME3765
Download: ML110060442 (12)

Text

UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20555-0001 April 21, 2011 Mr. Christopher L. Burton, Vice President Shearon Harris Nuclear Power Plant Carolina Power & Light Company Post Office Box 165, Mail Zone 1 New Hill, North Carolina 27562-0165

SUBJECT:

SHEARON HARRIS NUCLEAR POWER PLANT, UNIT 1 - RELIEF REQUEST 13R-06, TEMPORARY NON-CODE REPAIR OF SERVICE WATER SUPPLY SYSTEM PIPING (TAC NO. ME3765)

Dear Mr. Burton:

By letter dated April 15, 2010 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML101170058), as supplemented by letters dated October 4, 2010 and January 27, 2011, (ADAMS Accession Nos. ML102861818 and ML110340191, respectively), Carolina Power & Light Company (the licensee) submitted Relief Request 13R-06, for the Shearon Harris Nuclear Power Plant, Unit 1 (HNP).

Pursuant to Title 10 of the Code of Federal Regulations (10 CFR) 50.55a(g)(5)(iii), the licensee proposed to defer the American Society for Mechanical Engineers Boiler and Pressure Vessel Code (ASME Code) repair of a degraded service water system piping at HNP, until adequate time was available for the repair, but no later than the next scheduled refueling outage, RFO-16, in October 2010. The licensee requested relief because the proposed temporary non-code repair is not permitted on the ASME Code Class 3 piping without prior relief from the Nuclear Regulatory Commission (NRC).

The NRC staff notes that impracticality for the purpose of Generic Letter (GL) 90-05, "Guidance For Performing Temporary Non-Code Repair Of ASME Code Class 1, 2, and 3 Piping," is defined to exist if the flaw detected during plant operation is in a section of Class 3 piping that cannot be isolated for completing ASME Code repair within the time period permitted by the limiting condition for operation of the affected system as specified in the plant's technical speCifications, and performance of ASME Code repair necessitates a plant shutdown.

However, the staff's position is that shutting down the plant to perform mid-cycle repair is not an impracticality but a hardship. Therefore, the NRC staff has evaluated the licensee's proposed alternatives per the evaluation considerations of GL 90-05 pursuant to 10 CFR 50.55a(a)(3)(ii),

hardship or unusual difficulty without a compensating increase in the level of quality or safety.

On the basis of review and evaluation of the licensee's submittals, the NRC staff concludes that the proposed alternatives would provide reasonable assurance of operational readiness of the service water system and requiring an ASME Code repair immediately could have resulted in plant shutdown, and resulted in hardship or unusual difficulty without a compensating increase in the level of quality or safety. Furthermore the licensee's proposed alternative provides reasonable assurance of structural intergrity and public health and safety. Therefore, pursuant to 10 CFR 50.55a(a)(3)(ii), the NRC authorizes the licensee's proposed alternatives for the third

C. Burton

- 2 10-year inservice inspection interval at HNP, but no later than, RFO-16, which began in October 2010.

The NRC staffs safety evaluation is enclosed. If you have any questions regarding this matter, please contact Brenda Mozafari at (301) 415-2020.

Sincerely, Douglas A. Broaddus, Chief Plant Licensing Branch 11-2 Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket No. 50-400

Enclosure:

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SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION REQUEST FOR RELIEF NO. 13R-06 TEMPORARY NON-CODE REPAIR OF SERVICE WATER SUPPLY SYSTEM PIPING SHEARON HARRIS NUCLEAR POWER PLANT, UNIT 1 CAROLINA POWER & LIGHT COMPANY DOCKET NUMBER 50-400

1.0 INTRODUCTION

By letter dated April 15, 2010 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML101170058), as supplemented by letters dated October 4,2010 and January 27,2011, (ADAMS Accession Nos. ML102861818 and ML110340191, respectively), Carolina Power & Light Company (the licensee), now doing business as Progress Energy Carolinas, Inc., submitted Relief Request (RR) 13R-06 for U.S. Nuclear Regulatory Commission (NRC) review and approval. Pursuant to Title 10 of the Code of Federal Regulations (10 CFR) 50.55a(g)(5)(iii), the licensee proposed to defer the American Society for Mechanical Engineers Boiler and Pressure Vessel Code (ASME Code) repair of a degraded service water system piping at the Shearon Harris Nuclear Power Plant, Unit 1 (HNP), until adequate time was available for the repair, but no later than the next scheduled refueling outage, RFO-16, in October 2010. The licensee requested relief because the proposed temporary non-code repair is not permitted on the ASME Code Class 3 piping without prior relief from the NRC.

On December 7,2009, during operator rounds, a through-wall leak was discovered on the carbon steel sockolet and sockolet-to-pipe weld interface on instrument test connection line 3SW3/4-1630SA-1 off the "A" train emergency service water supply piping to the "A" essential service chilled water condenser. The plant was operating in Mode 1 at 100 percent power. At the leak point only slight moisture accumulation can be seen with no actual quantifiable leak rate with the "An emergency service water header supplied by normal service water and pressure at approximately 80 pounds per square inch gauge.

2.0 REGULATORY REQUIREMENTS As specified by 10 CFR 50.55a(g), inservice inspection of nuclear power plant components shall be performed in accordance with the requirements of the ASME Code,Section XI, except where specific written relief has been granted by the NRC pursuant to 10 CFR 50.55a(g)(6)(0. Further, 10 CFR 50.55a(g)(6)(i) states that NRC may grant such relief and may impose such alternative requirements as it determines is authorized by law and will not endanger life or property or the common defense and security and is otherwise in the public interest, given the consideration of the burden upon the licensee.

Enclosure

-2 Pursuant to 10 CFR 50.55a(a)(3), alternatives to the requirements of paragraph (g) of 10 CFR 50.55a may be used, when authorized by the NRC, if (i) the proposed alternatives would provide an acceptable level of quality and safety or (ii) compliance with the specified requirements would result in hardship or unusual difficulty without a compensating increase in the level of quality and safety. 10 CFR 50.55a(g)(5)(iii) states that if the licensee has determined that conformance with certain code requirements is impractical for its facility, the licensee shall notify the Commission and submit, as specified in Section 50.4, information to support the determinations.

Generic Letter (GL) 90-05, "Guidance for Performing Temporary Non-Code Repair of ASME Code Class 1, 2, and 3 Piping," provides a basis to allow temporary non-code repairs for ASME Code Class 3 piping.

3.0 TECHNICAL EVALUATION

3.1 ASME Code Components Affected

ASME Code Class:

Class 3 Component:

Interface Between a Sockolet and Sockolet-to-Pipe Weld on Instrument Test Connection Line 3SW3/4-1630SA-1 System:

Service Water System The component for which relief is requested is listed below.

System I Component Component Material Service Water System; A Carbon Steel Sockolet and Sockolet-to-Pipe Weld on Instrument Test Connection Line 3SW3/4-1630SA-1, a ~-Inch Supply Piping to Root Valve 1 SW-1344, off the "A" Train Emergency Service Water Supply Piping to the "An Essential Service Chilled Water Condenser Carbon Steel 3.2

Applicable Code Edition and Addenda

The code of record for the third 1 O-year in-service inspection (lSI) interval at HNP is the 2001 Edition through 2003 Addenda of the ASME Code,Section XI.

3.3

Applicable Code Requirement

The ASME Code Section XI, Article IWA-4000, "Repair or Replacement Activities," provides the requirements for performing repair or replacement activities on components and their supports.

This is used whenever a flaw is discovered that does not meet the ASME Code,Section XI, requirements.

According to NRC Inspection Manual, Part 9900: Technical Guidance, "Operability Determinations and Functionality Assessments for Resolution of Degraded or Nonconforming Conditions Adverse to Quality or Safety," Section C.12, if a leak is discovered in an ASME Code Class 1, 2, or 3 component in the conduct of an inservice inspection, maintenance activity, or

- 3 facility operation, corrective measures may require repair or replacement activities in accordance with Article IWA-4000 of Section XI of the ASME Code.

3.4 Proposed Alternative Relief is requested from the ASME Code,Section XI, Article IWA-4000, requirements to defer the ASME Code repair of the identified through-wall flaw until the next outage of sufficient duration, but no later than the next refueling outage (RFO-16) provided the conditions of GL 90-05, are met.

Impracticality Determination According to GL 90-05, an ASME Code repair is required for the ASME Code Class 1, 2, and 3 piping unless specific written relief is granted by the NRC. Requesting relief from the ASME Code requirements is appropriate when performing the repair at the time of discovery is determined to be impractical. A repair is considered to be impractical if:

• The flaw detected during plant operation is in a section of ASME Code Class 3 piping that cannot be isolated to complete an ASME Code repair within the time period permitted by the limiting condition for operation of the affected system as specified in the plant Technical Specifications, and

• Performance of code repair necessitates a plant shutdown.

The licensee stated that the flaw identified is a pinhole leak on a sockolet fitting at the interface between a sockolet and sockolet-to-pipe weld on 3SW3/4-1630SA-1, the supply line to root valve ISW-1344 and a downstream pressure indicator test connection point. This %-inch instrument test connection line is off of the "A" train emergency service water supply piping to the "A" essential service chilled water condenser. For the repair of this flaw, isolation of the "A" emergency service water system would require header depressurization and potentially freeze sealing.

The licensee stated that the HNP Technical Specifications Limiting Condition for Operation associated with less than two independent water loops of the emergency service water system is 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> or at least be in hot standby within 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br />.

3.5 Licensee's Basis for Use A through-wall leak was discovered on the carbon steel sockolet and sockolet-to-pipe weld interface on instrument test connection line 3SW3/4-1630SA-1 when the plant was operating in Mode 1 at 100 percent power.

The licensee noted that after paint was removed from the area directly surrounding the leak, an axial indication along the weld surface indicative of the start and stop location of the weld was revealed. Based on the proximity of the leak to this location, it could be a lack-of-fusion in welding existed following installation and a small crevice was created partially or fully between the inside diameter (10) and outside diameter (00) of the weld and sockolet interface.

-4 The licensee stated that although the exact cause of the weld defect cannot be determined, it could be a result of impurities, work practices, or workmanship. If the initial flaw was not present through the entire thickness of the sockolet, then the crevice or pit likely propagated through a corrosion process. Once a small crevice becomes wetted by service water, its passive film begins to break down. The immediate area surrounding the region then exhibits corrosion in a mechanism similar to pitting corrosion, until a through-wall leak is present.

Although welds and their surrounding heat affected zones are particularly susceptible to local corrosion attack, corrosion cells formed by this mechanism tend to remain localized and not propagate rapidly into adjacent areas. The licenses stated that based on the number of similar welds performed on the emergency service water system during the refueling outage, RFO-15, in April 2009 and previous outages, with no other failures identified, there is no programmatic or widespread deficiency present. This is considered an isolated incident.

The licensee stated that in order to comply with the ASME Code repair requirements, the plant would need to be shut down to perform the repair. As stated in Gl 90-05, the rather frequent instances of small leaks in some ASME Code Class 3 systems, such as service water systems, could lead to an excessive number of plant startup and shutdown cycles with undue and unnecessary stress on facility systems and components if the facilities were to perform a ASME Code repair when the leakage is identified. Therefore, the temporary non-code repair of ASME Code Class 3 piping that cannot be isolated without a plant shutdown is justified in this instance. The licensee requested approval for its proposed temporary non-code repair of the ASME Code Class 3 piping, based on the impracticality in performing an ASME Code repair while the plant is operating.

The licensee proposed, per the guidelines of Gl 90-05, to defer repair of the identified flaw until the next scheduled outage exceeding 30 days but no later than the next refueling outage. To ensure that the acceptance criteria of Gl 90-05 were met, the licensee implemented compensatory actions to detect changes in the condition of the identified defect.

The licensee stated that deferral of the ASME Code repair of the identified through-wall flaw would not impact the capability of the emergency service water system to perform its intended safety-related function based on the following reasons:

• The current loss of flow from the emergency service water system was negligible compared to the total system flow. Even with a conservatively estimated leak rate of one drop every 5 minutes, the minimum design emergency service water flow through the "A" train header is approximately 16,000 gallons per minute (gpm) to 18,000 gpm.

• The leak is on the weld and not the pipe wall. Based on past emergency service water through-wall leak analyses, a weld leak is indicative of crevice corrosion which typically creates a localized flaw with no mechanism to propagate rapidly into the adjoining pipe or tee section. Therefore, the leak will not expand significantly unless a new failure mechanism is introduced.

• There is no concern of diversion of flow since the leak is downstream of all emergency service water loads and is very small.

- 5 Based on nondestructive examination using ultrasonic testing (UT) of area adjacent to the weld that verified the wall thickness is near nominal thickness values, there is no impact on the structural integrity of the emergency service water line involved. Near nominal thickness values were recorded for the %-inch pipe and the 12-inch pipe adjacent to the sockolet, with no general area thinning identified.

• The leak is not affecting any other equipment important to safety in the immediate area.

In accordance with the guidance in GL 90-05, an augmented inspection of five other similar locations has been performed. These inspections did not reveal any locations approaching minimum wall thickness or any areas of concern.

The licensee stated that there were no other identified leaks in the emergency service water system. The pinhole leak would be permanently repaired by replacing the affected line during the next refueling outage, RFO-16 scheduled to begin in October 2010. Until this replacement, the leak rate would be monitored weekly and UT measurements of the area of the leak will be taken every 3 months, both of which meet the criteria of GL 90-05.

The licensee stated that a walkdown of line 3SW3/4-1630SA-1 with WC-2A inservice and normal service water supplying "N emergency service water revealed little to no vibration present on the line (Le. could not be felt by touch). This line extends vertically from the 12-inch line 3SWI2-83SA-1. Since the %-inch line is less than 2.0 feet in length and weighs approximately 20 pounds, it is therefore quite rigid. Additionally, the 12-inch line is supported by a three-way hanger within 2.0 feet axially of the %-inch line. Therefore, vibration induced fatigue is not a concern.

The licensee stated that for structural integrity assessment of the subject degraded pipe, flaw evaluation performed in accordance with GL 90-05 "through-wall flaw" approach. The results demonstrated that the flaw was acceptable for continued operation under the GL 90-05 augmented inspections guidelines. The NRC staff review of the licensee's assessment confirmed that structural integrity was maintained.

The licensee stated that an augmented UT inspection was performed to assess the overall degradation of the affected system. In accordance with GL 90-05, Section CA, inspection of at least five most susceptible (and accessible) locations were performed. In addition, measurements of the area where the flaw is located will be performed every 3 months, as required by GL 90-05. There are no operating mode restrictions associated with this condition.

The leak will be visually inspected weekly by Operations until it is repaired in RFO-16. Normal walkdowns are performed once every quarter in accordance with 10 CFR 50.65, "Requirements for monitoring the effectiveness of maintenance at nuclear power plants." This increase in periodicity of inspection is in accordance with the criteria of GL 90-05, which recommends that a qualitative assessment of leakage be performed at least weekly to determine whether any degradation of structural integrity was detected.

- 6 3.7 Duration of Relief RR 13R-06 is submitted for approval up to the next scheduled outage exceeding 30 days, but no later than the refueling outage, RFO-16, provided the condition continues to meet the acceptance criteria of GL 90-05. RFO-16 at HNP was scheduled to begin in October 2010.

4.0 STAFF EVALUATION The NRC staff notes that impracticality for the purpose of GL 90-05 is defined to exist if the flaw detected during plant operation is in a section of Class 3 piping that cannot be isolated for completing ASME Code repair within the time period permitted by the LCO of the affected system as specified in the plant TS, and performance of ASME Code repair necessitates a plant shutdown. However, the NRC staff position is that shutting down the plant to perform mid-cycle repair is not impractical but is a hardship. Therefore, the NRC staff has evaluated the licensee's proposed alternatives per the evaluation considerations of GL 90-05 pursuant to 10 CFR 50.55a(a)(3)(ii), hardship or unusual difficulty without a compensating increase in the level of quality or safety.

The NRC staff has evaluated the information provided in RR 13R-06 dated April 15, 2010, for the temporary non-code repair of ASME Code Class 3 piping weld with a through-wall pinhole leak at HNP, and as supplemented by letters dated October 4, 2010, and January 27, 2011, in response to the NRC staff request for additional information (RAI).

The licensee stated that during operator rounds on December 7,2009, slight moisture accumulation with no actual quantifiable leak rate on the "AI! train emergency service water supply pipe 3SW3/4-1630SA-1 indicated a leak point at the interface between a sockolet and sockolet-to-pipe weld. At the time of flaw discovery, the plant was operating in Mode 1 at 100 percent power.

An ASME Code repair would be required to address an identified through-wall flaw in an ASME Code Class 3 component to ensure the structural integrity of the component independent of the operational mode of the facility. The ASME Code,Section XI, Article IWA-4000, provides the requirements for performing ASME Code repair or replacement on components and their supports. NRC Inspection Manual, Part 9900, provides guidance for determinations of operability and assessments of functionality for resolution of degraded or nonconforming conditions adverse to quality or safety. GL 90-05 provides a basis to allow temporary non-code repairs for ASME Code Class 1, 2, and 3 piping. The licensee proposed to follow the requirements in GL 90-05.

On April 16, 2008, the NRC issued Revision 1 to the NRC Regulatory Issue Summary 2005-20, "Revision to NRC Inspection Manual, Part 9900: Technical Guidance, "Operability Determinations and Functionality Assessments for Resolution of Degraded or Nonconforming Conditions Adverse to Quality or Safety." Section C.11 of the updated NRC Inspection Manual, Part 9900, states, in part, that the NRC staff accepts GL 90-05 for conclusively establishing that a technical specification required ASME Code Class 3 piping system that contains a flaw has adequate structural integrity. Section C.12 of the updated NRC Inspection Manual, Part 9900, states, in part, that the licensee may evaluate the structural integrity of ASME Code Class 3 piping by evaluating the flaw using the criteria of GL 90-05, Enclosure 1, Section C.3.a. Further,

- 7 relief from the ASME Code requirements is needed even if the structural integrity is found acceptable when applying GL 90-05.

Section C.1 of GL 90-05 states, in part, that the licensee can only use this provision if the flaw was detected during operation and an impracticality determination was made. The licensee stated during plant operation in Mode 1 at 100 percent power, a pinhole leak was discovered on the "Au train emergency service water supply pipe 3SW3/4-1630SA-1 at the interface between a sockolet and sockolet-to-pipe weld. The licensee determined that the leak was from a through-wall flaw located in a section of piping in the service water system that cannot be isolated to complete ASME Code repair without a plant shutdown. Isolation of the "A" emergency service water system would require header depressurization and potentially freeze sealing. Technical specifications provide only a limited 72-hour timeframe for this evolution. The staff finds the licensee provided sufficient basis for compliance with GL 90-05.

Therefore, the staff finds the licensee basis met the guidance requirement in accordance with GL 90-05.

GL 90-05, Enclosure 1. Section C.2, states, in part, that a root cause determination and flaw characterization should be performed. The licensee stated that paint from the area directly surrounding the leak was removed and an axial indication was discovered along the weld surface indicative of the start and stop location of the weld. Based on the proximity of the leak to this location, the licensee determined that it could be a lack-of-fusion in welding existed following installation, and a small crevice was created partially or fully between the 10 and 00 of the weld and sockolet interface. The licensee stated that the root cause for the pinhole leak was attributed to crevice corrosion. Crevice corrosion progression is localized and generally very slow away from crevice conditions and therefore, will not lead to a catastrophic failure of the degraded component with proper monitoring. The NRC staff finds the licensee's root cause determination is acceptable. Therefore, the staff finds that the licensee met these evaluation requirements in accordance with GL 90-05.

By letter dated September 22, 2010, the NRC staff issued an RAI requesting the licensee to provide a detailed description of the input parameters, assumptions, and methodology used in the licensee's "Calculation 8050-79." In response to the RAI, the licensee revised its initially submitted flaw evaluation (Le. "Calculation 8050-79") and resubmitted a revision for NRC review. The licensee stated that the revision is needed due to an error that was inadvertently transcribed from a previous evaluation. The licensee eliminated deadweight contribution to total stress because the line is in a vertical orientation and attached to a massive pipe that is supported by a three-way hanger. Additionally, the mean pipe radius calculation was revised to conservatively assume a pipe wall thickness equal to the minimum required wall thickness, tmin.

The initially submitted "Calculation 8050-79" in RR 13R-06. Enclosure 1. assumed a pipe wall thickness equal to the nominal wall thickness, tnom

• The NRC staff finds that the licensee's revised flaw evaluation input parameters are consistent with GL 90-05, Enclosure 1, Section 3.a.

Section C.3 of GL 90-05, Enclosure 1, requires the licensee to assess the structural integrity of component by performing a flaw evaluation. Section C12 of NRC Inspection Manual, Part 9900, states that GL 90-05, Enclosure 1, Section C.3, provides a NRC acceptable flaw evaluation guideline for through-wall flaws. The NRC staff reviewed the licensee's revised flaw evaluation, provided in letter dated October 4,2010, against this guideline. The NRC staff finds the licensee's assumption that the pinhole leak had an opening diameter of 0.1 O-inch was

- 8 conservative. In addition, the NRC staff noted that the licensee satisfied the condition for acceptable flaw size specified in GL 90-05, Enclosure 1, Section C.3, "through-wall flaw" approach, which specifies that the measured flaw length should be less than either 3 inches or 15 percent of the length of the pipe circumference. Further, the staff agrees with the licensee's calculated stress intensity factor of approximately 3.315 kSi(in)o5 and finds it to be less than the critical stress intensity factor which represents the fracture toughness of the material. According to GL 90-05, the critical stress intensity factor for ferritic steel is 35 ksi(in)o.5. Therefore, the NRC staff finds that the licensee's flaw evaluation has satisfied the stress intensity factor requirements of GL 90-05.

Section C.4 of GL 90-05, Enclosure 1, requires the licensee to perform an augmented inspection once the flaw is detected and evaluated. The licensee stated that augmented inspection of five other similar locations was performed. The UT measurements of wall thickness did not reveal any piping approaching minimum wall thickness or any other areas of concern. The UT measurements of wall thickness of the area where the flaw is located will be performed every 3 months, as required by GL 90-05. The leak will be visually inspected weekly by Operations until it is repaired in RFO-16. Normal walkdowns are performed once every quarter in accordance with 10 CFR 50.65. The NRC staff finds the licensee's augmented inspections satisfy the requirements of GL 90-05.

The NRC staff has determined that the licensee has successfully met all requirements and taken all actions necessary to implement GL 90-05 in support of deferring the ASME Code repair of a degraded service water system piping at HNP, until adequate time was available for the repair, but no later than the scheduled refueling outage, RFO-16, in October 2010.

5.0 REGULATORY COMMITMENTS In Attachment 2 of the April 15, 2010 letter, the licensee made the following regulatory commitments:

. No.

Regulatory Commitment Due Date

1.

Replace temporary non-code repair of defect in weld on line 3SW3/4-1630SA-1 with a permanent repair. Temporary noncode repair consists of deferral of code repair until the next scheduled outage exceeding 30 days but no later than the next scheduled refueling outage, provided the condition continues to meet the acceptance criteria of Generic Letter 90-05.

RFO-16 (November 2010)

2.

Perform weekly inspections of location to detect changes in size or leakage of weld until code repair is performed. The s.-i,e-evaluated structural integrity and the monitoring frequency will be

~ significant changes are found in the condition of the weld area during this monitorin.-9.

3.

Perform ultrasonic measurements of the area where the RFO-16 (November 2010)

RFO-16 (November 2010)

Iflaw IS located at least once every 90 days.

The licensee in its letter (HNP-11-012) dated January 27, 2011, confirmed that it has completed its regulatory commitment NO.1. The licensee completed the repair of the subject piping in

-9 accordance with the ASME Code,Section XI in RFO-16, per the guidance of GL 95-05. Thus the other 2 commitments was met and are no longer applicable.

6.0 CONCLUSION

On the basis of review and evaluation of the licensee's submittals, the NRC staff concludes that the proposed alternatives would provide reasonable assurance of operational readiness of the service water system. Requiring an ASME Code repair immediately could result in plant shutdown, and result in hardship or unusual difficulty without a compensating increase in the level of quality or safety. Furthermore, the NRC staff concludes that the proposed alternative would have provided reasonable assurance of structural integrity of the subject piping during the interim period until completion of the Code repair. Therefore, pursuant to 10 CFR 50.55a(a)(3)(ii), the NRC authorizes the licensee's proposed alternatives for the third 10-year lSI interval at HNP, but no later than the refueling outage, RFO-16, in October 2010.

All other ASME Code,Section XI, requirements for which relief was not specifically requested and authorized herein by the NRC staff remain applicable, including the third party review by the Authorized Nuclear In-service Inspector.

Principal Contributor: Ali Rezai Date: April 21, 2011

C.Burton

- 2 10-year inservice inspection interval at HNP, but no later than, RFO-16, which began in October 2010.

The NRC staff's safety evaluation is enclosed. If you have any questions regarding this matter, please contact Brenda Mozafari at (301) 415-2020.

Sincerely, IRA by SLingam fori Douglas A. Broaddus, Chief Plant Licensing Branch 11-2 Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket No. 50-400

Enclosure:

Safety Evaluation cc w/enclosure: Distribution via Listserv DISTRIBUTION:

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