ML15070A428

Relief Request ANO2-ISI-017, Alternative to Utilize ASME Code Case N-513-4 for the Fourth 10-Year Inservice Inspection Interval

ML15070A428
Person / Time
Site:	Arkansas Nuclear
Issue date:	03/16/2015
From:	Markley M Plant Licensing Branch IV
To:	Entergy Operations
George A
References
TAC MF5107
Download: ML15070A428 (9)

Text

UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20555-0001 March 16, 2015 Vice President, Operations Arkansas Nuclear One Entergy Operations, Inc.

1448 S.R. 333 Russellville, AR 72802

SUBJECT:

ARKANSAS NUCLEAR ONE, UNIT 2 - RELIEF REQUEST AN02-ISl-017,,

ALTERNATIVE TO ASME CODE, SECTION XI REQUIREMENTS (TAC NO. MF5107)

Dear Sir or Madam:

By letter dated October 31, 2014, as supplemented by letter dated November 1, 2014, Entergy Operations, Inc. (Entergy, the licensee), submitted a request to the U.S. Nuclear Regulatory Commission (NRC) for the use of an alternative to certain American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel (Code),Section XI requirements at Arkansas Nuclear One, Unit 2 (AN0-2).

Pursuant to Title 10 of the Code of Federal Regulations (10 CFR) 50.55a(a)(3)(ii), the licensee proposed to use an alternative flaw evaluation to that of ASME Code Case N-513-3, "Evaluation Criteria for Temporary Acceptance of Flaws in Moderate Energy Class 2 or 3 Piping,Section XI, Division 1," to disposition a pinhole leak at the corner of an elbow in the service water piping in lieu of performing repair, on the basis that complying with the ASME Code requirement to repair the flaw would result in hardship or unusual difficulty without a compensating increase in the level of quality and safety.

The paragraph headings in 10 CFR 50.55a were changed by Federal Register notice dated November 5, 2014 (79 FR 65776), which became effective on December 5, 2014 (e.g.,

10 CFR 50.55a(a)(3)(i) is now 50.55a(z)(1 ), and 50.55a(a)(3)(ii) is now 50.55a(z)(2)). See the cross reference tables, which are cited in the notice, in the Agencywide Documents Access and Management System (ADAMS) at Accession Nos. ML14015A191 and ML14211A050.

The NRC staff has reviewed the subject request and concludes, as set forth in the enclosed safety evaluation, that Entergy has adequately addressed all of the regulatory requirements set forth in 10 CFR 50.55a(z)(2). Therefore, the NRC authorizes the use of Relief Request AN02-ISl-017 at AN0-2 until the end of the fall 2015 refueling outage, the time at which the pinhole exceeds the allowable flaw size, or the time at which the leak rate exceeds the allowable leak rate, whichever occurs first.

The NRC staff provided verbal authorization for Relief Request AN02-ISl-017 during a teleconference with your staff on November 1 2014.

All other ASME Code,Section XI, requirements for which relief was not specifically requested and approved in this relief request remain applicable, including third-party review by the Authorized Nuclear lnservice Inspector.

\

The detailed results of the NRC staff review are provided in the enclosed safety evaluation. If you have any questions concerning this matter, please contact Ms. Andrea George of my staff at (301) 415-1081 or by e-mail at Andrea.George@nrc.gov.

Sincerely, Michael T. Markley, Chief Plant Licensing Branch IV-1 Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket No. 50-368

Enclosure:

Safety Evaluation cc w/encl: Distribution via Listserv

UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20555-0001 SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELIEF REQUEST AN02-ISl-017 REGARDING PROPOSED ALTERNATIVE FOR ACCEPTANCE OF DEGRADED SERVICE WATER SYSTEM PIPING ENTERGY OPERATIONS, INC ARKANSAS NUCLEAR ONE UNIT, 2 DOCKET NO. 50-368

1.0 INTRODUCTION

By letter dated October 31, 2014, and as supplemented by letter dated November 1, 2014 (Agencywide Documents Access and Management System (ADAMS) Accession Nos. ML14309A188 and ML14309A186, respectively), Entergy Operations, Inc. (Entergy, the licensee), requested relief from the requirements of the American Society of Mechanical Engineers Boiler and Pressure Vessel Code (ASME Code),Section XI, at Arkansas Nuclear One, Unit 2 (AN0-2).

Specifically, pursuant to Title 10 of the Code of Federal Regulations (10 CFR) 50.55a(a)(3)(ii),

the licensee proposed an alternative flaw evaluation to that of ASME Code Case N-513-3 "Evaluation Criteria for Temporary Acceptance of Flaws in Moderate Energy Class 2 or 3 Piping,Section XI, Division 1," to disposition a pinhole leak at an elbow of the service water (SW) system piping in lieu of performing a repair on the basis that complying with the specified ASME Code requirement to repair the degraded elbow would result in hardship or unusual difficulty without a compensating increase in the level of quality and safety.

The paragraph headings in 10 CFR 50.55a were changed by Federal Register notice dated November 5, 2014 (79 FR 65776), which became effective on December 5, 2014 (e.g.,

10 CFR 50.55a(a)(3)(i) is now 50.55a(z)(1 ), and 50.55a(a)(3)(ii) is now 50.55a(z)(2)). See the cross reference tables, which are cited in the notice, in ADAMS at Accession Nos. ML14015A191 and ML14211A050.

On November 1, 2014 (ADAMS Accession No. ML14309A138), the U.S. Nuclear Regulatory Commission (NRC) staff authorized the use of Relief Request AN02-ISl-017 at AN0-2 until the end of the fall 2015 refueling outage, the time at which the pinhole exceeds the allowable flaw sizes, or the time at which the leak rate exceeds the allowable leak rate, whichever event occurs first. This safety evaluation documents the NRC staff's technical basis for the verbal authorization.

Enclosure

2.0 REGULATORY EVALUATION

Pursuant to 10 CFR 50.55a(g)(4), the ASME Code Class 1, 2, and 3 components (including supports) must meet the requirements, except the design and access provisions and the preservice examination requirements, set forth in the ASME Code,Section XI, "Rules for lnservice Inspection of Nuclear Power Plant Components," to the extent practical within the limitations of design, geometry, and materials of construction of the components.

Pursuant to 10 CFR 50.55a(z), alternatives to the requirements of paragraph (g) of 10 CFR 50.55a may be used when authorized by the Director, Office of Nuclear Reactor Regulation. A proposed alternative must be submitted and authorized prior to implementation.

• The licensee must demonstrate (.1) the proposed alternative would provide an acceptable level of quality and safety; or (2) compliance with the specified requirements of this section would result in hardship or unusual difficulty without a compensating increase in the level of quality and safety.

Based on the above, and subject to the following technical evaluation, the NRC staff finds that regulatory authority exists for the licensee to request the use of an alternative and the NRC to authorize the proposed alternative.

3.0 TECHNICAL EVALUATION

3.1 ASME Code Component Affected The affected component is the ASME Code Class 3, 2HCC-2003 {elbow) and 2HBC-33 (sweep-o-let) of Service Water (SW) piping to 2P-7B, Emergency Feed Water (EFW) Pump Suction.

• 3.2 Applicable ASME Code Edition and Addenda The ASME Code,Section XI, 2001 Edition with 2003 Addenda is the applicable Code of record for the current fourth 10-year inservice inspection interval at AN0-2.

3.3 ASME Code Requirements Articles IWC-3120 and IWC-3130 of the ASME Code,Section XI, require that flaws exceeding the defined acceptance criteria be corrected by repair/replacement activities or be evaluated and accepted by analytical evaluation. Article IWD-3120(b) of the ASME Code,Section XI, requires that components whose examination reveals flaws that do not meet the standards of IWD-3400 shall be subjected to supplemental examination, or to a repair/replacement activity.

3.4 Duration of Request The licensee stated that it will complete an ASME Code,Section XI compliant repair/

replacement prior to startup from the next refueling outage (fall of 2015) or prior to exceeding the structural limits identified by the evaluation as approved by this relief request, or prior to a leak rate greater than 5 gallons per minute {gpm), whichever occurs first.

3.5 Proposed Alternative and Basis for Use On October 20, 2014, the licensee identified leakage in a dissimilar metal weld between an 18-inch, standard wall thickness, by 6-inch schedule 40 carbon steel sweep-o-let, and a 6-inch schedule 40 stainless steel 45-degree elbow on the SW piping to the suction of the "B" EFW pump, which is located in the Auxiliary Building. The subject piping forms a branch connection, via a sweep-o-let, with the main SW header.. The licensee stated that the leak rate at the time of discovery was 1 to 2 drops per hour but developed to 32 drops per hour at the time of the relief request submittal. The licensee also stated that the size of the pinhole was too small to measure at 32 drops per hour.

The licensee characterized the flaw as nonplanar, and as a single flaw with respect to the proximity of other thinned regions of the piping. The licensee stated that the flaw is located in the toe of the weld on the sweep-o-let (carbon steel) side of the weld, with the weld material being ER309/E309, having a yield strength of 57 ksi and an ultimate tensile strength.of 86 ksi.

The licensee also stated that the remaining piping beyond the flaw is sufficient to maintain a pressure-retaining boundary and postulated leakage does not exceed operability margins. The licensee determined that the nonplanar indication is the result of microbiological induced .

corrosion. According to the licensee, such corrosion indications are historically limited to*

localized areas on AN0-2 SW piping and piping components and do not manifest in general thinning, cracking, or other prompt structural failure precursors. The licensee stated that the isolated corrosion area can be reliably monitored to ensure flow and structural integrity is 1

maintained.

In its relief request, as supplemented, the licensee stated that ASME Code Case N-513-3 is conditionally acceptable to the NRC per Regulatory Guide (RG) 1.147, "lnservice Inspection Code Case Acceptability, ASME Section XI, Division 1," Revision 17, dated August 2014 (ADAMS Accession No. ML13339A689). However, N-513-3 does not allow evaluation of flaws located away from attaching circumferential piping welds which are in elbows, bent pipe, reducers, expanders, and branch tees. ASME Code Case N-513-4, recently endorsed by the ASME in May 2014, provides guidance for evaluation of flaws in these locations. Code Case N-513-4 has not been generically approved by the NRC via RG 1.147.

In lieu of repairing the degraded weld at the elbow in accordance with the ASME Code,Section XI, IWD-3120(b), the licensee proposed to follow the requirements of Code Case N-513-3 associated with the identified condition, with the exception that it proposed to use the methodology from Code Case N-513-4 to evaluate the structural integrity of the degraded elbow/weld.

• 3.6 Basis for Hardship In the event of an emergency, the SW system can be the supply source for the EFW system per AN0-2 Technical Specification (TS) 3.7.1.3, "Condensate Storage Tank." The design pressure for the SW system is 150 pounds per square inch gauge and the design temperature is 130 degrees Fahrenheit. AN0-2 TS 3.7.3, "Service Water System," requires that two SW loops be operable and powered from independent essential buses to provide redundant and independent flow paths in Modes 1, 2, 3, and 4. AN0-2 TS 3.7.4 requires the Emergency Cooling Pond (ECP) to be operable in Modes 1; 2, 3, and 4. Two EFW pumps and associated

flow paths are to remain operable in Modes 1, 2, and 3 in accordance with TS 3.7.1.2, "Emergency Feedwater System."

. The licensee stated that on October 30, 2014, Loop 1 of SW and EFW pump 2P-78 were declared inoperable and the appropriate TS actions were entered. The licensee further stated that immediate repair or replacement of the pipe is not feasible during this limiting condition of operation (LCO). The inoperable loop is required to be restored within 72 hours3 days <br />0.429 weeks <br />0.0986 months <br /> or the unit must be placed in Hot Shutdown within 6 hours0.25 days <br />0.0357 weeks <br />0.00822 months <br /> and Cold Shutdown within the following 30 hours1.25 days <br />0.179 weeks <br />0.0411 months <br /> per TS 3.7.3.

The licensee stated that without approval of this relief, AN0-2 will be required to shut down following expiration of the allowable outage time and result in hardship without a compensating increase in the level of quality and safety.

3. 7 NRC Staff Evaluation

• The NRC staff reviewed the licensee's flaw evaluation, monitoring of the flaw, extent of condition, flooding analysis, and basis for hardship to determine acceptability of the relief request. The NRC staff has not approved Code Case. N-513-4 in Regulatory Guide 1.147, Revision 17. Therefore, the NRC staff evaluates the proposed alternative based on Code Case N-513-3 and on the flaw calculation methodology of the ASME Code,Section XI, Appendix C. * *

~. 7 .1 Flaw Evaluation The licensee modeled the pinhole as a planar flaw and performed a linear-elastic fracture mechanics calculation (included as Attachment 2 to the licensee's October 31, 2014, submittal) to demonstrate the structural integrity of the degraded elbow and weld. The licensee performed a structural evaluation using the methodology of Code Case N-513-4 for the degraded elbow, using conservative allowable stress values based upon carbon steel materials with the highest moments applied. Using the stress intensity factor of the flaw and the pipe material, the licensee has demonstrated that the pipe material has sufficient toughness to resist sudden propagation of the flaw in an unstable manner. The licensee calculated an allowable flaw size of 2.7 inches in the circumferential direction and 5.8 inches in the axial direction. Based on its independent calculations, the NRC staff concludes that the allowable flaw sizes are acceptable and that the flaw will not propagate uncontrollably.

The licensee provided measured wall thickness of the degraded elbow. Based on an independent calculation, the NRC staff concludes that the elbow, except at the pinhole area, satisfies the minimum required wall thickness in accordance with the ASME Code, Section 111, Article ND-3640.

In its relief request, as supplemented, the licensee stated that it will implement a leak rate limit of 5 gpm. If the pinhole leak rate exceeds 5 gpm, the licensee will repair the subject piping. In addition, the licensee will monitor the degraded area periodically as discussed in Section 3.7.2*

below to provide additional assurance of the structural integrity of the subject piping.

The NRC staff concludes that the licensee has demonstrated an allowable leak rate, which will ensure that propagation of the flaw will be addressed in a timely manner, before the pinhole would challenge the structural integrity of the subject piping during the effective period of the relief request.

3.7.2 Monitoring of the Flaw The li.censee stated that it will monitor the pinhole in a daily walk-down to confirm the analysis conditions used in the flaw evaluation. This is *consistent with Paragraph 2(f) of ASME Code Case N-513-3, which has been accepted by the NRC, and is, therefore, acceptable. The licensee also stated that it will perform periodic inspections at no more than 30-day intervals to determine if the flaws are growing. This inspection is consistent with Paragraph 2(e) of ASME Code Case N-513-3 and is, therefore, acceptable. The NRC staff notes that should the pinhole size grow to be unacceptable, Paragraph 2(g) of ASME Code Case N-513-3 requires that a repair or replacement be performed.

3.7.3 Extent of Condition The licensee stated that it will perform augmented volumetric examinations at five of the most susceptible and accessible locations based upon similar geometry and similar material properties. Based on information provided by the licensee, the NRC staff concludes that the licensee has satisfied the extent of condition inspection requirements of ASME Code Case N-513-3.

3.7.4 Flooding Analysis The licensee stated that the leakage, at the time of the relief request, is insignificant and does not present a flooding concern and that there is no equipment susceptible to water damage under or adjacent to the leakage site. A floor drain located nearby the leak is sufficient in size to remove leakage addressed by this request. The subject elbow is located in a well-lighted area in the Auxiliary Building that is frequented by personnel on rounds. Should the leak rate increase to beyond the allowable leak rate of 5 gpm, the licensee is required to repair or replace the degraded elbow in accordance with the ASME Code,Section XI. Therefore, the NRC staff concludes that the licensee's flooding analysis is acceptable.

3. 7.5 Hardship Justification The NRC staff concludes that the shutdown of AN0-2 to repair the subject piping would be a hardship, based on the insignificant leak rate and the evaluation supporting the structural integrity of the subject piping for the duration of the proposed alternative. The pinhole leak caused AN0-2 to enter into a number of TS LCOs, as discussed in Section 3.6 of this SE, which would have led to shutdown of the unit on a relatively short timeframe, unless repairs were completed. The NRC staff further concludes that the leakage is small and that the piping elbow maintains its structural integrity based on the flaw evaluation, periodic monitoring, and an allowable leak rate. Therefore, the NRC staff concludes that no compensating increase in the level of quality and safety would be gained by performing an ASME Code repair at the time of discovery of the leakage.

4.0 CONCLUSION

Based on the above, the NRC concludes that the licensee has demonstrated that Relief Request AN02-ISl-017 will provide reasonable assurance that the structural integrity of the subject SW piping and its intended safety function will be maintained for the duration of the relief. The NRC staff concludes that complying with IWD-3120(d) ofthe ASME Code,Section XI, would result in a hardship without a compensating increase in the level of quality and safety. 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 relief request AN02-ISl-017 at AN0-2, until the end of the fall 2015 refueling outage, the time at which the pinhole exceeds the allowable flaw size, or the time at which the leak rate exceeds the allowable leak rate, whichever event occurs first.

All other requirements of the ASME Code,Section XI, for which relief has not been specifically requested and authorized by NRC staff remain applicable, including a third-party review by the Authorized Nuclear lnservice Inspector.

Principal Contributor: John Tsao Date: March 16, 2015

• ML15070A428 *via email OFFICE NRR/DORL/LPL4-1 /PM NRR/DORL/LPL4-1/LA NRR/DE/EPNB/BC NRR/DORL/LPL4-1/BC NAME AGeorge JBurkhardt* DAiiey* MMarkley DATE 3/16/15 3/12/15 12/15/14 3/16/15