ML21054A330

Approval of Alternative IP3-ISI-RR-16 to American Society of Mechanical Engineers Code Case N-513-4 Inspection Requirement

ML21054A330
Person / Time
Site:	Indian Point
Issue date:	02/24/2021
From:	James Danna NRC/NRR/DORL/LPL1
To:	Entergy Nuclear Operations
Guzman R
References
EPID L-2021-LLR-0013
Download: ML21054A330 (9)

Text

February 24, 2021 Vice President, Operations Entergy Nuclear Operations, Inc.

Indian Point Energy Center 450 Broadway, GSB P.O. Box 249 Buchanan, NY 10511-0249

SUBJECT:

INDIAN POINT NUCLEAR GENERATING UNIT NO. 3 - APPROVAL OF ALTERNATIVE TO AMERICAN SOCIETY OF MECHANICAL ENGINEERS CODE CASE N-513-4 INSPECTION REQUIREMENT (EPID L-2021-LLR-0013)

Dear Sir or Madam:

By letter dated February 10, 2021 (Agencywide Documents Access and Management System Accession No. ML21041A509), Entergy Nuclear Operations, Inc. (Entergy, the licensee) submitted a proposed one-time alternative to the requirements of the American Society of Mechanical Engineers Boiler and Pressure Vessel Code (ASME Code),Section XI paragraph IWD-2500 and Table IWD-2500-1 for Indian Point Nuclear Generating Unit No. 3 (Indian Point 3).

Specifically, pursuant to Title 10 of the Code of Federal Regulations (10 CFR) 50.55a(z)(2), the licensee requested to use proposed alternative IP3-ISI-RR-16 on the basis that complying with the specified requirement would result in hardship or unusual difficulty without a compensating increase in the level of quality and safety.

The U.S. Nuclear Regulatory Commission (NRC) staff has reviewed the subject request and concludes, as set forth in the enclosed safety evaluation, that the licensee has adequately addressed all of the regulatory requirements set forth in 10 CFR 50.55a(z)(2).

The licensee performed a Code Case N-513-4 evaluation to accept a through-wall leak in a service water line that was discovered on December 10, 2020. The licensee installed a clamp that encapsulated the area of the leak and reduced the leakage rate from the initial 15 gallons per minute leak rate at time of discovery to 1.5 gallons per minute. Code Case N-513-4 paragraph 2(e) requires performance of periodic inspections at not more than 90-day intervals to verify flaw growth analysis predictions.

The NRC authorizes the use of the proposed alternative in IP3-ISI-RR-16 for Indian Point 3, through May 10, 2021, or until a leak rate from the flaw exceeds 200 gallons per minute, whichever occurs first. The alternative extends the time to perform the periodic inspection from 90 days to 150 days. 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 Inservice Inspector.

If you have any questions concerning this matter, please contact the Indian Point 3 Project Manager, Richard Guzman, at (301) 415-1030 or Richard.Guzman@nrc.gov.

Sincerely, Digitally signed by James G. James G. Danna Date: 2021.02.24 Danna 14:36:27 -05'00' James G. Danna, Chief Plant Licensing Branch I Division of Operator Reactor Licensing Office of Nuclear Reactor Regulation Docket No. 50-286

Enclosure:

Safety Evaluation cc: Listserv

SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELIEF REQUEST IP3-ISI-RR-16 ALTERNATIVE TO AMERICAN SOCIETY OF MECHANICAL ENGINEERS CODE CASE N-513-4 INSPECTION REQUIREMENT ENTERGY NUCLEAR OPERATIONS, INC.

INDIAN POINT NUCLEAR GENERATING UNIT NO. 3 DOCKET NO. 50-286

1.0 INTRODUCTION

By letter dated February 10, 2021 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML21041A509), Entergy Nuclear Operations, Inc. (Entergy, the licensee) submitted a proposed a one-time alternative to the requirements of the American Society of Mechanical Engineers Boiler and Pressure Vessel Code (ASME Code),Section XI paragraph IWD-2500 and Table IWD-2500-1 for Indian Point Nuclear Generating Unit No. 3 (IP3 or Indian Point 3 ).

Specifically, the licensee requested a one-time relaxation of the Code Case N-513-4 paragraph 2(e) requirement to perform periodic inspections at not more than 90-day intervals to allow the first periodic inspection no later than 150 days from the time of discovery. This relaxation would eliminate the need to remove the currently installed leak mitigation clamp for the purpose of performing the 90-day examination. Pursuant to Title 10 of the Code of Federal Regulations (10 CFR) 50.55a(z)(2)), the licensee requested to use the proposed alternative in Relief Request IP3-ISI-RR-16 on the basis that performing the 90-day periodic examination would result in hardship or unusual difficulty without compensating increase in the level of quality and safety.

2.0 REGULATORY EVALUATION

The regulation at 10 CFR 50.55a(z) states, in part, that alternatives to the requirements of paragraphs (b) through (h) of 10 CFR 50.55a or portions thereof 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 applicant or licensee must demonstrate that:

(1) Acceptable level of quality and safety. The proposed alternative would provide an acceptable level of quality and safety; or

(2) Hardship without a compensating increase in quality and safety.

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 use of the proposed alternative.

3.0 TECHNICAL EVALUATION

3.1 ASME Code Component(s) Affected The affected component is the Class 3 IP3 service water (SW) line 1093 which provides cooling to the central control room air conditioners and the emergency diesel generators (EDGs) lube oil and jacket water heat exchangers. Specifically, the applicable ASME Code,Section XI, examination categories and item numbers affecting the SW pipe are from IWD-2500 and Table IWD-2500-1: Examination Category D-B, All Pressure Retaining Components, Item No. D2.10.

3.2 Applicable Code Edition and Addenda The ASME Code,Section XI, 2007 Edition through the 2008 Addenda is the Code of Record for the fourth 10-year inservice inspection (ISI) interval.

3.3 Applicable Code Requirement Paragraph IWD-2500 of ASME Boiler and Pressure Vessel Code,Section XI and Table IWD-2500-1 require pressure-retaining components be pressure tested with a system leakage test and a VT-2 visual examination for leakage. Acceptance standards of IWD-3000 do not allow any through-wall or through-weld pressure-retaining material leakage and provide rules for analytical evaluation of such flaws. ASME Section XI Code Case N-513-4, Evaluation Criteria for Temporary Acceptance of Flaws in Moderate Energy Class 2 or 3 Piping, provides analytical evaluation rules for temporary acceptance of through-wall flaws in moderate energy Class 2 and 3 piping. The licensee performed a Code Case N-513-4 evaluation to accept a through-wall leak in the Class 3 10-inch SW line 1093 which was discovered on December 10, 2020. Code Case N-513-4 paragraph 2(e) requires performance of periodic inspections at not more than 90-day intervals to verify flaw growth analysis predictions when a flaw growth analysis was performed in accordance with the case.

3.4 Proposed Alternative The licensee proposed a one-time relaxation of the Code Case N-513-4 paragraph 2(e) requirement to perform periodic inspections at no more than 90-day intervals to allow the first periodic inspection no later than 150 days from the time of discovery. This relaxation would eliminate the need to remove the currently installed leak mitigation clamp for the purpose of performing the 90-day examination. The extension would allow IP3 to continue to operate until its permanent cessation of operations, which is currently scheduled to be April 30, 2021, without the additional periodic inspections beyond the daily operator rounds currently being performed.

The licensee proposed that performing the 90-day periodic examination would result in hardship or unusual difficulty without compensating increase in the level of quality and safety under

paragraph 10 CFR 50.55a(z)(2). Specifically, the licensee stated that performance of periodic inspections required by Code Case N-513-4 could result in a safety concern for the nondestructive examination (NDE) personnel and potentially impact the performance of the NDE equipment. In addition, activities required for performing additional examinations may further degrade the condition of the component such that the periodic inspection cannot be completed. The licensee stated this would result in an unplanned plant shutdown prior to the permanent plant shutdown on April 30, 2021, even though the affected location has significant structural margin beyond that required by the code case.

3.5 Basis for Use The licensee indicated that a one-time extension of the first periodic inspection from 90 days to 150 days is acceptable and does not result in a decrease in the level of quality and safety, based on the following:

(1) The periodic inspections required by the Code Case have no impact on the structural capability of the pipe but are intended to confirm the accuracy of the assumptions and inputs used in the Code Case evaluations. Since there is significant margin between the measured and the allowable flaw sizes, the additional 60 days requested beyond the ASME Code Case N-513-4 required due date is considered acceptable as structural integrity of the pipe will still be maintained.

(2) Since the applied stresses resulting from the normal operating and design bases loads are low in the affected area, there is significant margin between the Code Case N-513-4 calculated allowable flaw sizes and the amount of degradation measured during the original inspection.

(3) Calculations performed in accordance with section 3.2, Nonplanar Flaws in Straight Pipe, from Code Case N-513-4 have demonstrated that the degraded area will remain within the structural limits provided in the Code Case beyond the date for permanent cessation of IP3 operations (i.e.,

April 30, 2021, which is within the 150-day period requested). This is based on the FEA [finite element analysis] which evaluated a 4.4 inch circumferential by 3 inch axial hole, which bounds the as-measured thinning of 3 inches in the circumferential direction by 1.375 inches in the axial direction. The resultant stress was 69% of the allowable stress.

(4) Since the degradation mechanism is on the OD [outside diameter] of the pipe, it was accurately characterized during the previous inspection and is well understood. Based on the UT [ultrasonic testing] results and past internal inspections of the pipe, there is no evidence of any active internal degradation of the surrounding area.

(5) The affected location is being monitored by daily operator rounds, as required by Code Case N-513-4. Thus far, this monitoring has indicated no discernable change in the leakage around the clamp.

(6) The leak is located in the EDG valve room below the floor grating, which is treated as a confined spaced. There is no sensitive equipment in the vicinity of the leak which could be impacted by the spray.

(7) A hydraulic analysis of the system indicated that the SW system would remain capable of performing its intended cooling function under limiting design bases conditions with a leak up to 200 gpm [gallons per minute].

This assures significant margin between the original leak and the maximum expected leak if the current leak mitigation clamp were to fail.

(8) A flooding evaluation was also performed for the EDG building where the leak is located. A review of the available drainage in the location of the leak indicated that the capacity of the drainage system far exceeds a 200 gpm postulated leak and therefore flooding of the area as a result of the SW leak is not a concern, relative to the ability of the system to perform its intended design basis functions.

3.6 Duration of Proposed Alternative The licensees request is applicable to Entergys ISI program for the IP3 fourth 10-year interval, which is scheduled to extend through April 30, 2021.

4.0 NRC STAFF EVALUATION The NRC staff has evaluated Relief Request IP3-ISI-RR-16 pursuant to 10 CFR 50.55a(z)(2).

Specifically, the NRC has reviewed flaw characterization, leak rate monitoring, system operability, structural integrity, flooding evaluation, and hardship justification in the proposed alternative as follows.

Flaw Characterization The NRC noted that the through-wall hole is approximately 0.375 inches in diameter. The NRC staff finds acceptable the licensees characterization of the extent of the external corrosion on SW line 1093 using ultrasonic examinations and physical measurements. The licensee characterized the through-wall flaw as a non-planar flaw. The licensee was able to accurately characterize the wall thickness of the pipe adjacent to the through-wall hole to determine the length and depth of the corrosion near the hole. The external corrosion was characterized as two separate wall thinning areas. The first containing the 0.375-inch diameter through-wall flaw is 1.375 inches in the axial direction by 2 inches in the circumferential direction. The second area adjacent to the leak is 1 inch by 1 inch.

ASME Code,Section XI, IWA-3300 requires pipe degradation be characterized or sized in terms of a rectangle or square that fully contains the area of the flaw. Based on IWA-3300, the licensee combined the two thinned areas into a single flaw and characterized the single flaw as being 3 inches in the axial direction and 1.375 inches in the circumferential direction. The NRC staff finds that the licensee appropriately characterized the flaw based on the ASME Code,Section XI, IWA-3300.

Leak Rate Monitoring As required by Code Case N-513-4, the licensee plans to monitor the leak rate from the SW line 1093 on a daily basis. These assessments will monitor the leak rate and spray pattern from the leakage around the clamp installed around the leaking flaw. If changes in flow rate or spray pattern are identified, they will be evaluated, and corrective actions taken if necessary to ensure structural integrity and system flow requirements continue to be met. The NRC staff finds these

monitoring activities will provide reasonable assurance that structural integrity and system flow requirements will continue to be met.

System Operability The licensee stated that a hydraulic analysis of the SW system demonstrated that it would remain capable of performing its intended safety function under limiting design conditions with a leak up to 200 gpm. The licensee has installed a non-Code housekeeping clamp which encapsulated the area of the leak and has reduced the leakage rate from the initial 15-gpm leak rate at time of discovery to 1.5 gpm. For the leak to grow to 200 gpm, it would require the through-wall flaw to increase to approximately 0.85 inches in diameter. Using the average corrosion rate experienced on the SW system piping at IP3, the though-wall flaw is projected to potentially increase in diameter to 0.385 inches. At this size, the leak rate, if unmitigated, would be well below the 200 gpm operability limit. With the leak mitigated using the housekeeping clamp, the leak is expected to remain at the present rate of 1.5 gpm. Therefore, the NRC staff finds that the operability and functionality of the degraded SW system piping will not be significantly affected.

Structural Integrity The licensee evaluated the degraded SW line 1093 in accordance with ASME Code Case N-513-4 and derived an allowable through-wall flaw of size 3 inches in the axial direction and 4.4 inches in the circumferential direction. The allowable flaw size bounds the characterized flaw size of 1.375 inches in the axial direction and 3 inches in the circumferential direction. As such, the NRC staff finds that the piping will remain stable under all design-basis loading conditions. The NRC staff notes that the leak was discovered on December 10, 2020.

The NRC staff does not expect the flaw to grow aggressively during the 150-day period before performing the first reinspection as requested by the licensees alternative. The NRC staff finds that the licensees flaw evaluation has adequately demonstrated structural integrity of SW line 1093.

Flooding Evaluation The licensee stated there is no equipment in the area sensitive to water spray from the leakage, and that the floor drainage system capability exceeds the 200-gpm leak rate that would cause system to become inoperable. The leak mitigating housekeeping clamp the licensee has installed has reduced the leak rate to approximately 1.5 gpm. The NRC staff finds that no safety-related components or equipment will be affected by the leakage due to the pipes location below the floor grating and near the floor of the room that contains the SW system piping. If the flaw does grow unexpectedly, the licensee will detect the growth during the daily monitoring and will take corrective actions. Therefore, the NRC staff finds that flooding in the area where the leaking piping is located is not a safety concern.

Hardship Justification The NRC staff finds that performing the 90-day periodic inspection of the degraded SW system line 1093 piping poses difficulty due to requiring the removal of the leak mitigating clamp, the possibility of needing to perform surface preparation prior to the examination, and the degraded pipes location in an area considered a confined space. Removal of the leak mitigating clamp would allow the leakage rate to increase which could possibly affect the ultrasonic examination equipment and cause increased hazards for examination personnel. If additional surface

preparation is necessary to perform the inspection, this could increase the size of the through-wall flaw, therefore increasing the leak rate. The NRC staff notes that the extension of the periodic inspection to 150 days would move the inspection past the date of the next IP3 outage currently scheduled for April 30, 2021. The NRC staff notes that the licensee has demonstrated that the leaking SW line 1093 piping will maintain reasonable assurance of structural integrity for the limited duration of this alternative. Therefore, the NRC staff finds that complying with the specified ASME Code requirement of the degraded SW line 1093 piping would result in hardship or unusual difficulty without a compensating increase in the level of quality and safety.

Based on information provided, the NRC staff finds that: (1) there is adequate margin between the size of the existing flaws and the allowable flaw size for the SW line 1093 piping; (2) the existing flaws are reasonably expected to be stable and not growing significantly for the period of the requested alternative; (3) the leak rate from the existing flaws is less than the allowable leak rate, thus the SW system is capable of performing its intended function; (4) the daily monitoring is acceptable to identify changes in leak rate and/or potential flaw growth; and (5) the licensees hardship justification is acceptable. Therefore, the NRC staff finds that the proposed alternative will provide reasonable assurance that structural integrity of SW line 1093 will be maintained until for the duration of this alternative.

5.0 CONCLUSION

As set forth above, the NRC staff has determined that complying with the specified requirements described in the licensees relief request IP3-ISI-RR-16 referenced above would result in hardship or unusual difficulty without a compensating increase in the level of quality and safety. The proposed alternative provides reasonable assurance of structural integrity of the subject 10-inch SW line 1093 at Indian Point 3. Accordingly, the NRC staff concludes that the licensee has adequately addressed the regulatory requirements set forth in 10 CFR 50.55a(z)(2) for the proposed alternative. Therefore, the NRC staff authorizes the use of proposed alternative IP3-ISI-RR-16 for Indian Point 3 through May 10, 2021 or, until a leak rate from the flaw exceeds 200 gpm, whichever occurs first.

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

Principal Contributor: K. Hoffman, NRR Date: February 24, 2021

ML21054A330 OFFICE NRR/DORL/LPL1/PM NRR/DORL/LPL1/LA NRR/DNRL/NPHP/BC NRR/DORL/LPL1/BC NAME RGuzman JBurkhardt MMitchell JDanna DATE 02/24/2021 02/24/2021 02/23/2021 02/24/2021