ML041840169
| ML041840169 | |
| Person / Time | |
|---|---|
| Site: | Farley  |
| Issue date: | 06/25/2004 |
| From: | Stephanie Coffin NRC/NRR/DLPM/LPD2 |
| To: | Stinson L Southern Nuclear Operating Co |
| Peters, S, NRR/DLPM/301-415-1842 | |
| References | |
| TAC MC2211, TAC MC2212 | |
| Download: ML041840169 (13) | |
Text
June 25, 2004 Mr. L. M. Stinson Vice President - Farley Project Southern Nuclear Operating Company, Inc.
Post Office Box 1295 Birmingham, Alabama 35201-1295
SUBJECT:
JOSEPH M. FARLEY NUCLEAR PLANT, UNITS 1 AND 2 - REQUEST FOR RELIEF NO. 55 FROM ASME CODE REPAIR REQUIREMENTS FOR ASME CODE CLASS 3 SERVICE WATER SYSTEM PIPING (TAC NOS. MC2211 AND MC2212)
Dear Mr. Stinson:
By letter dated February 23, 2004, Southern Nuclear Operating Company, Inc., the licensee, requested relief from the American Society of Mechanical Engineers (ASME) Code,Section XI requirements, pursuant to Title 10 of the Code of Federal Regulations (10 CFR)
Section 50.55a(g)(6)(i), to repair flaws in the Service Water System piping, at the Joseph M.
Farley Nuclear Plant (FNP), Unit 1 and 2. The licensee based its request for relief on the results of a flaw evaluation that it performed in accordance with the guidelines and acceptance criteria contained in Generic Letter 90-05. The licensee will repair the affected section of pipe during the next cold shutdown greater than 30 days or at the latest, Refueling Outage 1R19 scheduled for October 2004.
Under the provisions of 10 CFR 50.55a, the licensee requested relief to allow temporary non-Code repairs of an FNP, Unit 1 through-wall pinhole leak on a section of piping that provides the backup Service Water to the 1B motor-driven Auxiliary Feedwater pump and of an FNP, Unit 2 through-wall pinhole leak on a section of piping that provides Service Water makeup to the Circulating Water canal. Both sections of piping are ASME Code Class 3 piping.
The Nuclear Regulatory Commission (NRC) staff has reviewed the information provided for this relief request. The NRC staffs Safety Evaluation is provided in the Enclosure. The NRC staff
L. M. Stinson concludes that compliance with the specified requirements would result in hardship without a compensating increase in the level of quality and safety. Therefore, the licensees proposed alternative to the ASME Code requirements is authorized pursuant to 10 CFR 50.55a(a)(3)(ii) until each units next cold shutdown greater than 30 days or at the latest, Refueling Outage 1R19 scheduled for October 2004.
Sincerely,
/RA/
Stephanie M. Coffin, Acting Chief, Section 1 Project Directorate II Division of Licensing Project Management Office of Nuclear Reactor Regulation Docket Nos. 50-348 and 50-364
Enclosure:
As stated cc w/encl: See next page
ml041840169 *No Major Changes to SE OFFICE PDII-1/PM PDII-1/ PM PDII-1/(A)LA EMCB*
OGC**
PDII-1/(A)SC NAME ZCruz SPeters DClarke TChan GLongo SCoffin DATE 6/18/04 6/12/04 6/24/04 04/05/04 06/07/04 6/24/04
Enclosure SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION REQUEST FOR RELIEF FROM ASME CODE REPAIR REQUIREMENTS FOR ASME CODE CLASS 3 PIPING JOSEPH M. FARLEY NUCLEAR PLANT, UNITS 1 AND 2 SOUTHERN NUCLEAR OPERATING COMPANY, INC.
DOCKET NOS. 50-348 AND 50-364
1.0 INTRODUCTION
By letter dated February 23, 2004, Southern Nuclear Operating Company, Inc. (SNC, the licensee), requested relief from the American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code (Code),Section XI repair or replacement requirements under the provisions of Title 10 of the Code of Federal Regulations (10 CFR) Section 50.55a(g) at Joseph M. Farley Nuclear Plant (FNP), Units 1 and 2. The licensee based its request for relief on the results of a flaw evaluation that it performed in accordance with the guidelines and acceptance criteria contained in Generic Letter (GL) 90-05. The licensee will repair the affected section of pipe during the next cold shutdown greater than 30 days or at the latest, Refueling Outage 1R19 scheduled for October 2004.
Under the provisions of 10 CFR 50.55a, the licensee requested relief to allow temporary non-Code repairs of an FNP, Unit 1 through-wall pinhole leak on a section of piping that provides the backup service water to the 1B motor-driven auxiliary feedwater pump (MDAFP) and of an FNP, Unit 2 through-wall pinhole leak on a section of piping that provides service water makeup to the circulating water canal. Both sections of piping are ASME Code Class 3 piping.
2.0 REGULATORY EVALUATION
2.1 Background
On November 1, 2003, the licensee discovered a through-wall leak in the service water system (SWS) of FNP, Unit 1. The leak is located upstream of motor-operated valve MOV3209 in the carbon steel 8-inch supply line to the 1B MDAFWP. The leak is located between MOV3209 and the feed to the MDAFWP room cooler, about 15 feet above the pump. The pinhole leak is located in the lower section of the pipe weld cap about a tenth of an inch from the edge. The leak rate was approximately 40 drops per minute (dpm).
On November 16, 2003, a through-wall leak was discovered in the SWS of FNP, Unit 2. The leak is located in the carbon steel 20-inch piping of the service water makeup to the circulating water canal, in valve box 2VB-3. The location is in the weld joining the downstream flange of valve Q2P I 6V560 to a short pipe section which then goes to the 20-inch/30-inch reducer. The leak rate was approximately 0.25 gallons per minute (gpm).
2.2 Applicable Requirements 10 CFR 50.55a(g) requires nuclear power facility piping and components to meet the applicable requirements of Section XI of the ASME Code.Section XI of the Code specifies Code-acceptable repair methods for flaws that exceed Code acceptance limits in piping that is in-service. A Code repair is required to restore the structural integrity of flawed Code piping, independent of the operational mode of the plant when the flaw is detected. Those repairs not in compliance with Section XI of the Code are non-Code repairs. However, the implementation of required Code (weld) repairs to ASME Code Class 1, 2 or 3 systems is often impractical for nuclear licensees since the repairs normally require isolation of the system requiring the repair and often shutdown of the nuclear power plant.
Pursuant to 10 CFR 50.55a(a)(3), proposed alternatives to the ASME Code requirements can be used when authorized by the Nuclear Regulatory Commission (NRC) if the licensee demonstrates that: (i) the proposed alternative 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.
A licensee may also submit requests for relief from certain Code requirements when a licensee has determined that conformance with certain Code requirements is impractical for its facility
[10 CFR 50.55a(g)(5)(iii)]. Pursuant to 10 CFR 50.55a(g)(6)(i), the Commission will evaluate determinations of impracticality and may grant relief and may impose 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 giving due consideration to the burden upon the licensee that could result if the requirements were imposed on the facility.
Generic Letter (GL) 90-05, entitled "Guidance for Performing Temporary Non-Code Repair of ASME Code Class 1, 2 and 3 Piping," dated June 15, 1990, provides guidance for the NRC staff in evaluating relief requests submitted by licensees for temporary non-Code repairs of Code Class 3 piping. For the purpose of this letter, impracticality 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 the repair within the time period permitted by the limiting condition for operation (LCO) of the affected system as specified in the plant technical specifications and performance of Code repair necessitates a plant shutdown.
3.0 LICENSEES RELIEF REQUEST FOR FNP, UNIT1 3.1 Components for Which Relief is Requested ASME Code Class 3 SWS piping (one 8-inch Nominal Pipe Size (NPS) carbon steel pipe).
3.2 ASME Section XI Code Requirement The ASME Code Section XI requires that repairs or replacements of ASME Code Class components be performed in accordance with rules found in the Code. The Code rules serve to provide an acceptable means of restoring the structural integrity of a degraded Code Class system back to the original design requirements.
3.3 Licensee Basis for Relief Flaw Detection During Plant Operation and Impracticality Determination On November 1, 2003, a through-wall leak was discovered in the Service Water system. The leak is located upstream of MOV3209 in the carbon steel 8-inch supply line to the 1B MDAFW. The leak is located between MOV3209 and the feed to the MDAFW pump room cooler and is located about 15 feet above the pump. The pinhole leak is located in the lower section of the pipe weld cap about a tenth of an inch from the edge. The leak rate was approximately 40 drops per minutes (dpm). The initial leakage is documented in FNP Condition Reports #2003002999 and #2003003034.
Repair of this location is not possible while the plant is in operation since no isolation valves exist between the leak location and the B-train Service Water supply header to the Auxiliary Building.
Root Cause Determination and Flaw Characterization The root cause for the piping degradation is considered to be due to microbiological induced corrosion (MIC). Experience from the Service Water Radiography (RT) program indicates a propensity for MIC attack to occur in the sensitized areas of welds. The RT shows non-cracklike rounded and/or irregularly shaped indications characteristic of MIC.
The flaw is located very close to the base metal/weld interface on the pipe side of the pipe to elbow weld. The exterior size of the pinhole was 1/16-inch diameter. The RT film showed the flaw to be irregular in shape through the wall thickness. The overall dimensions taken from the RT film are 0.277-inch in the axial direction and 0.481-inch in the circumferential direction. Volumetric examination of this weld detected other indications: (1) at approximately 6-inches from the original through wall flaw, a flaw of 0.385-inch diameter was found and assumed to be encroaching on the ASME minimum wall; (2) at approximately 12-inches from the original through wall flaw, a flaw of 0.442-inch diameter was found and assumed to be encroaching on the ASME minimum wall; and (3) at approximately 1-inch circumferentially and 2-inches axially away from the original flaw, a base metal spot flaw of 0.113-inch wall thickness and having a diameter less than the original flaw was found.
Flaw Evaluation Since a through-wall flaw had been found at this location, SNC chose to perform the evaluation on that basis.
A combination of volumetric (radiography and ultrasonic) examinations were performed on the flaw. This information was used to perform the structural integrity calculation required by GL 90-05 by the through-wall method. The results of this evaluation show that the largest calculated stress intensity factor "K" of 34.64 ksi(in)exp(1/2) is less than the 35 ksi(in)exp(1/2) acceptance criteria for carbon steel.
Engineering personnel reviewed the design requirements for this system and have determined that this amount of leakage does not prevent it from performing its safety function. This will not have an impact to safety related equipment downstream of the leak since this is a back-up supply of water to the AFW system and is not normally used. The impact of this leakage on components in the area was also evaluated and it was determined that those components would not be adversely affected by leakage or spray. The existing leakage is being collected in a bucket; therefore, other components are not being affected by this leakage. Leakage is being monitored by the weekly walkdown of this area and appropriate action to prevent further leakage and spray will be taken as needed.
The current leak rate is not sufficient to cause a flood level that will affect any safety related component in less than a weeks time.
Based on the above, SNC determined that the structural integrity of the Service Water piping at this location has not been impaired.
Augmented Inspections The piping with the initial flaw is moderate energy piping and therefore, five other susceptible locations were chosen for the augmented volumetric examinations per GL 90-05. No flaws were detected by these examinations; thus, SNC has concluded that the initial leak is a localized condition.
3.4 Licensee Proposed Alternative In place of the ASME Code requirements, SNC is implementing the alternative requirements of NRC GL 90-05 until the next refueling outage or during a scheduled Unit 1 outage exceeding 30 days, whichever occurs first.
Based on the evaluation above, SNC requests relief from ASME Section XI Code. SNC plans to leave this piping "as is" with a banded rubber patch that will direct leakage to a container. The total weight of this patch is less than 20 pounds which is considered negligible from a pipe loading standpoint. The leakage is negligible and does not present a maintenance or operational problem. The GL 90-05 evaluation shows that this piping still has structural integrity. Based on the continued monitoring discussed below, SNC will reevaluate the need for additional housekeeping measures as appropriate.
An ASME Section XI repair or replacement will be performed before the completion of the FNP Unit 1 1R19 refueling outage or during a scheduled Unit 1 outage exceeding 30 days, whichever occurs first. The 1R19 outage is scheduled to begin in October 2004.
Two actions will be performed by SNC for this component until the ASME Section XI repair or replacement is performed.
Operations will perform a weekly qualitative assessment of leakage with the housekeeping patch installed to identify any degradation of structural integrity. If the leak rate increases significantly, an engineering evaluation will be performed to determine the need for additional action, including a re-assessment of structural integrity.
A follow-up volumetric examination will be performed on or before each three-month anniversary of the completion of the original examination until the repair or replacement is completed.
4.0 LICENSEES RELIEF REQUEST FOR FNP, UNIT 2 4.1 Components for Which Relief is Requested ASME Code Class 3 service water system piping (one 20-inch Nominal Pipe Size (NPS) carbon steel pipe).
4.2 ASME Section XI Code Requirement The ASME Code Section XI requires that repairs or replacements of ASME Code Class components be performed in accordance with rules found in the Code. The Code rules serve to provide an acceptable means of restoring the structural integrity of a degraded Code Class system back to the original design requirements.
4.3 Basis for Relief Flaw Detection During Plant Operation and Impracticality Determination:
On November 16, 2002, a through-wall leak was discovered in the Service Water system. The leak is located in the carbon steel 20-inch piping of the Service Water makeup to the Circulating Water canal, in valve box 2VB-3. The location is in the weld joining the downstream flange of valve Q2P16V560 to a short pipe section which then goes to the 20-inch/30-inch reducer. The leak rate was approximately 0.25 gallon per minute. The initial leakage is documented in Farley Condition Report #2002002791.
Repair of this location is not possible while the plant is in operation since the line supplies makeup water to the Circulating Water canal with a nominal flow rate of 10,000 gpm. No other sources of water are available to supply this amount of water with the unit in operation.
Root Cause Determination and Flaw Characterization The root cause for the piping degradation is considered to be due to microbiological induced corrosion (MIC). Experience from the Service Water Radiography (RT) program indicates a propensity for MIC attack to occur in the sensitized areas of welds. The RT shows a non-cracklike rounded shaped indication characteristic of MIC.
The flaw is located in the weld approximately 1/8-inch from the base metal/weld interface. The exterior size of the pinhole was 1/16-inch diameter. NDE
[Non-destructive examination] did not detect any other indications at the original flaw location. The RT indicated that the maximum dimension of the flaw was 0.332 inches and that it was a rounded indication. The flaw extended a short distance out of the weld into the sensitized area of the base metal.
Flaw Evaluation Since a through-wall flaw had been found at this location, SNC chose to perform the evaluation on that basis.
A combination of volumetric (radiography and ultrasonic) examinations were performed on the flaw. This information was used to perform the structural integrity calculation required by GL 90-05 by the through-wall method. The results of this evaluation show that the largest calculated stress intensity factor "K" of 12.54 ksi(in)exp(1/2) is less than the 35 ksi(in)exp(1/2) acceptance criteria for carbon steel.
Engineering personnel reviewed the design requirements for this system and have determined that this amount of leakage does not prevent it from performing its safety function. The impact of this leakage on the components in the valve box was also evaluated and it was determined that those components would not be adversely affected by leakage or spray. Due to the leakage occurring in a valve box, safety related components could be affected by flooding if the existing sump pump fails and the control room high water level alarm fails. This is being addressed by the weekly walkdown of the valve box. Appropriate action to prevent flooding and damage of the components will be taken at that point. The current leak rate is not sufficient to cause a flood level that will affect any safety related component in less than a weeks time.
Based on the above, SNC determined that the structural integrity of the Service Water piping at this location has not been impaired.
Augmented Inspections The piping with the initial flaw is moderate energy piping and therefore, five other susceptible locations were chosen in valve box 2VB-3 for the augmented volumetric examinations per GL 90-05. No flaws were detected by these examinations; thus, SNC has concluded that the initial leak is a localized condition.
4.4 Licensee Proposed Alternative In place of the ASME Code requirements, SNC is implementing the alternative requirements of NRC GL 90-05 until the next refueling outage or during a scheduled Unit 2 outage exceeding 30 days, whichever occurs first.
Based on the evaluation above, SNC requests relief from ASME Section XI Code. SNC plans to leave this piping "as is" with a banded rubber patch that will direct leakage to an existing floor drain. The total weight of this patch is less than 20 pounds which is considered negligible from a pipe loading standpoint.
The leakage is negligible and does not present a maintenance or operational problem. The GL 90-05 evaluation shows that this piping still has structural integrity. Based on the continued monitoring discussed below, SNC will reevaluate the need for additional housekeeping measures as appropriate.
An ASME Section XI repair or replacement will be performed before the completion of the FNP, Unit 2 2R16 refueling outage or during a scheduled Unit 2 outage exceeding 30 days, whichever occurs first. The 2R16 outage is scheduled to begin in March 2004.
The following action will be performed by SNC for this component until ASME Section XI repair or replacement is performed:
Operations will perform a weekly qualitative assessment of leakage with the housekeeping patch installed to identify any degradation of structural integrity. If the leak rate increases significantly, an engineering evaluation will be performed to determine the need for additional action, including a re-assessment of structural integrity.
A follow-up volumetric examination will be performed on or before each three-month anniversary of the completion of the original examination until the repair or replacement is completed.
5.0 TECHNICAL EVALUATION
5.1 Operability Determination, Root Cause Analysis and Structural Integrity Evaluation The licensee determined that the leaks are located in an 8-inch diameter carbon steel pipe in the SWS supply line to the 1B MDAFW located upstream of MOV3209 in FNP, Unit 1 and a 20-inch NPS carbon steel pipe in the SWS makeup to the circulating water canal, in valve box 2VB-3 in FNP, Unit 2. The leaks are located in the service water system which is classified as an ASME Code Class 3 system. At the time of discovery, the licensees system engineer determined that the leakage from the piping is approximately 40 dpm from the leak in FNP, Unit 1 and 0.25 gpm from the leak in FNP, Unit 2. The system engineer has also reviewed the design requirements for the system and concluded that this amount of leakage does not prevent it from performing its safety function. The impact of the leakage in FNP, Unit 1 from the pipe to the area was evaluated and determined that components in the area would not be adversely affected by leakage or spray. In FNP, Unit 2, safety-related components could be affected by flooding if the existing sump pump fails and the control room high water level alarm fails. However, weekly walkdowns of the valve box addressed this concern since the current leak rate is not sufficient to cause a flood level that will affect any safety-related component in less than a weeks time. SNC evaluated the leaks using the through-wall flaw approach provided in GL 90-05. The evaluation calculated the stress intensity factor K for the degraded piping to be 34.64 ksi(in)exp(1/2) for the leak in FNP, Unit 1 and 12.54 ksi(in)exp(1/2) for the leak in FNP Unit 2. GL 90-05 states that the K value should be less than 35 ksi(in)exp(1/2) for carbon steels. Since the calculated K value for the degraded piping is less than the limit of 35 ksi(in)exp(1/2) specified by GL 90-05, which is consistent with the ASME Code lower-bound fracture toughness criterion, the requirements for use of temporary non-Code repair are satisfied.
The licensee determined that the degradation resulted from MIC. The service water RT shows a non-crack-like rounded shaped indication characteristic of MIC. The leakage was evaluated and the evaluation determined that the leakage has not caused any flooding or spraying onto any adjacent electrical equipment.
SNC stated that it is not possible to repair the location for FNP, Unit 1 while the plant is in operation because no isolation valve exists between the leak and the B-train Service Water supply header. For FNP, Unit 2, repair in this location is not possible since this line supplies the makeup water to the Circulating Water canal and no other sources of water are available to supply the amount of water needed while the unit is in operation.
5.2 Augmented Inspection The licensee chose five other susceptible locations for augmented volumetric examinations per GL 90-05 for each leak. No flaws were detected by these examinations, and SNC has determined that initial leaks in both units are a localized condition.
5.3 Temporary Noncode Repair and Monitoring Provisions The licensee will leave both pipes as is with a banded rubber patch that will direct leakage to a container or floor drain. Operations will perform a weekly qualitative assessment of both of the FNP, Unit 1 and 2 leaks with the housekeeping patch installed to identify any degradation of structural integrity. If the leak rate increases significantly, an engineering evaluation will be performed to determine the need for additional action, including a reassessment of structural integrity. Also, followup volumetric examination will be performed on or before each 3-month anniversary of the completion of the original examination until the repair or replacement is completed. The flaw will be repaired or replaced during the next scheduled outage or during a scheduled outage exceeding 30 days, whichever comes first. The outage for FNP, Unit 1 is schedule to begin in October 2004 and the outage for FNP, Unit 2 was scheduled to begin in March 2004.
6.0 CONCLUSION
The NRC staff has determined that the licensees flaw evaluation was consistent with the guidelines and acceptance criteria of GL 90-05. The NRC staff, therefore, finds the licensees structural integrity and operability assessments to be acceptable. The licensee had established a periodic inspection program to monitor leak rate and ensure continued operability. The licensee had also chosen five other susceptible locations for augmented volumetric examinations per GL 90-05. The licensees actions constituted an acceptable temporary alternative to the Code requirements. Furthermore, the staff finds that performance of an immediate Code repair would have constituted an undue burden (create undue hardship) upon the licensee since the repair may not have been completed within the time period permitted by the LCO, and, thus, an isolation of the affected service water piping would have been required.
Such an isolation is not in the best interest of plant safety, given the magnitude of the flaw and the licensees alternative program.
Because compliance with the specified requirements would result in hardship without a compensating increase in the level of quality and safety, the NRC staff concludes that the licensees proposed alternative to the Code requirements is acceptable and, therefore, is authorized pursuant to 10 CFR 50.55a(a)(3)(ii) until each units next cold shutdown greater than 30 days or at the latest, Refueling Outage 1R19 scheduled for October 2004.
Principal Contributor: D. Votolato Date: June 25, 2004
Joseph M. Farley Nuclear Plant cc:
Mr. Don E. Grissette General Manager -
Southern Nuclear Operating Company Post Office Box 470 Ashford, Alabama 36312 Mr. B. D. McKinney, Licensing Manager Southern Nuclear Operating Company Post Office Box 1295 Birmingham, Alabama 35201-1295 Mr. M. Stanford Blanton Balch and Bingham Law Firm Post Office Box 306 1710 Sixth Avenue North Birmingham, Alabama 35201 Mr. J. B. Beasley, Jr.
Executive Vice President Southern Nuclear Operating Company Post Office Box 1295 Birmingham, Alabama 35201 State Health Officer Alabama Department of Public Health 434 Monroe Street Montgomery, Alabama 36130-1701 Chairman Houston County Commission Post Office Box 6406 Dothan, Alabama 36302 Resident Inspector U.S. Nuclear Regulatory Commission 7388 N. State Highway 95 Columbia, Alabama 36319 William D. Oldfield SAER Supervisor Southern Nuclear Operating Company P. O. Box 470 Ashford, Alabama 36312