ML20199L050

SER Accepting Inservice Insp Program Relief Request NDE-32

ML20199L050
Person / Time
Site:	North Anna
Issue date:	11/24/1997
From:	NRC (Affiliation Not Assigned)
To:
Shared Package
ML20199L042	List: ML20199L035 ML20199L050
References
GL-90-05, GL-90-5, NUDOCS 9712010263
Download: ML20199L050 (9)

Text

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pasog p- k UNITED STATES s* NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 30eeH001

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i SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION REOUEST FOR APPROVAL TO REPAIR FLAWS IN ACCORDANCE WITH GENERIC LETTER 90 05 FOR ASME CODE CLASS 3 SERVICE WATER PIPING VIRGINIA ELECTRIC AND POWER COMPANY NORTH ANNA POWER STATION. UNITS 1 AND 2 DOCKET WOS.- 50-338 AND 50-339 t

1.0 INTRODUCTION

10 CFR 50.55a(g) requires nuclear power facility piping and components to meet the applicable requirements of Section XI of the American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code (hereafter referred to as the 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 comoliance with Section XI of the Code are non-Code repairs. However, the implemehtation 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 an isolation of the system requiring the repair, and often a shutdown of the nuclear power plant.

Alternatives to Code requirements may be used by nuclear licensees when authorized by the Director of the Office of Nuclear Reactor Regulation if the proposed alternatives to the requirements are such that they are shown to i provide an acceptable level of quality and safety in lieu of the Code requirements [10 CFR 50.55a(a)(3)(1)] or if compliance with the Code requirements would result in hardship or unusual difficulty without a compensating increase in the level of quality and safety [10 CFR 50.55a(a)(3)(11)).

A licensee may also submit requests for relief from certain Code requirements when a licensee has determined that conformance with certain Code requirements is imaractical for its facility [10 CFR 50.55a(g)(5)(111)). Pursuant to 10 CF1 50.55a(g)(6)(1), the Commission will evaluate determinations of impracticality and may grant relief and may impose alternative requirements as it determines is authorized by law.

ENCLOSURE fokN O

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- Generic Letter (GL) 90 05, " Guidance for Performing Temporary Non Code Repair i of ASME Code Class 1. 2 and 3 Piping," dated June 15, 1990, provides guidance for the staff in evaluating relief requests submitted by licensees for temporary non Code repairs of Code Class 3 31 ping. The staff uses the i guidance in GL 90-05 as its criteria for mecing its safety evaluation of .

relief requests for temporary non Code repairs of Code Class 3 piping. i

2.0 BACKGROUND

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Virginia Electric and Power Company (hereafter referred to as the licensee) i

{ . discovered at the North Anna Power Station. Units 1 and 2. various locations i with evidence of possible previous leakage on several lines of the shared ,

service water system (SWS). A re j

-all affected service water lines. pairInplan all was developed and implemented for cases, the licensee re .

pursuant to 10 CFR 50.55a(g)(6)(1), a relief from the ASME Code. quested.

Section XI replacement-requirements. The licensee based its request for relief-on the results of a "through wall flaw" evaluation that was performed in accordance .

! with the guidelines and acceptance criteria contained in GL 90-05. The NRC  :

staff reviewed those requests and granted relief from the ASME Code requirements for each of the submitted reliefs. On February 24, 1997, the i licensee submitted a request for generic relief for certain stainless steel lines of the SWS because the failure mechanism of the previously identified

. leaks was determined to be microbiologically induced corrosion (MIC). On August 8,199/. the licensee su)plemented its relief request by identifying each and every line for which t7e relief would t* applied. The purpose of the '

generic request is to avoid the submittal of a specific relief request to the NRC for each additional pin leak or location with possible evidence of -

previous leakage that may be identified during routine SWS piping walkdowns. i The MIC monitoring program requires walkdowns of the accessible portiors of the stainless steel SWS piping to identify, monitor and quantify leakage.

When a leak or evidence of pretious leakage is identified, structural analysis - 3 and increased monitoring of the affected welds is implemented. Further, the  !

program includes 3rovisions for evaluating continued system operability in i accordance with G. 90-05 until appropriate Code repairs can be completed. i I 3,0 LICENSEE'S RELIEF REQUEST 3.1 Comoonents for Which Relief is Reauested i

The following drawings containing the SWS line numbers for which a generic ,

relief was sought were identified by the licensee.

DRAWING 11715-CBB 040D-2. SHEET 1 1/4"-WS G37-153A 03 3/4"-WS-F83 163 3/4"-WS F82-163 03 4"rWS G01 163 03 4"-WS-F99 163 03 .

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DRAWING 11715-CBB-0400 2. SHEET 2 1-1/4"-WS H78 153A 03 1-1/4"-WS-H81-153A-03 DRAWING 11715 CBM-078A 2. SHEET 1 3/4"-WS-G31-163-03 3/4" WS H77-163-03 4" WS-H76-163 03 3/4" RS G30-163 03 3/4" WS-339 163-03 3/4"-WS G36-163-03 3/4"-WS 930-163-03 1/2"-WS-F61-163 03 2"-WS-D72 163 03 3/4"-WS F78 163 03 4" WS F63 163 03 3/4"-WS-F67-163-03 4" WS F64-163 03 3/4"-WS-F80-163-03 3/4"-WS F68 163-03 4"-WS-F65 163 03 3/4" WS-F69-163-03 8" WS-93-163 03 8"-WS94-163 03 4"-WS-F62 163 03 3/4" WS-F66 163-03 '

3/4"-WS F79-163 03 DRAWING 11715-CBM-078A-2. SHEET 4 8" WS 515-163-03 8"-WS-513 163 03 4" WS H48-163-03 3/4"-WS H52-163 03 4"-WS H50-163-03 3/4"-WS-H54 163 03 3/4" WS H67-163 03 3/4" WS G32-163-03 8"-WS-115 163 03 8"-WS-113 163-03 4"-WS-47-163-03 3/4"-WS H60-163 03 3/4"-WS-H62-163 03 4" WS 56-163-03 8"-WS-114-163-03 8" WS-516-163 03 8" WS-514-163 03 3/4"-WS-F64-163 03 3/4" WS-H53-163 03 3/4" WS-H66 163-03 4"-WS-H51-163-03 3/4" WS H55-163 03 3/4"-WS-G33-163-03 8" WS-116 163 03 4"-WS-46-163-03 2"-WS-926-163 03 3/4"-WS-H61-163 03 3/4"-WS H63-163 03 4"-WS-57 163 03 DRAWING 11715 CBM 0788-2. SHEET 1 ,

1-1/2"-WS 346-163-03 1" WS-G06-163 03 1-1/2"-WS-348-163 03 1" WS G05 163 03 1 1/2"-WS-350 163-03 1"-WS-G04-163 03 1-1/2" WS 352-163-03 1"-WS-G03 163 03 3/4"-WS-347-163-03 3/4" WS-351-163 03 1"-WS 347-163 03 1 1/2"-WS-347-163-03 1"-WS-349-163 03 1-1/2"-WS-349-163 03 1" WS 351-163-03 1-1/2"-WS-351-163-03 1"-WS-353-163 03 1-1/2"-WS-353-163-03 3/4"-WS 349-163-03 3/4" WS 353-163-03 DRAWING 11715-CBM 078B-2. SHEET 3 1-1/2"-WS-724-163 03 1" WS 933-163 03 1-1/2"-WS-726-163-03 1"-WS 934-163-03 1"-WS-729-163-03 1 1/2"-WS-729 163-03 1"-WS-731-163 03 1-1/2"-WS-731-163-03 3/4"-WS-725-163-03 3/4"-WS-729-163 03 1"-WS-725-163-03 1-1/2"-WS-725-163-03 1"-WS 727-163 03 1-1/2"-WS 728 163-03 1"-WS-935-163-03 1-1/2" WS-730-163 03 1"-WS-936-163 03 1-1/2"-WS-727-163-03 3/4" W:-725-163 03 3/4"-WS-731-163-03

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i 4-DRAWING 11715 CBM-078C-2. SHEET 2 4" WS-46 163-03 3/4"-WS-A47-163-03 1"-WS-81 163 03 1" WS 77-163-03 1" WS-477-163-03 1"-WS-481-163 03 3"-WS 73 163 03 4" WS-47-163 03 3/4"-WS-A49 163 03 1"-WS82-163 03 1"-WS-78-163-03 1"-WS 478 163 03 1"-WS-482 163-03 3" WS-74-163-03 4"-WS 56 163 03 3/4" WS-A48-163 03 1" WS 85 163-03 1"-WS-485 163 03 1"-WS 487 163 03 1"-WS 489 163-03 1" WS-491 163 03 3" WS-75 163 03 3"-WS 76-163-03 3/4" WS-79 163 03 3/4"-WS-381-163-03 2"-WS 80-163-03 3/4"-WS-83 163 03 3/8"-WS-383-163 03 3/8" WS 382-163 03 2" WS-376-163 03 3/8" WS-397-163-03 3/8" WS-398-163-03 1"-WS-90-163 03 3/4" WS-C06 163-03 1" WS-92 163 03 1" WS-86-163 03 3/4"-WS-C01-163 03 1" WS 488-163 03 3/4"-WS 913-163 03 1" WS 490 163-03 1"-WS-78-163-03 1"-WS-478-163-03 1"-WS-492-163 03 4"-WS-57 163-03 3/4"-WS-773-163 03 2"-WS-772 163-03 3/8" WS-910-163 03 3/8"-WS-914 163 03 2"-WS-776-163 03 3/8" WS-916 163 03 2"-WS-777-163 03 1"-WS-486 163-03 2" WS-377-163 03 3/8" WS-C01-163 03 3/8" WS-399-163 03 3/4"-WS-378 163-03 2"-WS-84-163-03 3/4"-WS-379-163 03 1"-WS-88-163 03 3/4"-WS-380-163-03 3/4"-WS-83-163 03 3/8" WS-383 163 03 3/4"-WS A50-163 03 1"-WS89-163 03 3/4" WS-400-163-03 3/4" WS-774-163 03 2"-WS-775-163 03 3/8"-WS-913-163 03 3/8"-WS 915-163 03 3/4"-WS-779 163 03 3/4"-WS-909-163 03 3/8" WS-912-163 03 DRAWING 11715-CBM-078G-2. SHEET 1 2"-WS-D46 153A-03 1"-WS-D50-153A-03 3/4"-WS-039-153A 03 1"-WS-D30-153A-03 3/4"-WS-D41-153A-03 3/8"-WS D55-163-03 1"-WS-031-153A 03 3/4" WS-043-153A-03 3" WS-73-163 03 2"-WS54-163 03 2"-WS-52-163-03 3/4"-WS D67-163-03 2" WS 50-163-03 3"-WS-74-163 03 2"-WS-55-163 03 3/4"-WS-054-163 03 2"-WS-53-163 03 3/4"-WS-D68-163-03 2" WS-51-163-03 2"-WS C88-153A-03 2"-WS C81-153A 03 2"-WS C87-153A 03 2"-WS-63-163-03 3/4" WS 061-163-03 2" WS-62-163 03 2"-WS-C80-153A-03 3/4"-WS-C67-153A-03 3/4"-WS-C73 153A-03 3/4"-WS-C76-153A-03 3/4" WS C70-153A 03 2"-WS-C86 153A-03 2"-WS 79-153A-03 2" WS-C85-153A 03 3/4"-WS-062 161-03 2"-WS-60-163-03 3"-WS-75-163 03 3/4"-WS D69-163 03 2" WS-61-163 03 3/4" WS D56-163-03 2" WS C83 153A-03 2" WS-C89-153A-03 3/4"-WS-060-163-03 2"-WS 64-163-03 2" WS-65-163-03 2"-WS-C82-153A-03 3/4"-WS C68-153A-03 3/4"-WS-C74-153A 03 3/4"-WS-C71-153A-03 3/4"-WS-070-163-03 3"-WS-76 163-03 2"-WS C78-153A 03 3/4"-WS-C66-153A-03 3/4" WS-C72-153A-03 3/4"-WS-C75-153A-03 3/4"-WS C69-153A 03 2"-WS-C84-153A-03 3/4"-WS-C77-153A-03

-mm ..

DRAWING 11715 CBM 078G-2. SHEET 2 2" WS 046-163A-03 3/4"-WS 071 153A 03 1"-WS D47-153A 03 3/4" WS 033-153A 03 3/4"-WS 051-163 03 1" WS-D48-153A 03 3/4"-WS 035-153A 03 3/4"-WS-052-163 03 1"-WS D49 153A-03 3/4" WS D37-153A 03 3/4"-WS-053 163 03 3"-WS-73 163 03 3/4" WS 063 163 03 3"-WS-74-163 03 2" WS 454-163 03 2"-WS 455-163 03- 2" WS 452-163 03 2" WS 453-163 03 2" WS 450163 03 2"-WS-451-163 03 2"-WS-949-153A-03 1-1/2" WS 981 153A 03 1 1/2"-WS-965-153A 03 2"-WS 955 153A-03 3/4"-WS D57-163 03 2" WS-464-163 03 2" WS-465-163 03 3" WS-75-163 03 3" WS-76 163-03 3/4"-WS-059 163-03 2" WS 461-163 03 3/4"-WS-065-163-03 3/4"-WS 066-163 03 3/4"-WS 934 153A 03 2"-WS 948 153A 03 3/4"-WS-940-153A 03 1-1/2"-WS 976-153A 03 1-1/2"-WS-982-153A 03 3/4"-WS-943-153A-03 3/4"-WS 937-153A-03 2"-WS-954-153A 03 2"-WS-947-153A 03 1-1/2"-WS 977-153A-03 1-1/2"-WS 963 153A 03 2"-WS-953-153A-03 3/4"-WS 058-163 03 2"-WS-462-163 03 2"-WS 463-163-03 2"-WS 946-153A-03 1-1/2"-WS-979 153A 03 1-1/2"-WS-978-153A-03 2"-WS-952 153A 03 2"-WS-945-153A 03 1-1/2"-WS-980-153A-03 1-1/2"-WS-961-153A 03 2"-WS 460 163-03 2"-WS 945-153A 03 2" WS 944-153A-03 1-1/2"-WS-975-153A 03 1-1/2"-WS-971-153A 03 2" WS 950-153A 03 DRAWING 11715-CBM-078H 2. SHEET 1 1" WS-9-163 3/4"-WS-E03-163 3/4"-WS-F44-163 1"-WS G07-163 3/4"-WS-E08-163 1"-WS-947-163 1" WS-G50-163 1"-WS-10 163 3/4" WS-F45-163 2"-WS E64 163 1/2"-WS-E68 163 1"-WS D97-163 2' WS 091 163 1"-WS H48-163 The above listed piping lines are classified as ASME Code Class 3. moderate energy stainless steel piping of the SWS. The piping provides cooling water from the service water reservoir to safety-related equipment and returns service water back to return headers. Normal operating pressure is 100 psig.

The design pressure is 150 psig and the design temperature is 150 F.

3.2 Section XI Edition for North Anna 1 and 2 North Anna Unit 1 - 1983 Edition of the ASME Code.Section XI including Summer 1983 Addenda.

North Anna Unit 2 - 1986 Edition of the ASME Code.Section XI.

3.3 ASME Section XI Code Recuirement The ASME Code Section XI requires that repairs or replacements of ASME Code Class components be performed in accordance with rules found in Articles IWA-4000 or IWA 7000. respectively. The intent of these rules serves to provide I

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• an acceptable means of restoring the structural. integrity of a degraded Code  :

Class system back to the original design requirements.

3.4 Content of the Relief Reauest-Relief is sought from performing a repair or replacement of the service water [

piping )er the requirements of Article IWA 4000 or IWA 7000, res)ectively, and .

from su)mitting to the NRC a relief request for each and every caservation of evidence of pin hole leaks in the stainless steel piping portion of the SWS listed above. This relief request establishes a plan for continued operation with through wall flaws in stainlest steel piping in the SWS based upon the -

guidance provided in GL 90-05. Relief is being sought because performing a Code repair within the limiting conditions of the SWS operation may be 1mpracticable or impose undue burden upon the licensee without a compensating "

increase in the level of quality and safety.

3.5 Basis-for Relief The licensee has submitted request for relief and proposed alternatives-to the Code requirement. The NRC staff reviewed the proposed alternatives for compliance with the provisions of 10 CFR 50.55a(a)(3)(ii). The licensee has committed to evaluate any newly found flaw or indication of a flaw in accordance with the guidance provided in Generic Letter 90 05. Based upon the evaluation. it will be established whether the discovered flaws satisfy the criteria for non-code repair as described in Generic Letter 90-05. The evaluation will also determine whether performing permanent repairs in accordance with the ASME Coh within the limits of the limiting conditions of upon the the licensee SWSsince would the constitute re) airs would annecessitateundue burden (create undue the unnecessary iso hardship)lation of portions of the SWS t1at are structurally sound and thus reduce the margins of safety of the SWS. .

3.6 Licensee's Alternative Proaram '

As an alternative to performing Code repairs in accordance with IWA 5250(a)(2) to through wall flaws in the SWS. the flaws will be left as found. The through-wall flaw will be monitored for leakage and must meet the criteria for flooding and spraying consequences and for structural integrity as described in GL 90 05 to remain in service. All welds identified with through wall flaws will be re) laced within 18 months from the time of discovery. This alternative to tie Code requirement will be followed for the remainder of the second 10-year inspection interval.- The Unit I second 10-year interval will end on December 24. 1998, and the Unit 2 second 10-year interval will end on December 14, 2000. The structural integrity of the SWS will be monitored by the following methods until the repairs required by IWA-5250(a)(2) are completed.

1. Weekly visual monitoring of all through wall flaws. If the welds are determined to be structurally acceptable.-then the visual. monitoring i frequency will;be decreased to once every 6 weeks.

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2. All welds identified as having a through wall flaw will be assessed for structural integrity within 14 days of detection. 69tt welds, if accessible, will be radiographed to characterize the flaws. Butt welds that areiin".cessible to radiography and socket welds will be assessed for structural integrity by assuming a conservative large hole. Welds determined to be structurally adequate will be included in the above monitoring program. Identification of a structurally inadequate weld will result in associated piping to be declared inoperable and an appropriate Technical Specification action statement to be taken.

3. Weekly visual monitoring of through-wall flaws in socket welds and outt welds that are inaccessible to radiography for a period of 2 months. If there is no significant change in the leakage rate, the monitoring frequency will be decreased to once every 6 weeks until the welds are repaired. A significant change is defined as a 0.5 gpm increase in the leakage rate from the initial observed leakage condition for each weld.

Should any location reach the threshold of significant change the weld will be reassessed for structural integrity and flood / spraying consequences.

4. A walkdown of the accessible stainless steel portions of the SWS will be performed every 6 weeks. The frequency of these walkdowns will be assessed after a year and may be adjusted based on results of inspections.

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5. A total leakage rate limit of 1.0 gpm for single supply or return line for an individual component will be established, if this total leakage rate limit is exceeded, then an evaluation will be performed to determine if a design service water flow is available to affected components. Inadequate service water supply will cause the associated service water lines and equipment to be declared inoperable and appropriate actions will be taken according to Technical Specifications.

6. An augmented radiographic inspection program will be performed on a quarterly basis on a minimum of 10 welds. The frequency of radiography will be assessed after a year and may be adjusted for each location based upon the results of the radiographic examination.

4.0 STAFF EVALUATION AND CONCLUSIONS 4.1 Doerability Determination. Root Cause Analysis and Structural Intearity Evaluation The licensee has proposed to use the guidance provided in GL 90-05 to assess newly discovered flaws in certain stainless steel lines of the SWS. The system was constructM in accordance with the requirements of ASME Code. Class 3. A routine MIC monitoring program has been developed for the SWS. Theprogram includes walkdowns to identify, monitor and quantify leakage. The SWS has 1

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previously experienced MIC. Radiographic examination of the welds having through wall leakage revealed small voids surrounded by exfoliation, which is typical of MIC. No other type of inservice defects were identified on the radiographs near the areas with through-wall leaks. Additionally, a visual examination of a sample of piping segments removed to repair leaking welds confirmed the presence of HIC.

No through-wall leaks have been identified involving the stainless steel lines associated with this relief. Flaw evaluation for newly discovered welds with

, through-wall leaks will be performed as follows. The flaws in butt welds that can be characterized by radiography will be evaluated by three types of analysis: area reinforcement. limit load analysis, and fracture mechanics using the quidance from GL 90-05. The flaws in welds that cannot be 1 character,'ed by radiography, i.e. socket welds and inaccessible butt welds.

? will be evaluated by the same ant. lysis by assuming a 3/41 inch hole fcr each

)oint of leakage within a weld with through-wall leakage. Socket welds will 3e analyzed by treating the weld cross section as an eauir 't pipe cross section.

4.2 Avamented Insoection L To assess the overall degradation of the SWS. an wmented inspection program has been developed. The augmented program is performed on a minimum of 10 welds in the SWS usirg radiography, Radiograp1y will be performed every 3 months. The frequency of radiography will be assessed after a year and may be adjusted for each location based on the results of the radiographs.

4.3 Prooosed Temocrary Non-code Reoair and Monitorino Provisions As an alternative to performing Code repairs in accordance with IWA-E250(a)(?)

for newly discovered through-wall flaws in the SWS, the flaws will be left as found. The through-wall flaw will be monitored for leakage and must meet the

. criteria for flooding and spraying Consequences and for structural integrity a as described in GL 90-05 to remain ir service. All welds identified with through-wall flaws will be replaced within 18 months from the time of discovery. This alternative to the Code requirement will be followed for the remainder of the second 19-year inspection interval. The Unit 1 second 10-fear interval will end on December 24, 1998, and the Unit 2 second 10-year 1rterval will end on December 14. 2000. The structural integrity of the SWS will be monitored by the visual and radiographic examinations as stated in paragraph 3.6 above until the repairs required by IWA 5250(a)(2) are completed.

4.4 Staff Conclusions

. The staff has determined that the licensee's proposed flaw evaluation bn been consistent with the guidelines and acceptance criteria of GL 90-05. The staff, therefore, finds tM licensee's proposed approach acceptable to perform future structn al integrity and operability assessments of the stain 19ss steel

9 piping as listed in paragraph 3.1 above.

The licensee has requested a relief from the burden to submit a relief request to the NRC for each and every through-wall leak discovered in certain stainless steel piping of the SWS. The staff finds this request to be reasonable because: (1) the licensee adheres to the guidance of GL 90 05, as dest-10ed above, up to the poir.t of actually submitting a relief request to the NRC: (2) each occurrence of flaw detection is documented in the North Anna's corrective action system; and. (3) all relevant documentation is available for NRC staff review.

Furthermore, the staff finds that performance of an immediate Code repair after each and every newly discovered flaw caused by MIC would have constituted an undue burden (create undue hardship) upon the licensee since the repair may exceed the time limits imposed by the governing Tecnnical Specification and thus necessitate the isolation of portions of the SWS.

Isolating portions of the SWS to )erform a Code re) air is not in the best interest of plant s9fety, given tie magnitude of tie flaw and the licensee's alternativeprc[

pursuant to 10 FRram. The staff. therefore, 50.55a(a)(3)(11), in thatconcludes comp _ethat relief is warranted with the specified requirements would result in hardship or unusual d11ficulty without a compensating increase in the level of quality a?.d safety. The staff concludes that the licensee's alternative program would p ovide an acceptable level of quality and safety.

Reviewer: G. Georgiev Date: November 14, 1997 ,

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