ML20248D749

Safety Evaluation Accepting Licensee Request for Relief from ASME Code Repair Requirements for ASME Code Class 3 Piping

ML20248D749
Person / Time
Site:	Arkansas Nuclear
Issue date:	05/28/1998
From:	NRC (Affiliation Not Assigned)
To:
Shared Package
ML20248D738	List: ML20248D734 ML20248D749
References
NUDOCS 9806030087
Download: ML20248D749 (9)

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UNITED STATES

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g-j' NUCLEAR REGULATORY COMMISSION l

t WASHINGTON, D.C. SD000 601 4,.....,c SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION L

BgQWhETfQREELIEr FROM ASME CODE REPAIR REQUIREMENTS i

FOR ASME CODE CLASS 3 PIPING l

ENTERGY OPERATIONS. INC.

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ARKANSAS NUCLEAR ONE. UNIT _1 i

DOCKET NO 50-313

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 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-r service. ' A Code repair is required to restore the structural integrity of flawed Code piping, l.

l' independent of the operational mode of the plant when the flaw is detected. Those repairs not in I

compliance with Sect;on XI of the Code are non-Code repairs. However, the implementation of

. required Cooe (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.

Technical Specification (TS) 4.0.5 says, in part, that inservice inspection and testing of ASME Code Class 1,2 and 3 components shall be applicable as follows:

inservice inspection of ASME Code Class 1,2 and 3 components and inservice testing of ASME Code Class 1,2 and 3 pumps and valves shall be performed in accordance with Section XI of the ASME Boiler and Pressure Vessel Code and applicable Addenda as required by 10 CFR 50, Section 50.55a(g), except where specific written relief has been l

granted by the Commission pursuant to 10 CFR 50, Section 50.55a(g)(6)(i).

Altematives to Code requirements may be used by nuclear licensees when authorized by the Director of the Office of Nuclear Reactor Regulation if the proposed attematives to the requirements are such that they are shown to provide an acceptable level of quality and safety in lieu of the Code requirements [10 CFR 50.55a(a)(3)(i)], 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)(ii)].

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 attemative requirements as it determines is authorized by law.

ENCLOSURE 1 I

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. l Generic Letter (GL) 90-05, "Cuidance for Performing Temporary Non-Code Repair 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 piping.

For the purpose of this GL, impracticality is defined to exist if the flaw detect 6d during plant i

operation is in a section of Class 3 piping that cannot be isolated for completing a Code repair 1

within the time period permitted by the limiting condition for operation of the affected system as

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specified in the plant TS, and performance of a Code repair necessitates a plant shutdown.

2.0 - BACKG3OUND On June 5,1996, M the Arkansas Nuclear One, Unit 1 (ANO-1), members of the Entergy

Operations, Inc. (h6reafter referred as the licensee) discovered three locations on the loop 2 supply pipe of the service water system to have less than the required ASME Code minimum wall thickness. Tne locations were discovered during the performance of an automated ultrasonic inspection of 42 locations on the service water piping. The three pits showed a wall thickness of 0.050, 0.026 and 0.050 inches. Based on engineering calculations, the minimum allowable wall thickness for the pipe was.056 inches. The average corrosion rate for the service water piping was approximately 0 003 inches per year. Using this corrosion rate, three additional pipe

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locations wore projected to be at or be ow minimum allowable wall thickness before current y scheduled replacement dates. A visual inspection was performed at these six locations. Based on visual inspection, it was confirmed that the service water piping was not leaking and the extemal appearance of the areas of concem was not degraded. The ANO-1 service water system was constructed in accordance with ANSI B31.1, but was reclassified as ASME Class 3 for the purpose of inservice inspection specified h ASME Section XI. The affected supply piping was 14-and 16 imh carbon steel piping having nominal wall thickness of 0.375 inches, in the event that an entire loop of service water is declared inoperable, technical specification 3.3.6 (TS) requires that the reactor shutdown be initiated and the reactor be placed in hot shutdown within 36 hours4.166667e-4 days <br />0.01 hours <br />5.952381e-5 weeks <br />1.3698e-5 months <br />. By "1CAN079601, Requests Relief from Requirements of ASME B&PV Code,Sections III & XI Due to Flaws in SW Piping,Iaw 10CFR50.55a & Guidance Provided in [[generic letter" contains a listed "[" character as part of the property label and has therefore been classified as invalid. & GL 91-18|letter dated July 3,1996]], the licensee requested relief from the ASME Code,Section XI replacement requirements. The request for relief was based on the results of a flaw l

evaluation that was performed by the licenses la accordance with the guidelines and acceptance criteria contained in GL 90-05.

3.0 LICENSEE'S RELIEF REQUEST I

3.1 Components for Which Relief !s Requilifd Six locations on ASME Code Cir ss 3 service water piping were calcWated to have less than the required ASME Code minimum wall thicknass. Locations were as follows: (1) 4 % feet downstream of the HBD 4-8" branch to the emergency feedwater supply line; (2) between the HCD-117-3" branch for the emergency control room chiller VCH-4A and vent valva SW-634; (3) between system vent valve SW-634 artd the HSD 45-10" branch for the reactor building coo!ers VCC-2C/D; (4) loop 2 supply header HBD-20-14" between vent valve SW-634 and the HBD-45-10" branch for the reactor building coolers (VCC-2C/D) in the reactor auxiliary building; (5) loop 2 supply header HBD 20-18" approximately six feet dowrstream of FE-3901 in the turbine building pipe chase; and (6) icop 1 supply header HBD 14-18" approximately 6 % feet downstream of FE-3902 in the tuibine building pipe chase.

. 3.2 - Section XI Edition for ANO-1 The 1980 edition of the ASME Code,Section XI through and including 1981 addenda applies to this issue.

3.3 ASME Section XI Code Requirement The ASME Code Section XI requires that repairs or replacements of ASME Code Class l

components be performed in accordance with rules found in Articles lWA-4000 or lWA-7000, l-respectively. The intent of these rules serve to provide an acceptable means of restoring the l

structural integrity of a degraded Code Class system back to the original design requirements.

i 3.4 Content of the Relief Reauesj Relief was sought from performing a repair or replacement of the service water piping per the requirements of Article IWA-4000 or IWA-7000, respectively. Relief was sought until the next maintenance outage for ANO-1,1R13, which was scheduled for September 1996. Permanent Code repair rer replacement was scheduled for and was subsequently performed during this outage.

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I 3.5 Basis for Relief Request for relief has been submitted and altomatives to the Code requirements have been i

propor,ed by the ticensee. The licensee has evaluated the flaw in accordance with the guidance provided in GL 90-05. Based upon the evaluation, it was estab'ished that the flaw satisfies the criteria for non-Code repair as described in GL 90-05 and perfomiing permanent repairs in accordance with the ASME Code would be impractical during plant operation. To perform a Code-qualified repair during power operation would not have been possible since a condition that would cause one loop of service water to be inoperable requires that the reactor be placed in hot shutdown within 36 hours4.166667e-4 days <br />0.01 hours <br />5.952381e-5 weeks <br />1.3698e-5 months <br /> per TS 3.3.6. Based on the results of the visualinspection which confirmed that the service water piping is nct leaking and the extemal appearance of the areas of concem revealed no signs of degradation, it would have been unadvisable to alter the plant conditions of the plant and possibly create a higher risk configuration in order to pelform the repairs.

3.6 Lh;i2nsee's Altemative Prooram Because the pipe flaws are not through-wall flaws and are not expected to leak, no immediate temporary repairs were performed. However, if a leak had occurred before the planned permanent Code repair, the licensee planned to install a simple rubber patch attached to the pipe by band clamps to serve as a "stop gap" measure to limit the leakage for housekeeping purposes. The patch would have been maintained as a ten,porary repair and would not have altered the structuralintegrity of the piping and was reversible, if necessary. The licensee planned to maintain this patch, or a sirnilar configuration, as a temporary repair until Code repair could be made. In accotdance with GL S0-05 guidance, the integrity of the non-Code repair will be assessed on a quarterty basis utilizing an ultrasonic examination method. Furthermore, a qualitative visual assessrr ent for leakage of the affected piping would be performed or' a weekly basis to determine any degradation of structuralintegrity. These inspections were to continue until the permanent Code repair was completed.

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. 4.0 STAFF EVALUATION AND CONCLUSIONS 4.1 Operability Determination. Root Cause Analysis and Simotural Inteority Evaluation The licensee determined that six locations on the service water system were below the minimum ASME Ccde required minimum wall thickness. This system was constructed in accordance with ANSI B31.1, Power Piping Code, but is treated as ASME Class 3 for the purpose of meeting the inservice inspection requirements of ASME Code,Section XI. Upon discovery of those locations, the licensee performed an operability determination of the service water system in the "as found" condition and the system was determined to be operable. Based upon the results of ultrasonic and visual examination that was performed on these locations, the licensee determined that the service water piping was not leaking and the extemal appearance of the area of concem did not show signs of degradation. The licensee also determined that the system was operable and because the piping was not leaking, there would be no adverse affect on any other safety-related equipment in the surrounding area.

Based on the UT data, the locations were determined to be localized and located on pits which were typical of corrosion degradation in service water piping. Previous evaluations of the large bore service water piping, performed as part of ANO's Service Water integrity Program, has determined that similar pitted areas are most likely to be caused by microbiologically induced corrosion. The licensee also evaluated the structuralintegrity of the piping using GL 90-05.

Based upon the evaluation, it was determined that the integrity of the piping would be maintained and that the flawed piping satisfied the criteria of GL 90-05.

4.2 Auomented Inspection The licensee identified three areas on the service water piping that were below the minimum ASME Code required wall thickness. These locations were identified during the automated inspections of 42 locations of the service water system. Using projected corrosion rate of 0.003 inches, the licensee identified three additional locations that were projected to be below the l

minimum required wall thickness. A visual examination was performed on those six locations.

The visual examination confirmed that the piping was not leaking and did not show signs of extemal degradation.

4.3 Proposed Temporarv Non-Code Repair and Monitorino Provisions Bec.ause the pipe flaws are not through-wall flaws and are not expected to leak, no immediate temporary repairs were performed. However, if a leak occurred before the planned permanent l

Code repair, the licensee planned to install a simple rubber patch attached to the pipe by band

. clamps to serve as a "stop gap" measure to limit the leakage for housekeeping purposes. The patch would have been maintained as a temporary repair end would not have altered the structuralintegrity of the piping and was reversible, if necessary. The licensee planned to maintain this patch, or a similar configuration, as a temporary ispair until Code repair could be made. In accordance with GL 90-05 guidance, the licensee stated that the integrity of the non-l Cods repair would be assessed on a quartarty basis utilizing an uMrasonic examination method.

Furthermore, a qualitative visual assessment for leakage of the affected piping was performed on a weekly basis to identify degradation of structural integrity. These inspections wero 'o be performed until the permanent Code repair was completed.

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( 4.4 Staff Conclusions The staff has determined that the licensee's flew evaluation is consistent with the guidelines and acceptance criteria of GL 90-05. The staff therefore finds the licensees' structural integrity and operability assessments to be acceptable. The licensee monitored the six locations identified as being under the ASME required miaimum wall thickness by ultrasonic examination that was performed quarterly and visual assessment for leakage of the affected piping was performed on a weekly basis to determine any degradation of structural integrity. The staff finds that the licensee's actions constitute an acceptable temporary attemative to the Code requirements.

Furthermore, the staff finds that performance of an immediate Code repair was impractical since it would have required an isolation of the affected senrice water piping. Such an isolation is not in the best interest of plant safety, given the magnitude of the flaws and the staff's finding that l

the licensee's attemative program provided adequate assurance of structuralintegrity. Pursuant to 10 CFR 50.55a(g)(6)(i), the staff grants the requested relief on the basis that it was impractical to make immediate repairs in conformance with the Code and that the licensee implemented the attematives during the period between disccvery of the SWS piping degradation at ANO-1 and the subsequent repairs to the affected piping in conformance wM5 the Code. The relief granted 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 l

and facility that could result if the Code requirements were imposed on the facility.

Principal Contributors: G. Georgiev W. Reckley Date: May 28, 1998 l

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WASHINGTON, D.c. 20066 0001

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I SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION REQUEST FOR RELIEF FROM ASME CODE REPAIR REQUIREMENTS f_OR ASME CODE CLASS 3 PIPING ENTERGY OPERATIONS. INC..

ARKANSAS NUCLEAR ONE. UNIT 2 DOCKET NO. 50-368

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 Mechanie.al Engineers (ASME) Boiler and Pressure Vessel Code (hereafter referred as the Code). E,vetion 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 an isolation of the system requiring the repair, and often a shutdown of the nuclear power plant.

Technical Specification (TS) 4.0.5 says, in part, that inservice inspection and testing of ASME Code Class 1,2 and 3 components shall be applicable as follows:

Following start of facility commercial operation, inservice inspection of ASME Code Class 1,2 and 3 components and inservice testing of ASME Code Class 1,2 and 3 pumps and valves shall be performed in accordance with Section XI of the ASME Boiler and Pressure Vessel Code and applicable Addenda as required by 10 CFR 50, Section 50.55a(g), except where specific written relief has becn granted by the Commission pursuarit to 10 CFR 50, Section 50.55a(g)(6)(i).

Altematives to Code requirements may be used by nuclear licensees when authorized by the Director of the Office of Nuclear Reactor Regulation if the proposed attematives to the requirements are such that they are shown to provide an acceptable level of quality and safety in lieu of the Code requirements [10 CFR 50.55a(a)(3)(i)], orif 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)(ii)].

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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 I

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[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 altemative requirements as i

it determines is authorized bylaw.

ENCLOSURE 2

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' 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 staff in evaluating relief requests submitted by licensees for temporary non-Ccde repairs of Code l

l Class 3 piping. The relief granted is authorized by law and will not endanger life or property or the common defense and secunty, and is otherwise in the public interest, giving due consideration to the burden upon the licensee and facility that could result if the Code

- requirements were imposed on the facility.-

2.0 BACKGROUND

n October 4,1996, at tho Arkansas Nuclear One, Unit 2 (ANO-2), members of the Entergy -

Operations, Inc (hereafter referred as the licensee) discovered a three drops per minute bak

' from the water supply line to the "B" emergency feedwater pump. Based on visual inspection, it 1

i was detemlined that the source of the leak was a through-wall defect in the service water system -

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L (SWS) piping. The operability of the service water system in the "as found" condition was assessed and determined to be operable. In addition, the licensee evaluated other system interactions such as flooding, water spraying on plant equipment as a result of the leak, and loss l

of flow to service water-supplied components. In all cases, the leak was determined to be insignificant and will not cause degradatbn of individual system comporeents. The specific L

location of the pinhole leak is approximately 5 feet downstream of Loop 1 header connection of service water to emergency feedwater (EFW) supply line 2HBC-854". This portion of the line is upstream of the first isolation valve (2SW-39A) and is not isolable from the Lonp 1 service water.

j piping. The SWS was constructed in accordance with the requirements of the ASME Code Section ill, Class 3. Unit 2 Technical Specification 3.7.1.2 requires that two emergency.

i feedwater pumps shall be operable. - With one EFW pump and its flow path inoperable, the

-l inoperable train is raquired to be restored within 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> or the unit must be placed in Hot -

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Shutdown within 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br />. By lette-dated November 4,1990, the licensee requested relief from the ASME Code,Section XI replacement requirements. The request for reliof was based on the results of a through-wall flaw evaluation that was performed by the licensee in accords.nce with' i

the guidelines knd acceptance criteria contained in GL 90-05.

3.0 LICENSEE'S RELIEF REQUEST 3.1 Components for Which Relief is Reauested One location on ASME Code Class 3 service water piping that hss been determined to have a j

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through-wall defect. The location was identified to be 5 feet downstream of the Loop i header

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connection of the SWS to EFW supply line 2H.BO 85-6".

j 3.2 Section XI Edition for ANO-2 l

The 1988 edition of the ASME Code,Section XI.

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3.3 ASME Section XI Code Requirement The ASME Code Section XI requires that repairs or replacements of ASME Code Class j

components be performed in accordance with rules found in Articles IWA-4000 or IWA-7000, 1

I respectively. The intent of these rules serve to provide an acceptable means of restoring the structural integrity of a degraded Code Class system back to the original design requirements.

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3.4 Content of the Relief Reauest Relief was sought from performing a repair or replacement of the service water piping per the requirements of Article IWA-4000 or IWA-7000, respectively. Relief was being sought until the next refueling and maintenance outage for ANO-2,2R12, which was scheduled to begin in May 1997. Permanent Code repair or replacement was scheduled for and was subsequently performed during this outage.

3.5 Basis for Relief Request for relief has been submitted and attematives to the Code requirements have been proposed by the licensee. The licensee has evaluated the flaw in accordance with the guidance provided in Generic Letter 90-05. Based upon the eva!uation, it was established that the flaw satisfies the criteria for non-Code repair as described in Generic Letter 90-05 and performing permanent repairs in accordance with the ASME Code would be impractical since the repair would have likely taken longer than tne allowed TS outage time (72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />) and would have therefore necessitated an unwarranted shutdown of ANCF2.

3.6 Licensee's Altemative Prqgegjn A c! amp device was installed over the defect area as a "stop gap" measure to limit leakage for housekeeping purposes. The iristalled clamp did not alter the structuralintegrity of the piping.

The licensee maintcined the clamp until a permanent replacement was performed daring the next refueling outage. The licensee stated that, in accordance with Generic Letter 90 05 guidance, the integnty of the non-Code repair would be assessed on a quarterly basis utilizing an ultrasonic testing examination method and a qualitative vlaual assessment of leakage through the temporary non-Code repair and affected piping would be perfotmed on a weekly basis to determine any degradation of structuralintegrity. The quaderly ultrasonic and weekly visual inspections were to be performed until the Code repair was completed 4.0 STAFF iEVAl.UATION AND CONCLUSIONS 4.1 Operability Determination. Root Cause Analysis end Structurs[,Inteority Evaluation The licensee determined that one location on the service water system has a "through-wall flaw" and was leaking at the rate of 3 drops per minute. This system was constructed in accordance with ASME Code, Class 3. Upon discovery cf the leak, the licensee performed an operability determination of the s hvice water system in the "as found" condition and the system was determined to be operable and because leak was small, there were no adverse f.ffect on any other safety related equipment in the surrounding area.

Based on the ultrasonic testing (UT) exarnination data, the flaw wns determined to be localized through-wall pit which is typicci of corrosbn degradation in service water piping. The licensee evalJattd the strUCturalintegrity of the piping using the cuidance of Generic Letter 90-05. Based upon the evaluation, it was deiermined that the integr~ty of the pioing would be maintained and r

thaMhe fiawed piping satisfied the criteria of Generic Letter 90-05.

l 4.2 Auomented Insoection Five additional locations, representative of the environment seen by the defect, were selected for augmented inspection utilizing UT. These included two locations downstream of the similar Loop 2 service water connection and three discretional pipe location downstream of the leak. The inspection results indicated negligible overall corrosion but did detect one pit that had a remaining wall thickness of 0.039 inches. This wall thickness does not violate the minimum ASME Code required thickness. The inspection results determined that the actual leak was the only location that violated the minimum required pipe wall thickness.

4.3 Proposed Tomoorary Non-Code Repair and Monitorina Provisions A clamp device was installed over the defect area as a "stop gap" measure to limit leakage for housekeeping purposes. The installed clamp did not alter the structural integrity of the piping.

t The licensee maintained the clamp until a permanent replacement was performed during the I

next refueling outage. The licensee stated that, in accordance with Generic Letter 90-05 guidance, the integrity of the non-Code repair would be assessed on a quarter 1y basis utilizing an L

ultrasonic testing examination method and a qualitative visual assessment of leakage through l

the temporary non-Code repair and affected piping would be performed on a weekly basis to l

determine any degradation of structural integrity. The assessment and visual inspection were to i

be performed until the Code repair was completed.

L 4.4 Staff Conclusions I

The staff has determined that the licensee's flaw evaluation is consistent with the guidelines and l

acceptance criteria of GL 90-05. The staff therefore finds the licensees'structuralintegrity and operability assessments to be acceptable. The licensee performed a temporary non-Code repair of the leaking area using a clamp device that was installed over the defect area until a Code l

repair was completed during the next refueling outage (which began on May 9,1997). Pending l

the completion of the Code repair, the licensee committed to assessing the integrity of the non-l L

Code repair on a quarterly basis utilizing an ultrasonic testing examination method and on a i

weekly basis utilizing a visual assessment ofleakage. The staff finds that the proposed attemative provides assurance of structural integrity and that an immediate Code repair of the i

i affected piping was impractical while ANO-2 was operating at power.

Pursuant to 10 CFR 50.55a(g)(6)(i), the den grints the requested relief on the basis that it was j

impractical to make immedick r6 pairs in conformance with the Code and that the licensee implerpented the attematives during the period between discovery of the SWS piping degradation at ANO-2 and the subsequent repairs to the affected piping in conformance with the Code. The relief granted 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 and facility that could result if the Code requirements were imposed on the facility.

PrincipalContributors: G. Georgiev W. Reckley Date: May 28, 1998 L