ML20217J707

Safety Evaluation Accepting Second 10-yr ISI Interval Relief Request I2R-22

ML20217J707
Person / Time
Site:	Wolf Creek
Issue date:	10/09/1997
From:	NRC (Affiliation Not Assigned)
To:
Shared Package
ML20217J682	List: ML20217J677 ML20217J707
References
NUDOCS 9710210228
Download: ML20217J707 (5)

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NUCLEAR REGULATORY COMMISSION WASHINGTON. D.C. 30teHoot

• * * ,o SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION SECOND TEN YEAR INTERVAL INSERVICE INSPECTION PLAN RE0 VEST FOR RELIEF NO. 12R 22 l

WOLE. CREEK NUCLEAR OPERATING CORPORATION WOLF CREEK NUCLEAR GENERATING STATION. UNIT 1 DOCKET NO. 50 482

1.0 INTRODUCTION

The Technical Specifications for Wolf Creek Gen? rating Station. Unit I state that the inservice inspection and testing of the American Society of Mechanical Engineers (ASME) Code Class 1. 2. and 3 components shall be performed in accordance with Section XI of the ASME Boiler and Pressure Vessel Code and applicable Addenda as required by 10 CFR 50.55a. Section 50.55a(a)(3) states that alternatives to the requirements of paragraph (g) may be used, when authorized by the NRC. if (1) the proposed alternatives 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.

Pursuant to 10 CFR 50.55a(g)(4). ASME Code Class 1. 2. and 3 components (including supports) shall meet the requirements, except the design and access provisions and the 3reservice examination requirements, set forth in the ASME Code.Section XI. "lules for Inservice Inspection of Nuclear Power Plant Components." to the extent practical within the limitations of design, and materials of construction of the components. The regulations geometry, require t hat inservice examination of components and system pressure tests conducted during the first ten-year interval and subsequent intervals comply with the requirements in the latest edition and addenda of Section XI of the ASME Code incorporated by reference in 10 CFR 50.55a(b) on the date twelve months prior to the start of the 120 month interval, subject to the limitations and modifications listed therein. The applicable edition of the ASME Code.Section XI for the Wolf Creek Generating Station. Unit 1 during the second ten year inservice inspection (ISI) interval, is the 1989 Edition.

The components (including supports) may meet the requirements set forth in subsequent editions and addenda of the ASME Code incorporated by reference in 10 CFR 50.55a(b) subject to the limitations and modificaticns listed therein and subject to Comission approval.

Pursuant to 10 CFR 50.55a(g)(5). If the licensee determines that conformance with an examination requirement of Section XI of the ASME Code is not practical for its facility information shall be submitted to the Commission in support of that determination and a request made for relief from the ASME Code requirement. After evaluation of the determination pursuant to 10 CFR 50.55a(g)(6)(1), the Commission may grant relief and may impose a

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alternative requirements that are determined to be authorized by law, will not endanger life, property, or the common defense and security, and are otherwise in the public interest, giving due consideration to the burden upon the licensee that could result if the requirements were imposed.

By letters dated April 24 and June 24, 1997, and subsequent revision to Relief Request 12R 22 dated September 9,1997, Wolf Creek Nuclear Operating Corporation (WCNOC), the licensee, requested approval to use an alternative to the 1989 Edition of the ASME Boiler and Pressure Vessel Code,Section XI, in ,

regard to the VT-2 visual ev. amination during system pressure tests, as stated '

in Subsection IWA-5244 for buried Class 3 piping since the provisions of the Code do not address VT 2 visual examination in redundant system: where the i

( Med components are isolable. Pursuant to 10 CFR 50.55a(a)(3)(1), the beensee proposes to apply the requirements of IWA 5244(a) of the same Code -

for VT-2 examination of nonredundant systems which the 1995 Addenda to the '

Code has endorsed. The licensee also proposes a rate of 3ressure loss or flow including corrective measures in the event of exceeding tie specified limit.

The staff has reviewed and evaluated the licensee's request and the supporting information to use the ASME Code Section XI, asprovisions a proposedofalternative IWA 5244(a) of the for VT 1989 Edition 2 examination of the of a redundant system with isolable components such as that of the Essential Service Water System at Wolf Creek Unit 1.

2.0 DISCUSSION Comoonent Identification Buried Class 3 piping on the supply-side of the essential service water system.

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- ASME Code,Section XI, 1989 Edition, Table IWD 2500-1, Examination Categories D A, Item Number D1.10 Examination'Reauirements

The licensee stated that j t

! "The pressure retaining components within the boundary of each system t

shall be pressure tested and VT-2 examined each inspection period and

hydrostatically tested and VT-2 examined each inspection interval.

i VT-2 examination of buried components is performed in accordance with j IWA-5244."

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Ucensee's Relief Reauest/ProDosed Alternative ,

The licensee stated that

" Pursuant to 10 CFR 50.55a(a)(3)(1), relief is requested for the second a ten year inspection interval. Relief is requested to use an alternative testing provision to the currently approved provisions in 10 CFR 50.55a(b). The proposed alternative provision stated below is requested in the absence of a i

of ASME Section XI.pplicable provisions of All other provisions in the IWA1989 5244Edition in the would 1989 Edition continue to be met, except as specifically approved by other relief requests.

l The Essential Service Water (ESW) System is a redundant, isolable system. In the absence of Section XI provisions for redundant, isolable

systems. WCGS proposes to perform a rate of pressure loss test of the underground supply piping of the ESW System in-accordance with the nonredundant, isolable system provisions, subparagraph IWA 5244(a) in the-1989 Edition of Section XI. A rate of pressure loss from the test volume would be quantified by measuring the rate of loss out of identified boundary valves compared with the rate of makeup to the system. For satisfactor test boundary condition,y test performance with the normally expectedthe a 4

l and identified boundary -leakage would be set at 11 gallons per minute

(gpm). The 11 gpm is based on tolerances in measurements and is set as 1

low as reasonably measurable in accordance with the NRC Staff request, 3

Although not part of this relief request, flow rates beyond 11 gm will be evaluated for acceptance in accordance with IWA 5244(a) and IAA-5250(a)(1)."

Licensee's Basis for Relief The licensee stated that "IWA-5244 of the 1989 Edition of ASME Section XI, as approved by 10 CFR 50.55a. does not provide grovisions for testing buried systems that are

" redundant" and " isolable such as the case for the WCNOC ESW System.

Use of the proposed relief request would allow WCNOC to perform the same test prescribed in IWA 5244(a) for nonredundant, isolable systems. The Code prescribed " rate of pressure loss" test would measure the flow rate in gpm going into the isolated (supply side) ESW buried pressure boundary compared to measured leakage (gpm)-through boundary valves.

For satisfactory test performance, the acceptance criteria for comparison of the two measured rates will be 11 gpm. This rate nat been established to comply with the request of the NRC Staff for the acceptance criteria to be as small as reasonably possible to measure.

The acceptance criteria was established based on reasonable tolerances in measurement of the makeup flow going into the system and measurement of the leakage coming out of the normally expected test boundary conditions (three large butterfly valves).

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Flow rates above 11 gpm, indicating probable through wall leakage, will

be evaluated for acceptance in accordance with the NRC currently 4

approved provisions in IWA 5244(a) and IWA 5250(a)(1) in the 1989 Edition of Section XI. At the staff's request. WCNOC will submit information on the acceptable through wall leakage rate in the buried j ESW piping, as soon as preparation of that information is completed.

i Although WCNOC will submit this information, this relief request does j not request any change to the provisions for establishing acceptable

leakage in buried piping contained in the currently approved Section XI.

These currently approved >rovisions require the owner to establish the limits for acceptable leacage loss in buried piping. The acceptable i

through wall leakage rate will be established in accordance with IWA- >

5244(a) and IWA 5250(a)(1) and will meet WCGS conditions for continued

, operations, lWA 5250(a)(1) requires corrective measures, i.e.. locating .

and repairing or replacing the leaking buried piping, when the Owner

specified acceptance criteria has been exceeded. However confirmed

! leakage will be monitored and evaluated by the existing WCNOC corrective action program for appropriate action.

l The ASME Code has rec nized that provisions for testing buried.

redundant. 1solable pi ing were not addressed in previous Editions of Section XI. In tne 19 5 Addenda of Se w on XI, IWA 5244 was revised to l' categorize requirements based on isolability alone. The Code revision broadens the requirements for isolable systems by requiring the same 1 provisions for all isolable buried components, whether they are i redundant or nonredundant systems. This Code revision published in the j 1995 Addenda was approved by the Code consensus process, t

The Code consensus process determined that redundancy vs. nonredundancy 1

was not appropriate criteria for setting requirements. The WCNOC i proposed alternative uses existing test methodology and acceptance criteria determination in the 1989 Edition and applies that methodology regardless of whether the system is redundant or nonredundant. The j- proposed alternative is also in compliance with the 1995 Addenda of IWA-

, 5244. In the absence of testing provisions for redundant, isolable ESW d

System. the proposed alternative demonstrates an acceptable level of

quality and safety."

)_ 3.0 EVALUATION The staff reviewed the licensee's request for relief from the requirements of the ASME Code.Section XI,1989 Edition. subsection IWA 5244 " Buried Components," and determined that the method of VT 2 visual examination during

hydrostatic testing for components in the buried piping stated in the relief request 12R 22. is independent of system classification such as redundant versus non redundant, but depends solely on whether the system is isolable or not. The portion of redundant-essential service water (ESW) piping ystem. "

! - that is buried underground, is isolable and, therefore, can be meanin fully-i VT 2 examined by measuring mass going into the isolated system which s i related to the rate of pressure loss after system pressurization, i

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The licensee has stated that for satisfactory test performance with the normally expected test boundary conditions, the acceptable difference between ,

system makeup and identified boundary valve leakage would be set at 11 g>m which is based on tolerances in measurement and is set as low as reasona)1y measurable. Any flow rate beyond 11 gpm will be evaluated for acceptance in accordance with corrective measures specified in the Code subsection IWA 5250 (a)(1). The staff accepts the specified leakage limit and the proposed disposition of unacceptable system leakage.

The staff finds that by measuring the mass going into the isolated system and relating this to the rate of pressure loss after the system is pressurized, the licensee can adequately determine the structural integrity of the piping, in addition, this alternative test for the buried, redundant, isolable piping in the ESW system is consistent with the testing required by the Code for buried, nonredundant.1solable piping. Based on the above and the fact that applicability / accuracy of the proposed test is independent of system classification (redundant vs. nonredundant), the staff finds the proposed alternative provides an acceptable level of quality and safety.

4.0 CONCLUSION

The staff has determined i.nat the VT 2 visual examination of isolable buried '

components in the redundant essential service water system at the Wolf Creek Generating Station can be performed by a rate of pressure loss test in accordance with the requirements of subsection IWA 5244(a) of the ASME Code,Section XI, 1989 Edition. An acce) table limit on leakage rate of 119)m ba ed on tolerances of measurement and tie licensee's corrective action in tie event of exceeding this leakage, provide an acceptable level of quality and safety, since 11 gpm is the least measurable level of leakage (as low as reasonably l achievable). Therefore, the )roposed alternative to the applicable ASME Code.

Section XI (verification of tie structural integrity of tha' buried ESW piping by measuring the mass going into the isolated system and relating this to the rate of pressure loss after the system is pressurized), as specified in the revision to Relief Request 12R 22 is authorized, pursuant to 10 CFR 50.55a(a)(3)(1) for the second ten year inspection interval of Wolf Creek ,

Generating Station.

Principal Contributor: P. Patnaik k

Date: October 9,1997

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