ML20199J684

SER Approving Relief Requests to Second 10-year Inservice Inspection Interval for Duane Arnold Energy Center

ML20199J684
Person / Time
Site:	Duane Arnold
Issue date:	11/21/1997
From:	NRC (Affiliation Not Assigned)
To:
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ML20199J672	List: ML20199J669 ML20199J684
References
NUDOCS 9711280200
Download: ML20199J684 (9)

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yefY.p aroy%,t UNITED STATES

. s* jt NUCLEAR REGULATORY COMM'3SION WASHINGTON, D.C. toteHoot

• • • • • SAFET [ Y EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION OF THE REllEF REQUESTS TO THE SECOND 10-YEAR INSERVICE INSPECTION INTERVAL IES UTILITIES INC.

DUANE ARNOLD ENERGY CENTER QQCKET NUMBER 50 331

1.0 INTRODUCTION

The Technical Specifications for the Duane Arnold Energy Center state that the inservice inspection (ISI) 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 50.65a(g), except where specific written relief has been granted by the Commission pursuant to 10 CFR 50.55a(g)(6)(l). 10 CFR 50.55a(a)(3) states that alternatives to the requirements of paragraph (g) may be used, when authorized by the NRC, if (i) the proposed alternatives would prwide 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 C!sss 1,2, and 3 components (including supports) shall meet the requirements, except the design and access provisions and the preservice examination requirements, set forth in the ASME Code,Section XI, " Rules for Inservice Inspection of Nuclear Power Plant Components," to the extent practical within the limitations of design, geometry, and materials of construction of the components. The regulations require that inservice examination of components and system pressure tests conducted during the first 10-year interval and subsequent intervals comply with the requirements in the latest edition and addenda of Section XI of the ASME Coue incorporated by reference in 10 CFR 50.55a(b) 12 months prior to the start of the 120-month inte. val, subject to the limitations and modifications listed therein. The applicable ASME Code,Section XI, for the Duane Arnold Energy Center second 10-year ISI interval is the 1980 Edition through Winter 1981 addendum. 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 modifications listed therein and subject to Commission 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 Enclosure 9711290200 971121 PDR ADOCK 05000331 G PDR

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. 2 determination, pursuant to 10 CFR 50.55alg)(6)(i), the Commission may grant relief and I may impose alternative requirements that are determined to be authorized by law, will not endanger lif e, property, or the common defense and security, er d 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 June 26, and September 15,1997, IES Utilities Inc., the licensee for the Duane Arnold Energy Center, submitted to the NRC its requests for relief from the examination requirement of the applicable ASME Code,Section XI, for the second ISI interval examinations. The staff has reviewed and evaluated the licensee's Relief Request Nos. NDE-022 through NDE 026 for the second 10-year ISI interval of the Duane Arnold Energy Center.

2.0 DISCUSSION (REQUEST FOR RELIEF No. NDE-022)

a. SYSTEM / COMPONENT (S) FOR WHICH REllEF IS REQUESTED HEA-CB 2 Residual Heat Removal System Residual Heat Removal (RHR) Heat Exchanger Nozzle Inner Radius Examination Category C B, item C2.22

b. CODE REQUIREMENT Section XI (1950 Edition with W81 Addendum), Table IWC-2500-1 Category C-B, item C2.22 requires a volumetric examination which includes essentially 100% of the inner radius once during the 10-year interval. The examination volume is defined in Fig.

lWC 2500-4.

c. CODE REQUIREMENT FROM WHICH REllEF IS REQUESTED Relief is roquested from the performance of the vuiumetric examination of essentially 100% of the nozzle inner radius as described in Fig. IWC 2500-4 for residual heat romoval (RHP' Heat Exchanger Weld HEA-CB-2.

d. BASIS FOR REllEE This weld is a nozzle to shell configuration which limits the volumetric (UT) coverage to a one-sided exam. In addition, the nozzle is located next to the tube sheet flange which limits the volumetric examination coverage. This results in approximately 75% UT coverage of the inner radius, it is not possible to perform a radiography of these welds and be able to detect potential flaws. Performing vadiography would require the Residual Heat Removal System to be drained and either the pipe or tube sheet opened to provide access to the inside diameter.

(Removal of the tube sheet is not an option because several tubes would be required to be

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3 removed along with the tube sheet.) Draining the pipe increases the dose rates in the area by a f actor of 1.7 (20 mr/hr vs 12 mr/hr). This results in additional personnel exposure of 50 mr, including the installation and removal of insulation and shielding, in addition, removing the pipe from the nozzle would require the pipe to be cut in two places and then rewelded which would take approximately 102 hours0.00118 days <br />0.0283 hours <br />1.686508e-4 weeks <br />3.8811e-5 months <br />. Additional examinations would then be required for the welds that reattach the pipe to the system. The total dose for the project would be approximately 2R. The additional 25% coverage would provide only a small potential for increasing plant safety while greatly increasing expenditures of plant manpower and radiation exposure.

e. ALTERNATE EXAMINATIONS IES Utilities Inc. proposes to perforrr volumetric examination of approximately 75% of the nocle inner radius. The alternative examination coverage of 90% as allowed by Code Case N-460 will alco be used.

f. IMPLEMENTATION SCHEDULE This relief request will be implement id in supoort of the second 10-year interval. This examination was included in the Refueling Outage (RFO) 14 Summary Report.

g. EVALUATION AND CONCLUSION in accordance with the ASME Code Case N-460, it is permissible to examine over 90% of the nozzle inner radius to comply with the requirement of the ASME Code,Section XI. The staff has determined that the volumetric examination of approximately 75% of the nozzle inner radius which is examinable with the licensee's best effort does provide a reasonable assurance that signUicant degradation, if present, would have been detected. In order to perform an alternate volumetric examination such as radiography to comply with the requirement of the Code, the system has to be drained and an access provided to the inside of the heat exchanger which would result in hardship in terms of high man-rem to licensee's personnel without a compensating increase in safety. With the volumetric examination of approximately 75% of nozzle inner radius and the VT-2 visual examination performed during the Code required system pressure test, reasonable assurance of operational readiness of the RHR Heat Exchanger is provided. The staff concludes that compliance with the applicable ASME Code,Section XI, would result in hardship without a compensating increase in the level of quality and safety. Therefore, the alternate examination proposed in Relief Request No. NDE-022 is authorized pursuant to 10 CFR 50.55ata)(3slii) for the second 10-year inspection interval.

2.1 DISCUSSION (REQUEST FOR RELIEF NO. NDE-023)

a. SYSTEM /COMPONENTIS) FOR WHICH REllEF IS REQUESTED HCC-C001 Reactor Pressure Head to Flange Weld and VCB-C005 Reactor Pressure Vessel to Flange Weld Examination Category B-A, items B1.30 and B1.10.

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b. CODE REQUIREMENI Section XI (1980 Edition with W81 Addendum), Table IWB-250n.1 Category B-A, Item B1.30 and B1.40 requires a volumetric examination which incloses essentially 100% of the weld once during the 10-year interval. The examination volume is d<ned in Fig. lWB- -

2500-4 and -5.

c. CODE REQUIREMENT FROM WHICH REllEF IS REQUESTED Relief is requested from performing a volumetric examination of essentially 100% of the vessel to flange weld (VCB-C005) and head to flange weld (HCC-C001),

d. BAS $ FOR REllEF These welds are vessel to flange and head to flange welds which limit the volumetric (UT) coverage to a one-sided exam. In addition, the weld configuration limits the one-sided exam to approximately 42.7% and 36.8% UT coverage respectively. It is not possible to perform a radiography of these welds and be able to detect potential flaws. Performing a -

surface examination would also not detect the type of flaws that would be expected (i.e.,

within the volume of the weld). In accordance with 10 CFR 50.55a(6)(i), relief requests may be granted when the examination is shown to be impractical,

e. ALTERNATE EXAMINATIONS IES Utilities Inc. proposes to perform volumetric examination of approximately 42.7% of the vessel to flang weld and 36.8% of the head to flange weld. The alternative examination coverage of 90% as allowed by Code Case N-460 will also be used,

f. IMPLEMENTATION SCHEDULE This relief request will be implemented in support of the second 10-year interval. This exam was included in the Refueling Outage (RFO) 14 Summary Report.

g. EVALUATION AND CONCLUSION in accordance with the ASME Code Case N-460,it is permissible to examine over 90% of the weld volume to comply with the requirements of the ASME Code,Section XI. The configurations of the vessel to flange and the head to flange welds do not allow UT examination of the welds from both sides to obtain Code-required volumetric coverage.

The staff has determined that it is impractical to comply with the Code requirement due to the weld configurations. If the requirements of the applicable Code were to be imposed on the licensee, the vessel has to be redesigned and replaced. The staff further determined that the subject welds cannot be meaningfully examined by radiography to meet the Code requirements. The volumetric examination coverage obtained for each weld provides reasonable assurance that the presence of any significant degradation woeld have been detected. The staff, therefore, concludes that based on the impracticability of complying

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wRh the Code requirements and the burden on the licensee if the Code requirements were imp) sed, Relief Request No. NDE-023 is granted pursuant to 10 CFR 50.55a(g)(6)(i) for the second 10-year inspection interval.

2.2 DISCUSSION (REQUEST FOR REllEF NO. NDE-024)

a. SYSTEM / COMPONENT (S) FOR WHICH RELIEF IS REQUESTED VSW 0 Reactor Pressure Vessel Stabilizer Weld, VSW 90 Reactor Pressure Vessel Stabilizer Weld, VSW-180 Reactor Pressure Vessel Stabilizer Weld, and VSW-270 Reactor Pressure Vessel Stabilizer Weld Examination Category B-H, item B8.10

b. CODE REQUIREMENT Section XI (1980 Edition with W81 Addendum), Table IWB-25001 Category B-H, item i 88.10 requires a surface examination which includes essentially 100% of the weld once during the 10-year interval. The examination surface is defined in Fig. IWB 250015.

c. CODE REQUIREMENT FROM WHICH RELIEF IS REQUESTED Relief is requested from performir.g a surface examination of essentially 100% of the vessel stabilizer integral attachment welds (VSW-0, 90, -180, and 270).

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d. BASIS FOR RELIEF These welds integrally attach lugs to the vessel by a "V gronve" weld. The lugs are used ,

to connect the vessel stabilizers to the vessel. The stabilizers prevent the necessary access to perform the surface examination of the bottom side of the lug. In addition, the close proximity of the lug to the vcssel prevents access. The vessel stabilizers would require disassembly in order to provide the access necessary to complete the examination of 100% of the bottom weld. The stabilizers were installed and tensioned with a Biach Industries 500,000# tensioner. After a 24 hour2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> period, the stabilizers were rechecked for a 290 kips residualload. D;sassembly of the vessel stabilizers to provide access to the bottom weld would require extensive manpower and exposure. Examining the bottom weld would provide only a 8 mall potential for increasing plant safety while greatly increasing expenditures of plant manpower and radiation exposure. In accordance with 10 CFR 50.55a(g)(6)(i), relief requests may be granted when the examination is shown to be impractical.

e. ALTERNATE EXAMINATIONS lES Utilities Inc. proposes to perform a surface examination of approximately 60% of the vessel stabilizer attachment welds which includes the top and sides of each stabilizer lug.

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f. IMPLEMENTATION SCHEDULE This relief request will be implemented in support of the second 10-year interval. VSW-0 was examined in RFO 9. VSW 90 was examined in RFO 10. VSW 180 and VSW 270 were examined in RFO 14.

g. EVALUATION AND CONCLUSION The applicable ASME Code,Section XI, Category B-H, item B8.10, requires surface examination of essentially 100% of subject attachment welds of lugs that are used to ,

connect the vessel stabilizer to the recctor vessel. The vessel stabilizer that is bolted to the lug prevents access to the bottom weld of the lug to perform the required surface examination. The licensee is able to perform a surf ace examination covering 60% surf ace area of each lug attachment weld without removal of the stabilizer. The disassembly of the stabilizer is manpower intensive and is associated with high radiation penalty. The staff has determined that surface examination of approximately 60% of the vessel stabilizer attachment welds provides .easonable assurance that significant degradation, if present, would have been detected. Therefore, the proposed testing has addressed the structural integrity concems related to the lug attachment welds to a reasonable extent. The disassembly of the vessel stabilizers, for the sole purpose of accessing the bottom weld for surface examination, would result in hardship without a compensating increase in safety.

Therefore, the attemative examination proposed in Relief Request No. NDE-24 is authorized pursuant to 10 CFR 50.55ata)(3)(ii) for the second 10-year inspection interval.

2.3 DISCUSSION (REQUEST FOR RELIEF NO. NDE-025)

a. SYSTEM / COMPONENT (S) FOR WHICH RELIEF IS REQUESTED Nozzle to-vessel welds Examination Category B-D, item t.lo. B3.90

b. CODE REQUIREMENT Section XI (1980 Edition with W81 Addendum), Table IWB-2500-1 Category B-D, item B3.90 requires a volumetric examination which includes essentially 100% of the weld once during the 10-year interval. The examination volume is defined in Fig. lWB-2500-7(b).

c. CODE HEQUIREMENT FROM WHICH REllEF IS REQUESTED Relief is requested from performing volumetric examination of essentially 100% of the nozzle-to-vessel weld volume for those nozzles affected.

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d. BASIS FOR REllEF Due to the design of these welds,it is not feasible to effectively perform a volumetric examination of 100% of the volume described in IWB-2500-7(b). The nozzle to-vessel welds are accessible from the vessel side, but examination cannot be performed from the nozzle side because of the taper, in accordance with 10 CFR 50.55a(g)(6)(i), relief requests may be granted when the examination is shown to be impractical.

c. ALTERNATE EXAMINATIONS IES Utilities Inc. proposes to perform volumetric examination from the vessel side of the nozzle to-vessel welds which are included in the attached list. Because of the design of the nozzle to-vessel welds, there are no known alternative examination techniques currently available to increase the examination volume,

f. IMPLEMENTATION SCHEDULE This relief request will be implemented in support of the second 10 year interval. The attached list to IES Utilities' September 15,1997, letter indicates the period when each nozzle to-vessel weld was examined.

g. EVALUATION AND CONCLUSION in accordance with the ASME Code Case N-460, it is permissible to examina over 90% of ti e weld volume to comply with the requiremente of the ASME Code.Section XI. The configurations of the nozzle-to-vessel welds do not allow ultrasonic (UT) examination of the welds from the nozzle side and are accessibb from the vessel side. The staff has determined that it is impractical to comply with the Code requirement due to the weld configurations. If the requirements of the applicable Code were to be imposed on the licensee, the vessel has to be redesigned and replaced. The staff further determined that the subject welds cannot be examined by alternative techniques to meet the Code requirements. However, the volumetric examination coverage obtained for each weld, as indicated in the licensee's submittal, provides reasonable assurance that the presence of any significant degradation would have been detected. The staff, therefore, concludes that based on the impracticability of complying with the Code requirements and the burden on the licensee if the Code requirements were imposed, Relief Request No. NDE-025 is granted, pursuant to 10 CFR 50.55a(g)(6)(i) for the second 10-year inspection interval.

2,4 DfSCUSSION (REQUEST FOR RELIEF NO. NDE-026)

a. SYSTEM / COMPONENT (S) FOR WHICH REllEF IS REQUESTED Vessel Clusure Head Threada in Flange Examination Category 8-G-1, B6.40

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b. CODE REQUIREMENT Section XI (1980 Edition with W81 Addendum), Table IWB-2500-1 Category B-G 1, item B6.40 requires a volumetric examination which includes 1 inch around the vessel bushing (when installed) as referenced in Figure IWB 250012 once during the 10-year interval,

c. CODE REQUIREMENT FROM WHICH RELIEF IS REQUESTED Relief is requested from performing volumetric examination of essentially 100% of the 1 inch annular area required by IWB 2500-12.

d. BASIS FOR REl. LEE The 1 inch annular area required by IWB-250012 to be examined encompasses the flange sealing surf ace area. This ligament examination is limited due to the proximity of the flange sealing surf ace. A total of approximately 77.1% of the examination volume can be achieved. The sealing surface does not allow examination of a 4 inch and 4.3 inch area on both sides of the stud which interfaces with the sealing surface. This is due to the flange configuration and the O-ring groove, in accordance with 10 CFR 50.55a(g)(6)(i) relief requests may be granteri when the examination requirements are shown to be impractical.

c. ALTERNATE EXAMINATIONS lF.S Utilities Inc. proposes to perform volumetric examination of 77.1% of the flange ligament once per interval.

f. IMPLEMENTATION SCHEDULE This relief request will be implemented in support of the second 10-year interval,

g. EVALUATION AND CONCLUSION in accordance with the ASME Code Case N-460,it is permissible to examine over 90% of the weld volume to comply with the requirements of the ASME Code,Section XI. The volume encompassing the 1 inch annular surface area required to be examined is limited in access for scanning due to the raised sealing surface and the O-ring groove on the flange.

The staff has determined that it is impractical to comply with the Code requirement due to the flange configuration. If the requirements of the applicable Code were to be imposed on the licensee, the flange has to be redesigned and replaced. The staff further determined that the annular area cannot be examined by any alternative method to meet the Code requirements. However, the volumetric examination coverage of 77.1% obtained for this ligament examination provides reasonable assurance that the presence of any significant degradation would have been detected. The staff, therefore, concludes that based on the impracticability of complying with the Code requirements and the burden on the licensee if

. g the Code requirements were imposed, Relief Request No. NDE 026 is granted pursuant to 10 CFR 50.55a(g)(6)(i) for the second 10-year inspection interval.

3.0 CONCLUSION

The staff has evaluated information provided by IES in its relief requests and any alteratives proposed by the licensee. For relief requests NDE 22 and NDE 24, the staff has determined that compliance with the Code will result in hardship or unusual difficulty without a compensating increase in the level of quality and safety. Thsrefore, the alternatives proposed are authorized pursuant to 10 CFR 50.55a(a)(3)(ii). For relief requests NDE 23,- NDE 25, and NDE 26, the staff has determined that the requirements of the Code are impractical and relief is granted for the second 10 year inspection interval pursuant to 10 CFR 50.55a(g)(6)(i). _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 given due consideration to the burden upon the licensee that could result if the requirements were imposed on the facility.

Principal Contnbutor: Prakash Patnaik .

Date: November 21, 1997-

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