ML20141B555

SE Accepting First 10-yr Interval Inservice Insp Program Plan Request for Relief NR-29 for Braidwood Station,Units 1 & 2

ML20141B555
Person / Time
Site:	Braidwood
Issue date:	05/13/1997
From:	NRC (Affiliation Not Assigned)
To:
Shared Package
ML20141B538	List: ML20141B533 ML20141B555
References
NUDOCS 9705150332
Download: ML20141B555 (12)

Text

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",'g* t UNITED STATES

! NUCLEAR RECULATORY COMMISSION

", WASHINGTON, D.C. 30006 4 001

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1 f SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION.

OF THE FIRST 10-YEAR INTERVAL INSERVICE INSPECTION PROGRAM PLAN E QUEST FOR RELIEF NR-29 EQB COPMONWEALTH EDISON COMPANY BRAIDWOOD STATION. UNITS I AND 2 DOCKET NOS. STN 50-456 AND STN 50-457 1.0 Df;RODUCTION The Ta nnical Specifications (TS) for Braidwood Station, Units I and 2, state that the inservice inspection (ISI) of the American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code (Code) Class 1, 2 and 3 components shall be performed in accordance with Section XI of the ASME Code and applicable addenda as required by 10 CFR 50.55a(g), except where specific written relief has been granted by the Commission pursuant to 10 CFR 50.55a(g)(6)(1). In 10 CFR 50.55a(a)(3), it states that alternatives to the requirements of paragraph (g) may be used, wh'en authorized by the NRC, if (i) 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 difficulties 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 pre-service examination requirements, set forth in the ASME I Code,Section XI, " Rules for Inservice Inspection of Nuclear Power Plad 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 Code incorporated by reference in 10 CFR 50.55a(b) twelve months prior to the start of the 120-month interval, subject to the limitations and ENCL 059RE 9705150332 970513 PDR ADOCK 05000456 P PDR

__y modifications listed therein. The applicable edition of Section XI of the -

ASr4E Code for the Braidwood Station, Units l' and 2, first 10-year ISI interval is the 1983 Edition through Summer 1983 Addenda.

I 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)(i), the Commission may grant relief and may impose l alternative requirements that are determined to be authorized by law, will not j t endanger life, property, 'or the common defense and security, and are otherwise 1 in the public interest, giving due consideration to the_ burden upon the licensee that could result if the requirements were imposed.

In a letter dated October 8, 1996, Commonwealth Edison Company (Comed, the t licensee), submitted to the NRC its first 10-year ISI interval program plan

< and associated requests for relief for Braidwood Station, Units 1 and 2. The

. licensee requested that the staff expedite its review of Request for Relief NR-29 regarding Weld Nos. IRV-01-003, IRV-01-004, IRV-01-005, IRV-02-001, IRV-02-002 (Unit 1), and 2RV-01-003, 2RV-01-004, 2RV-01-005, 2RV-02-001, 2RV-02-002 (Unit 2). This relief is evaluated below. The licensee also provided additional information in its letters dated February 25, 1997, March 25, 1997, and April 7, 1997.

2.0 EVALUATION The staff, with technical assistance from its contractor, the Idaho National

Engineering and Environmental Laboratory (INEEL), has evaluated the information provided by the licensee in support of its First 10-Year ISI Interval Program Plan Request for Relief NR-29 for Braidwood Station, Units 1 and 2. Based on the information submitted, the staff adopts the contractor's conclusions and recommendations presented in the Technical Letter Report (TLR) attached.

i For Request for Relief NR-29,Section XI, Table IWB-2500-1, Examination  !

Category B-A, Items Bl.11, Bl.21, and Bl.30, requires 100% volumetric '

examination of reactor pressure vessel welds as defined by Figures IWB-2500-1,

-3, and -4, as applicable. Ultrasonic (UT) examinations shall be conducted in

' accordance with Appendix 1. The licensee's proposed, as an alternative pursuant to 10 CFR 50.55a(a)(3)(1), to examine the_ subject areas'using examination procedures, equipment, and personnel qualified by performance demonstration ~in accordance with the Performance Demonstration Initiative ]

(PDI) program. In.the-licensee's letter dated April 7, 1997, it proposed to perform the PDI technique from two directions.

The licensee has contracted with Framatome Technologies (FTI) to use the URSULA manipulator to perform the 10_ Year UT reactor inspections. It is i Braidwood's intent to use the FTI technique qualified in December 1995 to the ,

PDI Program at EPRI NDE Center that meets _the intent of Appendix V!!! of the l L

1992 Edition with 1993 Addenda. This FTI qualified PDI techniqur, consists of i

. scanning the examination volume, weld and base metal, as follows: j 1 ., a - - ~ . .- ,

m.

(1) For, flaw detection, the examidion volume will- be scanned in two directions, one pern ndicular and one parallel to the weld axis. The examination volume is scanned from one direction such that all the ensination angles pass through the ent',re examination volume of interest for each transducer. If full toverage is limited, sc:nrf.ig from both directions will be performed d en coverage can be maximized.

Note: .By letter dated April 7,1997, ths above scanning information was.

superseded. Coned revised thc :ltert;;the to include scans in two opposing directions for examinations perpendicular and parallel to the weld axis.

(2) For flaw characterization (or flaw sizing), the examination will be-conducted from two opposing directions, in the direction perpendicular to'the plane of the flaw, when feasible.

The PDI program was developed by the U.S. nuclear industry to implement selected supplements from the 1992 Edition with 1993 Addenda of Appendix VIII to Section XI of the ASME Code. Appendix VIII was developed to ensure the effectiveness of UT examinations within the nuclear industry by means of a rigorous, item specific, performance demonstration. The performance demonstration is conducted on reactor pressure vessel mockups containing flaws of various sizes and locations. Appendix VIII is not currently a requirement for the licensee.

The licensee has stated that all of the requirements of the 1983 Edition through the Summer 1983 Addenda will be implemented except where specific differences have been identified. A comparison of the differences between the Code prescribed requirements and the PDI qualified procedure is provided F below:

I 1. The examination procedure uses examination angles that are essentially i- the same as those required by the Code. However, the PDI procedure uses a 45'L in place of a 60* shear wave. The PDI procedure has eliminated

i. the O' scan. The O' scan is used to determine the location of

j. laminations that may interfere with the angle beam examination, not for flaw detection. Since the reactor vessel base line examination data include the mapping of laminations that interfere with angle beam i examinations, subsequent O' scans required by Code may be omitted.

Because the PDI procedure angles were capable of detecting the qualification flaws, the PDI procedure angles are considered an acceptable alternative to the Code-required examination angles.

l' 2.- 1he calibration and calibration sensitivity are based on side-drilled hole diameters that are equal to or smaller than those required by the Code. As a result., it is concluded that the sensitivities referenced by F the PDI qualified procedure result in a higher sensit! city than that required by the Code.

3 The examination scanning sensitivity meets or exceeds the requirements of the Code and Regulatory Guide 1.150.

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4. The' scan overlap for the PDI procedure is slightly less than that required by the Code (33% versus 50%). However, because the PDI system l .is calibrated to'a higher sensitivity, the staff believes that the  !

i reduction in overlap allowed in the PDI procedure does not diminish flaw 1 detection capabilities. j

. 5. The PDI procedure will uo tip diffraction for the sizing of flaws. l

, This technique is consid a d superior to the amplitude-based sizing  !

technique required by Code. i

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6. - The , scan speed qualified with the PDI procedure is faster than the scan )

speed allowed by G e Code (up to 9 inches per second versus up to

. 6 inches per second). . However, the INEEL staff believes that the increase in scanning speed is offset by the increased examination sensitivity.

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7. The PDI procedure for crack detection and flaw sizing has been

~;. demonstrated to be capable of detecting and sizing actual cracks in 12 inch thick carbon steel blocks with 0.44 inch stainless steel clad overlay. This qualification approach to flaw detection and sizing is superior to that required by the Code (i.e., qualification based on the ability-to calibrate on side-drilled holes and notches).

! 8. Use of a certified UT Level II examiner qualified by performance based demonstration using flawed samples is superior to Code requirements.

. Based on the comparison of differences between the Code prescribed UT

[ technique and the PDI procedure in er wination with the licensee's revised alternative ;o include scans in two opposing directions for examinations

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perpendicular and parallel to the weld axis, the staff determined that the i PDI procedure is an enhancement over the Code examination technique.

Therefore, the' staff concludes that implementation of the licensee's proposed

' alternative, when all kssociated Code requirements are satisfied, provides an

acceptable level of quality and safety.

3.0 CONCLUSION

S

'The staff has reviewed the information provided by the. licensee in support of

the proposed alternative for Weld Nos. 1RV-01-003, 1RV-01-004, IRV-01-005, IRV-02-001, IRV-02-002 (Unit 1), and 2RV-01-003, 2RV-01-004, 2RV-01-005, 2RV-02-001, 2RV-02-002 (Unit 2). The licensee proposes to implement a PDI qualified.UT procedure for the examination of reactor pressure vessel welds and to include scans in two opposing directions for examinations perpendicular i and parallel to the' weld axis provides an acceptable level. of quality and

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i safety.-

Based on'the information provided alternitive provides an acceptible,level the staff has concluded of quality and safetthat the proposed

. Therefore, i the licensee's proposed alternative is authorized pursuant to 10 CFR '

50.55a(a)(3)(1) for Braidwood Station, Units 1 and 2.

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1 IECHNitAL LETTER REPORT ON THE FIRST 10-YEAR INSERVICE INSPECTION INTERVAL RE0 VEST FOR RELIEF NR-29 COMMONWEALTH EDISON COMPANY BRAIDWOOD POWER STATION. UNITS 1 AND 2 DOCKET NUMBERS: 50-456 & 50-457

1.0 INTRODUCTION

By letter dated October 8, 1996, the licensee submitted Revision 4 to the Braidwood Nuclear Power Station, Units 1 and 2, first 10-year interval inservice inspection program. Revision 4 included corrections to typographical errors, previously approved relief requests, and several new requests. This Technical Letter Report provides expedited evaluation of Relief Request NR-29. In letters dated February 25, 1997, March 25, 1997, and April 7,1997, the licensee provided additional information and clarification regarding Relief Request NR-29. The Idaho National Engineering and Environmental Laboratory (INEEL) staff has evaluated the subject request for relief in the following section.

2.0 EVALUATION i

The Code of record for the Braidwood Nuclear Power Station, Units 1 and 2, first 10-year interval is the American Society of Mechanical Engineers (ASME)

Boiler and Pressure Vessel Code,Section XI, 1983 Edition with the Summer 1983 Addenda. The information provided by the licensee in support of the request has been evaluated and the basis for disposition is documented below.

ATTACHMENT m ,

2.1 Relief Reauest NR-29.Section XI. Table IWB-2500-1. Examination Cateaory-B-A. Items B1.11. Bl.21. and B1.30. Volumetric Examinktion of Reactor Pressure Vessel Shell Welds i

Code Reauirement: Section XI, Table IWB-2500-1, Examination Category B-A, Items 81.11, Bl.21, and 81.30, requires 100% volumetric examination of reactor pressure vessel welds as defined by Figures IWB-2500-1, -3, and -4, as applicable. Ultrasonic examinations shall be conducted in accordance with Appendix I. {

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, Licensee's Proposed Alternative: Pursuant to 10 CFR 50.55a(a)(3)(1),

the licensee proposed to examine the subject areas using a~ Performance Demonstration Initiative (PDI). qualified technique. The licensee

stated

"Braidwood proposes to use FTI's underwater volumetric inspection techniques to inspect the reactor vessel Circumferential shell welds, lower head Circumferential weld and shell to flange weld. FTI's inspection techniques have been demonstrated and qualified to the PDI Program which meets the intent of the rules of Appendix VIII of the ASME

• Code,Section XI, 1992' Edition with 1993 Addenda. These techniques will be used in p hce of the currently required Section XI, 1983 Edition with summer 1983 Addenda, techniques."

! Note: In the April 7,1997, submittal, the licensee stated:

"During the reference teleconference the Staff and Comed specifically discussed Relief Request NR-29 which requested use of one directional 3 Performance Demonstration Initiative (PDI) on the reactor vessel shell welds. Comed understands that at this time the Staff is reluctant to

, approve a one directional examination; therefore, Comed will perform the PDI technique from 2 directions.

Licensee's Basis for the Proposed Alternative (as stated):

" Relief is requested pursuant to the provision of 10 CFR 50.55a(a)(3)(1), the proposed alternative would provide an acceptable level of quality. and safety. j "Braidwood is requesting relief from the Section XI, 1983 Addenda,-

Paragraph IWA-2232 requirements which requires these examirations to be  ;

conducted in accordance with Article 4 of Section V, 1 5 3 tdition with 1

. Summer 1983 Addenda and as amended by Section XI. The attached Table A I l

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' identifies the specific applicable Section V and XI requirements and the proposed corresponding Alternative Performance Demonstration Initiative -

(PDI) technique.

"The Electric Utility industry has developed a program to qualify ultrasonic inspection techniques. This program, Performance

Demonstration Initiative (PDI), is designed to meet the intent of Appendix VIII of.the ASME Code,Section XI, 1992 Edition through 1993 Addenda. This program, PDI, used a variety of test blocks to evaluate transducer designs, scanning reouirements and flaw sizing techniques. l

'"Braidwood has contracted with FNs'one Technologies to use the URSULA manipulator to perform the 10 Year mcasonic (UT) Reactor inspections.

It is Braidwood's intent to use the FTI technique qualified in December  :

1995 to the PDI Program at EPRI NDE Center that meets the intent of Appendix VIII of the 1992 Edition with 1993 Addenda. This FTI qualified PDI technique consists of scanning the examination volume, weld and base metal, as follows: .

f (1) For flaw detection, the examination volume will be scanned in two directions, one perpendicular and one parallel to the weld axis.

The examination volume is scanned from one direction such that all the examination angles pass through the entire examination volume of interest for each transducer. If full coverage is limited, scanning from both directions , vill be performed when coverage can l be maximized.

! i Note: B) letter dated April 7, 1997, the above scanning i information was superseded. Comed revised the alternative to include scans in two opposing directions for examinations perpendicular and parallel to the weld axis.

For flaw characterization (or flaw sizing), the examination will (2) be conducted from two opposing directions, in the direction '

2 perpendicular to the plane of the flaw, when feasible.

In addition, the licensee provided the following comparison table:

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TABLE A i

COMPARISON OF RPV SHELL' WELD EXAMINATION TECHNIQUES-

Description (Code Standard Section V, XI, FTI PDI/ Appendix VIII-1 Reference) Reg. Guide 1.150 Qualified Procedure l Procedure

! Examination Angles Four transducers Three transducers 45'S l (Section V, T-441.1 and required to perform the calibrated on each ASME T-441.6) detection scans 0*, 45' calibration standard l Shear wave, and 60*S based on examination for Code examination thickness range,

, and a 70' Longitudinal usually 9.0" and 5.0" j wave (L) for clad to blocks. The 70' is 1 j base metal interface, calibrated on

Reg Guide 1.150 calibration standard

! requirement. using 1/16" or 1/8" Additional transducers diameter side drilled

! used for sizing holes. Three

. unacceptable flaws. calibration blocks, ten calibrations. 45*S, L 45'L, and 70*L. 45'L and 70*L to examine the inner 10% of thickness.  !

i 45*S and 45'l to examine beyond 10%

thickness.

l Calibrations O*, 45*S, and 60'S One calibration (Section V, T-432 and calibrated on each ASME standard designed to I

T-434) calibration standard establish a calibrated j based on examination time base and i l thickness range, calibration sensitivity l usually 9.0" and 5.0" for each transducer 4 blocks. The 70' is using 1/16" or,1/8" J calibrated on diameter side drilled calibration standard holes. One calibration L using 1/16" or 1/8" standard, three diameter side drilled calibrations.

holes. Three calibration blocks, ten

. calibrations.

i Scanning Sensitivity Section XI,-+6dB beyond Minimum +20dB at the I (Section V, T-425) 25% of thickness. Reg. maximum thickness of Guide 1.150, +14dB for the applicable the first 25% examination volume.

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. COMPARISON OF RPV SHELL WELD EXAMINATION TECHNIQUES Recording Level Section XI, 50% DAC 70*L - 20% DAC, (1/16" (Section V, T- (Code required dia. SDH cal.)

441.3.2.8) reflectors) . Reg. 45'S - 20% DAC, Guide 1.150, 20% DAC (1/8"dia.SDH cal .)

for the first 25% of 45'L - 10% DAC, (1/8" material thickness. dia. SDH cal.)

Scan Index Minimum 50% overlap. 33% overlap for (Section V, T-425 and detection and 73%

amended by paragraph overlap for sizing.

IWA-2232 Flaw Sizing Amplitude based sizing Tip diffraction (Section V, T-441.8) at 50% DAC. Tip techniques using the

diffraction as option same transducers and for flaws determined to calibrations used for exceed IWB-3500 the initial detection acceptance standards scans. FTI qualified 4 based on amplitude the examination sizing. Requires procedure for additional transducers, Supplement 4 and 6 calibration, and sizing using the same scanning. Beam spread transducers and calculations are calibrations used for required. detection. In addition, FTI qualified a forward scatter time-of-flight diffraction (TOFD) technique for the Supplement 4 examination volume as a supplemental technique.

Beam spread calculations are not performed for these techniques.

Scan Speed Up to 6.0" per second. Up to 9.0" per second.

(Section V, T-425)

Procedure Qualification Transducers capable of Performance detecting the demonstration using calibration reflectors cracks. Qualified on in the applicable 12.0" thick samples calibration block. containing a 12.0" wide band of manual clad 0.44" thick.

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i COMPARISON OF RPV SHELL WELD EXAMINATION TECHNIQUES Data Analyst Certified Level II per A minimum of a Code of record (Section certified Level II I XI, Summer 1983 Addenda (Section XI, Summer l and 1980 SNT-TC-1A). 1983 Addenda and 1980 '

SNT-TC-1A) and l qualified by l performance  !

demonstration using flawed samples. ,

_ In the March 25, 1997, submittal the licensee provided the following additional information:

l 1) The licensee verified that all Code requirements except for those ]

j described in the Table will be met. The remaining requirements of ASME Section XI 1983 Edition through the 1983 Summer Addenda will l

. be implemented.

1

2) All essential variables used for the PDI procedure qualification )

- will be implemented for the Braidwood Unit I and 2 inspections. 1 Evaluation: As an alternative to the volumetric examination techniques J prescribed by Code, the licensee has requested approval to implement a l Performance Based Initiative (PDI) qualified ultrasonic examination l

procedure. The licensee has stated that all of the requirements of the 1983 Edition through the Sumer 1983 Addenda will be implemented except where specific differences have been identified. Provided below is a comparison of the differences between the Code prescribed requirements and the PDI qualified procedure:

1

1) The examination procedure uses examination angles that are essentially the same as those required by the Code. However, the PDI procedure uses a 45'l in place of a 60' shear wave. The PDI procedure has eliminated the 0* scan. The 0* scan is used to determine the location of laminations that may interfere with the

, - ~ - - , , . --

i

-7 angle beam examination, not for flaw detection. Since the reactor '

i vessel base line examination data include the mapping of laminations'that interfere with angle beam examinations, l

subsequent 0* scans required by Code may be omitted. Because the PDI procedure angles were capable of detecting the qualification flaws, the PDI procedure angles are considered an acceptable ,

alternative to the Code-required examination t.ngles. l

, 2) The calibration and calibration sensitivity are based on side-

! drilled hole diameters that are equal to or smaller than those i required by the Code. As a result, it is concluded that the ,

l sensitivities referenced by the PDI qualified procedure result in  ;

a higher sensitivity than that required by the Code.

3) The examination scanning sensitivity meets or exceeds the requirements of the Code and Regulatory Guide.l.150.

. 4) The scan overlap for the PDI procedure is slightly less than that required by the Code (33% versus 50%). However, because the PDI i system is calibrated to a higher sensitivity, the INEEL staff ,

I believes that the reduction in overlap allowed in the PDI procedure does not-diminish flaw detection capabilities.

' 5) The PDI procedure will use tip diffraction for the sizing of flaws. This technique is considered superior to the amplitude-  !

based sizing technique required by Code.

6) The rean speed qualified with the PDI procedure is faster than the scan speed allowed by the Code (up to 9 inches'per second versus up to 6 inches per second). However, the INEEL staff believes that the increase in scanning speed is offset by the increased 4

examination sensitivity.

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7) The PDI procedure for crack detection and flaw sizing has been

! demonstrated to be capable of detecting and sizing actual cracks in 12 inch thick carbon steel blocks with 0.44 inch stainless steel clad overlay. This qualification approach to flaw detection and sizing is superior to that required by the Code (i.e.,

qualification based on the ability to calibrate on side-drilled holes and notches).

8) Use of a certified ultrasonic Level II examiner qualified by performance based demonstration using flawed samples is superior to Code requirements.

Based on the information provided and the comparison of differences between the Code prescribed ultrasonic technique and the PDI procedure, l- in combination with the licensee's revised alternative to include scans in two opposing directions for examinations perpendicular and parallel j to the weld axis, it can be concluded that the PDI procedure is an enhancement over the Code examination technique. As a result, the INEEL I staff believes that implementation of the licensee's proposed alternative, when all associated Code requirements are satisfied, provides an acceptable level of quality and safety.

3.0 CONCLUSION

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The INEEL staff has reviewed the information provided by the licensee in support of the proposed alternative. The licensee proposes to implement a PDI l l qualified ultrasonic procedure for the examination of reactor pressure vessel

welds. Based on the information provided, it has been determined that the proposed alternative that includes scans in two opposing directions for l l examinations perpendicular and parallel to the weld axis will provide an

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acceptable-level of quality and safety. Therefore, it is recommended that the licensee's proposed alternative be authorized pursuant to 10 CFR 50.55a(a)(3)(1) for Braiowood I and 2.

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