ML20198C767
| ML20198C767 | |
| Person / Time | |
|---|---|
| Site: | Point Beach  |
| Issue date: | 12/10/1998 |
| From: | NRC (Affiliation Not Assigned) |
| To: | |
| Shared Package | |
| ML20198C757 | List: |
| References | |
| NUDOCS 9812220162 | |
| Download: ML20198C767 (7) | |
Text
- .- _ . - . = - . ._. ._
., f"h
! p 51 UN!TED STATES
,j NUGLEAR REGULATORY COMMISSION WASHINGTON, D.C. 30666 0001 I
,Q as (nV4 s* $
! l SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION ON THE THIRD 10-YEAR INSERVICE INSPECTION INTERVAL RELIEF REQUEST RR-2-24 WISCONSIN ELECTRIC POWER COMPANY POINT BEACH NUCLEAR PLANT,fNIT 2 DOCKET NO. 50-301 l
1.0 INTRODUCTION
l By letter dated November 2,1998, the Wisconsin Electric Power Company (WEPCo or the licensee) requested to use the Performance Demonstrat!on initiative (PDI) Program based on the criteria of Appendix Vill,Section XI of the ASME Code,1992 Edition, including the 1993 ;
Addenda as an alternative to the requirement of the 1986 Edition of ASME Code,Section XI, '
for ultrasonic examination of reactor vessel welds in Point Beach Nuclear Plant (PBNP) Unit 2.
Inservice inspection 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 (B&PV) 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(6)(g)(i).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 provide an acceptable level of quality and safety or (ii) complisnce 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 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 Code incorporated by reference in 10 CFR 50.55a(b) 12 months prior to the start of the 120-month interval, subject to the limitations and modifications listed therein. The applicable ASME Code,Section XI, for the l
PBNP third 10-year ISI interval is the 1986 Edition, no addenda. 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.
ENCLOSURE 4
9812220162 981210 PDR ADOCK 05000301 G PDR ,
2 Pursuant to 10 CFR 50.55a(g)(5), if the licensee determines that conformance with an j 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 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. Pursuant to 10 CFR 50.55a(a)(3)(i), proposed alternatives to the requirements of
- paragraphs (c), (d), (e), (f), (g), and (h) of 10 CFR 50.55a may be used when authorized by the Director of the Office of Nuclear Reactor Regulation and the applicant can demonstrate that the proposed alternatives would provide an acceptable level of quality and safety.
l The staff has reviewed and evaluated the licensee's request and supporting information on the proposed alternative to the Code requirements for Point Beach Unit 2 pursuant to the provisions of 10 CFR 50.55a(a)(3)(i).
i 2.0 DISCUSSION Comoonent identification:
Reactor Pressure Vesse! Unit 2 The PDI technique will be used to ultrasonically examine the following welds. j Circumferential Welds
- a. RPV-15-683 Upper Shell to Middle Shell
- b. RPV-16-683 Middle Shell to Lower Shell
- c. RPV-17-683 Lower Shell to Lower Head Ring - !
- d. RPV-18-683 Lower Head Ring to Lower Head A combination of PDI and the ASME Code techniques will be used to examine the following welds.
Reactor Vessel-to-Flance Weld l
- e. RPV-14-683-A Shell to Flange (Azimuth 0-180)
- f. RPV-14-683 B Shell to Flange (Azimuth 180-360)
Nozzle to-Shell Welds
- g. RPV-2-686-A Shell to Outlet Nozzle at 28.5 degrees l h. RPV-2-686-B Inlet Noz21e to Shell at 148.5 degrees l 1. RPV-2-686-C Shell to Outlet Nozzle at 206.5 degrees
- j RPV-2-686-D Inlet Nozzle to Shell at 328.5 degrees
! k. RPV-687-01-A Safety injection Nozzle to Shell at 288.5 degrees ,
- 1. RPV-687-01-B Safety injection Nozzle to Shell at 108.5 degrees i i
I
l ,.
3 I Exam Areas IWB-2500-1,3,4,7 ASME Section XI Cateaorv B-A - welds (a) through (f) above B-D - welds (g) through (i) above ASME Section XI ltem Number 81.11 - welds (a) and (b) above B1.21.- welds (c) and (d) above B1.30 - welds (e) and (f) above B3.90 - welds (g) through (1) above Code Reauiremant:
ASME Section XI,1986 Edition, no Addenda, Table IWB-2500-1 requires volumetric examination for these welds. The requirements for volumetric examinations are stated in Article IWA-2232, which states that examinations be conducted in accordance with Article 4 of ASME Code,Section V, as amended by ASME Code,Section XI.
Proposed Alternative: (as stated)
Examination procedures, equipment, and personnel qualified by performance ;
demonstration will be utilized in accordance with the Performance Demonstration l Initiative (PDI) Program, in combination with ASME Code,Section V, Article 4 techniques. The following techniques will be utilized for the proposed welds: l
- 1) Welds (a) through (d) above will be examined with PDI techniques only.
- 2) Welds (e) and (f) above will be examined from the seal surface using ASME Code techniques for detection of flaws parallel to the weld plane.
Examination for transverse and parallel flaws will be conducted from the ;
vessel inside surface using PDI techniques.
- 3) Welds (g) through (1) above will be examined with PDI techniques from the vessel wall for detection of transverse reflectors. For detection of flaws that are parallel to the weld, examinations will be conducted from the nozzle bore using ASME Code techniques.
A comparison of the proposed PDI technique for PBNP and the standard Article 4,Section V and Regulatory Guide 1.150 (" Ultrasonic Testing of Reactor Vessel Welds During Preservice l and Inservice Examinations") procedures are given in the table attached to this safety l evaluation.
As a minimum, all Code requirements of the 1986 Edition of Section XI will be implemented, except where specific differences have been identified. In addition, it is the licensee's intention I
4 to satisfy the 10 CFR 50.55a(g)(6)(ii)(A), " Augmented," reactor pressure vessel (RPV) inspection requirements.
FEASON FOR PROPOSED ALTERNATIVE REQUIREMENT:
WEPCo has contracted with Southwest Research Institute (SwRI) to perform the third 10-year RPV examination using a combination of the PDI qualified techniques and ASME,Section V, Article 4 techniques. SWRI's procedures were qualified in accordance with the PD! program covering Supplement 4, " Qualification Requirements for the Clad / Base Metal Interface of Reactor Vessel," and 6," Qualification Requirements for Reactor Vessel Welds Other than Clad / Base Metal Interface," of Appendix Vill,Section XI, ASME Code. Both double and single-sided approaches were qualified for Supplement 4 applications and for Supplement 6 applications up through 12-inch wall thicknesses. (SwRl's PDI certification is on file at the Electric Power Research Institute Non-Destructive Enmination Center in Charlotte, NC.)
SwRI's PDI detection procedure utilizes two types of search units (55 degrees, multibeam) when scanning can be accomplished from two sides of the weld, and three types of search units (45,55, and multibeam) when scanning can be accomplished from one side of the weld.
The multibeam search unit is used to examine the inner 25-percent thickness. The 45- and 55-degree shear-wave search units are used to examine the outer 75 percent. A 0-degree search unit may also be used to detect laminar reflectors and determine component thickness.
(NOTE: WEPCo has instructed SwRI to scan from two sides of each weld whenever possible.)
Scanning is performed (1) perpendicular to the weld for flaws oriented parallel to the weld; and (2) parallel to the weld for flaws oriented perpendicular (transverse) to the weld. Flaw discrimination methods are independent of signal amplitude. Scanning sensitivities are redetermined based on the actual material noise.
Analysis and sizing of indications are performed by qualified Level Ill Data Analysts using SwRI procedures. Regardless of whether the detection examinations are being performed per ASME Code or PDI procedures, SwRI's sizing procedures utilize tip-diffraction methods qual!fied in accordance with the PDI guidelines.
3.0 EVALUATION The PDI program based on the criteria of Appendix Vill,Section XI of the ASME Code,1992 Edition,1993 Addenda, requires that ultrasonic equipment, procedures, and examiners perform a performance demonstration on flawed and notched materials and configurations similar to those found in actual plant conditions. Hence, performance-based ultrasonic examination techniques provide a higher degree of reliability for detection and characterization of flaw when compared to the conventional emplitude-based ultrasonic techniques required by the current Code. The staff has assessed the PDI program activities and has approved the use of PDI techniques at other sites.
Based on the information provided by WEPCo, the staff has evaluated the PDI program proposed for ultrasonic examination of RPV welds at PBNP Unit 2 during the third 10-year inspection interval. The staff compared the licensee's proposed examination technique based on PDI qualifications with that of the current Code and the Regulatory Guide 1.150 and determined that the PDI-qualified technique would provide better sensitivity to flaw detection than that of the currently applicable standards. Furthermore, the sizing and evaluation of a flaw
N 5
j is more accurate using a multibeam tip-diffraction technique under the licensee's proposed PDI program than the amplitude based flaw sizing allowed by the current Code. Additionally, whenever feasible WEPCo will scan the examination volume from both sides of the weld on the same surface. However, when configuration or adjacent parts of the component are such that scanning from both sides is not feasible, the percent of coverage shall be included in the report i of examination. Therefore, the staff has determined that the proposed alternative to use UT
, techniques qualified under the PD) program for the reactor vessel examination provides an equivalent or a better examination than that of the current standards and will provide assurance of structuralintegrity.
4.0 CONCLUSION
The staff has reviewed and evaluated the licensee's proposed alternative to implement the PDI program for the reactor vessel examination at PBNP Unit 2 during the third 10-year inspection I interval. A comparison of the ultrasonic testing technique used in the PDI with that of the current Code and Regulatory Guide 1.150 indicates that the PDI technique provides an equivalent or a better examination of the reactor vessel than that of the governing standards.
Scanning of the examination volume will be carried out from both sides of the weld on the same i surface wherever feasible. Hence, the staff has determined that the proposed alternative provides an acceptable level of quality ar d safety. Therefore, the proposed alternative may be authorized, pursuant to 10 CFR 50.55a(a)3)(i) for the reactor vessel examination during the third 10 year interval at PBNP Unit 2.
Attachment:
Table Principal Contributor: B. Wetzel l
Date: December 10, 1998 i
Attachment to NPL 98-0931 N2vember 2, I998 -
ATTACHMENT 2 -
P ge1 COMPARISON OF REACTOR PRESSURE VESSEL SHELL WELD EXAMINATION TECHNIQUES tandweetion V, M, Description (Code Reference) SwRI PDI/ Appendix VIII Qualified Procedure Regulatory Guide 1.150 Procedure Examination Angles Four transducers required to perform the detection Two types of search units; a multibeam search (Section V, T-441) scans 0*,45*, and 60*, plus a multibeam transducer unit and 55* search unit are used to perform the i for clad-to-base metal interface (Regulatory double sided detection examinations. !
Guide 1.I50 requirement)is used.
Three types of search units, multibeam,45* and 55* are used for single-sided detection examinations. The multibeam search units are i
used to examine the near surface; and the 45* and 55* search units are used to examine the remainder of the wall. These examination angles were successfully qualified under the PDI protocol using the PDI program test blocks. ,
Instrument Calibrations Section V requires that instrument screen height SwRrs PDI-qualified procedure does not require (Section V, T-431,Section XI, and amplitude control linearity be evaluated at least that linearity checks be perfonned on site before ,
IWA-2232) every three months.Section XI requires that these and after examinations because amplitude y linearity checks be performed before and after the linearity is not relied upon for evaluation of E examinations performed during one outage. flaws. SwRI does perform instrument linearity S checks at least every 6 months as part of the i
$ maintenance and instrument certification process.
[ System Calibrations Requires that the original system calibration be One calibration standard is used for the
- (Section V, T-432) performed on the Code basic calibration block. It multibeam search unit and another standard is B
" allows the use of difTerent types of reference blocks used for the 45* and 55* search units. These and electronic simulators to perform system standards contain a series ofside drilled holes and ;
calibration verifications. are used to establish a calibrated time base and initial sensitivity. Periodic sweep calibration h checks are made and sensitivity checks are made on the vessel wall.
i r
~ .
Attachment to NPL 98-0931 -
November 2,1998 -
ATTACHMENT-2 . I Page 2 -
COMPARISON OF REACTOR PRESSURE VESSEL SHELL WELD EXAMINATION TECHNIQUES :
StandW Section V, M, Description (Code Reference) SwRI PDI/ Appendix VIII Qualified Procedure !
Regulatory Guide 1.150 Procedure i Scanning Sensitivity Scanning is performed at the reference level Initial sensitivity is increased, if necessary, until (Section V, T-424) sensitivity when electronic distance amplitude background noise from the material in the I correction (DAC) is used for automated examination area equals a level specified in the !
examinations. qualified procedure. This method ifdetermining e scanning sensitivity was successfully qualified .
under the PDI protocol using the PDI program test blocks -
Recording Level Section V requires recording and evaluation of 50% No amplitude thresholds are used. Data are (Section V, T-441) DAC. Regulatory Guide 1.150 requires recording recorded and evaluated independently of signal l and evaluation at 20% DAC for the inner 25% of amplitude. This evaluation method was l
material thickness. successfully qualified under the PDI protocol using the PDI test blocks.
Scan Index, Pulse Repetition Rate Section V requires a minimum increment overlap of Scanning overlap is 10% for the near surface (Section V,T-424 and Section XI, 10% of the dimension of the pie,:oelectric element multibeam searth units and 40% for the other IWA-2232) between scans.Section XI requires 50% overlap detection search units, as qualified under the PDI when not scanning in beam direction. Regulatory protocol using the PDI test blocks. Pulse ;
Guide 1.150 requires 25% minimum overlap for repetition rate is set such that data are collected at ;
detection and 0.25" maximum increment for 0.040 inch increments in the direction of scan.
characterization.Section XI also requires a pulse i repetition rate sufficient to provide at least 10%
l overlap of the minimum beam dimension.
i Flaw Sizing and Evaluation Amplitude based sizing at 50% DAC. Other Multibeam tip difTraction techniques are used for !
(Section V, T-441 and T 451) techniques and methods may be used. through-wall sizing. The length sizing is ;
accomplished using amplitude drop methods. ,
Beam spread calculations are not performed for these techniques.
l i
_ - _ . _ _ _ _ _ _ _ _ . _ . - _ - - _ _ _ _ _ _ - _ . _ _ _ _ _ _ - _ _ - _ _ _ _ _ _ _ _ _ _ _ _ _ _ - - _ - _ _ _ _ _ _ _ - _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ - _ - _ - _ _ _ _ - - _ _ _ _ _ . _ _ _ - - _ -