NOC-AE-11002633, Amended Request for Relief from ASME Section XI Code Requirements for Reactor Pressure Vessel Flange Insert Non-Destructive Examination (Relief Request RR-ENG-3-02)
| ML110460034 | |
| Person / Time | |
|---|---|
| Site: | South Texas  |
| Issue date: | 02/07/2011 |
| From: | Ruvalcaba M South Texas |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| NOC-AE-11002633, RR-ENG-3-02, TAC ME4764, TAC ME4765, G25, STI: 32816552 | |
| Download: ML110460034 (11) | |
Text
Nuclear Operating Company South Tes Pro/ect Electric GeneratingStation PO Box 289 Wadsworth, Tesas 77483 February 7, 2011 NOC-AE-1 1002633 File No.: G25 10 CFR 50.55a U. S. Nuclear Regulatory Commission Attention: Document Control Desk One White Flint North 11555 Rockville Pike Rockville, MD 20852-2746 South Texas Project Units 1 and 2 Docket Nos. STN 50-498, STN 50-499 Amended Request for Relief from ASME Section XI Code Requirements for Reactor Pressure Vessel Flange Insert Non-Destructive Examination (TAC No. ME4764/ME4765) (Relief Request RR-ENG-3-02)
Reference:
Marco Ruvalcaba, STP Nuclear Operating Company, to NRC Document Control Desk, "Request for Relief from ASME Section XI Code Requirements for Reactor Pressure Vessel Flange Insert Non-Destructive Examination (Relief Request RR-ENG-3-02)," dated September 20, 2010 (NOC-AE-1 0002593) (ML102700173)
In accordance with the provisions of 10 CFR 50.55a(a)(3)(i), the STP Nuclear Operating Company (STPNOC) requested relief from the ASME Section XI code nondestructive examination requirements applicable to the South Texas Project reactor pressure vessel flange inserts (referenced above). As an alternative to the visual examination, the South Texas Project proposes to perform a straight beam ultrasonic examination from the top surface of each insert (36 per unit) as described in the attached relief request. This amended request incorporates additional information in response to NRC reviewer comments. Revised and new text is indicated in the margin.
There are no commitments in this correspondence.
STPNOC requests NRC review and approval of this relief request by April 1, 2011, to support implementation of the Unit 1 and Unit 2 Ten Year Inservice Inspection Plan for the third inspection interval. The requested date is flexible.
If there are any questions, please contact either Mr. Philip Walker at 361-972-8392 or me at 361-972-7904.
M arco Ruvalcaba Manager, Test and Programs Engineering PLW
Attachment:
Amended Request for Relief from ASME Section Xl Code Requirements for Reactor Pressure Vessel Flange Insert Non-Destructive Examination (Relief Request RR-ENG-3-02)
STI: 32816652
NOC-AE-1 1002633 Page 2 of 2 cc: (paper copy) (electronic copy)
Regional Administrator, Region IV A. H. Gutterman, Esq.
U. S. Nuclear Regulatory Commission Morgan, Lewis & Bockius LLP 612 East Lamar Blvd., Suite 4004 Arlington, TX 76011-4125 Mohan C. Thadani U. S. Nuclear Regulatory Commission Mohan C. Thadani Peter Nemeth Senior Project Manager Crain Caton & James, P.C.
U.S. Nuclear Regulatory Commission One White Flint North (MS 8 G14) 11555 Rockville Pike C. Mele Rockville, MD 20852 City of Austin Senior Resident Inspector E. Alarcon U. S. Nuclear Regulatory Commission K. Polio P. 0. Box 289, Mail Code: MN1 16 Richard Pena Wadsworth, TX 77483 City Public Service C. M. Canady John Ragan City of Austin C. Callaway, Esq.
Electric Utility Department J. von Suskil 721 Barton Springs Road NRG South Texas LP Austin, TX 78704 Richard A. Ratliff Alice Rogers Texas Department of State Health Services
Attachment NOC-AE-1 1002633 Page 1 of 9 SOUTH TEXAS PROJECT UNITS 1 AND 2 AMENDED REQUEST FOR RELIEF FROM ASME SECTION Xl CODE REQUIREMENTS FOR REACTOR PRESSURE VESSEL FLANGE INSERT NON-DESTRUCTIVE EXAMINATION (RELIEF REQUEST RR-ENG-3-02)
A. Components Affected (a) Component: Reactor Pressure Vessel (b)
Description:
Roto-Lok flange inserts (bushings)
The vessel insert material specification is SA-540, Class 3, Gr. B-24 (as modified by Code Case 1605). There are 36 flange inserts per unit. Figure 1 is a cut-away showing the dimensions of a typical flange bushing mounted in the reactor pressure vessel flange. Figures 2A and 2B show the flange bushing ultrasonic examination volume.
(c) Class: ASME Code Class 1 B. Applicable Code Requirement The applicable code is ASME Section Xl, 2004 Edition (no addenda).
IWB-2500, Table IWB-2500-1, Code Category B-G-1, Item Number B6.50 requires that all bushings receive a visual, VT-1 examination each inspection interval. Examination of bushings and threads in flange base material is required only when the connections are disassembled. Bushings may be inspected in place.
C. Basis for Relief from Code Requirements In accordance with the provisions of 10 CFR 50.55a(a)(3)(i), STP Nuclear Operating Company (STPNOC) requests relief from the Section Xl code requirement for a visual, VT-1 examination of reactor pressure vessel bushings and threads in flange base material. Roto-Lok flange inserts (see attached illustration) consist of conventional threads on the outside surface and three rows of lugs on the inside surface. With the Roto-Lok flange inserts in place in the reactor vessel flange, portions of the lugs are not accessible for Visual, VT-1 examination.
D. Alternative Examination:
Pursuant to 10 CFR 50.55a(a)(3)(i), STPNOC proposes to perform a straight beam ultrasonic examination of the vessel inserts from the top end of the vessel inserts as an alternative to the Code-required Visual, VT-1 examination. The proposed alternative examination is to be performed concurrently with that of the vessel flange thread volumetric examination to inspect for radial-circumferential flaws.
E. Justification for Granting Relief Performing the examination concurrent with the vessel flange thread ultrasonic examination will reduce total radiation exposure. The ultrasonic technique will examine the entire length
Attachment NOC-AE-i 1002633 Page 2 of 9 of the vessel insert and is superior to the VT-1 examination. The straight beam ultrasonic examination procedure has been demonstrated to ensure examination adequacy.
Volumetric examination in lieu of the Visual, VT-1 examination was successfully performed during the second inservice inspection interval at STP Units 1 (September 25, 2000 to September 24, 2010) and 2 (October 19, 2000 to October 18, 2010). Figures 2A and 2B depict the volume achieved by ultrasonic examination.
The initial demonstration was performed December 7, 1998, in accordance with ultrasonic technical instructions. Ultrasonic technical instructions are demonstrated at the Electric Power Research Institute (EPRI) in accordance with the requirements of ASME Section Xl, Appendix VIII, 1995 Edition with Addenda through 1996, as modified by the Performance Demonstration Initiative (PDI) Program Description.
A calibration block was prepared in accordance with Table VI-2430-1 of ASME Section Xl, Appendix VI, to examine the entire length of the vessel insert. The calibration block was fabricated from an actual spare reactor pressure vessel insert. The calibration block includes notches at different depths on both the inside and outside surfaces to ensure examination volume coverage and sensitivity were obtained. The notches are representative of flaws that would be found in-service. The demonstration confirmed that all inside and outside surface indications can be easily observed at scanning speed.
The manual, contact, pulse echo, ultrasonic method utilizes a 1-inch round 0-degree longitudinal wave transducer. The inserts are examined from the top with the beam passing through the length of the insert.
Pictures of the calibration standard are attached:
Figure 3: This displays the inner surface of the calibration block for examining a reactor bushing insert. Machined notches at 8, 14, 20, and 23 inches from the top surface of the bushing are used to demonstrate the ability to discern crack-like indications at the inner bore surface.
Figure 4: This displays the outer surface of the calibration block for examining a reactor bushing insert. Machined notches at 4, 10, and 16 inches from the top surface are used to demonstrate the ability to detect indications located in the grooved area between threads (thread root).
The proposed alternate straight beam ultrasonic examine will ensure continued structural integrity of the vessel inserts and provide a comparable or superior level of quality and safety when compared to the Code-required Visual, VT-1 examination.
F. Implementation Schedule STPNOC requests relief from ASME Section Xl nondestructive examination requirements for the reactor pressure vessel flange inserts for the duration of the third ten-year inservice inspection interval of Units 1 and 2. The third interval began September 25, 2010 (Unit 1) and October 19, 2010 (Unit 2) and ends September 24, 2020 and October 18, 2020, respectively. The Nuclear Regulatory Commission is requested to review and approve this
Attachment NOC-AE-1 1002633 Page 3 of 9 relief request by April 1, 2011, to support implementation of the Unit 1 and Unit 2 Ten Year Inservice Inspection Plan for the third interval. The requested date is flexible.
G. Precedent Relief from this examination requirement to apply the proposed alternative at the South Texas Project was previously approved by the NRC for the second 10-year inservice inspection interval for STP Units 1 (September 25, 2000 to September 24, 2010) and 2 (October 19, 2000 to October 18, 2010):
Inservice Inspection Program, Relief Request RR-ENG-2-5 (June 17, 1999) (TAC Nos. MA5462 and MA5463)
Attachment NOC-AE-1 1002633 Page 4 of 9 SOUTH TEXAS PROJECT RELIEF REQUEST RR-ENG-3-02 RESPONSE TO REQUEST FOR ADDITIONAL INFORMATION The Nuclear Regulatory Commission (NRC) staff reviewed the information provided by STP Nuclear Operating Company for South Texas Project Units 1 and 2, in its letter dated September 20, 2010, and determined that additional information is necessary to complete the review of Relief Request RR-ENG-3-02.
- 1. Please provide the start and end dates of the third 10-year inservice inspection interval for STP Units 1 and 2.
Response
This information is incorporated into Section F of amended RR-ENG-3-02.
- 2. Section E of RR-ENG-3-02 states that the "straight beam ultrasonic examination procedure has been demonstrated to ensure examination adequacy." Please provide a detailed description of this demonstration, including mockups/samples used, method(s) demonstrated, and results.
Response
This information is incorporated into Section E of amended RR-ENG-3-02.
- 3. What flaws are expected in these components? Unless addressed in response to question 2 above, please address whether the mockups used in the demonstration of the UT technique contained flaws representative of those found inservice.
Response
As addressed in response to question 2, the mockups used in demonstration of the UT technique include flaws representative of those found in service. See Figures 3 and 4.
- 4. The illustration of the Roto-lok flange insert provided in RR-ENG-3-02 is not sufficient for understanding the Code-required examination surface as well as what is going to be examined with UT in lieu of VT. Please provide additional illustrations to clarify the Code required VT and proposed UT examination.
Response
Figure 1 shows the dimensions of a flange bushing insert.
Figures 2A and 2B show the flange bushing volume to be examined ultrasonically.
- 5. How many Roto-Lok flange inserts are on each reactor vessel?
Response
There are 36 Roto-Lok flange inserts on each reactor vessel.
Attachment NOC-AE-1 1002633 Page 5 of 9 FLANGE BUSHING THREADS 16.75" REACTOR PRESSURE 23.875" VESSEL FLANGE 9.913" 12.750" FIGURE 1 FLANGE BUSHING DIMENSIONS
Attachment NOC-AE-1 1002633 EXAMINATION VOLUME Page 6 of 9 (INSIDE SURFACE)
F R N EXAMINATION VOLUME (OUTSIDE THREADS)
AF zz EXAMINATION VOLUME (OUTSIDE THREADS)
FI Id[.d[.dLl&d- m FIGURE 2A FLANGE BUSHING ULTRASONIC EXAMINATION VOLUME
Attachment NOC-AE-1 1002633 Page 7 of 9 EXAMINATION VOLUME (OUTSIDE THREADS)
EXAMINATION VOLUME (INSIDE SURFACE)
FIGURE 2B FLANGE BUSHING ULTRASONIC EXAMINATION VOLUME (TOP VIEW)
Attachment NOC-AE-1 1002633 Page 8 of 9 I
FIGURE 3 REACTOR PRESSURE VESSEL FLANGE BUSHING CALIBRATION BLOCK (INTERIOR SURFACE)
Attachment NOC-AE-1 1002633 Page 9 of 9 16-inhch