ML11273A049

Response to Request for Additional Information Regarding Relief Requests for Limited Coverage Examinations Performed in the Third 10-Year Inspection Interval

ML11273A049
Person / Time
Site:	Millstone
Issue date:	09/22/2011
From:	Price A Dominion Nuclear Connecticut
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
11-511
Download: ML11273A049 (17)

Text

Dominion Nuclear Connecticut, Inc.

5000 Dominion Boulevard, Glen Allen, Virginia 23060 JA FoominioW Web Address: www.dom.com Proprietary Information -Withhold Under 10 CFR 2.390 September 22, 2011 U. S. Nuclear Regulatory Commission Serial No.11-511 Attention: Document Control Desk NSSLIWDC RO Washington, DC 20555 Docket No.

50-336 License No.

DPR-65 DOMINION NUCLEAR CONNECTICUT, INC.

MILLSTONE POWER STATION UNIT 2 RESPONSE TO REQUEST FOR ADDITIONAL INFORMATION REGARDING RELIEF REQUESTS FOR LIMITED COVERAGE EXAMINATIONS PERFORMED IN THE THIRD 10-YEAR INSPECTION INTERVAL As part of the inservice inspection (ISI) program, Dominion Nuclear Connecticut, Inc. (DNC) submitted a letter dated March 30, 2011 requesting approval for Relief Requests RR-89-69, RR-89-70, RR-89-71, RR-89-72, RR-89-73, RR 74, RR-89-75, RR-89-76, RR-89-77, and RR-89-78 for relief for limited coverage examinations performed in the third 10-year inservice inspection interval for Millstone Power Station Unit 2 (MPS2). Relief was requested on the basis that the required examination coverage is impractical due to physical obstructions and limitations imposed by the design, geometry and materials of construction of the subject components. In a letter dated August 26, 2011, the NRC transmitted a request for additional information (RAI). It was agreed DNC would respond to the RAI by September 23, 2011. provides the DNC response to the NRC RAI addressing questions 1 through 6. Attachment 2 provides sketches for the response to question 1.

The information in Attachment 2 is proprietary to AREVA NP and is supported by an affidavit provided in Attachment 3.

Accordingly, it is requested that be withheld from public disclosure in its entirety in accordance with 10 CFR 2.390.

Because AREVA NP seeks to withhold Attachment 2 in its entirety, a nonproprietary version of the attachment has not been prepared. provides a sketch in support of the response to question 3.

If you have any questions regarding this submittal, please contact Wanda Craft at (804) 273-4687.

Sincerely, SJ. Ala Price ce resident - Nuclear Engineering

-\\c1*-1 contains information that is being withheld from public disclosure under 10 CFR 2.390. Upon separation from the attachment, this letter is decontrolled.

Serial No.11-511 Docket No. 50-336 RAI Response for RRs for Limited Coverage Examinations Page 2 of 2 Attachments:

1. Response to Request for Additional Information Regarding Relief Requests for Limited Coverage Examinations Performed in the Third 10-Year Inspection Interval

2. Scan Plan for MPS2 Spring 2008 RPV Examination (Proprietary)

3. Application for Withholding Proprietary Information from Public Disclosure

4. Coverage Calculation Sketch for MSR-2 Commitments made in this letter:

1. None cc:

U.S. Nuclear Regulatory Commission Region I 475 Allendale Road King of Prussia, PA 19406-1415 C. J. Sanders Project Manager - Millstone Power Station U.S. Nuclear Regulatory Commission One White Flint North 11555 Rockville Pike Mail Stop O-8B3 Rockville, MD 20852-2738 NRC Senior Resident Inspector (w/o attachments)

Millstone Power Station

Serial No.11-511 Docket No. 50-336 ATTACHMENT i RESPONSE TO REQUEST FOR ADDITIONAL INFORMATION REGARDING RELIEF REQUESTS FOR LIMITED COVERAGE EXAMINATIONS PERFORMED IN THE THIRD 10-YEAR INSPECTION INTERVAL DOMINION NUCLEAR CONNECTICUT, INC.

MILLSTONE POWER STATION UNIT 2

Serial No.11-511 MPS2 RAI Response for RRs for Limited Coverage Examinations, Page 1 of 8 Question 1 RR-89-69, ASME Code, Section Xl, Examination Category B-A, Items B1.21 and B1.22, Pressure Retaining Welds in Reactor Vessel

a. The licensee stated that approximately 43 to 72.5 percent of the ASME Code required volumetric coverage could be obtained on reactor pressure vessel (RPV) Lower Head Meridional Welds BHV-1, -2, -3, -4, -5, and -6 and RPV Lower Shell-to-Lower Head Weld HS-1. Schematics have been provided of the RPV lower shell and lower head area depicting limitations of the core support lugs, flow skirt, and core barrel stabilizers. However, these drawings are unclear and extremely difficult to read. Please resubmit clear schematics/sketches to better describe the limitations of the RPV circumferential and meridional head welds.

b. The ASME Code states that essentially 100 percent of the "accessible length" of the subject welds must be examined. Please state the accessible length of each of the RPV circumferential and meridional head welds, and clarify whether the volumetric coverage percentages obtained are applicable to the accessible length, as opposed to the entire length of the weld.

DNC Response

a. Attached is a final scan plan for MPS2 spring 2008 RPV examination.

(Attachment 2) This legible file should clarify the examination coverage and limitations of the welds.

b. The accessible weld length to be examined is dependent upon the size of the examination equipment and the obstruction that limits access for this equipment to scan the required examination angles across the surface to obtain the necessary coverage of the examination volume. The length of weld scanned is documented in the scan plan and examination coverage calculation sheets for each weld. The examination coverage calculations take into account the area that was able to be scanned and the volume the required examination angles effectively covered. Essentially 100% of the accessible weld length was scanned to the extent possible and the effective coverage of the examination volume was calculated based on the examination angles required to cover the defined examination volume from the required beam directions. The volumetric coverage percentages listed in relief request RR-89-69 are applicable to the entire weld length.

Serial No.11-511 MPS2 RAI Response for RRs for Limited Coverage Examinations, Page 2 of 8 Question 2 RR-89-73, ASME Code, Section Xl, Examination Category C-B, Item C2.21, Pressure Retaining Nozzle Welds in Vessels Confirm that the required surface examinations, liquid penetrant (PT) or magnetic particle (MT) were performed for the subject welds in RR-89-73, and whether these surface examinations met the full ASME Code examinations (>90 percent coverage).

Further, describe any indications that were detected and how these were resolved.

DNC Response The required Magnetic Particle (MT) surface examination was performed on the subject welds with 100% code coverage attained. No recordable indications were detected.

Question 3 RR-89-74, ASME Code, Section Xl, Examination Category C-C, Item C3.20, Integral Attachments for Vessels, Piping, Pumps, and Valves

a. The licensee stated that examinations for the Main Steam Restraint Lug MSR-2 attachment welds were limited due to restraint members within close proximity of each of the lugs. It is further stated that, to increase examination coverage, support members of the pipe rupture restraint would need to be disassembled and removed, which would require a significant effort that is considered impractical due to impact to plant equipment.

It is unclear what is meant by "impact to plant equipment" and why the removal of the subject restraint is considered an impracticality. Submit detailed information on how the removal of the subject restraint would be an "impact to plant equipment" and why not removing this restraint, to gain access to the branch piping weld and maximize volumetric coverage, will continue to provide an acceptable level of quality and safety.

b. The schematics provided are unclear and difficult to read. Please resubmit higher quality schematics/sketches to clearly describe the limitations of the MSR-2 pipe restraint lug attachment welds.

DNC Response

a. As required by Category C-C, Item C3.20, a surface examination was performed on the attachment welds of MSR-2.

Serial No.11-511 MPS2 RAI Response for RRs for Limited Coverage Examinations, Page 3 of 8 The "impact to plant equipment" refers to the potential for damage to the components of the support or other adjacent plant components from the disassembly and reassembly of the support members for the purpose of obtaining additional coverage on the subject weld. This is a large support on a 34 inch pipe. The components of the support consist of a downstream boxed steel plate ring approximately 73 inches in diameter by 8.5 inches wide that encompasses the circumference of the pipe. The ring is secured with four studs, 2 3/4 " diameter by approximately six feet long, that are bolted to a permanently welded upstream portion of the support assembly. To improve examination coverage of the subject welds would require removal of the studs to move the downstream ring away from the subject welds. To move the downstream ring would require specialized rigging due to the weight of the ring, which is estimated to be approximately 2500 pounds. Additionally, there is minimal clearance between the ring and the 34" pipe, which adds to the difficulty of moving the ring along the pipe axis for access to the subject welds.

As noted in Relief Request RR-89-74, later editions of the code now allow the surface examination to be limited to the portions that are accessible without removal of the support members. (Reference ASME Section XI, 2004 Edition, Figure IWC-2500-5).

With the examination coverage that was attained and the VT-2 visual examination performed each inspection period, it is reasonable to conclude that if significant service-induced degradation had occurred, evidence would have been detected by the examinations that were performed.

b. The attached Coverage Calculation Sketch for MSR-2 has been revised to improve the clarity. (Attachment 4)

Question 4 RR-89-76, ASME Code, Section Xl, Examination Category C-F-2, Item C5.81, Pressure Retaining Welds in Carbon or Low Alloy Steel Piping The licensee stated that for ASME Code Class 2 Pipe Branch Connection Circumferential Weld MSB-CG-16, examination was limited due to the obstruction from pipe rupture restraint support members that are within close proximity of the weld. It is further stated that, to increase the examination coverage, support members of the pipe rupture restraint would need to be disassembled and removed, which would require a significant effort that is considered impractical due to impact to plant equipment.

It is unclear what is meant by "impact to plant equipment" and why the removal of the pipe restraint is considered an impracticality. Submit detailed information on how the removal of the pipe restraint would be an "impact to plant equipment" and why not

Serial No.11-511 MPS2 RAI Response for RRs for Limited Coverage Examinations, Page 4 of 8 removing this restraint to gain access to the branch piping weld and maximize volumetric coverage, will continue to provide an acceptable level of quality and safety.

DNC Response As required by category C-F-2, Item C5.81, a surface examination was performed on Weld MSB-CG-16.

The "impact to plant equipment" refers to the potential for damage to the components of the support or other adjacent plant components from the disassembly and reassembly of the support members for the purpose of obtaining additional coverage on the subject weld. This is a large support on a 34 inch pipe. The components of the support consist of a downstream boxed steel plate ring approximately 73 inches in diameter by 8.5 inches wide that encompasses the circumference of the pipe. The ring is secured with four studs, 2 3/4" diameter by approximately six feet long, that are bolted to a permanently welded upstream portion of the support assembly. To improve examination coverage of the subject welds would require removal of the studs to allow moving the downstream ring away from the subject welds. To move the downstream ring would require specialized rigging due to the weight of the ring, which is estimated to be approximately 2500 pounds. There is minimal clearance between the ring and the 34" pipe, which adds to the difficulty of moving the ring along the pipe axis for access to the subject welds. To attain the required code examination coverage, a portion of the upstream permanently welded section would also need to be cut out and removed to provide adequate access for examination of the upstream side of the subject weld.

With the examination coverage that was attained and the VT-2 visual examination performed each inspection period, it is reasonable to conclude that if significant service-induced degradation had occurred, evidence would have been detected by the examinations that were performed.

Question 5 RR-89-77, ASME Code, Section Xl, Examination Category R-A, Item R1.20, Risk Informed Piping Examinations

a. Confirm whether the examinations listed for all ASME Code, Section Xl, Examination Category R-A welds were conducted in accordance with the performance demonstration initiative (PDI) requirements of ASME Code, Section Xl, Appendix VIII.

b. Could additional or alternative welds have been examined to augment the reduced volumetric coverage resulting from the limited examinations of the subject welds?

Serial No.11-511 MPS2 RAI Response for RRs for Limited Coverage Examinations, Page 5 of 8

c. The PDI program has defined examinations of stainless steel piping from one direction terminating at the weld centerline and from the opposite direction also terminating at the weld centerline for determining coverage in the axial direction.

The PDI developed this coverage approach to support examinations with a weld crown. For examinations over the weld crown and on to the opposite side of the weld, PDI has termed that coverage volume as a best effort. Describe the surface waviness at and on the weld crown and the percent of best-effort coverage achieved on the opposite side of the weld. Could coverage be improved using phased array techniques? Please explain in detail.

DNC Response

a. The examinations listed for the ASME Code, Section Xl, Examination Category R-A welds were conducted in accordance with the performance demonstration initiative (PDI) requirements of ASME Code, Section Xl, Appendix VIII.

b. The ten welds examined in this category were selected for specific reasons. Six of the subject welds were examined specifically to meet preservice examination code requirements for new welds due to piping or component replacements as noted in Table 1 of RR-89-77.

The remaining four welds, BSI-C-1013, BSI-C-2011, BSI-C-3012 and BSI-C-4012, are located on Safety Injection lines, upstream of an isolation check valve.

The weld upstream of the isolation check valve was chosen based on this location likely being heated by conduction heating through the valve from the downstream end, which is normally at RCS cold leg temperatures. This effect could be accentuated by any back leakage at the valve. Thus, there was a potential for stratified conditions at the valve weld. In addition, the higher weld residual stresses due to the thickness discontinuity between the pipe and valve neck were a consideration. This combination of conditions is unique to these locations, and the probability of flaw initiation and propagation at other locations would not be as limiting as the ones chosen. The slightly higher probability of detection of a flaw at another location would not outweigh the much lower probability of a flaw existing at the alternate location. Therefore, selection of an alternate location for examination would not be as effective at reducing risk as the one selected.

To perform additional or alternative weld examinations in these segments would result in an increase in radiation exposure that would not provide a commensurate increase in the level of quality and safety.

c. The waviness at and on the weld crown was not detailed on all of the examination data reports. However, the data reports reflect that a portion of the

Serial No.11-511 MPS2 RAI Response for RRs for Limited Coverage Examinations, Page 6 of 8 subject welds consists of either a weld crown or a taper from the thickness transition of the pipe to valve due to the component configuration, which precludes scanning over the subject welds. The examination of the subject welds was supplemented with either a 60 degree refracted longitudinal scan angle or a 70 degree shear scan angle, depending upon nominal thickness, to maximize the best effort coverage. It was not the practice to record this best effort coverage during examinations performed earlier in the interval.

Examinations listed below are examples of examinations performed later in the interval where the best effort coverage was recorded.

Weld BSI-C-4010A: 50% coverage of the entire Code examination volumre for the near side of the weld using the qualified examination techniques of the procedure with 18% total Code volume of the far side examination volume in accordance with the examination procedure as a "best effort" examination in the axial scan direction.

Weld BSI-C-4011: 50% coverage of the entire Code examination volume for the near side of the weld using the qualified examination techniques of the procedure with 18% total Code volume of the far side examination volume in accordance with the examination procedure as a "best effort" examination in the axial scan direction.

The subject welds have not been evaluated for Phased Array techniques. Due to the inherent limitations of a single-sided examination, it is doubtful coverage could be improved since a similar limitation would exist with phased array techniques.

Question 6 RR-89-78, ASME Code Section Xl, Examination Category B-P, Item B15.11, Reactor Vessel, Pressure Retaining Boundary The following questions pertain to the third 10-year ISI interval at MPS2:

a. Provide the date(s) of the previous examinations of the RPV flange seal leak-off piping visual inspections and whether any indications of leakage were detected.

The following question pertains to the first and second 10-year ISI interval at MPS2:

b. What was the ASME Code of Record for the first and second interval at MPS2?

Was the hydrostatic test of the RPV flange seal leak-off line required during the first and second 10-year interval at MPS2? If so, please explain how the test was performed during the first and second interval and if the test was not

Serial No.11-511 MPS2 RAI Response for RRs for Limited Coverage Examinations, Page 7 of 8 performed, please explain what action has been taken and/or what action will be taken.

DNC Response

a. The accessible portions of the RPV flange seal leak-off piping have been VT-2 visually examined during the RCS Class 1 system leakage test performed at the end of each refueling outage during Mode 3. The RCS system was at normal operating pressure and temperature and the RPV flange seal leak-off piping was in its normally unpressurized state.

During each refueling outage since fall 2003 (2R15) examination of the normally inaccessible portion of this line has been performed in conjunction with the examination of the areas within the lower portion of the reactor vessel cubical that are normally inaccessible during Mode 3. The RCS was cooled down and depressurized during entry into this confined space cubicle.

A direct detailed visual examination for evidence of leakage from the portion of the line containing Alloy 600 material has been performed near the beginning of each outage of the interval since spring 2005 (2R16) with the RCS cooled down and depressurized.

Outage/Date 2R14 03/30/2002 Examination during Class 1 system leakage test (Mode 3)

No indication of leakage 2R15 10/16/2003 Examination during entry into lower reactor vessel cubical No indication of 11/24/2003 Examination during Class 1 system leakage test (Mode 3) leakage 2R16 04/12/2005 Detailed examination at beginning of refueling outage No indication of 04/15/2005 Examination during entry into lower reactor vessel cubical leakage 05/16/2005 Examination during Class 1 system leakage test (Mode 3) 2R17 10/09/2006 Detailed examination at beginning of refueling outage No indication of 10/09/2006 Examination during entry into lower reactor vessel cubical leakage 11/16/2009 Examination during Class 1 system leakage test (Mode 3) 2R18 04/08/2008 Detailed examination at beginning of refueling outage No indication of 04/10/2008 Examination during entry into lower reactor vessel cubical leakage L 05/13/2008 Examination during Class 1 system leakage test (Mode 3) 2R19 10/10/2009 Detailed examination at beginning of refueling outage No indication of 10/15/2009 Examination during entry into lower reactor vessel cubical leakage 11/14/2009 Examination during Class 1 system leakage test (Mode 3)

Serial No.11-511 MPS2 RAI Response for RRs for Limited Coverage Examinations, Page 8 of 8

b. The ASME Code of Record for the 1st inspection interval was 1971 Edition through the Summer 1973 Addenda. The ASME Code of Record for the 2 nd interval was the 1980 Edition through the Winter 1981 Addenda. During the 1st and 2 nd interval, the subject piping was examined in its normally unpressurized state. The requirements for pressurization of this normally isolated piping were not recognized at that time. This was identified near the end of the third inspection interval during preparation of the fourth inspection interval submittal.

As a result, the piping was not pressurized to the code required pressure during the first and second interval tests.

Note that a similar request has been recently approved (RR-04-08, approved January 18, 2011, ADAMS Accession No.ML103640257) for the fourth 10-year inspection interval.

Serial No.11-511 Docket No. 50-336 ATTACHMENT 3 APPLICATION FOR WITHHOLDING PROPRIETARY INFORMATION FROM PUBLIC DISCLOSURE DOMINION NUCLEAR CONNECTICUT, INC.

MILLSTONE POWER STATION UNIT 2

AFFIDAVIT COMMONWEALTH OF VIRGINIA

)

) ss.

CITY OF LYNCHBURG

)

1.

My name is Gayle F. Elliott. I am Manager, Product Licensing, for AREVA NP Inc. and as such I am authorized to execute this Affidavit.

2.

I am familiar with the criteria applied by AREVA NP to determine whether certain AREVA NP information is proprietary. I am familiar with the policies established by AREVA NP to ensure the proper application of these criteria.

3.

I am familiar with the AREVA NP information contained in Drawings 8022552D, Revision 003, Sheets 1 through 17, entitled "Millstone Unit 2, 10 Year Reactor Vessel ISl - 2008," and referred to herein as "Documents." Information contained in these Documents has been classified by AREVA NP as proprietary in accordance with the policies established by AREVA NP for the control and protection of proprietary and confidential information.

4.

These Documents contain information of a proprietary and confidential nature and is of the type customarily held in confidence by AREVA NP and not made available to the public. Based on my experience, I am aware that other companies regard information of the kind contained in these Documents as proprietary and confidential.

5.

These Documents have been made available to the U.S. Nuclear Regulatory Commission in confidence with the request that the information contained in these Documents be withheld from public disclosure. The request for withholding of proprietary information is made in accordance with 10 CFR 2.390. The information for which withholding from disclosure

is requested qualifies under 10 CFR 2.390(a)(4) "Trade secrets and commercial or financial information."

6.

The following criteria are customarily applied by AREVA NP to determine whether information should be classified as proprietary:

(a)

The information reveals details of AREVA NP's research and development plans and programs or their results.

(b)

Use of the information by a competitor would permit the competitor to significantly reduce its expenditures, in time or resources, to design, produce, or market a similar product or service.

(c)

The information includes test data or analytical techniques concerning a process, methodology, or component, the application of which results in a competitive advantage for AREVA NP.

(d)

The information reveals certain distinguishing aspects of a process, methodology, or component, the exclusive use of which provides a competitive advantage for AREVA NP in product optimization or marketability.

(e)

The information is vital to a competitive advantage held by AREVA NP, would be helpful to competitors to AREVA NP, and would likely cause substantial harm to the competitive position of AREVA NP.

The information in these Documents is considered proprietary for the reasons set forth in paragraphs 6(b) and 6(c) above.

7.

In accordance with AREVA NP's policies governing the protection and control of information, proprietary information contained in these Documents has been made available, on a limited basis, to others outside AREVA NP only as required and under suitable agreement providing for nondisclosure and limited use of the information.

8.

AREVA NP policy requires that proprietary information be kept in a secured file or area and distributed on a need-to-know basis.

9.

The foregoing statements are true and correct to the best of my knowledge, information, and belief.

SUBSCRIBED before me this

_q__

day of

,m jnLJ%.' -

'IY 2011.

Sherry L. McFaden NOTARY PUBLIC, COMMONWEALTH OF VIRGINIA MY COMMISSION EXPIRES: 10/31/14 Reg. # 7079129 SHERRY L. MCFADEN Notar6 Public Commonwealth of Virginia 7079129 My Commission Expires Oct 31, 2014

Serial No.11-511 Docket No. 50-336 ATTACHMENT 4 COVERAGE CALCULATION SKETCH FOR MSR-2 DOMINION NUCLEAR CONNECTICUT, INC.

MILLSTONE POWER STATION UNIT 2

GENERIC SKETCH SHEET Plant Millstone System Main Steam Unit 2 Page I of I Zone 2-17 Exam Package 214-03-004 Component ID MSR - 2 Restraint Lugs Coverage Calculation Sketch for MSR-2 14.0" 13.0" 0.50" Pipe Area # 4 I

8.25" Everything to the right side of this 1

line was not examined due to the obstruction from the restraint members.

2.00" 1.00"T 0.50"

- 1.00",

Area # 3 0.*50_*, x Area# 5