ML080110695

Response to Request for Additional Information Regarding Stretch Power Uprate License Amendment Request, Response to Questions CSGB-07-0010 and CSGB-07-0011

ML080110695
Person / Time
Site:	Millstone
Issue date:	01/11/2008
From:	Gerald Bichof Dominion, Dominion Nuclear Connecticut
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
07-0834B, CSGB-07-0010, CSGB-07-0011
Download: ML080110695 (11)

Text

Dominion Nuclear Connecticut, Inc.

~()O() Dominion Boulevard, Glen Allen, Virginia 2:,060 Weh Address: www.dom.com January 11, 2008 U. S. Nuclear Regulatory Commission Serial No.: 07-0834B Attention: Document Control Desk NLOS/MAE: RO One White Flint North Docket No.: 50-423 11555 Rockville Pike License No.: NPF-49 Rockville, MD 20852-2378 DOMINION NUCLEAR CONNECTICUT, INC.

MILLSTONE POWER STATION UNIT 3 RESPONSE TO REQUEST FOR ADDITIONAL INFORMATION REGARDING STRETCH POWER UPRATE LICENSE AMENDMENT REQUEST RESPONSE TO QUESTIONS CSGB-07-0010 AND CSGB-07-0011 Dominion Nuclear Connecticut, Inc. (DNC) submitted a stretch power uprate license amendment request (LAR) for Millstone Power Station Unit 3 (MPS3) in letters dated July 13, 2007 (Serial Nos. 07-0450 and 07-0450A), and supplemented the submittal by letters dated September 12, 2007 (Serial No. 07-04508) and December 13, 2007 (Serial No. 07-0450C).

The NRC staff forwarded requests for additional information (RAls) in October 29, 2007 and November 27, 2007 letters. DNC responded to the RAls in letters dated November 19, 2007 (Serial No. 07-0751) and December 17,2007 (Serial No. 07-0499). The NRC staff forwarded an additional RAI in a December 14, 2007 letter. The response to questions CSGB-07-0010 and CSGB-07 -0011 of this RAI is provided in the attachment to this letter.

The information provided by this letter does not affect the conclusions of the significant hazards consideration discussion in the December 13, 2007 DNC letter (Serial No. 07-0450C).

Should you have any questions in regard to this submittal, please contact Ms. Margaret Earle at 804-273-2768.

Sincerely,

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Vice President Nuclear Engineering COMMONWEALTH OF VIRGINIA COUNTY OF HENRICO The foregoing document was acknowledged before me, in and for the County and Commonwealth aforesaid, today by Gerald T. Bischof, who is Vice President Nuclear Engineering of Dominion Nuclear Connecticut, Inc. He has affirmed before me that he is duly authorized to execute and file the foregoing document in behalf of that Company, and that the statements in the document are true to the best of his knowledge and belief.

Ii 77-1 Acknowledged before me this LL-..:.iday of ,2008.

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Serial No. 07-08348 Docket No. 50-423 SPU Ques. CSGB-07-0010 and CSGB-07-0011 Page 2 Commitments made in this letter: None Attachment cc: U.S. Nuclear Regulatory Commission Region I Regional Administrator 475 Allendale Road King of Prussia, PA 19406-1415 Mr. J. G. Lamb U.S. Nuclear Regulatory Commission One White Flint North 11555 Rockville Pike Mail Stop 0-8B1A Rockville, MD 20852-2738 Ms. C. J. Sanders Project Manager U.S. Nuclear Regulatory Commission One White Flint North 11555 Rockville Pike Mail Stop 0-883 Rockville, MD 20852-2738 Mr. S. W. Shaffer NRC Senior Resident Inspector Millstone Power Station Director Bureau of Air Management Monitoring and Radiation Division Department of Environmental Protection 79 Elm Street Hartford, CT 06106-5127

ATTACHMENT LICENSE AMENDMENT REQUEST STRETCH POWER UPRATE LICENSE AMENDMENT REQUEST RESPONSE TO REQUEST FOR ADDITIONAL INFORMATION RESPONSE TO QUESTIONS CSGB-07-0010 AND CSGB-07-0011 MILLSTONE POWER STATION UNIT 3 DOMINION NUCLEAR CONNECTICUT, INC.

Serial No. 07-08348 Docket No. 50-423 Attachment, Page 1 of 8 Steam Generator Integrity & Chemical Engineering Branch CSGB-07-0010 (2.1.8-1)

The flow accelerated corrosion (FAC) program at MPS incorporates years of field data including wear rates and actual thickness measurements under current operating conditions. Under SPU conditions, however, MPS does not have data to inform the CHECWORKS model. Since the accuracy of the CHECWORKS program is dependent on field data, there is a potential that the changes in process variables (temperature, velocity, moisture content) resulting from SPU will lead to an unanticipated wear rate and therefore under-prediction of component thickness loss. How does the MPS3 FAC program account for this potential effect? How is the license renewal aging management program for FAC impacted by this potential effect? Identify the components that are expected to experience the greatest increase in wear as a result of power uprate and discuss the relative reduction in service life for those components. In addition, discuss any changes made to the MPS3 FAC program (i.e., criteria used for selecting components for inspection following the power uprate, criteria for repair and replacement, increased inspection scope, etc.) due to power uprate conditions.

ONC Response The FAC Program at Millstone Power Station Unit 3 (MPS3) continually incorporates field data into CHECWORKS and monitors the actual wear rates and thicknesses against the predicted wear. This activity ensures CHECWORKS predictions are checked constantly against field data. The CHECWORKS model has been updated based on the SPU heat balance to reflect the SPU thermodynamic and flow conditions.

A comparison of pre-SPU and post-SPU predictions has been made to evaluate the impact of the SPU on FAC wear rates. The following table shows the percent change in predicted wear rate for a series of selected components. The results range from a slight decrease to an increase of as high as approximately 32 percent.

However, the percent change in wear rate is a relative consideration. For example, a component on a line could exhibit an increase in wear rate of approximately 32 percent due to the SPU. However, if the absolute wear rate was small or if the component had a high margin, the impact of the 30 percent change is minimal.

To correctly interpret the CHECWORKS results to determine the actual impact of the SPU, the following factors were considered in conjunction with the percent

Serial No. 07-0834B Docket No. 50-423 Attachment, Page 2 of 8 change in wear rate:

• Absolute current wear rate.

• Actual measured component thickness.

• Design margin (difference between the measured component thickness and minimum allowable thickness)

While the table presents data for individual components, entire lines were assessed. When selecting inspection locations for the next outage, DNC will consider lines with the highest vulnerability based on the above discussion.

Additional inspection coverage will be considered for lines that indicate a significant change in predicted wear rates. The license renewal aging management program is not impacted by SPU other than increased monitoring to the end of the component life.

The power uprate parameters have already been built into the CHECWORKS model based on the expected power uprate Heat Balance. The post performance test at 100% power will allow adjustments to the theoretical heat balance values. The CHECWORKS SFA (Steam/Feedwater Application) database will be updated at the implementation of the modification, and used for future monitoring.

The additional coverage will be implemented based on the CHECWORKS trending and MFAC (Millstone Flow Accelerated Corrosion) wear calculations for non-CHECWORK modeled lines and components in scope to the FAC program.

Since these lines and components have already been reviewed to the power uprate theoretical heat balance model, impacted coverage components are already identified for wall thickness examinations. Future trending will be addressed as part of the overall program reviews required in accordance with EPRI NSAC 202L (Recommendations for An Effective Flow-Accelerated Corrosion Program) guidelines.

The FAG program has reviewed the effect of the proposed SPU on the FAG analysis for the plant and has concluded that changes in the plant operating conditions on the FAC analysis have been reasonably addressed. It has also been demonstrated that the updated analyses will accurately predict the loss of material by FAC and ensure timely repair or replacement of degraded components following implementation of the SPU.

For a comparison of predicted and measured wall thickness at current plant conditions, and wear rate comparison pre and post power uprate See Table 2.1.8-2 of the licensing report (Attachment 6 of MPS3 SPU licensing amendment request dated July 13, 2007).

Serial No. 07-08348 Docket No. 50-423 Attachment, Page 3 of 8 Comparison of Predicted and Measured Wall Thickness at Current Plant Conditions (100% Power) .__ .._ . -

Fluid Parameters and Wear Rate Comparison-Pre and Post Power Uprate Wear Rate CHECWORKS Temperature (deg F) Velocity (ftlsec) Quality Impact ef Power Uprate on Analysis Ram Component Name Component Geometry Wear Rate (mils/year)

• Predicted Wear Rate Notes Definition Name Type (% Change]

Current SPU Current SPU Current SPU Current SPU BLOWDOWNTO 053-006 45 544.3 544 1.229 1.228 0 0 0.004 0.004 0.0 Line is constructed of CONTROL VALVE.

Elbow chrome-moly 050-008 US Pipe 544.3 544 1.229 1.228 0 0 0.001 0.001 0.0 BLOWDOWN 050-028 Pipe 319.8 319.8 20.424 20.424 0.282 0.281 0.006 0.006 0.0 All components with the FROM CONTROL VALVE TO exception of the nozzle are BLOWDOWN chrome-moly TNK 057-018 Nozzle 319.8 319.8 8.643 8.643 0.282 0.281 1.053 1.053 0.0 BLOWDOWN 058-002 US Pipe 307.4 307.4 1.212 1.213 0 0 0.960 0.959 -0.1 TANK DRAIN TO CONTROL VALVE 058-027 90 307.4 307.4 2.212 1.213 0 0 1.315 1.315 0.0 Elbow BLOWDOWN 058-048 Nozzle 215.8 215.6 16.363 16.253 0.097 0.097 0.766 0.767 0.1 TANK DRAIN FROM CONTROL VALVE TO CONDENSER 2ND POINT 033-002 90 360.2 365.5 8.107 8.829 0 0 4.507 4.708 4.5 HEATER TO CONDENSATE Elbow HEATER 034-019 Pipe 360.2 365.5 8.107 8.829 0 0 3.898 4.071 4.4 CONDENSATE 035-007 90 361.1 366.5 8.837 9.61 0 0 6.861 7.149 4.2 HEADER FROM 2ND POINT Elbow HEATER TO FEEDWATER PUMP SUCTION 035-024 Pipe 361.1 366.5 8.837 9.61 0 0 4.080 4.251 4.2 CONDENSATE- 031-004 90 321.5 326.6 8.157 8.878 0 0 4.081 4.021 -1.5 3RD POINT HEATER TO 2N D Elbow POINT HEATER 031-029 US Pipe 321.5 326.6 7.909 8.609 0 0 3.462 3.411 -1.5 CONDENSATE- 029-003 90 284.2 288.1 7.718 8.368 0 0 5.002 5.224 4.4 4TH POINT HEATER TO 3RD Elbow POINT HEATER UPSTREAM OF HEATER DRAIN LINE TEE 030-002 DS Pipe 284.2 288.1 7.718 8.368 0 0 3.650 3.812 4.4

• + Shows an increase in wear rate

- Shows a decrease in wear rate

Serial No. 07-08348 Docket No. 50-423 Attachment, Page 4 of 8

_..*__ .~--_.~------~

Comparison of Predicted and Measured Wall Thickness at Current Plant Conditions (100% Power Fluid Parameters and Wear Rate Comparison-Pre and Post Power Unrate Wear Rate CHECWORKS Component Temperature (deg F) Velocity (ft/sec) Quality Impact of Power Uprate on Notes Analysis Run Component Geometry Wear Rate (mils/year)

• Predicted Wear Rate Definition Name Name Type (% Change)

Current SPU Current SPU Current SPU Current SPU CONDENSATE- 029-009 90 Elbow 277.2 281.5 8.041 8.746 0 0 3.823 4.024 5.3 4TH POINT HEATER TO )RD POINT HEATER DOWNSTREAM OF HEATER DRAIN LINE TEE 03-011DS Pipe 277.2 281.5 7.797 8.48 0 0 3.243 3.414 5.3 CONDENSATE - 026-004 90 Elbow 219.6 222.9 7.841 8.495 0 0 4.831 5.100 5.6 5TH POINT HEATER TO 4TH POINT HEATER 028-017 DS Pipe 219.6 222.9 7.481 8.106 0 0 3.169 3.346 5.6 CROSSUNDER 077-026 90 Elbow 375.9 382 20.955 21.66 0.866 0.868 9.609 9.730 1.3 077-041 US Pipe 375.9 382 20.794 21.503 0.866 0.868 4.246 4.298 1.2 EXTRACTION - 005-026 90 Elbow 369.2 375.6 38.217 39.745 0.869 0.87 6.353 6.591 3.7 2ND POINT (FROM MAlNSTEAM&

REHEAT TO END POINT HEATERS) 005-051 US Pipe 369.2 375.6 38.217 39.745 0.869 0.87 4.313 4.474 3.7 EXTRACTION 5'" 014-020 US Pipe 228.4 232.6 1.311 2.017 0.956 0.951 3.891 4.225 8.6 POINT (FROM LOW PRESSURE TURBINES TO 5TH POINT HEATERS) 014-023 45 Elbow 228.4 232.6 0.072 0.105 0.956 0.951 2.788 3.668 31.6 EXTRACTION - 109-004 DS Pipe 160.4 163.7 0.029 0.036 0.925 0.923 2.891 3.369 16.5 6TH POINT (FROM LOW PRESSURE TURBINES TO 6TH POINT HEATERS) 109-008 45 Elbow 160.4 163.7 0.031 0.038 0.925 0.923 4.004 4.668 16.6 FEEDWATER 037-021 90 Elbow 363 368.4 17 18.49 0 0 8.745 9.085 3.9 PUMP TO FIRST POINT FEEDWATER HEATERS 037-009 US Pipe 363 368.4 15.694 17.069 0 0 7.192 7.472 3.9

• + Shows an increase in wear rate

- Shows a decrease in wear rate

Serial No. 07-08348 Docket No. 50-423 Attachment, Page 5 of 8 Comparison of Predicted and Measured Wall Thickness at Current Plant Conditions (100% Power)

Fluid Parameters and Wear Rate Comparison-Pre and Post Power Uprate Wear Rate Analysis Run CHECWORKS Component Component Geometry Temperature (deg F) Velocity (ftlsec) Quality Wear Rate (mils/year)

• Impact of Power Uprate on Predicted Wear Rate Notes Definition Name Name Type (% Chanze)

Current SPU Current SPU Current SPU Current SPU FEEDWATER 041-004 90 Elbow 436.4 442.7 12.069 13.15 0 0 8.606 9.664 12.3 FROMHP FEEDWATER HEATER TO STEAM GENERATOR 039-048 US Pipe 436.4 442.7 11.162 12.162 0 0 6.944 7.799 12.3 HEATER DRAINS 015-033 DS Pipe 373.4 380.3 22.607 24.671 0 0 3.685 3.746 1.7 HEADER UPSTREAM OF CONTROL VALVE 015-044 90 Elbow 3734 380.3 8.657 9.447 0 0 3.388 3.444 1.7 HEATER DRAlNS 015-022 Pipe 364.7 370.6 29.839 31.605 0.011 0.012 4.813 5.122 6.4 HEADER DOWNSTREAM OF CONTROL VALVE 015-062 90 Elbow 364.8 370.7 9.803 10.863 0.011 0.012 7.244 7.707 6.4 2ND POINT 017-026 Pipe 328.5 334.5 15.074 16.45 0 0 3.279 3.196 -2.5 HEATER DRAlN T03RDPOINT HEATER UPSTREAM OF CONTROL VALVE 018-002 90 Elbow 328.5 334.5 6.668 7.276 0 0 3.219 3.218 0.0 2ND POINT 016-026 90 Elbow 321.8 327.2 7.586 8.378 0.008 0.009 0.032 0.033 3.1 HEATERDRAlN TO 3RD POINT HEATER Entire line is constructed of DOWNSTREAM chrome-moly OF CONTROL VALVE 3RDPOINT 019-030 US Pipe 286.7 292.1 17.276 18.899 0 0 4.100 4.375 6.7 HEATER DRAlN TO 4TH POINT HEATER UPSTREAM OF CONTROL VALVE 020-003 90 Elbow 286.7 292.1 7.518 8.225 0 0 4.086 4.360 6.7

• + Shows an increase in wear rate

- Shows a decrease in wear rate

Serial No. 07-08348 Docket No. 50-423 Attachment, Page 6 of 8 Comparison of'Predicted and Measured Wall Thickness at Current Plant Conditions (100% Power)

Fluid Parameters and Wear Rate Comparison-Pre and Post Power Uprate Wear Rate Analysis Run CHECWORKS Component Component Geometry Temperature (deg F) Velocity (ftlsec) Quality Wear Rate (mils/year)

• Impact of Power Uprate on PredictedWear Rate Notes Definition Name Name Type ('Yo Chense)

Current SPU Current SPU Current SPU Current SPU 3RDPOINT 019-036 90 Elbow 286.7 292.1 4.867 5.324 0 0 3.065 3.360 9.6 HEATER DRAIN TO 4TH POINT HEATER DOWNSTREAM OF CONTROL VALVE 020-018 OS Pipe 286.7 292.1 4.795 5.246 0 0 2.615 2.867 9.6 5TH POINT 514-013 Pipe 169.4 173.8 10.6 11.591 0 0 3.646 3.927 7.7 HEATER DRAIN TO CONDENSER UPSTREAM OF CONTROL VALVE 5TH POINT 514-017 US Pipe 169.4 173.8 5.177 5.661 0 0 0.016 0.018 12.5 Entire line is constructed of HEATER DRAIN TO CONDENSER chrome-moly DOWNSTREAM OF CONTROL VALVE 6TH POINT 516-017 90 Elbow 155.2 158.4 3.105 3.4 0 0 6.480 7.118 9.8 HEATER DRAIN TO CONDENSER 516-015 OS Pipe 155.2 158.4 1.97 2.157 0 0 2.868 3.150 9.8 4TH POINT 021-002 90 Elbow 260.8 266.3 3.285 3.598 0 0 3.436 3.782 10.1 HEATER DRAIN TO HEATER PUMP 021-027 US Pipe 260.8 266.3 3.285 3.598 0 0 2.321 2.556 10.1 HEATER DRAIN 022-051 Pipe 261.5 267 5.412 5.928 0 0 3.212 3.536 10.1 Most of this line has been PUMP HEATER DRAIN LINE TO replaced with chrome-moly CONDENSATE MOISTURE 070-011 90 Elbow 369 375.5 7.01 7.53 0 0 1.023 1.065 4.1 SEPARATOR DRAIN PUMP SUCTION/

DISCHARGE 072-012 OS Pipe 368 374.4 3.024 3.248 0 0 0.253 0.268 5.9 MOISTURE 074-093 90 Elbow 368 374.4 2.659 2.856 0 0 2.354 2.485 5.6 SEPARATOR REHEATER TO MSRDRAlN TANK 074-094 Pipe 368 374.4 2.659 2.856 0 0 1.590 1.679 5.6

• + Shows an increase in wear rate

- Shows a decrease in wear rate

Serial No. 07-08348 Docket No. 50-423 Attachment, Page 7 of 8 Comparison of Predicted and Measured Wall Thickness at Current Plant Conditions (100% Power)

Fluid Parameters and Wear Rate Comparison-Pre and Post Power Uprate Wear Rate Analysis Run CHECWORKS Component Component Geometry Temperature (deg F) Velocity (ft/sec) Quality Wear Rate (mils/year)

• Impact of Power Uprate on Predicted Wear Rate Notes Definition Name Name Type /'Yo Chanae)

Current SPU Current SPU Current SPU Current SPU MOISTURE 064-002 45 Elbow 528.4 527.6 1.93 2.019 0 0 8.513 8.824 3.7 SEPARATOR REHEATER DRAIN TO REHEATER DRAINS TANK 065-020 DS Pipe 528.4 527.6 1.93 2.019 0 0 6.449 6.685 3.7 DRAINS FROM 067-008 DS Pipe 528.2 527.4 8.273 8.652 0.001 0.001 7.291 7.454 2.2 REHEATER DRAIN TANKS UPSTREAM OF CONTROL VALVE 068-019 90 Elbow 528.5 527.7 3.281 3.433 0 0 4.936 5.117 3.7 DRAINS FROM 067-016 DS Pipe 441 448. 11.98 11.362 0.13 0.12 2.327 2.594 11.5 REHEATER DRAIN TANKS 2 DOWNSTREAM OF CONTROL VALVE TO 1ST POINT FEEDWATER HEATERS 067-060 90 Elbow 440.1 447.3 13.54 12.811 0.132 0.121 3.765 4.219 12.1 5

• + Shows an increase in wear rate

- Shows a decrease in wear rate Note: This Table's Current and SPU flow velocities are liquid film velocities (or the wet steam velocities in the liquid layers.

Serial No. 07-08348 Docket No. 50-423 Attachment, Page 8 of 8 CSGB-07-0011 (2.1.8-2)

Increased secondary side flow rates will result in increased particulate matter in the steam generators (SG). CHECWORKS is unable to account for this material when analyzing FAC for the SG blowdown system. Are inspections of the SG blowdown system triggered solely by CHECWORKS, or is this system subject to inspections in a similar manner to "non-CHECWORKS modeled" systems as described in Section 2.1.8 of the SPU Licensing Report? If the SG blowdown system is treated as a "CHECWORKS modeled" system, describe why the inability of CHECWORKS to model increased particulate matter is acceptable.

ONC Response The MPS3 FAC program also relies on the wall thickness examinations of the SG blowdown system.

Even though almost all of the blowdown piping at MPS3 is constructed of Cr-Mo material, operating experience at Millstone Power Station Unit 2 (MPS2), has shown only slight improvement on the in-service life from Cr-Mo material where particulate matter and not flow accelerated corrosion is the primary wear mechanism. This mechanism is most prevalent at and downstream of the MPS2 blowdown system throttle valves, and the header(s) to the blowdown tank, including the tank's stainless steel elbow(s) and inlet nozzles which have significant wear and are monitored and trended by ultrasonic testing (UT) examination.

MPS3, to date, has not seen the same particulate problem; however, the component line information, including valves are built into the CHECWORKs program to allow for the very same trending that has been established for MPS2.

The component structural calculations (or wear calculations) that provide component remaining life, which are based on UT exams (Le., field data) and not the GHEGWORKS model, are also maintained in the Millstone FAG Application for trending purposes. Millstone looks at both the CHECWORKS model trending and Millstone FAC Steam Feedwater Application (SFA) component level wear calculations, which are viewed separately for all modeled systems. Any discrepancy where the Millstone FAC SFA components remaining life varies from the CHECWORKS model is resolved. If the model is not able to predict component life accurately as with the case of particulate impingement and cavitation, the wear calculation trending based on actual field data is used to direct future examination and or replacement of the component, as needed.

Note: For all non-modeled systems, the trending based on actual field data is retained in the Millstone FAG SFA application, while the supporting UT data is retained in the CHECWORKS application.