ML051590167

Vermont Yankee Nuclear Power Station, Request for Additional Information, Regarding Proposed License Amendment Extended Power Uprate

ML051590167
Person / Time
Site:	Vermont Yankee
Issue date:	07/27/2005
From:	Richard Ennis NRC/NRR/DLPM/LPD1
To:	Kansler M Entergy Nuclear Operations
Ennis R, NRR/DLPM, 415-1420
Shared Package
ML052020114	List: ML051590167
References
TAC MC0761
Download: ML051590167 (48)

Text

July 27, 2005 Mr. Michael Kansler President Entergy Nuclear Operations, Inc.

440 Hamilton Avenue White Plains, NY 10601

SUBJECT:

REQUEST FOR ADDITIONAL INFORMATION - EXTENDED POWER UPRATE, VERMONT YANKEE NUCLEAR POWER STATION (TAC NO. MC0761)

Dear Mr. Kansler:

By letter dated September 10, 2003, as supplemented on October 1, and October 28 (2 letters),

2003, January 31 (2 letters), March 4, May 19, July 2, July 27, July 30, August 12, August 25, September 14, September 15, September 23, September 30 (2 letters), October 5, October 7 (2 letters), December 8, and December 9, 2004, and February 24, March 10, March 24, March 31, April 5, April 22, and June 2, 2005, Entergy Nuclear Vermont Yankee, LLC and Entergy Nuclear Operations, Inc., submitted a proposed license amendment to the Nuclear Regulatory Commission (NRC) for the Vermont Yankee Nuclear Power Station (VYNPS). The proposed amendment, Technical Specification Proposed Change No. 263, Extended Power Uprate would allow an increase in the maximum authorized power level for VYNPS from 1593 megawatts thermal (MWT) to 1912 MWT.

The NRC staff is reviewing your submittal and has determined that additional information is required to complete the review. The specific information requested is addressed in the enclosed request for additional information (RAI). The NRC staff has determined that the RAI contains proprietary information pursuant to Section 2.390 of Title 10 of the Code of Federal Regulations. As such, we have enclosed non-proprietary and proprietary versions of the RAI (Enclosures 1 and 2 respectively).

M. Kansler We request that the additional information be provided by August 1, 2005. The response timeframe was discussed with Mr. Craig Nichols of your staff on July 19, 2005. If circumstances result in the need to revise your response date, or if you have any questions, please contact me at (301) 415-1420.

Sincerely,

/RA/

Richard B. Ennis, Senior Project Manager, Section 2 Project Directorate I Division of Licensing Project Management Office of Nuclear Reactor Regulation Docket No. 50-271

Enclosures:

As stated cc w/Enclosure 1 only: See next page

M. Kansler We request that the additional information be provided by August 1, 2005. The response timeframe was discussed with Mr. Craig Nichols of your staff on July 19, 2005. If circumstances result in the need to revise your response date, or if you have any questions, please contact me at (301) 415-1420.

Sincerely,

/RA/

Richard B. Ennis, Senior Project Manager, Section 2 Project Directorate I Division of Licensing Project Management Office of Nuclear Reactor Regulation Docket No. 50-271

Enclosures:

As stated cc w/Enclosure 1 only: See next page DISTRIBUTION (w/ Enclosures 1 and 2):

PUBLIC (w/ Encl 1 only) TChan, EMCB-B JCai, IROB-B MHart, SPSB-C PDI-2 Reading RDavis, EMCB-B JBongarra, IROB-B FAkstulewicz, SRXB-A DRoberts LLund, EMCB-C AKugler, RLEP-C MRazzaque, SRXB-A REnnis KParczewski, EMCB-C SImboden, RLEP-C LWard, SRXB-A JStang RKaras, EMEB-A SJones, SPLB-A ZAbdullahi, SRXB-A CRaynor TScarbrough, EMEB-A JTatum, SPLB-A GThomas, SRXB-A CAnderson, RGN I PSekerak, EMEB-A DReddy, SPLB-A THuang, SRXB-A AHowe, EEIB-A KManoly, EMEB-B SWeerakkody, SPLB-B BPoole, OGC HGarg, EEIB-A CWu, EMEB-B RGallucci, SPLB-B VBucci, OIG RJenkins, EEIB-B DThatcher, IPSB-A MRubin, SPSB-A RCaruso, ACRS NTrehan, EEIB-B RPettis, IPSB-A MStutzke, SPSB-A AWang APal, EEIB-B SKlementowicz, IPSB-B RDennig, SPSB-C MMitchell, EMCB-A RPedersen, IPSB-B RLobel, SPSB-C BElliot, EMCB-A DTrimble, IROB-B HWalker, SPSB-C Accession Nos.

Package: ML052020114 Letter and Enclosure 1 (publicly available): ML051590167 (non-publicly available): ML052020107 OFFICE PDI-2/PM PDI-2/LA OGC PDI-2/SC NAME REnnis CRaynor BPoole DRoberts DATE 7/26/05 7/21/05 7/22/05 7/26/05 OFFICIAL RECORD COPY

Vermont Yankee Nuclear Power Station cc:

Regional Administrator, Region I Ms. Carla A. White, RRPT, CHP U. S. Nuclear Regulatory Commission Radiological Health 475 Allendale Road Vermont Department of Health King of Prussia, PA 19406-1415 P.O. Box 70, Drawer #43 108 Cherry Street Mr. David R. Lewis Burlington, VT 05402-0070 Pillsbury, Winthrop, Shaw, Pittman, LLP 2300 N Street, N.W. Mr. James M. DeVincentis Washington, DC 20037-1128 Manager, Licensing Vermont Yankee Nuclear Power Station Ms. Christine S. Salembier, Commissioner P.O. Box 0500 Vermont Department of Public Service 185 Old Ferry Road 112 State Street Brattleboro, VT 05302-0500 Montpelier, VT 05620-2601 Resident Inspector Mr. Michael H. Dworkin, Chairman Vermont Yankee Nuclear Power Station Public Service Board U. S. Nuclear Regulatory Commission State of Vermont P.O. Box 176 112 State Street Vernon, VT 05354 Montpelier, VT 05620-2701 Director, Massachusetts Emergency Chairman, Board of Selectmen Management Agency Town of Vernon ATTN: James Muckerheide P.O. Box 116 400 Worcester Rd.

Vernon, VT 05354-0116 Framingham, MA 01702-5399 Operating Experience Coordinator Jonathan M. Block, Esq.

Vermont Yankee Nuclear Power Station Main Street 320 Governor Hunt Road P.O. Box 566 Vernon, VT 05354 Putney, VT 05346-0566 G. Dana Bisbee, Esq. Mr. John F. McCann Deputy Attorney General Director, Nuclear Safety Assurance 33 Capitol Street Entergy Nuclear Operations, Inc.

Concord, NH 03301-6937 440 Hamilton Avenue White Plains, NY 10601 Chief, Safety Unit Office of the Attorney General Mr. Gary J. Taylor One Ashburton Place, 19th Floor Chief Executive Officer Boston, MA 02108 Entergy Operations 1340 Echelon Parkway Ms. Deborah B. Katz Jackson, MS 39213 Box 83 Shelburne Falls, MA 01370

Vermont Yankee Nuclear Power Station cc:

Mr. John T. Herron Mr. Ronald Toole Sr. VP and Chief Operating Officer 1282 Valley of Lakes Entergy Nuclear Operations, Inc. Box R-10 440 Hamilton Avenue Hazelton, PA 18202 White Plains, NY 10601 Ms. Stacey M. Lousteau Mr. Danny L. Pace Treasury Department Vice President, Engineering Entergy Services, Inc.

Entergy Nuclear Operations, Inc. 639 Loyola Avenue 440 Hamilton Avenue New Orleans, LA 70113 White Plains, NY 10601 Mr. Raymond Shadis Mr. Brian OGrady New England Coalition Vice President, Operations Support Post Office Box 98 Entergy Nuclear Operations, Inc. Edgecomb, ME 04556 440 Hamilton Avenue White Plains, NY 10601 Mr. James P. Matteau Executive Director Mr. Michael J. Colomb Windham Regional Commission Director of Oversight 139 Main Street, Suite 505 Entergy Nuclear Operations, Inc. Brattleboro, VT 05301 440 Hamilton Avenue White Plains, NY 10601 Mr. William K. Sherman Vermont Department of Public Service Mr. John M. Fulton 112 State Street Assistant General Counsel Drawer 20 Entergy Nuclear Operations, Inc. Montpelier, VT 05620-2601 440 Hamilton Avenue White Plains, NY 10601 Mr. Jay K. Thayer Site Vice President Entergy Nuclear Operations, Inc.

Vermont Yankee Nuclear Power Station P.O. Box 0500 185 Old Ferry Road Brattleboro, VT 05302-0500 Mr. Kenneth L. Graesser 38832 N. Ashley Drive Lake Villa, IL 60046 Mr. James Sniezek 5486 Nithsdale Drive Salisbury, MD 21801

REQUEST FOR ADDITIONAL INFORMATION REGARDING PROPOSED LICENSE AMENDMENT EXTENDED POWER UPRATE VERMONT YANKEE NUCLEAR POWER STATION DOCKET NO. 50-271 By letter dated September 10, 2003, as supplemented on October 1, and October 28 (2 letters),

2003, January 31 (2 letters), March 4, May 19, July 2, July 27, July 30, August 12, August 25, September 14, September 15, September 23, September 30 (2 letters), October 5, October 7 (2 letters), December 8, and December 9, 2004, and February 24, March 10, March 24, March 31, April 5, April 22, and June 2, 2005, (References 1 through 30), Entergy Nuclear Vermont Yankee, LLC and Entergy Nuclear Operations, Inc. (Entergy or the licensee),

submitted a proposed license amendment to the Nuclear Regulatory Commission (NRC) for the Vermont Yankee Nuclear Power Station (VYNPS). The proposed amendment, Technical Specification Proposed Change No. 263, Extended Power Uprate would allow an increase in the maximum authorized power level for VYNPS from 1593 megawatts thermal (MWT) to 1912 MWT.

The NRC staff is reviewing your Extended Power Uprate (EPU) amendment request and has determined that additional information is required to complete the review. The specific information requested is addressed below.

Electrical and Instrumentation and Controls Branch (EEIB)

Electrical Engineering Section (EEIB-A)

Reviewer: Amar Pal

1. The licensees submittal dated March 24, 2005 (Supplement No. 25), provided revised station blackout (SBO) analyses for VYNPS in response to a finding documented in the NRCs inspection report dated December 2, 2004. The finding relates to the requirements in Title 10 of the Code of Federal Regulations (10 CFR) Section 50.63, Loss of all alternating current power. Specifically, 10 CFR 50.63(c)(2) requires, among other things, that the time required for startup and alignment of the alternate alternating current (AC) power source and required shutdown equipment be demonstrated by test.

The licensee has not indicated in their submittal that they are planning to do any kind of integrated test, with all parties involved, to show they can meet the 2-hour basis for starting and aligning the alternate AC power source (i.e., the Vernon Hydroelectric Station (Vernon Station)), should it have to be re-started during a regional blackout.

The staff considers such a test to be critical to showing that appropriate procedures and protocols are in place to coordinate between the multiple entities that would be involved.

Provide a discussion on how the licensee intends to meet the 10 CFR 50.63(c)(2) test requirements.

Enclosure 1

2. Since the operators of the Vernon Station are not Entergy personnel or Entergy contractors or vendors, and the station is not manned 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> per day, 7 days per week, the NRC staff requires additional information to have reasonable assurance that the operators will respond to the station as required and perform their duties in a reliable manner as needed to provide the alternate AC power source to VYNPS. Please address the following issues:

a) Are specific operators designated on-call to respond to the Vernon Station, as needed, during periods when the station is unmanned?

b) Are the operators subject to any fitness-for-duty requirements?

c) Are the operators, responsible for responding to the station when it is unmanned, required to remain within a certain distance from the Vernon Station?

d) The licensees submittal states that since the Vernon Station is designated a black start facility under arrangements with the regional grid operator, this designation requires that the facility be capable of being black-started within 90 minutes after the operator is notified. From the onset of a regional grid collapse, during a period for which the Vernon Station is unmanned, discuss all assumptions regarding the time required for the operator to reach the station (e.g., adverse weather conditions, distance traveled), and the time required for the operator to perform the necessary actions to black start the station.

3. Provide a discussion on the agreements between Entergy and other entities to bring the Vernon Station online from black-start conditions in order to provide electric power to VYNPS during an SBO event (i.e., whether there are formal written agreements supported by written procedures). If there are no formal written agreements, discuss why there is reasonable assurance that the alternate AC power source will be available, as needed, consistent with the time frames assumed in the revised VYNPS SBO analyses.

4. With respect to the battery capacity requirements during an SBO event, verify that sufficient DC power is available, under worst case conditions during the two hour coping period, to close the 4160 volt breakers associated with the alternate AC power source.

5. Provide a discussion regarding the changes required to plant procedures for SBO coping (e.g., which procedures will be changed and brief discussion of the changes to be made). Also, address when the operator training on the revised procedures is expected to be completed.

Mechanical and Civil Engineering Branch (EMEB)

Component Integrity and Testing Section (EMEB-A)

Reviewer: Tom Scarbrough and Patrick Sekerak (Questions 147-149)

Civil and Engineering Mechanics Section (EMEB-B)

Reviewer: Cheng-Ih (John) Wu

18. On Page 6 of Attachment 1 to Supplement 26, Entergy states that input for the acoustic circuit model is obtained from pressure transducers installed on instrument lines from the four main steamline (MSL) venturi instrument racks and from strain gauges on each of the four MSLs between the reactor pressure vessel (RPV) nozzles and main steam safety relief valves (SRVs). Provide the basis for the assumption that the venturi pressure transducer measurements are capable of detecting very small pressure fluctuations in the MSL flow that will provide accurate and synchronized input for the acoustic circuit methodology in determining the steam dryer loads. Discuss the validation of the accuracy and synchronization of the venturi pressure transducer measurements in comparison to the MSL strain gauge data.

19. On Page 7 of Attachment 1 to Supplement 26, Entergy states that a test was conducted by Alden Research Labs to determine strain gauge sensitivity and provides a summary of the test results. Provide a detailed description of the sensitivity test, including the test setup, assumptions, applicability, acceptance criteria, and uncertainty analysis.

20. On Page 7 of Attachment 1 to Supplement 26, Entergy states that a benchmark test was performed using the General Electric (GE) Scale Model Test (SMT) facility in San Jose, California, to evaluate the ability of the acoustic circuit methodology to predict steam dryer loads. Provide the basis for the assumption that the GE SMT facility provides a reasonable representation of the sources, types, distribution, amplitude, and frequency spectra of the loads on a steam dryer installed in a boiling water reactor (BWR) nuclear power plant operating at EPU conditions.

21. On Page 8 of Attachment 1 to Supplement 26, Entergy states that pressure measurements from eight points in the SMT piping were provided as input for the acoustic circuit methodology in calculating the steam dryer loads. At VYNPS, Entergy indicates that the input for the acoustic circuit methodology is obtained from four venturi pressure transducers and four MSL strain gauge locations. Discuss the consideration of the differences in input sources and their uncertainties in evaluating the acoustic circuit methodology using the SMT facility and when calculating the steam dryer loads at VYNPS using the acoustic circuit methodology.

22. On Pages 1 and 2 of Attachment 2 to Supplement 26, Entergy describes a two-step power ascension for VYNPS if the EPU request is granted. In the first step, Entergy would increase power from 100% to 115% of the original licensed thermal power (OLTP) with 4-hour hold periods after each 2.5% power increase and a 168-hour hold period at each 5% plateau. Discuss the evaluation of the steam dryer loads that will be performed at each 5% plateau based on the acoustic circuit analysis using MSL data input and the plans to provide that information to the NRC staff.

23. On Page 1 of Attachment 2 to Supplement 26, Entergy states that, if the EPU request is granted during the current operating cycle, the second step of the power ascension for VYNPS would increase power to 120% OLTP following the refueling outage scheduled for the fall of 2005. Discuss the startup test plan that would be followed upon restart from the refueling outage with appropriate hold points at 2.5% and 5% plateaus and the evaluation of plant data at those hold points. Discuss the impact on the power ascension test plan if the EPU is not granted during the current operating cycle.

24. On Page 3 of Attachment 2 to Supplement 26, Table 1 indicates that the plant parameters to be monitored for steam dryer surveillance are moisture carryover, MSL pressure data from strain gauges, and MSL pressure data from pressure transducers.

Discuss the monitoring of MSL pressure data in assessing the performance of the steam dryer at VYNPS during plant operation.

25. In Footnote 1 on Page 5 of Attachment 2 to Supplement 26, Entergy states that the Level 1 and 2 spectra for steam dryer performance criteria will be determined and documented in an engineering calculation or report. Provide the engineering calculations or reports that describe the development and bases for the steam dryer performance criteria.

26. On Page 5 of Attachment 2 to Supplement 26, Entergy specifies 0.35% as the Level 1 performance criterion for moisture carryover. Discuss the basis for the selection of 0.35% as the Level 1 performance criterion for moisture carryover. If 0.35% moisture carryover represents indications of steam dryer damage, discuss the basis for allowing continued power ascension or operation.

27. On Page 6 of Attachment 2 to Supplement 26, Entergy discusses data that will be collected during the power ascension for evaluation of steam dryer performance.

Discuss the monitoring of additional plant parameters (such as MSL flow mismatch and loose parts noise) to identify degraded steam dryer conditions and the prompt action to be taken in response to adverse indications. Also, discuss the monitoring and walkdown inspections of plant equipment (other than the steam dryer) that could be impacted by increased flow-induced vibration (FIV) during EPU operations, such as main steam and feedwater system piping and components.

28. On Page 4 of Attachment 3 to Supplement 26, the Entergy contractor Continuum Dynamics Inc. (CDI) indicates that, because the steam velocity in the MSL is on the order of 200 ft/sec and the speed of sound in steam is approximately 1600 ft/sec, the flow Mach number is on the order of 0.1, and pressure oscillations, if they occur, are expected to be acoustic in nature. Note that this does not mean that the incompressible portion of the flow field plays no role in the oscillations but instead provides the source where mean flow energy is transferred into acoustic oscillations in the system. For structural loadings, however, the acoustic component to the overall pressure fluctuation is most significant. Specify which portion of the flow used in the formulation is considered incompressible. Provide all assumptions used throughout the report.

29. On Page 21 of Attachment 3 to Supplement 26, CDI indicates that the assumption of an out-of-phase vortex shedding in calculating the pressure resulted in non-physical results.

Discuss those findings and the physical implications that were drawn from the stated

mathematical results. CDI also indicates that the gusset splitter plate installed between adjacent steamlines had no affect on reducing dryer damage. Provide the technical basis for this conclusion.

30. On Page 21 of Attachment 3 to Supplement 26, CDI indicates that the acoustic circuit model is validated with data taken in the Quad Cities Unit 2 plant by comparing predictions of the fluctuating pressure at a location in the B MSL with inferred data hoop stress pressure measurements. Explain the basis for the assumed validation of the calculation of steam dryer loads by the acoustic circuit model using strain gauge data from one MSL in Quad Cities Unit 2. Explain the similarities and differences in the pressure and frequency spectra for the various test cases.

31. On Page 22 of Attachment 3 to Supplement 26, CDI compares results between the strain gauge data and predicted pressure associated with different instrument leg temperatures. Given that this step is intended to be a validation of the methodology, it seems more appropriate to predict the expected temperature based on a best estimate, rather than tabulating results using different temperatures. There will likely be a temperature which results in agreement, but if that temperature cannot be predicted accurately, then how does this represent a validation? Confirm whether the calculation requires varying the bulk acoustic speed in the instrument lines in the acoustic circuit analysis.

32. With the uncertainties inherent in the applied FIV (acoustic and computational fluid dynamics) pressure loading, GE indicates on Page 1 of Attachment 6 to Supplement 26 that the time history analysis was performed with a +/-10% time step change to account for uncertainty in the frequency content of the FIV loads. Provide the justification for using the +/-10% uncertainty considering several likely uncertainties involving strain gauge accuracy, instrument leg water temperature, and the assumption of no interaction between acoustic and turbulent flow within the reactor plenum.

33. On Page 7 of Attachment 6 to Supplement 26, GE provides a summary of the computational fluid dynamics (CFD) analysis for the VYNPS steam dryer using large-scale eddy simulation (LES) to assess the turbulence and shedding. Provide the details of that analysis for NRC staff review. For example, confirm whether the CFD analysis was performed considering an incompressible flow and the eddies were assumed to have frequencies similar to those detected in the MSL piping by VYNPS instrumentation.

Discuss how the CFD results were benchmarked. Also, provide a description of the model, methodology (computer code, version and year), assumptions, input values of key parameters, boundary conditions, and results.

34. On Page 9 of Attachment 6 to Supplement 26, GE states that vortex pressures have a localized effect resulting in lateral bending loads on the steam dryer gussets. Discuss the consideration of these loads in the steam dryer analysis and modifications.

35. On Page 11 of Attachment 6 to Supplement 26, GE states that weld quality factors were not applied in its analysis. Provide the basis for the exclusion of the consideration of weld strength in the stress analysis of the VYNPS steam dryer.

36. On Page 13 of Attachment 6 to Supplement 26, GE indicates that the seismic loads on VYNPS steam dryer are documented and unchanged for EPU conditions. Address the seismic evaluation impact on the internal structural response including the dryer and its support brackets due to the increase of the total dryer weight from the modifications.

37. On page 15 of Attachment 6 to Supplement 26, GE indicates that, in final verification of the model and completed analysis cases, one node was found in the modified hood that was inappropriately constrained by the beam below. The node was corrected and a static case was run to assess the stiffness changes. The modified hood stress decreased as a result and the attached end plate stress increased. FIV stresses were scaled in these two components. Confirm whether this additional restraint at the hood changes the fundamental frequency of the analytical model.

38. On Page 15 of Attachment 6 to Supplement 26, GE states that the stress intensity was conservatively used as the acoustic contribution to the FIV stress amplitude. Explain the basis for this assumption.

39. In Attachment 6 to Supplement 26, the modified dryer is shown in Figures 3.1-1 (Page 17) and 3.7.1 (Page 21) for CFD analysis and ANSYS analysis, respectively. The recent hammer test performed for a new steam dryer at Quad Cities indicated that significant coupling exists between the upper portion of the dryer and the skirt with pressure loading applied to the full dryer including the skirt. Confirm whether the full steam dryer model in the CFD and ANSYS analyses consists of both upper dryer banks, supporting ring, and the skirt. If the skirt is not included in the analysis, provide a justification.

40. On Page 22 of Attachment 6 to Supplement 26, GE discusses the sensitivity of the modified dryer analysis results. Discuss the uncertainty of the acoustic circuit analysis pertaining to the formulation equations and parameters including instrument leg water temperature, skirt water level (boundary condition), viscous damping, thermal conductivity, response of Rosemount transmitters, apparent mass, and strain gauge measurement accuracy in transferring pressure data from instrument line to the MSLs and transferring the steamline outer deformation to steam pressure. Also, provide values of parameters mentioned above that were used in the analysis.

41. On Page 22 of Attachment 6 to Supplement 26, GE discusses the modified steam dryer analysis results. The acoustic and CFD pressure loadings were calculated up to 100%

of the current licensed thermal power (CLTP) level. For the square type dryer similar to the ones at VYNPS and Quad Cities, no significant cracking was identified during operation at 100% OLTP. However, this type of steam dryer failed when Quad Cities Units 1 and 2 operated at EPU conditions. Analysis up to 100% CLTP does not demonstrate dryer integrity at EPU conditions. Provide the evaluation of VYNPS modified steam dryer for EPU conditions.

42. On Page 22 of Attachment 6 to Supplement 26, GE states that, with the exception of FIV stresses, the other stresses are calculated for EPU conditions. Explain the basis for this statement.

43. On Page 23 of Attachment 6 to Supplement 26, GE states that there is more than 20%

margin for any American Society of Mechanical Engineers (ASME) Level A or B load combination. Discuss this amount of margin in comparison to the uncertainties in the acoustic circuit and CFD analyses used in calculating the maximum loads on the VYNPS steam dryer during EPU operation. Also, discuss the potential for a pin-hole size break in the steam dryer outer hood face and the impact on steam dryer integrity from hydrodynamic forces due to steam flow being diverted through that hole.

44. On Page 23 of Attachment 6 to Supplement 26, GE states that the finite element analysis for FIV stresses is a linear analysis. Provide the basis for this approach in light of the GE SMT results that reveal different excited frequencies appearing as the flow increases.

45. On Pages 12 and 13 of Attachment 7 to Supplement 26, Figures 3a and 3b show the power spectral density from the VYNPS MSL strain gauges at 100% power ranging up to about 0.2 pounds per square inch differential squared per Hertz (psid2/Hz). On Pages 17 and 18 of Attachment 7, Figures 5a and 5b show the power spectral density from the VYNPS MSL venturi instrumentation ranging up to about 4 psid2/Hz. Discuss the basis and significance of the difference in these two determinations of power spectral density.

46. On Pages 14 and 15 of Attachment 7 to Supplement 26, Figures 4a and 4b show power spectral density (psid2/Hz) versus frequency measured by strain gauges on each of the four MSLs at VYNPS for 80%, 90%, and 100% power levels. The plots indicate that power spectral density measured by the MSL strain gauges at specific frequencies does not vary linearly with power level. See, for example, (a) the MSL A strain gauge plot in Figure 4a which shows the highest power spectral density for 55 Hz to occur at 90%

power; (b) the MSL B strain gauge plot in Figure 4a which shows the power spectral density for 10 Hz to be about equal at 80% and 90% power but to increase significantly at 100% power; (c) the MSL C strain gauge plot in Figure 4b which shows the power spectral density for 170 Hz to be about equal at 80% and 90% power but to decrease significantly at 100% power; and (d) the MSL D strain gauge plot which shows a power spectral density peak for 135 Hz at 100% power that does not appear at 80% and 90%

power. Explain the consideration of nonlinearity of the strain gauge data in applying the acoustic circuit model and the GE SMT results to EPU conditions.

47. On Page 27 of Attachment 7 to Supplement 26, Figure 10 compares the power spectral density at 80%, 90%, and 100% power at the peak load locations on the A-B and C-D sides of the VYNPS steam dryer as determined by the acoustic circuit analysis. Discuss the consideration of nonlinearity in the change in steam dryer loading with power level, and the appearance of load peaks at specific frequencies at 100% power that did not appear at lower power levels (see, for example, 165 Hz on the A-B dryer side, and 145 and 185 Hz on the C-D dryer side).

48. On Page 29 of Attachment 7 to Supplement 26, CDI compares the calculated steam dryer loads for Dresden Unit 2 and VYNPS. CDI indicates that, at 100% OLTP, the maximum pressure loads on the steam dryer in VYNPS are calculated to be 0.730 of the predicted loads in Dresden Unit 2. In light of the Dresden Unit 2 steam dryer loads under EPU conditions being sufficient to cause cracking that was identified during

inspections of the original steam dryer in October 2003 and modified steam dryer in November 2004, discuss the potential for, and consequences of, the VYNPS steam dryer loads reaching or exceeding the Dresden Unit 2 loads at EPU conditions in light of the uncertainty range of the acoustic circuit analysis and the possibility of additional excited frequencies above OLTP conditions.

49. On Page 29 of Attachment 7 to Supplement 26, CDI compares the calculated steam dryer loads for Quad Cities Unit 2 and VYNPS. CDI states that the added energy content present in Quad Cities Unit 2 is the result of distinct deterministic mechanisms that exist at the feed flow rates at which Quad Cities Unit 2 operates, and that these mechanisms are not excited at the much lower feed flow rates at which VYNPS operates. Discuss the basis for the assumption that the higher steam flow rates to be achieved during EPU operation at VYNPS, combined with the plant-specific steam system configuration, will not result in the excitation of distinct deterministic mechanisms similar to Quad Cities Unit 2.

50. On Pages 30 and 31 of Attachment 7 to Supplement 26, Figures 12a and 12b show the power spectral density of the MSL strain gauges in VYNPS is higher than in Dresden Unit 2 for a large portion of the frequency spectra. On page 32, Figure 13 shows the maximum differential pressure and root mean square (RMS) pressure at the nodes on the steam dryer being lower in VYNPS at 100% power than in Dresden Unit 2 at pre-EPU and EPU power levels. Discuss the basis for the higher power spectral density and the lower pressure calculations for the steam dryer in VYNPS compared to the steam dryer in Dresden Unit 2.

51. On Page 35 of Attachment 7 to Supplement 26, CDI states that the use of venturi instrumentation results in a conservatism that tends to increase with steam dryer loads.

Discuss the basis for using venturi instrumentation that diverges from the actual results as the steam dryer loads increase.

52. On Page 38 of Attachment 7 to Supplement 26, CDI states that the work documented in the report meets its Nuclear Quality Assurance Program. Discuss the uncertainties associated with the calculation of the steam dryer loads for VYNPS, including analyses assumptions, correction factors, and instrumentation error.

53. On Page 6 of Attachment 2 to Supplement 27, Entergy describes the 1:17.3 sub-scale GE SMT facility. Discuss the steamline geometry and component differences between the GE SMT facility and the VYNPS as-built configuration, and the potential for different sources of steam dryer loading being present in VYNPS.

54. On Page 6 of Attachment 2 to Supplement 27, Entergy states that microphones were installed in the SMT piping, dryer, and inlet plenum to measure unsteady pressure oscillations in the system. Discuss the potential for differences in source identification and measurement from the microphones in the GE SMT air lines compared to the VYNPS instrumentation.

55. On Page 6 of Attachment 2 to Supplement 27, it is not clear as to how the GE SMT facility in this validation was set up regarding the vibration sources associated with the MSL (i.e., SRVs, electromatic relief valves, main steam isolation valves, high pressure

coolant injection lines, reactor core isolation cooling lines). Confirm whether all 13 test cases were performed at ambient pressure. Discuss how these 13 test cases were performed to simulate the VYNPS systems pertaining to the pressure on the steam dryer. Discuss why the testing is considered valid in that the test conditions deviate from the VYNPS operating conditions.

56. On Page 6 of Attachment 2 to Supplement 27, Entergy indicates that CDI developed an analytical model of the GE SMT for use in predicting loads on the model dryer. Explain the CDI acoustic circuit model that was used in predicting the loads on the dryer in comparison with the SMT data. For each acoustic circuit analysis, describe the input data including microphone numbers and locations, and analytical results in comparison to the corresponding scale model test data. Provide the users manual and theoretical manual pertaining to the computer analysis code for review by the NRC staff.

57. On Page 7 of Attachment 2 to Supplement 27, Entergy states that the 81 cubic feet per minute (cfm) flow rate in the GE SMT facility represented approximately 50% OLTP for Quad Cities Unit 2. Discuss the scaling of the SMT flow rate up to the VYNPS EPU flow rate, and the potential for excitation of additional frequencies at significantly higher flow rates than achieved in the SMT facility.

58. On Page 10 of Attachment 2 to Supplement 27, Entergy states that data from microphone M30 at the outlet of the muffler in the GE SMT facility was provided to CDI in addition to air line instrumentation data. Discuss the influence of the muffler outlet data on achieving a blind benchmark of the acoustic circuit analysis.

59. On Pages 13 and 14 of Attachment 2 to Supplement 27, Entergy indicates that the averaged maximum CDI acoustic analysis predicted loads ranging from 162% to 91% of the SMT microphone measured loads in four test runs (two runs with no air flow and two runs with air flow). In one test run with flow (VY6RUN2), the average value of the pressure load predicted by the acoustic circuit analysis is indicated to have underestimated the microphone measured pressures with a CDI/SMT ratio of 91%. In the other test run with flow (VY12R1), the acoustic circuit analysis is indicated to have overestimated the measured pressures with a CDI/SMT ratio of 109%. Entergy states that, therefore, the CDI acoustic analysis model would appear to be a reasonable tool for predicting steam dryer peak loads. Discuss the acceptance criteria for the validation of the steam dryer load definition calculated by the acoustic circuit model, and the uncertainty range in applying the acceptance criteria in light of the underestimation and overestimation of the average pressure loads in the two test runs with air flow.

60. On Page 17 of Attachment 2 to Supplement 27, Figure 3C shows the maximum pressure and standard deviation for SMT steam dryer loads for the acoustic circuit analysis and SMT data for a burst random and 81 cfm flow. Discuss the underestimation by the acoustic circuit model of the maximum pressure measurements obtained from multiple SMT microphones and the uncertainty of the acoustic circuit model.

61. On Page 20 of Attachment 2 to Supplement 27, Entergy notes that the acoustic model does not predict an SMT peak at 800 Hz. Discuss the absence of the 800 Hz (67 Hz full scale) frequency peak from the acoustic circuit analysis, including the source of

frequency peak in the SMT facility and the impact of its omission on the validity of the acoustic circuit analysis.

62. On Page 20 of Attachment 2 to Supplement 27, Entergy states that, in general, the acoustic model did well under GE SMT flow conditions from 240 to 3200 Hz (20 to 267 Hz full scale), but some mismatches existed at narrow frequency bands. To address the uncertainty, Entergy generated additional power spectral density data sets varying the frequency sample rate by about 10% and established an enveloping curve by using the maximum of the three separate curves. Discuss the basis for broadening the power spectra density spectra in a benchmarking assessment of the acoustic circuit model.

63. On Pages 20 and 21 of Attachment 2 to Supplement 27, Entergy states that it is likely that under predicting the frequency content below 20 Hz (full scale, 240 Hz SMT scale) and shifting the peak response to higher frequencies below 77 Hz would have a conservative impact on stress in the structural assessment. Entergy also states that,

[a]lternatively, other methods could be employed to better define low frequency forces.

Discuss the differences in the acoustic circuit model and the SMT at low frequencies, and whether the acoustic circuit model or SMT provides more appropriate representation at low frequencies in a full size steam dryer operating at EPU conditions in a nuclear power plant. Also, discuss the possible application of the higher of the SMT measurements or acoustic circuit predictions to generate a bounding design load case over the entire frequency range.

64. On Page 24 of Attachment 2 to Supplement 27, Figure 6 compares the power spectral density (PSD) versus frequency plots for Microphone M16 obtained from the SMT facility and predicted by the acoustic circuit analysis during a burst signal with flow. Discuss the lack of consistency between the SMT measured data and the acoustic circuit analysis throughout the entire frequency range in terms of the PSD amplitude and specific excited frequencies.

65. On Page 26 of Attachment 2 to Supplement 27, Figure 8 compares the PSD for a pipe measured signal with the dryer face measured signal and the acoustic model prediction at Microphone M16 over the entire frequency range during a burst signal with flow.

Figure 8 shows (a) the pipe signal higher than the dryer signal and acoustic model prediction throughout the frequency range; (b) the absence of alignment of frequency peaks for the three plots; and (c) the dryer signal exceeding the acoustic model prediction at low frequencies and at certain higher frequencies. From this information, discuss the source of steam dryer loads, the fidelity of the acoustic circuit model, and reliability of the acoustic circuit model in providing a bounding steam dryer load definition.

66. On Page 27 of Attachment 2 to Supplement 27, Entergy states that the acoustic model does a reasonable job of predicting pressure amplitude and energy at the dryer face.

Describe the acceptance criteria and their basis for evaluating the validity of the acoustic circuit model.

67. On Page 27 of Attachment 2 to Supplement 27, Entergy states that, [i]f a 10% load step uncertainty is applied to the data the acoustic model predictions are conservative.

Explain this statement in light of the information on Page 20 and Figure 7 (as well as other figures) that the acoustic load predictions are nonconservative at low frequencies.

68. On Page E1 of Appendix E in Attachment 2 to Supplement 27, the figure shows the acoustic circuit model underpredicting the maximum pressure measured by numerous microphones on the SMT steam dryer outer surface. Discuss the evaluation of the acoustic circuit model in light of this underprediction of maximum SMT steam dryer surface pressure.

69. The figures of the pressure loading of specific microphone locations in Appendix E in Attachment 2 to Supplement 27 show the acoustic circuit model underpredicting the pressure loading at various low, medium, and high frequencies for certain microphones.

For example, see the figures on pages E3, E5, E7, E9, E11, E13, E15, E17, E19, E21, E23, E25, E27, E29, and E31. Discuss the evaluation of the acoustic circuit model in light of this underprediction of pressure loading at various frequencies over the entire spectra.

70. The figures of the pressure loading of specific microphone locations in Appendix F in Attachment 2 to Supplement 27 show the acoustic circuit model with +/-10% uncertainty applied. Although more bounding than the acoustic circuit model without the 10%

uncertainty, the expanded acoustic circuit model continues to underpredict loading at various low, medium, and high frequencies for certain microphones. For example, see the figures on pages F1, F4, F5, F8, F12, and F13. Discuss the evaluation of the expanded acoustic circuit model in light of this underprediction of pressure loading at particular frequencies.

71. Recently, Exelon indicated that adjustments had been made to the CDI acoustic circuit model in an effort to correct the underprediction of steam dryer pressure loads based on data obtained from the instrumented steam dryer at Quad Cities Unit 2 during EPU operation. Discuss the impact of the determination that corrections were necessary to the acoustic circuit model on the assessment of the VYNPS steam dryer, and the implication of those corrections to the validation effort for the acoustic circuit model applied to the VYNPS steam dryer using the GE SMT facility. Also, discuss the impact on the VYNPS steam dryer analysis of any adjustments made by GE to its SMT facility or test analysis, based on the pressure load data obtained from the Quad Cities Unit 2 instrumented steam dryer.

72. With regard to Section 3.1.1 of Attachment 6 to Supplement No. 26 (GE-NE-0000-0038-0936NP), the pressure data from the acoustic circuit analysis (ACA) prediction was translated to ANSYS load vectors for calculation of stresses due to acoustic loading. The translation was checked at key locations in the dryer and GE found that the load vectors were either exact matches or that the ANSYS values were conservative. Identify the conservative load vector and confirm whether and how frequency and phasing were preserved during translation.

73. With regard to Section 3.1.2 of Attachment 6 to Supplement No. 26, the vortex shedding pressure loading was input into ANSYS from a Fluent LES compressible flow simulation of the dryer at 100% of CLTP conditions. Entergy should provide documentation that

benchmarks and validates the CFD codes ability to predict vortex shedding in the complex flows of the dryer.

74. With regard to Section 3.1.2 of Attachment 6 to Supplement No. 26, Entergy should evaluate and submit the potential for the interaction of vortex shedding off the face of the dryer and the steam system acoustic modes. The evaluation should be based on an assessment of significant acoustic modes of the MSLs and dome contributing to pressure fluctuations on the steam dryer.

75. In reference to NEDC-33192P, (Attachment 2 to Exelon letter RS-05-053 dated April 28, 2005), Engineering Report for Quad Cities Unit 1 Scale Model Testing, the Executive Summary (Conclusion 11 for Plant Data and Conclusion 2 for Small Scale Test (SMT)

Facility) mentions that the primary sources of the dryer loading are attributed to acoustic resonances in the dryer dome, which are driven by hydrodynamic flow triggers (SRV singing, MSL turbulence at piping discontinuities, vortex flows at the front of the dryer near the MSL, etc.). However, the possibilities of fluid-structure interaction mechanisms are not totally dismissed, and their existence was to be re-evaluated after the Quad Cities Unit 2 plant data is analyzed. Entergy should explain whether the recent startup of the instrumented new dryer in Quad Cities Unit 2 has shown any indication of fluid-elastic instabilities building up with flow at abnormal rates (in its strain gauge, pressure transducer, or accelerometer data).

76. In reference to Section 6.3.4 of NEDC-33192P, it shows that some MSL and steam dome modes are strongly coupled. Entergy should explain whether any considerations have been given to amplification of surface pressures on the dryer, by the coincident coupling of MSL sources and system acoustic modes.

77. The Executive Summary of NEDC-33192P (Conclusions 8 - 10 for Plant Data and Conclusion 2 for SMT) mentions that existing data from VYNPS MSL strain gauges and venturi lines show no evidence of any singing in downstream valves. In other BWR-3 plants, and in the GE SMT data, singing in valves has been observed, and can lead to high acoustic pressure loads on the steam dryer. Entergy should explain whether there is a potential of acoustic pressure loads (on the dryer) induced by valve singing between pre-EPU and EPU conditions, and provide any estimates of valve singing frequencies (with respect to power level).

78. On Page 7 of Attachment 1 to Supplement No. 26, Entergy discusses measurement of MSL strains using strain gauges. Entergy should provide a justification that its measurement system can separate the dynamic acoustic pressure strains from those caused by the flow noise and the pipe vibrations. In particular, Entergy should provide estimates of the extraneous flow noise in the MSL, the frequencies of the MSL piping breathing mode and the lower frequency in-plane and out-of-plane bending modes, and the contribution of the extraneous in-plane bending mode strains to the hoop strain.

79. With respect to its use of MSL strain gauges, Entergy should provide an evaluation of the ability of the strain gauges on the Quad Cities Unit 2 MSLs to provide adequate dynamic pressure input to ACA analysis.

80. In Attachment 7 to Supplement No. 26 (CDI Technical Memorandum No. 05-06), the MSL strain gauge time signals were shifted for each power condition based on a common reference (the leg A venturi line). Table 1 on page 4 provides a list of the time offsets applied to the strain gauge data. Entergy should provide examples of how the time shifts synchronize the strain gauge and venturi line data. The examples should include time correlation and/or frequency coherence functions showing how the time offsets were chosen.

81. In Attachment 7 to Supplement No. 26, page 5 states that the MSL strain gauge data was filtered to reject signals associated with electrical noise and those associated with the recirculation pump vane passage frequency and its harmonics. Entergy should provide a list of the pump harmonics, along with an explanation of why the pump acoustic signals are not considered to be sources of steam dryer excitation. Also, Entergy should provide examples comparing the unfiltered and filtered MSL data to clearly show the filtering effects.

82. Based on the compliance modeling of the venturi lines, an ACA of each line was performed to correct the fluctuating pressures measured at the ends of the line to those within the MSL fluid. CDI provides plots (Figures 2a and 2b on pages 10 and 11 of Attachment 7 to Supplement No. 26) of the four venturi line transfer functions and their variability with compliance. As compliance increases, the peaks and dips in the transfer functions become less pronounced. In later plots of venturi line pressure spectra, several low frequency pressure peaks coincide with transfer function peaks (10, 21, and 36 Hz), making the compliance a key variable in the ACA analysis. It is not apparent which compliance was actually applied to correct the venturi line data. Entergy should explain the application of a specific compliance for correcting the venturi line data.

83. MSL pressures inferred from strain gauge measurements (using calibrations documented on page 7 of Attachment 7 to Supplement No. 26), and MSL pressures, corrected from venturi line measurements, are plotted as PSD functions at 80, 90, and 100% power in Figures 3 - 6 on pages 12 - 20 of Attachment 7 to Supplement No. 26.

At low frequency peaks (near 10, 21, and 36 Hz), the pressure levels in the venturi line spectra are consistently higher (2 - 3 psid2/Hz) than those in the strain gauge data (0.06 - 0.16 psid2/Hz). Entergy should explain why the strain gauge and venturi signals, which are closely spaced with respect to an acoustic wavelength, are so different at frequencies below 40 Hz.

84. At frequencies above 50 Hz, the pressure spectra inferred from the MSL strain gauges are constant at about 0.008 psid2/Hz (as shown on Figures 3 and 4 on pages 12 - 15 of Attachment 7 to Supplement No. 26), indicating a noise floor in the gauges (no actual pressure signal with amplitude lower than the noise floor can be measured). However, the corrected venturi data show peaks with amplitudes ranging from 0.1 to 1 psid2/Hz at several frequencies above 50 Hz (see Figures 5 and 6 on pages 17-20 of Attachment 7 to Supplement No. 26). Entergy states that including the high frequency peaks in the venturi line data in their ACA analysis adds conservatism to the loads. However, if the venturi line transfer functions incorrectly add peaks to the pressure signals, they can also (and very likely do) remove peaks from the pressure signals (the transfer functions shown in Figure 2 contain many peaks and dips, which lower and increase the corrected pressure signal, respectively). Entergy should explain why a conservative lower bound

on the transfer functions between 0 and 200 Hz (perhaps set to 0.1, which will uniformly increase the pressure signals input to the ACA) was not used.

85. On page 9 of Attachment 7 to Supplement 26 it states, For the most part, above 50 Hz, the strain gage data are at or below their noise floor. It appears that the primary loading of the [VYNPS] dryer will result from loads which have frequency content below 50 Hz.

Entergy should explain why the venturi pressures, which are increasing with frequency above 100 Hz (see Figures 6a - 6d), do not contribute to the primary loading on the dryer. Entergy should discuss the sensitivity of the dryer loading to the MSL strain gauge data and venturi pressure data.

86. In the ACA SMT benchmark report (Attachment 2 to Supplement No. 27, VYNPS Acoustic Model Benchmark - Dryer Acoustic Load Methodology, VY-RPT-05-00006),

the Conclusion section on page 27 states that the ACA systematically underpredicts low frequency differential pressures on the steam dryer (below 20 Hz at VYNPS scale).

Entergy should explain why correction factors based on the discrepancies between low-frequency ACA and directly measured steam dryer pressure spectra from the SMT benchmark are not applied in order to simulate the acoustic pressure loading on the steam dryer.

87. Entergy should compare the recently-measured dryer surface pressures in the Quad Cities Unit 2 plant to those shown in Figure 15 of Attachment 7 to Supplement No. 26 and establish error bounds between actual and ACA-simulated steam dryer pressures.

Entergy should explain whether these error bounds will be applied to the ACA-simulated VYNPS steam dryer pressure loads.

88. Entergy should provide schematics of the steam dome, dryer cavities and MSL including the key dimensions of the analysis to facilitate the review of Attachment 7 to Supplement No. 26.

89. Attachment 3 to Supplement No. 26 (CDI Report No.04-09P, Revision 6), CDI asserts on page 4, based on Mach number and Strouhal number, that the possibility of significant direct hydrodynamic loading on the steam dryer can be rejected. The acoustic pressure is proportional to fluctuating particle velocity, while the hydrodynamic pressure is proportional to steady flow velocity. Therefore, it is doubtful that the two velocities would cancel in the manner suggested. Also, other parameters will affect the ratio of acoustic to hydrodynamic excitation significantly. The argument does support the importance of acoustic excitation, but does not conclusively discount hydrodynamic excitation. Entergy should address these points.

90. In Section 4.1 of Attachment 3 to Supplement No. 26, the acoustic cavity within the steam dome is assumed to have rigid boundary conditions at the walls of the dome and at the walls of the steam dryer. At the interface between the steam cavity and the water level surface, the normal pressure gradient is assumed to be proportional to the pressure itself via the ratio i / a (as shown on page 10). The steam dome cavity is apparently assumed to be a system without losses. Entergy should define the steam dome cavity modeling further, specifically:

a) What is the basis for ignoring motion of the steam dryer walls in the steam cavity model? Are the walls assumed to be rigid? At steam dryer structural resonance conditions, how would the high amplitude motion of the walls affect the loading throughout the steam dryer?

b) What is the constant a relating the pressure and pressure gradient at the water surface, the speed of sound in the steam or water? Also, what is the basis for selecting this boundary condition? How sensitive are the inferred loads to this choice of boundary condition?

c) What is the basis for assuming a lossless steam cavity? If losses were included in the steam cavity model, how would the steam dryer loads change?

How sensitive are the inferred loads to the cavity loss coefficient?

91. ((

)) Other reports, such as Fluent report TM-675, CFD Modeling of the Vermont Yankee Steam Dryer, Section 4 (reference Attachment 1 to Supplement No. 29), and GE report NEDC-33191P, Revision 1, Computational Fluid Dynamics Flow Visualization of Quad Cities Sub-scale Original Dryer Model As a Function of Reynolds Number, page 8-1 (reference Enclosure 1, Attachment 5 to Exelon letter RS-05-059, dated May 6, 2005), show strong evidence that the high-energy fluctuating vortices entering the MSLs are actually coherent over long distances, extending from the MSL inlets back to the steam dryers. ((

))

92. Entergy should provide a detailed description of how the acoustic circuit analysis model considered in Attachment 3 to Supplement No. 26 is assembled and solved at each time step, along with documentation of any quality assurance processes that:

a) Establish that no numerical transient effects are corrupting the analysis. Is the accuracy of the computations dependent on initial conditions? If so, how many time steps are required before accurate solutions are obtained? Alternatively, are the input time signals adjusted to gradually ramp up their amplitudes to avoid numerical transients that corrupt the solution?

b) Explain how the ACA approach responds to coherent and incoherent input signals, particularly those associated with background noise, such as the MSL strain gauge pressure data at frequencies above 50 Hz, as shown in Figures 3 and 4 of Attachment 7 to Supplement No. 26 . Does random background noise lead to conservative, or non-conservative dryer loads at frequencies above 50 Hz?

93. The Quad Cities Unit 2 MSL acoustic pressures inferred from measured strain gauge data are compared to two ACA simulations in Figures 6.4 - 6.6 on pages 26 - 28 of

Attachment 3 to Supplement No. 26. On page 22, it states that the simulated and directly-measured frequency spectra are similar. However, examination of those spectra (the bottom plots in Figures 6.4 - 6.6) does not substantiate that assertion.

Entergy should explain how accurately the ACA methodology simulates the frequency content of the pressure fluctuations. Entergy should further explain how the discrepancies between the frequency content of the measured and simulated MSL pressures in Quad Cities Unit 2 reflect on the accuracy of the simulated pressures on the VYNPS steam dryer, and whether those inaccuracies are accounted for in the acoustic pressure loads used in the VYNPS steam dryer stress analysis.

94. In Section 7 of Attachment 3 to Supplement No. 26, additional in-plant MSL pressure inputs inferred from strain gauge measurements in the Dresden Unit 2 plant are used to relax the assumptions used in prior ACA analyses that the source strengths at the MSL inlets are either completely in or out of phase. Entergy should provide a comparison of frequency spectra of selected dryer loads with and without the assumed source phasing and assess the influence of these assumptions on the dryer loads across frequencies between 0 and 200 Hz.

95. Entergy should define the normalizing function, oN, used in Section 7.2 of Attachment 3 to Supplement No. 26.

96. As discussed in Attachment 1 to Supplement No. 27, VYNPS Acoustic Model Benchmark - Dryer Acoustic Load Methodology, a "blind" benchmark test was performed using the GE SMT facility to evaluate the ability of CDI's acoustic circuit methodology to predict dryer loads. The purpose of the evaluation is not clear because of the use of terms, like the viability of the methodology. Entergy should clearly state the purpose of the evaluation. If a purpose of the report is to use the SMT results to show that a bounding pressure loading can be obtained for the VYNPS dryer using the CDI ACA methodology, then Entergy should demonstrate that the SMT adequately represents the VYNPS steam dryer, the associated steam space, and the VYNPS MSLs.

97. The SMT was performed with flow rates, as shown in the table on page 7 of Attachment 1 to Supplement No. 27, well below EPU conditions (i.e., flow rates equivalent to half Quad Cities Unit 1 pre-EPU power). Entergy should justify why the SMT provides acceptable benchmarking (i.e., explain why SMT testing was not performed up to, and including, EPU conditions).

98. Attachment 1 to Supplement No. 27 does not appear to constitute a typical benchmark analysis. Entergy should define what benchmarking means in this report. In addition, it should provide criteria for benchmarking the predicted pressures, and justify why the criteria were selected based on their intended use of predicting steam dryer structural dynamic stresses. In particular, pressure amplitudes and frequency content from SMT and ACA are compared at specific locations on the dryer face, but phasing of the pressures across the dryer face is not. Also, comparisons of maximum and RMS pressures are given for each frequency, but frequency domain comparisons of the spatial distribution of pressures are not considered. All these characteristics of pressure

loading (frequency, amplitude, phase, and spatial distribution) are important to the excitation of structural modes and the resulting stresses.

99. The selection of the burst random and chirp noise sources (listed in the table on page 7 of Attachment 1 to Supplement No. 27) are not explained, other than to show a graph of their time history. Entergy should define the noise sources, elaborate on why they were used, how they were chosen, and provide comparisons of the SMT dryer pressures and spectrums with and without the noise.

100. The SMT was performed at reduced flow and included noise sources in the MSL, apparently to provide data that could be analyzed with confidence. However, no noise sources were included in the scale model steam dome. Entergy should elaborate on how this SMT has the ability to benchmark the ACA for FIV noise sources created in the steam dome.

101. The microphones on the dryer front surface chosen for SMT did not include any of those located in the center of the dryer (see Figure 2 on page 12 of Attachment 1 to Supplement No. 27). Entergy should explain the basis for selection of the microphone locations, including considerations that were given for investigating pressure distribution and phasing.

102. The reported pressures from the SMT are quite low. At 50% flow and an added noise chirp, the maximum and RMS pressures are less than 70 pascal (Pa) (0.01 psi) and 12 Pa (0.002 psi), respectively (see Figure 3D on page 18 of Attachment 1 to Supplement No. 27). Assuming a quadratic increase in pressures with flow rate, the extrapolated pressure would be less than 403 Pa (~ 0.06 psi) and 69 Pa (0.015 psi),

respectively for 120% simulated Quad Cities Unit 1 pre-EPU power. In the prototype, the maximum pressure would be ~ 3.8 psi and the RMS would be 0.65 psi at 120% pre-EPU power, assuming a scaling factor of 65. Entergy should justify why benchmarking at such low pressure and noise levels is a valid evaluation of the ability of the ACA to predict dryer pressures in the presence of high noise levels.

103. Both the ACA predicted maximum and RMS pressure levels for SMT with 50% flow and an added noise chirp are significantly less than the pressures predicted for no flow and the same noise chirp (see Figures 3B and 3D on pages 16 and 18 of Attachment 1 to Supplement No. 27). The SMT results do not exhibit this trend. Entergy should explain why the ACA predicts higher pressure-levels on the front surface of the dryer when flow is not present, in the presence of the same noise chirp.

104. Comparisons of the time data reveals that the ACA pressure predictions are up to 40%

lower than SMT results for several microphone locations. These differences are discussed by stating that ... in a structural analysis of the modified full scale VYNPS steam dryer, these loads would be effectively integrated by the 1" face plate and heavy 5/8" cover plate and 1/2" gussets (see page 13 of Attachment 1 to Supplement No. 27).

Entergy should explain whether such a statement is appropriate for a benchmark analysis intended to demonstrate the ability of the ACA to predict pressures. Also, Entergy should explain the meaning of effectively integrated and how it is applicable when pressures contain significant energy at a natural frequency and the pressure distribution and phasing result in a high participation factor.

105. Using its benchmark criteria formulated in response to RAI EMEB-98, Entergy should justify the conclusion that this analysis constitutes a benchmark for ACA analysis.

Several differences are noted in the main body of the report (Attachment 1 to Supplement No. 27). These differences are more apparent in the data provided in the Appendices. Most importantly:

a) Many significant pressure peaks measured at frequencies in the range of dryer structural natural frequencies are not predicted by CDI model. These discrepancies occur for many microphone locations. For example, see the PSD comparison at about 1,000 Hz for Microphone M8 located on the cover plate (Appendix E, page E9). The SMT data provides several times higher value for PSD than CDI model.

b) The CDI model predicts peaks at frequencies that do not exist in the data or greatly overpredicts the pressures at many frequencies. These discrepancies occur for almost all microphone locations.

Using its benchmark criteria formulated in response to RAI EMEB-98, Entergy should discuss the significance of the above-mentioned differences and justify the conclusion that this analysis constitutes a benchmark for ACA analysis.

106. The benchmark test shown in Attachment 1 to Supplement No. 27 minimizes the differences between the predictions by the CDI model and SMT results by a technique more appropriate for determining conservative load bounds, not for benchmarking a prediction method. Essentially, the predictions in the frequency domain are broadened to bound and envelope the peaks not predicted in the ACA blind benchmark analysis.

Even with this broadening, several significant peaks are not predicted. Entergy should provide the theoretical basis for broadening.

107. The benchmark test shown in Attachment 1 to Supplement No. 27 did not make any frequency-by-frequency comparisons of pressure phasing or distribution, nor investigate the correlation, coherence, or phasing between the pressures at different locations investigated. Entergy should explain why benchmarking pressure phasing between different dryer locations is not important, for the ACA methodology intended to provide the loading for structural dynamic analysis.

108. The modifications to the VYNPS steam dryer are described in Section 2.0 of Attachment 5 to Supplement No. 26. These modifications use thicker plates, which are expected to reduce the FIV stresses significantly. However, at some locations, the FIV stresses in the modified dryer are higher. For example, according to Table 4.4-1 of Attachment 5, the modified top outer hood has higher stresses than the original one. Entergy should explain the differences between the stresses in the original and modified dryers at the key locations.

109. The structural modifications in the VYNPS steam dryer, which are described in Section 2 of Attachment 5 to Supplement No. 26, have introduced several new weld locations that were not present in the original design. Entergy should explain whether a qualified welding procedure was followed for these underwater welds and whether the inspection results for these welds were acceptable.

110. With regard to Attachment 5 to Supplement No. 26, Entergy should submit the information about the significant frequencies and mode shapes of the modified steam dryer.

111. Entergy performed the sensitivity assessment of finite element analysis by varying the time interval between the pressure time steps by +10%. Why were both plus 10%

and minus 10% variations in time interval not considered? What is the technical basis showing that +/-10% and not larger variations in the time interval are appropriate for steam dryer dynamic stress analysis?

112. Entergy uses 1% of the critical damping in the finite element analysis of the steam dryer.

Entergy should justify the use of 1% critical damping in the modal analysis of the VYNPS steam dryer and describe the sensitivity of the FIV stresses to the critical damping value.

113. In Sections 3.4 to 3.6 of the steam dryer stress analysis report (pages 11 to 14 of Attachment 5 to Supplement No. 26), Entergy presents steam dryer design criteria, dryer loads, and load combinations. Entergy analyzes four different Level D conditions, two include faulted pressure, dead weight, +/- safe shutdown earthquake (SSE), and FIV, whereas the other two include MSL break pressure, normal pressure, dead weight and

+/-SSE. Entergy should discuss the significance of including +/-SSE loads in all four Level D conditions.

114. In two of the Service Level B conditions (see Table 3.6-1 of Attachment 5 to Supplement No. 26), loads due to turbine stop valve (TSV) events are considered, whereas in two other conditions, TSV flow-induced loads are considered. Entergy should explain the difference between TSV and TSV flow-induced loads.

115. In Section 3.8 (page 15 of Attachment 5 to Supplement No. 26), FIV Stress Determination, Entergy selects 10 load case combinations for the alternating stress calculations based on the ANSYS results. Entergy further states that these cases are selected to maximize alternating stress but are also biased to later time points under the assumptions that, as time progressed, the CFD model would be converging on a steady-state solution. Entergy should explain how these load combinations were selected and why they are biased to later time points.

116. In Tables 4.3-1 to 4.3-7 of Attachment 5 to Supplement No. 26, modified dryer stresses in different components are presented. Entergy should clarify the following items regarding these tables:

a) Explain whether these tables refer to stresses or stress intensities.

b) In these tables, local membrane stresses are considered but bending stresses are not considered. However, Columns 6 and 7 refer to primary bending stress.

Explain this contradiction.

c) Explain why only local membrane stresses are multiplied by the weld stress factor, but FIV stresses are not.

d) Comparison of Table 4.3-1 and 4.4-1 shows that the FIV stresses in Table 4.3-1 (1st row, Column 5) is the sum of acoustic membrane stress (2nd row, Column 3, Table 4.4-1) and vortex shedding maximum surface stress (2nd row, Column 4, Table 4.4-1). Entergy should explain why acoustic maximum surface stress (Column 1, Table 4.4-1) is not considered in determining the FIV stresses in Table 4.3-1.

117. In Attachment 2 to Supplement No. 26, Entergy describes its Steam Dryer Monitoring Plan (SDMP). In Table 1, Entergy proposes an hourly surveillance of MSL pressure data from strain gauges when initially increasing above a previously-attained power.

However, a similar surveillance frequency is not specified for MSL pressure data from pressure transducers. Entergy should explain the use of different surveillance frequencies for strain gauges and pressure transducers.

118. Table 2 of the SDMP (Attachment 2 to Supplement No. 26), presents VYNPS steam dryer performance criteria and required actions. One of the Level 2 performance criteria is that the pressure data do not exceed Level 2 spectra. Entergy should explain what are the Level 2 spectra and how the corresponding performance criterion is developed.

Similarly, Entergy should explain the Level 1 spectra and the development of the corresponding performance criteria. Entergy should explain whether the performance criteria are based on the MSL strain gauge measurements, venturi pressure measurements, or both.

119. One of the Required Actions for Level 1 criteria listed in Table 2 of the SDMP is as follows: Promptly initiate a reactor power reduction and achieve a previously acceptable power level within two hours, unless an engineering evaluation concludes that continued power operation or power accession is acceptable. Entergy should explain the Level 1 criteria and the corresponding Required Action.

120. With regard to Attachment 1 (Fluent Final Report TM-675, CFD Modeling of the Vermont Yankee Steam Dryer Phase - II) to Supplement 29, please provide a more detailed discussion of the lessons-learned during the Phase I analysis of the steam dryer along with more information on how these lessons-learned were addressed by the Phase II analysis.

121. On page 1 of Attachment 1 to Supplement 29, the Fluent report states that the model geometry was modified to raise the overall accuracy of the Phase I model. What specific measure or basis is used to support the improvements in accuracy?

122. On page 1 of Attachment 1 to Supplement 29, the Fluent report states that the model geometry was modified to raise the overall accuracy of the Phase I model. Are there any further refinements of the geometric details that could be made? Please discuss any remaining geometric simplifications that are present in the model and the basis for assuming these simplifications do not impact the predictions.

123. On page 1 of Attachment 1 to Supplement 29, the Fluent report states that "the Phase I study showed that an LES model could be successfully applied to the dryer model."

Please define the success criteria used to support this conclusion.

124. On page 1 of Attachment 1 to Supplement 29, the Fluent report states that improvements were made to the physical models. Assuming that certain assumptions are made in a typical CFD simulation, please discuss the remaining major assumptions and limitations of the physical models used in relationship to the flow physics and conditions expected in this specific problem. Please describe how computational limitations affected your modeling approach.

125. On page 2 of Attachment 1 to Supplement 29, the Fluent report states that a "highly refined mesh, consistent with LES requirements" was used in a specific domain.

Discuss the specific rationale used to determine the mesh size in the LES-appropriate mesh region and provide the specific computations used in this determination. Where appropriate, compare mesh sizes to relevant length scales, such as the Taylor or Komolgorov micro-scales or the boundary layer thickness (wall y+). Discuss the size of the mesh in the rest of the model regions (noted to be too large for ideal LES simulations) in terms of relative size of the mesh compared to an ideal LES mesh to give an idea of the relative coarseness of this mesh.

126. On page 3 of Attachment 1 to Supplement 29, the Fluent report discusses a comparison of LES and unsteady Reynolds-Averaged Navier-Stokes (URANS) in an attempt to demonstrate that the LES model would not produce significantly-different results from the URANS model. On page 12, it is noted that Figures 8 through 15 show that the LES model sufficiently represents the URANS solution. In light of the complex jet interactions in the upper dome of the reactor, explain the basis for using the URANS solution as a reference point given the lack of specific validations for this complex flow pattern. In addition, discuss the sufficiency argument for the LES to URANS comparison in the context of Figures 14 and 15 which show a significant variation in velocity magnitude as well as the spatial variation in the velocity.

127. On page 5 of Attachment 1 to Supplement 29, the hybrid mesh is described and it is noted that the flow domain is coupled by resolving the entire domain for the LES simulation. Conceptually, discuss the significance of the coarse mesh on this "boundary condition" at the edge of the LES appropriate mesh region. Given the strong dependence of LES solutions on the applied boundary conditions, discuss the potential for sensitivity of the results to variations in the coarse mesh size.

128. On page 5 of Attachment 1 to Supplement 29, the hybrid mesh is described and it is noted that the flow domain is coupled by resolving the entire domain for the LES simulation. Discuss the spatial and temporal filtering that could be expected to occur as the result of excess diffusion in the coarse tetrahedral region in the upper dome. What is the potential impact of not having resolved potentially higher frequency spatial and temporal variations on the conceptual "input boundary" to the LES appropriate mesh region? Could the lack of higher frequency information in the final results be partially attributed to a lack of resolution of these frequencies in large portions of the domain?

129. On page 5 of Attachment 1 to Supplement 29, it is stated that "the success of obtaining an LES solution on the hybrid mesh hinged on the capacity for the LES model to sufficiently resolve the flow field on the coarse mesh." The concept was tested by comparing the LES and URANS solutions. How can one determine that the LES model sufficiently resolves the flow on the coarse mesh without comparison to data? Is

comparing a specific turbulence model to another turbulence model considered to be a validation?

130. On page 9 of Attachment 1 to Supplement 29, it is noted that a central differencing scheme is used. What is the order of accuracy for the solution and what impact does the boundary treatments have on this accuracy? Does the accuracy at the boundaries impact the overall solution accuracy? Were higher order schemes attempted? What is the expected sensitivity of the solutions to the central differencing scheme and the wall treatment accuracy?

131. On page 9 of Attachment 1 to Supplement 29, it is noted that a dynamic Smagorinsky-Lilly model for subgrid scale stresses is used. What is the expected sensitivity of the solutions to variations in the subgrid scale stress model?

132. On page 9 of Attachment 1 to Supplement 29, it is noted that the turbulence level of the boundary condition is not important because the flow will develop as it traverses through the dryer. Please comment on the accuracy in the turbulence level as it reaches the LES appropriate mesh. Does the turbulence develop appropriately in the porous models within the dryer? Does the turbulence develop appropriately in the relatively coarse tetrahedral mesh in the upper dome? Are any sensitivities completed to justify the statement that the turbulence level at the inlet "does not have any impact" on the flow in the dryer?

133. On page 10 of Attachment 1 to Supplement 29, it is noted that y+ values are in the range of 3,000 to 15,000. What are "best practice" values for y+ in an LES simulation?

Assuming the y+ values used are larger than "best practice" guidelines would require, discuss the potential impact of the wall treatment (wall boundary condition) on LES predictions.

134. On page 10 of Attachment 1 to Supplement 29, the time step size is listed. Please provide further details on the determination of the time step size for this type of LES analysis.

135. On page 11 of Attachment 1 to Supplement 29, the determination of pressure differences is discussed. Are pressure fluctuations expected on the back side of the plate? Would this model determine pressure fluctuations in this region given the location of the inflow boundary condition and the non-prototypical influence of the porous media regions? What impact might these assumptions have on the reported pressure fluctuations?

136. Given the complex nature of the jets and interactions highlighted in Figure 32 of Attachment 1 to Supplement 29, discuss the impact of the coarse tetrahedral mesh on these flows and its potential subsequent impact on the "boundary" to the LES appropriate mesh region.

137. On page 17 in the first paragraph of Attachment 1 to Supplement 29, it is implied that improvements to accuracy are obtained locally in the specific region that is resolved using the LES appropriate mesh. The basic question is whether or not additional fluctuations would be present if the entire domain were modeled with an LES

appropriate mesh. Please summarize the basis for assuming that the prediction in a local region is accurate when the predictions in the surrounding regions can be assumed not to be accurate. This discussion should consider the importance of boundary conditions in LES predictions.

138. With regard to the work described in Attachment 1 to Supplement 29, discuss in general the applicability of a single CFD prediction (no sensitivity studies for key assumptions or parameters) in a flow domain where no data are used for validation or benchmarking.

139. With regard to the work described in Attachment 1 to Supplement 29, please provide a case file for the Fluent simulations at 100% and 120% load condition for review by the NRC staff. In addition, a representative full data set for each load condition is requested. Finally, a mesh database (GAMBIT *.dbs) file is requested.

140. On page 9 of Attachment 1 to Supplement 29, a uniform inlet turbulence intensity of 2%

is specified. The inlet dissipation rate (which, along with turbulence intensity, defines characteristic flow length scales) is not specified. Entergy is requested to discuss the sensitivity of the simulated steam dryer loading to the inlet turbulence intensity and dissipation rate.

141. On page 9 of Attachment 1 to Supplement 29, a porous media is described which simulates the head loss across the dryer. Entergy is requested to describe the effects of the porous media model on the turbulence intensity and characteristic length scales of the jet flow emanating from the top of the dryer. Also, the sensitivity of the simulated steam dryer loading to the porous media should be provided.

142. The PSDs averaged over the dryer face plate are compared for 100% of CLTP and 120% of CLTP conditions (or EPU conditions) in Figures 45 and 46 of Attachment 1 to Supplement 29. The comparison shows significant increases in loading at EPU condition at frequencies of about 32, 45, and 62 Hz. The amplifications strengthen near the MSL inlets. Entergy indicated on page 48 that low-frequency increases are due to hydrodynamic effects, and high-frequency increases are due to acoustic effects.

Entergy also indicated that the time step size used in the compressible LES solutions is too large to resolve acoustic effects accurately. Entergy is requested to explain whether the peaks at 32, 45, and 62 Hz are due to acoustic amplification, and if so, explain how the time step size affects the amplitudes of the peaks. The evaluation should be based on an assessment of significant acoustic modes of the MSLs and dome contributing to pressure fluctuations on the steam dryer.

143. Since the CFD analyses at 120% of CLTP conditions reported in Figures 45 and 46 of Attachment 1 to Supplement 29 show large increases (about a factor of 10) in steam dryer loading at several discrete frequencies, Entergy is requested to provide corresponding maximum vortex shedding stresses (as defined in Table 4.4-1 in the report, VYNPS Modified Steam Dryer Analysis, GE-NE-0000-0038-0936P, March 2005) for key dryer components.

144. On pages 14 and 15 of Attachment 3 to Supplement 26, ((

))

145. With regard to the work described in Attachment 1 to Supplement 29, ((

))

146. The CFD results indicated that the pressure PSD contains more peaks for the 120% of CLTP condition than the 100% of CLTP power condition. It is believed by Fluent that these peaks were introduced due to the interaction of the turbulent flow with the acoustic loading. Discuss the effects of the interaction between the acoustic and the hydrodynamic loadings on the forcing functions applying to the steam dryer.

147. On page 3-4 of Attachment 4 to the application dated September 10, 2003, ASME Code Section XI, Subsection IWB-3641 is cited as the code requirements governing the stress analysis of the modification of the Core Spray nozzle and safe end. Please discuss the applicability of IWB-3641, which provides procedures for piping flaw evaluation, in lieu of the original Code of construction for analysis of modifications made to this component.

148. On page 3-20 of Attachment 4 to the application dated September 10, 2003, the section addressing pipe stresses states: For those systems that do not require a detailed analysis, pipe routing and flexibility was evaluated and determined to be acceptable.

a) Discuss the method used for evaluating flexibility of piping.

b) What acceptance criteria are applicable to the flexibility evaluation?

c) Which piping systems were evaluated with this approach?

149. On page 3-35, Table 3-3, of Attachment 4 to the application dated September 10, 2003, the primary plus secondary stress level reported for the feedwater nozzle and safe end under constant pressure power uprate (CPPU) conditions is extremely close to the allowable ASME Code limit. Please discuss the general analytical approach used to calculate this stress. Also, explain the primary reasons for the 21% increase in stress over the CLTP stress reported, and why the feedwater nozzle CPPU stress and usage factor increases are so much larger than the increases for the other components listed in Table 3-3.

Plant Systems Branch (SPLB)

Balance of Plant Section (SPLB-A)

Reviewer: Devender Reddy

25. Spent Fuel Pool Cooling and Cleanup System (Safety Evaluation (SE) Template Section 2.5.3.1)

Section 6.3.1 of Attachment 6 of the application dated September 10, 2003, indicates that in the unlikely event of a complete loss of spent fuel pool (SFP) cooling capability, the SFP will reach the boiling temperature in six hours. This conclusion does not appear to be consistent with the information that is provided for the alternate cooling system (ACS) in Updated Final Safety Analysis Report (UFSAR) Section 10.8 which indicates that upon a loss of all SFP cooling, boiling will occur in two-to-three days. Please explain this apparent inconsistency.

26. Reactor Auxiliary Cooling Water Systems (SE Template Section 2.5.3.3)

UFSAR Section 10.8 indicates that the deep basin has a water capacity of 1.48 million gallons and that a water inventory of 1.45 million gallons is sufficient to assure seven days worth of ACS cooling capability. Please explain in detail how this conclusion was reached for post-EPU operation, quantifying all water additions and losses that are assumed to occur over this seven-day period along with how these values were determined, and how much inventory is required at the end of seven days to satisfy pump net positive suction head (NPSH) requirements.

27. Condensate and Feedwater System (SE Template Section 2.5.4.4)

The response to RAI SPLB-A-17 in Supplement No. 28 indicates that there is sufficient margin between the minimum transient reactor feedwater pump (RFP) suction pressure and the current RFP suction pressure trip setpoint to ensure RFP operation during normal operation and the loss of one condensate pump transient. This does not appear to be consistent with the information provided in the RAI response that indicates that the condensate pumps only have a 7% flow margin to pump runout conditions, which would suggest that two condensate pumps operating are not sufficient to ensure RFP operation following the loss of one condensate pump. Please explain the basis for concluding that continued RFP operation is assured following the loss of one condensate pump.

28. Condensate and Feedwater System (SE Template Section 2.5.4.4)

EPU operation will result in a substantial reduction in the available condensate and feedwater system operating margin and plant modifications must now be credited for preventing challenges to reactor safety systems that would otherwise occur upon the loss of a RFP or a condensate pump. Because the plant response to loss of RFP and

condensate pump events following EPU implementation is substantially different from the response at the current licensed power level, and the expected EPU response has not been confirmed by previous full-power tests or plant transients, the NRC staff requires that the power ascension test program include sufficient testing at the 100% EPU power level to confirm that the plant will respond as expected following a) the loss of a RFP, and b) the loss of a condensate pump. Please provide a complete description of the full-power testing that will be completed in this regard for the staffs review and approval, and propose a license condition that will assure that the proposed testing will be completed as described and that the results are fully satisfactory as a prerequisite for continued operation at the EPU power level.

29. Power Ascension and Testing Plan (SE Template Section 2.12)

The licensees response to RAI SPLB-A-20(a) in Supplement No. 28, is incomplete in that only the balance-of-plant (BOP) startup transient response criteria for the main steam isolation valve closure and generator load rejection transients were addressed.

In accordance with the review criteria provided in NRC Review Standard RS-001 and draft Standard Review Plan (SRP) Section 14.2.1, the staffs request applies to the BOP transient response for all of the startup tests that are potentially impacted by the proposed EPU. Please provide the additional information that is needed in this regard.

Probabilistic Safety Assessment Branch (SPSB)

Containment and Accident Dose Assessment Section (SPSB-C)

Reviewers: Richard Lobel (Questions 47-51), Harold Walker (Question 52)

47. The response to RAI SPSB-C-41 is not clear as to why required NPSH values, based on lower pre-EPU suppression pool temperatures, satisfy pump requirements at the higher EPU suppression pool temperatures. Does the increased suppression pool temperature affect the magnitude of the required NPSH or the time period at a given required NPSH, or both?

48. In response to RAI SPSB-C-39, Entergy stated that the emergency operating procedure NPSH curves are independent of specific event scenarios. However, credit was taken for the minimum available NPSH curves. Arent these curves event-specific to the large-break loss-of-coolant accident (LBLOCA) at pre-EPU conditions? Why is this acceptable?

49. Supplement 25, dated March 24, 2005, states that credit for containment accident pressure is no longer required in determining adequate available NPSH for the residual heat removal and core spray pumps for the postulated Appendix R fire and the SBO scenario. Was it necessary to take credit for the minimum available NPSH curves in reaching this conclusion?

50. Provide a comparison of the emergency core cooling system (ECCS) pump flow rates for the 10 CFR 50.46 LBLOCA analysis with the ECCS flow rates used for the short-term and long-term NPSH analyses.

51. Describe how instrument uncertainty is taken into account, either in the EPU containment analyses (both peak pressure and minimum pressure for NPSH),

surveillance procedures, or in some other way.

52. The effects of a loss-of-ventilation on a SBO event are discussed in Supplement No. 25, Attachment 2, Section 2.3. Please provide the references listed in that section for NRC staff review (i.e., References 3, 6, 7, 12, 13, and 16).

Reactor System Branch (SRXB)

Boiling Water Reactors and Nuclear Performance Section (SRXB-A)

Reviewers: Muhammad Razzaque (Questions 7-12), Tai Huang (Questions 13-16),

George Thomas (Questions 17-22), Len Ward (Question 23),

Zena Abdullahi (Questions 24-58)

7. Table 1-1 of the VYNPS Power Uprate Safety Analysis Report (PUSAR)

(i.e., Attachment 4 of the application dated September 10, 2003), lists computer codes used for CPPU for transient analysis. Please clarify which code was used for the over-pressure protection analysis.

8. Section 3.10.1 of the VYNPS PUSAR discusses the shutdown cooling (SDC) analysis for CPPU. However, SDC with single-loop operation was not discussed in the PUSAR.

Please clarify which criteria apply to SDC with single-loop operation, and whether the criteria are satisfied at CPPU conditions.

9. Section 2.2 of the PUSAR states that a representative cycle core was used for the CPPU evaluation. Please define the VYNPS representative cycle core and discuss which GE fuel type is limiting from the standpoint of fuel thermal limits.

10. Please provide the following additional information regarding the VYNPS LBLOCA analysis for the CPPU:

a) Describe the VYNPS limiting single failure LBLOCA event for the current licensing basis conditions and for EPU conditions, respectively. Typically, the events are the same; but if the events are different for VYNPS, then explain the reasons. Also, describe the type of reactor core that was assumed for the EPU analysis (i.e., whether the core was assumed to be loaded with the same kind of GE fuel, or a mixed-core was assumed). If it was a mixed-core, then describe which GE fuel types used, their proportions and burnup level, etc.

b) The peak cladding temperature (PCT) changes due to CPPU are typically within 20 EF; but for the VYNPS EPU, it was determined to increase by 50 EF. Discuss the reasons behind such a comparatively large increase of the PCT, and why VYNPS is an exception in this regard.

11. As shown in Supplement No. 4, Attachment 4 (NRC Review Standard RS-001, BWR Template Safety Evaluation (SE) as revised for VYNPS), Section 2.8.6, Fuel Storage, draft General Design Criterion (GDC) 66 is applicable to the NRCs review of the affect of the proposed EPU on new and spent fuel storage. This GDC requires prevention of criticality in fuel storage systems by physical systems or processes, preferably utilizing geometrically-safe configurations. The NRC staff did not find any discussion on criticality of new and spent fuel storage in the licensees submittals. Please provide this information.

12. In Section 7.2.1, Step # 3, NUMARC 87-00, Revision 1, "Guidelines and Technical Bases for NUMARC Initiatives Addressing Station Blackout at Light Water Reactors," it

is indicated that the minimum permissible usable gallons of water in the condensate storage tank (CST) should be recorded in the plant Technical Specifications (TSs). In Supplement No.

25, Attachment 2, Section 2.1, the licensee stated that in order to ensure that at least 100,000 gallons of usable CST inventory is available during an SBO, the minimum administrative limit for CST level identified in procedure OP 0150, "Conduct of Operations and Operator rounds,"

will be increased. The current CST minimum volume in TS 3.5.E.1.b is 75,000 gallons. Please justify why the TSs do not need to be revised, consistent with the recommendations in NUMARC 87-00.

13. As discussed in PUSAR Section 2.4, Stability, VYNPS currently operates under the Option I-D solution. Please provide a clarification for the following areas:

a) The current flow-biased average power range monitor (APRM) scram provides automatic detection and suppression of core wide instability. Provide the technical basis that supports the conclusion that regional mode reactor instability is not probable under EPU conditions.

b) Describe any alternative method to provide automatic detection and suppression of any mode of instability other than through the current flow-biased APRM scram.

c) Describe how the dominance of the core-wide mode oscillations is maintained under the EPU conditions. Specifically, describe how the effects on axial and power distributions (which change for EPU core loadings) have been taken into account in the new calculations to ensure the dominance of the core-wide mode.

Are there any negative effects on stability of the EPU core loadings?

14. Provide the technical basis that supports a conclusion that the hot bundle oscillation magnitude portion of the detect-and-suppress calculation is not dependent upon the core and fuel design.

15. The hot channel decay ratio provided for EPU is very close to acceptable criteria limits.

In addition, the core-wide decay ratio is not provided. Have the proposed EPU core loadings degraded the stability performance significantly? Provide a table of hot channel and core-wide decay ratios at the most limiting state point for the last three cycles and the proposed EPU condition. The purpose is to evaluate the impact of the EPU on relative stability of the plant, and the applicability of Option I-D to VYNPS under these new conditions.

16. It appears that the APRM flow-biased scram setpoint will be maintained at the same absolute levels (in terms of megawatts) for EPU as for CLTP. Please address the following:

a) Because the distance (in terms of megawatts (MWs)) between the most limiting power/flow operating point and the scram setpoint represents the oscillation amplitude required for scram, has this distance (i.e., the maximum oscillation amplitude) changed for EPU? Provide a graphical power/flow map representation of the new and old operating domains and the VYNPS scram setpoints, including the exclusion region. Note that the most limiting condition in

terms of the oscillation amplitude is not necessarily the most unstable point, but the one that results in the largest amplitude.

b) If the above distance (i.e., the oscillation amplitude required for scram) has changed, is the CLTP scram setpoint still conservative for the EPU?

c) Has the resolution of the recent DIVOM (delta critical power ratio (CPR) over initial minimum CPR versus oscillation magnitude) 10 CFR Part 21 notification had any effect on VYNPS implementation of Option I-D? What DIVOM correlation is used to justify the EPU scram line? Is it a plant-specific or generic correlation? Please provide details.

17. In Supplement 4, Attachment 5, Matrix 8, page 13, note for SE Section 2.8.5.4.1, there is an explanation for uncontrolled control rod withdrawal from a subcritical or low power startup condition. In this explanatory section, this event is considered as an accident and a fuel enthalpy of 170 calories/gram is given as the acceptance criterion. However, in SRP Section 15.4.1, this event is considered as a transient, not as an accident, and hence specified acceptable fuel design limit criteria is applied. Why is this event considered as an accident rather than a transient?

18. Review Standard RS-001, BWR Template SE for Sections 2.8.5.1, 2.8.5.2.1, 2.8.5.2.2, 2.8.5.2.3 , 2.8.5.3.1, 2.8.5.4.3, 2.8.5.5 and 2.8.5.6.1, guides the NRC staff to reach a conclusion regarding reactor coolant pressure boundary (RCPB) pressure limits not being exceeded. However, the revised template reflecting the VYNPS licensing basis (provided in Supplement Nos. 4 and 8) does not include any acceptance criteria in the Regulatory Evaluation portion of each of these SE sections related to the RCPB.

Please confirm that draft GDC-9, Reactor Coolant Pressure Boundary, is applicable to these sections and provide a markup of the SE template accordingly.

19. The following question relates to the review for SE template Section 2.8.5.4.3, Startup of a Recirculation Loop at an Incorrect Temperature and Flow Controller Malfunction Causing an Increase in Core Flow Rate.

VYNPS UFSAR Section 14.5.6 states that: [f]low dependent operating limits, MCPR(F)

[minimum critical power ratio (MCPR) flow-dependent limit], LHGRFAC(F) [linear heat generation rate (LHGR) flow-dependent multiplication factor] and MAPFAC(F)

[maximum average planar linear heat generation rate (MAPLHGR) flow-dependent multiplication factor] are developed to ensure that core thermal limits are not violated for the limiting flow increase transients. This UFSAR section also states that [t]hese flow-dependent limits are generic ARTS [APRM and rod block monitor TS] program limits and are derived from a conservative treatment of a two recirculation pump slow flow runout event. The validity of the flow-dependent limits for the core flow increase transients was reconfirmed for the GE14 fuel introduction. Confirm that validity of the flow-dependent limits were verified for the EPU operating conditions.

20. With respect to PUSAR Section 6.5, Standby Liquid Control System:

a) The results of the licensees anticipated transients without scram (ATWS) analyses at EPU conditions determined that the calculated peak vessel bottom

pressure is 1490 psig as shown in PUSAR Table 9-5. However, the standby liquid control system (SLCS) pump discharge pressure value proposed for the surveillance test is only 1325 psig (reference proposed revision to Surveillance Requirement (SR) 4.4.A.1). Clarify why this test pressure is acceptable.

b) PUSAR Section 6.5 states that because of the increase in SLCS pump discharge pressure under EPU conditions, the surveillance test pressure in SR 4.4.A.1 will be increased from 1320 psig to 1325 psig. What is the SLCS discharge relief valve setpoint under EPU conditions? Taking relief valve setpoint tolerance into consideration, how much margin is there to prevent the relief valve from lifting?

21. With respect to PUSAR Section 9.1, Anticipated Operational Occurrences, identify the staff-approved evaluation model used for the plant-specific loss of feedwater flow event analysis.

22. With respect to PUSAR Section 9.3.1, Anticipated Transients Without Scram:

a) Identify the staff-approved evaluation model used for the plant-specific ATWS analysis.

b) Confirm that operator actions specified in the VYNPS emergency operating procedures are consistent with the generic Emergency Procedure Guidelines/Severe Accident Guidelines insofar as they apply to the operator actions for ATWS. Specify the time delay used in the ATWS analysis for starting of the SLCS pumps.

23. Supplement No. 24, Attachment 3, Table 6-4, Metric Summary for VYNPS (120%)

presents the predicted maximum bundle powers and bundle power-to-flow ratios with exposure for the projected uprated conditions. In support of the staffs review of the LOCA analyses, please provide the following information specific to VYNPS:

a) For the peak power fuel assemblies, provide the limiting axial power distributions and radial peaking factors. For different exposures, select bundles with limiting axial power peaking operating with bottom peaked, double-hump or mid-peaked, and top-peaked axial power distributions. Please assure that the axial power distribution corresponding to the exposure with the highest hot bundle exit void fraction is also provided.

b) Include in the selected bundles, the power distribution and peaking corresponding to the maximum powered bundle selected for the cycle state point of 13.184 gigawatt days per standard ton. Table 6-4 also shows that the bundle is operating at 7.51 MW. Please provide the corresponding predicted bundle operating conditions, including axial power distribution, void fraction distribution and bundle nodal exposure.

c) Please also include the bundle inlet mass flow rate and inlet temperature.

Background for RAIs SRXB-A-24 through SRXB-A-58 In the Supplement No. 24 response to the NRCs RAI SRXB-A-6, Entergy compared ((

)) Additional information is required, as delineated below. The RAIs are grouped into six different sections. Parts I through VI, respectively, focus on operating experience, reference plants core follow benchmarking, safety limit minimum critical power ratio (SLMCPR) uncertainties, qualification of the steady-state neutronic methods, applicability of the thermal-hydraulic models and correlations and significant key parameters, and void-quality correlation.

PART I - Operating Experience

((

))

24. Supplement No. 24, Attachment 3, Figure 6-6, presents the peak LHGR ((

))

Are bundles (pins) setting the peak limit for non-GE14 fuel? What uncertainties are applied to the peak LHGR to account for the calculational uncertainties?

PART II - Reference Plants Core Follow Benchmarking RAI SRXB-A-6(b), requested that the licensee confirm that the calculational and measurement uncertainties applied to the thermal limits calculations are applicable for operation at the EPU conditions. The response to the RAI provided ((

)) The licensee concluded that the traversing incore probe (TIP) comparison results are well within the results previously approved. The response also states that the exposure dependence has already been discussed and justified in RAI 3 for Licensing Topical Report (LTR) NEDC-32694P-A. The submittal states that the non-adaptive, nodal RMS difference is less than (( )), which indicates that the axial power distribution prediction is adequate. The following RAIs identify additional areas that have not been addressed in the RAI response.

25. Explain the reason for the increase in the ((

)) The RAI response proposed void fraction weighting ((

)) Justify why the nodal uncertainties for ((

)) in order to establish the uncertainties that should be applied to VYNPS bundle powers and thermal limits.

26. ((

)) Demonstrate that for the 20% uprate condition for the entire operating domain, VYNPS would not operate with core power/flow ratio greater than (( )).

27. State what criteria are used to establish that the axial and nodal uncertainties are acceptable and do not reflect degradation of the neutronic methods predictions of the nodal and axial power distribution and peaking.

28. State where the axial and nodal uncertainties are accounted for in the thermal limits calculations and safety limit analyses.

29. State whether or not the axial and nodal uncertainties are accounted for in the initial steady-state conditions calculations for the transients and accident conditions (ECCS-LOCA). For example, the axial power peaking and distribution affect the response to LOCA and transients. Therefore, any underpredictions in the axial nodal powers could change the plants response. If nodal and axial uncertainties are not applied, justify how potential underpredictions in the axial and nodal powers are accounted for.

30. Explain how the axial and nodal uncertainties are applied to the nodal exposures, the operating MAPLHGR (MAPRAT), and the operating LHGR (PKLHGR), to account for the nodal inaccuracies of the steady-state neutronic method and code systems.

31. ((

))

Comparing against a fixed limit value assumes that the selected maximum powered bundles are limited to low exposure bundles. State whether the ratio of the peak LHGR to the LHGR limit monitored in the core simulator (e.g., 3D MONICORE) includes the decrease of the LHGR limit with exposure.

32. State if any uncertainty is applied to the LHGR limit in the core monitoring system and if the uncertainty value is increased with exposure as the limit decreases. This is important since the peak reactivity and nodal powers increase with exposure, when the Gadolinium (Gd) burns out (>8 GWD/ST) and the thermal-mechanical limit decreases with exposure at approximately 15 GWD/ST.

33. Describe how the core monitoring system and offline calculations calculate the peak nodal LHGR and the corresponding pin-wise peak LHGR, MAPLHGR and the accumulated exposure.

34. Since no gamma scans or isotopic inventory measurements are available for the current fuel designs (GE14) as operated, justify why it is acceptable to base the assessment of the predictions of the nodal powers and the pin powers on code-to-code comparisons.

35. Provide VYNPS-specific core follow data for operation at the current licensed thermal power. Include axial individual TIP measured versus calculated data for limiting conditions in terms of four-bundle nodal powers. Provide the individual TIP data for different power peaking (top-peaked, bottom-peaked and mid-peaked or double-hump).

Include the corresponding four-bundle predicted conditions (e.g., void fractions, nodal exposures).

36. The individual axial TIP data shows that the ((

))

Explain how it can be ascertained that the PCTIP peaking being closer to specific bundle power peaking is not due to variability in the positions of the TIPs which may reflect the response of specific bundles and not necessarily the maximum powered bundles. Provide an evaluation that establishes the reason that the measured PCTIP reflects the response of specific bundles.

PART III - SLMCPR Uncertainties (NEDC-32694P-A and NEDC-32601P-A)

RAI SRXB-A-6(b) asked VYNPS to confirm that for the EPU conditions, the calculational and measurement uncertainties applied to the thermal limits analyses are valid for the predicted neutronic and thermal-hydraulic core and fuel conditions. The licensee used ((

)) and concluded that the current bundle power uncertainties were acceptable. The following RAIs address additional uncertainty contributors in the SLMCPR calculations that have not been addressed in the RAI responses.

37. Section 3.1.1 Model Uncertainty of NEDC-32601P-A discusses the method used to determine the accuracy of TGBLA in computing the fuel pin peaking factors. The accuracy of the TGBLA model was established by comparing its peaking factor distributions with Monte Carlo (MCNP) benchmark results. Table 3-1 presents the RMS differences between the MCNP and TGBLA rod differences for 8x8, 9x9 and 10x10 lattice designs ((

)) Confirm that this is the case.

Specifically, MCNP is not a depletion code and there are no biases assumed for MCNP calculations to demonstrate that the impact of the infinite pin power peaking with exposure is accounted for. Justify why it is acceptable to establish infinite lattice pin power peaking at BOL conditions to determine the uncertainties associated with pin power peaking as the bundles deplete under hard spectrums with fuel designs and loading that do not reflect the current core conditions.

38. Table 3-1, Summary of TGBLA/MCNP Pin Power Comparisons, of NEDC-32601P-A combines the RMS differences in rod power using historical GE fuel designs (8x8, 8x8 GE9, 9x9 GE11, 10x10 GE12 and 10x10 SVEA96) ((

)) Justify why the uncertainty calculation should not be limited to fuel designs with similar characteristics and operated conditions, since pin power peaking is dependent on the fuel design, loading (enrichment, Gd loading, etc.) and operation (e.g., high void conditions).

39. ((

)) The fuel designs used to establish the gradient peaking (( )) is not discussed in the SLMCPR LTR.

a) State if similar (( )) analyses were performed for cores loaded with GE14 fuel and core designs that reflect the current and proposed operating conditions.

b) Demonstrate the validity of the currently used gradient peaking of (( )) for the current operating strategies and fuel designs (GE14). State if similar ((

)) to establish the influence of neighboring bundles on the local peaking distribution.

c) State whether the core simulations calculations are performed at different exposures. If not, establish a methodology that accounts for the exposure dependence.

40. ((

)) State if the current plant-specific SLMCPR calculations (( )) uncertainty was included in the

(( ))

41. In the review of the SLMCPR methodology, the staff asked in RAI 5 the following, The process computer monitors peak kw/ft and MAPLHGR. While MCPR depends primarily on the radial bundle power distribution, peak kw/ft and MAPLHGR depend on the bundle axial power distribution and, consequently are significantly more sensitive to the 3-D MONICORE replacement of the TIP/LPRM axial power distribution. Provide an uncertainty analysis for the 3-D MONICORE prediction of peak kw/ft and MAPLHGR.

Update this RAI response. Justify why the peak Kw/ft uncertainty (see RAIs addressing changes in the peak and nodal uncertainties) would not change for the current operating strategies and fuel designs (GE14). Describe how the uncertainty is applied in 3D MONICORE.

42. Section 3.2, Conversion of Peaking Uncertainty to R-factor Uncertainty of NEDC-32601P-A discusses that the R-factor represents the influence of the rod power peaking on the critical power. In addition, the R-factor methodology is described in NEDC-32505P, An R-Factor Calculation Method for GE11, GE12, and GE13 Fuel, dated July 1999. The bundle R-factor is an input to the GEXL correlation. ((

)) Tables 3.4a, b, and c of NEDC-32601-P-A provide the basis for the ((

)). Explain how the uncertainties in the lattice physics pin power data are accounted for in ((

)) Explain how the void and exposure dependency of the uncertainties of pin peaking factors is incorporated in the R-factor methodology. Specifically, explain how the exposure dependence of pin powers uncertainties are established if the infinite lattice pin power uncertainties are established using MCNP/TGBLA code to code benchmarking based in BOL or the standard GE MCNP/TGBLA comparisons with exposure is used.

43. The subcooling increases for the EPU conditions in comparison with operation at rated power and lower domains. Justify why the uncertainty due to core inlet temperature (Section 2.5 NEDC-32601P-A) would not change.

44. State if VYNPS EPU conditions would result in any bypass voiding due to the high bundle power conditions. The LPRM uncertainty increases with increasing void, ((

)) If any non-solid bypass voiding would occur during steady state, evaluate the LPRM and TIP uncertainties and justify why the current uncertainty based on zero bypass voiding remain applicable.

Consider an increase in the random noise. If bypass voiding does occur during transient events (e.g., RPT) and plant maneuvers in the offrated high power/low conditions, provide an evaluation of the impact of non-solid bypass voiding on the reliability and accuracy of the instrumentation.

45. Explain why the axial TIP RMS is not included in the calculation of the SLMCPR limit, when the SLMCPR limit calculation is non-adaptive. The staff understands that the core

((

))

Therefore, explain how the axial power distribution is accounted for in the (offline) calculation that establishes the SLMCPR value.

PART IV - Qualification of the Steady-State Neutronic Methods The footnote in Table 6-2 of Attachment 3 to Supplement No. 24, states, in part, that the purpose of the ((

)) For EPU conditions, no large transient tests or instability response tests are being performed. Therefore, comparing the steady state predictions of the maximum powered bundles operating conditions does not provide assurances of the accuracy of the coupled neutronic and thermal-hydraulic analyses supporting the EPU operation.

The following RAIs address GEs steady state neutronic methods and code systems (TGBLA/PANCEA).

46. Describe GEs standard approach for determining the cross-sections for operation at high void conditions (fit/interpolate/extrapolate). Discuss why the cross-sections are not directly generated for void fractions above 70%, using TGBLA. Describe any code-to-code comparisons that were performed in order to assess this method at high void fractions.

47. Provide plots of the isotopic concentrations and fission fractions of U-235, U-236, U-238, Pu-239, Pu-240, and Pu-241 as functions of burnup. Use lattices that are limiting in terms of enrichment and the number of hot pins and Gd concentration.

Present the isotopic concentration vs. exposure plots for depletion at 40%, 70%, and 90% void conditions. The objectives are to baseline potential changes due to spectral

hardening for operation at different void conditions and to determine both the accuracy of TGBLA and how TGBLAs accuracy changes with void fraction. Provide plots similar to the plots in Figures 3-8 and 3-9 of NEDE-20944-P for depletion at different void conditions and for different lattices.

48. With respect to the accuracy of the steady state neutronic methods for current fuel design (GE14) and operating strategies, demonstrate that possible variations in isotopic content, under applicable EPU conditions, have been accounted for including consideration of void reactivity coefficient.

PART V - Applicability of the Thermal-Hydraulic Models and Correlations and Significant Key Parameters In previous RAI SRXB-A-6(c), the staff requested that the licensee confirm that the assessment database and the assessed uncertainty of models used in all licensing codes that interface with and/or are used to simulate the response of VYNPS during steady state, transient or accident conditions remain valid and applicable for the EPU conditions. In response to the staffs RAI, the licensee opted, in part, to use the ((

)) The staff finds comparing the ((

)) useful, however this approach is not an adequate alternative to demonstrating that the applicable correlations and models that predict the plants response to the design bases events are applied within the ranges of the correlations or models or code systems are qualified.

Some qualitative assessments were provided under Applicability to transient methods, on pages 14 and 15 of Attachment 3 of the Supplement No. 24 response submittal. The following RAIs address the adequacy of the content of the response and asks for additional clarifications.

49. With respect to the GEXL correlation, for the VYNPS EPU conditions, state if any double-hump power shape is projected. Describe the methods and criteria used to determine that no additional SLMCPR penalty should apply. If any double-hump power shape is predicted irrespective of the corresponding bundle power level, justify why it is acceptable to predict the MCPR performance of a bundle using a correlation that was developed without the specific power shape, without adding a bias.

50. For the transient and LOCA events analyzed along the proposed operating domain statepoint, state if the power/flow ranges fall within the data base for which the GEXL correlation was developed. Give specific examples.

51. Provide an evaluation that demonstrates that the void reactivity coefficients are applicable and were developed for the ranges of core thermal-hydraulic conditions expected for the transient and accident conditions, including ATWS and SBO.

52. Demonstrate that the pressure drop measurement database include GE14 fuel designs and the test were performed to cover the ranges expected for operation at EPU conditions. Include in your response, the maximum range of bundle power-to-flow ratios and bundle mass flux over which the data were taken. With respect to bundle delta pressure validation, the information provided to date indicates an underprediction in delta pressure for high bundle power to flow ratios. How are the delta pressure uncertainties applied?

PART VI - Void-Quality Correlation Section 2.2 of Enclosure 3 to GE letter MFN 04-026 dated March 4, 2004, provides validation for the New Dix void-quality correlation, used for thermal-hydraulic modeling, for application above 90% void conditions. Enclosure 3 states that the correlation was developed using multi-rod data from CISE, GE, and ASEA-713 measurement programs. In addition, the correlation was verified by comparison to multi-rod data measurement in ASEA-813 and ASEA-513 experiments, in addition to a variety of results from simple test geometries. The following questions relate to the data supporting the void fraction correlation.

53. The document states that the ASEA-813 and ASEA-513 tests, which varied rod power distributions and side-to-side or in-out skew, were not included in the correlation development because of concerns over bias in the measurement. Enclosure 3 adds that there are many points of consistent overlap with ASEA-713 and the data serves well to validate the correlation developed using the most accurate data sources. Provide a tabulation or other means of justification that shows the data points supporting the validation of the correlation to the high void ranges. Identify the corresponding power profiles for the specific data set, the applicable test conditions /ranges (e.g., the bundle power/flow ratios.) and fuel designs and characteristics.

54. An EPU or a high-density plant can have an exit void fraction of ((

)) Do these void fraction predictions (( )) in the corresponding water density calculations?

55. The VYNPS response to RAI SRXB-A-6 states that the review of the steady state calculations at natural circulation indicates that the ((

)) The RAI response then justifies applying the ((

)) would not have significant impact on the thermal-hydraulic conditions and, therefore, the coupled reactivity feedback would not be affected.

As an Option 1D plant, VYNPS relies on APRM scram to provide SLMCPR protection for operation in the high powered/low flow zone of the power/flow map. For void fractions greater than (( )), issues that had not been addressed in the response are whether, (1) the SLMCPR would be protected before an ARPM scram occurs in order to meet GDC-12, and (2) would the reliability and effectiveness of the APRMs for stability protection be impacted by the high void conditions. Specifically, with 2RPT event conditions, ((

)), the instrument noise, and potentially the temperature, could increase, affecting the reliability of the APRMs relied upon for instability protection.

Right after a 2RPT event, the core thermal-hydraulic conditions may result in an SLMCPR value that is higher than for the cycle-specific SLMCPR value. In addition, the coupled neutronic and thermal-hydraulic response at the cited void ranges may change

depending on the response of the void reactivity coefficient with void fraction.

Therefore, the RAI response is inadequate.

Provide an evaluation that considers all impacts discussed above, including the any increases in the uncertainties of the ((

)) For any conclusions or assessment made, please provide the supporting bases.

56. Provide an evaluation of the impact on instrument random noise and reliability for operation at high power/low flow conditions during plant maneuvers and SLO operation.

57. In the response to RAI SRXB-A-6, the licensee states [t]he reactivity events are analyzed with the steady state tools and the results presented regarding steady-state methods in this response are directly applicable. There are some increases in power, which are significant but remain within the comparisons between the above plants for corresponding events. This RAI response does not provide sufficient detail.

a) State the specific reactivity event being referred to (e.g., control rod drop accident, rod withdrawal error).

b) State what steady state methods evaluation were described in the response to the RAI SRXB-A-6 response. The ((

)) would not serve to demonstrate that impact of local reactivity event on the fuel enthalpy and performance. Revise the RAI response and provide an explicit discussion of the event.

58. For the transients, LOCA and ATWS, during the initial condition, the axial power peaking and distributions and the accuracy of the steady state neutronic methods affect the plants response. State whether uncertainties are applied to the axial nodal powers, and the calculated void fraction. If uncertainties are not applied, please justify.

REFERENCES

1) Entergy letter (BVY 03-80) to NRC dated September 10, 2003, Vermont Yankee Nuclear Power Station, Technical Specification Proposed Change No. 263, Extended Power Uprate

2) Entergy letter (BVY 03-90) to NRC dated October 1, 2003, Vermont Yankee Nuclear Power Station, Technical Specification Proposed Change No. 263, Supplement No. 1, Extended Power Uprate -Technical Review Guidance

3) Entergy letter (BVY 03-95) to NRC dated October 28, 2003, Vermont Yankee Nuclear Power Station, Technical Specification Proposed Change No. 263, Supplement No. 2, Extended Power Uprate - Grid Impact Study

4) Entergy letter (BVY 03-98) to NRC dated October 28, 2003, Vermont Yankee Nuclear Power Station, Technical Specification Proposed Change No. 263, Supplement No. 3, Extended Power Uprate - Updated Information

5) Entergy letter (BVY 04-009) to NRC dated January 31, 2004, Vermont Yankee Nuclear Power Station, Technical Specification Proposed Change No. 263, Supplement No. 4, Extended Power Uprate - NRC Acceptance Review

6) Entergy letter (BVY 04-008) to NRC dated January 31, 2004, Vermont Yankee Nuclear Power Station, Technical Specification Proposed Change No. 263, Supplement No. 5, Extended Power Uprate - Response to Request for Additional Information

7) Entergy letter (BVY 04-025) to NRC dated March 4, 2004, Vermont Yankee Nuclear Power Station, Technical Specification Proposed Change No. 263, Supplement No. 6, Extended Power Uprate - Withholding Proprietary Information

8) Entergy letter (BVY 04-050) to NRC dated May 19, 2004, Vermont Yankee Nuclear Power Station, Technical Specification Proposed Change No. 263, Supplement No. 7, Extended Power Uprate - Confirmatory Results

9) Entergy letter (BVY 04-058) to NRC dated July 2, 2004, Vermont Yankee Nuclear Power Station, Technical Specification Proposed Change No. 263, Supplement No. 8, Extended Power Uprate - Response to Request for Additional Information

10) Entergy letter (BVY 04-071) to NRC dated July 27, 2004, Vermont Yankee Nuclear Power Station, Technical Specification Proposed Change No. 263, Supplement No. 9, Extended Power Uprate - Revised Containment Overpressure Envelope

11) Entergy letter (BVY 04-074) to NRC dated July 30, 2004, Vermont Yankee Nuclear Power Station, Technical Specification Proposed Change No. 263, Supplement No. 10, Extended Power Uprate - Response to Request for Additional Information

12) Entergy letter (BVY 04-081) to NRC dated August 12, 2004, Vermont Yankee Nuclear Power Station, Technical Specification Proposed Change No. 263, Supplement No. 11, Extended Power Uprate - Response to Request for Additional Information

13) Entergy letter (BVY 04-086) to NRC dated August 25, 2004, Vermont Yankee Nuclear Power Station, Technical Specification Proposed Change No. 263, Supplement No. 12, Extended Power Uprate - Revised Grid Impact Study

14) Entergy letter (BVY 04-097) to NRC dated September 14, 2004, Vermont Yankee Nuclear Power Station, Technical Specification Proposed Change No. 263, Supplement No. 13, Extended Power Uprate - Response to Steam Dryer Action Items

15) Entergy letter (BVY 04-098) to NRC dated September 15, 2004, Vermont Yankee Nuclear Power Station, Technical Specification Proposed Change No. 263, Supplement No. 14, Extended Power Uprate - Response to Request for Additional Information

16) Entergy letter (BVY 04-100) to NRC dated September 23, 2004, Vermont Yankee Nuclear Power Station, Technical Specification Proposed Change No. 263, Supplement No. 15, Extended Power Uprate - Response to Steam Dryer Action Item No. 2

17) Entergy letter (BVY 04-101) to NRC dated September 30, 2004, Vermont Yankee Nuclear Power Station, Technical Specification Proposed Change No. 263, Supplement No. 16, Extended Power Uprate - Additional Information Related to Request for Additional Information EMEB-B-5"

18) Entergy letter (BVY 04-107) to NRC dated September 30, 2004, Vermont Yankee Nuclear Power Station, Technical Specification Proposed Change No. 263, Supplement No. 17, Extended Power Uprate - Response to Request for Additional Information related to 10 CFR 50 Appendix R Timeline

19) Entergy letter (BVY 04-106) to NRC dated October 5, 2004, Vermont Yankee Nuclear Power Station, Technical Specification Proposed Change No. 263, Supplement No. 18, Extended Power Uprate - ECCS [emergency core cooling system] Pump Net Positive Suction Head Margin

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22) Entergy letter (BVY 04-129) to NRC dated December 9, 2004, Vermont Yankee Nuclear Power Station, Technical Specification Proposed Change No. 263, Supplement No. 21, Extended Power Uprate - Steam Dryer Power Ascension Testing

23) Entergy letter (BVY 04-131) to NRC dated December 8, 2004, Vermont Yankee Nuclear Power Station, Technical Specification Proposed Change No. 263, Supplement No. 22, Extended Power Uprate - 10 CFR 50 Appendix R Timeline Verification

24) Entergy letter (BVY 05-017) to NRC dated February 24, 2005, Vermont Yankee Nuclear Power Station, Technical Specification Proposed Change No. 263, Supplement No. 23, Extended Power Uprate - Response to Request for Additional Information

25) Entergy letter (BVY 05-024) to NRC dated March 10, 2005, Vermont Yankee Nuclear Power Station, Technical Specification Proposed Change No. 263, Supplement No. 24, Extended Power Uprate - Response to Request for Additional Information

26) Entergy letter (BVY 05-030) to NRC dated March 24, 2005, Vermont Yankee Nuclear Power Station, Technical Specification Proposed Change No. 263, Supplement No. 25, Extended Power Uprate - Station Blackout and Appendix R Analyses

27) Entergy letter (BVY 05-034) to NRC dated March 31, 2005, Vermont Yankee Nuclear Power Station, Technical Specification Proposed Change No. 263, Supplement No. 26, Extended Power Uprate - Steam Dryer Analyses and Monitoring

28) Entergy letter (BVY 05-038) to NRC dated April 5, 2005, Vermont Yankee Nuclear Power Station, Technical Specification Proposed Change No. 263, Supplement No. 27, Extended Power Uprate - Dryer Acoustic Load Methodology Benchmark

29) Entergy letter (BVY 05-046) to NRC dated April 22, 2005, Vermont Yankee Nuclear Power Station, Technical Specification Proposed Change No. 263, Supplement No. 28, Extended Power Uprate - Response to Request for Additional Information

30) Entergy letter (BVY 05-061) to NRC dated June 2, 2005, Vermont Yankee Nuclear Power Station, Technical Specification Proposed Change No. 263, Supplement No. 29, Extended Power Uprate - Computational Fluid Dynamics