View source for ET 11-0010, Response to Request for Additional Information Regarding License Amendment Request to Revise Technical Specification 5.6.5, Core Operating Limits Report for Large Break Loss-of-Coolant Accident Analysis Methodology

{{Adams
| number = ML11312A137
| issue date = 10/19/2011
| title = Response to Request for Additional Information Regarding License Amendment Request to Revise Technical Specification 5.6.5, Core Operating Limits Report for Large Break Loss-of-Coolant Accident Analysis Methodology
| author name = Clemens R
| author affiliation = Wolf Creek Nuclear Operating Corp
| addressee name = 
| addressee affiliation = NRC/Document Control Desk, NRC/NRR
| docket = 05000482
| license number = 
| contact person = 
| case reference number = ET 11-0010
| document type = Letter type:ET
| page count = 34
| project = 
| stage = Response to RAI
}}

=Text=
{{#Wiki_filter:W LF CREEK 'NUCLEAR OPERATING CORPORATION October 19, 2011 Richard P. Clemens Vice President Engineering ET 11-0010 U. S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555

==Reference:==
: 1) Letter ET 10-0025, dated November 4, 2010, from T. J. Garrett, WCNOC, to USNRC
: 2) Electronic Mail dated September 22, 2011, from J. R. Hall, USNRC to D. M. Hooper, WCNOC

==Subject:==
Docket No. 50-482: Response to Request for Additional Information Regarding License Amendment Request to Revise Technical Specification 5.6.5, "CORE OPERATING LIMITS REPORT (COLR)," for Large Break Loss-of-Coolant Accident Analysis Methodology Gentlemen:
Reference 1 provided Wolf Creek Nuclear Operating Corporation's (WCNOC) application to revise Technical Specification (TS) 5.6.5, "CORE OPERATING LIMITS REPORT (COLR)," to replace the existing large break loss-of-coolant accident (LOCA) analysis methodology (WCAP-10266-P-A) with a best estimate large break LOCA analysis based on WCAP-16009-P-A, "Realistic Large Break LOCA Evaluation Methodology Using Automated Statistical Treatment of Uncertainty Method (ASTRUM)." Reference 2 provided a request for additional information related to the application.
Attachment I provides a response to Question 5 of the request for additional information.
Enclosure I contains Attachment 1A of LTR-LIS-11-541 that provides Westinghouse Electric Company proprietary responses to Questions 1 through 4 and 6 through 10. Enclosure II contains Attachment 1B of LTR-LIS-11-541 that provides Westinghouse Electric Company non-proprietary responses to Questions 1 through 4 and 6 through 10. Enclosure III contains the affidavit for withholding proprietary information.
The additional information does not expand the scope of the application as originally noticed, and does not impact the conclusions of the Nuclear Regulatory Commission (NRC) staffs original proposed no significant hazards consideration determination as published in the Federal Register (75 FR 81673).
P.O. Box 411/ Burlington, KS 66839 / Phone: (620) 364-8831 An Equal Opportunity Employer M/F/HCNET

ET 11-0010 Page 2 of 3 In accordance with 10 CFR 50.91, a copy of this submittal is being provided to the designated Kansas State official.
Enclosure I provides the proprietary Westinghouse Electric Company LLC Attachment 1A of LTR-LIS-1 1-541, "Suggested Responses to NRC RAIs for Wolf Creek BELOCA Project."
Enclosure II provides the non-proprietary Westinghouse Electric Company LLC Attachment 1B of LTR-LIS-11-541, "Suggested Responses to NRC RAIs for Wolf Creek BELOCA Project." As Enclosure I contains information proprietary to Westinghouse Electric Company LLC, it is supported by an affidavit signed by Westinghouse Electric Company LLC, the owner of the information. The affidavit sets forth the basis on which the information may be withheld from public disclosure by the Commission and addresses with specificity the considerations listed in paragraph (b)(4) of 10 CFR 2.390 of the Commission's regulations. Accordingly, it is respectfully requested that the information, which is proprietary to Westinghouse, be withheld from public disclosure in accordance with 2.390 of the Commission's regulations. This affidavit, along with Westinghouse authorization letter, CAW-1 1-3269, "Application for Withholding Proprietary Information from Public Disclosure," is contained in Enclosure Ill.
This letter contains no commitments. If you have any questions concerning this matter, please contact me at (620) 364-4084, or Mr. Gautam Sen at (620) 364-4175.
Sincerely, cRihard P. Clemens RPC/rlt Attachment I      Response to Request for Additional Information Enclosure    I   Attachment 1A of LTR-LIS-11-541, "Suggested Responses to NRC RAIs for Wolf Creek BELOCA Project" II Attachment 1B of LTR-LIS-1 1-541, "Suggested Responses to NRC RAIs for Wolf Creek BELOCA Project" III CAW-1 1-3269, "Application for Withholding Proprietary Information from Public Disclosure" cc:   E. E. Collins (NRC), w/a, w/e T. A. Conley (KDHE), w/a, w/e II J. R. Hall (NRC), w/a, w/e G. B. Miller (NRC), w/a, w/e Senior Resident Inspector (NRC), w/a, w/e

ET 11-0010 Page 3 of 3 STATE OF KANSAS                    )
COUNTY OF COFFEY                   )
Richard P. Clemens, of lawful age, being first duly sworn upon oath says that he is Vice President Engineering of Wolf Creek Nuclear Operating Corporation; that he has read the foregoing document and knows the contents thereof; that he has executed the same for and on behalf of said Corporation with full power and authority to do so; and that the facts therein stated are true and correct to the best of his knowledge, information and belief.
plemens lent Engineering SUBSCRIBED and sworn to before me this H-z            day of  "c--ero(         ,2011.
GAYLE SHEPHEARD a      Notarj Public - State of Kansas Mv Appt. Ey~prrcs r72'*2 4 Expiration Date  - 7/. q1112- -

Attachment I to ET 11-0010 Page 1 of 2 Response to Request for Additional Information Reference 1 provided Wolf Creek Nuclear Operating Corporation's (WCNOC) application to revise Technical Specification (TS) 5.6.5, "CORE OPERATING LIMITS REPORT (COLR)," to replace the existing large break loss-of-coolant accident (LOCA) analysis methodology (WCAP-10266-P-A) with a best estimate large break LOCA analysis based on WCAP-16009-P-A, "Realistic Large Break LOCA Evaluation Methodology Using Automated Statistical Treatment of Uncertainty Method (ASTRUM)." Reference 2 provided a request for additional information related to the application.       Enclosure I contains Attachment 1A of LTR-LIS-1 1-541 that provides Westinghouse Electric Company proprietary responses to Questions 1 through 4 and 6 through 10. The response to Question 5 is provided below. The specific NRC question is provided in italics.
: 5. Please include the date of approval for WCAP-16009-P-A in the proposed TS 5.6.5.b.7 (Revision 0, January 2005, as approved by the NRC staff in a Safety Evaluation dated November 5, 2004). Please also specify which parameters listed in TS 5.6.5.a are supported by TS 5.6.5.b. 7.
Response: As discussed in Attachment I of Reference 1 (page 2 of 30), listing only the NRC-approved methodology by topical report number and title is consistent with Amendment No. 144 (adoption of Technical Specification Task Force (TSTF) traveler TSTF-363). Additionally, in a letter from the NRC to the TSTF (Reference 3) the NRC indicated that the NRC staff does not intend to backfit licensees that have these travelers (TSTF-363, TSTF-408 or TSTF-419) already in their TS. As such, inclusion of the date of approval for WCAP-16009-P-A in TS 5.6.5.b.7 is not necessary.
Amendment No. 123 (Reference 4) approved the deletion of the parameters listed in TS 5.6.5.a that were supported by the methodologies listed in TS 5.6.5.b based on NUREG-1431, "Standard Technical Specifications Westinghouse Plants," Revision 2. As such, specifying the parameters listed in TS 5.6.5.a that are supported by the TS 5.6.5.b.7 methodology is not necessary.

==References:==
: 1. WCNOC letter ET 10-0025, "Application To Revise Technical Specification 5.6.5, "CORE OPERATING LIMITS REPORT (COLR)," for Large Break Loss-of-Coolant Accident Analysis Methodology," November 4, 2010.
: 2. Electronic mail from J. R. Hall, USNRC to D. M. Hooper, WCNOC, "Request for Additional information - License Amendment Request for Wolf Creek Generating Station (TAC NO.
ME4996)," September 22, 2011.
: 3. NRC letter from J. R. Jolicoeur to TSTF, "IMPLEMENTATION OF TRAVELERS TSTF-363, REVISION 0, "REVISE TOPICAL REPORT REFERENCES IN ITS 5.6.5, COLR
[CORE OPERATING LIMITS REPORT]," TSTF-408, REVISION 1, "RELOCATION OF LTOP      [LOW      TEMPERATURE         OVERPRESSURE         PROTECTION]       ENABLE TEMPERATURE AND PORV [POWER-OPERATED RELIEF VALVE] LIFT SETTING TO THE PTLR [PRESSURE-TEMPERATURE LIMITS REPORT]," AND TSTF-419, REVISION 0, "REVISE PTLR DEFINITION AND REFERENCES IN ISTS [IMPROVED STANDARD TECHNICAL SPECIFICATION] 5.6.6, RCS [REACTOR COOLANT SYSTEM] PTLR"," August 4, 2011, ADAMS Accession No. ML110660285.

Attachment I to ET 11-0010 Page 2 of 2
: 4. License Amendment No. 123, "Conversion to Improved Technical Specifications for Wolf Creek Generating Station - Amendment No. 123 to Facility Operating License No. NPF-42 (TAC NO. M98738)," March 31, 1999.

Enclosure II to ET 11-0010 Enclosure 11 (20 pages)
Westinghouse Electric Company LLC, Attachment lB of LTR-LIS-11-541, "Suggested Responses to NRC RAIs for Wolf Creek BELOCA Project" (Non-Proprietary)

Westinghouse Non-Proprietary Class 3 Attachment 1B to LTR-LIS-11-541 (Page 1 of 20)
Suggested Responses to NRC RAIs for Wolf Creek BELOCA Project Preface:
The list of NRC questions is given in the NRC letter that is electronically attached to LTR-LIS-1 1-545.
Note that RAI #5 is being addressed by Wolf Creek Nuclear Operating Corporation (WCNOC) and is not addressed herein.
The Licensing Amendment Request (LAR) Document being NRC reviewed is Wolf Creek Letter ET 10-0025, Docket No. 50-482, License No. NPF-42, November 4, 2010 (NRC ADAMS Accession #
ML103200209).
                                 &#xa9;2011Westinghouse Electric Company LLC All Rights Reserved

Westinghouse Non-Proprietary Class 3 Attachment 1B to LTR-LIS-11-541 (Page 2 of 20)
RAI #1:
Please provide a description and the results of the evaluation done against the conditions and limitations stated in the staff s safety evaluation report (SER) on the ASTRUM methodology in WCAP-16009-P-A with respect to the Wolf Creek plant-specific adaptation of the ASTRUM methodology. Also, identify any deviations and describe their impact on safe plant operation Response #1:
The Wolf Creek ASTRUM BELOCA analysis was performed in accordance with the applicability limits and usage conditions defined in Section 13-3 of WCAP-16009-P-A as applicable to the ASTRUM methodology, without implementing any plant-specific modeling and analysis adaptations. According to the discussion of the conditions and limitations in Section 4.0 of the ASTRUM SER, Section 13-3 of WCAP-16009-P-A was found to acceptably disposition each of the identified conditions and limitations related to WCOBRA/TRAC and the Code Qualification Document (CQD) uncertainty approach.

Westinghouse Non-Proprietary Class 3 Attachment 1B to LTR-LIS-11-541 (Page 3 of 20)
RAI #2:
With respect to the analysis employed in the plant-specific adaptation of the ASTRUM evaluation model, please provide the following:
: a. A clarification to show that the plant-specific adaption of the ASTRUM evaluation model for WCGS is still within the approved limitations and conditions stated in the NRC staff's SER for WCAP- 16009-P-A;
: b. the plant nodalization scheme for WCGS;
: c. the results from the 4 circumferential node analysis; and
: d. a clarification and basis for the apparent increase in the number of circumferential noding stacks in the downcomer region from 4 to 12. Based on the staff's experience in reviewing similar applications, it appears that the licensee may have increased the number of circumferential noding stacks.
Response #2:
: a. The response to RAI #1 addresses the clarification desired for part (a) of RAI #2.
: b. The plant nodalization figures are enclosed and include the vessel noding diagram (vertical and horizontal views) and the loop noding diagram.
: c. As indicated in the vessel noding diagram in Figure 2-1, four circumferential noding stacks were modeled for Wolf Creek, which is consistent with the approved methodology.
: d. As indicated in the vessel noding diagram in Figure 2-1, four circumferential noding stacks were modeled for Wolf Creek, which is consistent with the approved methodology.

Westinghouse Non-Proprietary Class 3 Attachment 1B to LTR-LIS-11-541 (Page 4 of 20) 494.93                      _-
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Figure 2-1: Wolf Creek Vessel Model Noding Diagram (Vertical View)

Westinghouse Non-Proprietary Class 3 Attachment 1B to LTR-LIS-11-541 (Page 5 of 20)
SECTION 1: LOWER HEAD R   Channel ID #
O   Gap ID #
SECTION 2: LOWER PLENUM                               SECTION 3: CORE Figure 2-2: Wolf Creek Vessel Sections 1 to 3 (Horizontal View)

Westinghouse Non-Proprietary Class 3 Attachment 1B to LTR-LIS-11-541 (Page 6 of 20)
SECTION 4: CCFL REGION
[: Channel ID#
O Gap ID#
Loop 3 w/Pressurizer Loop 4 SECTION 5: UPPER PLENUM BELOW NOZZLES                    SECTION 6: NOZZLE REGION Figure 2-3: Wolf Creek Vessel Sections 4 to 6 (Horizontal View)

Westinghouse Non-Proprietary Class 3 Attachment 1B to LTR-LIS-11-541 (Page 7 of 20)
SECTION 7: UPPER PLENUM ABOVE NOZZLES                        SECTION 8: UPPER HEAD
[  Channel ID #
O   GapID#
SECTION 9: UPPER HEAD                            SECTION 10: UPPER HEAD Figure 2-4: Wolf Creek Vessel Sections 7 to 10 (Horizontal View)

Westinghouse Non-Proprietary Class 3 Attachment 1B to LTR-LIS-11-541 (Page 8 of 20)
PRIZER SGBREAK     SGFILL      36SGFILL                        SGBREAK Loop 3              37 37 32 36836                             4680 4      47 47            Loop 4 STGEN                                    1STGEN 32 31           39                        41    Q IFILL                                                                           .3FFLL 73     85 61TAC                      I 31          51T   41'5             E   3  4 6AV3 2 SITES                                                                                SITE 8        8IVAVE VA87E 64                                                      18 XLPIPE Loop 2                                                                                      Loop 1 SGFILL                     SGFILL       SGBREAK             (Broken Loop)
Figure 2-5: Wolf Creek WCOBRA/TRAC Model Loop Layout

Westinghouse Non-Proprietary Class 3 Attachment 1B to LTR-LIS-11-541 (Page 9 of 20)
RAI #3:
With respect to the peak cladding temperatures (PCTs) shown in Figure 1 of the LAR, please discuss the reasons why the PCTs corresponding to the double-ended guillotine break are significantly higher than those resulting from the split break for breaks around same effective break sizes (in the range of CDxAbreak/ACL between 1.7 and 2.1).
Response #3:
Figure 3-1 shows the non-IFBA PCT as a function of effective break area (CDXAbreak/ACL) between 1.7 and 2.1. Figure 3-1 indicates that there is generally little PCT difference between double-ended guillotine (DEG) breaks and split breaks for breaks in this effective break area range. The highest PCTs in this range correspond to DEG breaks; however, there are many more DEG breaks in this range than split breaks. It is also noted that there are many other sampled attributes that contribute to the PCT result in addition to the effective break area.

Westinghouse Non-Proprietary Class 3 Attachment 1B to LTR-LIS-11-541 (Page 10 of 20)
[]
PCT  Epe vs. (CD PC_DEC A) (A 124 Cases)
PCT  _ SPL            0              0            0 PCT       DEG C     [deg F]
0              0            0 PCT       SPL IT    [deg F]
c     -.
I UUU 0
M 1500-
[]                  []            M]
M                    []                                UK U []
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        *UU 1.7                   1.8                        1.9                       2           2.1 CD
* Abreak/ACL sumpost,x X2009/06/23 11:16:06.27 2083575543 Figure 3-1: HOTSPOT PCT vs. Effective Break Area Scatter Plot (non-IFBA)
(CDXAbreak/ACL between 1.7 and 2.1)

Westinghouse Non-Proprietary Class 3 Attachment 1B to LTR-LIS-11-541 (Page 11 of 20)
RAI #4:
Please explain the physical meaning and cause of the negative values for the hot assembly vapor flow rate between 10 and 30 seconds after the break as shown in Figure 8 in the LAR.
Response #4:
A notable aspect of blowdown is the core flow reversal behavior. The break is so large that the fluid quickly overcomes its initial steady state forward momentum near the cold leg break. This flow reversal progresses away from the break and into the core starting at the bottom of the core and proceeding upward. The plant-specific resistance network in the vessel (including the fuel assembly element) and the Reactor Coolant System (RCS) loops is critical in determining the timing of the flow reversal. It is not uncommon for even the top of the core to eventually experience flow reversal. The cited plot shows the vapor flow rate at node 10 in the core, which corresponds to approximately 8' up the fuel assembly. This is fairly typical of flow reversal behavior in other 4-loop plants (though, as stated, the details are plant-specific). The hot assembly vapor flow rate plot is typically interesting as it often is a strong predictor of blowdown PCT trends since there is virtually no liquid present in the core shortly after the onset of blowdown, leaving vapor heat transfer as the dominant clad heat removal mechanism.

Westinghouse Non-Proprietary Class 3 Attachment 1B to LTR-LIS-11-541 (Page 12 of 20)
RAI #6:
Please provide the uncertainty applied to the decay heat curve for the limiting large break LOCA.
Response #6:
The decay heat multiplier corresponds to "Decay Heat" in ASTRUM Topical (WCAP-16009-P-A) Table 1-10, [                       ]apc with mean (p') and standard deviation (o) applied as a function of burnup and enrichment according to the ANSI/ANS 5.1-1979 standard. Note that the ANSI/ANS 5.1-1979 standard is acceptable for calculating fission product decay heat per NRC Regulatory Guide 1.157.
The decay heat model is described in ASTRUM Topical Sections 8-2 and 8-4, while Section 8-7 provides information on the associated uncertainties provided by the ANSI/ANS 5.1-1979 standard. The relative contribution to the decay heat from U-235, Pu-239, and U-238 is a function of burnup and enrichment (see Figures 8-1 to 8-3 of WCAP-16009-P-A). As a result, the uncertainty contribution from the decay groups (shown in Table 8-14 of WCAP-16009-P-A) yields an overall uncertainty that varies with burnup and enrichment.
Application of the uncertainty is through the multiple decay groups shown in ASTRUM Topical Table 8-14.
In summary, the code includes all of the individual nominal and uncertainty elements for each decay heat contributor as given in the ANSI/ANS 5.1-1979 standard (as a function of burnup and enrichment), and applies the same sampled sigma to each contributor at each point in time, with the total decay heat being the sum of all contributors. Therefore, there is not a single time-independent percentage multiplier applied to the nominal value at all points in time.
Note that the as-sampled decay heat multiplier for the PCT-limiting case corresponds to -0.13y for Wolf Creek (decay heat below nominal).

Westinghouse Non-Proprietary Class 3 Attachment 1B to LTR-LIS-11-541 (Page 13 of 20)
RAI #7:
The Idlechik Handbook provides a recommended expression for pressure loss coefficients along a curved channel. Please explain the basis for the assumptions used in the calculation for the k-factor and why the Idlechik Handbook expression was not used in that calculation. Also, provide the values of the lateral k-factors used for the downcomer lateral flow paths for the plant.
RAI #8:
Please provide the method used to compute the azimuthal lateral k-factors and the values used in the plant calculations. The staff notes that the Idlechik Handbook reference for calculating k-factors presents a method to compute k-factors in annuli of various radii. Please provide the results of a k-factor study for the lateral flow paths in the downcomer, if one was performed.
Responses #7 and #8:
Since these two RAIs are related to each other, they are addressed in a single response.
The total lateral k-factor is made up of two components; the loss due to the curvature in the downcomer (form loss) and the frictional loss. The lateral k-factor resulting from application of Diagram 6-2 from Idelchik (Reference 7-1) is determined, and then compared to the lateral k-factor for a 4-loop Pressurized Water Reactor (PWR). A number of boundary conditions are necessary for this calculation.
: 1) [
                                    ]a.C Also note that the geometry used for the PWR calculation was taken from D. C. Cook Unit 2, which has a similar design as Wolf Creek.
The k-factor from the frictional losses and losses due to the curvature of the downcomer from WCOBRA/TRAC for a 4-loop PWR are presented in Figure 7-1 as a function of Reynolds number. Since the azimuthal flow rate in the downcomer and the fluid properties change significantly throughout a Large Break LOCA transient, it is desirable to compare the losses over a range of Reynolds numbers. [
1' is discussed later in this response.

Westinghouse Non-Proprietary Class 3 Attachment 1B to LTR-LIS-11-541 (Page 14 of 20)
The total loss calculated from Idelchik (including both frictional and curvature losses) is presented in Figure 7-2 as a function of Reynolds number. It is noted that the loss is higher for low Reynolds numbers in the laminar flow regime, and decreases as the regime transitions to turbulent flow.
The total loss calculated from WCOBRA/TRAC for a 4-loop PWR, the total loss calculated from Idelchik, and the difference between the two losses are presented in Figure 7-3. [
                                           ] ac The effect of the lower lateral k-factor on mixing in the downcomer is discussed in the response to RAI
#10.
Reference(s) 7-1)   Idelchik, I. E., 1994, "Handbook of Hydraulic Resistance,"  3 rd Edition, CRC Press, Inc.

Westinghouse Non-Proprietary Class 3 Attachment 1B to LTR-LIS-11-541 (Page 15 of 20) ax Figure 7-1: K-Factor for Frictional and Curvature Losses from WCOBRA/TRAC

Westinghouse Non-Proprietary Class 3 Attachment 1B to LTR-LIS-11-541 (Page 16 of 20) 3 2.5 2
L 1.5 1
0.5 0
0 10000    20000    30000   40000     50000      60000 70000   80000  90000 100000 Reynolds Number (-)
Figure 7-2: Total K-Factor for Losses Calculated from Idelchik

Westinghouse Non-Proprietary Class 3 Attachment 1B to LTR-LIS-11-541 (Page 17 of 20) a~c Figure 7-3: Comparison of Losses from WCOBRA/TRAC and Idelchik

Westinghouse Non-Proprietary Class 3 Attachment 1B to LTR-LIS-11-541 (Page 18 of 20)
RAI #9:
Please describe the azimuthal nodalization and results from the approved best-estimate WCOBRA/TRAC model. Also provide the results of other nodalization studies applied to the azimuthal detail in the downcomer (other than the four and 12 azimuthal node studies). Please also show the impact of time step on the PCT for the worst case downcomer boiling calculation.
Response #9:
The results of the CCTF Test 62, UPTF Test 6, and UPTF Test 25A simulations for the approved CQD methodology are described in Sections 14-2-6-1, 14-4-5 through 14-4-9, and 14-4-11 of the CQD (Reference 9-1), respectively. The results of these same simulations with three downcomer channel stacks per loop (twelve total stacks) are described in Reference 9-2. These test simulations were not executed with any other number of downcomer channel stacks to support the revised downcomer noding in the PWR.
                                                                    ]a,c As indicated in the vessel noding diagram in Figure 2-1, four circumferential noding stacks were modeled for Wolf Creek, which is consistent with the approved methodology. As such, analysis results from models with different numbers of downcomer channel stacks are not available.
Generically, the effects of time step sizes are quantified in detail in Reference 9-1 for both experimental facility and plant modeling applications as follows (Note that time step size, as referred to in this response, refers to DTMAX, the maximum allowable time step as defined by the user. The time step actually employed by the code is automatically adjusted to a value between DTMAX and DTMIN according to other convergence criteria as discussed in Section 2-7 of the CQD; also note that the cross-references below all refer to Reference 9-1):
     -   Section 2-7 and its subsections provide a detailed description of the methods for convergence criteria, time step size control, and numerical stability.
     -   Section 19-1-2 examines the effects of time step size on the experimental simulations used for code validation including the G-1 Blowdown Test 152, two FLECHT-SEASET forced reflood tests, CCTF Run 62, and LOFT L2-5. As stated on Page 19-1-6,
                        ]a.c
     -   Section 22-5 presents the effects of time step size on the demonstration analyses for three PWR plants, with results presented in Table 22-5-3. Based on time step sensitivity observed during the blowdown, refill, and reflood periods, the time step strategy shown in Table 22-5-4 was selected.
     -   The response to RAI4-11 explains the procedure followed in Section 22-5 to arrive at a fixed range of allowable time step sizes (as shown in Table 22-5-4) in the interest of minimizing variability.

Westinghouse Non-Proprietary Class 3 Attachment 1B to LTR-LIS-11-541 (Page 19 of 20)
     -   The response to RAI4-50a explains the definition of convergence in terms of the magnitude of change in PCT with further reduction in time step. The scoping studies of Section 22-5 are repeated using the MOD7A version of the code for the North Anna plant as documented in Section 22-5-5. Again, sufficiently small variation (less than the uncertainty in the code bias) is observed when using time steps within the recommended range.
In summary, the "code resolution" in terms of PCT variability with time step changes has been shown to be of low significance relative to the total calculation uncertainty. This conclusion has been reached in a general sense by exercising the code for both experimental facilities and full-scale PWR simulations of multiple types (3- and 4-loop), and is therefore applicable to plant analysis applications such as Wolf Creek.
The Wolf Creek plant-specific effect of time step size on PCT for the worst-case downcomer boiling is not available, since no plant-specific time step size study was performed for the Wolf Creek ASTRUM analysis (see below for more detail). Note however, that the time step sizes used in the Wolf Creek ASTRUM analysis meet the Best-Estimate Large Break LOCA Evaluation Model requirements provided in Table 22-5-4 of Volume 4 of the CQD (Reference 9-1).
LAR Figure 2 indicates that the PCT for the limiting case occurs at about 60 seconds after break. LAR Figure 10 shows that downcomer boiling begins at about 150 seconds after break as evidenced by a drop in lower plenum collapsed liquid level after initial refill. The PCT rise at this time is minimal and does not approach the maximum PCT. Therefore, it is concluded that downcomer boiling does not impact the results of the Wolf Creek analysis. Therefore, time step studies during downcomer boiling are not expected to affect the analysis results as the cladding temperatures are well below the maximum value during downcomer boiling as previously discussed.
Reference(s) 9-1)   Bajorek, S. M., et al., March 1998, "Code Qualification Document for Best Estimate LOCA Analysis," Volume I Revision 2, and Volumes 2 through 5, Revision 1, WCAP-12945-P-A (Proprietary).
9-2) Letter from Jensen, J. N. to USNRC, December 27, 2007, "License Amendment Request Regarding Large Break Loss-of-Coolant Accident Analysis Methodology," Enclosure 3, AEP:NRC:7565-01.

Westinghouse Non-Proprietary Class 3 Attachment 1B to LTR-LIS-11-541 (Page 20 of 20)
RAI #10:
Please provide a detailed analysis of the impact of the lateral k-factor values on PCT during downcomer boiling following a large-break LOCA. The NRC staff completed a sensitivity study on downcomer boiling and the effect of lateral k-factor on this phenomenon. The case with zero lateral k-factor in the downcomer cross flow paths joining the azimuthal cells resulted in a 400 degree (*F) reduction in peak clad temperature. This was due to the maximization of mixing between the downcomer azimuthal cells which severely limited downcomer boiling. The cold water entering the downcomer during the long-term cooling phase readily mixed into the adjacent downcomer volumes and thereby reduced boiling, the extent of core uncovery and resulting clad temperatures. ECCS bypass and liquid sweep-out that dominate the very early portion of the event (the first 100-200 seconds) do not prevail during the longer term when the downcomer fills with liquid and vapor velocities are no longer high enough to entrain and sweep out the injected liquid.
Response #10:
Responses to similar questions recently transmitted to the Nuclear Regulatory Commission (NRC) for D.C. Cook Unit 2 and North Anna Units 1 and 2 are generally also applicable to Wolf Creek. Information regarding how the lateral k-factors are modeled in the downcomer and comparisons to Idelchik calculations on a plant specific basis are provided therein.
                 ]Pc  Based on the physical nature of this argument, similar conclusions can be drawn for Wolf Creek.
Specific to the Wolf Creek analysis, LAR Figure 2 indicates that the PCT for the limiting case occurs at about 60 seconds after break. LAR Figure 10 shows that downcomer boiling begins at about 100 seconds and becomes significant at 150 seconds after break as evidenced by a drop in lower plenum collapsed liquid level after initial refill. The PCT rise at this time is minimal and does not approach the maximum PCT. Therefore, it is concluded that downcomer boiling does not impact the results of the Wolf Creek analysis.

Enclosure III to ET 11-0010 Enclosure III (7 pages)
Westinghouse Electric Company LLC, CAW-1 1-3269, "Application for Withholding Proprietary Information from Public Disclosure"

()Westinghuse                                                      Westinghouse  Electric Company Nuclear Services 1000 Westinghouse Drive Cranberry Township, Pennsylvania 16066 USA U.S. Nuclear Regulatory Commission                                 Direct tel: (412) 374-4643 Document Control Desk                                             Direct fax: (724) 720-0754 11555 Rockville Pike                                                 e-mail: greshaja@westinghouse.com Rockville, MD 20852                                               Proj letter: SAP-11-96 CAW-11-3269 October 13, 2011 APPLICATION FOR WITHHOLDING PROPRIETARY INFORMATION FROM PUBLIC DISCLOSURE

==Subject:==
LTR-LIS- 11-541, Attachment IA, "Suggested Responses to NRC RAIs for Wolf Creek BELOCA Project," TAC No. ME4996 (Proprietary)
The proprietary information for which withholding is being requested in the above-referenced report is further identified in Affidavit CAW-1 1-3269 signed by the owner of the proprietary information, Westinghouse Electric Company LLC. The affidavit, which accompanies this letter, sets forth the basis on which the information may be withheld from public disclosure by the Commission and addresses with specificity the considerations listed in paragraph (b)(4) of 10 CFR Section 2.390 of the Commission's regulations.
Accordingly, this letter authorizes the utilization of the accompanying affidavit by Wolf Creek Nuclear Operating Corporation (WCNOC).
Correspondence with respect to the proprietary aspects of the application for withholding or the Westinghouse affidavit should reference this letter, CAW-1 1-3269, and should be addressed to J. A. Gresham, Manager, Regulatory Compliance, Westinghouse Electric Company LLC, Suite 428, 1000 Westinghouse Drive, Cranberry Township, Pennsylvania 16066.
Very truly yours, JR. A Gresham, Manager Regulatory Compliance Enclosures

CAW-l 1-3269 AFFIDAVIT COMMONWEALTH OF PENNSYLVANIA:
ss COUNTY OF BUTLER:
Before me, the undersigned authority, personally appeared J. A. Gresham, who, being by me duly sworn according to law, deposes and says that he is authorized, to execute this Affidavit on behalf of Westinghouse Electric Company LLC (Westinghouse), and that the averments of fact set forth in this Affidavit are true and correct to the best of his knowledge, information, and belief:
A. Gresham, Manager Regulatory Compliance Sworn to and subscribed before me this 13th day of October 2011 Notary lblic COMMONWEALTH OF PENNSYLVANIA NOTARIAL SEAL Renee Giampole, Notary Public Penn Township, Westmoreland County My Commission Expires September 25, 2013

2                                      CAW-1 1-3269 (1) I am Manager, Regulatory Compliance, in Nuclear Services, Westinghouse Electric Company LLC (Westinghouse), and as such, I have been specifically delegated the function of reviewing the-proprietary information sought to be withheld from public disclosure in connection with nuclear power plant licensing and rule making proceedings, and am authorized to apply for its withholding on behalf of Westinghouse.
(2) I am making this Affidavit in conformance with the provisions of 10 CFR Section 2.390 of the Commission's regulations and in conjunction with the Westinghouse Application for Withholding Proprietary Information from Public Disclosure accompanying this Affidavit.
(3) I have personal knowledge of the criteria and procedures utilized by Westinghouse in designating information as a trade secret, privileged or as confidential commercial or financial information.
(4) Pursuant to the provisions of paragraph (b)(4) of Section 2.390 of the Commission's regulations, the following is furnished for consideration by the Commission in determining whether the information sought to be withheld from public disclosure should be withheld.
(i)       The information sought to be withheld from public disclosure is owned and has been held in confidence by Westinghouse.
(ii)     The information is of a type customarily held in confidence by Westinghouse and not customarily disclosed to the public. Westinghouse has a rational basis for determining the types of information customarily held in confidence by it and, in that connection, utilizes a system to determine when and whether to hold certain types of information in confidence. The application of that system and the substance of that system constitutes Westinghouse policy and provides the rational basis required.
Under that system, information is held in confidence if it falls in one or more of several types, the release of which might result in the loss of an existing or potential competitive advantage, as follows:
(a)      The information reveals the distinguishing aspects of a process (or component, structure, tool, method, etc.) where prevention of its use by any of

3                                       CAW-] 1-3269 Westinghouse's competitors without license from Westinghouse constitutes a competitive economic advantage over other companies.
(b)     It consists of supporting data, including test data, relative to a process (or component, structure, tool, method, etc.), the application of which data secures a competitive economic advantage, e.g., by optimization or improved marketability.
(c)     Its use by a competitor would reduce his expenditure of resources or improve his competitive position in the design, manufacture, shipment, installation, assurance of quality, or licensing a similar product.
(d)     It reveals cost or price information, production capacities, budget levels, or commercial strategies of Westinghouse, its customers or suppliers.
(e)     It reveals aspects of past, present, or future Westinghouse or customer funded development plans and programs of potential commercial value to Westinghouse.
(f)    It contains patentable ideas, for which patent protection may be desirable.
There are sound policy reasons behind the Westinghouse system which include the following:
(a)     The use of such information by Westinghouse gives Westinghouse a competitive advantage over its competitors. It is, therefore, withheld from disclosure to protect the Westinghouse competitive position.
(b)     It is information that is marketable in many ways. The extent to which such information is available to competitors diminishes the Westinghouse ability to sell products and services involving the use of the information.
(c)     Use by our competitor would put Westinghouse at a competitive disadvantage by reducing his expenditure of resources at our expense.

4                                     CAW-1 1-3269 (d)     Each component of proprietary information pertinent to a particular competitive advantage is potentially as valuable as the total competitive advantage. If competitors acquire components of proprietary information, any one component may be the key to the entire puzzle, thereby depriving Westinghouse of a competitive advantage.
(e)     Unrestricted disclosure would jeopardize the position of prominence of Westinghouse in the world market, and thereby give a market advantage to the competition of those countries.
(f)     The Westinghouse capacity to invest corporate assets in research and development depends upon the success in obtaining and maintaining a competitive advantage.
(iii)  The information is being transmitted to the Commission in confidence and, under the provisions of 10 CFR Section 2.3 90, it is to be received in confidence by the Commission.
(iv)  The information sought to be protected is not available in public sources or available information has not been previously employed in the same original manner or method to the best of our knowledge and belief.
(v)   The proprietary information sought to be withheld in this submittal is that which is appropriately marked in "Suggested Responses to NRC RAls for Wolf Creek BELOCA Project (Proprietary), for submittal to the Commission, being transmitted by Wolf Creek Nuclear Operating Corporation letter and Application for Withholding Proprietary Information from Public Disclosure, to the Document Control Desk. The proprietary information as submitted by Westinghouse is that associated with Westinghouse's request for NRC review and may be used only for that purpose.
This information is part of that which will enable Westinghouse to:
(a)      Obtain NRC review of Westinghouse responses to Requests for Additional Information to support the licensing of the Wolf Creek BELOCA analysis.

5                                      CAW-1 1-3269 Further this information has substantial commercial value as follows:
(a)     Westinghouse plans to sell the use of this information to its customers for purposes of licensing the Wolf Creek BELOCA analysis.
(b)     Westinghouse can sell support and defense of the use of the BELOCA criteria.
(c)      The information requested to be withheld reveals the distinguishing aspects of a methodology which was developed by Westinghouse.
Public disclosure of this proprietary information is likely to cause substantial harm to the competitive position of Westinghouse because it would enhance the ability of competitors to provide similar calculations and licensing defense services for commercial power reactors without commensurate expenses. Also, public disclosure of the information would enable others to use the information to meet NRC requirements for licensing documentation without purchasing the right to use the information.
The development of the technology described in part by the information is the result of applying the results of many years of experience in an intensive Westinghouse effort and the expenditure of a considerable sum of money.
In order for competitors of Westinghouse to duplicate this information, similar technical programs would have to be performed and a significant manpower effort, having the requisite talent and experience, would have to be expended.
Further the deponent sayeth not.

Proprietary Information Notice Transmitted herewith are proprietary and/or non-proprietary versions of documents furnished to the NRC in connection with requests for generic and/or plant-specific review and approval.
In order to conform to the requirements of 10 CFR 2.390 of the Commission's regulations concerning the protection of proprietary information so submitted to the NRC, the information which is proprietary in the proprietary versions is contained within brackets, and where the proprietary information has been deleted in the non-proprietary versions, only the brackets remain (the information that was contained within the brackets in the proprietary versions having been deleted). The justification for claiming the information so designated as proprietary is indicated in both versions by means of lower case letters (a) through (f) located as a superscript immediately following the brackets enclosing each item of information being identified as proprietary or in the margin opposite such information. These lower case letters refer to the types of information Westinghouse customarily holds in confidence identified in Sections (4)(ii)(a) through (4)(ii)(f) of the affidavit accompanying this transmittal pursuant to 10 CFR 2.390(b)(1).
Copyright Notice The reports transmitted herewith each bear a Westinghouse copyright notice. The NRC is permitted to make the number of copies of the information contained in these reports which are necessary for its internal use in connection with generic and plant-specific reviews and approvals as well as the issuance, denial, amendment, transfer, renewal, modification, suspension, revocation, or violation of a license, permit, order, or regulation subject to the requirements of 10 CFR 2.390 regarding restrictions on public disclosure to the extent such information has been identified as proprietary by Westinghouse, copyright protection notwithstanding. With respect to the non-proprietary versions of these reports, the NRC is permitted to make the number of copies beyond .those necessary for its internal use which are necessary in order to have one copy available for public viewing in the appropriate docket files in the public document room in Washington, DC and in local public document rooms as may be required by NRC regulations if the number of copies submitted is insufficient for this purpose. Copies made by the NRC must include the copyright notice in all instances and the proprietary notice if the original was identified as proprietary.}}