ML080980229
| ML080980229 | |
| Person / Time | |
|---|---|
| Site: | Millstone, Kewaunee, Surry, North Anna  |
| Issue date: | 04/04/2008 |
| From: | Gerald Bichof Dominion Energy Kewaunee, Dominion Nuclear Connecticut, Virginia Electric & Power Co (VEPCO) |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| 08-0174, DOM-NAF-2, Rev. 0, Appendix C | |
| Download: ML080980229 (27) | |
Text
Dominion Resources Services, Inc.
~OOO Dominion Boulevard, Glen Allen, VA nll(,I)
W"b Address: www.dom.com April 4, 2008 U.S. Nuclear Regulatory Commission Attention: Document Control Desk One White Flint North 11555 Rockville Pike Rockville, MD 20852-2738 Serial No.
NL&OS/ETS Docket Nos.
License Nos.
08-0174 H
EiO-305 EiO-336/423 EiO-338/339 EiO-280/281 DPR-43 DPR-65/NPF-49 NPF-4/7 DPR-32/37 DOMINION ENERGY KEWAUNEE, INC.
DOMINION NUCLEAR CONNECTICUT, INC.
VIRGINIA ELECTRIC AND POWER COMPANY KEWAUNEE POWER STATION MILLSTONE POWER STATION UNITS 2 AND 3 NORTH ANNA AND SURRY POWER STATIONS UNITS 1 AND 2 REQUEST FOR APPROVAL OF APPENDIX C OF FLEET REPORT DOM-NAF-2 QUALIFICATION OF THE WESTINGHOUSE WRB-2M CHF CORRELATION IN THE DOMINION VIPRE-D COMPUTER CODE VIPRE is a core thermal-hydraulics computer code developed by EPRI and approved by the NRC, which is currently in wide use throughout the nuclear industry. VIPRE-D is the Dominion version of VIPRE, which has been enhanced by the addition of several vendor specific CHF correlations.
Dominion has validated VIPRE-D through extensive code benchmark calculations.
In addition, the accuracy of VIPRE-D has been demonstrated through comparisons with other NRC-approved methodologies.
In letters dated September 30, 2004 and January 13, 2005 (Serial Nos.04-606 and 05-020, respectively) Dominion submitted Topical Report DOM-NAF-2, "Reactor Core Thermal-Hydraulics Using the VIPRE-D Computer Code," and associated Appendices A and 8, as supplemented by letters dated June 30 and September 8, 2005 (Serial Nos.05-328 and 05-020A, respectively) for NRC review and approval.
NRC approval of Fleet Report DOM-NAF-2 including Appendixes A and 8 was obtained in a letter dated April 4, 2006 as revised by the NRC in a letter dated June 23, 2006.
Dominion provided the approved version of Fleet Report DOM-NAF-2-A to the NRC in a letter dated September 13,2006 (Serial No. 06-773A).
Continuing with the modular approach to Fleet Report DOM-NAF-2, and as discussed during the public meeting held between the NRC and Dominion on August 4, 2004, Dominion is now submitting Appendix C to this Fleet Report, "Qualification of the
Serial Number 08-0174 Docket Nos. 50-305/336/423/338/339/280/281 DOM-NAF2, Appendix C Transmittal Page 2 of 3 Westinghouse WRB-2M CHF Correlation in the Dominion VIPRE-D Computer Code," for NRC review and approval. Appendix C, which is provided in the Attachment to this letter, documents the qualification of the Westinghouse WRB-2M CHF Correlation with the VIPRE-D code and the associated code/correlation DNBR design limit.
Dominion requests the approval of the generic application of this appendix to DOM-NAF-2.
Plant specific applications of this fleet report, including applicable appendixes, will be submitted to the NRC for review and approval, in accordance with Section 2.1 of DOM-NAF-2.
If you have further questions or require additional information, please contact Mr. Thomas Shaub at (804) 273-2763.
Very truly yours, i~~6 Vice President - Nuclear Engineering Dominion Energy Kewaunee, Inc.
Dominion Nuclear Connecticut, Inc.
Virginia Electric and Power Company Attachment Commitments made in this letter: None cc:
U.S. Nuclear Regulatory Commission Region I 475 Allendale Road King of Prussia, Pennsylvania 19406-1415 U.S. Nuclear Regulatory Commission Region II Sam Nunn Atlanta Federal Center 61 Forsyth Street, SW Suite 23T85 Atlanta, Georgia 30303 U.S. Nuclear Regulatory Commission Region III 2443 Warrenville Road Suite 210 Lisle, Illinois 60532-4352
Serial Number 08-0174 Docket Nos. 50-305/336/4~~3/338/339/280/281 DOM-NAF2, Appendix C Transmittal Page 3 of 3 Ms. M. H. Chernoff NRC Project Manager U. S. Nuclear Regulatory Commission One White Flint North Mail Stop 0-8 H4A 11555 Rockville Pike Rockville, Maryland 20852-2738 Ms. J. D. Hughey NRC Project Manager Millstone Units 2 and 3 U. S. Nuclear Regulatory Commission, One White Flint North Mail Stop 0-8 G9A 11555 Rockville Pike Rockville, MD 20852-2738 Mr. R. A. Jervey NRC Project Manager U. S. Nuclear Regulatory Commission One White Flint North Mail Stop 0-8 G9A 11555 Rockville Pike Rockville, Maryland 20852 Mr. S. P. Lingam NRC Project Manager U. S. Nuclear Regulatory Commission One White Flint North Mail Stop 0-8 H4A 11555 Rockville Pike Rockville, Maryland 20852 NRC Senior Resident Inspector Kewaunee Power Station NRC Senior Resident Inspector Millstone Power Station NRC Senior Resident Inspector North Anna Power Station NRC Senior Resident Inspector Surry Power Station
Serial Number 08-0174 Docket Nos. 50-305/336/4~~3/338/339/280/281 DOM-NAF2, Appendix C Transmittal Attachment Appendix C to Fleet Report DOM-NAF-2 QUALIFICATION OF THE WESTINGHOUSE WRB-2M CHF CORRELATION IN THE DOMINION VIPRE-D COMPUTER CODE Dominion Energy Kewaunee, Inc.
(DEK)
Dominion Nuclear Connecticut, Inc.
(DNC)
Virginia Electric and Power Company (Dominion)
~...
- .Domlnlon'*
DOM-NAF-2, Rev. 0.0 APPENDIXC Qualification of the Westinghouse WRB*21V1 CHF Correlation in the Dominion VIPRE*D Computer Code NUCLEAR ANALYSIS AND FUEL DEPARTMENT DOMINION RICHMOND, VIRGINIA February, 2008 Prepared by:
Kurt F. Flaig Reviewed by:
Rosa M. Bilbao y Leon C. B. LaRoe Supervisor, Nuclear Safety Analysis Recommended for Approval:
~.~
Approved:
CLASSIFICATION/DISCLAIMER The data, information, analytical techniques, and conclusions in this report have been prepared solely for use by Dominion (the Company), and they may not be appropriate for use in situations other than those for which they are specifically prepared. The Company thereore makes no claim or warranty whatsoever, expressed or implied, as to their accuracy, usefulness, or applicability. In particular, THE COMPANY MAKES NO WARRANTY OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE, NOR SHALL ANY WARRANTY BE DEEMED TO ARISE FROM COURSE OF DEALING OR USAGE OR TRADE, with respect to this report or any of the data, information, analytical techniques, or conclusions in it. By making this report available, the Company does not authorize its use by others, and any such use is expressly forbidden except with the prior written approval of the Company. Any such written approval shall itself be deemed to incorporate the disclaimers of liability and disclaimers of warranties provided herein. In no event shall the Company be liable, under any legal theory whatsoever (whether contract, tort, warranty, or strict or absolute liability), for any property damage, mental or physical injury or death, loss of use of property, or other damage resulting from or arising out of the use, authorized or unauthorized, of this report.
ABSTRACT This appendix documents Dominion's qualification of the Westinghouse WRB*2M correlation with the VIPRE-D code. This qualification was performed against the same CHF experimental database used by Westinghouse to develop and license the correlation.
This appendix summarizes the data evaluations that were performed to qualify the VIPRE~DIWRB~2M code/correlation pair, and to develop the corresponding DNBR design limit.
DOM-NAF-2, Rev. 0.0, APPENDIX C C-2
TABLE OF CONTENTS CLASSIFICATION/DISCLAIMER..
C-2 ABSTRACT C-2 TABLE OF CONTENTS C-3 LIST OF TABLES..........................................................................................
C-4 LIST OF FIGURES........................................................................................
C-4 ACRONYMS AND ABBREVIATIONS................................................................
C-S C.1 PURPOSE............................................................................................
C-6 C.2 APPLICABILITY C-6 C.3 DESCRIPTION OF THE WESTINGHOUSE WRB-2M CHF CORRELATIOI\\I....
C-7 CA DESCRIPTION OF THE VIPRE-DIWRB-2M DATABASEAND TEST ASSEMBLIES...............................................
C-8 C.S VIPRE-DIWRB-2M RESULTS AND COMPARISON TO VIPRE-01..
c-s C.6 CONCLUSiONS.....
C-22 C.7 REFERENCES.....................................................
C-23 DOM-NAF-2, Rev. 0.0, APPENDIX C C-3
LIST OF*TABLES Table C.4-1: Summary of CHF Tests...
C-9 Table C.5-1: SummaryofVIPRE-D Results.........................................................
C-10 Table C.5-2: Statistical Analysis of WRB-2M Design Limit.....................................
C-11 Table C.5-3: Range of Validity for WRB-2M.........................
C-11 Table C.5-4: M/P CHF Performance by Independent Variable Grouping of the WRB-2M Database at 95% Confidence Level C-13 Table C.6-1: DNBR Limits forWRB-2M..............................................................
0*22 Table C.6-2: Range of Validity for VIPRE-DIWRB-2M..............
C-22 LIST OF FIGURES Figure C.5-1: Measured vs. Predicted CHF forVIPRE-DIWRB-2M Database.............
C-14 Figure C.5-2: M/P vs. Pressure for VIPRE-DIWRB-2M Database C-15 Figure C.5-3: M/P vs. Mass Velocity forVIPRE-DIWRB-2M Database......................
C-16 Figure C.5-4: M/P vs. Quality for VIPRE-DIWRB-2M Database...............................
C-17 Figure C.5-5: DNBR vs. Pressure for VIPRE-DIWRB-2M Database.........................
C-18 Figure C.5-6: DNBR vs. Mass Velocity for VIPRE-DIWRB-2M Database...................
C-19 Figure C.5-7: DNBR vs. Quality for VIPRE-DIWRB-2M Database......................
C-20 Figure C.5-8: VIPRE-DIWRB-2M Probability Density Function.............
C-21 DOM-NAF-2, Rev. 0.0, APPENDIX C C-4
ACRONYMS AND ABBREVIATIONS CHF DNB DNBR FLC HTRF IFM LPD M/P MIFM MPS MVG NMVG P/M PWR RFA USNRC Critical Heat Flux Departure from Nucleate Boiling Departure from Nucleate Boiling Ratio Form Loss Coefficient Heat Transfer Research Facility at Columbia University Intermediate Flow Mixer Low Pressure Drop Ratio of Measured-to-Predicted CHF Modified Intermediate Flow Mixer Millstone Power Station Mixing Vane Grid Non-Mixing Vane Grid Ratio of Predicted-to-Measured CHF (equivalent to DNBR)
Pressurized Water Reactor Robust Fuel Assembly US Nuclear Regulatory Commission DOM-NAF-2, Rev. 0.0, APPENDIX C C-5
C.1 PURPOSE Dominion currently uses the Westinghouse 17x17 Robust Fuel Assembly (RFA) fuel product at Millstone Power Station (MPS), Unit 3. The thermal-hydraulic analysis of this We:stinghouse fuel product requires the use of the Westinghouse WRB-2M CHF correlation (Reference C1). In fact, the Westinghouse WRB-2M CHF correlation has been approved by the USNRC for use with the 17x17 RFA fuel design with or without the Intermediate Flow Mixer (IFM) grids (Reference C1).
To be licensed for use, a critical heat flux (CHF) correlation must be tested aqainst experimental data that span the anticipated range of conditions over which the correlation will be applied.
Furthermore, the population statistics of the database must be used to establish a departure from nucleate boiling ratio (DNBR) design limit such that the probability of avoiding departure from nucleate boiling (DNB) will be at least 95% at a 95% confidence level.
This addendum documents Dominion's qualification of the WRB-2M correlation with the VIPRE-D code. This qualification was performed against the data from the Columbia University Heat Transfer Research facility (HTRF) for the Modified Vantage 5H and Modified Vantage 5H/IFM fuel types (Reference C1). This is the same set of the Columbia-EPRI CHF database used by Westinghouse in the qualification of the WRB-2M correlation with the VIPRE-01 code (Reference C1). This addendum summarizes the data evaluations that were performed to qualify the VIPRE-DIWRB-2M code/correlation pair, and to develop the corresponding DNBR design limits for the correlation.
C.2 APPLICABILITY Dominion intends to use the VIPRE-DIWRB-2M code/correlation for Westinghollse 17x17 RFA fuel products, with or without modified intermediate flow mixers (MIFM) in a PWR reactor.
When evaluating this type of fuel outside of the range of validity of the WRB-2M CHF correlation, Dominion intends to use the VIPRE-DIW-3 code/correlation pair. W-3 is one of the CHF correlations contained in the USNRC approved generic version of VIPRE-D1 (References C3 and C4), and it has already been approved for use with the VIPRE-D code (Reference C5).
The intended VIPRE-DIWRB-2M applications discussed in this addendum are consistent with the generic intended applications listed in the main body of this report (Section 2.0 in Reference C5).
Also, more specifically, Dominion intends to use VIPRE-DIWRB-2M to analyze the transients delineated in Table 2.1-1 in Section 2.0 of the main body of this report (Reference C5). The qualification of the WRB-2M correlation with the VIPRE D code has been performed following the modeling guidelines described in Section 4 of this report (Reference C5).
This Addendum is submitted to the USNRC for review and approval in order to meet the USNRC's requirement #2 listed in the VIPRE-01 SER, as outlined in Section 2.2 in the main body of this report (Reference C5).
DOM-NAF-2, Rev. 0.0, APPENDIX C C-6
C.3 DESCRIPTION OF THE WESTINGHOUSE WRB-:!M CHF CORRELATION In pressurized water reactor (PWR) cores, the energy generated inside the fuel pellets leaves the fuel rods at their surface in the form of heat flux, which is removed by the reactor coolant system flow. The normal heat transfer regime in this configuration is nucleate boiling, which is very efficient. However, as the capacity of the coolant to accept heat from the fuel rod surface degrades, a continuous layer of steam (a film) starts to blanket the tube" This heat transfer regime, termed film boiling, is less efficient than nucleate boiling and can result in significant increases of the fuel rod temperature for the same heat flux. Since the increase in temperature may lead to the failure of the fuel rod cladding, PWRs are designed to operate in the nucleate boiling regime and protection against operation in film boiling must be provided.
The heat flux at which the steam film starts to form is called CHF or the point of DNB. For design purposes, the DNBR is used as an indicator of the margin to DNB. The DNBR is the ratio of the predicted CHF to the actual local heat flux under a given set of conditions. Thus, DNBR is a measure of the thermal margin to film boiling and its associated high temperatures.
The greater the DNBR value (above 1.0), the greater the thermal margin.
The CHF cannot be predicted from first principles, so it is empirically correlated as a function of the local thermal-hydraulic conditions, the geometry, and the power distribution measured in the experiments.
Since a CHF correlation is an analytical fit to experimental elata, it has an associated uncertainty, which is quantified in a DNBR design limit. A calculated DNBR value greater than this design limit provides assurance that there is at least a 95% probability at the 95% confidence level that a departure from nucleate boiling will not occur.
Correlations to predict the occurrence of CHF have undergone evolutions as nuclear fuel designs have changed. Westinghouse developed the WRB-1 CHF correlation fer the prediction of DNB for Westinghouse fuel assemblies with mixing vane grids (MVGs). Subsequently, Westinghouse developed the WRB-2 CHF correlation for the prediction of DNB in Westinghouse fuel assemblies with MVGs and intermediate flow mixing grid:; (IFMs). More recently, Westinghouse has modified their nuclear fuel design to reduce fuel rod mechanical wear and to further improve thermal/hydraUlic performance.
The new fuel design includes modified low pressure drop (LPD) mixing vane grids and modified intermediate flow mixing grids (MIFMs). This new fuel design is called the modified Vantage 5H and Modified Vantage 5HIIFM depending on whether the MIFMs have been included. (When the design includes the MIFM grids, it has also been referred to as the Robust Fuel Assembly (RFA>>. CHF tests with the modified grids were conducted at the Columbia HTRF with and without control rod guide thimbles and with and without MIFM grids. Although the new data was successfully correlated by Westinghouse using the WRB-2 CHF correlation, a better correlation, the WRB-2M CHF correlation (a modification of the WRB-2 CHF correlation), was obtained by DOM-NAF-2, Rev. 0.0, APPENDIX C C-7
incorporation of a multiplier 'M' (Reference C1). The sensitivity of WRB-2M to other parameters, such as various power shapes is very similar to WRB-2. Thus, WRB-2M is applicable for 17x17 fuel with 0.374 inch OD rods, and Modified LPD grids with or without MIFM's.
The range of applicable parameters is given in Table C.5-3. The WRB-2M correlation has been approved by the NRC (Reference C1).
The WRB-2M DNB correlation was developed from test bundles simulating the RFA fuel design with only a cosine axial power shape. As part of a scoping study for new grid designs, DNB tests were performed with the uniform axial power shape at the Columbia Unlversity test loop.
Although the grid designs were not the same, the mixing vanes of the test bundles were similar to the RFA fuel design. When compared to the data from those tests, the WRB*,2M measured-to-predicted (M/P) CHF average ratio was lower than 1.0.
No significant trend in M/P was observed with respect to key parameters such as local flow rate, local equilibrium quality, and pressure. Based on this comparison with the test results, Westinghouse decided to adjust the DNB predictions for the WRB-2M DNB correlation. The adjustment factor does not constitute a change in the methodology as described in the licensing basis. The NRC staff has reviewed the adjustment factor and its consequences and found it acceptable (Reference C6).
The W-3 correlation is used when conditions are outside the range of the WRB-2M DNB correlation.
Specifically, the W-3 correlation is applied to the lower portion of the fuel assemblies in the rod withdrawal from subcritical event because of the bottom peaked axial power distribution assumed, and in the steam line break event because of the low pressures involved. The W-3 correlation with a correlation limit of 1.30 is used below the fuel assembly first mixing vane grid for the rod withdrawal from subcritical event. For the steam line break event, the W-3 correlation is used with a correlation limit of 1.45 in the pressure range of 500 to 1000 psia and 1.30 for pressures above 1000 psia (Reference C8). The Westinghouse W-3 CHF correlation is described on page 10 in Reference C7.
C.4 DESCRIPTION OF THE VIPRE-DIWRB-2M DJ~TABASE AND TEST ASSEMBLIES The WRB-2M CHF correlation was developed from CHF data obtained at the Columbia University HTRF using full-scale, electrically heated rod bundle test sections (Reference C1).
The Dominion qualification of WRB-2M in VIPRE-D was performed against the same test data from the Columbia-EPRI CHF database for Westinghouse 17x17 fuel. Dominion used the CHF experimental data used by Westinghouse to develop the WRB-2M correlation.
No data point was deleted or excluded.
The HTRF test assemblies had a 5x5 geometry, thus the test assemblies used by Dominion to qualify the VIPRE-DIWRB-2M code/correlation pair have a 5x5 geometry. These 5x5 test bundles have essentially a 17x17 subchannel geometry (Reference C1). Table C.4-1 provides a summary of the key information about each test.
DOM-NAF-2, Rev. 0.0, APPENDIX C C-8
Table C.4-1: Summary of CHF Tests PIN 001 HEATED AXIAL HEAT GUIDE TUBE MIFM NUMBER TEST MATRIX FLUX SHAPE 00 LENGTH grids?
OF TeSTS
[inches]
[inches]
A-1 5x5 Non-Uniform 0.374/-
168 Yes B6 A-2 5x5 Non-Uniform 0.374/
168 Yes "77 0.474 A-3 5x5 Non-Uniform 0.374/
168 No
0 0.474 A-4 5x5 Non-Uniform 0.374/-
168 No -.
c.s VIPRE*DIWRB*2M RESULTS AND COMPARISON TO VIPRE*01 Reference C1 describes the mathematical model for each separate test section by providing the bundle and cell geometry, the rod radial peaking values, the rod axial flux shapes, the types, axial locations and form losses associated to the spacer grids, as well as the thermocouple locations.
Reference C1 also provides the data for each CHF observation within a test, including power, flow, inlet temperature, pressure and CHFaxiallocation.
Each test section was modeled for analysis with the VIPRE-D thermal-hydraulic computer code as a full assembly model following the modeling methodology discussed in Section 4 in the main body of this report. For each set of bundle data, VIPRE-D produces the local thermal-hydraulic conditions (mass velocity, thermodynamic quality, heat flux, etc.) at every axial node along the heated length of the test section. The ratio of measured-to-predicted CHF (M/P) is the variable that is normally used to evaluate the thermal-hydraulic performance of a code/correlation pair.
The measured CHF is the local heat flux at a given location, while the predicted CHF is calculated by the code using the WRB-2M CHF correlation. The ratio of these two values provides the M/P ratio, which is the inverse of the DNB ratio. M/P ratios are frequently used to validate CHF correlations instead of DNB ratios, because their distribution is usually a normal distribution, which simplifies their manipulation and statistical analysis.
This section summarizes the VIPRE-D results and the associated significant statistics. This section also shows the variation of the M/P ratio with each independent variable to demonstrate that there are no biases in the data. Finally, it provides the VIPRE-D overall statistics for the WRB-2M tests and generates the DNBR design limit for the WRB-2M CHF correlation with VIPRE-D.
DOM-NAF-2, Rev. 0.0, APPENDIXC C-9
The WRB-2M correlation was developed by Westinghouse by correlating the CHF experimental results obtained in the tests as described in Reference C1. Westinghouse also used these test data to calculate a DNBR design limit of 1.14 for the WRB-2M correlation (Heference C1).
Dominion used these experimental
- data, as described in section CA, to develop the VIPRE-DIWRB-2M DNBR limit. Table C.5-1 summarizes the relevant statistics for each test, and calculates the aggregate statistics for the entire set of data.
Tests Average SrDeV Max Min A-1 66 1.0178 0.0789 1.2114 0.8287 A-2 77 0.9834 0.0538 1.1017 0.8614 A-3 70 1.0144 0.0559 1.1444 0.8954 A-4 28 0.9731 0.0490 1.1002 0.8688 Thimble 147 0.9982 0.0568 1.1444 0.8614 Typical 94 1.0045 0.0740 1.2114 0.8287 WithMIFM 143 0.9993 0.0685 1.2114 0.8287 Without MIFM 98 1.0026 0.0570 1.1444 0.8688 All Results 241 1.0006 0.0640 1.2114 0.8287 Table C.5-1: Summary of VIPRE*D Results Test Number of I M/P Ratio I M/P Ratio I M/P Ratio I M/P Ratio I One-sided tolerance theory (Reference C2) is used for the calculation of the VIPRE-DIWRB-2M DNBR design limit. This theory allows the calculation of a DNBR limit so that, for a DNBR equal to the design limit, DNB will be avoided with 95% probability at a 95% confidence level.
First, it is necessary to verify that the overall distribution for the M/P ratios is a normal distribution, because all the statistical techniques used below assume that the original data distribution is normal. To evaluate if the distribution is normal, the D' normality test was applied.
A value of D' equal to 1047.04 was obtained for the VIPRE-DIWRB-2M database. This D J value is within the range of acceptability for 241 data points with a 95% confidence level {1038.60 to 1066.75)l11. Thus, it is concluded that the M/P distribution for the VIPRE-DIWRB-2M database is indeed normal. Based on the results listed in Table C.5-1, the deterministic DNBR design limit can be calculated as:
DNBRL =
1.0 M I P - K N,C,P. (YM I P
[C.5.1]
where M/P
= average measured to predicted CHF ratio O'M/P
= standard deviation of the measured to predicted CHF ratios of the database KN,c,p = one-sided tolerance factor based on N degrees of freedom, C confidence level, and P portion of the population protected. This number can be obtained from Table 1.4.4 of Reference C2.
1 FromTable 5 in Reference C9 0' Lower Limit (241) [P =0.025] =1038.60 D' Upper Limit (241) [P =0.975] =1066.75 DOM-NAF-2, Rev.0.0, APPENDIXC C-10
Normally, the number of degrees of freedom would be the total number of delta minus one.
However, because Westinghouse used these experimental data to correlate the 6 constants that appear in the WRB-2M correlation, the total number of degrees of freedom must be corrected to account for this. In addition, the standard deviation of the database needs to be corrected accordingly to account for this reduced number of degrees of freedom:
N =n-1-6 aN =(JMfP' [ (n -1) IN] Yo
[C.5.2]
Then, the DNBR design limit for the VIPRE-D and the WRB-2M correlation can be calculated as shown in Table C.5-2.
Table C.S-2: Statistical Analysis of WRB*2M Design Limit Number of data n
241 Degrees of freedom N
=n-1-6 234 Average M/P M/P 1.0006 Standard Deviation O"M/P 0.0640 Corrected Standard Deviation O"N
=O"M/P' [(n-1)/N]Y.
0.0648 Owens Factor K(N,0.95,0.95) 1.8170 WRB*2M Design limit DNBRL
= 1 I (M/P - K(N,O.95,O.95). O"N) 1.1327 Even though this is not a large database, correcting for the number of constants in the WRB-2M correlation has no significant effect, and it is more conservative to make the correction.
The calculated DNBR limit results in a value of 1.14.
This is the same number reported by Westinghouse in Reference C1 and has been approved by the NRC.
Table C.5-3 summarizes the ranges of validity for the VIPRE-DIWRB-2M correlation. These ranges, are identical to those submitted by Westinghouse and already approved by the NRC (Reference C1).
Table C.S-3: Range of Validity for WRB*2M VIPRE-D Pressure [psia]
1495 to 2425 Mass Velocity [Mlbm/hr-ft21 0.97 to 3.1 Thermodynamic Quality at CHF
-0.1 to 0.29 Figures C.5-1 through C.5-4 display the performance of the M/P ratio, and its distributions as a function of the pressure, mass velocity and quality. The objective of these plots is to show that DOM-NAF-2, Rev. 0.0, APPENDIX C C-11
there are no biases in the M/P ratio distribution, and that the performance of the WRB-2M correlation is independent of the three independent variables of interest. The plots show a mostly uniform scatter of the data and no obvious trends or slopes. These plots also show that all the tests in the WRB-2M database are within 3.5 standard deviations from the average.
Figures C.5-5 through C.5-7 display the performance of the P/M ratio (i.e., the DNBR) against the major independent variables for the WRB-2M database. These plots also include the DNBR design limit line. It can be seen that only six data points (2.49% of the database~1 are above the DNBR design limit, and that these data in excess of the limit are distributed over the variable ranges tested.
A more formal determination of the lack of bias of the average M/P ratio can be done using the analysis of variance test (ANaVA) shown in Table C.5-4. ANaVA tests are normally applied to highly controlled situations, but they can be somewhat useful in CHF testing and correlation.
However, the ANOVA test cannot be used as the sole measure of the performance of a CHF correlation, but it would indicate an extremely bad mismatch (with a very large F statistic). The variables analyzed were pressure, quality, mass velocity and test cell type. The ANaVA results for VIPRE-DIWRB-2M slightly exceed the critical values of F for pressure and quality, but other comparisons prove the hypothesis that all the groups belong to the same distribution; i.e., that there is no bias of the results regarding the analyzed variables.
Furthermore, when looking at the figures in this section, there does not appear to be any trend or bias in the data. Therefore, it can be concluded that the WRB-2M M/P ratio database is independent or the pressure, quality, and mass velocity.
DOM-NAF-2, Rev. 0.0, APPENDIX C C-12
Table C.5-4: MJPCHF Performance by Independent Variable Groupin" of the WRB-2M Database at 95% Confidence Level Grouping Number Average Standard Maximum Minimum of Data M/P Deviation M/P Mrp Analysis by Pressures Below 1575 psla 29 0.9831 0.0610 1.1153 0.8146 1575 - 1850 psla 67 0.9967 0.0666 1.1327 0.81514 1850 - 2250 psla 74 1.0210 0.0680 1.2114 0.9058 Above 2250 psia 71 0.9903 0.0534 1.1002 0.8287 Fdistribution =4.0812 FCrilical(3,237) =2.6427 Analysis by Qualities Below 5%
42 1.0107 0.0521 1.1193 0.8688 5% to 10%
71 1.0126 0.0581 1.1302 0.8B62 10% to 15%
66 1.0051 0.0633 1.1744 0.8794 15% to 20%
46 0.9718 0.0628 1.1444 0.8287 Above 20%
16 0.9858 0.0961 1.2114 0.8336 Fdistribution =3.6650 FcriticaI(4,236) =2.4099 Analysis by Mass Velocities Below 1.25 Mlbm/hr-ffo!
32 0.9915 0.0645 1.1444 0.8688 1.25 - 1.75 Mlbm/hr-ft£ 75 1.0055 0.0642 1.1302 0.8614 1.75 - 2.25 Mlbm/hr-ft£ 74 1.0023 0.0602 1.1744 0.8287 2.25 - 2.75 Mlbm/hr-ft;l 51 0.9911 0.0637 1.1264 0.8336 2.75 - 3.25 Mlbm/hr-ft;l 9
1.0323 0.0879 1.2114 0.9063 Fdistribution =1.1176 Fcritical(4,236) =2.4099 Analvsis by Geometry Tvpe With MIFM Grids 143 0.9993 0.0685 1.2114 0.1:287 Without MIFM Grids 98 1.0026 0.0571 1.1444 0.1:,688 Fdistribution =0.1580 Fcritical(1,239) =3.8807 Analysis by Thimble vs. Typical Thimble 147 0.9982 0.0568 1.1444 0.~'614 Typical 94 1.0045 0.0740 1.2114 0.~'287 Fdislributlon =0.5546 FCrilical(1,239) =3.8807 All Data WRB-2M All Data 241 1.0006 0.0640 1.2114 0.0287 DOM-NAF-2, Rev. 0.0, APPENDIX C C-13
Figure C.5*1: Measured vs. Predicted CHF for VIPRE*DIWRB-2M Database
+------1I------I---....J 1.000 0.900 0.800 0.700 0.400 0.500 0.600 Measured CHF (MBtu/hr-ft2) 0.300 0.200 i/
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IXI:E-0.600 L&.
- J:
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0.500 ts:ce 00400 D-0.300 0.200 0.100 DOM-NAF-2, Rev. 0.0, APPENDIX C C-14
Figure C.5~2: M/P vs. Pressure for VIPRE-DIWRB-2M Database
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f 1.3 1.2 1.1 0.9 0.8 0.7 0.0 500.0 1000.0 1500.0 Pressure (psia) 2000.0 2500.0 3000.0 DOM-NAF-2, Rev. 0.0, APPENDIX C C-15
Figure C.5-3: M/P vs. Mass Velocity for VIPRE-DIWRB-2M Database 1.3 1.2 1.1 0.9 0.8
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3.500 3.000 2.500 1.500 2.000 Mass Velocity (Mlbm/hr-ft2) 1.000 0.500 0.7 J------------------+------l-------+------+------
0.000 DOM-NAF-2, Rev. 0.0, APPENDIX C C-16
Figure C.5-4: MfP vs. Quality for VIPRE-DIWRB-2M Database 1.3 1.2 1.1 D.i 1
0.9 0.8
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-0.050 0.000 0.050 0.100 Quality 0.150 0.200 0.250 0.300 0.350 DOM-NAF-2, Rev. 0.0, APPENDIX C C-17
Figure C.5-5: DNBR vs. Pressure for VIPRE*DIWRB*2M Database 1.3 1.2 1.1
- !a::
II l:t::m zc 0.9 0.8 07 VIPRElWRB*2M DeIsign Limit=1.14
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0.0 500.0 1000.0 1500.0 Pressure (psia) 2000.0 2500.0 3000.0 DOM-NAF-2, Rev. 0.0, APPENDIX C C-18
Figure C.S-6: DNBR vs. Mass Velocity for VIPRE-DIWRB-2M Database 1.3,-------..,-------r------,------..,-------,----.----,----------,
1.2 -jn n
VIPREIWRB-2M esign Limit =1.1*
1.1 +
+
0.9 i
0.8 3.500 3.000 2.500 1.500 2.000 Mass Velocity (Mlbm/hr-ft2) 1.000 0.500 0.7 Ji--------------------------.-1c----------------------
0.000 DOM-NAF-2, Rev. 0.0, APPENDIX C C-19
Figure C.5-7: DNBR vs. Quality for VIPRE-D/WRB-2M Database 1.3 ~----r------r----.,..-----,------r-----r------r------.,-----r----.......,
VIPREIWRa-2M Design limit = 1.14
..,....... ~....
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II 0:::mzc 0.8 +-----+----+-----+----+------+----+-------+----+--------+-----1 I
-0.100 I
-0.050 I
0.000 I
0.050 I
0.100 Quality I
0.150 I
0.200 0.250 0.300 0.350 DOM-NAF-2, Rev. 0.0, APPENDIX C C-20
The 241 data points of the VIPRE-DIWRB-2M M/P distribution calculated by Dominion were used to create the empirical probability density function. These data points were distributed among 21 equal bins that covered the entire range of M/P in the VIPRE D/WRB-.2M distribution, and the frequency of data in each bin was determined.
The resulting empirical probability density functions for the VIPRE-DIWRB-2M distribution were then compared with the probability density function of a normal distribution of mean 1.0006 and standard deviation 0.0640, which is the mean and standard deviation for the VIPRE-DIWRB-2M distribution calculated in Section C.5 above.
Figure C.5-8 displays the resulting empirical probability density function for the VIPRE-DIWRB-2M M/P distribution, and compares it with the probability density function of the normal distribution of mean "1.0006 and standard deviation 0.0640.
Figure C.5-8: VIPRE*DIWRB*2M Probability Density Function 2.00%
0.00%
§ of) 0 of) 8 0
8 0
- 5 0
0 0
0 N
N
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ci ci ci ci ci ci ci 0
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M/P 18.00%.---------------------------l 16.00%
12.00%
6.00%
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ue CD 5-8.00%
l!!
u, 14.00%
4.00%
IIl!!!!!lVIPRE-DIWRB-2M Data NORMAL(1.0006. 0.0640) I DOM-NAF-2, Rev. 0.0, APPENDIX C C-21
C.G CONCLUSIONS The WRB-2M correlation has been qualified with Dominion's VIPRE-D computer code. Table C.6-1 summarizes the DNBR design limits for VIPRE-DIWRB-2M that yields a 95% non-DNB probability at a 95% confidence level. The limit of 1.14 from VIPRE-D is the same limit as found with Westinghouse's version of VIPRE (Reference C1). The Westinghouse WRB-2M CHF correlation has been approved by the USNRC for use with Westinghouse 17x17 with 0.374 inch 00 rods, and Modified LPD grids with or without MIFM's in a PWR reactor.
Table C.6-1: DNBR Limits for WRB-2M Dominion Westinghouse VIPRE-D VIPRE-01 DNBR limit 1.14 1.14 Table C.6-2 summarizes the applicability and the ranges of validity for VIPHE-DIWRB-2M, which are the same as those on page 4-2 of Reference C1.
Table C.6-2: Range of Validity for VIPRE-DIWRB-2M Pressure 1440 to 2425
[psia]
Mass Velocity 0.97 to 3.1
[Mlbm/hr-:ft2]
Thermodynamic
-0.1 to 0.29 Quality at CHF DOM-NAF-2, Rev. 0.0, APPENDIX C C-22
C.7 REFERENCES C1.Technical Report, WCAP-15025-P-A, "Modified WRB-2 Correlation, WRB-2M, for predicting Critical Heat Flux in 17x17 Rod Bundles with Modified LPO Mixing Vane Grids," L.D. Smith, et ai, April 1999.
C2.Technical Report, "Tables for Normal Tolerance Limits, Sampling Plans and Screening," R.
E. Odeh and D. B. Owen, 1980.
C3.Letter from C. E. Rossi (NRC) to J. A Blaisdell (UGRA Executive Committee), "Acceptance for Referencing of Licensing Topical Report, EPRI NP-2511-CCM, 'VIPRE-()1: A Thermal-Hydraulic Analysis Code for Reactor Cores,' Volumes 1, 2, 3 and 4," May 1, 1986.
C4.Letter from A.
C. Thadani (NRC) to Y.
Y.
Yung (VIPRE-01 Maintenance Group),
"Acceptance for Referencing of the Modified Licensing Topical Report, EPRII\\lP-2511-CCM, Revision 3, 'VIPRE-01: A Thermal Hydraulic Analysis Code for Reactor Cores,' (TAC No.
M79498)," October 30, 1993.
C5.Fleet Report, DOM-NAF-2-A, including Appendixes A and B, "Reactor Core Thermal-Hydraulics Using the VIPRE-D Computer Code," Rosa M. Bilbao y Leon, August 2006.
C6.Letter from D. S. Collins (NRC) to J. A Gresham (Westinghouse), "Modified WRB-2 Correlation WRB-2M for Predicting Critical Heat Flux in 17X17 Rod Bundles with Modified LPO Mixing Vane Grids," February 3, 2006.
C7.Technical Report, "Boiling Crisis and Critical Heat Flux," TI0-25887, 1972.
C8.Letter from AC.
Thadani (NRC) to W.J.
Johnson (Westinghouse),
"Acceptance for Referencing of Licensing Topical Report, WCAP-9226-P, Reactor Core: Response to Excessive Secondary Steam Releases." 1989.
eg. Technical Report, "Assessment of the Assumption of Normality (employing individual observed values)," American National Standards Institute, ANSI N15.15.19711*.
DOM-NAF-2, Rev. 0.0, APPENDIX C C-23