ML17338A718

DNBR Safety Limit for Cobra Iiic Analysis.

ML17338A718
Person / Time
Site:	Turkey Point
Issue date:	03/31/1979
From:	Irani A, Wilson W, Wyrick R FLORIDA POWER & LIGHT CO.
To:
Shared Package
ML17338A717	List: ML17338A716 ML17338A718
References
NAD-2199, ZAR-790331, NUDOCS 7905250430
Download: ML17338A718 (32)

Text

NAD 2l99 DNBR Safety Limit For COBRA XXX C Analysis March l979 A. Xrani W. Wilson R. Wyrick Reviewed By K Date 3 O'7 Approved By Date /Z~ ~

Manager, Nuclear Analysis Dept..

NAD-QR-87 Florida Power and Light. Company Miami, Florida

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1. Xntroduction The objective of this investigation is to determine a DNBR limit for thermal hydraulic calculations performed with the COBRA XXX C code for Turkey Point. Units 3 and 4.- The Turkey Point core loading consists of Westing-house 15xl5 fuel with L-grid spacers.

On the basis of data from 91 test points obtained fzom Columbia University test bundle experiments and des-cribed in WCAP-7988 (reference 1), Westinghouse, in reference 2, derived a DNBR limit of 1.24 as the value that bounds 95% of the 91 point. data base with 95-confidence. The predicted values of critical heat flux .

were calculated with the THXNC computer code using the W-3 critical heat flux correlation and the L-grid correction. However, as reference 1 is a Westinghouse proprietary report, this data base was not available for dizect compazison with COBRA III C results. Xnstead, COBRA XXX C results have been compaxed with'hose ob-tained with the Westinghouse THINC code for a data base (reference 3) suggested by the NRG (reference 4). This data base consists of 284 DNB data points obtained with 12 different test sections. These test sections covered a variety. of heat flux distributions, different heated lengths of rods, and several lengths of axial spacings between grids. Some test sections had spacer grids with mixing vanes and some had no vanes. For the COBRA study, five of these test sections, those corresponding most closely to the L-grid geometry of the Turkey Point fuel, were selected for data comparison. A total of 3.17 points were thus compared.

2. Results The statistical analysis of the 117 data points from reference 3 performed by FPL with the COBRA XII C/MIT code yielded a DNBR limit of 1.1870 while the DNBR limit:

calculated from THINC DNB heat fluxes given in reference 3 for the same data points was 1.1564. Therefore,.

was concluded that the COBRA DNBR limit is 1.1870 it 1.0265 1.1564 times the DNBR limit obtained with the,THXNC code. As discussed above, the DNBR limit for the THXNC code with the L-grid correction is 1.24. Therefore, the corres-ponding COBRA XIX C DNBR limit is 1.24xl.0265=1.273.

IQ' TABLE I INLET (continued)

POWER INLET BUNDLE AV . LOCAL DNB RUN PRESSURE AT DNB TEMP. MA(S VELOCITY lO BTU/i(R-PX2 NO. (PSXA) (MW) (.'P) (10 LBM/HR-PT liEAS PRHD 'R PPPO 242 2413 2. 286 558. 3 2.09 .629 . 705 .892 243 2392 2. 426 541. 0 2.06 .782 .890 .879 244 2412 2.656 514.3 2.07 .856 1.018 ~ 841 245 2112 2.410 537.7 2.04 .663 .699 .948 247 2102 2.713 499.7 2.05 .747 .837 .892 248 1793 2.508 499,. 7 2.11 .733 .835 .878 249 1813 2.658 477.7 2.02 . 77.7 892 . 871.

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379 1810 2.700 587.0 3.58 .551 .505 380 1854 3.049 568.0 3.53 .672 .644 1.044 381 1792 2.688 562.0 3.03 .637 .630 1.011 382 1848 2.827 540.0 3.07 .711 .794 ~ 896 383 2111 2.703 608.0 3.54 .459 .393 1.167 384 2112 3.010 588.0 3.53 .614 .569 1.078 385 2092 2 '74 603.0 3.03 .463 .404 1.147 386 2098 2.650 578.0 3. 08 .628 .640 .982 387 2111 3 '04 573.0 3.03 .613 .568 1.079 388 2.743 624.0 3.71 465 .402 1.158 2417'408 390 2.845 602. 0 3.10 .483 .433 .1. 116 391 2425 2.983 592.0 3.00 .558 .508 1. 100 392 2403 2.732 584.0 2.53 .511 .467 1.095 393 2393 2.998 563.0 2.51 .561 ~ 531 1.057 246 2102 2.583 515.3 2 '6 .711 .784 .907

TEST SECTiON XX RUNS 8 19 1.0 53 69 Q c9' o.

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0.4 0.6 (PREDICTED) X 10 6,, 0.8 BTU/HR-FT2 8 FT USXNE U ROD BUNDLE WITH MIXING GRXD AT 20 XN SPACXNG. COMPARXSON OF DNB DATA WXTH W-3 PREDXCTXONS FROM COBRA XXI.C SUBCHANNEL ANALYSIS

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3. Test, Descri tion A,detailed description of the test bundles and ex-perimental arrangement is given in reference 3. Two basic test section configurations were used in this analysis. They were (1) a 9 rod bundle in a 3x3 square array with a 14 foot heated length, anQ (2) a 16 rod bundle in a 4x4 square array with an 8 foot heated length. The test bundles included both a u sin u and cos u axial heat flux distributions. The "

14 foot. test section used a uniform radial power distribution and the 8 foot test section used a non--

uniform radial power distribution. Various grid designs were utilized to maintain rod spacing for the test bundles. For this analysis, ll7 DNB data points from test sections XX, XXX, VXX, VXXX, and XXX of Table XV of reference 3, were used. Only test sections which included mixing vane grids (excluding the T-H type) were considered in orQer to be representative of FPL fuel assemblies.

4. Data Anal sis The ratio of the measured heat flux for DNB to the predicted heat flux for DNB as well as the values of the heat fluxes, were calculated in a manner similar to that used by Westinghouse anQ described in reference

3. Briefly, the method will be described here.

A. The ratio of predicted to measured DNB heat flux

=

was calculated by II q meas II pred where Q is the experimentally measured total bundle power (H$U) given in ref erence 3, at, which DNB occurs for specified inlet conditions. QXX is the total bundle power predicted by the COBRA XXX C code for a minimum DNBR of 1.0 for the specified inlet conditions using the I-3 critical heat flux correlation multiplied by the grid spacer correction factor, Fs, where Ps 1 e 0 + 0 ~ 03 (G TDC 35

) ( )

10 0-.019 G = Local mass velocity, ibm /hr ft2 TDC = Thermal diffusion coefficient, 0.061 for 20 in. grid span 0.051 for 26 in. grid span

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As an alternate method, the spacer factor Fs could have been included internally in the COBRA calcu-lation of Q >. Sensitivity studies showed that this would lead'o a lower DNBR limit. Following the Westinghouse method described in reference 3, of multiplying the predicted power by the spacer factor external to the code, results in a more conservative value for the DNBR limit.

B. The value of the measured local DNB heat flux, q" meas , was determined at the axial location of minimum DNBR for the bundle power Q I and the speci-fied inlet conditions. 'he predicted local DNB heat flux, q" predd, was. calculated from q" meas and the ratio descry.bed in part A, above.

5. Derivation of DNBR Limit The experimental inlet conditions and values of pred meas pred calcul'ated by FPL using the COBRA XXX C code are presented in Table 1. The DNBR safety limit for a 95x95 upper tolerance limit (i.e., the value of DNBR which bounds 95% of the data base with a 95%

confidence) is given by:

DNBR'imit =

95%95 Z is (q" /q" d), the mean value of the measured to predicted DNB heat, flux ratios 0 is the standard deviation of the ratios, q"q meas q pred E95 95 is a multiplier to give a 95x95 upper tolerance limit for the number of~points, N, in the data base. Values are taken from reference 5.

Ik Por the 117 points analyzed:

N = 117 X = 0.9864 6 = 0.0756 K95 = 1.903 (reference 5) 95x95 95 DNBR Limit = 1.1870 Figures 1 through 5 show comparisons of q" meas 's predd for the test assemblies analyzed. Figure 6 q"

is a composite of all the data points analyzed.

The corresponding Westinghouse DNBR limit for the same experimental points is 1.1564. The difference may be due to some of the conservatism in the COBBA calculations. For example,. sensitivity studies showed that an increase in the number of axial nodes used in- the calculations would have decreased the DNBR safety limit calculated with COBM. and brought it, closer to the Westinghouse limit.

TABLE I INLET POWER INLET BUNDLE AV- LOCAL DNB Il RUN PRESSURE AT DNB TEMP. MA$S VELOCITY 106 BTU/HR PT2 MEAS Il II NO. ~(PSXA (MW) ( F) (10 LBM/HR-FT MBAS . ~ . PRHD q PRZO 8 1504 2.353 520.0 2. 50 '870 . 845 1.029 9 1505 2.586 499.0 2.50 .956 .932 1.026 10 2150 2.116 584.0 2.59 .699 .650 1.075 11 2100 2.310 567.0 2.55 .762 .709 1.075 12 2401 2.281 577.0 2.54 .843 .832 1.013 13 2401 2.145 559.0 2.06 ;793 .798 .994 1508 2.122 560.0 3.43 .732 .775 ..945

'5 14 1808 2.259 579.0 3.55 ;746 .741 1.006 16 1811 2.333 500.0 1.91 .862 .844 1.022 17 1508 2.400 545.0 3.60 .887 .945 .939 18 1504 2.754 482.0 2.48 1.018 1. 000 1.018 19 1532 2.530 466.0 1.97 .935 .918 1.018 20 1504 2. 722 495.0 2.55 .762 .821 .929 21 lS14 2.837 483.0 2.56 .795 .870 .914 22 1812 2.649 519.0 2.51 .691 .735 .941 23 1843 2.854 501.0 2.49 .799 .861 .928 24 2091 2.414 564.0 2.53 .583 .579 1 007

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25 2091 2.708 544.0 2.55 .654 ~ 657 .996 26 2389 2.515 581.0 2.56 .547 .523 1. 046, 27 2391 2.692 564.0 2.54 .650 .643 1.011 28 2391 2 '09 543.0 2.56 .758 .777 .975 29 2397 2.563 620.0 3.43 .496 .421 1.179 30 2391 3.000 601.0 3.58 .581 ~ 519 3.'. 121 31 2394 2.565 605.0 3.01 .497 .439 1.131 32 2395 2.937 582.0 3.03 .639 .592 1.079 33 2394 2.321 560.5 2.01 .560 .547 1.025 34 2394 2. 513 543.0 2.04 .607 .609 .997 35 2395 2.677 520.0 2.04 .698 .732 .954 36 2093 2.599 596.0 3.56 .565 .532 1.062 37 2095 2.921 579.0 3.53 .635 .609 1.043 38 2099 2,228 602.0 3.00 .485 .445 1.090 39 2096 2.649 577.0 3.05 .640 .612 1.046 40 2096 2.880 561.0 3.06 .695 .685 1.015 41 2095 2.313 544.0 2.00 .558 .547 1.020 42 2095 2.525 518.0 2.03 .658 .680 .968 43 2095 2.672 501.0 2. 04 .697 .736 .947 44 1800 2.341 580. 0 3. 52 .610 .637 .957 4S 1799 2.630 563. 0 3.51 ~ .686 .726 .945 46 1799 2.459 559.0 3.01 .641 .665 .964 47 1799 2.777 540.0 3.02 .724 .. 750 .966 48 2099 2;908 524.0 2.50 .758 .778 .975 49 1796 2. 629 494.0 2.06 .685 .709 .967 50 1505 2.565 541.0 3.47 .669 .744 .899 51 1500 3.066 514.0 3 '3 .799 .881 .907

.962 52 1796 2.718 482.0 2.03 .709 .737

0 ~ i TABLE I INLET (continued)

POWER INLET BUNDLE AV. LOCAL DNB I(

RUN PRESSURE AT DNB TEMP. HA$S VELOCITY ,)10 BTU/IIR-FT HEWS NO. ~PSXll) (MN) ( F) (10 LBM/HR-FT fs q PRHD 53 1503. 2.105 558.0 3.58 .778 .864 .901 54 1815. 2.508 560.0 3.62 .927 .967 .958 55 1781. 2.474 481.5 2.03 .914 .944 .968 56 2103. 2.366 502.5 2.02 ,.874 .944 .926 57 2108. 2.279 517 ' 2.04 .842 .888 .948 58 2110. 2.103 541.5 2.03 .777 ~ 785 .990 59 .2114. 2.420 545.0 2. 53'.06

.894 .907 .986 60 2115. 2.519 567.5 ..869 .853 1.019 61 2129. 2.262 581.0 3.07 .780 .780 1.000 62 2097. 1 999 601.5 3.04 .660 .620 , 1.064 63 2104. 2.857 566.0 3.58 .964 .954 1.011 64 2108 2 '73 594.0 3.46 .750 .730 1.028 65 '083.

2.563 577.5 '3. 57 .884 .884 1.000 66 2390 2.476 580.0 3.09 .915 .950 .963 67 2404. 2.158 602.0 3.07 .712 .713 .999 68 2407. 1.949 623.0 3.05 .643 .580 1.109 69 2414. 2.079 627.0 3.56 .686 .625 1.098 206 2084 2.431 579.3 2.60 .603 .587 1.028 208 2026 2.884 536.7 2.61 .795 .833 .953 209 ,1497 2.686 525.0 2.48 .739 .730 1.013 210 1497 3.058 499.5 2.55 ,.842 .837 1.005 211 1497 3.340 478.3 2.55 .919 .919 1.000 212 1491 2.498 566.3 3.51 .663 .677 .979 213 1498 2.905 536.7 3.63 .800 .882 .907 214 1801 2.626 566.3 3.62 .745 .840 .887 215 1797 2.836 568.7 3.51 .725 .725 1.000 216 1790 2.782 501.0 2.07 .766 .780 .9Sl 217 1490 2.418 516.7 2.55 737 .843 .874 218 1490 2.665 496.7 2.56 .779 .889 .876 219 1491 2.861 481.0 2.55 .836 .907 .922 220 1510 2.278 559.7 3.60 .666 .790 .843 221 1512 2.668 539.3 3.59 .780 .905 .862 222 1796 2.257 580.7 3.54 .621 .704 .882

'23 1791 2.797 560.'0 3.68 .770 .845 .911 224 2103 2.232 583.0 2.56 .593 .601 .986 225 2105 2.428 565.3 2.55 .668 .701 .953 226 2103 2.630 546. 0 2.57 .724 .793 .913 227 2103 2.235 599. 0 3. 10'.

.571 .582 .981 228 2113 2.513 583.7 06 .667 .682 .979 229 2124 ~ 2.833 559.3 3.10 .780 .853 .914 232 .2115 3.054 566.3 3.56 .873 .942 .927 233 2422 2.391 626.3 3.54 .561 .522 1.075 234 2424 2.786 602.5 3.61 .. 713 .742 .961 235 2415 3.049 583.7 3.59 . 839 .908 .924 236 2432 2.200 624.3 3.03 .516 .477 1.081 237 2424 2.492 602.2 3.06 .637 .648 ~ 983 238 2414 2 '90 580.3 3.09 .910 .987 .922 239 2413 2.431 579.3 2.58 .669 .724 .924 240 2413 2.711 553.7 2.57 .874 .993 .880 241 2388 2.835 537.0 2.56 .914 1.067 .857

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REFERENCES Cadek, F.F. and Motley, F.E., Applications of Modified Spacer Factor for L Grid Typical and Cold Wall Cell DNB, WCAP-7988-P-A, January 1975 (Westinghouse Proprietary).

2. Reavis, J.R. et. al., Fuel Rod Bowing, WCAP-8692, December, 1975.

3. Rosal, E.R. et. al., High Pressure Rod Bundle DNB Data With Axially Non-Uniform Heat. Flux, Nuc. Eng, Des., Vol 31, 1974.

4. Letter A. Schwencer (NRC) to R.E. Uhrig (FPL), dated September 15, 1978, Dockets No. 50-250 and 50-251.

5. Owen, D.B., Factors for One-Sided Tolerance Limits and for Variables. Sampling Plans, SCR-607, Sandia Corp.,

March 1963.

0 0 TEST SECTION III RUNS 20 -52 1.0 0.8 Q)O r 0 OOP CA OO OC 0.6 ~O 0 9

. Or mlles OQ 0.4

=,

0.2 0

0 0.2 0.4 0.6 0.8 1.0 q" 6 2 (PREDICTED) X 10 BTU/EER-FT FXGURE 2 14 FT USXNU ROD BUNDLE WITH MXXING VANE GRID AT 20 IN SPACING. COMPARISON OF DNB DATA WITEE W-3 PREDICTIONS FROM COBRA XXX.C SUBCEEANNEL ANALXSIS.

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TEST SECTXON VXX 206 216 1.0 RUNS

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<o C) 0.6 r'/'

r 0.2 r r

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0 0 0.2 0.4 0.6 0.8 1.0 c[" (PREDICTED) X l06 BTU/HR-FT 2

FXGURE 3 8 FT COSXNE U ROD BUNDLE WITH MIXING VANE GRXD AT 20 XN SPACINGS COMPARISON OF DNB DATA NITH N 3 PREDICTXONS PROM COBRA XIX.C SUBCHANNEL ANALYSIS.

0 TEST SECTXON VIII RUNS 217 249 1.0 CD p 0 0.8 8 g)

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0.2 0 0.2 0.4 0.6 0.8 1.0 q" (PREDICTED) X 10 BTU/HR-FT NB FIGURE 4 8 FT COSINE U ROD BUNDLE WITH MIXING VANE GRID AT 26 IN SPACING. CO~FARISON OF DNB DATA MXTH W-3 PREDICTXONS FRO~f COBRA XII.C SUBCHANNEL ANALYSIS.

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0 TEST SECTION XXX RUNS 379 393 1.0

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0.2

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0 0 0 2

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(PREDICTED) X 10 BUT/kfR FT FXGURE 5 14 FT COSINE u ROD BUNDLE NITkk MIXING VANE GRID AT 20" SPACXNG. COMPARISON OF DNB DATA NXTlt N-3 PREDXCTIONS FROM COBRA XII.c SUBCHANNEL ANALYSIS.

41 TEST SECTXONS XI r IXX x + 1<crj r

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r t PI VXX, VXXX, XXX A ~

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0 0.2 0.4 0.6 0.8 1.0 q" (PREDICTED) X 10 BTU/$1R-FT FXGURE 6 COMPARISON OF DNB DATA NXTli N-3 PREDXCTIONS FROM COBRA XXX C SUBCIiANNEL ANALYSIS FOR TEST SECTIONS XX, XXX, VXX, VIIX AND XX'I 1

STATE OF FLORIDA )

)

COUNTY OF DADE )

Robert E. Uhrig, being first duly sworn, deposes and says:

That he is a Vice President of Florida Power 6 Light Company, the Licensee herein; That he has executed the foregoing document; that the state-ments made i;n this said docum'ent are true and correct to the best of his knowledge, information, and belief, and that he is authorized to execute the document on behalf of said Licensee.

Robert E. Uhrig Subscribed and sworn to before me this Q/ ~ day of l9 >'7 NOTARY PUBLI in and for the county of Dade, State of Florida HbtAI 'SUO CTATB,OI: NLORIDA IH ~ROg MY COMMISSION 'XPIRES MARCH 27, $ $ Q My commission expires: BOMDEO THRII MAYWARO BONDIHG

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