ML20154E421

Amend 1 to CE NPSD-911, Analysis of Moderator Temperature Coefficients in Support of Change in TSs End of Cycle Negative Mtc Limit. App a Consists of Responses to 970226 NRC RAI

ML20154E421
Person / Time
Site:	Waterford
Issue date:	01/31/1998
From:	C-E OPERATING PLANTS OWNERS GROUP
To:
Shared Package
ML20154E412	List: ML20154E410 ML20154E417 ML20154E421
References
CE-NPSD-911-A01, CE-NPSD-911-A1, NUDOCS 9810080178
Download: ML20154E421 (21)

Text

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hC COMBUSTION ENGINEERING OWNERS GROUP CE NPSD-911 Amendment 1 s

1 i

i A'nalysis Of Moderator Temperature l

Coefficients In Support Of A Change In The i Technical Specifications End of Cycle Negative MTC L'imit i

CEOG TASK 1009 Prepared for the C-E OWNERS GROUP January 1998

• old! Esofossa PoA a a6an=Lw __ ABB

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LEGAL NOTICb This report was prepared as an account of work sponsored by the Combustion Engineering Owners Group and ABB Combustion Engineering.

Neither Combustion Engineering,Inc. nor any person acting on its behalf:

A. makes any warranty or representation, express or implied including the warranties of fitness for a particular purpose or merchantability, with respect to the accuracy, completeness, or usefulness of the information contained in this report, or that the use of any information, apparatus, method, or process disclosed in this report may not infringe privately owned rights; or B. assumes any liabilities with respect to the use of, or for damages resulting from the use of, any information, apparatus, method or process disclosed in this report.

Combustion Engineering, Inc.

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. ANAL YSIS OF MODERA TOR TEMPERA TURE COEFFICIENTS INSUPPORTOFA CHANGEIN THE TECHNICAL SPECIFICA TION

l. END OFCYCLENEGATIVEMTCLIMIT .l Table of Contents

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1. Introduction 3

- Ils . Summary 4 l Ill. Methodology 4 IV. Data Base and Data Reduction 5

. V. Results 5 l

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Appendix A: ABB-CE Response to Questions A1 I l

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. ANAL YSIS 0FMODERA TOR TEMPERA TURE COEFFICIENTS INSUPPORTOFA CHANGEIN THE TECHNICALSPECIFICA TION END OFCYCLENEGATIVEMTCLIMIT .

1 Introduction ne accurate knowledge of the moderator temperature coefficient (MTC) at end of cycle is of prime impor-tance in the fuel managanent oflong reload cycles. The designermust ensure that the most negative MTC will always be conservativeto the Technical Specification limit. De required amount of conservatism depends on the accuracy of

. the calculationalmodel, and on the uncertainty attached to the knowledge of the true MTC. If enough reliance can be placed on the calculationalmodels and on the etd of cycle predicted MTC, a surveillance test becomes unnecessary, ne calculationalaccuracy of the analytical models and the confidence assigned to the knowledge of the true MTC are established by comparing calculated and measured values. A moderator temperature coefficient design .

margin (uncertainty)is established such that if the best estimate design MTC is conservative relative to the Technical Specificaion limit by an amount equal to or greater then the design margin, then the Technical Specificsion limit vill

. not be violated. The best este. : value is defined as the calculated value using the current ABB CE methodology augmented by a bias term. Although the Technical Specification limit on negative MTC must be satisfied at end-of-cycle,it is shown that the design margin applies to all times in life. It is also establishedthat if the measured beginning-ofcy +oderator temperature coef5cients agree with the predictions within the design margin, then all measured l coeffk au for that cycle are expected to pool with the data base presented in this report, including the end-of-cycle .

MTC. Dus if the end-of-cycleMTC is expectedte fall wimin the design margm,its measurenent is not required. j la this analysis,isothermettemperaturecoefficients(ITC) are used since they are the measured quantities. ihe ,

measured ITC is assumed to represent the true value. The impact of syna===nc errors in the measurements is reduced

' by combining values obtained on several plants by several utilities using different techasques. The accuracy of the  !

l model is expressed as a bias repreneuting sy=a===ac differences between measured and calculated values, and the uncertausy is expressedas the random hea===between chose values. The uncertamtycan be viewed as a limitation ,

' in the search for the true value. Dus, to ensure compliance with the Tech. Spec. with a high confidence level, the most e.gstive raw calculead design M1C at EOC must be less negative than the Tech. Spec. MTC by an amount equal to thi. bias plustotalunconsinty. ,

s CENPSD-911 A*'**'**** h I L

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i This Amendment 1 updates the data base and validates the conclusions of the original issuance with l respect to the most recent plant predicted versus measured startup data available. Thirty-four data points have l been added since the original report was issued, for a total of 105 data points. For 15 cycles, all three conditions 1 (BOC at hot zero power, near BOC at power, and near EOC at power) have been analyzed. An additional set of i six cycles consists of BOC hot zero power and near EOC at power. A total of 30 near EOC values have been l analyzed. Of the 105 data points, only one shows a residual deviation which equals the design margin. This i amendment demonstrates that enough reliance can be placed on the calculational models and on the EOC predicted l MTCs, and that a surveillance test beco es unnecessary.

II. Summary In order to ensure thst the moderator temperature coefficient will not exceed the Technical Specification limit with a confidence / tolerance of 95/95%,the cycle must be designed,using the ABB-CE methodology,such that the best estimate MTC is:

a. more negative than the BOC TechnicalSpecificationlimit by the design margin, and

b. more positive than the EOC TechnicalSpecsficationlimit by Ihe design margin.

De design margin is determined to be 1.6 pcm/*F at all times in life.

The analysis of a revised data base including the most recent measured and calculated MTC's has established that if the measured beginning-of-eyelemoderator temperature coefficients fall within 1.6 pearF of the best estimate prediction,then it esa be assumed that the end-of-eyele coeffleient will too and its measurementis not required.

He measured data reduction must be based on the current ABB-CE methodologyas described in this report. ,

if the beginning of-cyclefails the acceptance criterir of *l.6 pcmrF and the discrepancy cannot be resolved, then the end of-cyclesurveitance test must be performed.

III. Methodology He methodology used for this Amendment I is identical to that employed in the original issuance.

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. ,g . Amendaunt No.1 L

IV. Data Base and Data Reduction The data base of cycles analyzed within this amendment and to be included in the previous data base of the original issuance are Waterford Unit 3 Cycle 8, Arkansas Unit 2 Cycles 11 and 12, Calvert Cliffs U7it 1 Cycle 12 and Unit 2 Cycle 11, Palo Verde Unit i Cycle 6, Palo Verde Unit 2 Cycle 6 and Cycle 7, and Palo Verde Unit 3 Cycle 6, and include 23 measurements. An additional set of 1I measurements had been added in the interim. The augmented data base contains a significant sample from all Combustion Engineering plants (2700 MW,2815 MW, 3400 MW, and 3800 MW), using both the rod insenion and the power trade measurement techniques. The data reduction of all measurements and predictions for the most recent plant data is summarized in Table 1.

ITC predictions have all been made at the ineasured critical conditioris, so that no adjustments were needed.

The test initial conditions (power level, exposure, inlet temperature, soluble boron concentration and lead bark insertion)were simulated,taking into account all thermal-hydraulicsand xenon feedbacks. Then, without changing the xenon distribution, a change of *3*F was applied to the inlet temperature, keeping the thermal-hydraulics feedback efrects active. The core average temperature was obtained from edited output, and the ITC calculated.

The 105 dats ooints were analyzed for normality using the American National Standard Institute Standard Normality Test. TLe D' Test statistic was 301.39 which implies that the assumption of normality is appropriate based on the percentage points of the D' Test Statistic.

V. Results A complete list of all measured and calculatedITC's is given in Table 1. Table I lists the plants and cycles, the core enrichment and exposure, the operstmg conditions (PPM soluble boron, power and moderator temperature), the measured and calculatedITC and the difference (M-C) in units of pcm/'F. ,

The residuals of the fit ((M-C) values- fitted values] are clotted in Figure i vs. soluble boron concentration.

This figure indicates a fairly uniform distribution of points, with no obvious PPM dependence. The residuals of the fit are also plotted vs. vanous parameters, to de:nonstrate independence of the residual against these parameters, and to show that no significasc variables were omitted in the model, i.e. that the soluble boron is really the only correlating variable. The residuals are plotted vs. core exposure, enrichment, power, moderator temperature, bias and calculated ITC, in Figures 2 to 7. In all Figures, the scatter of the residuals appears random, indicating that there is no correlation of the residuals against any of the chosen variables when including the most recent plant data available.

CE NPSD-911 Am*"A"'*' NO I

The result of this Amendment I su.tes tha; when the data base of measured versus predicted MTC includes the most recent plant data available, the cogelusions of the original issuance remain valid. It is also concluded that the addition of more data beyond the preseet data base will not affect the current conclusions. Specifically, the end-of-cycle MTC monitoring procedure in the absence of a measutementis as follows:

Ifthe isothermettemperaturecoefficients measuredat zero power during the cycle startupprogram, and at power during thefirstpower ascension, fall within the des!gn margin (acceptance criteria) of 51.6pcdF, then the end-of-cyclebest estimateprediction will also be within k1.6 pcdFof the true l

, MTC. To establish congpliance with the Technica! Specifications,the best estimate end-of-cycleMTC  !

. must be less negative shan the Teck. Spec. value by l.6 pcWF.

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v-v Table 1 Measured ITC's, Calculated ITC's, and Residual of ITC's l

1 Core Avg Core Avg PWR . Tmod ITC ITC M-C Ses Residual

. PLANT Cycle Bumup Ennch PPM (%) ('F) Meas Cale pcmFF pcmfF pcmrF  !

E4fF EarF ANO2 9 28367 3.98 276 95 380 2.251 -2.2% 0.450 0.423 0 873 ANO-2 11 14049 4 00 lio2 0 541 0.083 0.228 1.450 -1.883 0.433 i ANO-2 . Ii 15320 4.00 1240 95.5 572 -0.623 4 575 -0.480 1.370 0.890 ANO-2 - 12 13806 4.01 1657 0 548 -0.110 0.012 1.220 -1.780 0.560 ANO-2 12 14151 4.01 1810 98 578 1.042 0.892 1.500 1.243 -0.257 ANO-2 12 28843 4.01 288 97 575 -2.011 2.022 0.110 -0.435 0.545 CC 1 8 14526 3.81 1600 0 532 0.344 0.417 0.730 1.724 0.994 CC 1 8 14526 3.81 1330 0 532 -0.560 -0.408 1.520 -1.459 0 061 CC-1 8 24723 3.81 310 97 570 1.782 1.801 0.190 -0.457 0 647 CC-1 9 16502 3.77. 1398 0 532 0.064 0.187 -1.230 -1.526 0.2%

CC 1 9 24783 3.77 275 97 570 1.065 1.870 0.050 -0.422 0.472  !

CC-1 10 10971 3.95 1750 0 $32 0.265 0.422 1.570 -1.871 0.301 CC 1 10 10971 3.95 1735 0 $32 0.200 0.452 2.530 1.857 -0 663 CC 1 10 27443 3.95 285 97 570 -1.757 -1.781 0.240 0.432 0.672 CC 1 12 15399 4.19 2024 0 535 0.440 0.580 1.400 1.071 4 329 CC 1 12 15579 4.19 1521 100 567 0.260 0.116 1.440 0.577 4 863 CC-1 12 31905 4.19 357 72 559 -1.770 1.645 -1.250 0.503 -0.747 CC-2 5 24423 3.42 44 0 530 -1.610 -1.550 0.500 0.195 -0405 CC-2 5 24423 3.42 44 0 $30 1.740 -1.670 -0.700 0.195 0.505 CC-2 5 24423 3.42 - 44 0 $30 1.950 1.950 0.000 4 195 0.195 CC-2 5 24423 3.42 44 0 530 -2.000 -2.110 0.300 0.195 0 495 CC-2 5 24423 3.42 330 0 530 -1.050 -1.000 0.400 0.476 7876 CC-2 5 24423 3.42 330 0 530 1.110 -1.000 0.300 0.476 0.176 CC-2 5 24423 3 #2 80 100 572 -2.089 2.058 0.310 0.220 0090 CC-2 8 12957 3.95 - 1496 0 $21 0.200 0.387 1.870 -1.622 4 248 CC-2 8 27130 3.93 297 97 570 -1.810 -1.779 0.310 0.444 0 134 CC-2 9 13095 4.15 1801 0 532 0.370 0.544 1.740 1. .k1 0.181 CC-2 9 13095 4.15 1389 0 532 0.470 0.338 1.320 -1.517 0.197 CC-2 11 15926 4.71 1995 0 535 0.470 0.610 1.400 0.872 -0.477 CC-2 11 15982 4.21 1527 100 567 0.23 0.095 1.330 4 413 4 917 32372 4.21 284 100 567 -2.072 1.900 1.720 0.431 -1.289 CC-2 11 3.73 1507 0 523 0.240 0.433 -1.930 1.633 0.297 OFFD 12 15738 3.73 1050 91 565 -0.516 4 448 4 680 -1.184 0.504 OFFD 12 16530 OPPD 12 25777 3.73 309 92 565 i.711 1.004 0.930 4 456 1.386 CENPSD 911 A *meduemetNo.1

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- i Table 1 Continued PWR Tmod ITO iTC M-C Stas Res.Juel l Core Avg Core Avg Cycle Bumup Ennch PPM (%) ('F) Meas Caic pcm/'F pcm/'F pcmrF PLANT E-drF E-4rF 0 521 0.310 0 506 1.960 - 1.688 0.272 OPPD 13 14835 3.12 1561

!!!3 92 565 -0.461 -0.341 1.200 1.246 0.046 OPPD 13 15209 3.72 325 92 565 l.640 1.728 0.880 -0.471 1.351 OPPD 13 25531 3.72 0 523 0.090 0 035 1.250 1.309 0.059 OPPD 14 14562 3.60 1178 768 88 $64 0.912 0.789 -1.230 -0.907 0.323 OPPD 14 14916 3.60

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0 320 0.128 0.038 0.900 -1.189 0.289 PV l 1 0 2.65 10$$

s 0 320 0.369 0.208 1.610 0.962 -0.648 PV 1 1 0 2.65 824 0 565 0.442 4.223 -2.190 -1.159 -1.031 I

PV 1 1 0' 2.65 1025 0 565 0.972 0.709 -2.630 -1.029 -1.601 PV-1 1 0 2.65 893 23 565 -0.587 -0.502 4.850 0.M3 0.113 PV 1 82 2.65 825 0 565 0.150 0.308 -1.580 -1.338 0.008 PV 1 2 11269 3.15 1462 0.422 -0.244 -1.780 -1.309 0.471 PV 1 2 , 11269 3.15 1178 0 565

( $65 0.133 0.256 -1.230 -1.861 0.631 PV 1 3 9727 3.66 1739 0 565 -0.445 0.262 1.830 -1.565 0 265 PV-1 3 9727 3.66 1438 4.130 0.003 1.330 -1.776 0.446 FV 1 3 9727 3.66 1653 0 565 595 0.813 -0.821 0.080 -1.302 1.382 .l 11209 3.66 1170 100 PV-1 3 l

595 -2.291 2.184 1.070 0.628 -0.442 3 22404 3.6a 484 100 PV 1 565 -0.044 0.038 0.820 -1.033 0.213 l FV 1 6 16533 3.84 1753 0 99 589 -1.095 1.014 0.810 0.450 0.360 PV-1 6 18110 3.84 1160 589 -2.490 -2.342 -1.480 -0.560 4.920 6 27460 3.44 415 100 FV 1 0.038 0.059 0.970 1.183 0.213 FY 1 7 16140 3.98 2070 0 565 0.048 0.080 1.280 1.579 0.299 2 912J 3.32 1452 0 565 PV 2 0.M8 0.295 1.730 -1.272 0.458 FV-2 2 9123 J.32 1140 0 565 0.065 0.209 1.440 -1.719 0.279 FV-2 3 12102 3.76 1595 0 $95 0.693 0.535 1.580 -1.444 0.136 FV-2 3 12102 ~3 .h 1315 0 565 1.146 0.%1 -1.850 -1.163 4.687 14462 3.76 1029 100 595 FV-2 3 0.174 0.328 -1.540 -1.863 0.323 4 13988 3.73 1741 0 565 PV 2 4 972 0.882 0.900 -1.258 0.358 j 4 15516 3.73 1126 100 595 FY 2

-2.352 -2.270 0.820 0.599 0.221 4 3.73 455 100 595 4 FV 2 24121 0.070 0.043 -1.130 1.415 0.285 6 17972 3.45 1563 0 565 FV 2 0.428 588 -1.219 -1.094 1.250 0.822 6 19543 3.65 959 99.95

1. V 2 0.830 589 2.205 -2.235 0.300 0.530 6 - - - - 3.65 385 100 FY-2 4.054 4 125 0.038 0.870 0.816 7 13683 3.71 1784 0 565 FV-2 1.257 0.837 4 617 2.200 -0.943 0 2.45 805 0 565 FV-3 1 0.c35 0.061 0.218 1.570 -1.605 2 8402 3.26 1479 0 565 FV.3 0.589 0.424 0.232 -1.920 -1.331 2 8402 3.26 1200 0 565 FV 0.446

-2.054 -2.043 0.110 0.556 19015 3.26 411 99 595 FY-3 2

-2.437 -2.040 0.476 1.364 3.47 330 100 595 2.641 FV-3 3 22874 0.183 1.430 1.710 0.280 3.61 1586 0 565 0.040 FY 3 4 14284

l. 0.147 0.470 1.05) 0.585 3.76 1836 0 565 0.100 FV-3 5 13153 1

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CENPSD-911 AM N* I 1

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. Table 1 Continued Core Avg Core Avg PWR Tmoc ITC iTC M-C Biam Rescual

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PLANT Cyc6e Bumup Ennch PPM (%) (*F) Mens Calc pcmFF pcmFF pcm/* F E-4/*F E 4FF PV 3 6 17053 3.91 l862 0 565 -0.285 0 037 -2.480 1 400 .i 080 PV 3 6 18631 3.91 1222 100 588 -1.253 1.113 -1.400 -0.771 0 629 PV.) 6 27676 3.91 449 99 95 586 -2.495 -2.362 1.330 4.593 0 737 SONGS 2 4 8419 3.75 1798 0 545 0.077 0.278 2.010 l.919 4 091 SONGS 2 4 8419 3.75 1563 0 545 0.364 0.205 -1.590 1.688 0 098 SONGS 2 ' 5 11355 3.95 1615 0 545 0082 0.071 1.530 1.739 0 209 SONGS 2 5 11355 3.95 1208 0 545 -0.860 0.755 -1.050 1.339 0.289 ST L-2 5 14397 3.65 1705 0 $35 0.208 0.370 -1.620 1.827 0.207 ST-L 2 5 26200 3.65 280 100 572 2.114 2.026 -0.880 0.427 0453 ST L-2 6 16024 3.85 1784 0 532 0.219 0 372 1.530 1.905 0 375 ST L-2 6 22570 3.85 782 100 572 -! .203 -l.234 0.310 -0.920 1.230 ST-L-2 6 28462 3.85 283 100 572 -2.033 2.094 0.610 0.430 1.040 ST-L-2 7 18519 3.93 1510 0 532 4.063 0.080 1.430 -1.636 0.206 ST-L-2 8 16668 3.86 1714 0 532 - 0.203 0.370 -1.670 1.836 0 166 ST-L-2 9 16029 3.94 1550 0 532 0.096 0 020 -1.160 1.675 0 515 WSES-3 4 1 074 3.82 1540 0 545 0.074 0.065 1.390 -1.665 0.275 WSES-3 4 14211 3.82 1077 92 582 0.964 0855 1.090 -1.210 0.120 WSES-3 4 25206 3.82 370 95 582 2.129 2.049 0.800 4.516 0.284 WSES-3 5 14898 3.91 1530 0 545 0.097 0.003 -l.000 1.655 0.655 WSES-3 5 15040 3.91 1066 91 582 -0.918 -0.913 0.050 -1.199 1.149 WSES-3 5 25907 3.91 404 93 582 -2.134 2.017 -1.170 4.549 -0 621 WSES-3 6 15524 3.95 1647 0 545 0.114 0.173 2.870 -1.770 -1.100

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WSES3 6 15524 3.95 1411 0 545 0.600 0.383 -2,170 1.538 -0 632 WSES-3 6 15638 3.95 1131 90 578 -0.819 0.726 0.930 -1.263 0.333 WSES-3 6 27465 3.95 444  % $80 -1.896 1.875 0.230 0.588 0.358 WSES-3 7 14974 3.95 1741 0 545 0.160 0.253 0.930 1.863 0.933 WSES-3 7 14974 3.95 1471 0 545 0.435 0.305 -1.300 1.597 0 277 WSES-3 7 16199 3.95 1862 94 578 0.703 0.666 0.370 1.294 Q 924 WSES3 8 14961 4.08 1833 0 548 0.139 0.224 0.850 1.953 1.103 16054 4.08 1254 94.5 578 0.736 0.641 -0.950 -1.384 0 434 WSES3 8 26993 4.08 590 92 577 -1.749 1.583 -1.660 -0.732 0 928 WSES3 8 4

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Appendix A ABB-CE Response to Questions f

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CENPSD 911 I

- Al . Amendment No.1 i-

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. o a This Appendix A has been prepared in response to a number of questions raised by the NRC on the original submittal.

1. What methodology is usedfor calculating MTC?

The Isothermal Moderator Temperature Coefficients (lTC) are calculated with the ROCS coarse mesh nuclear design code. (Reference 1) This code performs two- or three-dimensional flux calculations in full , half- or quarter-core geometries. A typical ROCS core geometry consists of four radial nodes per fuel assembly and 20 to 30 axial planes.

The nodal macroscopic cross sections are calculated from detailed isotopic concentrations and microscopic cross sections. The nuclides are divided into three categories:

Fuel: Includes two uranium, one neptunium and four plutonium nuclides, Fissionproducts: Includes 1 135 and Xe-135, Pm-149 and Sm-149 and a lumped fission products, Burnableabsorbers: Includes depletable boron (B-10), erbium or gadolinium nuclides.

The microscopic cross sections are functionalized vs burnup and operating conditions such as moderator temperature, moderator density, fuel temperature and soluble boron concentration. His treatment provides for a very accurate representation of the cross sections under any operating conditions, and for ccurate spatial isotopic distributions, accounting for all history effects. Daring the flux calculation, thermal-hydraulic feedback and egailibrium xenon calculations are performed to ensure consistency between the power, moderator temperature and density, fuel temperature and xenon distributions. The local fuel temperature is determmed from a correlation vs burnup and power, and from the local moderator temperature ne calculation of the moderator temperature coefficientis performed as follows:

1. A reference calculationis performed to simulate the core conditions at the begmnmg of the testing program. .

All thermal-hydraube and xenon feedback options are exercised, and the critical control rod position and soluble boron concentranonare supplied.

2. Two off-nominal calculadons are psifvuued by changing the inlet temperature above and below that of the reference r=dirlan usually by 3*F. The power level, xenon distribution, control rod insertion and soluble boron concentration are kept unchanged from the reference condition. The change in core reactivity is therefore due to the change in inlet temperature, and to the ensumg change in the distribution of the moderator 4 .and density and of the fuel temperature. For the nominal and the off-nominalcues, the ROCS code provides an ed.: of the core reactivity and of the volume average moderator temperature.

The moderator temperature coefficienus defined as the ratio of the reactivity change to the core average moderator tsmysi.rdre change.

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t CENPSD-911

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l The moderator temperature coefficient prediction is usually accompanied by one of two of the following calculations, depending upon the measuring technique. If the ITC is measured by the rod insenion technique, a prediction of the lead bank insenion wonh curve is performed, using full thermal-bydraulic feedback, but keeping the power level, xenon distribution, inlet temperature and soluble boron concentrationof the reference case. If the ITC is measured with the power trade technique, a prediction of the power coefficient is performed, again under the rod insenion, boron concentration and xenon distributionof the referencecase.

2. Has the methodology changed since the data analysis presented in the repon? If yes, please explain changes and the effect of these changes.

All results presented in this topical report and its amendment have been generated with the same methodology.

3. Is only the methodology referencedin answering question 1 involved or are there more than one m;.nodologiesinvolved?

De methodology described in paragraph 1 above is the only one which has been used in the preparation of this repon.

4. Wdi Combustion Engineeringperform the calculations in all cases or will the utilities perform them in some cases? If utilitiesperfonn the calculations, what codes will they use?

Combustion Engmeering has performed all calculations presented in this report. Should Utilities perform suc calculations in the fumre, they will use a consistent methodology. The analysis presented in this repon has demonstrated the random nature of the residual between measured and predicted temperature coefficients. Sinc residual cannot be correlated agamst any pai.ructer, one can assume that it is due entirely to measurement uncertamties, and as such is ire of the analytical technique. Any NRC approved physics code system, e.g.

DIT ROCS or CASMO-SIMULATE,will lead to the same level of uncertamties. However, the calculational bias will be established for each code system.

S. Assuming Combustion Engineering has performed all the calculations, why is there not more data? In addidon, please supply all additional data obtained since the repon was prepared (Update Table 1 to include all data available)

The data base pad in the Topical Repon contains a large number of meuurements, collected unde operating conditions for all classes of Combustion Engineering plants, ne purpose of the repon wa large enough data base and to perform statistical tests to show that data from various plants, levels or exposures, measured with vanous exedrucrdal techniques, belong to tbc same pty4h addition or removal of some data points will not impact the conclusions.

CENPSO 911 Amendment No. I

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o <s V The data' base was considered to be large enough to justify the conclusions reached in the report. Since the Report was issued in 1993,34 data points have been added to the data base and are presented in this Amendment. The additional data provides a significant sample of all Combustion Engineering plants (2700 MW, 2815 MW, 3400 MW and 3800 MW), using both the rod insertion and the power trade measurement techniques. The extended data confirms the validity of the conclusions reached earlier. Because of the truly random nature of the data base, the sample size chosen for this amendment is deemed sufficient.

Some experimental data from earlier cycles of older plants has not been incorporated, because it was originally analyzed with slightly different methods and also because the fuel management used at the time was not representative of current fuci management practices.

6. In examining the data on Table 1, it appears that there are only a small number of sets (consisting of 3 measurements - a BOC, zero power measurement; - a BOC, full power measurement;and a near EOCfullpower measurement)of data. Why is this the case?

The data base presented in this amendment has been increased and now contains 15 sets of 3 measurements per cycle

(- a BOC, zero power measurement; a BOC, full power measurement; and a near EOC full power measurement).

In addition,6 sets of 2 measurements (- a BOC, zero power measurement and a near EOC full power measurement) are included. A total of 30 near EOC values are included in the data base.

7, From the data in Table 1, there are only S cases in which cil three measurementsfall within the acceptance criteria. Please discuss why this should be sufficient. .

In the increased data base, only one data point shows a deviation equal to the design basis. Of the 13 sets of three measurements and 6 sets of 2 measurements, no data point exceeds the design basis. ,

Reference:

1. "The ROCS and DIT Computer Codes for Nuclear Design," CENPD-266-P-A, April,1983.

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