ML20207R745
| ML20207R745 | |
| Person / Time | |
|---|---|
| Site: | Mcguire, Catawba, McGuire, 05000000 |
| Issue date: | 03/11/1987 |
| From: | Tucker H DUKE POWER CO. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| TAC-62972, TAC-62981, TAC-62982, NUDOCS 8703180088 | |
| Download: ML20207R745 (9) | |
Text
_ _. _ _ - - _ _ _ - _ _ _ _ _ _ _ - - _ _ _ _ _ _ _
1 DuuE Powen GOMPANY P.O. BOX 33189 CHAmL& RTE, N.O. 28942 H
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{,"4[3" March 11, 1987 U.S. Nuclear Regulatory Commission Document Control Desk Washington, D.C.
20555
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Subject:
McGuire Nuclear Station Docket Nos. 50-369/370 Catawba Nuclear Station Docket Nos. 50-413/414 Determination of Rod Worth Using
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Rod Swap Methodology Gentlemen:
Pursuant to telecons of February 19, 1987 and March 10, 1987 between D.S. Hood (ONRR) et.~ al., and S.A. Gewehr (DPC) et. al., attached are revised responses to Questions 6 and 7 of D.S. Hood's request for information dated January 12, 1987.
Very truly yours,
' f b. A fh Hal B. Tucker SAC /61/jgm Attachment r2703180008 870311
[)O PDR ADOCK 05000369 j((
P PDR
Document Control Desk March 11, 1987
.Page 2 xc: Mr. Darl Hood, Project Director Office of Nuclear Reactor Regulation U.S. Nuclear Regulatory Commission Washington, D.C.
20555 Dr. J. Nelson Grace, Regional Administrator U.S. Nuclear Regulatory Commission - Region II 101 Marietta Street NW - Suite 2900 Atlanta, GA 30323 Mr. W.T. Orders NRC Resident Inspector McGuire Nuclear Station
Document Control Desk March 11, 1987 Page 3 f
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bxc: w/o attachment R.H. Clark j
M.S. Kitlan E.O. McCraw
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N.A. Rutherford
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4 Page 1 ATTACHMENT QUESTION 6:
Provide data for at least 2 sets of side-by-side comparisons of I
Boron dilution and Rod Swap Data - predicted and measured. The data may be either for your plants or measured data fron another plant and predictions by Duke.
RESPONSE
In the original Nuclear Physics Methodology Topical, DPC-NF-2010A, Duke Power Company benchmarked its methods for predicting rod worths against measurements made during the startup testing for both initial cores at the McGuire Nuclear Station. These measurements were made using the boration/ dilution technique l
~for determining rod worths in sequential insertion.
In its review of this s
topical, the NRC accepted the capability of Duke Power to adequately predict l
a l
control rod worths and shutdown margin using the outlined methodology.
l In the Rod Swap Methodology Report recently sent to the_ Commission, Duke Power I
benchmarked its methodology for predicting rod worths using the rod swap I
technique against 5 cycles of actual rod swap measurements. This methodology utilized the same computer codes previously benchmarked in DPC-NF-2010A. All predictions, when compared to the measured results, met the acceptance criter-is as outlined in the rod swap plant procedure.
'It has been noted in previous conversations with the NRC that the two bench-i marking studies noted above do not make comparisons of the same units for the same cycles. It is Duke Power's position that there is really no benefit from i
this type of comparison. A valid comparison cannot be expected since boration/-
dilution is a sequential measured worth calculation and rod swap consists of a summation of the worths of each rod individually inserted into an otherwise unrodded core. It is therefore impossible to make direct comparisons between worths of the two methods. The only thing that can be looked at is the
' percent difference between measured and predicted for th two methods. When looking at percent differences between measured and predicted, one does not i
have to look at the same unit and cycle to verify methodologies are correct.
Comparisons of predicted and measured rod worths done using boration/ dilution l
l sud rod swap on the two Catawba units are enclosed. The boration/ dilution l
technique was used to measure rod worths in sequential bank insertion for the l
Catawba 1 Cycle 1 core while Catawba 2 Cycle 1 measurements were done using j
the rod swap technique (Table 1).
From a neutronics standpoint, the two cores are almost identical. This assumption can be justified by examining the core loadings cnd the results of the Zero Power Physics Testing for each of the units.
Several key parameters concerning the core are shown in Table 2.
Also enclosed are the quarter core loading pattern (Figure 1) and a comparison of the quarter core essembly power distribution from the zero power map taken during the startup physics testing (Figure 2).
It should also be pointed out that the rod worths from the rod swap predic-l tions are not the worths used to calculate the shutdown margin. Rod swap only verifies the. code's ability to predict rod worths. The rod worth used in the l
ahutdown margin calculation is the N-1 worth, i
Duke Power has provided a total of nine cycle of predicted rod worth compari-cons to measured data with good to excellent results. This demonstrates the ability of the codes and methods used to adequately model reactivity effects J
l due to control rods in.any configuration. Therefore, the use of Duke Power predictions in the verification of shutdown margin with appropriate factors of i
I conservatism applied to the calculation as outlined in DPC-NF-2010A Section
{
4.2.2.2 is justified.
Page 2 ATTACHMENT QUESTION 7:
What Organization does the safety analysis for the Duke Plants?
When this is not done by Duke, what is done (e.g. tests, comparisons, etc.) to show that the startup test results adequately 3
i.
represent the plant features and assumptions used in the safety analyses?
RESPONSE
l
(
The safety analyses for the McGuire and Catawba Nuclear Stations have been
. performed by the current fuel vendor. The analyses utilized NRC-approved codes i
and methodologies and conservative input assumptions including values for key nuclear physics parameters such as reactivity coefficients, core power c
distributions, and shutdown margins, which are expected to bound the actual values of these parameters for current and future reload cores. An evaluation is performed for each reload cycle which consists of comparing nuclear design predictions to the safety analyses assumptions to ensure the safety analyses i
remain bounding. The cycle-specific evaluation process is described in WCAP-9272,
" Westinghouse Reload Safety Evaluation Methodology." Core physics testing performed for each cycle verifies the nuclear design predictions and ensures the j
actual core physics parameters are conservative with respect to the safety 4
analyses.
I l
The main safety analysis assumption verified by the rod swap procedure is that the
].
plant will maintain adequate shutdown margin per Technical Specifications.
One of I
the purposes of rod swap measurements and comparisons to predicted values is to verify the accuracy of the total rod worth prediction used as an input to the shutdown margin calculation.. An indepentent Duke Power shutdown margin is evaluated for each cycle using methods approved by the NRC in DPC-NF-2010A.
The N-1 rod worth used in this prediction is reduced by 10% for conservatism.
Acceptance criteria listed in the procedure indicate that the total inferred rod worth as measured in the rod swap testing isust be within 10% of the total predicted worth. If the total measured rod worth is less than the predicted worth j
by more than 10%, a review of the shutdown margin is made to determine if the current rod insertion limits provide adeqt ate shutdown margin.
If the shutdown targin is adequate, then no revision of the limits is necessary. However, if the
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margin is not maintained, then Duke will notify Westinghouse, revise the rod insertion limits, and submit any necessary changes to Technical Specifications to l
the NRC.
In order to tie the rod swap measurements to the verification of inputs to the i
cafety analysis, Duke Power will perform an independent shutdown margin for each j
reload cycle using methods approved by the NRC in DPC-NF-2010A.
In addition, for I
cach cycle where Duke generates the rod swap prediction but the safety analysis i
has been performed by a vendor, a comparison between the Duke and vendor predicted i
total rod worth will be made at beginning-of-cycle, hot zero power conditions.
Any significant discrepancies will be documented, reviewed, and resolved prior to ctartup physics testing.
Reference McGuire Nuclear Station, Catawba Nuclear Station Rod Swap Methodology Report for l
j Startup Physics Testing, DPC-NE-1003, Rev.1 December 1986.
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TABLE 1 Rod Worth Measurement Data Comparison of Rod Swap and Boration/ Dilution Techniques Boron / Dilution Rod Swap Integral Worths Integral Worths Predicted Measured Predicted Measured Bank (PCM)
(PCM)
% Diff**
(PCM)
(PCM)
% Diff**
D 772 794
-2.85 773 788
-1.94 C
790 849
-7.47 1214 1203 0.91 B*
852 882
-3.52 1190 1171 1.60 A
249 250
-0.40 572 548 4.20 SE 377 385
-2.12 508 460 9.45 SD 497 525
-5.63 755 772
-2.25 SC 497 522
-5.03 1098 1099
-0.09 SB 765 834
-9.02 SA 674 706
-4.75 N-1 7370 7414
.60 N
5473 5747
-5.01
- Reference Bank
- % Diff = [(P-M)/P]*100
9 TABLE 2 Catawba 1 Cycle 1 and Catawba 2 Cycle 1 Comparison of Core Parameters l
Unit 1 Unit 2 KG U/ASSY a
Batch 1 1.6 424.169 424.623 Batch 2 2.4 423.508 425.805 Batch 3 3.1 423.676 424.519
~~
AVE ENR-I' Batch 1 1.6101 1.6104 Batch 2 2.3999 2.4014 j
Batch 3 3.1022 3.0954 ARO BORON l
ENDPOINT (PPMB) 975 975 ISO. TEMP.
'COEFF (PCM/'F)
-1.745
-1.81 1
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Figure 1 CATAWBA 1 CYCLE 1 AND CATAWBA 2 CYCLE 1 QUARTER CORE LOADING PATTERN H
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Figure 2 O
CIC1 AND C2C1 HZP POWER DISTRIBUTIONS 0 MWD /MTU ARO. HZP. NO XE, HD SM H
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- % DIFF eennessmene*********e*****ene******* sense CIC1 CORE AVERAGE 1.00 C2C1 CORE AVERAGE 1.00
% DIFF CORE AVERABE
.05 C1C1 MAXIMUM MAGNITUDE IS 1.43 AT ASSEMBLY D - 12 C2C1 MAXIMUM MAGNITUDE IS 1.44 AT ASSEMBLY D - 12
% DIFF MAXIMUM MAGNITUDE IS 3.19 AT ASSEMBLY C - 0 PERCENT ERROR BETWEEN THE MAXIMUM VALUES IS
.69 AVERAGE A8 SOLUTE RELATIVE ERROR
.88 PERCENT ROOT MEAN SOUARE OF THE RELATIVE ERROR 1.22 PERCENT ROOT MEAN SOUARE OF THE DIFFERENCE 1.16 PERCENT t