ML20055D412
| ML20055D412 | |
| Person / Time | |
|---|---|
| Site: | Braidwood  |
| Issue date: | 01/29/1990 |
| From: | Hunsader S COMMONWEALTH EDISON CO. |
| To: | Murley T NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM), Office of Nuclear Reactor Regulation |
| References | |
| NUDOCS 9007060278 | |
| Download: ML20055D412 (4) | |
Text
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'N Commonwealth Edison i
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) 1400 Opus Pisce i
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) Downers Crove, Illinois 60515
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January 29, 1990
)
Dr. Thomas E. Murley, Director Office of Nuclear Reactor Regulation U.S. Nuclear Regulatory Commission Washington, DC 20555 i
.Attnt NRC Document Control Desk f
Subject:
Braidwood Unit 2 initial-Use of Rod Worth Measurement Using the Rod Exchange Technique NRC_ Doc]r,r,1 No. 50-457 Reference (a): NUREC-1002, Safety Evaluation Report Supplement 2, dated October, 1986 Section 4.3.2 of Reference (a) provided the NRC evaluation which allowed Braidwood Station to use the Rod Exchange method to measure the worth of Rod Control Cluster Banks. Condition (4) of Section 4.3.2 of reference (a) requires that "...a. report comparing the measured and predicted rod worths will be submitted to the NRC within 45 days of the completion of the rod worth' tests for the first.use of rod swan of a reload at each unit." The purpose of this letter is to respond to this requirement.
i Attachment A provides a brief description of the calculations performed in accordance with the Braidwood Station procedure used to make the rod worth measurements.
Table 1 of attachment A summarizes the results obtained.
?
This information is being provided for NRC review.
Please address any questions regarding this submittal to this office.
Very truly yours.
- 1. c. g~A S.C. Hunsader Nuclear Licensing Administrator cc:
S.P. Sands-NRR W. Shafer-RIII BWD Resident Inspector 0516T/SCH:wj.
9007060278 900129 Dl PDR ADOCK 05000457 Q\\
P PDC
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ATTACWIlNT A 7
e 6
(
Braidwood Unit 2, Cycle 2 Zero Power Physics Testing Rod Worth Measurement Results l
The purpose of this test was to determine the differential and
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t.
i integral worth of the reference bank over its entire travel in an t
unrodded core and to determine the integral worths of the remaining banks using the rod exhange method.
Ajequate shutd0wn margin exists i
bared on the rod worth measurements meeting the r equired acceptance criteria.
7he god exchange technique requitec calculations by Nuclear Fuel Services (Reference 2) providing estimated critical positions of the reference bank after exchange with the bank balng measured, P
h, and the associated correction factors, a,.
The measurements were x
obtained for three reference bank positions:
(h )I"lti"l M
a)
Initially fully inserted position, b)
Critical position after exchange, h c)
Final fully inserted position, (h )
I The worth of a measured bank, g, 1st l
x wf=w
- (Op ),
ax(Ap2)x g
' where:
M = The total measured worth of the reference bank.
1) wR l
2)
(Ap )x = The reference bank worth from 0 steps to the 2
M Initial M
and (h ) Return average of (ha)o ao 3)
(Ap )x = The reference bank worth from hM to 228 2
steps.
l 1
2B(060890)ZD79G 1
a
4) o o A c rrOctica fcet:r fcr th) h t;trth du) to th]
g rodded geometry.
Rod worth measurements were performed under the guidance of Westinghouse Rod Exchange topical (Reference 3).
The document states that the allowable percent difference between measured and predicted reference bank worth is 10%, 15% for individual rod banks and 10% for the sum of all measured rod banks.
For individual banks with a predicted vorth less than 667 pcm the allowable difference is 100 pcm rather the.n 15%.
The worth of reference bank (CBC) was measured by dilution. The percent difference between the predicted worth and the measured worth by dilution of CBC was detern.ined to be -3.2%, which is well within the allowable limits as stated above. The results of the rod worth measurements based on the dilution measurement of CBC are shown in Table 1.
Using the rod exchange technique, all control and shutdown banks were exchanged with CBC. Tho largest percent difference between a measured and predicted rod worth was -10.4% for Control Bank A.
Since the predicted worth of CBA was 446 pcm (< 667 pcm) the allowable difference was 100 pcm.
The largest difference between a measured and predicted rod worth in pcm was -55.6 pcm for Shutdown Bank E.
This.value is below the allowable difference of 100 pcm.
The measured total worth of all banks, based on dilution measurements of CBC, was 5012.3 pcm which differs by -1.6% from the predicted worth.
All safety and design acceptance criteria were met.
I 2
28(060890)ZD79G j
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4 ATTACHMENT A -TABLE 1 o
ROD EXCHANGE MEASUREMENTS DILUTION
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BRAIDWOOD UNIT 2, CYCLE 2 Reference Reference Bank Bank Inferred Predicted-Percent Withdrawn Worth North Difference M
BANK Inserted (h,),(steps) y g
(Ap ),
(M I "x M )x "x
I b,.
e g
2x 2
No.
ID Initial Return Airerage (steps)
(pcm)
(pcm)
(pcm)
(pcm)
(pcm)
(%)
x 1
C 901.6 931
-3.2 2
D 22 22 22 146 1.08 14.3 355.7 384.2 503.1 503 0.0 3
B 22 22 22 196.5 1.28 14.3 160.2 205.1 582.2 669 2.0 4
A 22 22 22 95 0.91 14.3 535.9 487.7 399.6 446
-10.4 5
SD 22 22 22 130.5 1.09 14.3 404.1 440.S 446.8 428 4.4 6
SC 22 22 22 130-1.09 14.3 405.8 442+3 445.0 428 4.0 7
SB 22 22 22 206 1.01 14.3 82.2 83.0 804.3 830
-3.1 8
SA 22 22 22 99 1.10 14.3 519.1 571.0 316.3 289 9.4 9
SE 22 23 22.5 130 0.92 14.9 405.3 373.3 513.4 569
-9.8 i
M Measured Integral Reference Bank Worth, WR=
901.6 (pcm)
Total 5012.?,
5093.0
-1.6 1
M Calculations:
W, =WR - Ih } ~ "x M } x I
l 2
I P
P Percent Difference = (W, -W,)/W,x100 Note: Predicted values from Reference 2.
t 3
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ED79G
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