ML20084F697
| ML20084F697 | |
| Person / Time | |
|---|---|
| Site: | Turkey Point  |
| Issue date: | 04/14/1975 |
| From: | Schmidt A FLORIDA POWER & LIGHT CO. |
| To: | Rusche B Office of Nuclear Reactor Regulation |
| References | |
| RO-250-75-1, NUDOCS 8304210244 | |
| Download: ML20084F697 (3) | |
Text
P.C. BOX 3100 MIAMI. f tORIDA 33101
.-...-g FLORtDA PO'AER & LIGHT COMPANY April 14, 1975 Mr. Benard C.
Rusche, Director Office of Nuclear Reactor Regulation U.
S.
Nuclear Regulatory Commission Washington, D. C.
20555
Dear Mr. Rusche:
UNUSUAL EVENT NO. 250-75-1 TURKEY POINT UNIT NO. 3 APPARENT DISCREPANCY BETWEEN MEASURED CONTROL ROD WORTH AND VENDOR PREDICTIONS A.
DESCRIPTION OF EVENT During physics tes. ting following Unit 3 Cycle II refueling, a comparison of measured control rod worths to the predicted worths, furnished by the vendor indicated
' discrepancy of approximately 19% for total control rod bank worth.
The measured val-ucs were lower than predicted which gave some concern as to required shutdown margin at beginning-of-cycle.
Further testing verified that adequate shutdown margin existed so normal operation of the unit was initiated.
B.
APPAR$NT CAUSE AND ANALYSIS OF EVENT An investigation into the apparent discrepancy was initiated by Florida Power & Light Company to determine its cause and extent.
The fuel vendor was requested to reconfirm the predicted values for Cycle II operation.
In addition, Florida Power & Light Company engineers performed independent calculations of beginning-of-cycle physics parameters.
The Florida Power & Light Company calculations indicate that the measured control rod worths are within 6% of predicted values for beginning-of-cycle conditions.
Further, end-of-cycle calculations indicate that adequate shut-down margin will be available.
C.
CORRECTIVE ACTION The fuel vendor has recalculated his predictions and the results, included as Table 1, are consistent with Florida Power &-Light Company predicted values.
Based on this recalculation and our a: 'i
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Mr. Benard C. Rusche, Director Page Two April 14, 1975 L-independent calculations, adequate control rod capability and
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shutdown margin exist throughout Cycle II.
L-Very truly yours,
- l pM II A.
D. Schmidt
.Vice President Power Resources PJW/cpc Enclosure cc:
Mr. Norman C. Moseley Jack R. Newman, Esquire 6
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TABLE 1 i
u TURKEY POINT UNIT NO. 3 - CYCLE 2 l
END OF CYCLE SHUTDOWN REQUIREMENTS AND MARGINS 1
REVISED I
ITEM CYCLE 1 CYCLE 2 Control Rod Worth at HZP (%Ap)
'All Full Length Rods Inserted 7.71 7.23 All Full Length Rods Inserted Less Worst Stuck Rod (F-14) 6.47 6.01 (1) Less 10%
S.82 5.41 Control Rod Requirements (%Ap)
Power Defect (Combined Doppler, Tavg, Void and Redistribution ertects) 3.07 2.61 Rod Insertion Allowance 0.70 0.70 (2) Tota,1 Requirement 3.77 3.31 Shutdown Margin [(1) - (2)] (%Ap) 2.05 2.10 Required Shutdown Margin (%Ap) 1.77 1.77 Excess 0.28 0.33 The revised control rod worth is based on the end of Cycle 1 critical boron and an adjustment to the radial reflector cross-section to provide better agreement with power distribution measure-ments.
The revised power defect is based on a more accurate evaluation at the Cycle 2 plant operating conditions for a core average moderator temperature of 567.3*F at a system pressure of 1,900 psia, as pre-viously documented in the Unit No. 3 Design Report.
Based on this revised analysis, the calculated N-1 rod worth at BOC II is within 6.7% of the measured value.
In addition, at BOC II the reanalysis provides good agreement between the calculated and measured power distribution and the HFP and HZP critical boron concen-trations.
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