ML20207L214
| ML20207L214 | |
| Person / Time | |
|---|---|
| Site: | Mcguire |
| Issue date: | 10/10/1988 |
| From: | Tucker H DUKE POWER CO. |
| To: | NRC OFFICE OF ADMINISTRATION & RESOURCES MANAGEMENT (ARM) |
| References | |
| NUDOCS 8810170229 | |
| Download: ML20207L214 (6) | |
Text
.
ll l
IMe 1%er Company Hu H Trs-PO ikt 331%
h e rn u h nt i
t CharVlte NC 24242 Li~rnJam l
Mmn mt fr DUKE POWER October 10, 1988 l
U.S. Nuclear Regulatory Commission ATTN Document Control Desk l
Washington, DC 20555 l
Subject:
McGuire Nuclear Station. Unit 2 Docket No. 50-370 Rod Swap Methodology Review Criterion Failure Report cycle 5 Startup Physics Test - July 27, 1988 Centlement
{
By letter dated May 22. 1987, the NRC approved Duke Power Company's "Rod Swap Methodology P# port for startup Physics Testing" (DP C-N E-1003-A Revision 1
(
December 1986) for use on McGuire and Catauba Nuclear Stations. Units 1 and 2 I
subject to certain conditions listed in the associated NRC Safety Evaluation l
Report (SER).
One of these conditions (No. 5) specifies remedial action for l
failure of an acceptance or review criterion, requiring investigation and i
solution within 30 days (for Acceptance Criterion) or 60 days (for Reviev Criterion), with the submittal o' a report of the findings to the NRC within 45 days of the test (f or Acceptance Criterion) or within 75 days of the ceet (for Review Criterion).
On July 27, 1988, during the McGuire Unit 2 Cycle 5 Rod Swap Test Measurement, the reference bank vorth. Shutdown B. was measured to be 11.2% below the predicted value.
This value exceeds the 10% review criterion for the l
reference bank vorth as specified by the ebove mentioned NRC SER.
Accordingly, as a requirement of the SER, a report to explain this discrepancy is due to the NRC 75 days after the Unit 2 test.
Please find attached the subject Review Criterion Failure Report.
The report summarizes the evaluation performed to explain the over-prediction of the reference back vorth for McGuire Unit 2 Cycle 5.
Should there be any questions regarding this report or if additiosual information is required.
please advise.
t Very truly yours, q
//
p,z Ea1 B. Tucker l
PBN/116/.mf
/
l Attachment fjth f,#
8910170229 891010
{
PDR ADOCK 0500037f p
PN' r
. _ =.
Document Control Desk October 10, 1988 Page 2 xc:
(w/ attachment):
1 Dr. J. Nelson Grace Regional Administrator i
U.S. Nuclear Regulatory Commission 101 Marietta Street, NW, Suite 2900 I'
Atlanta, GA 30323 I
l Mr. Darl S. Hood, Project Manager
{
Of fice of Nuclear Reactor Regulation U.S. Nuclear Regulatory Commission Washington, DC 20555 l
P r'
Mr. P.K. Van Doorn NRC Resident Inspector McGuire Nuclear Station 1
l e
1 1
6 I
+
1
{
t i
i 5
i 1
t
+
I i
l l
i i
i i
l I
f I
Document Control Desk October 10, 1988 Page 3 bxc: (w/ attachment):
N.A. Rutherford R.L. Gill S.E. LeRoy S.A. Gewehr T.C. Geer N.R. Hager K.S. Canady R.H. Clark D.E. Bortz J.H. Randles M.S. Kitlan. Jr. (MNS)
S.W. Brown (CNS)
T.L. McConnell (MNS)
R.O. Sharpe (MNS)
MC-801.01 l
(
Duke Power Company McGuire Nuclear Station i
Rod Swap Methodology Review Criterion Failure Report Unit 2 Cycle 5 Startup Physics Test - July 27, 1988 1
INTRODUCTION / BACKGROUND i
Rod worth measurements at the McGuire Nuclear Station are performed using the methods described in "Rod Swap Methodology Report for Startup Physics Testing " (DPC-NE-1003-A). This testing methodology uses a dual set of criteria for test result evaluation. These criteria are (1) review, which have no direct safety significance, and (2) acceptance, which are based on meeting safety analysis input assumptions.
The specifics of these criteria i
are described in the NRC Safety Evaluation Report (SER) for DPC4tE-1003-A.
On July 27, 1988, during the McGuire Unit 2 Cycle 5 Rod Swap Test measurement, the reference bank worth. Shutdown B, was measured to be 11.2% below the predicted value. This value exceeds the 10% review criterion for the reference bank worth. All other rod swap measurements met their r6spective review and acceptance criterion.
Results from the McGuire 2 Cycle 5 Rod Swap Test are provided in Table 1.
The totsi predicted and measured rod worths agreed within 3.9%.
Therefore, no safety analysis input assumptions are r
affected. This report summarizes the evaluation performed to explain the over-prediction of the reference bank worth.
i EVALUATION The evaluation performed concentrated on the following areas.
j 1)
Review of analytical predictions.
J j
2)
Review of plant test procedure.
j 3)
Comparison of rod exchange data to boron endpoint data.
4)
Comparison of Measured and Predicted Power Distribution.
{
5)
Control rod examination.
e f
The computer models and calculations on which the rod worth predictions were i
based were reviewed and no errors were found. The cross sections used in the i
McGuire 2 Cycle 5 PDQ model were reviewed and found to be consistent with
}
those used for cycle 4.
The dwlayed neutron fraction (61) can be affected by l
rodded configurations by as much as 3% in some cores.
However, for the McGuire 2 Cycle 5 core this effect was found to be negligible.
A review of the plant test procedure for control rod worth measurement l
(PT/0/A/4150/11) for the Reference Bank was performed. No errors were found 1
in the test procedure or calculations.
The dilution rate during the measurement of the reference bank was determinad to be 348 pcm/ hour, which satisfied the procedural limit and the SER for DPC-NE-1003-A. A review of the reactivity trace from the strip chart recorder showed no not.iceable anomalies.
l However, a change from unrodded to Shutdown B In conditions resvits in a j
radial power redistribution into the peripheral assemblies of about 15%. This 1
shift in the radici power distribution could result in a reactivity under-estimate of Shutdown B following the rod motion because of a change in neutron leakage as seen by the excore detector. This effect could have contributed to a low measurement of Shutdown B rod worth by the reactivity computer.
)
i I
'The differences between the measured and predicted critical boron concentrations for ARO and Shutdown B In conditions were 84 and 85 ppm, respectively. These values compare favorably. However, the measured boron worth determined from the rod worth based on the reactivity computer and the measured boron endpoints was inconsistent with this cycle's predictions.
This discrepancy implies a greater rod worth for Shutdown B than measured by the reactivity computer.
l A comparison between measured and predicted radial power distributions at various power levels was performed.
These comparisons showed an in-out tilt of 2-3% where predicted powers in the peripheral assemblies were over-predicted relative to measured powers.
Since Shutdown B is near the core periphery this implies that the predicted worth of Shutdown B should have been approximately 4.5% less, i
Examination of all control rods using the eddy current technique was performed during the McGuire 2 Cycle 5 refueling outage. The results of this examination confitned that the cladding of the control rods was intact, thus eliminating any concern with leaching of the B C absorber material being a 4
cause of the low measured rod worth.
CONCLUSION l
4 Duke Power has reviewed the resulte of the McGuire Unit 2 Cycle 5 Rod Swap test and found no errors in the rod worth measurement or procedures or in the calculational models used in the rod worth predictions.
The probable cause of l
the difference between the measured versus predicted rod worth of the i
]
reference bank is a combination of flux redistribution effects during the measurement, and a small in-out tilt of the radial power distribution. Since
]
the total measured rod worth for McGuire 2 Cycle 5 met both its acceptance and review criteria, there is no ef fect on the safety analysis input assumptions due to these measurements.
i i
l l
J i
TABLE 1 McGuire 2 Cycle 5 Rod Swap Test Results Measured vs. Duke Predicted Bank Worths Measured Duke Predicted Bank Worth Bank Worth
% Diff BANKS INSERTED (PCM)
(PCM)
((M-D)/D)*100 CTL 0 IN 634 633 0.16 CTL C IN 826 828
-0.24 CTL B IN 696 769
-9.49 CTL A IN 346 299 15.72 SE IN 407 397 2.52 SD IN 452 484
-6.61 SC IN 447 482
-7.26 SD IN (REFERENCE BANK) 748 842
-11.16 SA IN 311 332
-6.33 TOTAL WORTH 4867 5066
-3.93 1