ML20093A949
| ML20093A949 | |
| Person / Time | |
|---|---|
| Site: | Palo Verde  |
| Issue date: | 09/18/1984 |
| From: | Van Brunt E ARIZONA PUBLIC SERVICE CO. (FORMERLY ARIZONA NUCLEAR |
| To: | Bishop T NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION V) |
| References | |
| REF-PT21-84-473-000 ANPP-30550-TDS, DER-84-35, PT21-84-473-000, NUDOCS 8410090410 | |
| Download: ML20093A949 (4) | |
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ILOSVED nric Arizona Public Service Company
% EEP 21 r;; 3 13 September 18,198/:
t ANPP-30550-TDS/TRB U@
U. S. Nuclear Regulatory Commission Reginn V Creekside Oaks Office Park
- 1450 Maria Lane - Suite 210
' Walnut Creek, California 94596-5368 Attention: Mr. T; W. Bishop, Directc' Division of Resident Reactor Projects and Engineering Programs
Subject:
Final Report - DER 84-35 A 50.55(e) Reportable Condition Relating to Setpoint Potentiometers In The PPS Drif t Outside Of Tolerance.
File: 84-019-026; D.4.33.2 Ref erence: A) Telephone Conversation between P. Narbut and T. Bradish on May 17, 1984 B) ANPP-29732, dated June 12, 1984 (Interim Report)
C) ANPP-30355, dated August 29, 1984 (Time Extension) l
Dear Sir:
1 Attached is our final written report of the deficiency referenecd above, which has been determined to be Not Reportable under the requirements of 10CFR50. 55( e).
Very truly yours, 11LLk/w E. E. Van B runt, Jr.
I A'S Vice President Nuclear Production ANPP Project Director EEVB/TRB/nj Attachment ac: See Page Two 8410090410 040918 PDR ADOCK 05000529 8
PDR I l S
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' Mr. T. W. Bishop DER 84-35 Page Two-cc:
Richard DeYoung, Director Office of Inspection and Enforcement -
U. - S. Nuclear Regulatory Commission Was*tington, D. C.
20555 T. G. Woods, Jr. -
D. B. Karner W. E. Ide D. B. Fasnacht A. C. Rogers L. A. Souza D. E. Fowler T. D. Shriver C. N. Russo J. Vorees
]
J. R. Bynum J. M. Allen J. A. Brand D. N. Stover A. C. Gehr W. J. Stubblefield W. G. Bingham R. L. Patterson R. W. Welcher H. D. Foster D. R. Hawkinson L. E. Vorderbrueggen R. P. Zimmerman S. R. Frost L. Clyde l
M. Woods l
T. J. Bloom I
Records Center Institute of Nuclear Power Operations 1100 Circle 75 Parkway, Suite 1500 Atlanta, GA 30339
FINAL REPORT - DER 84-35 DEFICIENCY EVALUATION 50.55(e)
ARIZONA PUBLIC SERVICE COMPANY ( APS)
PVNG3 UNITS 1, 2 I.
Description of Deficiency Af ter experiencing excessive voltage drif t. in a number of setpoint potentiometers in the Auxiliary Feed Actuation System at the St. Lucie II power plant, Combustion Engineering (C-E) began a program in the Summer of 1983 to perform stability testing on the ANPP Plant Protection Systems (PPS), which use identical potentiometers - the Bourns Infinitron series.
C-E identified a total of twelve potentiometers in Unit 1 that exhibited voltage drif t beyond allovable tolerances and required replacement.
II.
Analysis of Safety Implications The subject deficiency was discovered as a result of stability testing of Bourns P/N 3501S-1-102 setpoint voltage course potentiometers in the PVNGS-1 Plant Protection System (PPS).
Stability testing involved monitoring of setpoint voltages over a 14-day period.
Test results revealed that 12 of 160 setpoint voltages exceeded the hardware design acceptance criteria of +4.13 mVdc drift. However, criteria for safety analysis and PdS setpoints were not exceeded. The 12 rotentiometers associated with these setpoint voltages were subsequently replaced via DCP ISJ-SB-039.
Of the 12 out-of-tolerance readings, 3 setpoint voltage drifts were attributed to a single random defect in a bistable comparator card reference voltage source connected to all three of the potentiometers; the potentiometers were not defective at all. The defective comparator card was subsequently replaced.
Of the remaining 9 out-of-tolerance readings, 7 exceeded the hardware acceptance criteria by +3.87 mVdc or less. This drif t is minor since it is less than one tenth of the safety margin which has been established between the trip setpoint and allowable value for the affected parameters and which is included in the safety analysis.
The remaining 2 out-of-tolerance readings were observed to drif t by 47 mVdc and 44 mVdc respectively. This drif t does not exceed the safety margin established between the trip setpoint and the allowable value for the respective parameters.
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Mr. T. W.. Bishop _
DER 84.Page Two' The root cause of the. observed,setpoint drif ts is believed to be differences in 'the physical resistance characteristics of out-of-tolerance potentiometers when subjected to internal.
resistance heating and environmental effects.
Since. the observed setpoint drif ts were within the assumptions of the safety analysis, the reported deficiency would not. have affected safe operation of the plant.
Based on the above, this condition is evaluated as not reportable under the requirements of 10CFR50.55(e) and 10CFR21; since, if this condition were to remain uncorrected, it would not represent a significant safety condition.
III.
Corrective Action The 12 identified potentiometers in Unit 1 have been replaced via DCP 1SJ-SB-039. The Unit 3 PPS was tested prior to shipment and verified to be within specifications.
For the Unit 2 PPS, a stability test will be performed via i
SWA #8A 45 and any potentiometers exhibiting drif t will be replaced via DCP 2SJ-SB-039.
IV.
Ref e rences C-E letter V-CE-30180, dated May 2, 1984 C-E letter V-CE-30555, dated July 13, 1984 DCPs 1SJ-SB-039, 2SJ-SB-039 Plant Protection System Instruction Manual, N.001-13.03-200