ML20207D803
| ML20207D803 | |
| Person / Time | |
|---|---|
| Site: | Palo Verde  |
| Issue date: | 07/07/1986 |
| From: | Van Brunt E ARIZONA PUBLIC SERVICE CO. (FORMERLY ARIZONA NUCLEAR |
| To: | Kirsch D NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION V) |
| References | |
| REF-PT21-86-260-000 ANPP-37206-EEVB, DER-86-22, PT21-86-260-000, NUDOCS 8607220190 | |
| Download: ML20207D803 (5) | |
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ricaVED wq Arizona Nuclear Power Project g,g ;; ggg P.O. BOX 52034 e PHOENIX, ARIZONA 85C?2-2034 July 7, 1986.,
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3 ANPP-37206-Eh?iB/LAS /DRI[-92.11 q
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b U.-S. Nuclear Regulatory Commission Region V 1450 Maria Lane - Suite 210
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Walnut Creek, California 94596-5368 a'
Attention:
Mr. D. F. Kirsch, Acting Director Division of Reactor Safety and Project 9 '
", s Palo Verde Nuclear Generating Statrion (PVNGS)
Units 1, 2, 3
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j Docket Nos. 50-528, 529, 530
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Subject:
Final Report - DER 86-22 A 50.55(e) and 10CFR21 Condition Relating to Redundant Fault Current Protection 4
-m File: 86-006-216; D.4.33.2
Reference:
(A Telephone Conversation between R. C. Sorenson and ' D[R. Larkin on June 24, 1986 (Initial Reportability ER 86-22)
Dear Sir:
Attached, is our final written report of the Deficiency under 10CFR50.55(e) referenced above. The 10CFR21 evaluation is also inc.itided.
Very truly yours, 7
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E. E. Van Brunt, Jr.
Executive Vice Fresident Project Director EEVBJr/DRL:kp Attachments cc: See Page 2 1
8607220190 860707 PDR ADOCK 05000528 S
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ANPP-37206-EEVB/LAS/DRL-92.11 July 7, 1986 DER 86 Final Report Mr. D. F. Kirsch Acting Director Page Two ec:
Mr. J. M. Taylor, Director Office of Inspection and Enforcement U. S. Nuclear Regulatory Commission Washington, D. C.
20555 A. C. Gehr (4141)
R. P. Zimmerman (6295)
Records Center Institute of Nuclear Power Operations 1100 Circle 75 Parkway - Suite 1500 Atlanta, Georgia 30339 l
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FINAL REPORT - DER 86-22 DEFICIENCY EVALUATION 50.55(e)
ARIZONA NUCLEAR POWER PROJECT (ANPP)
PVNGS UNITS 1, 2, 3 I.
Description of Deficiency Requirement / Violation Regulatory Guide 1.63 requires that redundant protection shall be provided if the expected fault current may damage the penetration. DER 83-47 investigated the power, control, and instrument penetrations where the power supply has sufficient energy to damage the penetration conductors. Backup overload protection devices were provided for these circuits.
During Unit 3 update of Electrical Penetration Assembly (EPA) backup protection calculation 13-EC-PK-160, it was discovered that certain portions of the Reactor Coolant Pump (RCP) control circuitry had not been fully analyzed in regard to coordination of primary and secondary protective devices. Although one (1) circuit in the RCP starting scheme was fully analyzed, three (3) circuits had not been specifically analyzed to demonstrate that these circuits satisfied Regulatory Guide 1.63.
Evaluation These three (3) control circuits for each of the four (4) RCPs are routed through the EPA, using #14 AWG conductors which have a continuous current rating of less than thirty (30) Amps. The maximum calculated fault currents in these circuits range from twenty-two (22) to seventy (70)
Amps. Two (2) of the circuits are protected by two (2), fifteen (15) Amp fuses and one (1) circuit is protected by two (2), thirty-five (35) Amp fuses. Each RCP control circuit is backed by a forty (40) Amp thermal magnetic molded case circuit breaker.
The three (3) RCP control circuits identified operate as follows:
Circuit #1 - Presence of lift oil flow.
The oil lift pump must be operating prior to closure of the RCP circuit breaker.
The pump shuts down after the RCP circuit breaker ' remains closed for two (2) minutes. When lift oil flow decreases, this control circuit is deenergized by action of the' lift oil flow switch. This circuit is protected by two (2), fifteen (15) Amp fuses. A maximum calculated fault current of forty-one (41) Amps for two (2) minutes exceeds the thermal rating of the EPA.
Due to the time-current characteristics of the forty (40) Amp breaker, it does not provide adequate protection for this fault condition.
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DER 86 Final Report Page Two Circuit #2 - Vibration detector cutout.
The RCP vibration switch is blocked for a period of twenty-five (25) seconds after the RCP circuit breaker is closed. This circuit is deenergized by operation of a time delay relay at twenty-five (25) seconds after the RCP circuit breaker closure.
This circuit is protected by two (2),
fifteen (15) Amp fuses. A substained fault occurs during starting of an RCP only if there is a short across the relay coil and the time delay relay contact fails to open along with the fifteen (15) Amp fuses failing to blow.
Circuit #3 - Presence of motor operating speed.
If the RCP speed is not greater than six hundred (600) RPM within fourteen (14) seconds after circuit breaker closure, the breaker trip circuit is engaged and the motor shuts down.
This speed sensing circuit is energized for a maximum of twenty-five (25) seconds af ter initial circuit breaker closure. This circuit is protected by two (2), thirty-five (35) Amp fuses. A substained fault occurs only if there is a short across the relay coil and the time delay relay contact and the speed switch fails to open during starting of the RCP.
The three (3) RCP control circuits identified are energized during starting of the RCP's only and are not required for continuous operation.
When the RCP's are running, these circuits are deenergized. A fault in these circuits, after the initial two (2) minutes of RCP start, is unlikely.
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Since circuits one (1), two (2), and three (3) do not represent a significant safety condition, backup fuses can be added during the next available maintenance outage. Additionally, as a precautionary measure, circuit number one (1) will be checked for shorts prior to every restart until the backup fuses can be installed.
Root Cause l
l The root cause of this condition was the inadequate preparation and i
design review, by Engineering, for calculation 13-EC-PK-160 to ensure that all penetration protection circuits had been addressed in accordance with Reg. Guide 1.63.
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DER 22 - Final Report Page Three Transportability The complete control and instrumentation penetration protection calculation (which includes over four hundred (400) control schemes) has been subjected to a thorough review and found acceptable, with the exception of the RCP control circuits identified. All power penetration calculations were reviewed in detail in response to DER 83-47.
Safety Assessment Circuits two (2) and three (3), discussed above, are energized for a short period only during starting of the RCP's.
Time delay relay contacts or switch contacts coulti deenergize these circuits before any significant damage, due to a fault, would occur.
The fault condition in circuit one (1), as discussed above, could have sufficient energy (based on an analysis of the short-circuit current vs. time conditions) to damage the penetration seal if no corrective actions were taken.
However, the possibility of damage to the EPA is remote because it requires simultaneous failures of independent components. Therefore, these circuits do not represent a significant safety condition.
II.
Analysis of Safety Implications Based on the above, this condition is evaluated as Not Reportable under the requirements of 10CER50.55(e) and 10CFR Part 21, since if this condition were to remain uncorrected it would not represent a significant safety condition.
III. Corrective Action 1.
Calculation 13-EC-PK-160 has been reviewed and is being updated to reflect the 3 control circuits for the RCP's.
2.
PCR 86-13-RC-045 has been issued, as an enhancement, to add backup fuses to each of these circuits.
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