ML18153C997
| ML18153C997 | |
| Person / Time | |
|---|---|
| Site: | Surry  |
| Issue date: | 05/06/1992 |
| From: | Stewart W VIRGINIA POWER (VIRGINIA ELECTRIC & POWER CO.) |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| 92-322, NUDOCS 9205140101 | |
| Download: ML18153C997 (3) | |
Text
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I VIRGINIA ELECTRIC AND POWER COMPANY RICHMOND, VIRGINIA 23261 May 6, 1992 United States Nuclear Regulatory Commission Attention: Document Control Desk Washington, D. C. 20555 Gentlemen:
VIRGINIA ELECTRIC AND POWER COMPANY SURRY POWER STATION UNIT 1 CONTROL ROD URGENT FAILURES TEMPORARY WAIVER OF COMPLIANCE Serial No.
NL&P/ETS Docket No.
License No.92-322 R4 50-280 DPR-32 Surry Unit 1 received Rod Urgent Failure Alarms on May 3, 1992 and twice on May 5, 1992. The Rod Urgent Failure Alarm indicates a fault in the Control Rod Drive System which renders a group or bank of control rod assemblies inoperable due to the inability to move the control rod assemblies on demand by the Control Rod Drive System.
However, for this faulted condition the control rod assemblies remain trippable.
In this condition the unit is required to enter Technical Specification 3.12.C.3 which provides two hours for troubleshooting and repair prior to requiring that the unit be brought to hot shutdown in six hours.
The urgent failures have been attributed to circuitry in a cabinet of the Control Rod Drive System. However, to effect thorough troubleshooting and repairs, a waiver of the two hour Action Statement in Technical Specification 3.12.C.3 is being requested.
The Action Statement was entered at 1750 hours0.0203 days <br />0.486 hours <br />0.00289 weeks <br />6.65875e-4 months <br /> on May 5, 1992. The waiver will allow continued operation for up to fifty hours to troubleshoot and repair the Control Rod Drive System with more than one control rod assembly immovable due to an external electrical problem, provided the affected control rod assemblies remain trippable.
In a May 5, 1992 telephone call between Virginia Power and the NRC, we requested and received verbal approval for a waiver to extend the two hour Action Statement of Technical Specification 3.12.C.3 to fifty hours to complete thorough troubleshooting and repair of the Control Rod Drive System.
SAFETY IMPACT AND POTENTIAL CONSEQUENCES The operation of the unit with more than one control rod assembly being inoperable does not create any immediate threat to safety when these control rod assemblies are trippable. The control rod assemblies continue to be capable of performing their intended safety function to promptly shutdown the reactor when a safety system setting is reached (i.e., reactor trip). Adequate core protection is maintained by maintaining 9205140101 920506 PDR ADOCK 05000280 p
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insertion limits, bank overlap and shutdown margin. Power level will be maintained stable during the troubleshooting and repair activities.
In addition, since the rod control problem does not affect the controlling bank (i.e. "D" bank control rod assemblies are unaffected), the operators can utilize control rod assemblies to maintain a stable power level or to reduce power should a controlled shutdown be required, thus minimizing the transient on the plant if a reactor shutdown becomes necessary.
SIGNIFICANT HAZARDS CONSIDERATION The proposed waiver of the two hour Action Statement of the Technical Specification requirement in 3.12.C.3 for inoperable but trippable control rods does not result in a significant hazards consideration as defined in 1 O CFR 50.92.
Specifically, the proposed waiver does not:
Involve a significant increase in the probability or consequences of an accident previously evaluated.
Allowing fifty hours for the diagnosis and repair associated with electronic or electrical malfunctions of the Control Rod Drive System is acceptable, since the primary safety function of the control rod assemblies (reactor trip) remains unaffected.
During the extended troubleshooting and maintenance period, the requirements for control rod assembly alignment, insertion limits, and shutdown margin are being maintained so that power and peaking distributions used in the safety analysis will remain unaffected. The proposed changes do not affect the ability of the control rod assemblies to perform their intended safety function when a safety system setting is reached. Therefore, the consequences of accidents related to or dependent on control rod assembly operation will remain unaffected.
Create the possibility of a new or different kind of accident from any previously evaluated. There are no new failure modes or mechanisms associated with plant operation for an extended period to perform maintenance on the Control Rod Drive System. Extended operation with inoperable but trippable control rod assemblies does not involve any modification in the operational limits or physical design of the involved systems. There are no new accident precursors generated due to the extended maintenance period.
Involve a significant reduction in the margin of safety. Plant operation with the inoperable but trippable control rod assemblies does not affect the Technical Specification margin of safety. During the extended maintenance period the control rod assemblies maintain the ability to perform their primary safety function. Other Technical Specification limits for reactivity control, such as control rod assembly insertion limits, alignment and shutdown margin will remain in effect to assure that the safety margins are maintained.
ENVIRONMENTAL CONSEQUENCES This waiver will not change the types of any effluents that may be released offsite, nor create a significant increase in individual or cumulative occupational radiation exposure.
The proposed changes do not affect the ability of the control rod
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- assemblies to perform their intended safety function when a safety system setting is reached. Therefore, the consequences of accidents related to or dependent on control rod assembly operation will remain unaffected.
The waiver of compliance was reviewed by the Station Nuclear Safety and Operating Committee. It has been determined that no unreviewed safety question or significant hazards consideration exists.
Very truly yours, q,P,~~~
Gi,rW. L. Stewart
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Senior Vice President - Nuclear cc: U. S. Nuclear Regulatory Commission Region II 101 Marietta Street, N. W.
Suite 2900 Atlanta, Georgia 30323 Mr. M. W. Branch NRC Senior Resident Inspector Surry Power Station