ML20198N608
| ML20198N608 | |
| Person / Time | |
|---|---|
| Site: | North Anna  |
| Issue date: | 10/28/1997 |
| From: | Ohanlon J VIRGINIA POWER (VIRGINIA ELECTRIC & POWER CO.) |
| To: | Reyes L NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II) |
| References | |
| 97-636, NUDOCS 9711060004 | |
| Download: ML20198N608 (5) | |
Text
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VeulNI A Ei.i:cTRIC ANI) POWI:M CONTI%NY RICllMONI), YlltGINI A 23261 october 28, 1997 Mr. Luis Reyes Serial No.:
97-636 Regional Administrator NL&OS/ETS R7 U. S. Nuclear Regulatory Commission Docket No.:
50-338 Region II License No.:
NPF-4 Atlanta Federal Center 61 Forsyth St., SW, Suite 23T85 Atlanta, Georgia 30303
Dear Mr. Reyes:
VIRGINIA ELECTRIC AND POWER COMPANY NORTH ANNA POWER STATION UNIT 1 EMERGENCY DIESEL GENERATOR REPAIRS REQUEST FOR ENFORCEMENT DISCRETICH Pursuant to 10 CFR Part 2, Appendix C, Virginia Electric and Power Company (Virginia 1
Power) requests the NRC to exercise enforcement discretion regarding compliance with Technical Specifications 3.8.1.1, Action b, Emergency Diesel Generator allowed outage time. The enforcement discretion will permit continued operation beyond the current 72 hour8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> allowed outage time for an inoperable Emergency Diesel Generator (EDG). During routine testing of the 1H Emergency Diesel Generator, the engine driven cooling fan catastrophically failed rendering the 1H EDG inoperable. Therefore, in order to avoid unnecessary plant transients (e.g., a plant shutdown and startup), Virginia Power is requesting enforcement discretion to permit continued operation of Unit 1 with the 1H EDG inoperable for up to seven days to repair and restore the EDG to operable status.
l)
DiscussiQD At 2018 hours0.0234 days <br />0.561 hours <br />0.00334 weeks <br />7.67849e-4 months <br /> on October 26,1997, during routine maintenance / testing of the 1H EDG a blade in the engine driven cooling fan catastrophically failed causing significant damage fb' J
to the remainder of the fan blades and the radiator. In order to retum the EDG to operable status, it is necessary to replace all of the fan blades and repair or replace several of the radiator sections. The extensive amount of work required to remove and replace interferences, replace all the fan blados, replace several of the radiator sections, and perform post maintenance testing will cause the physical maintenance activities to extend beyond the current 72 hour8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> allowed outage time. Therefore, we are requesting.
I one-time extension of the allowed outage time for the 1H EDG from 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> to seven days.
9711060004 971028 PDR ADOCK 05000339 P
.A review-of industry operating experience was pedormed to determine whether other plants with similar EDG's had experienced cooling fan blade failures.
The review determined that there were no similar failures for EDGs that were air cooled. The manufacturer was also contacted and they were not aware of _ any similar faiiures.
Virginia Power is currently periorming a root cause evaluation of the fan blade failure, it
-is currently believed that one fan blade failed and caused damage to the ciber fan blades. Additional evaluation and analysis are being performed to establish the root cause of the fan blade failure.
The enforcement discretion will permit the 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> allowed outage time to be extended to seven days. The extended allowed outage time will expire upon retuming the 1H EDG to operable status or on November 2,1997 at 2018 hours0.0234 days <br />0.561 hours <br />0.00334 weeks <br />7.67849e-4 months <br />, if the 1H EDG is not
- retumed to operable status during the above timeframes, North Anna Unit 1 will initiate a plant shutdown in accordance with Technical Specification 3.8.1.1 Action b. Adoption -
of the approved line-item improvements to the Technical Specifications or the improved
- Technical Specifications (ITS) would not have obviated the need for the enforcement discretion since the ITS allowed outage time for an EDG remains at 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />.
The compensatory measures, the justification for the duration of the request, the significant hazards consideration, and the evaluation' of the potential impact on'he environment are discussed in the following sections.
SAFETY IMPACT AND POTENTIAL CONSEQUENCES Continued operation during the one-time extended allowed outage time of the 1H EDG does not increase the probability of occurrence or the consequences of an accident or malfunction of equipment important to safety previously evaluated in the safety analysis report. The inoperability of an EDG does not affect the probability of any accident previously analyzed. During the one time extended allowed outage time for the 1H EDG, the remaining train of emergency-power (1J emergency bus) and emergency safeguards equipment-will remain operable to mitigate the consequences of.any previously analyzed accident. A single train of emergency safeguards equipment is adequate - to mitigate the consequences of any previously analyzed _ accident.
Furthermore, compensatory measures will ensure _ power -is available to the 1H emergency bus in the event of an accident or transient which requires emergency powering of the 1H bus.
~ The proposed one time extension of the Technical Specifications allowed outage time does not create the possibility of an accident or malfunction of a different type than any evaluated previously in the safety analysis report. The one-time extended allowed outage time of the 1H EDG does not cn. ate any new accident precursors, or limiting single failures. The UFSAR accidents are analyzed assuming that the EDG is the worst single failure. No new initiators result from the change. Therefore, it is concluded that no_new or different kind of accident from any previously evaluated has been created by the one-time extended allowed outage time for the 1H EDG.
y
O The.one time extended allowed outage time of the 1H EDG does not result in a reduction in margin of safety as defined in the basis for any Technical Specifications.
The compensatory measures provide additional assurance that power will be available for the 1H emergency bus in the event of an accident or transient which requires emergency powering of the 1H bus.
An explicit PSA model solution.was performed in accordance with the guidance
-contained in the PSA Applications Guide, EPRI TR 105396, which indicated an acceptable configuration risk for an increased allowed outage time. The increase in CDF for a one time seven day allowed outage time for the 1H EDG was less than the acceptance criterion. The On-Line Maintenance Configuration Matrix will be used to control the planned configurations entered while in this seven oay period.
COMPENSATORY MEASURES The following compensatory measures will be takers to provide additional assurance that the public health and safety will not be adversely affected by this enforcement discretion request.
During the extended outage time for the 1H EDG the following actions will be taken to ensure the 1H Emergency Bus can be powered if necessary to support safety equipment necessary to mitigate the consequences of an accident or transient:
l The Alternate A.C. Diesel Generator (AAC DG) will be operable and capable of being connected to the 1H Emergency Bus.
The opposite unit's EDGs will be maintained operable with the 2J EDG capable of being cross tied to the 1H Emergency Bus.
The Unit 1J EDG and emergency safeguards equipment will be maintained j-operable.
Switchyard / reserve station service transformer activities that could cause any unstable offsite or onsite power conditions will not be scheduled.
Refresher training will be provided to the control room operators responsible for restoring power to the 1H Emergency Bus using existing approved procedures.
SIGNIFICANT HAZARDS CONSIDERATION The proposed enforcement discretion for the Technical Specifications described above does not result in a significant hazards consideration as defined in 10 CFR 50.92.
Specifically, the proposed enforcement discretion does not:
1.
Involve a significant increase in the probability or consequences of an accident previously evaluated. The inoperability of an EDG does not affect the probability of any accident previously analyzed.
During the one-time extended allowed
l outage time for the 1H EDG, the-remainin'g train of emergency _ power-(1J
" emergency bus) and emergency safeguards squipment will remain operable to mitigate the consequences of any previously analyzed accident. A single train of -
emergency safeguards equipment is adequate to mitigate the consequences of--
i any previously analyzed accident. Fudhermore, the opposite unit's EDGs will be maintained operable with the 2J EDG capable of being cross tied to the 1H Emergency Bus. Therefore, the request does not involve a significant increase in the probability or _ consequences of an accident or malfunction previously evaluated.
2.
Create the possibility of a new or different kind of accident from-previously evaluated. The electrical distribution system will continue to_ be operated in the same manner. No new failure scenarios, transient precursors, or limiting single failures are introduced. A loss of an emergency bus is essumed in the accident analysis. There are no adverse affects or challenges imposed on any safety system as result of the extended allowed time. Therefore, the possibility of a new or different kind of accident is not created by the one time extended allowed-outage time for the 1H EDG.
3.
Involve a significant reduction in the margin of safety. The opposite train of emergency power (1J emergency bus) and the associated engineered safety l
equipment remain operable to mitigate the consequences of any previously l'
analyzed accident. Funbermore, the compensatory measures provide additional assurance that power will be available to power the 1H emergency bus in the event of an-accident or transient. Therefore, the one time extended allowed outage time for the 1H EDG does not result in a significant reduction in the margin of safety.
ENVIRONMENTAL CONSEQUENCES The proposed enforcement discretion meets the 10 CFR 51.22(c)(9) eligibility criteria j
for categorical exclusion as specified below:
As specified above this request does not involve a significant hazards considerations.
. The proposed enforcement discretion does not change the types of any effluents that may be released offsite, nor create a significant increase in individual or cumulative-occupational radiation exposure. Operation of the plant is not being changed in any way to effect the amounts of affluents or create new types of effluents. The proposed enforcement discretion only extends existing action statement to affect repair of the 1H EDG. The redundant train of emergency-power and train of safety equipment is adequate to mitigate the consequence of an accident. Thus, the consequences of any analyzed accidents are not increased by the extended allowed outage time of the 1H EDG.
d A
.The request does not adversely impact the operation of the reactor, and does not affect
' any system that would affect occupational radiation exposure. The proposed one time extended allowed outage time for the 1H EDG was not create additional exposure to personnel nor affect the levels of radiation present in the plant.
Based on the above, it is concluded that there will be no impact on the environment resulting from the proposed one time extended allowed outage time for the 1H EDG, and that the request meets the criteria of 10 CFR 51.22 for categorical exclusion from the requirements of 10 CFR 51.21 relative to requiring a specific environmental assessment by the Commisuion.
CONCLUSION l
This enforcement discretion was reviewed and approved by the Station Nuclear Safety and Operating Committee. It has been determined that no unreviewed safety question
- or significant hazards consideration exists.
On October 28,1997, by telephone conference calls between our staffs, we requested enforcement discretion to extend the allowed outage time of Technical Specification 3.8.1.1.b from 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> to seven days. This enforcement discretion, if granted, will expire upon retuming the 1H EDG to operable status or at 2018 hours0.0234 days <br />0.561 hours <br />0.00334 weeks <br />7.67849e-4 months <br /> on November 2, 1997, whichever is first.
4 Should you have any questions, please contact us.
Very truly yours, y11AG i
James P. O'Hanlon i
Senior Vice President - Nuclear cc: % U. S. Nuclear Regulatory Commission Attention: Document Control Desk Washington, DC. 20555 Mr. M. J. Morgan l
NRC Senior Resident inspector North Anna Power Station 1
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