ML18038B549
| ML18038B549 | |
| Person / Time | |
|---|---|
| Site: | Browns Ferry  |
| Issue date: | 11/15/1995 |
| From: | NRC (Affiliation Not Assigned) |
| To: | |
| Shared Package | |
| ML18038B547 | List: |
| References | |
| NUDOCS 9511200147 | |
| Download: ML18038B549 (4) | |
Text
REVISED APPENDIX R SAFE SHUTDOWN SAFETY EVALUATIONREPORT PAGE 14 ENCLOSURE qsiig00i47 95iii5 PDR ADQCK 05000260 PDR
this concern (i.e.,
manual operator actions to shed nonessential loads) is no longer necessary.
The licensee restated this approach (ensuring adequacy of main breaker margin) in the SSA that is the subject of this SE, which stated that the occurrence of high impedance faults that may be initiated as a result of fire damage to connected load circuits was considered during the evaluation of common power source associated
- circuits, and based on the results of this evaluation, it was concluded that sufficient margin exists in the trip point setting of the main breakers of potentially affected supplies to preclude a trip as a result of such faults.
However, the licensee did not describe the basic assumptions used in performing the analysis of this concern.
Specifically, the staff could not determine if the evaluation was performed in accordance with the criteria specified in NRC Generic Letter (GL) 86-10, which requires consideration of multiple, simultaneous, faults.
By letter dated October 5, 1995, the licensee submitted additional information regarding the high impedance faults.
BFN is divided into 34 fire zones.
Depending on the specific location of the fire, either HPCI, RCIC, or LPCI will be used to achieve and maintain shutdown conditions in the reactor.
For each
- system, the licensee has performed an analysis to ensure that time-dependent loads will not be lost due to multiple high impedance faults (MHIF) >
3.7.2.1 HPCI and RCIC Systems The licensee stated that neither the HPCI nor the RCIC systems power time-critical loads.
Should MHIFs result in the loss of a required source of electrical power associated with these
- systems, the operator would have approximately 20 minutes to clear the affected board, re-establish the required electrical alignment, and re-initiate the HPCI or RCIC system.
Therefore, for those areas where HPCI or RCIC is available, the licensee has determined that there is adequate time to restore any boards or panels lost due to a MHIF current condition.
All operator actions necessary to restore the operation of affected power sources will be governed by written procedures.
3.7.2.2 LPCI System Unlike the HPCI and RCIC systems, the time required to restore the operability of power supplies associated with the LPCI system may be critical.
To address this concern, the licensee has performed additional analyses for the 14 fire areas/zones requiring LPCI for safe shutdown.
This analysis considered MHIFs on all required and non-required loads routed in the fire area, and verified that the total MHIF current from these loads will not affect the board/panel feeder breaker at the 60 second trip rating.
This approach (i.e.,
use of the 60 second trip current rating) reduces the number of manual actions that may otherwise be required.
For power supplies which power time-critical loads, the licensee intends to reduce the electrical loading on specific boards and panels (i.e., non-essential load shedding) in the event of a fire.
Mr. Oliver D. Kingsley, Jr.
Tennessee Valley Authority BROWNS FERRY NUCLEAR PLANT CC:
Hr. 0. J. Zeringue, Sr. Vice President Nuclear Operations Tennessee Valley Authority 3B Lookout Place 1101 Market Street Chattanooga, TN 37402-2801 Dr. Hark 0. Hedford, Vice President Engineering
& Technical Services Tennessee Valley Authority 3B Lookout Place 1101 Market Street Chattanooga, TN 37402-2801 Mr. D.
E.
Nunn, Vice President New Plant Completion Tennessee Valley Authority 3B Lookout Place 1101 Market Street Chattanooga, TN 37402-2801 Hr.
R.
D. Machon, Site Vice President Browns Ferry Nuclear Plant Tennessee Valley Authority P.O.
Box 2000
- Decatur, AL 35602 General Counsel Tennessee Valley Authority ET llH 400 West Summit Hill Drive Knoxville, TN 37902 Hr.
P.
P. Carier, Manager Corporate Licensing Tennessee Valley Authority 4G Blue Ridge 1101 Market Street Chattanooga, TN 37402-2801 Hr. T.
D. Shriver Nuclear Assurance and Licensing Browns Ferry Nuclear Plant Tennessee Valley Authority P.O.
Box 2000
.Valley Authority P.O.
Box 2000
- Decatur, AL 35602 TVA Representative Tennessee Valley Authority 11921 Rockville Pike, Suite 402 Rockville, HD 20852 Regional Administrator U.S. Nuclear Regulatory Commission Region II 101 Marietta Street, NW., Suite 2900
- Atlanta, GA 30323 Mr. Leonard D. Wert Senior Resident Inspector Browns Ferry Nuclear Plant U.S. Nuclear Regulatory Commission 10833 Shaw Road
- Athens, AL 35611 Chairman Limestone County Commission 310 West Washington Street
- Athens, AL 35611 State Health Officer Alabama Department of Public Health 434 Monroe Street Montgomery, AL 36130-1701
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