ML18026A851
| ML18026A851 | |
| Person / Time | |
|---|---|
| Site: | Browns Ferry  |
| Issue date: | 01/06/1984 |
| From: | Vassallo D Office of Nuclear Reactor Regulation |
| To: | Parris H TENNESSEE VALLEY AUTHORITY |
| References | |
| NUDOCS 8401310465 | |
| Download: ML18026A851 (5) | |
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January 6,
1984 Docket Nos. 50-259/260/296 Mr. Hugh G. Parris Manager of Power Tennessee Valley Authority 500 A Chestnut Street, Tower II Chattanooga, Tennessee 37401
Dear Mr. Parris:
DISTRIBUTION:I Docket File~
NRC PDR ORB¹2 Reading LPDR DEisenhut EJordan OELD RClark SNorris NSIC JTaylor ACRS(10)
Gray
Subject:
Adequacy of Station Electric Distribution System Voltages-Verification Testing Re:
Browns Ferry Nuclear Plant, Units 1, 2, and 3
Your letter of July 22, 1983 provided the results of the verification tests which we required as part of our approval of the modified electrical distri-bution system for the Browns Ferry Nuclear Plant.
In response to several conference calls with your staff, you provided additional information on the verification tests by your letter of September 22, 1983.
As discussed in the enclosure, our review indicates that there could be a potential over-voltage condition under some conditions when using the backup 161 KV offsite power source.
You are requested to review this potential overvoltage condition.
Within 45 days of receipt of this letter, please provide your assessment of the inplant voltages, a discussion of the general approach you plan to follow to resolve this potential condition and an estimate of when you expect to submit design information on any proposed modifications.
This request for additional information is specific to one licensee.
The reporting and/or recordkeeping requirements contained in this letter effect fewer than ten respondents; therefore OMB cleareance is not required under P.L.96-511.
Sincerely, Original signed by/
Domenic B. Vassallo, Chief Operating Reactors Branch ¹2 Division of Licensing
Enclosure:
As stated cc w/enclosure:
See nex page
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Mr. Hugh G. Parris Tennessee Valley Authority Browns Ferry Nuclear Plant, Units 1, 2 and 3
CC:
H. S. Sanger, Jr., Esquire General Counsel Tennessee Valley Authority 400 Commerce Avenue E 11B 330 Knoxvi 1 1 e, Tennessee 37902 Mr. Ron Rogers Tennessee Valley Authority 400 Chestnut Street, Tower II Chattanooga, Tennessee 37401 Mr. Charles R. Christopher
- Chairman, Limestone County Commission Post Office Box 188
- Athens, Alabama 35611 U. S. Environmental Protection Agency Region IV Office Regional Radiation Representative 345 Courtland Street, N.
W.
Atlanta, Georgia 30308 Resident Inspector U. S. Nuclear Regulatory Commission Route 2, Box 311
- Athens, Alabama 35611 Mr. Donald L. Williams, Jr.
Tennessee Valley Authority.
400 West Summit HilT Drive,,W10885 Knoxville, Tennessee 37902 Ira L. Myers, M. D.
State Health Officer State Department of Public Health State Office Building Montgomery, Alabama 36130 Mr. H.
N. Culver 249A HBD 400 Commerce Avenue Tennessee Valley Authority Knoxville, Tennessee 37902 George Jones Tennessee Valley Authority Post Office Box 2000
- Decatur, Alabama 35602 Mr. Oliver Havens U. S. Nuclear Regulatory Commission Reactor Training Center Osborne Office Center, Suite 200 Chattanooga, Tennessee 37411 James P. O'Reilly Regional Administrator Region II Office U. S. Nuclear Regulatory Commission 101 Marietta Street, Suite 3100 Atlanta, Georgia 30303
ENCLOSURE Request for Additiona1 Infor mat i on Adequacy of Station Electric Distribution System Voltages Verification Testing Browns Ferry Nuclear Plant Docket Nos. 50-259, 260 and 50-296
REFERENCES:
1.
NRC Letter, W. Gammill to All Power Reactor Licensees, "Adequacy of Station Electric Distribution System Voltages,"
August 8, 1979 2.
TVA Letter, L. M. Mills to H.
R. Denton, April 9, 1981 3.
TVA Letter, D. S.
Kammer to H. R. Denton, July 22, 1983 4.
TVA Letter, L. M. Hills to H.
R. Denton, September 22, 1983 Reference 1 requested TYA to provide station voltage analysis and tests to verify the accuracy of the analysis.
Review of your voltage analysis indicates that when power to 480V shutdown buses is provided via the 161 KY transmission
- system, the associated safety equipment supplied by these buses could be subjected to voltages as high as 115%, which is 5X over the manufacturer's 110Ã recommended maximum voltage.
Reference 2 indicates that in order for an overvoltage to occur at the 480V safety related
- buses, the following three conditions must be present:
1 - 161 KV transmission system to be the source of power to the Class 1E equipment.
TYA In Reference 2 state this condition occurs only 5X of the time.
2 - Station to be lightly loaded.
3 - 161 KV switchyard to be at its expected maximum voltage of 170 KV.
References 3 and 4 provide the results of the verification test.
The test results are higher by as much as 3X than the calculated values.
In addition the test results show that when the 480Y shutdown buses are loaded to a minimum of 30% and supplied by the 161 KV transmission system at a voltage of 166 KV (which is less than the maximum expected voltage of 170 KV), the 480V safety equipment experienced 115% voltage.
This is not totally in conformance with the above three conditions that must be present for an overvoltage condition at the 480V buses.
With the 161 KV transmission system at the maximum voltage of 170 KV the overvoltage at the safety related buses would be higher and have potential to cause damage to the 480V safety equipment.
This is not acceptable.
You are requested to review the potential overvoltage condition that could exist at the 480V safety related buses when these buses are supplied by the 161 KY transmission system and implement modifications as appropriate to correct this situation.
Provide a description of method of correcting this potential overvoltage condition for our review and approval.
In addition we request that you provide documentation indicating the voltage recorded during the test for shutdown board 1B when voltage at shutdown board C is at 4.4 KV.
This information was provided during a telephone conference on October 11, 1983, however, it was not included in References 3 and 4.
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