ML19345E256
| ML19345E256 | |
| Person / Time | |
|---|---|
| Site: | Browns Ferry  |
| Issue date: | 12/02/1980 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML19345E252 | List: |
| References | |
| NUDOCS 8012230519 | |
| Download: ML19345E256 (5) | |
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UNITED STATES
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SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION SUPPORTING AMENDMENT NO.63 TO FACILITY OPERATING LICENSE NO. CPR 33 AMENDMENT NO.59 TO FACILITY OPERATING LICENSE NO. DPR-52 AMENDMENT NO.35 TO FACILITY OPERATING LICENSE NO. DPR-68 TENNESSEE VALLEY AUTHORITY BROWNS FERRY NUCLEAR PLANT, UNITS N05. 1, 2 AND 3 DOCKET NOS. 50-259, 50-260 AND 50-296 1.0 Introduction By letter dated August 6,1980, the Tennessee Valley Authority (the licensee or TVA) requested amendments to Facility Operating License Nos. OPR-33, DPR-52 and DPR-68 for the Browns Ferry Nuclear Plant, Units Nos. 1, 2 and 3.
The proposed amendments resolve ambiguities which exist in the auxiliary electrical system technical specifications.
2.0 Discussion The Browns Ferry Plant is connected into the TVA system network by six 500-kV lines.
Normal station power is from station service transformers connected to the generator leads of each unit.
Startup power is from the TVA 161-kV system network through 161-to 4.16-kV stepdown transformers.
The 161-kV switchyard is supplied by two transmission lines from the 161-kV system network. One line comes in from the northeast from the Athens l
substation; the other line comes in from the south across Wheeler Reservoir from the Trinity substation. The 500-kV system is interconnected with the 161-kV system at various points, including two lines to the Trinity i
substation. The standby source of auxiliary power is from eight diesel-driven generators.
Auxiliary power is supplied from two sources:
either the unit station tran3 formers or from the 161-kV transmission system through the common station transformers or the cooling tower transformers.
The normal power source for unit auxiliaries is the 20.7-to 4.16-kV unit station service transformer, which is connected to each unit generator's output leads.
The startup and alternate power source for unit auxiliaries is either of two 161-to 4.16-kV common station service transformers which are fed from the TVA 161-kV system.
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The normal power source for station common auxiliaries is either or both of the two common station service transformers.
Two of the unit station SS V
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. service transformers also serve as alternate sources for station common auxiliaries.
The alternate sources to the shutdown auxiliary power system buses are the 161-to 4.16-kV common station service and cooling tower transformers. Any of the three 20.7-to 4.16-kV unit station service transformers may also serve the shutdown auxiliary power system buses, and two of these unit transformers will serve as normal sources to these buses.
The diesel generators serve as backup sources to the shutdown auxiliary power system boards.
Both common station service transformers in service are capable of continu-ously carrying the load consisting of.the station common auxiliaries, plus all auxiliaries of one generating unit operating at full load without its unit station service transformer, plus all auxiliaries of another unit either in the starting mode, the shutdown mode, or the accident mode.
Only one common station service transformer in service is capable of continuously carrying the load consisting of the station common auxiliaries, plus either (1) all auxiliaries of one generating unit in the starting mode or (2) all auxiliaries of one generating unit in the accident made and two generating units in the shutdown mode.
In May 1978, TVA made various modifications to the inplant electrical systems to improve inplant voltages including a) installation of capacitor banks at the Browns Ferry terminal ends of the two 161-kV transmission lines to improve the power factor and b) rearranging the 4160-volt loads of Unit 3 to reduce the voltage drop due to high impedance in the common station service transformers.
The latter included cutting Unit 3 boards 3A, 38 and 3C off the start bus 1A and 18 and supplying them from cooling tower transformers 1 and 2.
These electrical modifications were approved by Amendments No. 39, 37, and 13 to Licenses DPR-33, OPR-52, and DPR-68, respectively.
The staff's safety evaluation for these amendments discusses these modifications; since these modifications are pertinent to the administrative changes requested by TVA's letter of August 6, 1980, the safety evaluation related to Amendments 39, 37 and 13 is incorporated herein by reference.
3.0 Evaluation TVA's stated purpose in requesting the proposed changes is to resolve ambiguities which exist in the auxiliary electrical system technical specifications. The Limiting Conditions for Operation (LCO) and Surveil-
-lance Requirements on the Auxiliary Electrical System are covered in Sections 3.9 and 4.9 of the Technical Specifications.
Each of the proposed changes and our evaluation thereof is discussed separately below, a.
For Units 1 and 2, TVA proposes to delete from Section 3.9.A (p.
292) the words:
' and one cooling tower transformer" from the list of equipment that must be operable before either Units 1 or 2 can be started up.
Only Unit 3 is fed from the cooling tower transformers.
This requirement was added when the same wording was used for all three units with Amendment Nos. 39, 37, and 13.
The cooling tower transformers are not needed for Unit 1 and 2 operation except in
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. degraded conditions and the deletion from the Unit 1 and 2 requirements is acceptable.
b.
For Units 1 and 2, TVA proposes to add to Section 3.9.A.4 (p. 293) the requirements that the Units 1 and 2 Diesel Auxiliary Boards and Shutdown Buses 1 and 2 are energized prior to startup of the units.
Shutdown buses and diesel auxiliary boards are necessary for opera-tion of the onsite and offsite power system. We conclude the addi-tional requirements are desirable and acceptable.
c.
For Units 1 and 2, TVA proposes to delete the requirement from Section 3.9.8.1 (p. 295) that a cooling tower transformer and its 4-kV bus tie board be operable when Unit 1 or 2 are in the startup or run mode for the same reason as in a, above.
TVA is proposing to add a requirement that if the 4-kV bus tie board becomes inoperable, continued reactor operation is permissible for 30 days provided both common station service transformers are energized and checked daily.
The bus tie board is needed primarily in the event a common transformer is removed from service. We find the proposed changes acceptable.
Because of the added requirement, the numbering on former LCO and Surveillance Requirements 3.9.B.2 and 3.9.B.3 is changed to 3.9.B.3 and 3.9.B.4, respectively.
d.
For Units 1 and 2, TVA is proposing to add requirements to Section 3.9.8 (p. 296) to specify a limit for how long reactor operation is permis-sible (i.e., 7 and 5 days, respectively), when one of the 4-kV shutdown buses is inoperable or one of the 480-V diesel auxiliary boards becomes inoperable, provided all diesel generators are proven operable immediately and daily thereafter and the remaining diesel auxiliary board is demonstrated to be operable.
The times specified are considered reasonable for maintenance and testing of the equipment.
We conclude that the proposed changes are acceptable.
Because of the added requirements, there is a renumbering of the remaining LCOs and Surveillance Requirements.
e.
For Units 1 and 2, TVA is proposing to add requirements to Section 3.9.8 (p. 297) to specify that reactor operation is permissible for a period of 7 and 5 days, respectively, if.the undervoltage relays on the 1A or 18 start bus become inoperable or if the undervoltage relays on a shutdown board become inoperable, provided the other start bus and shutdown boards and associated undervoltage relays are operable. We find the proposed changes acceptable.
f.
For Unit 3, Section 3.9.A.4.a (p. 320) of the present Technical l
Specifications requires that start buses.1A and 18 be energized for l
the reactor to be brought critical. There are four start buses - 1A 18, 2A and 28.
The normal souce of power to the A buses is common station service transformer A; the normal source of power to the B buses is common station service transformer B.
However, alternatively, either set of buses may also be fed from the other transformer.
TVA i
l proposes to change this requirement to read "Both start buses to I
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, Unit 3 be energized" rather than just 1A and 18.
Since two start buses are adequate and these two could be 2A and 2B as well as 1A and IB, we find the proposed change acceptable.
g.
For Unit 3, TVA is proposing to add a requirement to Section 3.9.A.4 that the 480-V diesel auxiliary boards are energized prior to startup of the unit.
Since the diesel auxiliary boards are necessary for operation of the onsite and offsite power system, the proposed change is desirable and acceptable.
h.
For Unit 3, TVA is proposing to add a provision that the 4-kV bus tie or a Unit 3 start bus may be inoperable for 7 days, provided both 161-kV lines, both cooling tower transformers and the Unit 3 diesel generator are demonstrated to be operable.
The 4-kV bus tie board provides the shutdown boards with backup access to the offsite power system through either cooling tower transformer.
The cooling tower transformers supply more than the bus tie board; thdy also supply power to the unit boards. We conclude that the proposed change is acceptable.
i.
For Unit 3, TVA is proposing to add a new requirement (Section 3.9.B.5,
- p. 324) specifying a limit of 5 days that one of.the diesel auxiliary boards may be out of service for maintenance and testing, provided the remaining diesel auxiliary board and each Unit 3 diesel are verified to be operable.
This is the same as proposed for Units 1 and 2 in d, above, and is acceptable.
j.
For Unit 3, TVA is proposing to add two requirements (Section 3.9.B.8 and 3.9.8.9, p. 325a) similar to the proposed changes for Units 1 and 2 in e, above, specifying a limit on the time the undervoltage relays may be inoperable for maintenance and testing and specifying-the backup equipment that must be available. We conclude that the proposed changes are acceptable.
In summary, we have reviewed the proposed changes to the auxiliary elec-trical system technical specifications both individually and collectively and conclude they are acceptable.
4.0 Environmental Considerations
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We have determined that the amendments do not authorize a change in effluent types or total amounts nor an increase in power level and will not result in any significant environmental impact.
Having made this determination, we have further concluded that the amendments involve an action which is-insignificant from the standpoint of environmental impact and pursuant to 10 CFR 51.5(d)(4) that an environmental impact statement or negative declaration and environmental impact appraisal need not be prepared in connection with the issuance of the amendments.
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1 5-5.0 Conclusion
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We have concluded, based on the considerations discussed above, that:
(1) because the amendments do not involve a significant increase in the probability or consequences of accidents previously considered ~
and do not involve a significant decrease in a -safety margin, the 4
amendments do not involve a significant hazards consideration, (2) there is reasonable assurance that the health and safety of the public will not be endangered by operation in the proposed manner, and-(3) such activities will be conducted in compliance with the
- Commission's regulations, and the issuance of_these amendments will not be inimical to the common defense and security or to the health and safety of the public.
Da ted: December 2,1980 o
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