ML20247K813
| ML20247K813 | |
| Person / Time | |
|---|---|
| Site: | Oconee  |
| Issue date: | 09/12/1989 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML16138A673 | List: |
| References | |
| NUDOCS 8909220023 | |
| Download: ML20247K813 (3) | |
Text
r
..)
1
[
o, UNITED STATES 8"
t NUCLEAR REGULATORY COMMISSION 74 E
tTASHINGTON, D. C. 20555
%.....)
SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO AMENDMENT NO. 175TO FACILITY OPERATING LICENSE DPR-38 AMENDMENT N0.175 TO FACILITY OPERATING LICENSE DPR-47 AMENDMENT NO.172TO FACILITY OPERATING LICENSE DPR-55 DUKE POWER COMPANY OCONEE NUCLEAR STATION, UNITS 1, 2 AND 3 DOCKET NOS..50-269, 50-270 AND 50-287
1.0 INTRODUCTION
Duke Power Company is implementing a program to replace the power circuit breakers (PCB) in the 230 kV switchyard to upgrade the fault current interrup-tion capability of the PCBs.
PCB-9, which is required for the operability of the overhead emergency power path per Technical Specification (TS) 3.7.1(b)(2),
is included in this program.
The existing TS allows an outage time of 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> for inoperability of PCB-9.
To modify the PCB, the overhead emergency power path would have to be inoperable for 10 days, requiring the shutdown of all three Oconee Units for 10 days. By letter dated June 9,1989, Duke submitted a proposal to anend TS 3.7.8 to allow a one-time outage of 10 days to change out PCB-9.
The purpose of the Oconee 230 kV switchyard is to provide a reliable interface between Oconee Generating Station, Units 1 and 2, and the 230 kV Duke transmission line network. The switchyard provides multiple connections for distributing power from Oconee Units 1 and 2 to the 230 kV transmission lines and for feeding power to the unit auxiliary loads during the unit startups or shutdowns.
The switchyard has 24 PCBs which are used for operation and protection. Each PCB is provided with two separate tripping circuits / coils for redundant tripping operation.
When an abnormal power condition is detected by protective relays and removal of the line or bus experiencing a fault is necessary, the protective relaying circuit will energize the tripping coil (s) to the trip breaker. Each PCB has a l
closing coil circuit that is connected to the relaying scheme.
This allows operation to be initiated remotely from the control room and supervised by the protective relay scheme.
Currently, the PCBs have an interrupting current rating of 43 kA. The replacement PCB will have a rating of 67.5 kA.
Qf2hkb P
_.dh l
1 L
' 2.0 EVALUATION The risk associated with the inoperability of the overhead emergency' power path for longer than 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> has been previously reviewed by the staff and found acceptable (Amendments 117,117, and 114, dated November 22, 1982, to Facility.
Operating Licenses DPR-38, DPR-47, and DPR-55).
Specifically, TS 3.7.8 establishes a 28 day special inoperability period for the overhead emergency power path due to Keowee Main Step-up Transformer unavailability. The following restrictions are included within TS 3.7.8.
(a) Prior to heating the reactor above 200 degrees F or prior to the restart of the shutdown reactor or within 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> of the loss of the Keowee Maih Step-up Transformer, the 4160 volt standby buses shall be energized by a Lee gas turbine through the 100 kV circuit. The Lee gas turbine and 100 kV transmission circuit shall be electrically separate from the system grid and offsite and non-safety related loads.
(b) A Keowee hydro unit shall be cc;inected to the underground feeder circuit and this path shall be verified operable within 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> and weekly thereafter.
(c) The remaining Keowee Hydro Unit shall be available to the underground feed circuit.
~
(d) Operating in this mode is restricted to periods not to exceed 28 days, and the provisions of this specification may be utilized without prior NRC approval. The U.S. NRC Regional Office, Region II, will be notified within 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />.
The proposed amendment will expand the scope of TS 3.7.8 on a one-time basis to allow inoperability of the overhead energency path due to PCB-9 unavailability for 10 days.
Although the extension of the inoperable period for PCB-9 may involve an increase in the probability of previously analyzed accidents, the consequences of the accidents are within the bounds of FSAR analyses.
Upon implementation of the modification, the probability of previously analyzed accidents will be reduced due to the increased fault current interrupting capability of PCB-9 concurrent with the reduced probability of a unit separation from the system grid.
Modifications to the electrical system and the supporting operating procedures have assured the adequacy of both the Keowee underground emergency power path and the Lee 100 kV circuit to supply the emergency power requirements for the three Oconee Units. Therefore, the staff finds the proposed changes to the Oconee TS are acceptable.
i
j I
. i i
3.0 ENVIRONMENTAL CONSIDERATION
l Pursuant to 10 CFR 51.21, 51.32, and 51.35 an environmental assessment and finding of no significant impact has been prepared and published in the Federal Register (54 FR 37514) on sept. 11
, 1989. Based upon the' environmental assessment, the Commission has determined that issuing these amendments will have no significant effect on the quality of the human environment.
4.0 CONCLUSION
i The Commission made a proposed determination that the amendments involve no significant hazards consideration which was published in the Federal Register (54 FR 29405) on July 12, 1989, and consulted with the state of South Carolina.
No public comments were received, and the state of South Carolina did not have any comments.
We have concluded, based on the considerations discussed above, that-(1) there is reasonable assurance that the health and safety of the public will l
not be endangered by operation in the proposed manner, and (2) such activities l
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.
.j Principal Contributors:
L. Wiens, PD#11-3/DRP-I/II l
S. Brewer, PD#II-3/DRP-I/II Dated:
September 12, 1989 i
i 4
i l
)
I i
i i
l l
_ _ - _ _ _ _ _ _ _ _ _ _ _ _ _ _ - _ _ _ _ _ _ _