ML20091P689
| ML20091P689 | |
| Person / Time | |
|---|---|
| Site: | Prairie Island  |
| Issue date: | 01/29/1992 |
| From: | Parker T NORTHERN STATES POWER CO. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| REF-GTECI-048, REF-GTECI-049, REF-GTECI-NI, TASK-A-48, TASK-A-49, TASK-OR GL-91-11, NUDOCS 9202030250 | |
| Download: ML20091P689 (4) | |
Text
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Northan States Power Company 414 Nicollet Mall Minneapohs, Minnesota $54011927 Telephone (612) 330-5500 January 29, 1992 U S Nuclear Regulatory Commission 10 CFR Part 50 Attn:
Document Control Desk Section 50.54(f)
Washington, DC 20555 PRAIRIE ISIAND NUCLEAR GENERATING PIANT Docket Nos. 50 282 License Nos. DPR 42 50 306 DPR-60 Response to Generic Letter 91-11, " Resolution of Generic Issues 48, 'LCOs for Class 1E Vital Instrument Buses', and 49, ' Interlocks and LCOs for Class 1E Tie Breakers' Pursuant to 10 CFR 50.54(f)"
This letter is provided in response to Generic Letter 91-11, " Resolution of Generic Issues 48, 'LCOs for Class 1E Vital Instrument Buses', and 49,
' Interlocks and LCOs for Class lE Tie breakers' Pursuant to 10 CFR 50.54(f)"
As recommended by Enclosure 1 to the Generic Letter, a review was conducted of the Prairie Island Nuclear Generating Plant vital instrument buses, their power supplies, and their associated procedures and instructions.
A summary of the results of this review is provided as Attachment 1 to this letter.
Please contact us if you have ary questions related to our response.
/
M homas M Parker Manager Nuclear Support Services c: Regional Administrator - Region III, NRC Senior Resident Inspector, NRC l
NRR Project Manager, NRC J E Silberg l
Attachments: Affidavit l - Generic Letter 91-11 Response
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PDR ADOCK 05000282 p
UNITED STATES NUCLEAR REGULATORY COMMISSION NORTHERN STATES POWER COMPANY PRAIRIE ISLAND NUCLEAR GENERATING PLANT DOCKET No. 50 282 50-306 Response to Generic Letter 91-11, "Rnsolution of Generic Issues 48, 'LCOs for Clasr 1E Vital Instrument Buses', and 49, ' Interlocks and LCOs for Class lE Tie Breakers' Pursuant to 10 CFR 50.54(f)"
Northern States Power Con.pany, a Minnesota corpcration, with this letter is submitting information requested by NRC Ceneric Letter 91-11, " Resolution of Generic Issues 48, 'LCOs for Class 16 Vital Instrument Buses', and 49,
' Interlocks and LCOs for Class lE Tie Breakers' Pursuant to 10 CFR 50,54(f)'
The rerults of our review of the recormendations contained in Enclosure 1 to the Generic Letter are included as Attachment 1 to this submittal, This letter contains no restricted or other defense information.
NORTHERN STATES f0WER COMPANY i
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DNo I& w By 'Themas M Parker Manager, Nuclear Support Services Onthisp?7 ay of AruAAA#
/f74beforemeanotarypublicinandforsaid County, personally @ppeared/ThomasMParker, Manager,NuclearSupport Services, and being first duly sworn acknowledged that he is authorized to execute this document on behalf of Northern States Power Company, that he knows the contents thereof, and that to the best of his knowledge, information, and belief the statements made in it are true and that it is not interposed for delay, PiJL._
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MARCIA K LaCORE NOTARY PUBLIC-M!NNESOTA HENNEPIN COUNTY My Commeston Exp:rn Sept 24,1%3 a W:::::::. :::::::::::::::::.WNN
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1 RESPONSE TO NRC CENERIC LETTER 91-11 The results of our review of the recommendations contained in Enclosure 1 to Osneric Letcer 91-11 are summarized below:
1 Generic Letter 91-11 Recommended Action Ensure that your plant has procedures that include time 11mitations and survelliance requirements for:
1.
Vital instrument buses (typically 120V ac buses),
Results of Review:
a.
Time Limitations Prairie Island Tech Specs allow no more than one vital instrument bus to be powered by an alternate source or its associated instrument inverter bypass source.
b.
Surveillance Requirements - Weekly surveillance procedures have been implemented to verify the operability and correct configuration of the vital instrument buses.
2.
Inverters or other onsite power sources to the vital instrument buses, and Results of Review a.
Time Limitations - New adminstrative controls limit the maximum time an instrument inverter should be out of service while the associated unit-is above cold shutdown to 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />. Only one instrument inverter should be out of service at a time, A second inverter supplying a vital instrumelt bus may be powered-from an inverter bypass source for 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br />.
-b.
Surveillance Requirements keekly surveillance procedures have been implemented to verify the operability and correct configuration of the inverters and instrument buses.
3.
Tie breakers that can connecc redundant class 1E buses at one unit or that can connect class 1E buses between units at the same site.
Results of Review:
120VAC and DC Buses The 120VAC and DC buses at Prairie Island are'not configured with bus ties.
48Qy Buses Bus ties et the 480V level are between the opposite trains of the same unit ano normally only used during cold shutdown.
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Attachtwnt 1 January 29, 1992 Page 2 of 2 The 480VAC bus ties will be eliminated when the Station Black Out /
Electrical Safeguards Upgrade (SB0/ESU) modification is complete in 1994.
a.
Time 1. imitations Prairie Island administrative controls specifies an 8 hour9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> limit on 480V bus tie closed time when the unit is above 200* F.
b.
Surveillance Requirements Weekly surveillance procedures have been implemented to ensure correct breaker alignment and indicated voltage on the 480V buses, Other 480V Concerns Group B pressurizer heaters' sources are switchable between a safeguards bus and a non safeguards bus, Procedure C20.6 requires both breakers supplying the group B pressurizer heaters be opened before a transfer is made, Therefore, the' transfer of the heaters is an administrative break-before-make transfer.
The supply breakers to motor control centers 1T1 and IT2 can be switched from one unit to the other. These breakers are interlocked to only allow a break before make transfer, The break-before-make configuration prevents these load breakers from becoming a bus tie, 4.16~KV Buses 4,16 KV bus ties exist between the same trains of the opposite units and
-are used in the automatic voltage restoration scheme.
This configuration
- has been evaluated by the Updated Safety Analysis Report section 8.3 which states;that "in the extremely remote case of a bus tie breaker failure
- resulting in loss:of the two associated buses, the engineered safety features on the remaining buses are sufficient for safe shutdown of either unit,"
- a, Time-Limitations - There are no time limitations per the' Updated Safety Analysis Report discussion reference above.
b.
Surveillance-Requirements - Weekly surveillance procedures will be implemented by April 30, 1992 to ensure correct breaker alignment and
- indicated voltage on the 4,16 KV. buses.
- After.the SB0/ESU modification, the 4,16 KV bus ties will be manually operated only (no longer closed as part of the-voltage restoration scheme),-and-under administrative control.
In addition, there will be two breakers per bus tie, i
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