ML20091K143
| ML20091K143 | |
| Person / Time | |
|---|---|
| Site: | Sequoyah  |
| Issue date: | 01/14/1992 |
| From: | Joshua Wilson TENNESSEE VALLEY AUTHORITY |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| REF-GTECI-048, REF-GTECI-049, REF-GTECI-NI, TASK-048, TASK-049, TASK-48, TASK-49, TASK-OR GL-91-11, NUDOCS 9201220164 | |
| Download: ML20091K143 (6) | |
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January 14, 1992 U.S. Nuclear Regulatory Commission ATTN Document Control Desk Washington, D.C. 20555 Centlement In the Matter of
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Docket Nos. 50-327 Tennessee Valley Authority
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50-328 SEQUOYAH NUCLEAR PLANT (SQN) - GENERIC LETTER (GL) 91-11, RESOLUTION OF CENERIC ISSUES (GI) 48, "LCOs FOR CLASS 1E VITAL IliSTRUMENT BUSES." AND 49,
" INTERLOCKS AND LCOs FOR CLASS 1E TIE BREAKERS." PURSUANT TO 10 CFR 50.54(f)
This letter provides SQN's response to the subject CL.
The attached enclosure t
provides a brief-system description and the administrative controls in place to address the concerns described in the GL.
If you have any questions concerning this issue, please contact W. C. Ludwig at (615) 751-7460.
Sincerely, h b
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L.' Wilson Sworn to gnd subscribed before me this _/N day of 3Ah A4 y 1992 A G A11 %
Notasty Public V
My Commission Expires YU Enclosure
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See page 2 9201220164 920114 PDR ADOCK 05000327 l]j ' b
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U.S. Nuclear Regulatory Commission Page 2 January 14 1992 cc (Enclosure):
Mr. D. E. LaBarge. Project Manager U.S. Nuclear Regulatory Comm'relon One White Flint, North 11555 Rockville Pike Rockville. Maryland 20852 NRC Resident Inspector Sequoyah Nuclear Plant 2600 Igou Ferry Road Soddy Daisy. Tennessee 37379 Mr. B. A. Wilson. Project Chief U.S. Nuclear Regulatory Commission Region !!
-101 Marietta Street. NW, Suite 2900 Atlanta. Coorgia 30323 5
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ENCLOSURE 1
t Sequoyah Nuclear Plant (SQN) l Response to NRC Cenerlc Letter 91-11 kesolution of Generic Issues (GI) 48, j
"LCOs For Class IE Vital Instrument Buses " and 49 Interlocks and LCOs for Class 1E Tie Breakers,"
Pursuant to 10 CFR 50.54(f) j t
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ENCLOSURE The following is SQN's response to the concerns contained in Enclosure 1 of Ceneric Letter (CL) 91-11.
Additional infortation may be found in Section 8.3 of the SQN Updated Final Saf ety Analysis Report (UFSAR) and SQN Technical Specifications (TSs).
Description of 120-Volt (V) Vit$1 Instrumentation Power Syste_m SQN's 120-V Vital Power System has four identical channels and eight 120-V vital instrument power boards with uninterruptable inverter power supplies (reference UTSAR Section 8.3.1.2.2, " Analysis for Vital 120-Volt AC Control Power Systems, AC Distribution Boards, and Inverters," and UFSAR Figure 8.1.2-2):
120-V ac Vital Instrument Board 1-1 and 120-V ac Vital Inverter 1-1 120-V ac Vital Instrument Board 2-1 and 120-V ac Vital Inverter 2-1 120-V ac Vital Instrument Board 1-11 and 120-V ac Vital Inverter 1-11 120-V ac Vital Instrument Board 2-11 and 120-V ac Vital Inverter 2-11 120-V ac Vital Instrument Board 1-111 and 120-V ac Vital Inverter 1-111 120-V ac Vital Instrument Board 2-111 and 120-V ac Vital Inverter 2-111 120-V ac Vital Instrument Board 1-IV and 120-V ac Vital Inverter 1-IV 120-V ac Vital Instrument Board 2-IV and 120-V ac Vital Inverter 2-IV Distribution of 120-V, alternating-current (ac) vital instrument power is performed without automatic transfers between redundant load groups and without automatic load stripping or sequence.
Each power channel's equipment in electrically and physically independent f rom the equipment of other channels. Normal power to the 120-V, ac vital instrument power boards is from an ac,120-V vital inverter with each board having its own inverter.
Alternate 120-V, ac power for the boards is from the 480-V shutdown boards by means of an instrument power transformer. A manual transfer switch, located on the 120-V, ac vital instrument power board, is used to transfer between the normal and alternate power.
The 480-V, ac vital transfer switch supplying this alternate and/or maintenance power to the 120-V, ac vital instrument board also powers the same channel of 120-V, ac vital inverters and 125-V, direct-current (de) vital battery charger. Train A is the normal 480-V power source f or Channels I and III, and Train B is the normal 480-V power source for Channels Il and IV.
Alternate 480-V, ac power, which is supplied by the opposite train, may be selected by way of a manual transfer switch. Also, two spare battery chargers are provided. One can be substituted for the normal Channel I or 11 charger and the other for the normal Channel III or IV charger. These spare chargers may be powered from either train by means of their 480-V vital transfer switch.
The 120-V, ac vital inverters contain an auctioneering circuit that accepts de power f rom either the inverter rectifier (rectifies 480-V ac to 125-V de) or a 125-V, de vital battery haard.
Power for the 125-V, de vital battery boards is normally from its 125-V, de vital battery charger with the 125-V, de vital battery being the emergency backup.
Each 125-V, de vital battery board supplies a Unit 1 and Unit 2120-V, ac vital inverter.
Channel loads are assigned according to the divisional requirements. Train A divisional loads, primarily associated with Units 1 and 2, are assigned to Channels I and 111 respectively.
In addition Train B divisional loads, primarily associated with Units 1 and 2, are assigned to Channels 11 and IV respectively.
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Response
I As stated in the description, each power channel is electrically and physically independent of other channels up to their 480-V, ac vital transfer switches. Additionally, the SQN TSs are consistent with the Westinghouse standard TSs.
Therefore, only three potential areas of concern vero identified 1.
The 480-V, ac vital transfer switches for the four channels could be placed in an arrangement such that redundant Class 1E equipment is supplied by the same power source.
2.
When a spare battery charger is substituted for one of th-normal chargers, it could be powered by the opposite train 480-V, ac power.
3.
The transfer switch on the 120-V, ac vital instrument power board could be left in the " alternate" position.
While alternate power is from the same train, it does not have battery backup as does " normal" power.
Surveillance Requirements 4.8.2.1 and 4.8.2.2 for TSs 3.8.2.1 and 3.8.2.2, respectively, require verification of correct breaker alignment for specified ac bnards and inverters at least once every seven days.
This is met by performance of Surveillance Instruction (SI) 1-S!-0PS-000-003.W. " Weekly Shift Log," for Unit I and 2-SI-000.003.W. " Weekly Shift Log," for Unit 2.
System Operating Instruction. 0-S0-250-1, "125 Volt DC Vital Power System " is the plant instruction for normal operation of the 125-V, de vital power system. -Further, as stated above, these transfer switches are verified every seven days by sis to be in their " normal" position.
Therefore, sufficient
.nistrative controls exist to ensure these switches are n-t placed in an wc a.tangement such that redundant Class IE equipment is supplied by the same power.
The identified sis also verify that, when either of the spare battery chargers is subscituted for a normal charger, they are powered from the same divisic.n of 480-V power as the charger they replaced.
Since the alignment is verified by these sis every seven days, sufficient administrative controls exist to ensure an arrangement such that redundant Class IE equipment is not supplied by the same power. Additionally, should breaker alignment be found not to be in compliance with TSs 3.8.2.1 or 3.8.2.2, the required actions will be taken and their time limits met.
System Operating Instruction, 0-S0-250-2, "120 Volt AC Vital Instrument Power System," is the plant instruction.for normal operation of the 120-V, ac vital instrument power system.
It ensures each 120-V, ac vital-instrument power board transfer switch is in the normal position as required by TS 3.8.2.1.
Should the transfer switch be placed in the alternate position, the actions of TS 3.8.2.1 would apply. Additionally, these transfer switches are verified to be in the normal position once every seven days by performance of
.1-SI-0PS-000-003.W and 2-SI-OPS-000-003.W for Units 1 and 2, respectively.
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.o In conclusion, the SQN Class 1E vital ac instrument power system is designed to be an independent system and survelliances exist to ensure continued TS compliance.
Based upon the above discussion, SQN has appropriate administrative controls to fulfill the following requirements:
1.
Limit the time that a plant is in possible violation of the single-failure criterion with regard to the Class 1E vital instrument buses and tie
- breakers, 2.
Require surve 11ances of these components, and 3.
Ensure that, except for the tines covered in item (1), the plant is operating in an electrical configuration consistent with the regulations and its design bases.
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