Text

Forwards Info Requested by NRC Re Estimate of Time Required to Borate to Cold Shutdown Conditions Using Refueling Water Storage Tank Water & Charging Pumps
	ML13330A188
Person / Time
Site:	San Onofre
Issue date:	01/05/1981
From:	Krieger R; SOUTHERN CALIFORNIA EDISON CO.
To:	Norwick S; Office of Nuclear Reactor Regulation
References
	NUDOCS 8102020499
	Download: ML13330A188 (19)
	v • d • e

MEMO.TO Stan Nowicki January 5, 1981 DATE PREPARED Operating. Reactors Branch No. 5 U. S. Nuclear Regulatory Commission Enclosed is the following information which you requested from Mr. Jack Rainsberry of my organization:

1. Calculation of estimated time required to borate to cold shutdown conditions using only RWST water and the charging pumps.

2. Section 22 of the San Onofre Unit 1 Equipment Data Manual, "Compressed Air System Equipment."

3. Section 26 of the San Onofre Unit 1 System Description Manual "Compressed Air System."

If you require any additional information please let me know.

C/)

-U CL2 cc: J. L. Rainsberry (w/enclosures)

NRC Fi les EDM Files 810 20 2 0 99 From R. W. Krieger 5-q NEW 19flS J@4tEW. ED68t

ESTIMATE OF TIME REQUIRED TO BORATE TO COLD SHUTDOWN CONDITIONS USING RWST WATER AND CHARGING PUMPS Assumptions:

1. RCS Volume = 6752 ft3 at 5750F

2.

Initial EOL Boron Concentration (Bc) = 0 ppm

3. Charging Pump Flowrate = 90 gpm

4.

Cold Shutdown Bc = 480 ppm

5.

RWST Bc = 3750 ppm at 80oF Estimated Time VdC W

W C

in 1

out dt where V = volume of RCS = 6752 ft3 C = boron concentration = 480 ppm at cold shutdown Win Wout = W = charging and letdown rate = 90 gpm =

.20052 ft3/sec.

Cl RWST Bc = 3750 ppm therefore dC W (C C) dt V

1

-Wt C = C (1 -e V

solving for t

-Wt C

e V 1

C1 t

V In

(

1 W

C 1

using values above t = 4612 sec z 77 min Conservatisms in Estimate

1. RCS volume includes pressurizer liquid volume and uncertainties

2. EOL Boron concentration is assumed

3. Charging pump flowrate is a nominal rate and not the maximum rate

4. Cold Shutdown Bc includes 100 ppm allowance for margin and uncertainties

5. RWST Bc is tech spec minimum concentration

SAN ONOFRE NUCLEAR GENERATING STATION UNIT 1 EQUIPMENT DATA

22.

COMPRESSED AIR SYSTEM EQUIPMENT TABLE OF CONTENTS Page AIR RECEIVERS, C-4A, B, AND C 22-1 AIR COMPRESSORS, K-lA, B, AND C 22-2 AIR COMPRESSOR MOTORS 22-3 INSTRUMENT AIR DRYER, X-47 22-4 INSTRUMENT AIR FILTERS X-49A, B, AND C 22-5 AUXILIARY AIR COMPRESSOR, K-12 22-6 AUXILIARY AIR COMPRESSOR MOTOR 22-7

SAN ONOFRE NUCLEAR GENERATING STATION UNIT 1 EQUIPMENT DATA

22.

COMPRESSED AIR SYSTEM EQUIPMENT AIR RECEIVERS, C-4A, B, AND C REFERENCES Manufacturer, Advance Tank Specification, BSO-403 Purchase Order, BSO-403 Quantity, Three DATA Shell, Material/Thickness A455A / 5/16 in Heads, Material/Thickness A455A / 3/8 in Overall Height 12 ft Diameter O.D.

4 ft Capacity 120 cu ft Operating Pressure 110 psig Operating Temperature Ambient to 100 F Design Pressure 125 psig Design Temperature 200 F Corrosion Allowance:

Bottom 1/8 in Remaining 1/16 in Flange Rating/Facing (ASA Std.)

150 lb R.F.

Fittings Rating 3000 lbs Earthquake Force 0.2 g Applicable Codes and Spec ASME Code & Stamped Manhole Size 11 in x 15 in 22-1

DELIVERY:

SPECIFIED/DID (SCFM)

_00 A

DISCHARGE PRESSURE (PSI*)

100 ALTITUOE ABOVE SEA LEVEL (FEET) 20 AMBIENT TEMPERATURE (DESIGN)40-100 RATED HORSEPOWER AT DRIVER SHAFT_

0 w

MAX. ALLOWABLE DISCHARGE PRESSURE 100 I.

AIR TEMP. LEAVING COMPRESSOR

-430 VERTICAL OR HORIZONTAL.

NO. OF STAGES One NO. OF CYLINDERS:

1ST STAGE/2ND STAGE One SORE AND STROKE OF CYLa IST sTG/2ND $TO.

PISTON DISPLACEMENT:

IST STAGE/2ND STAGE 464 VOLUMETRIC EFF:

IST STAGE/2ND STAGE SPEED:

CRANKSHAFT (RPM)/PISTON(FT/MIN) 327 600 LUBRICATION:

CYLINDER/CRANKCASE lkcre/Oil MATERIAL:

CYLINDER/CYLINDER LINER Cast IrCn PISTON/PISTON RINGS _

.1 I -n STUFFING BOX PACKING:

CYLINDER/CRANKCASE LENGTH DISTANCE PIECE (IF ANY)

CONNECTIONSI SIZE INLET/DISCHA 6/6 RATING INLET/DISCHARSE FACING INLET/DISCHARSE INTAKE FILTE*SILENCER:

MFR/TYPE Dd-iv e /Dr-, Tvme SIE/MODEL NO.

DRIVER:

TYPE/RATED HORSEPOWER Westinc~ -:se /5 hT DRAWING REFERENCE Oien D-i750 rn-A DIRECT CONNECTED/V*AELT DRIVE SHEAVE PITCH DIAMETER:

DRIVER/COMPRESSOR BELTS: NO.

MAKE AND TYPE/SERVICE FACTOR FLYWHEEL DIAMETER. IF ANY TOTAL WR 2

IN coMPRasson CYL. JACKET COOL. WTR:

TEMP:

INLET/DUTLET F

Wate-,

-5 "135 F FLOW/PRESS DROP__

3

/ 3 si MAX. ALLOW CYL. COOL WTR. PRESSURE -PSIC nax.

60 in INTERCOOLER/AFTERCOOLER OWO.

REFERINCEMatecials ubsA'Iit-ueSheets Nuntz Mat AIR TEMP. LEAVING AFTERCOOLER 110 F

-Afftprvnper-tptr Tn

-~

P Tn/Oiit/CPN-/i)

Guacd,eauired C alI-.

Std.

TYPE OF CONTROL/CONTROL ELECT.

POWER_____________'DualrC o 1 PRESS.

COMPR.:

LOADED OR STARTS/UNLOADED OR STOPS____________________

TYPE STARTING UNLOADERS A trm COMPRESSOR MANUFACTURER___

Chia c Pneumatin U

SIZE & TYPE______

12 x 11 - TBO-B2',

W WEIGHT:

COMPRES SOR ONLY/HEAVIEST PIECE 5HDO

.i-JTioin PIPING LAYOUT/P & I.D. NO.___________

S(REO'N NO.) (SPEC.

NO./1110t-ff*f_________

BSO -4O BECHTEL AIR COMPRESSOR DATA SHEET CROAINAIR COMPRESSORS, K-lA, B, AN JOB No 3246 REV.

San Onofre Nuclear Generating Station, POWER DIVISION Unit 1 EN N

SHEET OF 22-2

A.C. INDUCTION MOTOR DATA SHEET Customer:

Southern California Edison Company Project:

San Onofre Nuclear Generating Station, Unit No. 1 AIR COMPRESSOR MOTORS

1. Service Comp. Drive

2. No. of units:

3

3. Type:

Squirrel Cage

4. Mounting Horizontal

5. Characteristics v Ph..Cy.

440-3-60

6. Synchronous speed -

rpm 1800

7. Horsepower 75

8. Frameno 444U

9. Enclosure Drip proof-Guarded

10.

Insulation Class B

11.

Insulation treatment Thermalastic

12.

Ambient temp. -

C 40

13.

Stator temp. rise -

C.

60

14.

Bearing type Ball

15.

Rotation Either

16.

Shaft (hollow-solid)

17.

Thrust bearing load coupling -

(self-release non-reversing solid-adjustable flexible)

18.

Full load amp.

89

19.

Starting current -

amp.

540

20.

Starting torque - % F.L.

150

21.

Pull-out torque -

% F.L.

200

22.

Eff 100% load %

90.5 75% load %

90.0 50% load %

88.5

23.

P.F. 100% load 89.0 75% load 86.0 50% load 80.0

24.

Space heaters - kv

.2kw @ 550 volts

25.

Rotation*

Either

26.

Conduit box location F-1

Rotation of motor when viewed from end of motor opposite shaft extension. 22-3

0 0

22.

COMPRESSED AIR SYSTEM EQUIPMENT INSTRUMENT AIR DRYER, X-47 REFERENCES Manufacturer, C. M. Kemps Mfg. Co.

Specification, BSO-402 Purchase Order, BSO-402 Quantity, One DESCRIPTION One (1)

C. M. Kemp Mfg.

Company Dual Tower, Desiccant Air Dryer, Oriad Model No. 100-E with NEMA-4 Electrical Construction PERFORMANCE DATA Capacity 254.5 scfm Dryer Cycle 8 hours9.259259e-5 days 0.00222 hours 1.322751e-5 weeks 3.044e-6 months Adsorption 4 hours4.62963e-5 days 0.00111 hours 6.613757e-6 weeks 1.522e-6 months Reactivation 4 hours4.62963e-5 days 0.00111 hours 6.613757e-6 weeks 1.522e-6 months Inlet Pressure 110 psig Inlet Temperature 100 F Final Dewpoint Minus 20 F Pressure Loss at Design Flow 1 psig Reactivation Heat 3.5 KW Reactivation Purge 4.5 scfm PHYSICAL DATA ASME Code Design 150 psig Electrical Construction NEMA 4 Control Circuit 115 Volt, 1 Phase, 60 Cycle Power Circuit 440 Volt, 3 Phase, 60 Cycle Method of Control Full Automatic Desiccant 120 lbs Silica Gel/Tower Overall Dimensions 4 ft -

5 in by 2 ft -

8 in by 6 ft 4 in Weight 2300 lbs 22-4

22.

COMPRESSED AIR SYSTEM EQUIPMENT INSTRUMENT AIR FILTERS X-49A, B, AND C REFERENCES Manufacturer, Beach Sta-Dri Filter Co.

Specification, BSO-4001 Purchase Order, BSO-4001 Quantity, Three PERFORMANCE DATA Flow Rate 200 scfm Design Pressure 100 psig Allowable Air Pressure 150 psig Cleaning Capacity 9 to 10 million cu ft of air (for a well maintained compressor)

PHYSICAL DATA Model 600 AL Connection, Inlet 2 inch - NPT Outlet 2 inch - NPT Weight 50 lbs (each)

Cylinder length 17 in No. of Elements per Cylinder 2

MATERIALS Top and Bottom Spacers Aluminum Gaskets Neoprene Cylinder Aluminum Castings, Top and Bottom Aluminum 22-5

DELIVERY:

SPECIFIoED/SID (SCFu) 98.0 1 IsCHARGE PRESSURE__(PSI) 100, Adjustable to 60 & Set to 65 ALTITUDE ABOVE SEA LEVEL (FEET)

AMBIENT TEMPERATURE (DESIGN) 600 Design Point 40-1w0 RAngp RATED HORSEPOWER AT DRIVER SHAFT 24 @ 75 psig 01 MAX. ALLOWABLE DISCHARGE PRESSURE 125 a

AIR TLMP.

LEAVING COMPRESSOR 5

VERTICAL OR HORIZONTAL.

Horizontal Tank Mounted NO. OF STAGES 2

NO.

OF CYLINDERS: IST STAGE/2ND STAGE_

2/1 11

.BORE AND STROKE OF CYLl IST STG/2ND STe.

6-0 / 2-3/4--/ 3-1/2 / 2-3/4 PISTON DISPLACEMENT:

1ST STAGE/2ND STAGE_ __

3.3 VOLUMETRIC EFF:

IST STAGE/2ND STAGE 73% @ o0 psig 72% @ 100 psiz x

SPEED:

CRANKSHAFT (RPM)/PISTON(FY/MIN) 1470/860 LUBRICATION:

CYLINDER/CRANKCASE Oil/Oil MATERIAL:

CYLINDER/CYLINDER LINE_

Cast Iron PISTON/PISTON RINGS Aluminum (LP) / C! (HP)

STUFFING BOX PACKING:

CYLINDER/CRANKCASE LENOTH DISTANCE PIECE (IF ANY)

CONNECTIONSI SI1E INLET/DISCHARE 3!1/3'f RATING INLET/DISCHARGE NPTI FACING INLET/DISCHARGE INTAKE FILTER-SILENCER:

MPR/TYP__.

S2I/MODEL NO.

DRIVER:

TYPE/RATED HOKSEPOWERNon Overloading Westinghouse DRAWING REFERENCE DIRECT CONNECTED/V*BELT DRIVE Multi V-Belt Drive SHEAVE PITCH DIAMETER:

DRIVER/COMPRESSOR BELTS: NO. MAKE AND TYPE/SERVICE FACTOR FLYWHEEL DIAMETER. IF ANY TOTAL wa 2

IN COMPRSOR CYL. JACKET COOL. WTR:

TEMP:

INLET/OUTLET FLOW/PRESS DROP MAX. ALLOW CYL. COOL WTR. PRESSURE INTERCOOLER/AFTERCOOLER DOW.

REFERENCE AIR TEMP. LEAVING AFTERCOOLER TYPE OF CONTROL/CONTROL ELECT. POWER Dual Control PRESS. COMPR.:

LOADED OR STARTS/UNLOADED OR STOPS TYPE STARTING UNLOADERS z

Specification BSO-4023 urcnase Urder BSO-4023 COMPRESSOR MANUFACTURER Worthington SIZE & TYPE 6-0/6-0/3-1/2 x 2-3/4 25BN-24 WEIGHT:

COMPRESSOR ONLY/HEAVIEST PIECK 2170 PIPING LAYOUT/P

& I.D.

NO.

o (REO'N NO.)

(SPEC.

NO./COST CODE CORTORAON AIR COMPRESSOR DATA SHEET CORPORTI ONJOB No 3246 AUXILIARY AIR COMPRESSOR, K-12 San Onofre Nuclear REV.

Generating Station, Unit 1 POWER DIVISION ENGINEERING a *9 SHEET OF 22-6

A.C. INDUCTION MOTOR DATA SHEET Customer:

Southern California Edison Company Project:

San Onofre Nuclear Generating Station, Unit No. 1 Date:

February 21, 1967 AUXILIARY AIR COMPRESSOR MOTOR

1. Service Auxiliary Air Compr ssor

2. No. of units:

One

3. Type:

Induction

4. Mounting Horizontal

5. Characteristics 3/60/440

6. Synchronous speed -

rpm 1800

7. Horsepower 25

8. Frameno 324U

9. Enclosure Drip-Proof

10.

Insulation Class B

11.

Insulation treatment Lifeguard

12.

Ambient temp. -

C 40

13.

Stator temp. rise -

C.

60

14.

Bearing type Std. (Not less than 100,000 hours0 days 0 hours 0 weeks 0 months life)

15.

Rotation Clockwise

16.

Shaft (hollow-solid)

Solid

17.

Thrust bearing load coupling -

(self-release non-reversing solid-adjustable flexible)

18.

Full load amp.

19.

Starting current -

amp.

20.

Starting torque - % F.L.

21.

Pull-out torque - % F.L.

22.

Eff 100% load %

75% load %

50% load %

23.

P.F. 100% load 75% load 50% load

24.

Space heaters -

kv

25.

Rotation*

26.

Conduit box NEMA 4 W/unthreade 1/4" Drain Hole one size larger than standa

Rotation of motor when viewed from end of motor opposite shaft extension.

22-7

SAN ONOFRE NUCLEAR GENERATING STATION UNIT 1 SYSTEM DESCRIPTION

26.

COMPRESSED AIR SYSTEM TABLE OF CONTENTS Page FUNCTION 26-1 DRAWING REFERENCES 26-1 DESIGN CRITERIA 26-1 System 26-1 Components 26-1 NORMAL OPERATION 26-2 STARTUP OPERATION 26-4 ABNORMAL OPERATION 26-4

SAN ONOFRE NUCLEAR GENERATING STATION UNIT 1 SYSTEM DESCRIPTION

26.

COMPRESSED AIR SYSTEM FUNCTION The compressed air system provides a continuous supply of pressurized air for instruments, controls, and other servicerequirements.

DRAWING REFERENCES 568780 Compressed Air, P & ID DESIGN CRITERIA SYSTEM The system supplies oil-free, dry, compressed air at 85 to 100 psig, at a flow rate of 100 scfm and a maximum dew point of minus 20 F for pneumatic instrument operation -and control.

The system also supplies compressed air to service outlets throughout the Station for operation of pneumatic tools or other requirements.

COMPONENTS Air Compressors K-1AB,C Design capacity, each 300 scfm Design discharge pressure 100 psig Aftercoolers E-26A,BC Air inlet temperature 450 F Air outlet temperature 110 F Cooling water flow 5 gpm Cooling water inlet temperature 95 F Cooling water outlet temperature 135 F Air Receivers C-4A,B,C Volume, each 120 Cu Ft Design pressure 125 psig Design temperature 120 F Instrument Air Dryer X-47 Type-Desiccant Capacity, minimum 250 scfm Air outlet dewpoint minus 20 F Pressure drop 1 psi Internal reactivation heater cap., each 3.5 kw Reactivation purge flow 4.5 scfm 26-1

26.

COMPRESSED AIR SYSTEM DESIGN CRITERIA (Continued)

Instrument Air Filters X-49ABC Capacity, each at 8 psi pressure drop 200 scfm Design pressure 100 psig NORMAL OPERATION During normal operation, one of the three single-stage, non lubricated, air compressors operates continuously to supply the Station instrument and service air requirements.

The cylinder unloading mechanism is operated automatically to match the system demand. Whenever the air compressor is operating (assume K-IA), the solenoid valve (SV-62) is energized to load from closing of its respective motor start. Energizing SV-62 discharges system pressure as long as the system pressure remains between 90 and 100 psig (the force exerted by the air pressure is greater than the spring pressure at the unloader and the compressor cylinder inlet valves are' kept open).

Air drawn into the cylinder is discharged through the inlet valves without being compressed and the compressor idles (unloaded). When system pressure drops below 90 psig, the force exerted by the air pressure is less than the spring pressure at the unloader and the cylinder inlet valves close.

The compressor is then loaded.

The two remaining air compressors are manually positioned in automatic stand by from the control room and will start in sequence upon the decrease of supply air header pressure.

Pressure Switch PS-57 starts Compressor-K-lB at 75 psig and Pressure Switch PS-58 starts compressor K-lC when system pressure drops to 70 psig.

The unloader valve operation.for these compressors is identical to compressor K-lA,.described above.

Operation of the standby air compressors is annunciated in the control room. The standby air compressors must be stopped manually. When the system demand has returned to normal, air is admitted to the suction of a compressor through a filter-silencer.

The filter-silencer reduces noise and filters out dirt particles from the air stream prior to entering the cylinder.

Discharged air flows through an aftercooler where the temperature is reduced to 110 F before it enters the air receivers.

Cooling water flow (Turbine Cycle Cooling Water System) to the aftercoolers is continuous, having been established at initial startup.

Aftercooler air inlet temperature alarms are provided by TS-15, TS-16 and TS-17 which annunciate high temperature in the control room and trip the respective compressor motors.

The air receivers are reservoirs and serve as surge chambers for the compressors to minimize system pressure fluctuations.

The air receivers are equipped with relief valves (RV-23, RV-24 and RV-25) and local pressure indicators.

Each receiver and its respective air compressor is isolated as a unit for maintenance. A check valve is provided at each air receiver outlet to prevent loss of compressed air through a stopped compressor with broken dis charge valves.

26-2

26.

COMPRESSED AIR SYSTEM NORMAL OPERATION (Continued)

A common air supply header receives air flow from the three receivers and supplies the instrument air header and the service air header on demand.

The instrument air header supplies instrumentation and pneumatic controllers:

throughout the Station which require compressed air of high purity and low dew point.

Since some controllers require 3-15 psi instrument air pressure for operation, and others 3-27 psi, Station control valve operation requires that instrument air header pressure be maintained above 40 psig.

To maintain acceptable purity and low dew point, an instrument air dryer (X-47) is provided.

The air dryer is a dual tower dessicant-type unit with fully automatic controls. Instrument air enters one of the desiccant towers through four-way Solendid Valve SV-105 and is discharged through four-way Solendid Valve SV-106. After a pre-set time (four (4) hours), a timer switch located on the unit automatically positions SV-105 and SV-106 for direct flow to the second tower.

The first tower is then automatically regenerated by heating the silica gel dessicant with an internal 3.5-kw electric heater. A reactivation purge flow of 4.5 scfm is automatically supplied during reactivation which requires four (4) hours.

Local pressure gauges, mounted on each tower, provide visual indication of pressure drop through the dryer. Relief Valves RV-44 and RV-45 are provided, one on each tower, to prevent over-pressure by air heat-up as a result of being dried.

Instrument air filters are provided after the instrument air dryer to remove impurities. Normally, all three filters are in parallel service.

The air leaving the filters,is split into two instrument air headers which form a loop to supply all areas of the Station. Branch lines are taken off the instrument air header loop. Each branch line contains a restricting orifice which limits flow through the line to 150 cfm in the event of a line rupture downstream from the orifice.

Compressed air leak-off from penumatic instruments and valves inside the Sphere is collected in a common header. Normally, the leak-off flows through CV-40 and CV-10 to the vent stack (Air Conditioning System).

When the Sphere high radiation alarm is actuated in the control room, three-way valve CV-40 actuated by SV-19, is automatically positioned to divert leak off flow to the Sphere atmosphere, and CV-10 actuated by SV-28 is closed.

The same control valve action is initiated when high pressure exists in the Sphere exhaust duct (PS-23) or is initiated manually from the control room.

Service air is supplied to the various Station service air outlets directly from the air receivers through Control Valve CV-41 and a service air header loop.

Control Valve CV-41 is actuated by Pressure Controller PC-1 to cut off service air use if the compressed air system supply pressure drops to 70 psig. This is to assure that instrument air supply which has priority.

26-3

26.

COMPRESSED AIR SYSTEM STARTUP OPERATION The three manual valves on the air receiver discharge lines to the air header are opened before starting a compressor. The flow path is established through the instrument air dryer and the three instrument air filters in parallel.

Normally, Compressor K-lA is started manually from the control room by positioning the control switch in START. Pressure Switch PS-56 will start the compressor due to low compressed air header pressure. System pressure will begin to increase through Receiver C-4A and Receivers C-4B and C-4C will be pressurized through orfices in the check valves on the air outlet piping from.each receiver. Control Valve CV-41 on the service air header, will remain closed until the air receiver (C-4A) pressure exceeds 70 psig.

When system pressure is 100 psig, Compressor K-lA will unload as described in Normal Operation.

Cooling water supply is automatically established to the three air compressor cooling water jackets through Solenoid Valves SV-59, SV-60 and SV-61, when the respective compressor motors are energized. Cooling water is supplied from the Turbine Plant Cooling Water System.

ABNORMAL OPERATION When the compressed air load exceeds 300 cfm, which is the capacity of one compressor (assume K-lA), system pressure will drop. When system pressure drops to 75 psig, a pressure switch (PS-57) closes, starting the second compressor (K-1B) automatically and a pressure switch (PS-53) positions Solenoid Valve SV-63 to the LOADED position. If system pressure continues to drop, Compressor K-lC is started automatically at 70 psig by PS-58.

At 70 psig, service air flow is stopped by CV-41, and the three compressors (900 cfm) are utilized for instrument air supply exclusively.

All three compressors will continue to operate after system pressure has been returned to 100 psig. When system demand returns to normal, two compressors (K-LB and K-lC) can be turned off and re-positioned manually to automatic standby.

Any of the three compressors can be selected as the operating compressor from the control room with the remaining compressors on automatic standby.

Sequence of operation may be varied by adjusting the pressure switch settings.

Abnormal operating conditions are annunciated in the control room by Flow Switch FS-5 for high instrument air flow to the Sphere, from Pressure Switch PS-15 for low instrument air header pressure, and from Pressure Switch PS-16 for low service air header pressure.

26-4

Southern California Edison Company P. 0. BOX 800 2244 WALNUT GROVE AVENUE ROSEMEAD, CALIFORNIA 91770 6

J. G. HAYNES February 2,

1981 MANAGEROF NUCLEAR OPERATIONS 2, 198 5E7EP 1O4 U. S. Nuclear Regulatory Commission Office of Inspection and Enforcement Region V 1990 North California Boulevard Suite 202, Walnut Creek Plaza Walnut Creek, California 94596 Attention:

Mr. R. H. Engelken, Director DOCKET NO. 50-206 SAN ONOFRE -

UNIT 1

Dear Sir:

This letter constitutes a revision to a reportable occurrence involving loss of power to all station auxiliaries, previously reported to you in LER 80-038 dated December 9, 1980.

It was noted that during this incident, 4Kv breaker 11C02, source breaker to 4Kv bus IC, did not open on loss of voltage as required.

Subsequent investigation revealed that the No. 1 D.C. bus control power switch to the station undervoltage scheme for the IC bus was open. This switch is required to be in the closed position for complete operation of the station undervoltage scheme during a Loss of Power (LOP) or Safety Injection Signal/Loss of Power (SIS/LOP) event.

The primary function of the aforementioned undervoltage scheme is to strip 4Kv bus 1C of remaining loads during a LOP or SIS/LOP event. This circuit is energized to perform this function. However, with the D.C. control power swtich open, the undervoltage scheme will remain deenergized. In this condition, the potential exists for applying load blocks larger than the diesel generator is designed to accept.

The subject D.C. control power switch is physically located in 4Kv breaker cubicle 11CO1.

It is identified as the control power to the station undervoltage scheme and is located within six inches from a similar D.C.

switch that supplies control power to breaker 11CO1.

When "racking out" a 4Kv breaker, it is normal practice to open the D.C. control power switch to that breaker. Breaker 11COl is the tie breaker between 4Kv buses 1-C & 1-A and would be racked out for clearances on these buses or for breaker servicing.

U. S. Nuclear Regulatory Commission Page #2 A review of our records indicate that the control power switch to the undervoltage scheme was verified to be closed at the end of our last refueling outage. At that time sequencer testing including SIS/LOP was completed satisfactorily. From that time until this outage, there were no clearances issued which would have required opening of the D.C.

control power switch to breaker 11COl or the No. 1 D.C. bus control power switch to the undervoltage scheme. However, during the current refueling outage there were at least two times when the D.C. control power switch to breaker 11CO was opened. It is believed that on one of these occasions the D.C. control power switch to the station undervoltage scheme was inadvertently opened due to its close proximity to the D.C.

control power switch to breaker 11CO1.

The first of the two occasions noted above occurred on April 16, 1980, one week after reactor shutdown. Prior to the first occasion the SIS/LOP signal had been locked out and the reactor was in the cold shutdown condition. In this mode the normal loading on 4KV bus 1C would not be greater than the maximum load block that the diesel generator is designed to accept. Due to equipment testing however, there may have been brief periods when the loading on 4Kv bus 1C was greater than the design load block.

With the SIS/LOP signal locked out, an LOP event would automatically start the Diesel Generators but loading would be accomplished manually as specified in Emergency Operating Instruction, SO-3-5.30, Loss of Offsite Power. This procedure lists the automatic equipment trips associated with the station undervoltage scheme and requires verification that breaker 11C02 is open prior to manual loading. In the unlikely event the diesel generator had not been able to accept the loading which may have been on 4Kv bus IC and tripped, the operator would have detected the failure of the automatic trip functions and taken immediate remedial action.

Based on the above information, it is our conclusion that the station undervoltage transfer scheme was disabled inadvertently during the current refueling outage but that this disabling would have no adverse effect on plant safety during this time. Testing of the sequencer is required prior to return to service and discovery of the open switch would have been assured at that time. There was no effect on public health and safety as a result of this event.

To preclude recurrence of this incident, the station will develop and implement administrative controls on safety-related D.C. control circuits prior to our return to service from the current refueling outage.

U. S. Nuclear Regulatory Commission Page #3 Should you have any questions regarding this incident, please call me.

Sincerely,

Enclosure:

LER 80-038 Rev. 1 cc:

L. F. Miller (NRC Resident Inspector - San Onofre Unit 1)

Director, Office of Management Information & Program Control Director, Nuclear Safety Analysis Center

NRC FORM 366 1OU.S.

NUCLEAR REGULATORY COMMISSION CONTROL BLOCK: [J~

(PLEASE PRINT OR TYPE ALL REQUIRED INFORMATION)

FoLri 1 IC 1A.tS 10oIS 11-1 0

10

- 10 10 10 10 1 1-10 lo I01 4 1 1i11 11 1 01 1i 7

8 9

LICENSEE CODE 14 15 LICENSE NUMBER 25 26 LICENSE TYPE 30 57 CAT 58 coN'T REOT10 2 0- 12 8

1 REPORT 0

5 10 1 10 12 10 76 1 11 12 12 j8 10 I 1

i I I

7 8

60 61 DOCKET NUMBER 68 69 EVENT DATE 74 75 REPORT DATE 80 EVENT DESCRIPTION AND PROBABLE CONSEQUENCES With the RCS drained to mid loop and transferring a 4KV bus power supply from aux. transformer C to aux. transformer A&B, AC power to all station auxiliaries O 4-was lost for 15 seconds due to brkr misalignment. It was also noted that source brkr j to 4Kv bus IC did not open on loss of voltage due to an open D.C. switch supplying I

FO T61 power to the station undervoltage scheme.. There was no effect upon public health and I safety nor was there any impact on plant safety. Both emergency diesel generators l

started automatically and were available for loading if needed.

I 890 SYSTEM CAUSE CAUSE COMP.

VALVE CODE CODE SUBCODE COMPONENT CODE SUBCODE SUBCODE lD 9E lBDl

()J (D ) CIKITIBIRIK 1 (i4 7

8 9

10 11 12 13 18 19 20 7

g SEQUENTIAL OCCURRENCE REPORT REVISION LERERO EVENT YEAR REPORT NO.

CODE TYPE NO.

(

EPO)

L 8 1 0 L

0 3 1 8j l~

10 1 3 I-NUMBE R jj~

~

J 1111 LJLi

~

N 21 22 23 24 26 27 28 29 30 31 32 ACTION

.FUTURE EFFECT SHUTDOWN ATTACHMENT NPRD-4 PRIME COMP.

COMPONENT TAKEN ACTION ON PLANT METHOD HOURS 2

S2 SUBMITTED FORM suB.

SUPPLIER MANUFACTURER 2

2 2

1 0

0 1 0 1 09

(

@2 (L )

l Z19 19 l19 LIJSLIJ LiO LID 10001IL i

W Z0tt 33 34 35 36 37 40 41 42 43 44 47 CAUSE DESCRIPTION AND CORRECTIVE ACTIONS A licensed operator intending to open auxiliary transformer C bus supply breakers inadvertently opened the 4KV bus tie breakers. The D.C. power supply switch to station undervoltage scheme was inadvertently opened by personnel racking out a nearby brkr.

Administrative controls on safety related D.C. circuits will be implemented to preclude recurrence.

80 7

AC8LIT METHOD OFDICVRDERPTO STATUS

% POWER OTHER STATUS MISCOVERY DISCOVERY DESCRIPTION 0

jJN.A.

00 (J)W Operator Observation 7

8 9

10 12 13 44 45 46 80 ACTIVITY CONTENT REL ASED OF RELEASE AMOUNT OF ACTIVITY 35ALOCATION OF RELEASE ELE 0N.A.

N.A.

7 8

9 10 11 44 45 PERSONNEL EXPOSURES NU BE TYPE DESCRIPTION 10 1 1'b 1 J N.A.

7 8

9 11 12 13 PERSONNEL INJURIES 50o206 NUMBE DESCRIPTION J)

?O-JS APPLT:CAT CRP ECE Io p I1 1

N.A.

-U-O0) 8 9

11 12 LOSS OF OR DAMAGE TO FACILITY TjPE DESCRIP T19N ILJ@1 N_.A.

7 8

9 10 s8 PUBLICITY U

is UED DESCRIPTION NL IRII

.A.

9 10 68 69 80 NAME OF PREPARER J.M urnPHONE:

(714) 49277000

______________________________80L

ML13330A188

Text

Dear Sir:

Enclosure:

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