ML15117A213

Summary of 940406 Meeting W/Util Re Proposed TS Change to Delete Requirements Re Emergency Condenser Circulating Water Sys.Attendance List & Related Info Encl

ML15117A213
Person / Time
Site:	Oconee
Issue date:	04/13/1994
From:	Wiens L Office of Nuclear Reactor Regulation
To:	Office of Nuclear Reactor Regulation
References
NUDOCS 9404210137
Download: ML15117A213 (25)

Text

.e e

UNITED STATES NUCLEAR REGULATORY COMMISSION t

WASHINGTON, D.C. 2055-0001 April 13, 1994 Docket Nos. 50-269 and 50-270 LICENSEE:

Duke Power Company, et al.

FACILITY:

Oconee Nuclear Plant, Units 1 and 2

SUMMARY

OF APRIL 6, 1994, MEETING WITH DUKE POWER COMPANY ON PROPOSED CHANGES TO OCONEE TECHNICAL SPECIFICATIONS On April 6, 1994, NRC staff members met with representatives of Duke Power Company (DPC) to discuss issues related to'a proposed Technical Specification (TS) change to delete requirements related to the Emergency Condenser Circulating Water (ECCW) System. Meeting attendees are included as. Specific questions which were discussed at the meeting are included as Enclosure 2. Copies of information describing the operation of the ECCW system are included as Enclosure 3.

In response to question 1, the licensee provided a detailed description of the operation of the ECCW system. For question 2, the DPC representatives agreed that the auxiliary service water (ASW) pump in question would.not be available during a Station Blackout (SBO) event, and should not have been included in the submittal.

In a discussion of the methods of providing decay heat removal during an SBO event (question 3), the 1icensee stated that the preferred method was to use the turbine-driven Emergency Feedwater (TDEFW) pump, with the Standby Shutdown Facility (SSF) ASW pump being a backup means. They stated that there was uncertainty on the part of DPC as to what system the NRC SBO Safety Evaluation Report (SER) credited for decay heat removal during an SBO event. The NRC representatives indicated that the NRC had credited the SSF ASW pump alone in the SBO SER.

With respect to cooling water (Low Pressure Service Water) for the TDEFW pump (question 4), the licensee stated that.a seismic event in conjunction with an SBO event was beyond the design basis of the plant. The staff agreed. For other transients coupled with a seismic event, the two moter driven pumps are available to provide decay heat removal.

The NRC representatives indicated that they were still evaluating the acceptability of restarting non-safety related loads for accident mitigation. This discussion also addressed question 5, where the DPC representatives stated that no loads were restarted during an SBO event, because by definition, there was no power available.

However, SBO analysis assumes power would be restored in 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br />, at which time necessary loads would be restarted. In response to question 6, it was stated that the ECCW requirements were originally included to address SBO 940421017 974041 C PDR' ADOGC&

O5 26 1,'

2 -

April 13, 1994 concerns. However, the subsequent SBO analysis performed in response to NRC requirements and the use of the SSF to provide decay heat removal now made the use of the ECCW system unnecessary. Reference was made to an Oconee TS amendment issued on April 30, 1984, in support of this statement.

In concluding the meeting, DPC representatives agreed to supplement their submittal to delete a surveillance requirement for the ECCW system that had been overlooked in the original submittal.

They agreed to also clarify the use of the TDEFW pump, SSF ASW pump, and delete reference to the "tornado" ASW pump. The revised submittal was to also indicate whether the ECCW system was required to support any accident scenario (other than an SBO).

This supplement is to be submitted by April 20, 1994.

/s/

L. A. Wiens, Project Manager Project Directorate 11-3 Division of Reactor Projects -

I/II Office of Nuclear Reactor Regulation

Enclosures:

1. Meeting Attendees

2. Questions

3. Handouts cc w/enclosures:

See next page DISTRIBUTION

Docket File D. Matthews NRC & Local PDRs W. LeFave, 8D1 PD23 Reading File W. Poertner, RH W. Russell/F. Miraglia M. Caruso, 8E23 ADPR/NRR H. Abelson, 8E23 S. Varga G. Lainas L. Wiens L. Berry OGC E. Jordan ACRS (10)

L. Plisco 17-G-21 J. Johnson (Acting) RII OFF LA:PD23:

PE PM D23:DRPE D:P E

NAM LBerry L

iens:dt DMatthews DATE

/

//94

/ ) /94

/

/94 Document Name: G\\OCONEE\\MTGSUM.EFW

2 -

April 13, 1994 concerns. However, the subsequent SBO analysis performed in response to NRC requirements and the use of the SSF to provide decay heat removal now made the use of the ECCW system unnecessary. Reference was made to an Oconee TS amendment issued on April 30, 1984, in support-of this statement.

In concluding the meeting, DPC representatives agreed to supplement their submittal to delete a surveillance requirement for the ECCW system that had been overlooked in the original submittal. They agreed to also clarify the use of the TDEFW pump, SSF ASW pump, and delete reference to the "tornado" ASW pump. The revised submittal was to also indicate whether the ECCW system was required to support any accident scenario (other than an SBO).

This supplement is to be submitted by April 20, 1994.

L. A. Wiens, Project Manager Project Directorate 11-3 Division of Reactor Projects -

I/II Office of Nuclear Reactor Regulation

Enclosures:

1. Meeting Attendees

2. Questions

3. Handouts cc w/enclosures:

See next page

Duke Power Company Oconee Nuclear Station cc:

A. V. Carr, Esquire Mr. Steve Benesole Duke Power Company 422 South Church Street Comp Charlotte, North Carolina 28242-0001 Oconee Nuclear Site P. 0. Box 1439 J. Michael McGarry, III, Esquire, Seneca, South Carolina 29679 Winston and Strawn 1400 L Street, NW.

Mr. Mark Lesser, Section Chief Washington, DC 20005 Project Branch #3 U. S. Nuclear Regulatory Commission Mr. Robert B. Borsum 101 Marietta Street, NW. Suite 2900 Babcock & Wilcox Nuclear Power Division Suite 525 Ms. Karen E. Long 1700 Rockville Pike Assistant Attorney General Rockville, Maryland 20852 North Carolina Department of Justice Manager, LIS P. 0. Box 629 NUS Corporation Raleigh, North Carolina 27602 2650 McCormick Drive, 3rd Floor Clearwater, Florida 34619-1035 Mr. G. A. Copp Licensing -

ECO50 Senior Resident Inspector Duke Power Company U. S. Nuclear Regulatory Commission 526 South Church Street Route 2, Box 610 Charlotte, North Carolina 28242-0001 Seneca, South Carolina 29678 Mr. J. W. Hampton Regional Administrator, Region II Vice President, Oconee Site U. S. Nuclear Regulatory Commission Duke Power Company 101 Marietta Street, NW. Suite 2900 P. 0. Box 1439 Atlanta, Georgia 30323 Seneca, South Carolina 29679 Max Batavia, Chief Dayne H. Brown, Director Bureau of Radiological Health Division of Radiation Protection South Carolina Department of Health North Carolina Department of and Environmental Control Environmental Health and 2600 Bull Street Natural Resources Columbia, South Carolina 29201 P.0 Box 27687 Raleigh, North Carolina 27611-7687 County Supervisor of Oconee County Walhalla, South Carolina 29621

ENCLOSURE 1 ATTENDEES OCONEE ECCW TS MEETING NAME ORGANIZATION Len Wiens NRC/NRR Bill LeFave NRC/NRR W. K. Poertner NRC/RII Mark Caruso NRC/SRXB Susan Simpson Oconee/Mechanical System Greg Byers Duke/Charlotte/Safety Analysis Bryan Dolan Duke Power Company Leonard J. Azzarello Duke Power Company Harvey Abelson NRR/SRXB

ENCLOSURE 2 QUESTIONS RELATED TO ECCW TECHNICAL SPECIFICATION CHANGE

1.

Provide a description of the Emergency Condenser Circulating Water System, including interrelationships with other systems.

Identify the safety and non-safety portions of the systems.

Include power supplies for significant pumps and valves. Describe the various operating modes of the system (i.e., gravity flow, siphon, forced flow) and the conditions needed to support each.

2.

In Attachment 5 of your December 8, 1993 amendment request, you mention use of the ASW (not the SSF ASW) pump as a means of secondary side decay heat removal.

This pump appears to be mentioned in the context of response to a SBO event, even though it would not be available under that scenario. Please clarify.

3.

In reviewing past correspondence related to your response to the SBO rule (including the NRC approval letter), it appears that the credited method of coping with this event for up to a four hour period is through use of the SSF. Your amendment request, however, implies that the credited method of decay heat removal is use of the turbine-driven EFW pump with the hotwell, upper surge tank, and condensate storage tank as suction sources.

No mention of the SSF is made whatsoever. Please explain this apparent inconsistency. What is the preferred method of coping with an SBO? What are the alternative methods?

4.

One function of the LPSW system is to provide cooling for the turbine driven EFW pump. Under a loss of all AC power scenario (i.e., SBO) in which ECCW siphon flow is lost and gravity flow is inadequate because of lake level, what source of water would provide cooling for the EFW pump if it is to be used to mitigate the event? What other components/equipment normally cooled by the LPSW would be cooled under this scenario?

5.

Your method of coping with a SBO event seems to rely heavily on.

restarting the CCW pumps within 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br />. Please specify the sources(s) of power available to restart these pumps and at what time during the event you expect restart to occur. If for some reason the pumps could not be restarted within the four hour coping period, what method would be used for continued decay heat removal for, say, 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />?

6.

If, as you have concluded in your amendment request, the ECCW system is not a system that is required for safety, why was it given an operability TS in the first place?

ENCLOSURE 3 Description of the ECCW System The Condenser Circulating Water (CCW) System provides cooling water to the condensers during normal operation of the plant.

Following a design basis event involving loss of the CCW pumps, the Emergency Condenser Circulating Water (ECCW) System supplies suction to the Low Pressure Service Water (LPSW) pumps. It also provides flow through the condenser for decay heat removal.

The CCW System is designed to take suction from the intake canal, provide suction to the Low-Pressure Service Water (LPSW), High Pressure Service Water (HPSW), Aux Service Water (ASW), and the Standby Shutdown Facility (SSF) ASW systems.

It is used to condense turbine exhaust in the condenser, and to provide cooling water for the Condensate Coolers and the Recirculated Cooling Water (RCW) system.

The CCW system has an emergency discharge line to Lake Hartwell via the Keowee hydro tailrace. This discharge line is connected toeach of the three condensers of each unit.

Under a loss of power situation, the emergency discharge line will automatically open and the CCW system will continue to operate as an unassisted siphon. The siphon system is the ECCW system and can be divided into two distinct parts. The "first siphon" takes suction from the CCW intake canal and supplies flow to the CCW crossover header in the Turbine Building basement, where the LPSW System takes suction. The "second siphon" takes suction from the CCW intake piping, supplies flow through the condenser, and discharges to the Keowee hydro tailrace.

During a Loss of Offsite Power (LOOP) situation, the CCW pumps will be tripped by a load shed command. The ECCW System first siphon is required to supply suction to the LPSW system until a CCW pump is manually restarted by a control room operator.

Gravity flow (without relying on the siphon) to the suction of the LPSW pumps is possible if the lake level is sufficiently above the bottom of the CCW intake piping to maintain the required NPSH and flow demand.

During a loss of all AC power situation (Station Blackout),

the ECCW System is not required to supply suction to the LPSW System since power to the LPSW pumps would not be available.

The second siphon is the preferred method for decay heat removal. Decay heat removal can also be accomplished by venting steam to the atmosphere using the main steam safety valves or the manual atmospheric dump valves. The Emergency Feedwater system has sufficient inventory to cope with a four-hour Station Blackout by venting steam to the atmosphere.

During forced flow various numbers of CCW pumps provide flow through the intake piping to the LPSW pumps, HPSW pumps, condensate coolers, RCW coolers, and through the condenser out the normal discharge. To provide forced flow, power must be available form the 4KV switchgear, and HPSW must provide cooling and seal water to the CCW pump motor and shaft.

Upon loss of power, flow is diverted from the normal discharge to the emergency discharge through the Condenser Emergency

'Discharge valves to establish siphon or gravity flow through the Condenser. SLC 16.9.7 provides the conditions required for gravity and siphon flow.

CONDENSER CIRCULATING WATER (CCW)

Purpose Condense Turbine Exhaust in Condenser Aid in Maintaining Condenser Vacuum Provide Cooling Water for Condensate Coolers, Recirculating Cooling Water (RCW)

Suction Source for:

Low Pressure Service Water (LPSW)

High Pressure Service Water (HPSW)

Auxiliary Service Water (ASW)

Standby Shutdown Facility (SSF) ASW Ultimate Heat Sink for Decay Heat Removal

CCW SYSTEM Key Characteristics Intake Structure supports pumps, valves, and screens CCW Pumps four per unit, located at intake structure interlock: discharge valve must be closed to start Pump Discharge Valves one per pump, located at intake structure prevents water hammer at pump start prevents backflow through idle pump CCW High and Mid Point Vents located in 132" lines at intake, in lines near Turbine Bldg., and in normal discharge

- ensure CCW lines are full of water and air free as CCW lines fill

CCW SYSTEM Key Characteristics (cont'd)

Surge Line located in Turbine Bldg. where two 132" lines join to form 186" header 75 ft. tall, 30" dia.

provide overpressure, waterhammer protection CCW Cross-Connect located in Turbine Bldg. basement floor 42" common header for all three units suction source for LPSW, HPSW, RCW coolers Emergency CCW Flowpath upon loss of power and/or loss of CCW pumps gravity flow or siphon flow from intake to Keowee tailrace upon dam failure

=>'

forced flow (one pump) from intake back to intake Skimmer Wall and Submerged Weir located at entrance to intake canal allows only cooler, lake bottom water into canal prevents draining canal following dam break

(At N0 KEOWEE HYDRO ONS 800..

0 LEVEL 100 SC 183 SUBMERGED WEIR SC183 SKIMMER.

WALL SC 130

79101 FULL POND 800 MAX.

ALLOWABLE 775 TO P OF 770 3

WE IR e

TOM MOF 761I EMERG. CCW DISC.

CCW-8 T. e.

A.S.

PRWCCW

-9 U I U2 u3' Re~~

/eR SSF 11 W. H.

IR W

CCW discharge to lake Unit 1 Unit 2 Unit 3 Cond.

main C

Cond.

main Cond.

main cooler condenser coolers cooler condenser cooler condenser CCW-crossover Sucion to Unit 3 LPSW Suction lo SSF.

feedwat CCW pumps and discharge valves 1A IB IC ID 2A 2B 2C 2D 3A 38 3C 30 CCW-intake--......-...........-

Ii..

OSFD-I133A-1 STRUCTURE__POs________RE CT YP IO/FRIM TO/FROM I11fF RUl OF 4)

UNI I 1.141 1 2 UN41T 3 CCV PUMP CCV PUMP CCV PUMhP TDISCHARGE DISCHARGE DISCHARGE 1

11 A

TO RCV COOLERS TO AIDL UIT1 UNIT 3 ~s FO srAxFO AVSETO RADVASIE 3CC-4 2CV4 SERVICE WATER -

0 TO SSr AUX FAILT 39 FACILITY 3fL -iao (4.1411 2 ONtL Y) 310 I* SERVICE VAEECSS~h'~

1 C SYSTEM

-2 r X2 6 6

( U I T 2,D N L )

( N O T E 2 )

3 9(

N O T E 2 )

1 0 R V T O U N I T1 S T O U N I T S T

C

[p(P(pCOUILERS I L.2 1 L TOTRC TOC &IOPFR D) t -

PE SV C1 16'1 1. I'tSV L.

uNIT 3 COOLERS (TOY IPICLiff 4 2 2

(UNIT ?)

IPSV v;MV LPSV (1.1411 3)

C NG.

75tNI A

31.PSV 3CCV VACUUM PRIMING -

LAKE AEVEL) 9 ATER PUMP 72--

3C _ ___

SEE ETAI AT IGHTCCV CROSSOVER DETAILS (S04 W ALL UNITS)

'15 s

FOMF HPSV COOLERS (EER FIlL' PUMHP TURBINE WSV-184

.LS

(~) ~ (j

.. ~)

~

)

l~)-.O OIL CEnIER PUMP A2~

(HC2EER FOV PUMP

_______TURLBINE OIL COOLER

-C

-c

-OD

<D

<Dc NOTO 10+

W*

-89 1423 El 24SHARED 84 s8I' ALL UNITS

_________I Y EMR CCV ICAG I4 TO INTAKE C ANAL 2CCV-7(UNIT

2)

I CV9 (EL EVATION 7601) 67 ~ ~~~~

EMMRWlcw9(NI

)[ER CCV DIISCHIARGE

-*10 KEOVEE TAIIRACE 2CV77Lll 2)DI RROV

________0 0_

~~4 C

COOLERS L LPSV IC-B14TI 2CCV-71(l~ ~ ~ ~ ~~ICV6ICNr 2)CV1SAE)(LEAIN70)(

2CCV-70CUNII

3) 70 7

AIMOSPHER*ATHSPIE RE ATMOSPHER TO CONTNUm TO CDI4TIMOUS NOTES VACUAUM PRIMING 4

• VACUUM PRIMING

1. THESE VALVES ARE MANUJAL AND NORMALLY OPEN rVOR UNITS 2 L. 3 TO MAIN 0MI Z.

UNITS 2 &. 3 CONNECT TO PO4s VAC-4 TO11S A L.

I DISCH4ARGE HEADER TO CONTITOJUS DISCHARGE T

OINU VACUU PRIING ANALTYPICAL FOR UNITS L Z L 3 ALL VALVES

'CCV' EXCEPT AS NOTED

875*-do SURGE 804'-er 8ol-c1 8c1--l 1/gs(UNfTS #2&3) 777'--11 7991-O p

79*5f7 07C 791

• -If-793*mf igodM W.w 780-*&

ss 760' SUPPLY 79-f770*-Ef 770

'-774--U 7*

767 MlTAKIE 781'--T 759-(f 757*-.3 780-d 759'-IT 756-Or D~HREOCONEE C C W 754*

M___ FULL POND EL. 800 Lr3L-EL.775 -

LENGTH = 395' t LENGTH= 36di @EL. 7 70.z 04 LAKE KEOWEE O'C.W.

INTAKE 0!0 2.5 4

EL. 732 EL. 725 SUBMERGED WEIR EL. 800.5 I

L...

I"'oIr.jIJ 2

2 EL. 710 310' EL. 733 SKIMMER WALL

TO HPSW

~.

EAST YARD HEADER WEST YARD TO UNIT 1.2 HEADER 16" LPSW '8 HEADER IG HPSW W LINE HEADER 1 6' I

FROM HPSW 14' 1 G' PUM" A U

I

'2, TDEFW PUMP TDEw J'1).

TDEPW PUMP

-0*---LPSW 'A' HEADER MHPSW M LINE HEADER JDCKEY PUPP A.UNr 2 HP PUMP COOLERS UNIT I HPT PUMP COOLERS 4

16 4"

"O FLOOR AUXILIARY BUILDING HELER tS"6 16 6.

4-EUPENT & CABLE RO.WS HEADER 4

EA T YARDg 164-2ST FLOOR AUXILIARY BUILDING HEADER 6" EA0TH SARO a6 -

4-ISFLOAULIRBIDNGHDE HEADER FRTO UNIT 3 HPI PUP B PUMP COOLERS is*

16I S1 WEST YARD HEADER 16" 12 6"

TO PUMPS 100.000 GALLON 19" ELEVATED WATER STORAGE TANK 18*

1I" 12' 100KV SWITCHYARD HEADER HPSW-25

• HYDRANTS

• CT-5 TRANSFORMER MJLSIFYRE SYSTEM

• *4 WAREHOUSE

FROM kIPSW_________________

YARD HEADER P

W 3A 3A 1216 120 121 122 123 i57~c2 F IS I38 I38 271415161758FG4 FG36 P-LO ?

3C 3C 1218 128 129 130 1311159 1F66 F05 3D 3 D T2 1 32 133 134 135

-i6-oTFc3 8 FG78 HPSW-469 UNIT I CCW PLM2pS 4"i 4j 4

UNIT 2 UNIT 2 UNIT 2 UNIT 2 CCu CCW Cw CCw PLIP A PUMP B PUMPC PIR4 D 3HP ccw P MP FO S 3HPS-LAIR COOLER A ABRASIVE SEPARATORS 3HS 4

3HSW-J 1C TO TONTTAKE STR sTUcrJR

16.9 AUXILIARY SYSTEMS liC

'UNCONTROtLLED Cpp 16.9.7 KEOWEE LAKE LEVEL COMMITMENT Ensure the proper requirements are met for the following lake Keowee level ranges.

APPLICABILITY: Maintain level to ensure operability of specified systems and/or components.

NOTE: An instrument error of +/- 1.15 ft has been applied to lake levels identified in this SLC.

This is based on control room indicator or computer point being used to verify level.

Keowee personnel may be contacted to determine absolute lake level. Levels identified as ( abs) are absolute values without instrument error included.

LAKE LEVEL REQUIRED ACTION REQUIRED ACTION NOT MET A. Lake level A.1 Verify at least two A.1.1 If only one gravity a-799.25 ft.

sources of CCW are source is available, (798.1 abs) available by gravity then the LPSW system flow to the CCW cross-cannot withstand a over piping. The two single failure.

sources must come from Enter a 24 hour2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> LCO different.Oconee Units.

per T.S. 3.3.7.

A.1.2 If no gravity sources are available, then declare the LPSW system inoperable.

Enter T.S.

3.0.

B. Lake level B.1 Verify at least two B.1.1 If only one siphon

< 799.25 ft.

sources of CCW are assisted source is (798.1 abs) available by siphon available, then flow to the CCW cross-the LPSW system over piping. The two cannot withstand a sources must come from single failure.

different Oconee Units.

Enter a 24 hour2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> LCO To ensure the sources per T.S. 3.3.7.

will siphon flow to the CCW crossover piping, the CCW intake piping B.1.2 If no siphon must be maintained assisted sources water solid. For any are available, then unit to be considered a declare the LPSW source, at least 3 Ccw system inoperable.

pumps shall be running.

Enter T.S. 3.0.

11/15/93 16.9-20

LAKE LEVEL REQUIRED ACTION REQUIRED ACTION NOT MET B. (Continued)

B.2 For any Oconee unit with B.2.1 Declare the ECCY Lake level an RCS temperature a 250 system inoperable

< 799.25 ft.

'F, verify at least 3 per T.S. 3.4.5 on (798.1 abs)

CCW pumps are running to the applicable ensure the flow through Oconee unit.

the condenser portion of the ECCW (second siphon) is operable.

C. Lake level C.1 Declare the Keowee C.l.1 Notify Compliance of

< 796.65 ft.

Step-up Transformer the need to meet (795.5 abs)

Mulsifyre inoperable the reporting AND requirements of SLC Refer to SLC 16.9.2 16.9.2.

to establish required firewatch.

D. Lake level D.1 Verify at least two D.1.1 If only one siphon

< 790.15 ft.

sources of CCW are assisted source (789 abs) available by siphon flow is available, then to the CCW crossover the LPSU system piping. The two sources cannot withstand a must come from different single failure.

Oconee Units.

To ensure Enter a 24 hour2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> the sources will siphon LCO per T.S. 3.3.7.

flow to the GCW crossover piping, the CCV intake piping must be maintained D.1.2 If no siphon water solid. For any unit assisted sources to be considered a source, are available, then all 4 CCV pumps shall be declare the LPSW running.

system inoperable.

Enter T.S. 3.0.

D.2 For any Oconee unit with D.2.1 Declare the ECCW an RCS temperature a 250 system inoperable

• F, verify all 4 CCV per T.S. 3.4.5 on pumps are running to ensure the applicable the flow through the Oconee unit.

condenser portion of the ECCW (second siphon) is operable.

E. Lake level E.1 Prior to lake level E.1.1 Declare the

< 787.40 ft.

decreasing below 787.40 affected unit (786.25 abs) close valves (1)(2) unavailable as a 3CCW-319 and (1)(2) siphon assisted 3CCW-320 source. Refer to item D. above.

11/15/93 16.9-21

LAKE LEVEL REQUIRED ACTION REQUIRED ACTION NOT MET F. Lake level F.1 Restore lake level to F.1.1 The LPSW system

< 785 ft.

greater than 785.

cannot withstand (783.85 abs) a single failure.

Enter a 24 hour2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> LCO per T.S.3.3.7.

SURVEILLANCE:

Keowee Lake Level shall be monitored once per shift.

BASES:

The CW system provides the suction source to the CCW crossover piping which supplies suction to the LPSW system. Normally this crossover header is aligned to all three Oconee Units and any operating CCW pump can provide adequate flow for the requirements of the LPSW systems for all 3 units. During certain analyzed accident conditions, a loss of power to the CCW pumps for all 3 units must be assumed.

This results in a loss of forced flow to the CCW crossover header.

With lake level greater than 799.25, lake water will gravity flow from the intake structure to the CCW crossover piping and provide an adequate suction source to the COW crossover piping through an idle CGW pump and a single open discharge valve. However, due to a potential single failure, which could close all the CCW discharge valves associated with one Oconee Unit, two Oconee Unit's CCW intake must be available to supply this suction source.

With only one CCW source available, the LPSW system cannot withstand a single failure. Therefore, a 24 hour2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> LCO must be entered-per T.S. 3.3.7.

With the lake level less than 799.25, gravity flow alone may not provide adequate flow to the CCW crossover piping. Because of this, siphon flow must be established. To ensure a siphon flowpath will be established, at least one unit's CCW piping from the intake structure to the CCW crossover, must be maintained water solid. For lake levels between 799.25 and 790.15, this is assured by maintaining at least three CCW pumps running for each Oconee Unit being used as a source.

In the event lake level falls below 790.15, the "water solid" CCW pipe requirement can be met by running all four CCW pumps on an operating Oconee Unit.

Again, due to a potential single failure associated with the CCW discharge valves, two Oconee Units should be aligned to supply siphon assisted flow to the CCW crossover piping. A 24 hour2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> LCO should be entered per T.S. 3.3.7 if only one source is available.

The minimum number of running CCW pumps required to provide siphon flow to the CCW crossover piping as described above will also ensure operability of siphon flow through the condenser, also known as the "second siphon".

If any Oconee Unit fails to maintain the minimum number of CCW pumps running when the RCS is heated above 250'F as described in items B and D, 11/15/93 16.9-22

then the ECCW system for that unit must be declared inoperable per (Technical Specification 3.4.5.

Should lake level fall below 796.65, the Keowee main Step-up Transformer Mulsifyre system may not provide the required flowrates. For this reason, the Mulsifyre should be declared inoperable and the appropriate compensatory actions taken.

Should lake level fall below 787.40, a postulated pipe break (due to a seismic event) downstream of valves (1)(2)3CCW-319 and (1)(2)3CCW-320 could cause a loss of the siphon supply to the CCW crossover for any unit which has these valves open.

For this reason, it should be verified that the two units being utilized for meeting the requirements of D.1 have their respective Radwaste supply valves closed prior to lake level decreasing below 787.40.

With lake level below 785, the LPSW pumps could experience inadequate NPSH with siphon flow from the GCW intake. Calculations show this could occur if a single failure causes the minimum number of LPSW pumps (one for Unit 3 or two for the shared Unit 1 and 2 systems) to be available during a design basis event. Therefore, the LPSW system must be considered unable to withstand a single failure for lake level below 785 and a 24 hour2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> LCO must be entered per T.S. 3.3.7. Action should be initiated to raise and maintain Keowee lake level >785.

The level of 785 for LPSW system operability is based upon testing performed to determine the level required to ensure adequate NPSH to the LPSW pumps during worst case accident configurations.

This testing in conjunction with flow model calculations determined that this lake level would be sufficient to maintain the LPSW systems operable, provided additional steps as identified by procedural guidance to the operators were utilized.

"UNCONTROLLED COPY" 11/15/93 16.9-23

REFERENCES:

1.

PIR 0-092-0535

2.

Calculation OSC-5018, Rev. 1

3.

Units I and 2 LPSW System Flow Test, TT/l/A/0251/21

4.

CCW Design Basis Document

5.

Calculation OSC-2895, Rev. 3

6.

Technical Specification 3.7

7.

Calculation OSC-5325

8.

PIR-4-090-0109

9.

PIP-7-093-0384

10.

Calculation OSC-5304

11.

Calculation OSC-5022, Rev. 1

12.

Calculation OSC-2280, Rev. 4

13.

Technical Specification 3.0

14.

Technical Specification 3.3.7

15.

Calculation OSC-5461 STATION MANAGER APPROVAL 14& -

Move

? DATE //*/j 11/15/93 16.9-24

SURGE 80O*-4 1 sol1-7 uf (UN4IT #I so0-c 1O- /8(U~rT

1. 2&3) 791*-Cf 791

• r 7 g

-r RETURN LPSW 78*- df SF 779'-cf SUPPLY 780' 9-Id*0 7

770'770 767*

4.4 759*-(f75.

DISCHARGE OCONEE C C W 5*