ML20198E594

Proposed Change Number 482 to Application for Amends 174 & 160 to Licenses NPF-10 & NPF-15.Amends Revise TS 3.7.5, AFW Sys & Bases to Indicate Turbine Driven AFW Pump Is Operable When Running in Manual Mode to Shutdowns & Testing

ML20198E594
Person / Time
Site:	San Onofre
Issue date:	01/05/1998
From:	Nunn D SOUTHERN CALIFORNIA EDISON CO.
To:	NRC
Shared Package
ML20198E586	List: ML20198E581 ML20198E594 ML20198E605
References
NUDOCS 9801090159
Download: ML20198E594 (10)

Text

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,- ,. UNITED STATES OF AMERICA ,

NUCLEAR REGULATORY COMIS$10N t

Application of SOUTHERN Calif 0kNIA  :

EDISON COMPANY, E h. for a Class 103. Docket No. 50-361 License to Acquire, Possess, and Use a Utilization Facility as Part of Amendment Application

- Unit No. 2 of the San Onofre Nuclear No. 174 -!

Generating Station _

SOUTHERN CAllFORNIA EDISON COMPANY, H R . pursuant to 10 CFR 50.90, hereby j submit Amendme.i Application No. 17,. This amendment application consists of l

. Proposed Change' Number NPF-10-482 to facility Operating License No. NPF-10.

Proposed Change Number NPF-10-482 is a request to revise Technical l Specification 3.7.5"Auxiliaryfeedwater(AfW) System"anditsBasesto  !

indicate the turbine driven AfW pump is OPERABLE when running in the manual mode to support plant startups, shutdowns, and testing.  ;

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Subscribed oh this day of . Mti dh t . 1998.

J Respectfully subrnitted.

-SOUTHERN CALIFORNIA EDISON COMPANY h

By: .

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DwightE.Nudi Vice President

$ tate of California County of San Otego 3 On - ! I$ h before me, f SbMD lbblN ,

personally appeared IhI~ - k/ , personally known to me to be the person whose name is subscribed to the within instrument and acknowledged to me that he executed the same in his authorized capacity, and that by his signature on the instrument the person,-or the entity upon behalf of which the person acted, executed the instrument.

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WITNES$ hand and official seal.

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UNITED STATES Of AMERICA NUCLEAR REGULATORY C0ltilSS10N  ;

Application of SOUTHERN Calif 0RNIA EDIS0N COMPANY, H R. for a Class 103 Dotket No. 50-362 License to Acquire Possess, and Use aUtilizationfacilityasPartof Amendment Application Unit No. 3 of the San Onofre Nuclear ilo, 160 Generating Station SOUTHERN cal.lf0RNIA EDISON C0liPANY, H R . pursuant to 10 CFR 50.90, hereby submit Amendment Aoplication No.160. This amendment application consists of Proposed Change Number NPf-15-482 to facility Operating License No. NPF-15.

Proposed Change Number NPF 15-482 is a request to revise Technical Specification 3.7.5 " Auxiliary feedwater (AfW) System" and its Bases to indicate the turbine driven AfW pump is OPERABLE when running in the manual mode to support plant startups, shutdowns, and testing.

i V [AAIL/tru Subscribed o'n this day of . 1998.

J Respectfully submitted, ,

SOUTHERN LAllf0RNIA EDIS0N COMPANY B '

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Dwight E. Nurb Vice President State of California N '

Counir of San Diego q

On b before .1 M4 ihne In 6,'1f.P. '

personally appeared i lbit/ _

, personally known to me to be the person whose name is subscribed to the within instrument and acknowledged to me that he executed the same in his authorized capacity, and that by his signatute on the instrunent the person, or the entity upon behalf of which the person acted, executed u e instrument. ' - - -

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. . 1-Enclosure DESCRIPTION AND SAFETY ANALYSIS Of PROPOSED CllANGE NPf-10/15-482 Proposed Change Number 482 (PCN 482) is a request to revise the San Onofre Units 2 and 3 Technical Specification {TS) 3.7.5 " Auxiliary feedwater (AfW)

System" and its Bases to indicate the turbine driven AfW pump is OPERABLE when running in the manual mode.

l Existino Specifications: i Unit 2: See Attachment "A" Unit 3: See Attachment "B" i Revised _ Specifications:

Unit 2: See Attachment "C" Unit 3: See Attachment "D" 1MMM&RY of CHANGE PCN-482 is a request to add a note to TS 3.7.5 to declare the steam driven AfW pump OPERABLE when it is running and controlled manually.

A discussion is being added to the AfW System Bases, B 3.7.5, to 3rovide the need and basis for the note. This note is necessary because if t1e steam driven AfW Pump is manually actuated and operating when a Main Steam Line Break (MSLB) occurs, the steam driven AfW pump turbine can trip on overspeed.

The best estimate is that the steam driven AfW pump operates approximately 500 minutes per year to support start-ups, shutdowns, and testing. Operating the steam driven AfW pump in manual operation for 500 minutes / year results in  ;

a net reduction of the core damage frequency (CDF) of approximately 2E-10/yr.

The steam driven AfW pump will be available for all other required uses while operating in manual.

. SYSTEM DESCRIPTIOR The auxiliary feedwater system su) plies feedwater to the steam generators during normal plant startup-and slutdown. During emergency conditions the auxiliary feedwater_ system automatically supplies feedwater to the steam generators to _ remove reactor decay heat- and to cool down the reactor coolant system. : The system is described in Section 10.4.9 of the Updated final Safety ,

Analysis Report.

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'A flow diagram of the auxiliary feedwater system is shown in Attachment E to this PCN. -Major components of the auxiliary feedwater system include three required 100% capacity auxiliary feedwater pumps and associated piping,_

valves,'and instrumentation.

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, . 2-Two of the three auxiliary feedwater pumps are driven by separate electric power sources. Each pump feeds one steam generator through a set of valves powered from the same lE AC power source as the pump motor. The horizontal centrifugal pumps are each capable of delivering a minimum of 500 gpm at a Steam Generator pressure of 1097 psia to meet Accident Analysis flow requirements. Each pump is also capable of delivering 700 gpm at a Steam Generator pressure of 890 psia to support cooldown requirements.

A turbine driven auxiliary feedwater pump, identical to the motor-driven pumps except the pump driver, provides overall system redundancy of auxiliary feedwater supply and diversity of motive pumping power. The ) ump is a horizontal, centrifugal unit. (Cooldown requirements during lot shutdown are The turbine driven pump is met byindependent totally operating one of ACofpower the motor driven ind can pumps.)h steam generator through two feed eac sets of valves powered from 125 V DC IE power sources. Each set of valves aligned to a steam generator from the steam driven auxiliary feedwater pump is powered from the opposite train from the valves from the corresponding electric driven auxiliary feedwater pump. The auxiltery feedwater pumps are located in separate areas of the auxiliary feedwater pump room at elevation 28 feet, in the tank building close to the condensate storage tanks.

Each pump is equipped with manually-operated isolation valves at the pump suction and discharge. These valves are used for maintenance only and are locked open during normal operation. Check valves are located in each pump discharge line to prevent backflow through a shutdown pum) in the event of a loss-of pump failure. The auxiliary feedwater lines in tae motor driven feedwater pump trains are equipped with motor-operated isolation valves powered from the same AC power source t.s the pump motor. They are also equipped with AC electrohydraulic bypass control valves and AC electrohydraulic isolation valves. The auxiliary feedwater lines in the turbine driven auxiliary feedwater pump train are equipped with DC motor operated control and isolation valves. The lines that supply water to the auxiliary feedwater pumps from the condensate storage tank are equipped with manually-operated gate valves at the storage tanks, which are normally locked open, parallel isolation valves are provided in the auxiliary feedwater line to each steam generator outside the containment; one of each valve in parallel is AC powered, the other is DC-powered. Subject to certain exceptions stated in the Technical Specifications, all manual valves in the auxiliary feedwater system are required to be in the correct position and all automatic valves (except bypass valves) are required to be capable of opening upon actuation of the Emergency feedwater Actuation Signal (EFAS) and closing upon actuation of a Main Steam Isolation Signal (MSIS).

DlEh51Qlf An overspeed trip of the steam driven Auxiliary feedwater (AFW) pump (P140) may occur if the steam driven AFW Pump is manually actuated and operating when a Main Steam Line Break (MSLB) occurs and causes a MSIS actuation befne an EFAS. This overspeed trip occurs for the following reason:

If the Trip / Throttle valve (HV-4716) is open when the MSLB occurs, the MSIS will close both steam inlet valves (HV 8200 & 8201) and the AFW pump turbine will coast to a stop with HV-4716 and the Governor Control

, 3-Valve ($V 4700) open. In time, depending on the specific accident conditions, EFAS will actuate to deliver water to the intact steam generator and at least one steam inlet valve will open (HV 8200 and/or ,

HV 8201). The steam enters the turbine with HV 4716 and SV 4700 open. '

The turbine will accelerate and SV 4700 will close to regulate speed.

The outcome will be a timing race that can result in the steam driven AIW pump turbine tripping on overspeed.

SuppprJ1Dg_htalysis Summary Probabilistic analyses have been performed in support of declaring P140 operable when the pump is manually actuated and operating. The core damage frequency (CDf) for operation with P140 in standby and in test are compared.

The results are shown in the following table:

P 14C running P-140 in standby Difference (for an entire year) (for an entire year) (running-standby)

MSLB/FWLB 6.55E-7/yr 6.12E-7/yr 4.3E 8/yr Other 2.57E-5/yr 2.60E 5/yr -3E 7/yr Initiating Events Total CDF 2.64E 5/yr 2.66E-5/yr -2E 7/yr ear, the lhe coreresults damageshow risk ofthat, considering a Main Steam LineP-140 Breakto be in testLine

/feedwater for Break an entire (MSLB y/FWLB) slightly increases (4.3E 8/yr) while the risk due to other initiating events decreases (3E-7/yr). The not core damage impact of P-140 in test for an entire year is a CDF decrease of 2E-7/yr. Having P140 operating instead of being in standby increases its reliability. This increased reliability reduces the risk due to other initiating events, such as loss of main feedwater, medium and small loss of Coolant Accidents (LOCAs), Steam Generator Tube Rupture (SGTR), and Loss of Offsite Power (LOP), which require AfW and which occur with much greater frequency than MSLB/fWLB. With the overall CDF reduction a result of considering P140 being in a test configuration for an entire year, the actual cumulative risk incurred is the weighted fraction that P140 is in the test configuration over a year period. Based on past experience, the pump is run in manual operation approximately 500 minutes / year, which results in an annual net cumulative CDF reduction on the order of 2E-10/yr due to running in manual mode.

The core damage risk due to external events (such as earthquakes) while testing P140 is also reduced since an external event induced MSLB/fWLB is unlikely. In the San Onofre 2/3 Individual Plant Examination of External Events (IPEEE), a seismic induced MSLB/fWLB was screened due to the seismic ruggedness of the main steam and feed line piping. Seismic induced events such as a LOP benefit by having P140 initially running. The net result of having P-140 operating in test is a risk benefit.

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. . 4-Additional Supportino Information j Consistent with draft Regulatory Guide DG 1061 and the use of Probabilistic  !

Analyses to support proposed changes to the current licensing basis, five  !

additional principles must be maintained. These principles are addressed as follows: l

1) Current regulations are met (or a change proposed). i This PCN seeks to consider the AFW pump operable during operation of the f AfW pump in the manual mode, i

2) Defense in depth is maintained.  !

Defense in depth is maintained and-is not impacted by this PCN. This PCN charges only the definition of operability of P 140 while operating in manual and does not change its availability to perform as designed.

3) Sufficient safety margins are maintained. '

Sufficient safety margins are maintained and are not impacted by this PCN. This PCN changes only the definition o' operability of P-140 while >

operating in manual and does not change the system's design margins or safety margins.

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4) Pro)osed increases in risk and cumulative impact must be small and wit 11n safety goals. ,

t This PCN changes only the definition of operability of P-140 while in test and does not change the base core damage risk. The basis for the change in definition of operaole is based on the reduction in overall CDF when P140 is operating in manual. .

5) Performance based implementation and monitoring must be used.

Performance of P140 is currently and will continue to be monitored under the Maintenance Rule and its attendant performance criteria.  ;

Conclusion Because P140 will-perform its design functions under all circumstances with the one exception, described above, considering a running pump inoperable is a -

source of confusion to the Operations staff. Also, is previously discussed, f the probability of the overspeed trin as described above is very low. The  ;

overspeed trip protects the pump from damage allowing for a restart by -

Operations following the tri assumed in the CDF analysis)p (The operating steam driven pump is morethe restart o

reliable for conditions such as LOCAs, SGTR, and LOP. Southern California Edison's' determination is that, given the current design of the AFW system, '

overall plant safety is enhanced, rather than reduced, when P140 is operating  ;

in- the manual mode. 3 Therefore, the steam driven AFW pump should be considered OPERABLE when the pump is. running and controlled manually.

, . SE UY MAIU15  :

1he proposed change (escribed above shall be deemed to involve a significant hazards consideration if there is a positive finding in any one of the following areas:

1. Will operati of the facility in accordan" with this proposed change involve a si9 ficant increase in the prob.cility or consequences of an accident previously evaluated?

Rewonse: No Probabilistic analyses have been performed in support of declaring P140 operable when the pump is manually actuated and operating.

The results show that, considering P-140 to be in test for an entire year, the core damage risk of a Main Steam Line Break /Feedwater Line Break (MSLB/fWLB) slightly increases (4.3E 8/yr) while the risk due to other initiating events decreases (3E-7/yr). The not core damage impact of P-140 in test for an entire year is a Core Damage frequency (CDF) decrease of 2E-7/yr. Having P140 operating instead of being in standby increases its reliability. This increased reliability reduces the risk due to other initiating events, such as loss of main feedwater, medium and small Loss of Coolant Accidents (LOCAs), Steam Generator Tube Rupture (SG1R), and loss of Offsite Power (LOP), which require Auxiliary feedwater (AFW) and which occur with much greater fiequency than MSLB/FWLB. With the overall C0F reduction a result of considering P140 being in a test configuration for an entire year, the actual cumulative risk incurred is the weighted fraction that Pl40 is in the test configuration over a year period. Based on past ex)erience, the pump is running in manual approximately 500 minutes / year, w11ch results in an annual not cumulative C0F reduction on the order of 2E-10/yr due to running P140 in the manual mode.

Therefore, the operation of the facility in accordance with this proposed change does not involve a significant increase in the probability or consequences of an accident previously evaluated.

2. Will operation of the facility in accordance with this proposed change create the possibility of a new or different kind of accident from any accident previously evaluated?

Resoonse: No This change does not involve a plant hardware modification or allow the operation of any 31 ant equipment in any way other than originally designed. This clange only affects the administrative tracking of the turbine-driven AfW pump when the steam driven AFW pump is operating in the manual mode.

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.. . 6-Th'erefore, the operation of the facility in accordance with this

')roposed change will not ' create the possibility of a new or different (ind of accident from any accident previously evaluated.

3. Will operation of the facility in a.cordance with this' proposed change involve a significant reduction in a margin of safety?

Be.iponse: No Pump history shows the pump is run'approximately 500 minutes per year.

In all cases except for the one postulated scenario of the Main Steam isolation Signal followed by an Emergency feedwater Actuation Signal the turbine driven AfW pump is not susceptible to being tri) ped. Also, this postulated scenario does not affect the capability of tie motor-driven AfW pumps.

Even though there is a small increase in the C0F from the AFW steam driven pump operating in manual mode based on the possibility of a MSLB/fWLB, also considering other initiating events results in an annual net cumulative CDF reduction on the order of 2E-10/yr due to P140 running in the manual mode.

Therefore, the operation of the facility in accordance with this proposed change does not involve a significant reduction in the margin of safety.

Safety and Sienificant Hazards Determination Based on the above Safety Analysis, it is concluded that: (1) the proposed change does not constitute a.significant hazards consideration as defined by 10 CFR 50.92 and of the public will(not be endangered by the proposed change.2) Moreover, there is reasona because this action does not involve a significant hazards consideration, it will also not result in a condition which significantly alters the impact of the Station on the environment as described in the NRC Final Environmental Statement.