ML20199D033

Suppl 1 to Amend Applications 157 & 141 to Licenses NPF-10 & NPF-15,respectively,restricting Required Action Completion Time to Close All Containment Penetrations Providing Direct Access from Containment Atmosphere to Outside Atmosphere

ML20199D033
Person / Time
Site:	San Onofre
Issue date:	01/13/1999
From:	Nunn D SOUTHERN CALIFORNIA EDISON CO.
To:
Shared Package
ML20199D024	List: ML20199D019 ML20199D033 ML20199D039
References
NUDOCS 9901190269
Download: ML20199D033 (26)

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Enclosure 3 Amendment Application Numbers 157, Supplement 1 and 141, Supplement 1 i

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9901190269 990113 PDR ADOCK 05000361 P PDR_

[ UNITED STATES OF AMERICA NUCLEAR REGULATORY COMMISSION

!- Appiication of SOUTHERN CALIFORNIA l EDIS0N COMPANY, El AL. for a Class 103 Docket No. 50-361 l License to Acquire, Possess, and Use a Utilization Facility as Part of ) Amendment Application

, Unit No. 2 of the San.0nofre Nuclear ) No.157, Supplement 1 p#

L Generating Station .) I f

l SOUTHERN CALIFORNIA EDIS0N COMPANY, El AL. pursuant to 10 CFR 50.90, hereby submit Amendment Application No.157 Supplement 1. This amendment application l consists of Proposed Change Number NPF-10-458 Supplement to Facility M  !

l Operating License No. NPF-10. Proposed Change Number NPF-10-458 Supplement 1

( is a request to change Technical Specification (TS) 3.9.4 " Shutdown Cooling l (SDC) and Coolant Circulation -- High Water Level" and TS 3.9.5 " Shutdown l Cooling (SDC) and Coolant Circulation -- Low Water Level." Proposed Change Number NPF-10-458 is a request to 1) reduce the water level in the reactor cavity during refueling outages when two loops of shutdown cooling (SDC) are required from 23 feet to 20 feet above the reactor pressure vessel flange, 2) increase the time a required loop of the SDC system may be removed from service from up to I hour per 8-hour period to up to 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br /> per 8-hour period, provided the upper guide structure has been removed from the reactor I

-pressure vessel, 3) allow for running 1 loop of shutdown cooling with 1 additional requirements when the water level is less than 20 feet but greater than 12 feet above the reactor pressure vessel flange, 4) add an action to be taken when operating 1 loop of SDC with less than 20 feet of water above the reactor pressure vessel flange when the specified requirements are not met, and 5) make editorial changes.

Supplement 1 conservatively restricts the required action completion time to close all containment penetrations providing direct access from containment

, atmosphere to outside atmosphere from "4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br />" to "4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> or within the

!. calculated time to boil, whichever is less." This change is to revise the Technical Specification to reflect the current practice at San Onofre Unit 2. f ,p(

This supplement also updates the Significant Hazards Consideration Section.

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Subscribed on this b ay of bllLbfU , 1999.

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l Respectfully submitted, SOUTHERN CALIFORNIA EDISON COMPANY I

C D h-By: ~_ s _

DwightE. Nun)

Vice President h

State of California Countyi of Sa i Diego

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On b k D k h _ befo,re me,[ ff [( d)2 L Ll148, personally appeared d lh 't h /1 U Q rsonally 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.

/\ mas ANE SANCHEZ p WITNESS'mr/hhnd and official seal.

~ Comrmson #1196482 j

_ S No*ary Pyone-C h Signatur [L ____ _

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UNITED STATES OF AMERICA NUCLEAR REGULATORY COMMISSION Application of SOUTHERN CALIFORNIA EDISON COMPANY, H AL. for a Class 103 Docket No. 50-362 License to Acquire, Possess, and Use a Utilization Facility as Part of Amendment Application Unit No. 3 of the San Onofre Nuclear ) No. 141, Supplement 1 yg l Generating Station )

SOUTHERN CALIFORNIA EDISON COMPANY, H AL. pursuant to 10 CFR 50.90, hereby submit Amendment Application No.141 Supplement 1. This amendment application consists of Proposed Change Number NPF-15-458, Supplement 1 to Facility W Operating License No. NPF-15. Proposed Change Number NPF-15-458, Supplement 1 is a request to change Technical Specification (TS) 3.9.4 " Shutdown Cooling (SDC) and Coolant Circulation -- High Water Level" and TS 3.9.5 " Shutdown Cooling (SDC) and Coolant Circulation -- Low Water Level." Proposed Change Number NPF-15-458 is a request to 1) reduce the water level in the reactor cavity during refueling outages when two loops of shutdown cooling (SDC) are required from 23 feet to 20 feet above the reactor pressure vessel flange, 2) increase the time a required loop of the SDC system may be removed from service from up to I hour per 8-hour period to up to 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br /> per 8-hour period, provided the upper guide structure has been removed from the reactor pressure vessel, 3) allow for running 1 loop of shutdown cooling with additional requirements when the water level is less than 20 feet but greater than 12 feet above the reactor pressure vessel flange, 4) add an action to be taken when operating 1 loop of SDC with less than 20 feet of water above the reactor pressure vessel flange when the specified requirements are not met, and 5) make editorial changes.

I Supplement I conservatively restricts the required action completion time to I close all containment penetrations providing direct access from containment atmosphere to outside atmosphere from "4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br />" to "4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> or within the N/i' l calculated time to boil, whichever is less." This change is to revise the Technical Specification to reflect the current practice at San Onofre Unit 3.

This supplement also updates the Significant Hazards Consideration Section.

Subscribed on this day of t O LL fL r lJ , 1999.

J Respectfully submitted, SOUTHERN CALIFORNIA EDIS0N COMPANY I

\ v By: _

Dwight E. Nunn Vice President State of California County of Sa Die o '

r on before me (([l Lh k_) UNY{ '

personally appeared b.[ bbl /L/Versonallyknown 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, M'

• SANCHEZ L WITNESS mfandandofficialseal. -f Com c.w .11pgg [

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l No*ary PwO.ic - Cofifamk2 f Signatu W, I . __ _

u 1 .2002

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l Enclosure DESCRIPTION AND SAFETY ANALYSIS OFPROPOSEDCHANGENPF-10/15-458 Supplement 1 l

l Proposed Change Number 458 (PCN-458) Supplement 1 is a request to revise San Onofre Units 2 and 3 Technical Specification (TS) 3.9.4 " Shutdown Cooling (SDC) and Coolant Circulation -- High Water Level" and TS 3.9.5 " Shutdown Cooling (SDC) and Coolant Circulation -- Low Water Level." .

l Existina Soecifications:

Unit 2: See Attachment "A" Unit 3: See Attachment "B" Revised Soecifications (Redline and Strikeout 1: l Unit 2: See Attachment "C" Unit 3: See Attachment "D" Revised Soecifications:

Unit 2: See Attachment "E" \

Unit 3: I See Attachment "F" pi Figure 1 from Calculation No. Supplement A N-0220-029, sheet A-28:

See Attachment G BASES l

Units 2 and 3: Attachment H (For Information Only)

SUMMARY

of CHANGE By a letter dated February 15, 1995, the NRC issued Amendment Nos. 116 and 105 to Facility Operating License Nos. NPF-10 and NPF-15 for the San Onofre Nuclear Generating Station Units 2 and 3, respectively. These amendments were issued for use in the Cycle 8 refueling outages only in response to amendment applications consisting of PCN 402. PCN 458, Supplement 1 is similar to PCN l 402, however, PCN 458 Supplement I requests a permanent change to the technical specifications.

PCN 458 is a request to:

1) Reduce the water level in the reactor cavity during refueling outages when two loops of shutdown cooling (SDC) are required from 23 feet to 20 feet above the reactor vessel flange, l 2) Increase the time a required loop of the SDC system may be removed

, from service from up to I hour per 8-hour period to up to 2 hcurs per 8-hour period, provided the upper guide structure has been removed from the reactor vessel,

3) Allow for running only 1 loop of shutdown cooling with additional requirements when the water level is less tlan 20 feet but greater than or equal to 12 feet above the reactor vessel flange,

j 4) Add an action to be taken when operating only 1 loop of SDC with less than 20 feet of water above the reactor vessel flange when the specified requirements are not met.

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5) Make editorial changes.

6) Revise the completion time of the required actions 3.9.4 A.4 and .gd !

3.9.5 C.3 to include the restriction "or within the calculated time l to boil, whichever is less."

l These changes will allow the required maintenance and testing to be scheduled and performed in a cost effective way, and they will potentially save Southern California Edison (Edison), et al., between 14 and 48 hours5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br /> of critical path time in future refueling outages for each Unit.

The LC0 section of the Bases B 3.9.4 states that only one SDC loop is required l for decay heat removal in MODE 6, with water level 2 23 feet above the top of the reactor vessel flange. Only one SDC loop is required because the column of water above the reactor vessel flange provides backup decay heat removal capability. The Applicability section states that the 23 foot level was selected because it corresponds to the 23 foot requirement established for fuel movement in LC0 3.9.6.

Edison has performed calculations to determine the time it would take for the water to boil with an initial water level of 23 feet above the flange,13 feet above the flange, and 1 foot below the flange. Attachment E is a figure of the heatup curves from the calculation. Additional components are required to 4 l be available by this PCN when the reactor cavity water level is 12 feet above the reactor vessel flange to be able to raise the water level to 20 feet above the reactor vessel flange in the event of a loss of SDC. Also, with the reactor cavity flooded to any level above the reactor vessel flange, Edison has demonstrated that containment closure can be achieved within 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br />, even in the event of a loss of offsite power.

Edison has performed a Probabilistic Risk Assessment (PRA), with a) one loop of the SDC system operable with the reactor cavity water level greater than or equal to 12 feet above the reactor vessel flange, and b) one loop of the SDC system operable with the reactor cavity water level greater than or equal to l 20 feet above the reactor vessel flange, to show that operating the plant within the conditions allowed by the proposed TS does not significantly

increase the probabilities of inventory boiling and core damage.

Items 1 and 2 provide a permanent solution to a testing requirement originally

, addressed by a temporary waiver of compliance from the pre Unit 2 Amendment No. 127 approved TSs 3.9.8.1 and 3.9.8.2. This temporary waiver was approved l by a letter from R. P. Zimmerman (NRC) to R. W. Krieger (SCE) dated j October 10, 1991. The request to change the water level from 23 feet to i

20 feet above the reactor vessel flange and allow the SDC system to be removed from service for testing of Low Pressure Safety Injection system components is supported by recent calculations. Additionally, specific requirements are being added to permit increasing the time the required loop of SDC may be removed from service. These changes permit the required testing to be performed without offloading any fuel from the reactor vessel.

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l l Additionally, to support the inservice testing of the Low Pressure Safety Injection (LPSI) system components and integrate the testing in the outage l plan, item 2 proposes to increase the time a required loop of the SDC system j may be removed from service from up to 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> per 8-hour period to up to i

2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br /> per 8-hour period. This inservice valve testing will add cool water to the reactor cavity at a flow rate between 5000 gpm and 5300 gpm. i Typically, each pump will run from 1 to 5 minutes during the test and will  !

increase the reactor cavit The Refueling Water Storage Tank (RWST) y water boron level by 4intoconjunction concentration 20 inches. with the flowrate l provided by the SDC pumps operating for 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> out of 8 will provide

, sufficient mixing to prevent boron stratification. The two hours allows the valve lineups and inservice testing to be performed without unnecessary urgency. A restriction is being added to prevent removing both SDC loops from l service unless the upper guide structure has been removed from the reactor vessel which assures that natural circulation heat transfer is not impeded.

Also, by lowering the required water level from 23 feet to 20 feet above the reactor vessel flange, maintenance on one SDC loop and its supporting  ;

equipment can be scheduled in conjunction with some reactor internals removal preparation work. This will save approximately 14 hours1.62037e-4 days <br />0.00389 hours <br />2.314815e-5 weeks <br />5.327e-6 months <br /> of critical path time. i Items 3 and 4 will support additional flexibility in scheduling maintenance '

outages for the SDC loops and their supporting systems. To support the PRA for naving 1 loop of SDC operable when the water is less than 20 feet above the reactor vessel flange and greater than or equal to 12 feet above the reactor vessel flange., Edison has established 8 requirements to be met and added a new action statement.

. Item 5 adds wording to the notes in LCOs 3.9.4 and 3.9.5 that was unintentionally deleted by the Unit 2 Amendment No. 127 and Unit 3 Amendment No. 116 approved Technical Specifications. l Item 6 conservatively restricts the completion time to ensure containment closure is achieved prior to the water in the cavity boiling, in the event of a Loss of Shutdown Cooling. This restriction is already a self imposed Pfl (

requirement at San Onofre Units 2 and 3. Incorporating it in the Technical l Specification only serves to highlight the importance of this requirement.

DESCRIPTION of CHANGE PROPOSED TEQiNICAL SPECIFICATION CHANGES The proposed change to the TS 3.9.4 first note under the Limiting Condition

! for Operation (LC0) and the Applicability statement for both the Unit 2 and j Unit 3 TSs follows (highlighting for additions and line out for deletions):

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1. Withithe upper;gui_de!structurej removed- from the reactor 1 vessel ~ the required SDC loop may be removed from operation for s + 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br /> per '

8-hour period, provided: no operations are permitted thet would cause dilution of the Reactor Coolant Syste, boron concentretion.

a..  ? Th'e;makimum; RCS f tempeEa tursfi s L mai ntai ned si.140 F.

Lb.. .qNoToperationsT are permitted i; hat?would cause a. reduction?of- the RCS' boron 2 concentration:

c.  ::Thefcapabilitf.toiblose theicontainment pe'netrations with direct

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accessjto:the outsidejatmospherel.within the calculated l time:to boil is, maintained.

id. . Thei reactoricavi.ty:' water: Llevelaisin iaintainedi20ifeettalio've the t_op Loflthe reactor pressurelvesself: flange, or, >for. core alterations,:32?23kfeettabovef the~ top;of;the; reactor7pressure i v' esse lt flange.

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2. A containment spray pump may be used in.pla.c_e of a l_ow pressure safety .

injection pump in?either:or bot.h. shutdown-coolingLloops :to provide shutdown cooling flow.

" APPLICABILITY: MODE 6 with the water level > M 20 ft above the top of the reactor vessel flange.

Com)letion time.on Required Action A.4.: 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> or withinith'eTcalculate'd time ht/

to joilkwhichever is11essi The proposed change to TS 3.9.5 will revise the LCO, the Applicability statement, and the Action Statement for both the Unit 2 and Unit 3 TSs, as follows:

LIMITING CONDITION FOR OPERATION l LC0 3.9.5 Two SDC Loops shall be OPERABLE and one SDC loop shall i be in operation.

NOTE l LA; containment 1 spray; pump.mayJbelused in: place?of.':a low pressure .

! safety injection pump inLeitherLor..both; shutdown 4 coolingsloopsfto l provide shut'down cooling' flow, t

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, ?0rielloopiffshutd0wnlcoolingishallibe'.l0PERABLE and . operating under the

. fol. lowing conditions.:

- ll)i jTheTreactorfhas.been' shut'ownifor.;atTleast-6 d days!

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'2)-l : Ths;waterilevelfabove:theTreactor. vessel flange is 12 feet or g reater_.

3)j iTh'e assodiated Lloop. of Salt Water CoolingI(SWC) is OPERABLE and operating.

L4)j ~TheLassociated Component Cooling. Water:(CCW)' pump andithe CCW swing i

pump.~are OPERABLE, and the' associated;.CCW: loop is. OPERABLE and operating' .

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5) 1TheShutdownCdolingisystemisoperatingusingthe1containmentspray l pump,.and-the associated high. pressure safety injection pump'and the low pressure..; safety injection: pump 'are- 0PERABLE: and. at: ambient temperaturekavailable for{ injection from'.the RWST.

(6) LThe~;RWST contains[thej vo1~ume of twater: requireditoiraise the; level;to

20. feet.above.;the reactorEvessel" flange;

<7)2 The ass'ociated' Emergency Dies'el Generator?isj 0PERABLE.

18)? iThe water temperature;offthe SDC.syst'emLis'; maintained.less'than

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120PF.

APPLICABILITY: MODE 6 when the water level above the top of the reactor vessel flange is less than M 20 feet.

ACTIONS:

A statement is being added to Action "A" that will limit the

! applicability of Action "A" to initial conditions of two shutdown j cooling loops OPERABLE A new Action "B" is being added for the conditions when only one SDC loop is OPERABLE and the Reactor Cavity water level is less than 20 feet above the reactor vessel flange. This new Action statement will require immediate action to establish greater than or equal to 20 feet of water above the reactor vessel flange if any of the required conditions (1 through 8) are not met.

The current Action "B" will become Action "C."

Completion time for the new C.3: 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> or withinTthe calcula'ted time 3.yp/

to boil,:whichever;is less; The revised Bases B 3.9.4 and B 3.9.5 are included as Attachment F for your information.

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l l l SYSTEM DESCRIPTIONS The purpose of the Emergency Core Cooling System (ECCS) is to inject borated water into the Reactor Coolant System (RCS) to cool the core following a Loss of Coolant Accident (LOCA) and to maintain the reactor subcritical following a LOCA or a Main Steam Line Break (MSLB).

The ECCS system includes three High Pressure Safety Injection (HPSI) pumps,

! two Low Pressure Safety Injection (LPSI) pumps, and two Containment Spray (CS) pumps. These pumps are in two redundant and independent loops. The third HPSI pump is a swing pump which can be aligned to either loop.

The two LPSI pumps also provide SDC flow through the reactor core and the SDC system heat exchangers for shutdown plant cooling or for long term cooling for small break loss of cooling accident scenarios. Also, as the result of a recent design change, the containment spray pumps may be aligned to be used in place of a LPSI pump in either or both shutdown cooling loops to provide shutdown cooling flow.

l BACKGit0MQ Limiting Conditions for Operation (LCO) in TSs 3.9.4 and 3.9.5 define the operability requirements for the SDC system during refueling operations l (Mode 6) while the water level above the top of the reactor vessel flange in the reactor cavity is at least 23 feet and less than 23 feet, respectively.

The objective of these TSs is to ensure that 1) sufficient cooling is

! available to remove decay heat, 2) the water in the reactor vessel is

! maintained below 140*F, and 3) sufficient coolant circulation is maintained in the reactor core to minimize boron stratification leading to a boron dilution incident.

Prior to the approval of Unit 2 Amendment No. 127 and Unit 3 Amendment No. 116, Technical Specification Bases Section 3/4.9.8 has stated that "With the reactor vessel head removed and 23 feet of water above the reactor vessel flange, a large heat sink is available for core cooling, thus in the event of a failure of the operating shutdown cooling loop, adequate time is provided to initiate emergency procedures to cool the core."

In the Bases for the New Standard Technical Specifications, NUREG 1432, l Revision 0, dated September 30, 1992, Section B 3.9.4 it is stated that; "The

! 23 ft level was selected because it corresponds to the 23 f t requirement established for fuel movement in LC0 3.9.6, " Refueling Water Level."

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Edison Calculation N-0220-029 was performed to address action items identified in an Edison assessment of NUMARC 91-06 " Guidelines for Industry Actions to Assess Shutdown Management," December, 1992. Calculation N-0220-029 provides time to boil and time to uncover the core curves based on several plant conditions over a 90-day period following reactor shutdown. These plant conditions include various water levels (from 17 inches above the bottom of the hot leg to 23 feet above the reactor vessel flange, Steam Generator (SG) tubes empty and full, and SG nozzle dams installed and not installed). The results of this calculation are used to determine containment closure requirements for the various Mode 5 and Mode 6 configurations. These curves are used by the outage planning team to plan refueling outages with " Defense in Depth."

The primary consideration in planning outages at San Onofre is safety.

" Defense in Depth," based on NUMARC 91-06, is the concept used in outage planning to ensure sufficient equipment, including instrumentation, is maintained available to provide both a primary and an alternate or backup method for control of each of the Shutdown Safety Functions. Operations verifies each day during an outage that this equipment set is available as planned.

Defense in Depth planning includes:

o Providing systems, structures, and components to ensure backup of Shutdown Safety Functions using redundant, alternate, or diverse methods; e Planning and scheduling outage activities to optimize safety system availability; Providingadministrativecontrolsthatsupportand/orsupplementthe above elements.

%. The Edison Nuclear Safety Group performs a comprehensive outage safety assessment based upon an expanded version of our Individual Plant Examination (IPE) for each refueling outage. The purpose of this assessment is to evaluate the probability of either fuel damage or inventory heatup during the various plant configurations throughout the outage, including reduced inventory operations, fuel transfer operations, Spent Fuel Pool operations during full core offload, and midloop operations with the reactor fueled. If the results of the outage safety assessment indicate a higher probabilistic risk than is desired, compensatory measures are implemented or plans are changed to reduce the risk to acceptable levels. The results of these evaluations have led to plant configuration changes or outage sequence changes in the last several refueling outages, which yielded significant gains in shutdown safety.

DISCUSSION General The proposed savings identified which initiated this request for a TS change were made possible, in part, due to the recent SDC design change which allows the SDC system to be cross-tied with the containment spray system (Edison Projects 2-6863 and 3-6863). The NRC approved the cross tie design change by License Amendments 106 and 95 for Units 2 and 3, respectively. Now that this capability exists, cost savings due to reduced outage times are possible. The reduction of the required water level from 23 feet to 20 feet will potentially save approximately 14 hours1.62037e-4 days <br />0.00389 hours <br />2.314815e-5 weeks <br />5.327e-6 months <br /> of outage time. The additional change requiring only 1 loop of SDC operable with the water level 12 feet or greater above the reactor vessel flange will save approximately another 34 hours3.935185e-4 days <br />0.00944 hours <br />5.621693e-5 weeks <br />1.2937e-5 months <br /> of outage time.

The expected savings associated with PCN-458 is between 14 and 48 hours5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br /> of outage time during future refueling outages at each unit.

i Probability Risk Assessments (PRAs) were performed to assess the risks of inventory boiling and core damage with using the proposed technical specification change for operating with the water level at 12 feet above the i

vessel flange or greater. The risks of inventory boiling and core damage were calculated to increase by 1.5 X 104per day and 6 X 10 4 per day, l respectively, from the current TS requirements.

The proposed TS changes in this PCN are requested to reduce outage durations.

The required water level to move fuel will still remain 23 feet above the reactor vessel flange as specified in TS 3.9.10. Our intent will always be to operate in a safe condition and plan according to a Defense in Depth philosophy. Prior to each outage the Defense in Depth philosophy is used to plan the work required during an outage. The required Mode 5 and Mode 6 configurations are compared to the assumptions in Calculation N-0220-029 and evaluated to ensure plant safety margins are maintained. Therefore, utilizing the calculations and the Defense in Depth philosophy in outage planning, plant safety is maintained throughout all evolutions of the refueling outage.

Pronosed Chanaes: Items 1 and 2 The request to lower the required water level from 23 feet above the reactor vessel flange to 20 feet above the reactor vessel flange and to increase the time the SDC system is allowed to be out of service from "s 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> per 8-hour period" to "s 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br /> per 8-hour period" is necessary to allow for the addition of water to the reactor cavity and for adequate time to set up and perform testing of LPSI system components (e.g., Inservice Testing of the LPSI pump suction check valves).

This change will allow this test to be performed in conjunction with the

normal reactor cavity fill evolutions during a refueling outage without

requiring the core to be offloaded from the reactor vessel _. Specifically

! stating that the upper guide structure will be removed assures that natural l heat transfer is not impeded. This requirement was requested by the NRC

during the review of PCN 402.

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l This change allows the SDC system alignments to be made and the tests to be  ;

l completed as part of an integrated outage plan. The time the SDC system is l

, allowed to be secured is increased to 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br />, but during the short test the ,

water level is being increased by approximately 4 to 20 inches with a high  !

flow rate of cool borated water from the RWST. The 6-hour period following the test that the SDC system would be required to run is adequate to provide j mixing and prevent boron stratification. The 2-hour period will allow the required valve lineup changes and the test to be performed without unnecessary urgency.

The reduction in the required water level from 23 feet to 20 feet above the <

reactor vessel flange will also allow one loop of SDC and the supporting loops of Component Cooling Water (CCW) and Salt Water Cooling (SWC) to be removed from service and still allow some reactor internals removal preparations to be l performed. Currently, the loop outages would have to be delayed approximately 14 hours1.62037e-4 days <br />0.00389 hours <br />2.314815e-5 weeks <br />5.327e-6 months <br /> to allow the reactor internals removal preparations to reach the point when the reactor cavity can be filled to 23 feet above the reactor vessel flange.

The reduction of water from 23 feet above the reactor vessel flange to 20 feet l above the reactor vessel flange is a small change and has little impact on the i time to boil (4.0 hours0 days <br />0 hours <br />0 weeks <br />0 months <br /> to 3.5 hours5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br /> at six days following the reactor ,

shutdown). The basis of having a sufficient heat sink to provide core cooling and allow time to take other actions to cool the core in the event of losing the operating loop of SDC is still maintained. J To assure the objectives of TS 3.9.4 are satisfied during performance of the testing of LPSI system components the following requirements will oe met: '

1) The periods in which a SDC loop is not in operation will be limited to s 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br /> per 8-hour period, provided the upper guide structure has been removed from the reactor vessel,

2) The maximum RCS temperature will be maintained s 140*F.

3) No operations will be permitted that would cause a reduction of the RCS boron concentration.

4) The capability to close the containment penetrations with direct access to the outside atmosphere within the calculated time to boil will be maintained.

i 5) The reactor cavity water level will be maintained greater than or I equal to 20 feet above the reactor vessel flange.

With no SDC system operating the above described compensatory measures provide assurance that performance of the full flow LPSI pump suction header check valve test is of no safety consequence.

1 i

l .

l l l The maximum RCS temperature is maintained s 140 F. The two hours is sufficient time to align the system to test, perform the t'st, and restore the loop of SDC to operation prior to exceeding 140 F. The in,tial conditions and heatup rate are selected such that RC5 temperature remains s 140 F during the test. Typically, the reactor cavity water initial temperature will be less than 100 F. In the request for the October 10, 1991, waiver of compliance, the increase in the RCS temperature without SDC in operation due to decay heat was estimated to be a maximum of 2.6 F per hour. During the Unit 2 tests the SDC system was secured twice, once for 18 minutes and once for 15 minutes.

During the test, cool borated water from the RWST was introduced to the RCS and resulted in an increased inventory, effectively providing a source of core cooling. The flow rate during this test was between 5000 gpm and 5300 gpm.

The reactor cavity water level increased one inch for every 1260 gallons of water added, a rate of 4.2 inches per minute.

No operations are permitted that would cause a reduction of the RCS boron concentration. This minimizes the probability of an inadvertent boron dilution event. Boron stratification due to temperature gradients will not develop to any significant extent during the time when no loop of SDC is in operation. The use of adequately borated water for injection into the RCS during the test provides assurance that the test itself cannot lead to a boron dilution event. When the SDC system is operating, the minimum SDC flow rate of 2200 gpm imposed by Surveillance Requirements SR 3.9.4.1 and SR 3.9.5.2 is sufficient to ensure complete mixing of the boron within the RCS.

The capability to close the containment penetrations with direct access to the outside atmosphere within the calculated time to boil is maintained. During outages the Operations Department has updated information based on current calculations which show the time to boil. Provisions are maintained in place to ensure containment closure can be established within the calculated time frame. With the reactor cavity flooded to any level above the reactor vessel flange, Edison has demonstrated that containment closure can be achieved within 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br />, even in the event of a loss of offsite power. It will take approximately 6 days to reach the point in the outage where the reactor head is removed and the cavity is filled with water. The time to boil with initial conditions of 6 days following shutdown and 20 feet of water above the reactor vessel flange is approximately 3.5 hours5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br />. The time to uncover the core with these same initial conditions is approximately 77.5 hours5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br />.

The reactor cavity water level is maintained greater than or equal to 20 feet above the reactor vessel flange. This level ensures an adequate heat sink and allows room to perform the LPSI pump suction header check valve test, which will increase this water level.

t l

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1 Pronosed Chanaes: Items 3 and 4 Based on Calculation N-0220-029, with the reactor cavity water level at 12 feet above the flange, at 6 days after shutdown it takes approximately 2.3 hours3.472222e-5 days <br />8.333333e-4 hours <br />4.960317e-6 weeks <br />1.1415e-6 months <br /> to boil and 48 hours5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br /> to uncover the core, the top of the active '

fuel. With the reactor cavity flooded to any level above the reactor vessel flange, Edison has demonstrated that containment closure can be achieved

. within 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br />, even in the absence of offsite power. This will provide a j l minimum of a 1.3-hour margin. Therefore, a restriction of 6 days after '

l shutdown is added to the TS.

1 Using the LPSI pump as the standby pump, cold RWST injection water can fill the reactor cavity at a flow rate of approximately 5000 gpm, over twice the

required SDC flow of 2200 gpm. It will take approximately 30 minutes to align l a LPSI pump to fill the cavity and approximately 25 minutes to raise the reactor cavity level from 12 feet above the reactor vessel flange to 20 feet above the reactor vessel flange, for a total time of approximately 55 minutes.

The allowance to operate with only one loop of SDC OPERABLE and operating with the reactor cavity water level less than 20 feet above the reactor vessel l flange but greater than or equal to 12 feet above the reactor vessel flange l will provide for a significant savings in outage time. The provisions added l

by this TS change ensure there is adequate time to take action and provide a method to restore the reactor cavity water level to 20 feet above the reactor l vessel flange, taking the plant to a condition bounded by TS 3.9.4.  !

l Specifically, these provisions will:

l l

l 1. Require the reactor to be shutdown for at least 6 days to ensure that the time to boil is greater than twice the time it would take to establish containment closure, and significantly more time than it would take to commence reactor cavity fill with the required standby equipment. Limiting initiation of this proposed configuration to at least 6 days following reactor shutdown allows the decay heat to be naturally reduced which increases the time to boil. Furthermore, the time to boil and time to uncover the core both increase each subsequent i day following reactor shutdown.

! 2. Limit the water level above the reactor vessel flange to 12 feet or greater, providing enough cooling to allow time for corrective actions.

Although the 12 feet will be our absolute limit, typically, we operate with some margin away from the limits. To perform the outage work supported by this change (i.e., SDC, CCW, and SWC loop outages running concurrent with reactor internals disassembly and reassembly) we need a water levei less than 12'9" above the reactor vessel flange. Typically, we will maintain a level closer to the 12'9" than the 12' above the flange. The reactor pressure vessel flange is approximately 11' above

! the top of the fuel. Therefore, the water level will be a minimum of 23' above the fuel, which still maintains a large volume of water to provide a heat sink.

l i

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3. Require one loop of SWC and CCW operable, and the CCW swing pump

maintained operable to reduce the probability of CCW failure.

4. Require one loop of Shutdown Cooling to operate using the containment spray pump. Also, require the LPSI pump to be the main standby pump ready to fill the cavity to at least 20 feet above the reactor vessel

! flange. In the event that CCW is lost, cooling flow to all ECCS pumps '

l is also lost. The LPSI pump can start cold and raise the reactor cavity I water level from 12 feet above the reactor vessel flange to 20 feet '

above the reactor vessel flange within the manufacturer's recommended operating times without CCW flow. The high pressure safety injection

, pump will also be maintained as a standby pump ready to increase the water level if needed. In support of this contingency the RWST will be required to contain the volume of water required to raise the level to 20 feet above the reactor vessel flange.

5. Require the water temperature of the SDC system to be maintained less than 120*F. This is the temperature the time to boil curves are based on. However, the normal operating temperature during this condition l will typically be less than 100*F. '

6. Provided that only one loop of the shutdown cooling system is operable I with less than 20 feet of water above the reactor vessel flange and any of the required conditions are not met, action will be taken to i l

immediately establish greater than or equal to 20 feet of water above I the reactor vessel flange. By taking action to restore the level to i 20 feet above the reactor vessel flange the plant will be placed in l TS 3.9.4, which only requires one loop of SDC to be operable.

Additionally, the core will not heat up while the reactor cavity water l level is being raised with cool water from the RWST. This will provide I additional time to either restore the one loop of SDC or take other  ;

actions to provide core cooling as required by TS 3.9.4.

Prooosed Chance Item 5: j This change adds wording to the notes in LCOs 3.9.4 and 3.9.5 that was i unintentionally deleted by the Unit 2 Amendment No.127 and Unit 3 Amendment No. 116 approved Technical Specifications. When the Unit 2 Amendment No. 127 and Unit 3 Amendment No.116 TSs are implemented (scheduled for July of 1996),  !

the following note will read: '

, "A containment spray pump may be used in place of a low pressure safety l injection pump to provide shutdown cooling flow."

f PCN 458 restores the phrase "in either or both shutdown cooling loops," which i was inadvertently omitted by Unit 2 Amendment No. 127 and Unit 3 Amendment

No. 116. Therefore, this is an editorial change.

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- - _ _ - - .-- - - - - - . - - ~ . - -- - . - .- - . _. - ~ _ . _ _ - - .

D Proposed Chanae Item 6:

l I This change conservatively restricts the completion time to ensure containment l closure is achieved prior to the water in the cavity boiling, in the event of l

a Loss of Shutdown Cooling. This restriction is already a self imposed requirement at San Onofre Units 2 and 3. Incorporating it in the Technical i Specification only serves to highlight the importance of this requirement. pd 1

l This change recognizes the importance to ensure the containment is closed l

prior to the water in the reactor cavity boiling in the event of a Loss of Shutdown Cooling. This change recognizes that the time to boil may be less l than 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br />.

No Significant Hazards Consideration:  :

The Commission has provided standards for determining whether a significant hazards consideration exists as stated in 10 CFR 50.92. A proposed amendment to an operating license for facility involves no significant hazards consideration if operation of the facility in accordance with a proposed amendment would not: (1) involve a significant increase in the probability or consequences of an accident previously evaluated; or (2) create the possibility of a new or different kind of accident from any accident i previously evaluated; or (3) involve a significant reduction in a margin of I safety. A discussion of these standards as they relate to this amendment request follows to show that operation of the facility in accordance with this l

proposed Amendment does not: '

1. Involve a significant increase in the probability or consequences of an accident previously evaluated?

ReSDonSe: No Limiting Conditions for Operation (LCO) in Technical Specifications (TSs) 3.9.4 and 3.9.5 define the operability requirements for the Shutdown Cooling (SDC) system during refueling operations (Mode 6) while the water level above the top of the reactor vessel flange is at least 23 feet and less than 23 feet, respectively. The objective of these TSs is to ensure that 1) sufficient cooling is available to I remove decay heat, 2) the water in the reactor vessel is maintained below 140 F, and 3) sufficient coolant circulation is maintained in the reactor core S minimize boron stratification leading to a boron dilution incident.

The proposed TS changes affect the current limits imposed while ensuring adherence to the bases of the TS. No plant modifications are being made. The reactor cavity water level limitations and SDC system required operating times are being changed based on plant specific calculations and the objectives of the TSs are being l maintained.

i l

1) Reduce the water level where two locos of SDC are reauired from 23 feet to 20 feet above the reactor vessel flanae.

- = = - .- -_---- - _ . . - . - - - . . - . - . - . ~

Prior to the approval of Unit 2 Amendment No.127 and Unit 3 Amendment No. 116, Technical Specification Bases Section 3/4.9.8 has ,

stated that "With the reactor vessel head removed and 23 feet of water above the reactor vessel flange, a large heat sink is available for core cooling, thus in the event of a failure of the operating shutdown cooling loop, adequate time is provided to initiate emergency procedures to cool the core."

In the Bases for the New Standard Technical Specifications, "NUREG 1432, Revision 0, dated September 30, 1992, Section B 3.9.4 l it is stated that; "The 23 ft level was selected because it corresponds to the 23 ft requirement established for fuel movement in LC0 3.9.6, " Refueling Water Level."

Southern California Edison (Edison) calculations show that there is an insignificant difference in the time to boil due to the 3-foot change ir. required water level. Therefore, adequate water is still available to mitigate the consequences of losing SDC.

2) Increase the time a reauired 1000 of the SDC system may be removed from service from un to 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> oer 8-hour neriod to un to 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br /> ner 8-hour oeriod. orovided the uocer auide l structure has been removed from the reactor vessel.

l The proposed TS changes the time the SDC loop may be removed from operation from up to 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> per 8-hour period to up to 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br /> per i 8-hour period, and allows removal of the SDC loop from operation for j testing of the Low Pressure Safety Injection (LPSI) system components as well as for core alterations in the vicinity of the hot legs. The proposed TS change also imposes certain restrictions to ensure operating the SDC system in accordance with this proposed  ;

TS change is of no safety significance. These restrictions are ,

discussed separately below. I Specifically stating that the upper guide structure will be removed j assures that natural heat transfer is not impeded.

l l

When securing the only operating loop of the SDC system the maximum Reactor Coolant System (RCS) temperature is maintained s 140 F.

The initial conditions and heatup rate are selected such that the 4 RCS temperature remains s 140"F during the test. Therefore, there is ample margin to boiling. Typical initial temperatures are less than 100"F.

The water being injected by the LPSI system test is cool water from the Refueling Water Storage Tank (RWST) and will increase the

reactor cavity water level by several inches, providing more cool water to the heat sink. The two hours is sufficient time to align the system to test, perform the test, and restore the loop of SDC to operation prior to exceeding 140*F.

4 i

1 No operations are permitted that would cause a reduction of the RCS boron concentration. This minimizes the probability of an  ;

inadvertent boron dilution event. The use of adequately borated j water for injection into the RCS during the test provides assurance that the test itself cannot lead to a boron dilution event. When the SDC system is operating, the minimum SDC flow rate of 2200 gpm )

imposed by Surveillance Requirements SR 3.9.4.1 and SR 3.9.5.1 is '

sufficient to ensure complete mixing of the boron within the RCS.  ;

l Securing SDC flow is only allowed when the reactor cavity water level is maintained greater than or equal to 20 feet above the reactor vessel flange. This level ensures an adequate heat sink to J perform the LPSI pump suction header check valve test.

3) Allow for runnina 1 1000 of shutdown coolina with additional l reauirements when the water level is less than 20 feet but areater than or eaual to 12 feet above the reactor vessel flanae.

4) Add an action to be taken when ooeratina 1 1000 of SDC with less than 20 feet of water above the reactor vessel flance when the soecified reauirements are not met. ,

In the event of a loss of SDC the time to boil is reduced from approximately 4.0 hours0 days <br />0 hours <br />0 weeks <br />0 months <br /> when the water level is 23 feet above the reactor vessel flange to approximately 2.3 hours3.472222e-5 days <br />8.333333e-4 hours <br />4.960317e-6 weeks <br />1.1415e-6 months <br /> at 12 feet, assuming the reactor has only been shutdown for 6 days. However,  ;

this is ample time to close containment (less than 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br />) and to '

, restore SDC or initiate alternative cooling (e.g., add water to the  ;

cavity (approximately 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br />)). The reactor pressure vessel flange is approximately 11' above the top of the fuel. Therefore, the )

water level will be a minimum of 23' above the fuel, which still maintains a large volume of water to provide a heat sink.

l Requiring the reactor to be shutdown for at least 6 days to have l only one loop of SDC operable when the reactor cavity level is between 20 feet and 12 feet above the reactor vessel flange ensures that the time to boil is greater than twice the time it would take to establish containment closure and to commence reactor cavity fill with the required standby equipment.

One loop of SDC operating with a containment spray pump allows for the high capacity LPSI pump to be the main standby pump capable of i filling the reactor cavity to at least 20 feet above the reactor l pressure vessel flange in the event SDC is lost. The high pressure safety injection pump will also be maintained OPERABLE to increase the water level if needed. In support of this contingency the RWST will be required to contain the volume of water needed to raised the l 1evel to 20 feet above the reactor pressure vessel flange. As discussed above, the reactor cavity can be filled at a rate of approximately 4.0 inches per minute with the LPSI pump.

j 1

If operating one loop of the SDC system with less than 20 feet of water above the reactor vessel flange and any of the required conditions are not met, requiring immediate action to establish greater than or equal to 20 feet of water above the reactor vessel flange ensures no time is wasted trying to restore the required condition not met. By taking action to restore the level to 20 feet above the reactor vessel flange the plant will be placed in TS 3.9.4, which only requires one loop of SDC to be operable.

Additionally, the core will not heat up while the water level in the reactor cavity is being raised with cool water from the RWST. This will provide additional time to either restore the one loop of SDC or take other actions to provide core cooling as required by TS 3.9.4.

A Probabilistic Risk Assessment (PRA), with a) one loop of the SDC system operable with the reactor cavity water level greater than or equal to 12 feet above the reactor vessel flange, and b) one loop of the SDC system operable with the reactor cavity water level greater than or equal to 20 feet above the reactor vessel flange, showed that the operations in accordance with the proposed TS would not significantly increase the probabilities of inventory boiling and core damage.

5) Item 6 adds wordina to the notes in LCOs 3.9.4 and 3.9.5 that was unintentionally deleted by the Unit 2 Amendment No. 127 and Unit 3 Amendment No. 116.

This is an editorial change.

6) Item 6 conservatively restricts the completion time to ensure

, containment closure is achieved orior to the water in the cavity boilina. in the event of a loss of Shutdown Coolina.

This restriction is already a self imoosed reauirement at Sul Onofre Units 2 and 3. In'cdrporatina it in the Technical Specification only serves to hiahliaht the imoortance of this reauirement.

This change captures all periods of time when the time to boil following a Loss of Shutdown Cooling is less than 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br />. Having this requirement cannot initiate an accident. However, this requirement reduces the consequences of a Loss of Shutdown Cooling Accident when the time to boil is less than 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br />.

Therefore, proposed changes 1 through 6 do not involve a significant increase in the probability or consequences of an accident.

2. Create the possibility of a new or different kind of accident from any accident previously evaluated?

Response: No

1) Reduce the water level where two locos of SDC are reauired from 23 feet to 20 feet above the reactor vessel flanae.

2) Increase the time a reauired 1000 of the SDC system may be removed from service from un to 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> oer 8-hour oeriod to uo to 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br /> oer 8-hour oeriod. orovided the uooer auide structure has been removed from the reactor vessel.

3) Allow for runnina 1 1000 of shutdown coolina with additional reauirements when the water level is less than 20 feet but areater than or eaual to 12 feet above the reactor vessel flanae.

l 4) Add an action to be taken when ooeratina 1 1000 of SDC with less than 20 feet of water above the reactor vessel flanae when the specified reauirements are not met.

l l The Limiting Conditions for Operation (LC0) in Technical Specifications (TSs) 3.9.4 and 3.9.5 define the operability requirements for the SDC system during refueling operations (Mode 6) while the water level above the top of the reactor vessel flange is at least 23 feet and less than 23 feet, respectively. The objective of the proposed TS changes is to ensure that the intent of the Bases ,

l is maintained. [i.e.,1) sufficient cooling is available to remove  !

decay heat, 2) water in the reactor vessel is maintained below i 140*F, and 3) sufficient coolant circulation is maintained in the reactor,, core to min.im.ize boron stratification leading to a boren i i

~dilutionincident.]

The proposed TS changes affect the current limits imposed while ensuring adherence to the bases of the TS, No plant modifications are being made. The reactor cavity water level limitations and SDC system required operating times are being changed based on plant specific calculations, and the objective of the TSs are being maintained. The added requirements and action statement facilitate safe operation.

i 5) Item 5 adds wordina to the notes in LCOs 3.9.4 and 3.9.5 that l was unintentionally deleted by the Unit 2 Amendment No.127 and

Unit 3 Amendment No. 116.

4 5

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l 0

This is an editorial change.

6) Item 6 conservativelv restricts the comoletion time to ensure containment closure is achieved orior to the water in the cavity boilina. in the event of a loss of Shutdown Coolina.

This restriction is already a self imoosed reauirement at San Onofre Units 2 and 3. Incorocratina it in the Technical Soecification only serves to hiahlicht the imoortance of this

~

reauirement. l i

l This restriction cannot initiate an accident.

Therefore, the operation of the facility in accordance with proposed changes 1 through 6 does not create the possibility of a new or different kind of accident from any accident previously evaluated.

3. Involve a significant reduction in a margin of safety? l Resoonse: No Limiting Conditions for Operation (LCO) in TSs 3.9.4 and 3.9.5 define the operability requirements for the SDC system during refueling operations (Mode 6) while the water level above the top of the reactor vessel flange is at least 23 feet and less than 23 feet, i respectively. The objectives of these TSs are to ensure that 1) sufficient cooling is available to remove decay heat, 2) the water I in the reactor vessel is maintained below 140 F, and 3) sufficient coolant circulation is maintained in the reactor core to minimize boron stratification leading to a boron dilution incident.

1) Reduce the water level where two looos of SDC are reauired from "

l 23 feet to 20 feet above the reactor vessel flanae. l l

Prior to the approval of Unit 2 Amendment No. 127 and Unit 3 Amendment No. 116, Technical Specification Bases Section 3/4.9.8 has stated that "With the reactor vessel head removed and 23 feet of

. water above the reactor vessel flange, a large heat sink is l available for core cooling, thus in the event of a failure of the l operating shutdown cooling loop, adequate time is provided to initiate emergency procedures to cool the core."

l In the Bases for the New Standard Technical Specifications, l l NUREG 1432, Revision 0, dated September 30, 1992, Section B 3.9.4 it

! is stated that "The 23 ft level was selected because it corresponds ,

to the 23 f t requirement established for fuel movement in LCO 3.9.6,

" Refueling Water Level."

. I 1

i Edison calculations show that there is a minimal difference in the time to boil due to the 3-foot change in required water level.

, Therefore, the margin of safety has not been significantly reduced.

l 2) Increase the time a reauired 1000 of the SDC system may be

{

1 removed from service from uo to 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> oer 8-hour oeriod to un i j to 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br /> Der 8-hour oeriod. orovided the uoner auide j structure has been removed from the reactor vessel.

The proposed TS changes the time the SDC loop may be removed from ,

operation from up to 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> per 8-hour period to up to 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br /> per '

8-hour period, and allows removal of the SDC loop from operation for testing of the LPSI system components as well as for core alterations in the vicinity of the hot legs. The proposed TS change l also imposes certain restrictions to ensure operating the SDC system )

in accordance with this proposed TS change is of no safety  !

significance. These restrictions are discussed separately below.

Specifically stating that the upper guide structure will be removed assures that natural heat transfer is not impeded.

When securing the only operating loop of the SDC system, the maximum i RCS temperature is maintained s 140*F. The initial conditions and heatup rate are selected such that RCS temperature remains s 140*F during the test. Therefore, there is ample margin to boiling.

Typical initial temperatures are less than 100*F.

The water being injected by the LPSI system test is cool borated water from the RWST and will increase the level of the reactor .

cavity by several inches. The two hours is sufficient time to align the system to test, perform the test, and restore the loop of SDC to operation prior to exceeding 140*F. ,.

1 No operations are permitted that would cause a reduction of the RCS boron concentration. This minimizes the probability of an inadvertent boron dilution event. The use of adequately borated water for injection into the RCS during the test provides assurance that the test itself cannot lead to a boron dilution event. When the SDC system is operating, the minimum SDC flow rate of 2200 gpm is sufficient to ensure complete mixing of the boron within the RCS.

Securing SDC flow is only allowed when the reactor cavity water level is maintained greater than or equal to 20 feet above the reactor vessel flange. This level ensures an adequate heat sink to  ;

perform the LPSI pump suction header check valve test. l The added requirements and the nature of the test provide assurances that the water temperature will be maintained less than 140*F and that boron stratification is prevented.

3) Allow for runnina 1 1000 of shutdown coolina with additional reauirements when the water level is less +han 20 feet but areater than or eaual to 12 feet above the reactor vessel flance.

4) Add an action to be taken when operatina 1 1000 of SDC with less than 20 feet of water above the reactor vessel flange when 1hfL50ecified reauirements are not met.

In the e s t of a loss of SDC, the time to boil is reduced from approximately 4.0 hours0 days <br />0 hours <br />0 weeks <br />0 months <br /> when the water level is 23 feet above the reactor vessel flange to approximately 2.3 hours3.472222e-5 days <br />8.333333e-4 hours <br />4.960317e-6 weeks <br />1.1415e-6 months <br /> at 12 feet, when the reactor has only been shutdown for 6 days. However, this is ample time to close containment (less than 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br />), and to restore SDC or initiate alternative cooling (e.g., add water to the cavity (approximately 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br />)).

Requiring the reactor to be shutdown for at least 6 days to have only one loop of SDC operable when the reactor cavity ievel is between 20 feet and 12 feet above the reactor vessel flange ensures that the time to boil is greater than twice the time it would take us to establish containment closure and to commence reactor cavity fill with the required standby equipment.

One loop of SDC operating with a containment spray pump allows for the high capacity LPSI pump to be the main standby pump capable of filling the reactor cavity to at least 20 feet above the reactor pressure vessel flange in the event SDC is lost. The high pressure safety injection pump will also be maintained OPERABLE to increase the water level if needed. In support of this contingency the RWST will be required to contain the volume of water needed to raised the levei to 20 feet above the reactor pressure vessel flange. As discussed above, the reactor cavity can be filled at a rate of approximately 4.0 inches per minute with the LPSI pump.

If operating one loop of the SDC system with less than 20 feet of water above the reactor vessel flange and any of the required conditions are not met, requiring immediate action to establish greater than or equal to 20 feet of water above the reactor vessel flange ensures no time is wasted trying to restore the required condition not met. By taking action to restore the level to 20 feet above the reactor vessel flange the plant will be placed in TS 3.9.4, which only requires one loop of SDC to be operable.

Additionally, the core will not heat up while the reactor cavity water level is being raised with cool water from the RWST. This will provide additional time to either restore the one loop of SDC or take other actions to provide core cooling as required by TS 3.9.4.

t i A PRA showed that operations in accordance with the proposed TS did not significantly increase the probabilities of inventory boiling and core damage.

5) Item 5 adds wordina to the notes in LCOs 3.9.4 and 3.9.5 that yas unintentionally deleted by the Unit 2 Amendment No.127 and l Unit 3 Amendment No. 116.

This is an editorial change.

6) Item 6 conservativelv restricts the comoletion time to ensure conta1nment closure is achieved orior to the water in the cavity boilina. in the event of a Loss of Shutdown Coolina.

This restriction is already a self imoosed reauirement at San Onofre Units 2 and 3. Incorocratina it in the Technical i Soecification only serves to hiahliaht the imoortance of this reauirement.

This change increases the margin of safety provided by the Technical Specification by specifying that the containment must be closed within 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> or within the calculated time to boil, whichever is Af(

less. This change revi.ses the Technical Specification to specifically recognize the iniportance of ensuring containment closure is achieved prior to Doiling in the reactor vessel, upon a j loss of shutdown cooling.

Therefore, operation of the facility in accordance with proposed changes 1 through 6 do not involve a significant reduction in a margin of safety.

l l Based on the responses to these three criterion, Southern California Edison l (SCE) has concluded that the proposed amendment involves no significant hazards consideration.

Environmental Consideration:

SCE has determined that the proposed amendment involves no changes in the ,

i amount or type of effluent that may be released offsite, and results in no

! increase in individual or cumulative occupational radiation exposure. As l l described above, the proposed TS amendment involves no significant hazards consideration and, as such, meets the eligibility criteria for categorical exclusion set forth in 10 CFR 51.22(c)(9).

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