ML20063D320

Amend Applications 138 & 122 to Licenses NPF-10 & NPF-15, Respectively,Consisting of Proposed Change Number 433 to Revise UFSAR to Allow Use of NUREG-0800 SRP Guidance in Evaluating Need for tornado-generated Missile Barriers

ML20063D320
Person / Time
Site:	San Onofre
Issue date:	02/01/1994
From:	Rosenblum R SOUTHERN CALIFORNIA EDISON CO.
To:
Shared Package
ML20063D290	List: ML20063D287 ML20063D320 ML20063D330
References
RTR-NUREG-0800, RTR-NUREG-800 NUDOCS 9402080098
Download: ML20063D320 (8)

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i UNITED STATES OF AMERICA NUCLEAR REGULATORY COMMISSION  :

Application of SOUTHERN CALIFORNIA ) Docket No. 50-361 EDISON COMPANY, et al . for a Class )

103 License to Acquire, Possess, and ) Amendment Use a Utilization Facility as Part of ) Application No. 138 Unit No. 2 of the San Onofre Nuclear )

Generating Station. )

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SOUTHERN CALIFORNIA EDISON COMPANY, et al. pursuant to 10CFR50.90, hereby submit ,

Amendment Application No. 138. This amendment application consists of Proposed Change No. NPF-10-433 to Facility Operating License No. NPF-10. ?roposed Change L

No. NPF-10-433 is a request to revise the Updated Final Safety Analysis Report (UFSAR) to allow the use of probabilistic risk assessment in evaluating the need for tornado-generated missile protection barriers.

Subscribed on the /" day of kBMAf ,199 .

Respectfully submitted, i SOUTHERN CALIFORNIA EDISON Ci.?ANY By: / '

er #W Richard M. Rosenblum Vice President ,

state of California County on c2 lofOrange ll9'l before me, Bussen A. ficeAcrM/$s*o'na/qgt./c 11y appearedM'kpo M. ROJEva t.4M , 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 pers,on, or the  ;

entity upon behelf of which the person acted, executed the instrument.

WITNESS my hand and official seal.

OFFICIAL SEAL j

Notory PWIc-Confornio 9 BARIARA A.ORANGE COUNN Signature M b W O - March 1 i

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94020B0098 940201 i PDR. ADOCK 05000361  ?  !

P PDR y

e UNITED STATES OF AMERICA NUCLEAR REGULATORY COMMISSION Application of SOUTHERN CALIFORNIA ) Docket No. 50-362 -

EDIS0N COMPANY, et al. for a Class )

103 License to Acquire, Possess, and Amendment Use a Utilization Facility as Part of Application No. 122 Unit No. 3 of the San Onofre Nuclear Generating Station.

SOUTHERN CALIFORNIA EDISON COMPANY, et al. pursuant to 10CFR50.90, hereby submit Amendment Application No. 122. This amendment application consists of Proposed j Change No. NPF-15-433 to Facility Operating License No. NPF-15. Proposed Change No. NPF-15-433 is a request to revise the Updated Final Safety Analysis Report (UFSAR) to allow the use of probabilistic risk assessment in evaluating the need +

for tornado-generated missile protection barriers.

Subscribed on the day of FE6MV,19 .

Respectfully submitted, ,

SOUTHERN CALIFORNIA EDISON COMPANY h

By: m) Le I Ri~ chard M. Ros'enblum ..

Vice President State of California . '

Countyof07ange On A/// 9Y before me,JMdMA A. MMUgpfty /ugu G

/ , personally  !

appeared %huMO M. 05&#L4M 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 j entity upon behalf of which the person acted, executed the instrument.

WITNESS my hand and official seal. _______ _

OFFCML SEAL "

Notory Amic CoWordo l Signature h d. p U @ BARIMRA A My ComMedon Eg*es MWeh 31,1996

4 DESCRIPTION AND SAFETY ANALYSIS PROPOSED LICENSE AMENDMENT TO USE NUREG-0800, " STANDARD REVIEW PLAN,"

METHODOLOGY TO EVALUATE THE NEED FOR TORNADO-GENERATED MISSILE HAZARDS 1 SAN ONOFRE NUCLEAR GENERATING STATION, UNITS 2 AND 3 This is a request to change the licensing basis of San Onofre Nuclear Generating Station (SONGS) Units 2 and 3 to allow the use of probabilistic risk assessment techniques, consistent with NUREG-0800, " Standard Review Plan" (SRP), to evaluate the need for tornado-generated missile barriers.

DESCRIPTION OF CHANGES:

The Updated Final Safety Analysis Report (UFSAR) will be changed to allow the use of Probabilistic Risk Assessment (PRA) techniques in evaluating the need for tornado-generated missile barriers. The probability of core damage due to postulated tornado-generated missile strikes of less than 10 4 per year (P 7)-

will be used u a conservative threshold for evaluating the plant configuration. Existing plant conditions, as well as future changes to the facility, may be evaluated through the 10CFR50.59 process as long as the total probability of core damage due to postulated tornado-generated missile strikes is less than 10 4per year. The UFSAR will be updated on'the normal cycle with a listing of affected plant areas and their associated probability of core damage due to postulated tornado-generated missile strikes.

BACKGROUND:

The original SONGS 2&3 licensing basis assumed a tornado-generated missile strike to exposed critical components. Accordingly, barriers to protect certain critical components against these postulated missiles were designed and constructed. By letter dated November 24, 1980, from Mr. K. P. Baskin (SCE) to Mr. F. Miraglia (NRC), Edison committed to protect the SONGS 2&5 Auxiliary feedwater (AFW) system from postulated tornado-generated missiles as listed in UFSAR Table 3.5-6, consistent with the criteria used for tornado-generated missile protection for other plant safe shutdown components. During the resolution of calculation concerns raised during an Edison internal audit of the design of tornado-generated missile protection structures, Edison determined that the missile barriers for portions of the SONGS 2&3 AFW system do not fully satisfy this licensing commitment (Ref.: Voluntary Licensee Event Report 2-93-006, Docket No. 50-361).

A PRA was conducted to determine the risks associated with postulated tornado-generated missile strikes on exposed AFW and Condensate Transfer system piping. The PRA determined that the core damage frequency attributable to tornado-generated missile strikes on the subject piping is less than 10 4 per year (Attachment 1).

The PRA results were eval'uated in light of' Standard Review Plan (SRP) Section 3.5.1.4, Missiles Generated by Natural Phenomena, and SRP Rev.1, Section 3.5.1.5, Site Proximity Missiles (Except Aircraft). Table 1 provides a comparison of the SRP and the proposed licensing basis of SONGS 2&3.

Table 1 i SRP and SONGS 2&3 Proposed Licensing Basis-Acceptance Criteria Comparison SRP Section 3.5.1.4, Rev. O, Tornado-generated missile Missiles Generated by Natural protection is not required if the Phenomena aggregate probability 4of a missile '

strike is less than 10 per year.

SRP Section 3.5.1.4, Rev. 1, Tornado-generated missile Missiles Generated by Natural protection is not required if the Phenomena aggregate probability of a missile strike is less than 10 d per year.

SRP Section 3.5.1.4, Rev. 2, Allows probabilistic approach but Missiles Generated by Natural does not provide an explicit Phenomena acceptance criteria. 7 SRP Section 3.5.1.5, Rev.1, Si+'. Acceptance criteria is met if the Proximity Missiles (Except probability of site proximity Aircraft) missiles impacting the plant and causing radiological consequences greater than 10 CFR Part 100 ~

exposureguidelinesislessthan about 10' per year.

SONGS 2&3 proposed Licensing Basis Tornado-generated missile protection is not required-if the aggregate probability of4 core  ;

damage is less than 10 per year.

r The SRP uses missile strikes and 10 CFR Part 100 exposure guidelines to '

establish acceptance criteria. This FSAR amendment will update the SONGS 2&3 licensing basis to be consistent with these two criteria by using the  :

i probability of core damage to evaluate postulated tornado-generated missile strikes. This methodology is consistent with the work be'ing performed for the Individual Plant Examination of External Events (IPEEE).

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PROPOSED CHANGES TO THE UFSAR: ,

r The following proposed changes are to be made to the SONGS 2&3 UFSAR:

Existing UFSAR ,

l 3.5.3 BARRIER DESIGN PROCEDURES c

Missile-resistant barriers and structures are designed to withstand and ,

absorb missile impact loads without being perforated in order to prevent '

damage to protected components. The procedures employed in design of sistant barriers for local effects are described in Section 2 of '

missile-rpl')

BC-TOP-9A and EPRI RP-399.03) The procedures used to predict the overall ,

response of the barrier and portions thereof to missile impact are described in Sections 3 and 4 of BC-TOP-9A.02)

The barriers provided for protection against tornado-generated missiles are typically the reinforced concrete walls (1-foot 6-inch thick minimum) and '

roof slabs (1-foot 2-inch thick minimum) of the safety-related' structures.

These thicknesses prevent perforation and sustain the impact without concrete spalling on the interior surfaces. In addition, steel grids or framed steel plates (3/4-inch minimum thickness) are provided as covers for safety-related openings. These covers prevent missile perforation and experience structural  !

deflections which are restricted by design so as not to impair the intended  ;

safety function of each opening. One of these covers is the set of front entry doors (AC201) to .the control room lobby. These doors are designed as missile barriers and are normally held in an open position. Uoon initiation of a severe weather warning, the station is notified by the SCE Energy '

Control Center and station personnel will then close these missile doors.  ;

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Proposed Addition to the UFSAR:

Hissile-resistant barriers are not required when the aggregate probability of core damage due to postulated tornado-generated missiles is less than 10 per year. Table 3.5-13 lists the equipment that has been analyzed as meeting this criteria.

Table 3.5-13 Core Damage Risk Assessment for Equipment Locations without 1 Tornado-generated Missile Resistant Barriers Probability of Core Number Description Location Damage per year 4

1. Piping and valves Exposed portions inside <10 associated with the the Refueling Water Units 2 arid 3 Auxiliary Storage Tank (T-005 and i Feed Water pump T-006) enclosures. -l suction, discharge and miniflow, and Exposed portions Condensate Transfer in and around the systems. Condensate Storage Tank  :

T-120 enclosure.  ;

4 TOTAL <10 i

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i SAFETY ANALYSIS:

• The proposed change described above shall be deemed to involve a significant  !

hazards consideration if there is a positive finding in any one of the  !

following areas: ]

Does the proposed amendment:  !

(1) Involve a significant increase in the probability or consequences of an ,

accident previously evaluated?  ;

Response: No.

NUREG-0800, Standard Review Plan (SRP) Section 3.5.1.4 Revision 0 and Section 3.5.1.5 Revision 1 provide a conservatively acceptable  ;

thresholdforsafetyduetodamagecausedbypostulatedmissile  !

strikes. Section 3.5.1.4 Revision 0 uses 10- per year for a  :

tornado-uses 10' generated missile per year for strike,10 exceeding and Section CFR 3.5.1.5 Part 100 Revision 1 limits.

The new criteria of 10 per year for core damage frequency is consistent with this guidance and is negligible when compared to i the overall probability for core damage of about 3x10'6 for the San Onofre Nuclear Generating Station, Units 2 and 3.  !

This change does not involve a significant increase in the ,

probability of an accident previously evaluated because the probability of core damage due to a postulated missile strike is .

so small as to be negligible. The consequences of.an accident remain unchanged since this change only affects the probability of ,

the initiating event and not the consequences.

(2) Create the possibility of a new or different kind of accident from any l accident previously evaluated?  :

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Response: No. 1 This amendment establishes a conservatively acceptable risk I criteria for evaluating postulated tornado-generated missile j damage consistent with the SRP guidance and will not create a new- 1 or different kind of accident from those that have been previously evaluated.

I (3) Involve a significant reduction in the margin of safety. -l Response: No.

This proposed change is consistent with the methodology and acceptance criteria of the SRP. There will be no significant

t reduction in the margin of safety since the acceptance criteria is  !

negligible when compared to the overall core damage frequency of t SONGS 2&3.

SAFETY AND SIGNIFICANT HAZARDS DETERMINATION:

Based on the above Safety Analysis, it is concluded that: 1) the proposed change does noticonstitute a significant hazards consideration as defined by ,

10CFR50.92 and 2) there is reasonable assurance that the health and-safety of the public will not be endangered by the proposed change. Moreover, because. <

this action does not involve a significant hazards consideration, it will also j not result in a condition which significantly alters the impact.of the station .

on the environment as described in the NRC Final Environmental Statement. 1 e

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