ML20086T307

Describes Programs for Completing Individual Plant Exam of External Events for Severe Accident Vulnerabilities,Per Suppl 4 to Generic Ltr 88-20

ML20086T307
Person / Time
Site:	Beaver Valley
Issue date:	12/20/1991
From:	Sieber J DUQUESNE LIGHT CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
GL-88-20, NUDOCS 9201060216
Download: ML20086T307 (7)

Text

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Nuclear Regulatory Commission Attnt Document Control Desk Washington, DC 20555 Subject Beavor Valley Power Station, Unit No. 1 and No. 2 BV-1 Docket No. 50-334, License No. DPR-66 BV-2 Docket No. 50-412, License No. NPF-73 Conoric Letter 88-20, Supplement 4 Referenco 1. Duquesno Light Company Lotter to the NRC providing the 60-day Response to Genoric Lotter 88-20, dated October 30, 1989

2. Individual Plant Examination of Exto: sal Events (IPEEE) For Sovoro Accident Vulnerabilities - 10CFR50.54(f)(Gonoric Lottor No. 88-20,Supplomont 4)

This lotter is in response to Reference 2

requesting the proposed programs for completing the Individual Plant Examination of External Events (IPEEE) for Severo Accident Vulnerabilities.

Duquesno Light Company (DLC) will perform the IPEEE for BVPS-1 and 2

by extending each Unit's Loval 2

Probabilistic Risk Assessment (PRA) that was described in Reference 1 to include full scopo coverago of external events.

The PRAs will moot or exceed the requestad actions for the IPEs and the IPEEEs.

The PRAs are being performed by a

team of DLC Engincors acquiring expertise and experienco in PRA technology supported by a team of contractors led by PLG Inc.

(formerly Pickard, Lowe, and

Garrick, Inc.).

Contractor personnel are supporting the effort by providing

methods, software, special areas of exportiso and resources nooded to supplement the DLC PRA team.

As with the IPE Frogram described in Reference 1,

DLC personnel will actively participato in all phases of the work.

The transfer of PRA technology from our contractors to DLC, which has occurred in the IPE, will continue through the IPEEE.

The overall objectives of the PRA program are tot

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l 5eavor Valley Power Station, Unit No. 1 (DVPS-1) and No. 2 (DVPS-2)

DVPS-1 Docket No. 50-334, License No. DPR-66 BVPS-2 Docket No. 50-412, Liconne No. NPF-73 Generic Letter 88-20, Supplomont 4 Page 2 Develop

separato, plant-specific PRA's for Units 1 and-2 with adequate coverago of external events to support a comprehensive risk and accident management program.

Apply and develop generic and plant-specific PRA databases for initiating event frequencies, component failure rates, maintenanco unavailability, common cause failure parameters, and human error rates.

Develop point estimato and uncertainty distribution results for core damago events. and a full spectrum of radioactive release categorieb for Units 1 and 2.

Determine the underlying risk controlling

factors, importance

measures, and key sources of uncertainty in developing the risk estimates.

Provide technology transfer to DLC (including methods,-

software, and training) in the use of PRA methods, severo accident

behavior, and application of associated computer softwara.

Moot the NRC ' requirements as set forth in Generic Letter 88-20, HUREG-1335, NUREG-1407 and supporting documents.

The methodology that will be followed in the IPEEE is a

straightforward application of modern PRA technology developed by PLG for external events and builds directly on the PRA models already developed and analyzed for intnrnal initiating events and floods.

The event troo/ fault tree models that are developed and used in the PRA provide for an integrated treatment of accident sequences caused by the combination of internal and external causes actions. plant of initiating

events, system responses, and operator This integrated treatment is graphically depicted in Figure 1.

A discussi9n of the treatment of unch class of events is briefly presented below.

Soismic Events i

The treatment of seismic events will meet or exceed the criteria for acceptable methods sat forth in NUREG-1407 and will make use of recent experience in the performance and reviews of seismic PRAs on other plants such as Diablo

Canyon, South Texas

Project, and Seabrook.

Accident sequences will be modeled with a special seismic event tree that represents all the seismic damage states for structures and equipment.

Several trees are used to cover different

-initiator types (e.g.

trar.sient or LOCA) and different discreto levels of seismic intensity.

These seismic event trees are linked to the plant systems event trees to provide for an integrated treatment of sequences resultd.ng from both seismic and non-seismic causes.

i 1

Boavor Valley Power Station, Unit No. 1 (BVPS-1) and No. 2 (BVPS-2)

BVPS-1 Docket No. 50-334, License No. DPR-66 BVPS-2 Docket No. 50-412, License No. 14PF-73 Generic Letter 88-20, Supplement 4 Page 3 Wo plan to incorporato both Electric Power Rosearch Institute (EPRI) and Lawrence Livormore National Laboratorios (LLNL) based soismic hazard methods as requested.

PRA importance monsures will be used to focus msources applied to structural fragility evaluation.

s:*lification will include a

full treatment of uncertainties and will produco high confidence of a low probability of failure (HCLPF) values as a byproduct.

The treatment of relay chatter and soil liquotaction will be structured so as to meet the associated requirements.

Walkdowns will incorporate insights from the EPRI Report

NP6041, Methodology for Assessment of Nuc1 car Power Plant Seismic Margin, Generic Letter 88-20, Supplement 4,

encourages coordination of the soismic IPEEE with-Unronolved Safety Issuo A-46 "so that the objectivos of both activities may be accomplished with a single walkdown effort."

As stated in NRC SECY-91-102, the procedures for the soismic walkdown portion of this program are "ono of tho most important ingredients in the seismic

IPEEE,

[and) are similar to those that will be used in the implementation of Unresolved Safety Issue (USI) A-46.

DLC agrees with NRC staff that proceduros developed for resolution of A-46 be used as much as possible for the seismic IPEEE, which-would include the necessary training on these procedures.

Because of similarities between the A-46 and sei mic IPEEE

programs, DLC intends to train seismic IPEEE walkdown personnel at training courses currently being developed by the seismic Qualification Utility Group (SQUG).

DLC also intends to conduct seismic IPEEE and A-46 valkdowns at the same time for BVPS-1 which is designated as an A-46 plant.

However, the anticipated Supplemental Safety Evaluation Report (SSER) cn the SQUG's Generic Implementation Procedure (GIP) for resolution of USI A-46 has not been made available in sufficient time to permit finalization of a

coordinated plan and schedule for the soismic portion o_ the IPEEE in this responso.

Therefore, DLC is not able to submit a firm schedule to complete the seismic portion of the IPEEE until after receipt and review of the SSER, and in no caso later than 120 days following receipt of the SSER.

Following this

review, the program for conducting the seismic IPEEE may be modified depending on the content of the SSER and resolution of open issues.

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Beaver Valley Pcuer Station, Unit No. 1 (BVPS-1) and No. 2 (BVPS-2)

DVPS-1 Docket No. 50-334, License No. DPR-66 BVPP ? Docknt No. b0-412, License No. NPP-73 Generic Letter 88-20, Supplement 4 Page 4 Internal Fires The treatment of internal fires will use state-of-the-art techniques of fire PRA and will address issues raised in teh Fire Risk Scoping Studies.

The involvement of PLG, which performed three of the four PRAs reviewed in the Fire Risk Scoping

Study, will help ensure that these

.icsues are adequately addressed.

Insights from NRC's recent review of the South Texas Project PRA will also be incorporated.

The treatment of internal fires begins with a

spatial interactions task that includes a walkdown and a systematic examination of each plant location for a range of hazards and possible effects on plant equipment.

Screening evaluations are performed to identify important locations for a

more detailed analysiv of fires.

The spatial intoraction analysis also providos important information to support the examination of other hazards.

Individual fire scenarios are identified and evaluated for determination of frequency and plant damage impact.

An up-to-date fire event data base developed by PLG is used to support the quantification.

Fire propagation analyses support the determination of damage states.

The fire scenarios are processed through the plant event trees, or with the seismic

events, to effect an integrated treatment.

Seismic induced fires and possible damage from fire suppression activities will also be addressed.

Other External Eventg The treatment of high

winds, floods, transportation and nearby facility hazards will closely follow the approach described in Section 5 of NUREG-1407.

The future IPEEE effort will be carried out in what is best described as a full-scopo Level 2 PRA.

As such, scenarica initiated by external events are examined not only with respect to the potential for core damage, but for impacts on containment structures and systems as well.

Hence, if there are any risk significant plant damage states involving containment failure or bypass that are unique to our external events, these states will be identified.

Walkdowns and analyses which are common to other identified issues will be. coordinated to the maximum extent practical.

The seismic portion of the IPEEE for Unit 1 is currently-scheduled to be performed during the loth refueling outage to allow planning and coordination with USI A-46.

As indicated earlier this schedule is subject to the final NRC approval and issuance of the SSER on the SQUG methodology to address A-46.

Coordination with other issues and the desire to maximize the use of Duquesne Light personnel for a major portion of this work will result in a submittal of the Beaver Valley IPEEE reports after the date requested in Generic Letter 88-20, Supplement 4.

The milestones and schedule for the IPEEE program are as follows:

1

I Boavor Valloy Power Station, Unit No. 1 (BVPS-1) and No. 2 (BVPS-2)

BVPS-1 Docket No. 50-334, License No. DPR-66 BVPS-2 Docket No. 50-412, License No. NPF-73 Generic Letter 88-20, Supplement 4 Page 5 During 1992 - develop a detailed project plan for conducting the IPEEE for Beaver Valley Units 1 and 2 will be developed.

Durin(

the

.ch refueling outage at Unit 2 (projected to begin September, 1993) perform the required seismic and fire walkdowns (pending issuance of the SSER and appropriate walkdown training).

complete the seismic, fire and other By

February, 1995 external event analyses for Unit 2.

By September 1995 - integrate the Unit 2 analyses into the current int ne? events IPE.

During the loth refueling outage at Unit 1 (projected to begin in

October, 1994) perform the seismic and fire walkdowns (pending issuance of the SSER and appropriate walkdown training).

By

January, 1996 complete the seismic, fire and other external events analyses for Unit 1.

By

July, 1996 integrate the Unit 1 analyses into the current internal events IPE.

By

January, 1996 submit the IPEEE report for BVPS-2 for NRC review.

By July,-

1997

- submit the IPEEE repoNt for BVPS-1 for NRC review.

Shoulu you-have any questions regarding this submit *al, please contact Ed Coholich at (412) 393-5224.

Sincerely, w-D. Siebei.

ice President Nuclear Group cc:

-Mr. J.

Beall, Sr. Resident Inspector

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Mr. T. T. Martin, NRC Region-I Administrator Mr. A. W. DeAgazio, Project Manager Mr. M. L. Bowling (VEPCO)

1 Figure 1 1

Internal

• Events impact on Plant Equipment Inte d Floods 1

All Possible Accident Containment SIstem and Sequences Responses O~perator witri Core and i

Internal Responses Damage

- Releases i

Fires 1

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i Seismic Im act on i

PI nt l

Events Equipmerit I

i Other

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Events IPEEE s........................................

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SS COUllTY OF BEAVER

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, 1991, on this I Olb

[d N N2[., a 11otary Public in and for said beforu me, commonwoalth' and-County, personally appeared J.

D. Slober, who being duly sworn, deposed, and said that (1) he is Vice President - 11uclear of Duquesne Light, (2) he is 6uly authorized to execute and file the foregoing Submittal c.n. behal f of u.31d Company, and (3) the statements set forth in the Submittal are true and correct to the best of his knowledge, information and be1let.

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