BVY-92-111, Submits Info Re Methodology/Plans to Address Suppl 4 to GL 88-20 Re IPE of External Events for Severe Accident Vulnerabilities.Internal Fires & Internal Floods Will Be Analyzed W/Level 1 Pra.Results Will Be Sent by 950630

Submits Info Re Methodology/Plans to Address Suppl 4 to GL 88-20 Re IPE of External Events for Severe Accident Vulnerabilities.Internal Fires & Internal Floods Will Be Analyzed W/Level 1 Pra.Results Will Be Sent by 950630

ML20118B056
Person / Time
Site:	Vermont Yankee
Issue date:	09/18/1992
From:	Pelletier J VERMONT YANKEE NUCLEAR POWER CORP.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
BVY-92-111, GL-88-20, NUDOCS 9209290343
Download: ML20118B056 (6)

Text

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, VisitMONT YANKEE NucLEAlt POWEH CORPORATION

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September 18,1592 BVY 92111 Unlied States Nuclear Regulatory Commission ATTN: Document Control Desk Wnshington, DC 20555

References:

a) License No. DPR 28 (Docket No. 50 271) b) Generic Letter 88 20, Supplement 4, " Individual Plant Examination of External Evonts (IPEEE) for Severa Accident Vulne abilities - 10CFR50.54(f), NVY 9 t 122, June 28,1991 c) NUREG 1407, " Procedural and Submittal Galdsnce for the Individual Plant Examination of External Events (IPEEE) for Severo Accident Vulnerabilitler" d) Letter, VYNPC to USNRC, "Responso to Generic Letter 88-20, Stpplement 4", BVY 91 123, December 19,1991 e) Le;ter, USNRC to VYNPC, " Review of Response to Generic Letter 88-20, Supplement 4", NVY 92-099, June 22,1992 t) Generic Letter 88 20, Supplement 1, " Initiation of the Individual Plant Examination for Severo Accident Vulnerabilities - 10CFR50.54(f), NVY 89180, Augurt 29, 1989 g) Letter, VYNPC to USNRC, " Vermont Yankee Response to Generic Letter 88-20, Seppiement 1 * . BVY 89100, October 24,1989 h) Generic Letter 88 20, " Individual Plant Examination for Severo Accident Vulnerabilities 10CFR50.54(f), NVY 88-259, November 23,1988

Subject:

RESPONSE TO GL 88-20 (SUPPLEMENT 4)

Dear Sir.;

Reference e) requested the.t VYNPC submit an IPEEE plan consistent with Suoplement 4 of the Generic Letter (Reference b), including ti.s project schedule, milestones, and methods. Our response is provided nerein.

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c VERMONT YANKEE NUCLE AR POWER CORPOR ATION United States Nuclear Regulatory Commission September 18,1992 Pago 2 Sch?h.!Q As you know, we are currnntly parforming the IPE for internal events (Reference f). The IFE is scheduled for submittal on December 31,1993 (Reference g). This work

, is currently on schedulo.

L Wt. plan to begin the IPEEE no later than January 1,1994. We plan to submit l the IPEEE on June 30,1995. This in consistent with your request in Referance e)

I"...no later than June 1995"). i l

.Mileston.gg The following tentative milestones are planned for the V / IPEEE:  !

l 01-01 94 BcGin IPEEE j i

! 12 31 94 Cort.plota Screening Analysis for High Winds, Tornadoes, i External Floods, Trantsedation and Nearby Facility )

Accidents j 03-31 95 Compic .a Walkdowns for Seismic IPEEE j i

05 31 95 Complets Internal Firo, ir.ternal F! nod and Setsmle Event ]

- Analyses j i

06-30 95 Submit IPEEE Rnsu!ts ic NRC l

Methods I l High Winds, Tornadocs, Externai Floode, Transportation and Nehrby Facility j

, Accidents will be analyzed usin0 the screenbig approach nutilnod by Figure 1 of - -l L Reference b). j l  :

Internal Fires and Internal Floods win be analyzed with a Lovel 1 PRA. The FIVE methodology will be used as a screan'ng tool to help establish the neope of thct  ;

h Level 1 PRA fire analysis. ,

Seismic events ivill be analyzed using a walkdown-bcend appruch that takes maximum advantage of recognized inaustry expeits. This approacn is suppotied by the following statements from References b), c), and e):

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l ,' vrRMONT YArMEE NUCLE AR POWER CORPORATION United States Nuclear Regulatory Commission September 18,1992 Page 3 "Howcor, the NRC recognizes that other methods capable of identifying plant-specific vulnerabilities to severo accidents due to external ovents may exist."

(Page 3 of Reference b)

"The application of the abovo [NRC approved] qanaches involves considerable judgement with regards to the roquested scope and depth of the study,lovel of analytical sophistication, and lovel of effort to t e expended...The detalled guidelines presented in NUREG 1407 do not prech de use of this type of judgement. Consistent with engineering practice, exper' opinions, simplified _

scoping studies. and bounding analysis (which should be documented), are expected to be used, as appropriate, in forming these judgements." (Page 5 of Reference b)

"The staff recognizes that other methods capable of identifying plant specific vulnerabilities to severo accidents may be acceptable. A licensee may request that the staff review any other systematic examination rnethod to determine if it is acceptable for IPEEE purposes." (Page X of Reference e, " Alternative Methods")

"If you desire to propose a new approach (ie.: an approach not specifically considered in NUREG 1407), you should provide sufficient supporting documentation to allow NRC to determine whether the proposed approach is acceptable." (Page 1 of Reference e)

We are stillin the process of fctmulating the details of the approach to be used g for the seismic analysis. These details will be provided to you as they are developed and finall;'ed, but no later than three months prior to the plant walkdowns. However, in order M satisfy your request for the best informat'on that we can provide at this time, we offer the following outline of the approach:

1. A team of recognized industry experts will participate in the seismic IPEEE, ,

2. The scope of eqeipment to be reviewod will be determined by VY based on input from those experts, using their experience and judgement, with assistance from in-house personnel This will allow resources to be conc 9ntrated on equiplaent found to be most important in enhancing safety.

3. Walkdowns will be performed and documented by the team ul experts along with in-house personnel This will assure that in-house personnel are involved in the examination as encouraged by Reference b).

VENMONT YANH E E Nt)CLE AR POWCH CORPORATION United ~ States Nuclear Regulatory Commission September 18,1992 Pago 4

4. Equipment within the scopo (seo Stop 2) will be reviewed using methods judged acceptable by the team. The proferred methods will be engineering judgement and comparison to existing analysis. Now analysis will only be perfo:med if,in the opinion of the expert team, such analyses are required in order to quantify a perceived vulnerability.

EurtheL i nformation The following information is provided in order to assist NRC in their ovaluation of the proposed schedule and methods.

Reference e) requested that we reassess opportunities for submitting the IPEEE on a more expeditious schedule than we offered in Reference d). We have done such a reassessment and we conclude that tno schoculo can be improved from March 30, 1997 to June 30, 1995. As explained ear ller, the VY IPE will be completed in December 1993. The same personnel used for IPE '.4ill be used for IPEEE in order to take maximum advantage of the in house expertise which has been deve!oped. This is consistent with Reference b) and e) which state:

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...Each licensee is requested to use its staff to maximum sxtent possibla in conducting the 1PEEE...' (Page 3 of Reference b)

"The information you ouained and the expertise you acquired through the IPE [

process should be used to follill part of the IPEEE requirements." (Page 2 of Reference e)

Thus the schedulo proposed herein wm structured to moet the NRC target date  !

whi!e most efficiently utilizing out available resources. The proposed methods have been previously approved tsy NRC (Reference b) except for our seismic IPEEE method.

Wo believe that our proposed seismic IPEEE method is supported by the following facts:

1. The estimated resources of the VV IPEEE effort (including all external events) is al out 6 person years. This !s consistant with the level of effort estimated by NRC in the " Regulatory Basis" Section of Reference bP "The estimated average burden wou'd not exceed 6 person years per licensee response..." (Page 10 of Reference b).

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VERMONT YANKEE NUCLE AR POWER CORPOR ATION United States Nuclear Regulatory Commission Septernbar 18,1992 Pago 5

2. The general nhilosophy of all IPEEE methods is one of "progressivo scroonMg". Dotalled and costly ar,alysis should not have to be perfoimcd when expert engincoring judgement can be telled upon instead. VY's proposed seismic IPEEE method reflects this general philosophy which underlies all methods found acceptablo by NRC.

3. The objectivos of the IPEEE (Pago 2 of Referenco b) are:

1. To develop an appreciation of sovere accident behavior

2. To understand the most likely severo accident sequences that could occur at its plant under full power operating conditions,

3. To gain a qualitativo understanding of the overaillikollhood of core damage and radioactive material release, and

4. If necassary, to reduce the overalllikelihood of core damage and radioactivo material releases by modifying hardware and procedures that would help prevent or mitigato severo accidents.

By pursuing our proposed method (examining potentially vulnerable plant configurations for potential severe accident sequencec), VY will ensure that Objectivos 1 and 2 are mot.

Objectivo 3 for IPEEE notes the need "to gain a gupilliative uniff.ralaft.glir}g

{ emphasis added) of the overall likellhood of core damage and radioactiva matorial release..." This is to be contrasted with the corresponding goal of IPE

'or internal events, "to gain a mole _qvantitative understandina [omphasis added] of the overall probabilities of core damage mod fission product trJoasos..." (Page 1 of Reference h). Wo do not believe that detailed calculations are necessary to achlove a qualitativ_e understanding. Rather, our approach achloves the qualitativo understanding througli use of judgements and comparisons maue by recognized experts, tnereby seeting Objective 3.

To meet Object!ve 4 without incurring excessive costs, VY has proposed a methou that tak.ss advantage of existing industry expertise along with plant speellic walkdo vns. Although VY is not a reduced scope plant, our method is founded on o agreernent with the following statement on page 12 of Referenco c):

"Well conducted, detallad walkdowns have been demonstrated to be the most important tool for identifying seismic weak links whose correction is highly cost offective."

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.e VERMONT YANKEE NUCLE AR POWER CORPOR ATION United States Nuclear Regulatory Commission September 18,1992 Page 6

4. As a reciplent of Generic Letter 87 20, and as a member of SOUG, VY intends to resolvo USl A 46 by implementing a program which fully moots the requirements set forth by the GIP and ondorsed by the NRC.

Satisfactory completion of this program will Insure seismio adequacy of Vermont Yankoo's identified Safe Shutdown Train (SST) equipment relative to the plant Ilconsed design basis and commensurate with j current Ilconsing criteria. To the extent that beyond design basis accidents rely on the same tritigating systems and structures as within-design basis accidents (which is the case to a large extent), the i substantial effort being performed by VY to resolve A-46 is expected to  ;

support many of the objectives of solsmic IPEEE. l C_oncluviqnj j This letter has provided you with the information requested in Reference e) regarding schedulo, methods and milestones for the VY IPEEE and thorofor j supersedes in its entirety prior subm!ttal (Referenco d). In order for Vermont Yankeo i to preparo for IPEEE offorts, we request that NRC provido concurronen of our plan and 1 scheduto by January 1.1993.

Very truly yours, Vermont Yankee Nuclear Power Corporation Q ff&Q C -

James P. Pelletier Vice President, Engineering cc: USNRC Region i Administrator USNRC Resident inspector - VYNPS .

USNRC Project Manager VYNPS """"*'*

4 > 84/VQ SALLY A SANDSTRUM a #  % 6 STATE OF VERMONT )

NOTARY PUBUC N [' / 'W f '# '

MM COUR WRMOM l-WINDHAM COUNTY My Imn Expires _A.ho/W hse (t*u<w:j '.

4 Then personally appeared before me, James P. Pelletler, who, being d , did sta

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le j is Vice President. Engineering of Vermont Yankee Nuclear Power Corporation, .

h411)la, lzed to execute and file the foregoing document in the name and on the behalf of Vermont Yankes Nuclear Power Corporation and that the statements therein are true to the best of his knowledge and bellsf.

Nv'bd R Sally A/ San'dstrum Notary Public -

My Commission Expires February 10,1995 l- _ _

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