ML20199F400

Forwards Request for Addl Info on Individual Plant Exam of External Events for Plant,Units 1 & 2

ML20199F400
Person / Time
Site:	Vogtle
Issue date:	11/19/1997
From:	Larry Wheeler NRC (Affiliation Not Assigned)
To:	Mccoy C SOUTHERN NUCLEAR OPERATING CO.
References
TAC-M83690, TAC-M83691, NUDOCS 9711240199
Download: ML20199F400 (6)

Text

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l November 19, 1997 Mr. C. K. McCoy Vice President Southern Nuclear Operating 1 Company, Inc. l P O. Box 1295 I Birmingham, Alabama 35201 l

SUBJECT:

REQUEST FOR ADDITIONAL INFORMATION ON THE INDIVIDUAL PLANT EXAMINATION OF EXTERNAL EVENTS VOGTLE ELECTRIC GENERATING PLANT, UNITS 1 AND 2 (TAC NOS. M83690 AND M83691)

Dear Mr. McCoy:

The NRC staff, in conjunction with Sandia National Laboratories and Brookhaven National Laboratory, has developed the enclosed request for additional information (RAl) based on its review of the Individual Plant Examination of External Events (IPEEE) for the Vogtle Electric Generating Plant, Units 1 and 2 (Vogtle). The RAI pertains to the IPEEE information on fire and seismic vulnerabilities. There are no questions in the high wind, flood, and other external events (HFO) area of the submittal. The enclosed questions have all been reviewed by the Senior Review Board (SRB). The SRB includes NRC staff and consultants with probabilistic risk assessment expertise in external events.

You are requested to provide a response to the enclosed questions not later than January 16, 1998. If there are any questions regarding this RAI, please have your representative contact me at (301) 4151444.

Sincerely.

ORIGINAL SIGNED BY:

Louis L. Wheeler, Senior Project Manager .

Project Directorate ll 2 Division of Reactor Projects - l/Il y)I Office of Nuclest Reactor Regulation Docket Nos. 50-424 and 50-425

Enclosure:

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%, / November 19, 1997 Mr. C. K. McCoy Vice President Southem Nuclear Operating Company, Inc.

P. O. Box 1295 -

Birmingham, Alabama 35201

SUBJECT:

REQUEST FOR ADDITIONAL INFORMATION ON THE INDIVIDUAL PLANT EXAMINATION OF EXTERNAL EVENTS VOGTLE ELECTRIC GENERATING  ;

PLANT, UNITS 1 AND 2 (TAC NOS. M83690 AND M63691)

Dear Mr. McCoy:

The NRC staff, in conjunction with Sandia National Laboratories and Brookhaven National Laboratory, has developed the enclosed request for additionalInformation (RAl) based on its review of the Individual Plant Examination of Extemal Events (IPEEE) for the Vogtle Electric Generating Plant, Units 1 and 2 (Vogtle). The RAI pertains to the IPEEE information on fire and seismic vulnerabilities. There are no questions in the high wind, flood, and other extemal events (HFO) area of the submittal. The enclosed questions have all been reviewed by the Senior Review Board (SRB). The SRB includes NRC staff and consultants with probabilistic risk assessment expertise in extemal events.

You are requested to provide a response to the enclosed questions not later than January 16, 1998, if there are any questions regarding this RAI, please have your representative contact me at (301) 415-1444.

Sincerely, aw< . -

Louis L. Wheeler, Senior Project Manager Project Directorate ll 2 Division of Reactor Projects 1/ll Office of Nuclear Reactor Regulation Docket Nos. 50-424 and 50-425 inclosure: Request for Additional Information i

cc w/ encl: See next page

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Vogtle Electric Generating Plant oc: 1 Mr. J.' A. Bailey Harold Rehels, Director I Manager, Licensing . Departmor

• of Natural Resources Southem Nuclear Operating 205 Butler Street, SE. Suite 1252 l

Company, Inc. i_ Atlanta, Georgia 30334 P. O. Box 1295 1  ;

l Blimingham, Alabama 352011295 Attomey General l Law Department  ;

Mr. J. B. Bsasley 132 Judicial Building .

e General Manager, Vogtle Eleo'ric Atlanta, Georgia 30334  !

Generating Plant ,

Southem Nuclear Operating Mr. R. D. Barker l Company, Inc. Program 'tasi;+r- - '

P. O. Box 1600 Fossil & Nuclear Operations .

Waynesboro, Gecrgia 30830 Oglethorpe Power Corporation 2100 East Exchange Place ,

Regional Administrator, hegion il P. O. Box 134g U. S. Nuclear Regulatory Tucker, Georgia 30085134g Commission Atlanta Federal Center _ Charies A. Patrizia. Esquire 61 Forsyth Street, SW., Suite 23T85 Paul, Hastings, Janofsky & Walker Atlanta, Georgia 30303 10th Floor 1299 Pennsylvania Avenue Office of Planning and Budget Washington, DC 20004 9500 ,

Room 6158 '

270 Washington Street, SW, Arthur H. Domby, Esquire

' Atlanta, Georgia 30334 Toutman Sanders NationsBank Plaza  !

Mr. J. D. Woodard 600 Peachtree Street, NE. t Executiva Vice President Suite 5200 -

Southem Nuclear Operating Atlanta, Georgia 30308-2216 '

Company, Inc.

P. O. Box 1295 _ Resident inspector Birmingham, Alabama 352011295 Vogtle _

8805 River Road Steven M. Jackson Waynesboro, Georgia 30830 Senior Engineer. Power Supply

-Municipal Electric Authority Office of the County Commissioner i of Georgia Burke County Cornmission 1470 Riveredge Parkway. NW. Waynesboro, Georgia 30830 Atlanta, Georgia 30328-4684  :

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Request for Additional information (RAl) Related to the Vogtle individual Plant Examination of External Evente (IPEEE) i i

Vulnerabuities to Firee

1. The screening of propagation pathway boundaries on the basis of combustible contents is  !

inappropriate for barriors rated at less than 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br />. The submittal lists the barrier rating j between some adjacent fire zones as 1.0 and 0.25 hour2.893519e-4 days <br />0.00694 hours <br />4.133598e-5 weeks <br />9.5125e-6 months <br />. There is no technical justification (as supported by NUREG 1547,

• Methodology for Developing and .

implementing Altemative Temperature Time Curves for Testing the Fire Resistance of  !

Barriers for Nuclear Power Plant Applications") to allow screening of propagation

, pathways when the only ortterion satisfied is that the estimated fire severity (in hours) is  ;

less than 75% of a 1.0 or 0.25-hour rated barrier. Please reevaluate the propagation e pathways when this ortterion is eliminated for these barriers, and assess the assoolated  ;

impact on the results.  ;

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2. There is an apparent error in the numbers listed in Table 4.1 3 for the scenario frequencies, conditional core damage probabilities, and core damage frequencies I (CDFs). Each column of numbers appears to be high by a factor of 10. This is noted  :

when comparing the numbers in the table to the description for Are zone 120 in the text, as well as when comparing the CDF values of the scenarios that were screened with the  ;

screening CDF value of 4.45E 8/yr. Please confirm the correct values for these  !

frequencies and probabilities. l t

3. Qualitative screening of some fire zones with safety-related equipment was based on the  ;

argument that the fire initiation frequencies are bounded by intomal events transient and loss of offsita power initiation frequencies. This argument is valid only if the anticipated conditional core damage probabilities for the fire initiators is less than or equal to the r conditional core damage probabilities for the intamal events initiators. Please justify the scresning that was performed in this manner.

4. The submittal notes that automatic fire detection systems and fire suppression systems were assumed to be installed per design specifications, following National Fire Protection Association and NRC guidelines, and were assumed to be maintained regularly. The

! submittal also indicates that fire detectors were assumed to be able to detect Are signatures at their location per design specifications. Also, automatic fire suppression systems were assumed to be sized to effectively mitigate a fire of the maximum postulated size at that location. Please provide the bases for these assumptions.

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5. It is important that the human error probabilities (HEPs) used in the screening phase of the analysis property renect the potential effects of flre (e.g., smoke, heat, loss of lighting, -

and poor communication), even if these effects do not directly cause equipment damage in the scenarios being analyzed, if these effecta are not treated, the HEPs may be -

optimistic and result in the improper screening of scenarios. Note that HEPs which are realistic with respect to an intomai events analysis could be optimistic with respect to a fire risk analysis, Please identify: (a) the scenarios screened out from further analysis whose quantification g

involved one or more HEPs, (b) the HEPs (descriptions and numerical values) for each of s these scenarios, and (c) how the effects (e.g., smoke, heat, loss of lighting and poor i communication) of the posWlated fires on HEPs were treated. ,

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Seismic Vulnerabilities  ;

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1. The refueling water storage tank (RWST) is a single component with no redundancy that is used in both success paths described in the submittal. Functional failure of this tank  !

due to earthquakes willlead to an unsuccessful shutdown in both paths. Although the ,

RWST is described as being highly f eliable in the submittal, quantification in terms of a  !

high confidence low probability of failure (HCLPF) value, which is requested for all safe shutdown equipment list components in reduced-scope plants, is not provided. Please l provide the HCLPF calculation or some other quantitative justification why the RWST has j en HCLPF at or above the Review Level Eerthquake (RLE) of 0.30  ;

2. In the descript on of the primary success path, the IPEEE states that *RCP (reactor coolant pump) seal injection is established using manual valves 1206 06152/151 to preclude the occurrence of a seal LOCA [ loss of coolant accident).' No further discussion is provided. Since the development of a seal LOCA would eliminate this success path, the prevention of a seal LOCA is very important. Please discuss the systems required to prevent a seal LOCA, the operator actions required to establish the functions of these systems, and the estimated failure rates of the operator actions (considering the existing j~

plant procedures, operator training, and the time allowed for the actions). Please include in the discussion the operation of the above-mentioned manual valves.

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3. For deeply embedded structures, the Vogtle IPEEE states that the original seismic analyses for a design basis es:thquake of 0.2g was sufficiently conservative to meet the requirements of an RLE of 0.3g, due to a scaling factor of 1.5 applied to the in structure response spectra. However, the purpose of the 1.5 scaling factor was to satisfy the NRC's concem, at the time of licensing, that the Standard Review Plan requirement for the deconvoluted motion to be no less than 60 percent of input motion at grade may not l have been met in the design basis analyses for deeply embedded structures. Therefore, in order to justify that sufficient margin exists in the original seismic analyses to meet an RLE of 0.30, the licensee should demonstrate that the deconvoluted motions at the foundation levels are no less than 60 percent of the input motion at grade without the annlication of the 1.5 factor. Please provide a comparison of the deconvoluted motions at the foundation levels with the specified input motion at the grade from the original seismic analyses without the scaling factor of 1.5. If the deconvoluted motions at foundation levels are less than 60 percent of the input motion at grede, please provide additional justification of why the plant HCLPF is 0.3g, or revise your estimate of the plant HCLPF ,

as appropriate. '

4. The following questions pertain to the shallow / surface mounted structures: ,

(a) Conflicting statements were made in the submittal regarding scaling factors applied i for shallow / surface-mounted structures. Section 3.1.3 of the submittal states *(t]he

- Instructure response spectra (IRS) were conservatively scaled up by a factor of 1.5 ,

for use in the IPEEE program.' However, Section 3.1.3.1 states "[fjor the shallow-embedded structures, the original demand peak ground acceleration (pga) equals 0.2g. If the equipment to be analyzed is flexible and the static equivalent method is used, then the peak acceleration mdtiplied by a factor from 1.0 to 1.5 could have i

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been used. For those osses, wherein the equipment is rigid, the ZPA (aero period ecceleration) could have been used.* Please provide clarification of the above  :

statements and provide the scaling factor actually applied to shallow / surface.

mounted structures.  ;

t'u) Per EPRI NP4041-SL requirement, linear scaling is applicable to rock sites, and .

therefore may not be applicable to the Vogtle site, which is a soil site. For soil  ;

sNes, a new analysis is recommended by EPRI. To justWy the use of linear scaling, a licensee should demonstrate that the changes in composite modal damping due to l the soil-structure interaction effects will not lead to optimistic structural responses, f ,

Please provide quantified justification for the application of the scaling method to the  :

Vogtle site. t

5. The turbine building was evaluated for seismic interaction concems because of its -

proximity to the control building. However, the screening criteria designed for Category 1 structures appear to oe improperty applied in the Vogtle IPEEE to the turbine building,  !

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which is a Category ll structure. Since Category 11 structures are not designed to the -

same criteria applied to Category I structures, there is less confidence regarding the

= inherent seismic margin in the original design. Therefore, using the screening criteria for j - Categnry I structures to screen out the turbine building as having an HCLPF of 0.3g i appears to be incorrect. For the turbine building, please follow the guidance for

evaluation of Category ll structures, as recommended in EPRI NP4041 SL and provide your results.

l- 6. The submittal states that several open items documented in Appendices 3.J and 3.K were

scheduled for closure by August 1,1996, i.e., after the IPEEE submittal had been l completed and forwarded to the NRC. Please provide the status of these items scheduled for closure. For the closed items please provide the details of their resolution.

High Wind, Flood, and Other External Events (HFO)  ?

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i There is no RAIin the HFO area.

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