ML20236V452

Forwards RAI Re Response to GL 88-20,suppl 4,dtd 910628 Concerning Seismic & Fire Analyses in Ipeee.Response Requested within 60 Days of Receipt of Ltr

ML20236V452
Person / Time
Site:	Beaver Valley
Issue date:	07/28/1998
From:	Brinkman D NRC (Affiliation Not Assigned)
To:	Cross J DUQUESNE LIGHT CO.
References
GL-88-20, TAC-M83591, NUDOCS 9808030198
Download: ML20236V452 (8)

Text

July 28,1998 Mr. J. E. Cross President-Generation Group Duquesne Light Company Post Office Box 4 Shippingpod, PA 15077

SUBJECT:

REQUEST FOR ADDITIONAL INFORMATION (RAI) REGARDING INDIVIDUAL PLANT EXAMINATION OF EXTERNAL EVENTS (IPEEE) FOR BEAVER VALLEY POWER STATION, UNIT NO. 2 (BVPS-2) (TAC NO. M83591) l

Dear Mr. Cross:

By letter dated September 30,1997, Duquesne Light Company (DLC) submitted the results of its IPEEE for BVPS-2 in response to NRC Generic Letter 88-20, Supplement 4, dated June 28, 1991. The NRC staff, in conjunction with its contractors, Brookhaven National Laboratory and Sandia National Laboratories, has reviewed DLC's September 30,1997, submittal and has determined that additional information is required to complete our review. The RAI is related to the seismic and fire analyses in the IPEEE. The specific issues are noted in the enclosed RAl. .

There is no RAI in the high wind, floods, and other extemal events area. DLC is requested to i provide this additional information within 60 days of receipt of this letter to enable the NRC staff to complete its review within a timely manner.

Please contact me at (301) 415-1409 if you have any questions on this matter.

Sincerely,

/5/

Donald S. Brinkman, Senior Project Manager Project Directorate 1-2 Division of Reactor Projects - 1/11 Office of Nuclear Reactor Regulation Docket No. 50-412 7

Enclosure:

RAI f

, cc w/ encl: See next page DISTRIBUTION Docket File - MO'Brien 9te' " - m

/~ T/ ,

PUBLIC .OGC i3Nb d ,. 7 f,

. , , - , , g, PDI-2 Reading ACRS JZwolinski MEvans, RGN-l RCapra EChelliah L DBrinkman RHeman MCunningham ARubin OFFICE PDI-2/PM A , z PDl-h(dlb PDI-2/D NAME DBrinkma MdE$n RCapra '"'

DATE 7 / 0 /98 b/N98 1 /28/98 OFFICIAL RECORD COPY /

DOCUMENT NAME: BV83591.RAI 9808030198 980728 PDR n

F ADOCK 05000412 PDR

,@ Clouq g i UNITED STATES g j NUCLEAR REGULATORY COMMISSION

)

{

WASHINGTON, D.C. 20eeH001

\ . . . . . 8,o # July 28,1998 l

Mr. J. E. Cross President-Generation Group l

Duquesne Ught Company

]

Post Office Box 4 Shippingport, PA 15077

SUBJECT:

REQUEST FOR ADDITIONAL INFORMATION (RAI) REGARDING INDIVIDUAL PLANT EXAMINATION OF EXTERNAL EVENTS (IPEEE) FOR BEAVER VALLEY POWER STATION, UNIT NO. 2 (BVPS-2) (TAC NO. M83591)

Dear Mr. Cross:

By letter dated September 30,1997, Duquesne Light Company (DLC) submitted the results of its IPEEE for BVPS-2 in response to NRC Generic Letter 88-20, Supplement 4, dated June 28, 1991. The NRC staff, in conjunction with its contractors, Brookhaven National Laboratory and Sandia National Laboratories, has reviewed DLC's September 30,1997, submittal and has determined that additional information is required to complete our review. The RAI is related to the seismic and fire analyses in the IPEEE. The specific issues are noted in the enclosed RAl.

There is no RAI in the high wind, floods, and other extemal events area. DLC is requested to provide this additional information within 60 days of receipt of this letter to enable the NRC staff {

l to complete its review within a timaly manner. I Please contact me at (301) 415-1409 if you have any questions on this matter.

Sincerely,

& ./d -

Donald S. Brinkman, Senior Project Manager Project Directorate 1-2 Division of Reactor Projects - t/II ,

Office of Nuclear Reactor Regulation 1 Docket No. 50-412 .

l

Enclosure:

RAI cc w/ encl: See next page i

i l

l

\

J. E. Cross Beaver Valley Power Station, Units 1 & 2 Duquesne Light Company cc:

Jay E. Silberg, Esquire Bureau of Radiation Protection Shaw, Pittman, Potts & Trowbridge Pennsylvania Department of 2300 N Street, NW. Environmental Resources Washington, DC 20037 ATTN: Michael P. Murphy Post Office Box 2063 Director-Safety and Licensing Harrisburg, PA 17120 Department (BV-A)

Duquesne Light Company Mayor of the Borrough of Beaver Valley Power Station Shippingport PO Box 4 Post Office Box 3 Shippingport, PA 15077 Shippingport, PA 15077 Commissioner Roy M. Smith Regional Administrator, Region I West Virginia Department of Labor U.S. Nuclear Regulatory Commission Building 3, Room 319 475 Allendale Road Capitol Complex King of Prussia, PA 19406 Charleston, WVA 25305 Resident inspector Director, Utilities Department U.S. Nuclear Regulatory Commission Public Utilities Commission Post Office Box 298 180 East Broad Street Shippingport, PA 15077 i Columbus, OH 43266-0573 Director, Pennsylvania Emergency Duquesne Light Company Management Agency Beaver Valley Power Station Post Office Box 3321 PO Box 4 Harrisburg, PA 17105-3321 Shippingport, PA 15077 ATTN: S. C. Jain, Vice President Ohio EPA-DERR Nuclear Services (BV-A)

ATTN: Zack A. Clayton i

Post Office Box 1049 I Columbus, OH 43266-0149 Dr. Judith Johnsrud National Energy Committee Sierra Club i 433 Orlando Avenue  !

State College, PA 16803 l l

Duquesne Light Company Beaver Valley Power Station PO Box 4 Shippingport, PA 15077 ATTN: R. L. Grand, Division Vice President, Nuclear Operations Group and Plant Manager (BV-SOSB-7) j

L REQUEST FOR ADDITIONAL INFORMATION REGARDING INDIVIDUAL PLANT EXAMINATION OF EXTERNAL EVENTS (IPEEE)

BEAVER val i FY POWER STATION. UNIT NO. 2 DOCKET NO. 50-412 Fire events

1. It is important that the human error probabilities (HEPs) used in the detailed analysis phase of a fire PRA property reflect the potential effects of fire (e.g., smoke, heat, and loss of lighting), even if these effects do not directly cause equipment damage in the scenarios being analyzed. If these effects are not treated, the HEPs may be optimistic and result in incorrect quantification of unscreened fire scenarios. Please note that HEPs which are conservative j with respect to an intemal events probabilistic analysis could be non-conservative with respect to a fire risk analysis.

The submittal does not indicate whether or not fire impacts were included in the assessment of human actions in the final quantification. Please identify: a) the HEPs credited in the final quantification including recovery actions (descriptions and numerical values), and b) how the effects of the postulated fires were treated in calculating the HEPs and recovery actions.

2. NUREG-1407, Section 4.2 and Appendix C, and GL 88-20, Supplement 4, request that documentation be submitted with the IPEEE submittal with regard to the Fire Risk Scoping Study (FRSS) issues, including the basis and assumptions used to address these issues, and a discussion of the findings and conclusions. NUREG-1407 also requests that evaluation results and potentialimprovements be specifically highlighted. Control system interactions involving a combination of fire-induced failures and high probability random equipment failures were identified in the FRSS as potential contributors to fire risk.

The issue of control systems interactions is associated primarily with the potential that a postulated fire in a fire area (e.g., the main control room (MCR)) might lead to potential degradation of safety system redundancy due to hidden design vulnerabilities of control systems. Given an MCR fire, the likely sources of control systems interactions could happen between the MCR, the remote shutdown panel (RSP), and shutdown systems. Specific areas that have been identified as requiring attention in the resolution of this issua include: l (a) Electricalindependence of the remote shutdown coritrol systems: The primary concern of I control systems interactions occurs at plants that do not provide independent remote i shutdown control systems. The electricalindependence of the remote shutdown panel i and the evaluation of the level of indication and control of remote shutdown control and l monitoring circuits need to be assessed. )

(b) Loss of control equipment or power before transfer: The potential for loss of control power for certain control circuits as a result of hot shorts and/or blown fuses before ,

transferring control from the MCR to remote shutdown locations needs to be assessed.

ENCLOSURE

4 (c) Spurious actuation of components leading to component damage, loss-of-coolant accident (LOCA), or interfacing systems LOCA: The spurious actuation of one or more safety-related to safer-shutdown-related components as a result of fire-induced cable faults, hot shorts, or component failures leading to component damage, LOCA, or interfacing systems LOCA, prior to taking control from the remote shutdown panel, needs to be assessed. This assessment also needs to include the spurious starting and running of pumps as well as the spurious repositioning of valves.

(d) Totalloss of system function: The probability of totalloss of system function as a result of redundant train (and/or component) failures or electrical distribution system (power sourc'e) failure during a fire needs to be addressed.

Please describe the BVPS-2 remote shutdown control system capability, including the nature and location of the shutdown station (s), as well as the types of control actions which can be taken from the remote shutdown panel (s). Please describe how plant procedures provida for transfer of control to the remote shutdown panels. Please provide an evaluation of whether loss of control power due to hot shorts and/or blown fuses could occur prior to transferring control to the remote shutdown location and identify the core damage frequency (CDF) contribution of these types of failures. If these failures have been screened in the IPEEE, please provide the basis for the screening. Finally, please provide an evaluation of whether spurious actuation of components as a result of fire-induced cable faults, hot shorts, or component failures could lead to component damage, a LOCA, or an interfacing systems LOCA prior to taking control from the RSP (considering both spurious starting and running of pumps as well as the spurious repositioning of valves).

3. The BVPS-2 fire PRA uses two factors to estimate fire-induced component fragilities: the severity factor and geometric factor. The severity factor is used to estimate the fire-induced damage probability of a component due to component-induced fires. Generic fire data and engineering judgement were used to develop curves depicting the probability of co.mponent damage as a function of the distance from the fire source. The geometric factor is used to estimate the probability of component damage from transient fires. Multiple COMPBRN-ille code runs performed for the BVPS-2 PRA were used to establish the critical radius from the transient fire where component damage would not occur.

The response to this question submitted for BVPS-1 indicated that the data and engineering judgement used in the development of the fire severity factor are no longer available, and thus new estimates of the fire severity factors were used in a sensitivity evaluation. In addition, the use of the geometric factor was also described, and a sensitivity study was performed in which no credit was taken for the geometric factor. However, the types and sizes of transient fires used in the geometric factor evaluations were not described. Please provide this additionalinformation concoming the development of the geometric factors. In addition, repeat the sensitivity studies, performed in response to the question for BVPS-1, for i BVPS-2. l 4, The screening cf propagation pathway boundaries on the basis of combustible contents is e inappropriate for barriers 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 />. There is no technical justification (as supported by NUREG-1547) to allow screening of propagation pathways when the only criterion satisfied is that the estimated fire severity (in hours) is less than 50% of the barrier rating.

I

i A

3-Please re-evaluate the propagation pathways when this criterion is sliminated for these barriers, and assess the associated impact on the fire-induced CDF results.

5. Table 4 5 in the submittal indicates that fire zone: were qualitatively screened on the basis that no scram mechanisms were identified even tnough safety-related equipment is contained in the zone. Areas screened include portions of the intake structure, portions of the primary auxiliary building, and two battery rooms. Although a fire may not result in an automatic scram, there is a potential for a manual scram or controlled shutdown initiated by procedures or due to technical specification requirements resulting from fire-induced component damage. Please address whether a manual scram or controlled shutdown could be expected as a result of equipment failures in the zones screened by this criterion, if a scram or shutdown requirement is identified, please provide a detailed evaluation of the fire CDF of the zones that were screened using this criterion.

6. Table 4 5 in the BVPS-2 IPEEE submittal also indicates that fire zones were qualitatively screened on the basis that no IPE equipment was identified in the fire zone. Fire zones screened include the RSP room, portions of the control building, and cable vault areas.

However, it is not clear from the submittal that the IPE equipment includes all Appendix R equipment and controls. Since it is likely that fire procedures would direct the operators to use Appendix R equipment in case of a severe fire and to use the altemate shutdown panels when control room fires require evacuation of the MCR, it is important that any fire zones containing Appendix R equipment not be qualitatively screened.

Please clarify whether any of the fire zones screened by this criterion contain Appendix R equipment. If any fire zones were screened by this criterion, please provide a revised CDF evaluation of these fire zones.

7. Fires that could affect portions of both BVPS-1 and BVPS-2 were not considered. For dual-unit sites, there are three issues of potential interest. Hence, please address the following:

(a) A fire in a shared area of the BVPS facility might cause a simultaneous or a delayed demand for a trip of both units. This may complicate the response of operators to the fire event, and may create conflicting demands on plant systems which may be shared between two units. Please provide the following information regarding this issue: (1) identify all fire areas that are shared between two units and the potentially risk-important syste.ns/ components for each unit that are housed in such shared fire zones, (2) for each sha'ed fire zone identified in (1), provide an assessment of the associated dual unit fire CDF contribution, and (3) for the special case of the MCR, assess the CDF contribution for scenarios involving a fire or smoke-induced evacuation of the MCR with subsequent shutdown of both units from the RSPs.

l (b) At some dual-unit sites the safe shutdown path for a given unit may call for cross-connects to a sister unit in the event of certain fires. Hence, the fire analysis for BVPS-2 should include the unavailability of the cross-connected equipment due to outages at the sister unit (e.g., routine test and maintenance outages, and the potential that normally available equipment may be unavailable during extended refueling outages at the sister unit). Please provide the following information regarding this issue:

4 (1) indicate whether any fire-related safe shutdown procedures call for unit cross-connects, and (2) 17 any such cross-connects are required, determine the impact on the overall fire-icduced CDF for the BVPS-2 facility if the SVPS-1 equipment is included in the assessment.

(c) Propagation of fire, smoke, and suppressants between fire zones containing equipment for one unit to fire zones containing equipment for the other unit also can result in dual-unit propagation scenarios. Hence, the fire assessment for BVPS-2 should include analyses of fire scenarios addressing propagation of smoke, fire and suppressants to and from fire zones containing equipment for BVPS-1. From tne information in the BVPS-2 IPEEE submittal, it is not clear whether these types of scenarios were considered and evaluated. Please clarify whether such fire propagation scenarios were addressed in the BVPS-2 IPEEE submittal. If not, please provide an evaluation of the CDF contribution of such dual-unit propagation scenarios.

Seismic eHDif

1. The BVPS-2 IPEEE used the uniform hazard spectrum (UHS) as a basis for fragility quantification. This UHS has an unusual spectral shape that exhibits a pattem of consistent decrease of spectral amplitude for frequencies less than 10 Hz, and shows no spectral amplification above peak ground acceleration (PGA). The BVPS-2 IPEEE submittal seems to recognize the unrealistic shape of the UHS, compared to typical design response spectra or spectra generated from real earthquakes. The spectral shape of a seismic input plays an important role in fragility quantification. Fragility of a component is computed based on the median capacity and beta values. The spectral shape of the seismic input significantly influences computations of the median capacity, which is usually expressed as a percentage of g in PGA. Therefore, different spectral shapes should result in different fragility calculations for components that are less than rigid, and this in tum may have an impact on the evaluation of the seismic accident sequences.

a) In examining the UHS and the hazard curves provided in the IPEEE submittal, it is noted that the UHS is cut off at 25 Hz, not the zero-period acceleration (ZPA) frequency. The

, ZPA of the UHS, however, may be located from the hazard curve for the 10,000-year l' retum period and is equal to about 0.09g PGA, which is 40 percent less than the spectral amplitude at the 25 Hz cutoff frequency. If the UHS is extended to the ZPA, the spectral shape will change to one comparable to a more typical response spectra. Please discuss l

the impact on the fragility calculations of using the corrected spectral shape of the UHS.

If numerical changes in the fragility calculations result, please discuss the effect of these changes in the fragility of applicable equipment and structures (including tanks) on the determination of the seismic accident sequences.

b) According to Section 3.1.3 of the BVPS 2 IPEEE submittal, a new soil-structure interaction (SSI) analysis was not performed. Instead, the existing design floor spectra were scaled using the ratios of the median uniform hazard spectrum (UHS) to tne design spectrum at each frequency. EPRI NP-6041-SL, Section 4 provides a guideline on scaling of in-Structure Spectra. There are two essentialingredients in the guideline.

First, the ground input spectral shapes should be comparable, and second, the scaling should be performed on the ZPA of the floor response spectra (FRS), using the ratio of

ei 4

the peak ground spectral accelerations at the dominant structural response frequency.

Neither of these requirements was complied with in the scaling procedure used in the BVPS-2 IPEEE study. Please provide justification for the scaling procedure used in the IPEEE, and if some commonly used reference was used, please provide any relevant reference meterials that may facilitate the staff's IPEEE review.

c) The BVPS-2 design basis spectrum has a shape comparable to the NUREG/CR-0098 median spectra, which are used as the general seismic criteria for the seismic IPEEE evaluations. Please discuss the results of the fragility calculations if the NUREG/CR-0098 median spectrum shape is used, and discuss the impact, if any, on the BVPS-2 seismic accidence sequences.

d) In Section 3.1.3 of the IPEEE submittal, it is stated that for initial screening the spectral shape of NUREG/CR-0098 anchored to 0.3g was used. However, subsequently, a j second screening was perfomied using 0.5g threshold criteria. It is unclear whether the second screening was performed consistently, i.e., using the spactral shape of L NUREG/CR-0098 anchored to 0.3g. Please provide clarification. In addition, the bulk of the IPEEE fragility data, expressed as a percentage of g, came from generic information.

Please describe with what spectral shape these generic fragility data are associated.

e) Please provide the detailed fragility calculations (including also the natural frequency characteristics with the assumed SSI effects, if any, and floor response spectra used) for the following components. If possible, please use the corrected UHS shape (as discussed above) and the NUREG/CR-0098 median spectrum.

. Reactor Coolant Pumps (HCLPF = 0.61g)

. Cable Trays and supports (HCLPF = 0.65g)

. Heating ventilation and air conditioning-related ducting and supports (HCLPF =

0.65g)

. Boric acid tanks (HCLPF = 2.45g)

. Emergency diesel (HCLPF = 0.28g)

. Emergency Response Facility (ERF) diesel generator (HCLPF = 0.26g)

2. The top 100 sequences are presented in the IPEEE submittal; however it is difficult to understand their meaning, as split fraction acronyms (a unique PRA (Probabilistic Risk Assessment) term) are used which are not explained. A discussion of a few top sequences would be helpful in understanding the seismic vulnerability results obtained in the IPEEE.

Please provide a description of the top 5 sequences, including the acceleration levels used for the sequences, the seismically induced failures, and non-seismic and human failures which occur during the sequence, as well as the required operator actions and their timing. If fragility estimates of equipment and structures are revised as a result of Request for Additional Information (RAl) No.1 above, and this results in a different set of top 5 ,

sequences, please also provide the description of the new top five sequences.  ;

i 3. The instrument air system could affect containment performance because it may be needed for motive power for isolation valves and for the functioning of inflatable containment hatches. 1 There is no discussion in the subnittal as to how failures of the instrument air system affects containment performance issues. Please provide such a discussion.

Hioh wind. floods and other extemal events (HFO)

There are no RAls in this area.

L