ML20198A299
| ML20198A299 | |
| Person / Time | |
|---|---|
| Site: | Beaver Valley |
| Issue date: | 12/08/1997 |
| From: | Brinkman D NRC (Affiliation Not Assigned) |
| To: | Cross J DUQUESNE LIGHT CO. |
| References | |
| GL-88-20, TAC-M83590, NUDOCS 9801050336 | |
| Download: ML20198A299 (8) | |
Text
December 8, 1997 Mr. J. E. Crass President-Generation Group
.Duquesne Light 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. 1 (BVPS-1) (TAC NO. M83590)
Dear Mr. Cross:
By letter dated June 30, 1995, Duquesne Light company (DLC) submitted the results of its IPEEE for BVPS-1 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 (BNL) and Sandia National
-Laboratories (SNL), has reviewed DLC's June 30, 1995, 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 RAI.
There is no RAI in the high wind, floods, and other (HFO) external events area.
DLC is requested to 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,
/S/
Donald S. Brinkman, Senior Project Manager Project Directorate I-2 Division of Reactor Projects - I/II Office of Nuclear Reactor Regulation Docket No. 50-334
Enclosure:
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WASHINGTON, D.C. 30e46-0001 December 8, 1997 Mr. J. E. Cross President-Generation Group Duquesne Light 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. 1 (BVPS-1) (TAC NO. M83590)
Dear Mr. Cross:
By letter dated June 30, 1995, Duquesne Light Company (DLC) submitted the results of its IPEEE for BVPS-1 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 (BNL) and Sandia National Laboratories (SNL), has reviewed DLC's June 30, 1995, 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 RAI.
There is no RAI in the high wind, floods, and other (HFO) external events area. DLC is requested to 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, n"Y h, 0 Donald S. Brinkman, Senior Project Manager Project Directorate I-2 Division of Reactor Projects - I/II Office of Nuclear Reactor Regulation Docket No. 50-334
Enclosure:
RAI cc'w/ encl:
See next page
p J. E. Cross Beaver Valley Power Station Duquesne Light Company Units 1 & 2 I
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 Comission Building 3, Room 319 475 Allendale Road Capitol Complex King of Prdssia, PA 194M 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 Columbus, OH 43266-0573 Director, Pennsylvania Emergency Duquesne Light Company llanagement 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 Post Office Box 1049 Columbus, OH 43266-0149 Dr. Judith Johnsrud National Energy Committee Sierra Club 433 Orlando Avenue State College, PA 16803 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-50SB-7) 1
RE0 VEST FOR ADDITIONAL INFORMATION REGARDING INDIVIDUAL PLANT EXAMINATION OF EXTERNAL EVENTS BEAVER VALLEY POWER STATION. UNIT NO. 1 DOCKET NO. 50-334 Fire events 1.
It is important that the human error probabilities (HEPs) used in the detailed analysis phase of a fire PRA properly 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 scenarios. Note that HEPs which are realistic with respect to an internal events analysis could be optimistic with respect to a fire risk analysis.
The submittal does net 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 Generic Letter (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 potential improvements 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 fire in the plant (e.g., the main control room) might lead to potential contrni systems vulnerabilities.
Given a fire in the plant, the likely sources of control systems interactions could happen between the control room, the remote shutdown panel, and shutdown systems.
Specific areas that have been identified as requiring attention in the resolution of this issue include:
Enclosure
1 1
1 i
[
2 (a) Electrical independence of the remote shutdown control systems: The primary concern of control systems interactions occurs at plants that do not provide independent remote shutdown control systems.
The electrical independence of the remote shutdown panel and the evaluation of the level of indication ud control of remote shutdown control and monitoring circuits need to be asssssed.
(b) Loss of control equipment or powcr before transfer: The potential for loss of control power for certain control circuits as a result of hot shorts and/or blowr fuses before transferring control from the main control room to remote shutdown locations needs to be assessed.
(c) Spurious actuation of components leading to component damage, loss-of-coolant accident (LOCA), or interfacing systems LOCA: The spu,ious actuation of one or more safety-related to safe-shutdown-related components as a result of fire-induced cable faults, hot shorts, or ccmponent failures leading to component damage, LOCA, or interfacing systems LOCA, prior to taking control from the remote shutdown manel, needs to be assessed. This assessment also needs to include tie spurious starting and running of pumps as well as the spurious reposittning o. valves.
(d) Total loss of system function: The potential for total loss of system function as a result of fire-induced redundant component failures or electrical distribution system (power source) failure needs to be addressed.
Please describe the BVPS-1 remote shutdown capability, including the nature and location of the shutdown station (s), as well as the types of control actions which can be taken from :.he remote panel (s).
Describe how DLC's procedures provide for transfer of control to the remote station (s).
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 risk contribution of these types of failures (if these failures are screened, please provide the basis for the screening).
Finally, 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 syster LOCA prior to taking control from the remote shutdown panel (considering both spurious starting ard running of pumps as well as the spurious repositioning of valves).
3.
The previous question addresses the potential for hot shorts due to fires in the main control roor.
Fires in other areas of the plant can also result in hot shorts that result in adverse conditions.
Hot shorts in control cables can simuste the closing of control switches leading, for example, to the repositioning of valves, spurious operation of motors and pumps, or the shutdown of operating equipment. 1hese types
3 of faults might, for example, lead to a LOCA, diversion of flow within various plant systems, deadheading and failure of important pumps, premature or undesirable switching of pump suction sources, or undesirable equipment operations.
In instrumentation circuits hot shorts may cause misleading plant readings potentially leading to inappropriate control actions or generation of actuation signals for emergency safeguard features. From the submittai, it cannot be determined to what extent the licensee has considered hot shorts as a failure mode for control or instrumentation cables.
In particular, hot short considerations should include the treatment of conductor-to-conductor shorts within a given cable.
Discuss to what extent these issues have been considered in the IPEEE.
If they have not ben considered, please provide an assessment of how inclusion of potential hot shorts would impact the quantification of fire risk scenarios in the IPEEE.
4.
The BVPS-1 fire PRA uses two factors to estimate fire-induced component fVagilities; the severity and geometric factors. The severity factor is used in 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 component 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 code runs were used to establish the critical radius from the transient fire where component damage would not occur.
The submittal does not provide information on the development of the fire severity and geometric factors.
Specifically, the data and engineering judgement used in the development of the fire severity factor and the types and sizes of transient fires used in the geometric factor evaluations are not dascribed.
Please provide this additional information concerning the development of these factors.
5.
The screening of propagation pathway boundaries on the basis of combustible contentr. is inappropri te 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 Atstification (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 a rated barrier.
Please reevaluate the propagation pathways when this criterion is eliminated for these barriers, and assess the associated imp ut on the results.
6.
Table 4-5 in the submittal indicates that fire zones were qualitatively screened on th.. basis that no scram mechanisms were identified even theugh safety-relates equipment is contained in the zone. Ateas screened include portions of the intake structure, safety injection pump cubicles, and recirculation spray pump cubicles. Although a fire may not result in an automatic scram, there is a potential for a manual
I 4
scram or controlled sHtdown initiated by procedures or due to technical l
specification requirements resulting from fire-induced component damage.
Address whether a manual scram or controlled shutdown could be expected in the zones screened by this criteria.
If a scram or shutdown requirement is identified, please provide a detailed evaluation of the zones that were incorrectly screened.
7.
Two fire scenarios (GW-1/GW-1 and DC-1/DC-1) were identified in Figures 4-2 through 4-7 but are not listed in Table 4-2 nor do they appear to have been quantitatively evaluated. Please address the quantitative significance of the fires associated with these areas / scenarios.
Seismic events 1.
According to Section 3.1.4.2 of the submittal, a relay evaluation was not performed as part of the IPEEE study because, (i) " bad-actor" relays would be resolved through the on-going USI A-46 program, and (ii) the BVPS-1 plant, which is binned in the 0.3g focused-scope slant category, can actually be regarded as a reduced-scope plant.
As tle basis of the statement in (ii) above, Section 3.1.4.2 of the submittal asserts that "the margin of safety over the safe shutdown earthquake (SSE) remains the same as originally intended for this group of plants when the more recent Lawrenco Livermore National Laboratory (LLNL) curves are used."
However, according to Figure 3.11 of the submittal, the median response spectrum used for the IPEEE study is much lower than the design spectrum at a frequency range lower than 10 Hz. This would indicate that the seismic analyses performed for the IPEEE do nat confirm the seismic margin over the SSE level. Moreover, according to Section 3.1.1.4 of NUREG-1407, low ruggedness relays that are not included in the USI A-46 program need to be reviewed as part of the IPEEE study.
Please provide information regarding the actions taken for such low ruggedness relays which are outside of the scope of the USI A-46 program.
2.
The BVPS-1 iPEEE used the uniform hazard spectrum (UHS) as a basis for much of the analysis.
a) According to Section 3.1.3 of the submittal, a new soil-structure interaction (SSI) analysis was not performed in the IPEEE study.
Instead, the existing dnign floor spectra were scaled (down) using the ratios of the median uniform hazard spectrw (VHS) to the design spectrum at each frequency.
This procedure may not be acceptable for a soil site becuse of the nonlinearity in soil properties (dampirig and soil stiffness).
Please explain how the nonlinearity in soil properties was accounted for in calculating new floor
- spectra, b) According to Figure 3.11 of the submittal, the UHS seems to be anchored using the spectral value at 25 Hz. However, the zero period acceleration (ZPA) value can be determined separately from the hazard curves for peak gro...id acceleration (PGA) values, and
7 5-l l
this IPA value should be used for anchoring the UHS (at approximately 80 ~ 100 Hz).
Please explain the basis of how the UHS was anchored in the BVPS-1 seisnic analysis.
c) To provide confider.ce in the adequacy of the evaluated component fragility values, please provide the detailed calculation results i
for the following components:-
l 1.
125V batteries and battery racks-(median = 0.2g) 11.
block walls (median = 0.52g) 111.
Emergency. diesel generator (EDG) fuel. oil storage tank (med'an-1.31g)
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3.
According to Section 3.1.4.3 of the submittal, a high confidence low prcbability failure (HCLPF) value of 0.5g was used for component screening.
By using this criterion, a total of only 13 components and structures were screerad-in for system analysis.
Please orovide the basis for the screening criteria used, and explain why a higher g-value for screening would not be appropriate for obtaining a more complete analysis.
4.
The top 100 sequences are presented in the submittal; however it is t
difficult to understand their meaning, as split fraction acronyms are used which are not explained. A discussion of a few top sequences would be helpful in understanding the results obtained in the IPEEE.
Please provide.a discussion of the to 10 sequences, including the acceleration level used for the sequence, tie seismic and-independert failures which occur during the sequence, as well as the operator actions and their timing.
5.
Small LOCAs can be significant contributors to seismic core damage frequency.
Please describe DLC's treatment of small LOCAs in the PRA model.
Please provide the mechanisms which were considered for small l
LOCAs, provide the fragility parameters for such failure mechanisms, and provide the basis for screening if such was performed.
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