ML20203C529

Forwards RAI Re IPEEE Submittal,Which Provided Final Response to GL 88-20,suppl 4, IPEEE for Severe Accident Vulnerabilities. Response Requested within 60 Days of Receipt of Ltr

ML20203C529
Person / Time
Site:	Hatch
Issue date:	12/08/1997
From:	Olshan L NRC (Affiliation Not Assigned)
To:	Sumner H SOUTHERN NUCLEAR OPERATING CO.
References
GL-88-20, TAC-M83628, TAC-M83629, NUDOCS 9712150332
Download: ML20203C529 (8)

Text

7 December 8, 1997 Mr. H. L. Sumner, Jr.

Vice President - Nuclear Hatch Project Southern Nuclear Operating Company, Inc.

Post Office Box 1295 Birmingham, Alabama 35201-1295

SUBJECT:

REQUEST FOR ADDITIONAL INFORMATION ON HATCH INDIVIDUAL PLANT EXAMINATION OF EXTERNAL EVENTS (IPEEE) SUBMITTAL (TAC NOS.

M83628 AND M83629)

Dear Mr. Sumner:

By letter dated January 26,1996, you submitted the results of the IPEEE evaluations for the Edwin I. Hatch Nuclear Plant, Units 1 and 2. Your submittal provided the final response t Generic Letter 88-20, Supplement 4, " Individual Plant Examination of Extemal Events (TcEE) for Sever Acciderit Vulnerabil: ties." Enclosed is a request for additional information (RAl) that we need to complete our review. This RAI is related to fire and was developed by our co,1 tractor, Sandia National Laboratories. No RAI is needed in the areas of seismic, high wind, flood, or other external events of the IPEEE submittal.

Your response is requested within 60 days of receipt of this letter. If you have any questions, please contact me at (301) 415-1419.

Sincerely, ORIGINAL SIGNED BY:

Leonard N. Olshan, Project Manager Project Directorate 11-2 Divisien of Reactor Projects -Illi Offi.:e of Nuclear Reactor Regulation Docket Nos. 50 321 and 50-366

Enclosure:

As stated I

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NUCLEAR REGULATORY COMMISSION WASHINGTDN, D.C. 20655-0001 December 8, 1997

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Mr. H. L. Sumner, Jr.

Vice President - Nuclear Hatch Project .

Southem Nuclear Operating ,

Company, Inc.

Post O ice Box 1295 Birmingham, Alabama 352011295

SUBJECT:

REQUEST FOR ADDITIONAL INFORMATION ON HATCH INDIVIDUAL PLANT EXAMINATION OF EXTERNAL EVEN' S (IPEEE) SUBMITTAL (TAC NOS.

M83628 AND M83629)

Dear Mr. Sumre .

By letter dated January 26,1996, you submitted the results of the IPEEE evaluations for the Edwin 1. Hatch Nuclear Plant, Units 1 and 2. Your submittal provided the final response to Generic Letter 88-20, Supplement 4, "Indiv! dual Plant Examination of Extemal Events (IPEEE) for Sever Accident Vulnerabilities." Enclosed is a request for additional information (RAl) that we need to comp!ete our review. This RAI is related to fire and was developed by our contractor, Sandia National Laboratories. No RAI is needed in the areas of seismic, high wind, flood, or other extemal events of the IPEEE submittal.

Your response is requested within 60 days of receipt of this letter. If you have any questions, please contact me at (301) 415-1419.

Sincerely, 3

f.fst /)hSv Lonnard N. Olshan, Project Manager Project Directorate 112 Division of Reactor Projects -l/II Office of Nuclear Reactor Regulation Docket Nos. 50-321 and 50-3S6

Enclosure:

As stated cc w/ encl.: See next page

l Edwin 1. Hatch Nuclear Plant ec:

Mr. Ernest L. Blake, Jr. Charles A. Patrizia, Esquire 1 Shaw, Pittman, Potts Paul, Hastings, Janofsky 6 Walker and Trowbridge 10th Floor 2300 N Street, NW. 1299 Penntylvania Ave .us Washington, DC 20037 Washington, DC 20004-9500 Mr. D. M. Crowe Chairman Manager, Licensing Appling County Commissioners Southem Nuclear Operating County Courthouse Compeny, Inc. Baxley, Georgia 31513 P. O. Box 1295 Birmingham, Alabama 35201-1295 Mr. J. D. Woodard Executivo Vice President Resident inspector Southem Nuclear Operating Plant Hatch Company, Inc.

11030 Hatch Parkway ' P. O. Box 1295 Baxley, Georgia 31531 Birmingham, Alabama 352011295 Regional Administrator, Region Il Mr. P. W. Wells U.S. Nuclear Regulatory Commission General Manager, Edwin I. Hatch Atlanta Federal Center Nuclear Plant 61 Forsyth Street, SW, Suite 23T85 Southern NucMar Operating Atlanta, Georgia 30303 Company, Inc.

U.S. Highway 1 North Mr. Charles H. Badger P. O. Box 2010 Office of Planning and Budget Baxley, Georgia 31515 Room 610 270 Washington Street, SW. Mr. R. D. Barker Atlanta, Georgia 30334 Program Manager Fossil & Nuclear Operations Haro'd Reheis, Director Oglethorpe Power Corporation Department of Nc.tural Resources 2100 East Exchange Place 205 Butlar Street, SE., Suite 1252 P. O. Box 1349 Atlanta, Georgia 30334 Tucker, Georgia 30085-1349 Steven M. Jackson Senior Engineer - Power Supply Municipal Electric Authority of Georgia 1470 Riveredge Parkway, NW At'inta, Georgia 30328-4684

1 Request for AdditionalInformation (RAI) on Hatch Individual Plant Examination of External Events (IPEEE)

Fire

1. It is important that the human error probabilities (HEPs) used in the screening phase of the analysis properly resect the potential effects of fire (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 thesa effects 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 intemal events analysis could be optimistic with respect to a fire risk analysis.

Piease identify: (a) the scenarios screened out from further analysis whose quantification involved one or more HEPs,( b) the HEPs (descriptions and numerical values) for each of these scenarios, and (c) how the effects (e.g., smoke, heat, loss of lighting, and poor communication) of the postulated fires on HEPs were treated.

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 failure

• and high probability random equipment failures were identified in the FRSS as poter. cal 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 (MCR)) might lead to potential control systems vulnerabilities. Given a fire in the plant, 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 issue include:

(a) Electricalindependonen of the remote shutdown control systems: Tne primary concern of entrol systems interactions occurs at plants that do not provide independe.u remote shutdown control systems. The electricalindependence of the RSP and the evaluation of the level of indiction and control of remote shutdown control and 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, i

1

2 (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 safe-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 RSP, needs to be assessed. This assessment also needs to include the spurious starting and running of purnps as well as the spurious repoe'Uoning of valves.

(d) Totalloss of system function: The potentic' for totalloss of system function as a result of fire-induced redundant ccmponent failures or electrical distribution system (power source) failure needs to be addressed.

Please describe your remote shutdown capability, including the nature and location of the shetdown station (s), as well as the types of control actions, which can be taken from the remote panel (s). Describe how your procedures provide for transfer of control to the remote station (s). Provide an evaluation of chether 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 inese failures are screened, please provide the basis for the screening). Finally, provide an evaluation of whether spurious actuation of components as a result o~ fire-induced cable faults, hot shorts, or component failures could lead to component damage, a LOCA, or an interfacing systems LOCA prior to taking centrol from the RSP (considering both spurious starting and running of pumps as well as the spurious repositioning of valves).

3. The previous question aadresses the potential for hot shorts due to fires in the MCR.

Fires in other areas of the plant can also result in hot shorts that result in adverse conditions. Hot shorts in control cables can simulate 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. These types of faults might, for example, lead to a LOCA, diversion of flow within various plant systems, deacheading 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 leafng to inapproprise control actions or generation of actuation signals for emergency safeguard features. From the submittal, it cannot be determined to what extent the licensee has considered hot shorts as a failure mode for cuntrol or instrumentation cables, in particular, hot short considerations st.ould 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 been considered, please provide an assessment of how inclusion of potential hot shorts would impact the quantification of fire risk scenarios in the IPEEE.

l

4. The Hatch fire probabalistic risk assessment (PRA) uses two factors to estimate fire-induced component fragilities: the severity and geometric factors. The severity factor is used to estimate the fire-induced damage probabliity d 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 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 tha development of tht fire severity factor and the types and sizes of transient f'res used in the geometric factor evaluations are not described. Furthermore, there is a lack of detail as to the application of these factors and the nonsuppression factor. Please provide (a) this additionalinformation concerning the development of these factors, and (b) the values of the severity, geometric, and nonsuppression factors used in the scenarios analyzed in the detailed analysis.

5. The scieening of propagation pathway boundaries on the basis of combustible contents is 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 ' Methodology for Developing and implementing Alternative Temperature-Time Curves for Testing the Fire Resistance of Barriers for Nuclear Power Plant Applicotions') to allow screening of propagation pathways when the only criterion satisfied is that the estimated fire severity (in hours) is less than 75% of a rated barrier. Please reevaluate the propagation pathways when this criterion is eliminated for these barriers, and assess the associated impact on the results.

6. From the information provided in the submittal, it is not ctear that fire propagation to areas qualitatively W reened was included in the quantitative portions of the PRA. Sirce some fire zones were qualitatively screened even though they contain safety-related equipment, fires initiated in other fire zones that propagate to these zones can result in significantly more damage. Please indicate if fire propagation to qualitatively screened fire zones was considered and if not, provide an evaluation of this impact on the core damage frequency (CDF).

7. Table 4.1-1 in the submittal indicates that fire zones were qualitatively screened on the basis that no scram mechanisms were identified even though safety-related equipment is contained in the zone. Areas screened include switchgear rooms, diesel generator rooms, and service water valve pits. Although a fire may not result in an automatic scram, there is a potential for a manual scram or controlled shutdown initiated by procedu;es or due to technical 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.

8. Insufficient anchorages on electrical cabinets can result in their tipping over during seismic events potentially resulting in seismic-induced fires. The Hatch submittal does not indicate if electrical cabinets were reviewed during the seismic / fire interaction evaluation. Please provide an evaluation of the fire potential from electrical cabinets at both Hatch units during an earthquake.

9. The submittalindicates that some fire areas contain elements of both units. For example, the MCR and cable spreading room appear to be shared by both units. For multi-unit sites, there are three issues of potentiat intorest.

A fire in a shared area might cause a simultaneous trip demand for more than one unit.

This may considerably complicate the response of operators to the tire event, and may create conflicting demands on plant systems, which are shared between units. Thia may include the MCR. Please provide the following relevant information regarding this question: (1) identify all fire areas that are shared between units and the systems / components for euch unit that are housed in each such area, (2) for each shared area that houses importhnt components or syrtems for both units, provide an assessment of the potential for a multi-unit fire scenario to be initiated, (3) for the special case of control rooms s6 sring a common fire area, assess the likelihood of a fire or smoke induced evacuation with subsequent shutdown of both units from RSPs, and (4) provide an assessment of the CDF contribution of any such multi-unit scenarios.

At some sites, the safe shutdown path for a given unit may call for cross-connects to a sister unit in the event cf certain fires. Hence, the fire analysis should include the unavailability of the cross-connect equipment due to outages at the sister unit (e.g.,

routine in service maintenance outages and/or the potential that normally available equipment may be unavailable during extended or refueling outages at the sister unit).

Please provide the following relevant information regarding this question: (1) identify if any fire response cafe shutdown procedures call for unit cross-connects and (2)if any such cross connects are called for, determine the impact on fire CDF if the total unavailability of the sister unit equipment is included in the assessment.

Fire propagation between fire zones containing equipment for one unit to fire zones containing equipment for the other unit can also result in multi-unit fire scenarios.

Hence, the fire assessment for each unit should include analysis of propagation scenarios between fire zones containing equipment Sr the other unit. From the information in the submittal, it is not clear if these types of scenarios are possible and included in the assessment. Please provide an assessment of the CDF contribution of any such multi-unit fire scenarios.

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

There is no RAI in the HFO area. -

Selcmic There is no RAI in the seismic area.

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