ML20236F731

Forwards Request for Addl Info Related to Fire,Seismic & High Wind,Flood & Other External Events Areas of IPEEE Submittal

ML20236F731
Person / Time
Site:	North Anna
Issue date:	06/29/1998
From:	Kalyanam N NRC (Affiliation Not Assigned)
To:	Ohanlon J VIRGINIA POWER (VIRGINIA ELECTRIC & POWER CO.)
References
TAC-M83647, TAC-M83648, NUDOCS 9807020307
Download: ML20236F731 (9)

Text

- _ _ _ _ _ _ _ _ _ _ _ _ _ -.

Juns 29, 1998 f.1r. J. P. O'Hanlon Senior Vice President - Nuclear j-

. Virginia Electric and Power Company 5000 Dominion Boulevard Glen Allen,VA 23060

SUBJECT:

REQUEST FOR ADDITIONAL INFORMATION ON INDIVIDUAL PLANT EXAMINATION OF EXTERNAL EVENTS (IPEEE) SUBWilTTAL - NORTH ANNA POWER STATION, UNITS 1 AND 2 (TAC NOS. M83647 AND M83648)

Dear Mr. O'Hanlon:

Based on the ongoing review of the North Anna IPEEE submittal, the staff has developed the attached reouests for additional information (RAls). The RAls are related to the fire, seismic, and high wind, flood, and other external events (HFO) areas of the IPEEE submittal.

We request that you provide your response within 60 days in conformance with our review schedule. If you have any questions, please call the undersigned at (301) 415-1480.

Sincerely, (Original Signed By)

N. Kalyanam, Project Manager Project Directorate ll-1 Division of Reactor Projects - 1/11 Office of Nuclear Reactor Regulation Docket Nos. 50-338 and 50-339 i

Enclosure:

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Mr. J. P. O'Han!on North Anna Power Station Virginia Electric & Power Company Units 1 and 2 cc:

Mr. J. Jsffrey Lunsford Regional Adminis;rator, Region ll County Administrator U.S. Nuclear Regulatory Commission Louisa County Atlanta Federal Center P.O. Box 160 61 Forsyth St., SW, Suite 23T85 Louisa, Virginia 23093 Atlanta, Georgia 30303 Michael'N. Maupin, Esquire Mr. W. R. Matthews, Manager Hunton and Williams North Anna Power Station Riverfront Plaza, East Tower P. O. Box 402 951 E. Byrd Street Mineral, Virginia 23117 Richmond, Virginia 23219 Mr. R. C. Haag Dr. W. T. Lough U.S. Nuclear Regulatory Commission Virginia State Corporation Atlanta Federal Center Commission 61 Forsyth St., SW, Suite 23T85 Division of Energy Rogulation Atlanta, Georgia 30303 P. O. Box 1197 Richmond, Virginia 23209 Mr. E. S. Grecheck, Manager j

Surry Power Station j

Old Dsminion Electric Cooperative Virginia Electric and Power Company l

4201 Dominion Blvd.

5570 Hog Island Road i

Glen Allen, Virginia 23060 Surry, Virginia 23883 Mr. J. H. McCarthy, Manager Robert B. Strobe, Ni.D., M.P.H.

Nuclear Licensing & Operations State Health Commissioner Support Office of the Commissioner Virginia Electric and Power Company Virginia Department of Health Innsbrook Technical Center P.O. Box 2448 5000 Dominion Blvd.

Richmond, Virginia 23218 Glen Allen, Virginia 23060 Office of the Attorney General Commonwealth of Virginia 900 East Main Street Richmond, Virginia 2321g Senior Resident inspector North Anna Power Station U.S. Nuclear Regulatory Commission 1024 Haley Drive Mineral, Virginia 23117 m

4 4

VIRGINIA Ft FCTRIC AND POWER COMPANY NORTH ANNA POWER STATION. UNITS 1 AND 2 REQUEST FOR ADDITIONAL INFORMATION ON INDIVIDUAL PLANT EXAMINATION OF EXTERNAL EVENTS (IPFFF) SUBMITTAL TAC NOS M83647 AND M83648 SRE:

1.

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, s'nd a discussion of the findings and conclusions. NUP.EG-1407 also requests that evaluation resu!ts 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 !n 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 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:

(a)

Electricalindependence 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 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 1

control power for coitain control circuits as a result of hot shorts and/or blown i

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

(c)

Spurious actuation of components leading to component damage, loss-of coolant i

L accident (LOCA), or interfacing systems LOCA: The spurious actue+ ion of one l

cr more safety-related to safe-shutdown-related components ss.4.esult of fire-L induced cable faults, hot shorts, or component failures leading to e,omponent i

damage, LOCA, or interfacing systems LOCA, prior to taking control from the L

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.

2 (d) fatal 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 how your 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 screen 3d, plaase provide the basis for the screening). Finally, provide an evaluation of whether spurious actuation of componento 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 remote shutdown panc.I (cons,idering both spurious starting and running of pumps as well as the spurious repositioning of valves).

2.

Fires that could affect both units were not considered. The submittalindicates that some fire areas contain elements of both units. For multi-unit sites, there are three issues of potentialinterest. Hence, please answer the following:

(a)

A fire in a shared area might cause a simultaneous trip demand for more than one unit. This may considerably complicate +he respor:se of operators to the fire event, and may create conflicting demands on plant systems which are shared between units. Please provide the following information regarding this issue:

(1) identify all fire areas that are shared between units and the potentially risk important systems / components for each unit that are housed in each such area, (2) for each area identified in (1), provide an assessment of the associated multi-unit fire risk, (3) for the special case of control rooms, assess the likelihood of a fire or smoke-induced evacuation with subsequent shutdown of both units from remote shutdown panels, and (4) provide an assessment of the risk contribution of any such multi-unit scenario.

(b)

At some sites, the safe shutdown path for a given unit may call for cross-connects to a sister unit in the everit of certain fires. Hence, the fire analysis should include the unavailability of the cross-connected 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 issue: (1) indicate whether any fire response safe shutdown procedures call for unit cross-connects, and (2) if any such cross-connects are required, determine the impact on fire risk if the total unavailability I

of the sister unit equipment is included in the assessment.

1 (c)

Propagation of fire, smoke, and suppressants between fire zones containing equipmeret for one unit to fire zones containing equipment for the other unit also i

can result in multi-unit scenarios.' Hence, the fire assessment for each unit l

.should include analyses of scenarios addressing propagation of smoke, fire and suppressants to and from fire zones containing equipment for the other unit.

l l

3 From the information in the submittal, it is not clear if these types of scenarios are possible. Please provide an assessment of the risk contribution of any such multi-unit scenarios.

3.

In general, the fire risk associated with a given compartment is composed of contributions from fixed and transient ignition sources. Neglect of either contribution can lead to an underestimate of the compartment's risk and, in some cases, to improper screening of fire scenarios. Transient fire sources were not considered credible based on examples listed in the Fire induced Vulnerability Evaluation (FIVE) methodology screening section. However, the actual conditions at North Anna Power Station (NAPS) do not conform to the criteria given in the examples in FIVE. For example, flammable and combustible liquids at NAPS can be stored in unapproved containers if proper authorization is obtained. In addition, it is assumed that the North Anna plant inspection, combustible control, and housekeep!rg requirerr. nts eliminate many transient fire sources, i.e., there are no credible errors that could lead to a significant transient-induced fire.. It must be noted that administrative controls are an insufficient basis for eliminating transient combustible fires from consideration.

This can lead to the omission of a potential vulnerability if a compartment contains cables or equipment for all redundant trains of important systems. For NAPS, neglecting transients, in particular, may have impacted the risk contribution for the auxilisry building and switchgear rooms.

For the auxiliary building and switchgear rooms, please quantify the contribution of transient fuel fires to plant core damage frequency (CDF).

4.

In the discussion of the screening analysis on pape 4-9 of the submittal, it is stated that "if redundant shutdown paths are located in the same area but separated according to Appendix R criteria, one path may be failed at a time."

This assumption is not consistent with either the intent of the IPEEE process or the FIVE methodology. Further, according to the comments column of Table 4.5.1-1, eleven compartments were qualitatively screened using criteria that are not part of the FIVE methodology. Eight compartments were screened on the basis that nn independent shutdown path would remain intact. In addition, three

~

y compartments were screened based on the normal method of plant shutdown j

being available. The areas screened included the turbine building, the Uc,it 1

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turbine-driven auxiliary feedwater (AFW) pump room, the Unit 1 motor-driven AFW pump room, and the Unit 1/ Unit 2 emergency diesel generator (EDG)

. areas. As a result, these areas / compartments and other potentially high hazard areas were not analyzed in detail to determine the potential effects of fire damage or propagation.

Please quantitatively analyze the turbine building, AFW pump rooms, and plant EDG areas and discuss the resuits. Identify any plant areas or fire scenarios where separation "according to Appendix R criteria" was credited as preventing fire damage ~. For all such areas / scenarios, quantify the risk contribution (either the screening result or CDF) if Appendix R separation is not credited a priorias preventing damage l

1

4 5.

The submittal discusses one possible scenario for fire-induced hot shorts that could lead to a LOCA. From the submittalit can not be determined whether other hot shorts and spurious actuations have been considered as a failure mode for control or instrumentation cables (e.g., the potential for a control room fire to cause hot shorts in motor-operated valves (MOVS) needed for reactor shutdown per NRC Information Notice 92-18). These hot shorts could cause valve damage before the operator transferred control to the auxiliary shutdown panel and render them inoperable.

Hot short considerations should include the treatment of conductor-to-conductor shorts within a given cable. 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 exampio, lead to a 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. For MCR abandonment scenarios, such spurious operations and actions may not be indicated at the auxhiary shutdown panel (s), may not be directly recoverable from remote shutdown locations, or may lead to the loss of remote shutdown capability (e.g. through loss of shutdown panel power sources). 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.

Please discuss to what extent these issues have been considered at NAPS. Of particular interest are potential vulnerabilities of (1) high head safety injection (HHSI), and low head safety injection (LHSI) systems to spurious opening signals, and (2) safe shutdown MOVs to power being applied to a stalled motor, if those, or other important systems, have not been considered, please provide an assessment of how inclusion of potential hot shorts and spurious actuations would impac! the quantification of fire CDF in the IPEEE.

6.

On page 4-20 of the submittal it is stated that "If the operator must take action in an area affected by a fire, then local recovery was not allowed until the fire was extraguished. Typically 30 minutes was added to the median response time Tm unless specific analysis showed that the fire was extinguished in less time."

Crediting recovery actions in the fire effected area is inconsistent with accepted fire risk assessment practice, and may have resulted in optimistic risk estimates.

Equipment in the fire-affected area may not be recoverable, and even if equipment tr,ight be recoverable, the timing of such recovery as stated in the submittal appears optimistic.

Please identify each scenario where operator recovery actions within the fire-affected compartment have been credited. Describe in detail the credited recovery actions for each such scenario. Quantify the contribution to CDF if the in-compartmer,t recovery actions are not credited (i.e., assuming that any recovery actions within the fire-affected area cannot be performed or are not successful).

5 7.

It appears that the North Anna IPEEE fire analysis has assumed that the plant esbles are either IEEE-383 qualified or that they are equivalent to IEEE-383 qualified cables (see, for example, the discussion on pp. 4-17 and 4-18). Given the age of the two North Anna units, this assumption appears optimistic and was not substantiated. The IEEE-383 standard is primarily a severe accident equipment qualification standard that also includes a name spread test. In a fire context, it might erroneously be assumed that only the flame spread pass # ail status of a cable is of interest. In practice, the recommended cable damage thresholds reflect the more robust thermal performance that might be assumed for IEEE-383 qualified cables based on the demonstrated severe accident performance as compared to unqualified cables whose thermal performance has not been demonstrated (as per FIVE, the assumed damage thresholds are 700*F and 1 BTU /ft /s for qualified cables and 425'F and 0.5 BTU /ft /S for 8

2 unqualified). Hence, the assumptions of cables being equivalent to IEEE-383 cables should include consideration of both the implied flammability properties (ignition temperature, rate of flame spread, anr1 likelihood of self-ignited fires) and thermal damage thresholds.

Please provide a specific basis for the assumption that the cables at North Anna are either IEEE-383 qualified or equivalent to IEEE-383 qualified cables. Include in the response specific consideration of both the flammability properties (ignition, flame spread, and likelihood of self-ignited fires) and the thermal damage properties. Altematively, provide an assessment of the impact on the j

arvalysis results (CDF) if it is assumed that the cables are not IEEE-383 i

equivalent and the flammability and/or appropriate non-qualified cables damage properties are used.

8.

While extensive, the North Anna containment evaluation did not consider two important issues. First, residual heat removal (RHR) pumps are located in 1

containment at North Anna. As noted in the FIVE methodology, an analysis of H

containment should be performed if redundant trains of critical equipment might be susceptible to damage from a single fire. The possible effects of a fire involving the RHR pumps was not discussed. Second, ThermoLag is used in j

containment to separate safe shutdown equipment. The submittal does not discuss the vulnerability of containment equipment protected by this material (see information Notice 95-27).

Please determine the CDF contribution of potential fires which could impact the RHR pumps located in containment. For these and other fires which could occur in containment, assess the CDF contribution if the ThermoLag barriere are not 4

credited.

SEISMIC:

1.'

Table 3.2-1 of the IPEEE submittal lists all mechanical and electrical equipment for which a high confidence-low probability of failure (HCLPF) of less than 0.3g peak ground acceleration (PGA) was calculated as well as the mode of failure. Some of these are

6 critical components in the success paths such as the emergency condensate storage tanks (ECST) which are used on both transient and small LOCA success paths for the makeup of steam generawr feedwater inventory in the se.condary loops, and the refueling water storage tank (RWST) tanks which are used for coolant inventory control 1

in the small LOCA success pathi Please provide:

{

(a)

A spectral comparison between the review level earthquake (RLE) spectral inputs and the original design basis spectra; please identify whether these tanks are founded on rock or soil.

(b)

HCLPF capacity calculations for the ECST tanks and RWST tanks.

HIGH WIND. FLOOD. AND OTHER EXTERNAL EVENTS (HFOh 1.

Generic lasue (GI)-103, " Design for Probable Maximum Precipitation (PMP)," was addressed with a qualitative discussion, but there was no estimate of the revised PMP.

Please provide the revised PMP and quantify its effects on flooding and roof ponding.

2.

Section 2.5 of NUREG-1407 refers to NRC's current criteria (NUREG/CR-5042,

" Evaluation of External Hazards to Nuclear Power Plants in the United States,"

December 1987) on various accidents related to transportation. in particular, Sections 6.7 and 6.8 of NUREG/CR-5042 describe railroad and truck accidents involving either the detonation or release of hazardous materials transported.

Please discuss your findings on transportation accidents involving either the detonation or release of hazardous materials transported on nearby highways and railroads.

3.

Section 5.2.2 of NUREG-1407 mentions that all licensees should review the site for any significant changes since the operating license was issued including onsite storage or other activities involving hazardcas :natorials.

Please provide your findings on accidents involving a release of toxic chemicals stored onsite.

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