ML20195C660

Forwards Response to NRC 990216 RAI Re Summary Rept of USI A-46 Program

ML20195C660
Person / Time
Site:	North Anna
Issue date:	06/01/1999
From:	Hartz L VIRGINIA POWER (VIRGINIA ELECTRIC & POWER CO.)
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
REF-GTECI-A-46, REF-GTECI-SC, TASK-A-46, TASK-OR 99-101, NUDOCS 9906080251
Download: ML20195C660 (9)

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VIEINIA Eucernic ann Powica CmtI%NY RicM10NID, VHUHNI A 232(,1 l

June 1, 1999 l

U.S. Nuclear Re0ulatory Commission Serial No.99-101 Attention: Document Control Desk NL&OS/ETS R0 Washington, D.C. 20555 Docket Nos. 50-338 50-339 License Nos. NPF-4 NPF-7 Gentlemen:

VIRGINIA ELECTRIC AND POWER COMPANY NORTH ANNA POWER STATION UNITS 1 AND 2 REQUEST FOR ADDITIONAL INFORMATION ON i

SUMMARY

REPORT ON USI A-46 PROGRAM in a May 27, 1997 letter (Serial No.97-246), Virginia Electric and Power Company provided a summary report of the USl A-46 program, " Verification of Seismic Adequacy of Mechanical and Electrical Equipment," at North Anna Power Station Units 1 and 2.

In a February 3,1999 letter, the staff requested additional information to complete their review of our A-46 program submittal. The NRC staff's questions were formally transmitted to Virginia Electric and Power Company in a February 16,1999 letter. The attachment to this letter provides our response to the staffs questions.

If you need any additional information, please contact us.

Very truly yours, L. N. Hartz Vice President - Nuclear Engineering and Services Commitments made in this letter:

1. An Administrative Procedure is being prepared to address future hcusekeeping concerns'in safety significant areas of the plant, including the control room. The procedure is scheduled for implementation at the Station by the end of 1999.

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Attachment

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9906080251 990601 PDR ADOCK 05000338 P Pog

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i cc: U.S. Nuclear Regulatory Commission

• Region II Atlanta Federal Center 61 Forsyth Street, SW Suite 23T85 Atlanta, Georgia 30303 -

Mr. M. J. Morgan NRC Senior Resident Inspector North Anna Power Station I

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, 1 ATTACHMENT LETTER SERIAL NO,99-101 Response to Request for Additional Information (RAI) in NRC Letter dated February.

16,1999 Regarding Virginia Power's Submittal dated May 27,1997 on the Verification of Seismic Adequacy of Mechanical and Electrical Equipment l

Unresolved Safety issue (USI) A-46 i

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North Anna Power Station Units 1 and 2 Docket Numbers 50-338/339

Request a: 1 i

• Describe what reviews were performed to determine if any local operator actions required to safely shut down the reactor (i.e. implement the safe shutdown equipment list (SSEL) could be affected by potentially adverse environmental conditions (such as loss of lighting, excessive heat or humidity, or in-plant barriers) resulting from the seismic event. Describe how staffing was evaluated and describe the reviews which were conducted to ensure operators had adequate time and resources to respond to such events.

Virginia Power Response:

In selecting the method (s) to be used to shutdown the plant following a design basis earthquake (DBE), a conscious effort was made to utilize the processes and i components relied upon in existing operating procedures. The potential for loss of instrument air, HVAC, and electrical loads (such as lighting) were anticipated, and a path / process for shutdown was selected which would work for such contingencies. The Appendix R report was reviewed as part of the process of developing the SSEL since it 4 was recognized that many of the same operational limitations may be present following a seismic event.

Support was considered for remote operating equipment and performing line-ups on an as-needed basis. It was determined that the necessary supplies (such as portable lights, respirators, ice vests, etc.) would be available to perform these evolutions in accordance with approved procedures under adverse operating environmental conditions. In addition, the necessary hardware needed to block air operated valves, or to cycle them by means of connection to portable air bottles, was confirmed to be ,

available, in the event such actions should be required. '

Adequate instrumentation was verified to be on the SSEL to permit a timely evaluation i of the following status after a seismic event: l the condition of the plant; the equipment available for continued operations, based on the extent of the damage to the instrument air system; and, the electrical buses that may be lost.

Following an assessment of plant conditions and the determination of the need for dispatching operators throughout the plant, a decision would be made whether additional operators would be called in to supplement the on-shift staffing.

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Request b.: j

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As part of the licensee's review, were any main control room (MCR) structures which could impact the operator's ability to respond to the seismic event identified? Such items might include but are not limited to: MCR ceiling tiles, non-bolted cabinets, and non-restrained pieces of equipment (i.e., computer keyboards, monitors, stands, printers, etc.). Describe how each of these potential sources c? interactions has been evaluated and describe the schedule for implementation of the final resolutions.

Virginia Power Response:

The control room and associated structures and safe shutdown equipment located in the control room, as well as the ability of the operators to respond to safely shutdown the reactor following a safe shutdown earthquake (SSE), were evaluated for impact on the ability to safely shutdown the plant. The main control boards, the benchboards, cable tray and conduits, and other safe shutdown equipment located in the control room were evaluated as part of North Anna's A-46 review.

The method used for evaluating potential sources of seismic spatial interaction is described in Generic implementation Procedure, Revision 2 (GIP-2), Part il, Section 4.5 and Appendix D. Our review concluded that the control room structures and components satisfied the GIP screening criteria, and they are well anchored with sufficient margins to withstand a SSE. Two exceptions to this are identified in our summary report transmitted to the NRC in May 1997 and in our response to NRC, dated April 1,1999 (Serial No.99-027). They are:

. A few cabinets containing essential relays in the Control Room are not connected to the adjacent cabinets. An evaluation of the potential of relay chatter is in progress and if necessary, these cabinets will be bolted together in  ;

the side-to-side direction to prevent any interaction. These cabinets are, i however, well braced at the back. l

. The diffuser panels of the control room ceiling represent a potential source of interaction. The control room ceiling light diffuser panels will be further reviewed and, if required, they will be tied together to the tee frames to prevent their falling i during a SSE.

l As stated in our May 1997 summary report, the schedule for completing these  ;

evaluations / modifications is the end of the second refueling outage for Unit 1 from the time of the submittal of the summary report. This outage is currently scheduled to commence in March 2000.

In addition, an Administrative Procedure is being prepared to address future housekeeping concerns in safety significant areas of the plant, including the control room. The procedure is scheduled for implementation at the Station by the end of 1999.

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Request c.:

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' Describe what reviews were performed to determine if any local operator actions were required to reposition " bad actor relays." For any such activities describe 4 how adverse environmental conditions (such as loss of lighting, excessive heat or humidity, or in-plant barriers) resulting from the seismic event were analyzed and dispositioned. Describe how staffing was evaluated and describe the reviews that were conducted to ensure operators had adequate time and resources to respond to such events.

Virginia Power Response:

No " bad actor" relays were identified during the USI A-46 relay review for North Anna Units 1 and 2. However, a few groups of relays were screened based upon the use of ,

operator action. This screening was based on the methodology stated in section 6.2 of )

GlP-2. This screening process does not require relays, whose malfunction is acceptable, to be seismically rugged or evaluated for seismic functionality. Therefore, a l seismic evaluation was not performed for these relays. As identified in the relay review I report (Appendix B of the USI A-46 summary report for North Anna, May 1997), l operator action was relied upon in the following cases:

. Boric Acid . Tank Heaters (1-CH-H-6A, B; 1-CH-H-7A, B; and 1-CH-H-0A, B).

Contact chatter or an undervoltage condition on the emergency bus wiil turn the heater off. The operator must reset the heater after chatter has stopped, or after the undervoltage condition has been remedied. The operator accomplishes the reset by means of a pushbutton located in the electrical penetration area. The heaters must be reset following a loss of offsite power, and the operators are familiar with this procedure. In addition, Low Boric Acid Tank temperature is annunciated in the main control. Since the operators have low temperature indication and an accessible reset capability, operator action is considered acceptable.

. Control Room / Relay Room Chillers (1-HV-E-4A, 4B, 4C; 2-HV-E-4A, 4B, 4C).

Contact chatter may cause the chillers to turn off Local switch closure is required to restart the chiller. Operators have indication of chiller status in the control room and i will be aware of high control room temperature. Therefore, operator action, which l will nct be required immediately following the earthquake, is considereo acceptable.

. Control Room Air Conditioners (1-HV-AC-1, 2; 2-HV-AC-8, 9). Contacts are interlocks from the Halon 1301 Fire Suppression System. Contact chatter may shut down the air conditioning units. Local switch closure is required to restart the air conditioners. Operators have indication of air conditioner status in the control room ,

and will be directly aware of high control room temperature. Furthermore, operator action is not required immediately following the earthquake. Therefore, the operator action is considered acceptable.

The required actions related to postulated relay chatter were reviewed against the conditions and requirements specified in EPRI NP-7148, Section 3.5.2, regardhg Page 3 of 6

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operator actions. These criteria require that there be sufficient time, indication, access, and procedures available to reset or restore the systems controlled by these relays and I

' that these actions can be carried out by the operations staff along with their other duties. Based on a review of the above cases and the types of situations where operator action might be used, no significant increase in operator burden is considered likely. No changes to current operator procedures were required.

In order to validate the operator's ability to access equipment to perform local actions, engineering and operations personnel walked down the associated paths. The walkdown considered the building structure ruggedness, anchorage of the equipment inside the building structures, potential seismic interactions, and other possible adverse effects due to a seismic event. We conclude that no adverse environmental conditions will impede operator access for the above scenarios following a safe shutdown ,

earthquake. l l

Request d.:

Describe shich of the operator actions associated with resetting SSEL equipment affected by postulated relay chatter are considered to be routine and consistent with the skill of the craft. If not considered skill of the craft, what training and operational aids were developed to ensure the operators will perform the actions required to reset affected equipment?

Virginia Power Response:

Abnormal Procedure 0-AP-36 provides guidance for required actions in the event of a valid seismic event. As discussed in the response to Request c., required actions related to postulated relay chatter are within the scope of expected operator activities, concistent with the skill and training required of operators, and addressed in existing procedures. Therefore, development of specific training and operational aids was not considered necessary.

Request e.:

Assume the alarms associated with " bad actor relays" annunciate during the seismic event. Do the operators have to respond to those annunciators and review the annunciator response procedures associated with them for potential action? How would those additional actions impact the operator's ability to implement the Normal, Abnormal, and Emergency Operating Procedures required to place the reactor in a safe shutdown condition?

Virginia Power Response:

As described in EPRI Report NP-7148, Section 3.5.3, following an earthquake that causes the turbine to trip and the reactor to scram, 50 to 100 or more alarms are Page 4 of 6

expected to annunciate than due to a normal plant trip. In addition to this large number of alarms, there may be several earthquake-induced, spurious alarms resulting from

' such' events as water sloshing in tanks, oil sloshing in transformers, actuation of vibration protective instrumentation on rotating' equipment, and - contact chatter of

~ relays. When these additional alarms occur, the operator will clearly be' aware that the plant has . tripped. Plant procedures and operator training require that operators respond to the turbine trip and reactor scram by confirming the scram and trip and checking important levels, temperatures, pressures, flows, and electrical switching resulting from associated power transfers. These confirmatory checks will take more than a' minute to complete, during which time the operators will not be able to respond to specific alarms because they will be preoccupied performing these checks. The earthquake motion is assumed to last less than a minute and therefore, the causes of the spurious alarms will have gone away during this period while the operators are responding to the plant trip. As noted in our response to request d, Abnormal  !

Procedure 0-AP-36 provides guidance for required actions in the event of a valid seismic event. Following the seismic event, the operators will immediately evaluate the

' plant's critical parameters and the remaining alarms will be acknowledged ~ and prioritized. Expectations concerning the maintenance of critical parameters during emergency and . ~ abnormal situations have been conveyed by Administrative Procedures.

The issue of spurious alarms was generically addressed by SQUG as summarized in

' EPRI NP-7148, Section 3.5.3 (page 3-12) where the following conclusion was reached:

I "Accordingly, there appears to be no reasonable bases or evidence which would suggest that spurious alarms resulting from an earthquake may lead to abnormal operator responses. Therefore, special operating procedures or relay evaluation i actions to address potential spurious alarms are not considered warranted and relays affecting alarms need not be seismically adequate."

The NRC staff accepted the relay functionality review procedure summarized in GIP-2 and described in detail in EPRI NP-7148 (including the above conclusion) in Supplemental Safety Evaluation Report No. 2 on GIP-2. We consider our alarm annunicator and response to be enveloped by the generic evaluation described in EPRI NP-7148.

Request f.:

To the extent that Normal, Abnormal, and Emergency Operating Procedures were modified to provide plant staff with additional guidance an mitigating the A-46 Seismic Event, describe what training was required and provided to the licensed operators, non-licensed operators, and other plant staff required to respond to such events.

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Virginia Power Response:

Since it is assumed that there are no accidents (LOCA, HELB, etc.) or abnormal conditions (floods, high winds, fires, sabotage, etc.) to contend with at the same time that the plant is being shut down as a result of a seismic event, the selection of equipment for the SSEL was straightforward. For the worst case scenario, it was j assumed that instrument air may not be available. Reliance exclusively on on-site )

power sources (the diesels and batteries) was also assumed. Also, the decision was made to take the units to cold shutdown conditions, rather than maintaining them in hot shutdown conditions. This approach resulted in the inclusion of components of the Residual Heat Removal (RHR) System on the SSEL.

Procedures (normal and atnormal) existed for shutting down the units under these conditions, in compiling the SSEL, the approach used was to credit the equipment j specified in existing procedures and not to develop new approaches for bringing the units to safe shutdown conditions. Operations was involved during the development and finalization of the SSEL to assure that the equipment credited was consistent with operating procedures and that the necessary instrumentation to monitor the process was included on the SSEL.

Since it was not necessary to modify operating procedures to address the mitigation of l an A-46 seismic event, there was no need to provide specific training on A-46 l generated procedural changes.

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