ML18039A386

Responds to 980320 RAI Re GL 87-02,Suppl 1, Verification of Seismic Adequacy of Mechanical & Electrical Equipment in Operating Reactors,Unresolved Safety Issue (USI) A-46

ML18039A386
Person / Time
Site:	Browns Ferry
Issue date:	06/11/1998
From:	Abney T TENNESSEE VALLEY AUTHORITY
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
REF-GTECI-A-46, REF-GTECI-SC, TASK-A-46, TASK-OR GL-87-02, GL-87-2, TAC-M69431, TAC-M69432, NUDOCS 9806170065
Download: ML18039A386 (26)

Text

CATEGORY 1 REGULATO INFORMATION DISTRIBUTION STEM (RIDS)

ACCESSION NBR:9806170065 DOC.DATE: 98/06/11 NOTARIZED: NO DOCKET I FACIL:50-26( Browns Ferry Nuclear Power Station, Unit 2, Tennessee 05000260 50-296 'rowns Ferry Nuclear Power Station, Unit 3, Tennessee 05000296 AUTH.NAME AUTHOR AFFILIATION ABNEY,T.E.

Tennessee Valley Authority RECIP.NAME RECIPIENT AFFILIATION Document Control Branch (Document Control Desk)

SUBJECT:

Responds to 980320 RAI re GL 87-02,Suppl 1, "Verification of Seismic Adecpxacy of Mechanical

& Electrical Ecpxipment in Operating Reactors, Unresolved Safety Issue (USI) A-46."

DISTRIBUTION CODE:

A025D COPIES RECEIVED:LTR l ENCL Q SIZE:

jg TITLE: Seismic Qualification of Ecpxipment in Operating Plants

- A-46 NOTES:

GL-87 RECIPIENT ID CODE/NAME OGC/HDS3 DEAGAZIO,A COPIES RECIPIENT LTTR ENCL "'D CODE/NAME 1

1 PD2-3-PD 1

1 COPIES LTTR ENCL 1

1 INTERNAL: ACRS NRR/DE NRR/DE/EMEB NRR/DRCH/HICB, NRR/DSSA/SRXB 1

1 1

1 2

2 1

1 1

1 LE C

B NRR/DRCH/HHFB NRR/DRPE/PDl-3 1

1 1

1 1

1 1

1 EXTERNAL: NRC.PDR 1

1 D

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NOTE TO ALL "RIDSN RECIPIENTS:

PLEASE HELP US TO REDUCE WASTE. TO HAVE YOUR NAME OR ORGANIZATION REMOVED FROM DISTRIBUTION LISTS OR REDUCE THE NUMBER OF COPIES RECEIVED BY YOU OR YOUR ORGANIZATION, CONTACT THE DOCUMENT CONTROL

,DESK (DCD)

ON EXTENSION 415-2083 TOTAL NUMBER OF COPIES REQUIRED:

LTTR 14 ENCL 14

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Tennessee Valley Authority. Post Oflice 8ox 2000, Decatur. Alabama 35609 June ll, 1998 U.S. Nuclear Regulatory Commission ATTN:

Document Control Desk Washington, D AC. 20555 Gentlemen:

In the Matter of Tennessee Valley Authority Docket Nos.

50-260 50-296 BROWNS FERRY NUCLEAR PLANT (BFN)

UNITS 2 AND 3 GENERIC LETTER (GL) 87 02 I SUPPLEMENT 1 r VERIFICATION OF SE ISMIC ADEQUACY OF MECHANICAL AND ELECTRICAL EQUIPMENT IN OPERATING

REACTORS, UNRESOLVED SAFETY ISSUE (USI) A-46

RESPONSE

TO REQUEST FOR ADDITIONAL INFORMATION (TAC NOS M6943 1 I AND M69432)

This letter responds to the NRC March 20,

1998, request for additional information regarding Seismic Evaluation Reports for BFN Units 2 and 3.

NRC requested that TVA provide additional information regarding operator actions associated with bringing the plant to a safe shutdown condition following an earthquake.

t TVA submitted Seismic Evaluation Reports that summarized the results of the USI A-46 and seismic Individual Plant Examination of External Events (IPEEE) programs for BFN Units 2 and 3 by letter dated June 28, 1996.

These reports listed outliers (i.e.,

items of equipment that did not meet the walkdown screening criteria) identified during the seismic evaluations for mechanical and electrical equipment and electrical relays.

9806170065 9806%i POR ADOCX 0500am<0

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U.S. Nuclear Regulatory Commission Page 2

June 11, 1998 The enclosure to this letter provides background information for the BFN A-46 program, lists the specific NRC requests, and corresponding TVA responses..

There are no new commitments contained in this letter.

If you have any questions, please contact me at (256) 729-2636.

S'ncerely T.

E,. Abney Manager of L'si g and Indust y Aff irs Enclosure cc (Enclosure):

Mr. Harold'. Christensen, Branch Chief U. S. Nuclear Regulatory Commission Region II 61 Forsyth Street, S.W.

Suite 23T85

Atlanta, Georgia 30303 NRC Resident Inspector Browns Ferry Nuclear Plant 10833 Shaw Road

Athens, Alabama 35611 Mr. Albert W.

De Agazio, Project Manager U.S. Nuclear Regulatory Commission One White Flint, North 11'555 Rockville Pike Rockville, Maryland 20852

Cl

ENCLOSURE TENNESSEE VALLEY AUTHORITY BROWNS FERRY NUCLEAR PLANT (BFN)

UNITS 2 AND 3 GENERIC LETTER (GL) 87 02 ~

SUPPLEMENT 1 ~ VERIFICATION'F SEISMIC ADEQUACY OF MECHANICAL AND ELECTRICAL EQUIPMENT IN OPERATING REACTORS, UNRESOLVED SAFETY ISSUE

'(USI) A-46 AND GL 88 20 ~

SUPPLEMENT' g'NDIVIDUAL PLANT EXAMINATIONOF EXTERNAL EVENTS,(IPEEE)

FOR SEVERE-ACCIDENT VULNERABILITIES SEISMIC EVALUATION REPORTS REQUEST FOR ADDITIONAL INFORMATION Back round In GL 87-02, NRC established the process'or resolution of USI A-46 and encouraged the affected licensees to participate in a generic program.

Supplement 1 to GL 87-02, required a response that included a commitment to the Generic Implementation Procedure, Revision 2, (GIP-2) prepared by the Seismic Qualification Utility Group (SQUG),

a schedule for implementation of the GIP-2, and submission of a report summarizing the results of the USI A-46 Program.

By letters to NRC dated September 21,

1992, January 19,

1993, and March 19,

1996, TVA committed to implement the GIP-2, including the clarifications, interpretations, and exceptions in the NRC Supplemental Safety Evaluation Report Number Two (SSER-2),

and to communicate to the staff any significant. or programmatic deviations from the GIP-.2 guidance.

For BFN Units 2 and 3, TVA committed,to submit the results of the USI A-46 evaluation by June 28, 1996.

Combined USI A-46 and seismic IPEEE walkdowns were performed in,accordance with the SQUG GIP-2.

Outliers (i.e.,

items of equipment that did not meet the walkdown screening criteria) were identified'uring the seismic evaluations for mechanical and electrical equipment and electrical relays.

Seismic Evaluation and Relay Reports listed the outliers identified during these evaluations.

The Seismic Evaluation Reports for BFN Units 2 and 3 were submitted by TVA letter dated June 28, 1996.

In a letter dated March 20,

1998, the NRC staff identified questions regarding its review of the BFN Units 2 and 3

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Seismic Evaluation Reports.

The NRC questions and the corresponding TVA responses are provided below.

NRC Re est Describe what reviews were performed to determine if any local operator actions required to safely shutdown the reactor, i.e.,

implementation of the safe shutdown equipment list (SSEL),

could be affected by potentially adverse environmental conditions such as but not limited to 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 would have adequate time and resources to respond to such events.

G TVA Res onse The BFN Operations staff performed an extensive review of the SSEL and determined that present procedures (GOIs, OIs,

EOIs, and AOIs) would be adequate to accommodate plant shutdown in the event of a seismic event using equipment identified in the SSEL, with minor changes to O-AOI-100-5, Earthquake.

It was also determined that the required operator actions and time allowed for completion of these actions is well bounded by the Appendix R fire procedures.

Since Operations is adequately staffed to perform the more extensive Appendix R procedures, adequate staffing is available for the actions (e.g., resetting relays) required by the A-46/IPEEE earthquake evaluation.

As described in GIP-2, Part II, Section 3.2.5, the only potential events which must be considered in the USI A-46 program are a safe shutdown earthquake (SSE) and loss of off-site power (LOOP).

The plant operating procedures used to shut down the reactor following a LOOP have previously been validated for local operator actions.

This includes potentially adverse environmental conditions such as loss of lighting and excessive heat and humidity.

Note that the USI A-46 accident scenario (SSE plus LOOP) explicitly excludes loss of coolant accidents (LOCA) and high energy line breaks (HELB).

Therefore, the heat and humidity conditions in the plant are postulated to be equivalent to those in a LOOP scenario.

Abnormal Operating Instruction O-AOI-57-1A, Loss Of Off-Site Power (161 and 500kV)/Station Blackout, will be in progress during this evolution.

Since the earthquake is postulated to only last seconds, the focal point of the scenario will be on the loss of off-site power and its restoration.

Operators are required to know the "Immediate Actions" of E-2

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AOIs from memory.

The first "Immediate Action" is to verify the diesel generators have started and are tied to the respective 4kV shutdown boards..

In Operations'rocedures, the term "VERIFY" means if the required action has not

occurred, the action should be manually taken to make it occur.

A note has been added to alert the operators that if the loss of off-site power is due to, or in conjunction

with, an earthquake, then the relays and breakers for 0he diesel generator (86G and the Field Breaker) may need to be reset to ensure diesel generator operability.

Due to the emphasis placed on restoration of power to the 4kV Shutdown

Boards, and based on Operations'esources and times documented in performance of the Appendix R Safe Shutdown Instructions, it is concluded that the required actions for the A-46/IPEEE earthquake evaluation could be performed adequately.

As part of the TVA review, were any control room structures identified which could impact the operator's ability to respond to the seismic event?

Such items might include but are not limited to:

main control room ceiling tiles, non-bolted cabinets, and non-restrained pieces of equipment, e.g.,

computer keyboards,

monitors, stands,

printers, etc.

Describe how each of these potential sources of interactions has been evaluated and describe the schedule for implementation of the final resolutions.

TVA Res onse Evaluations of the Main Control Room (MCR) ceilings were performed with considerations for the following attributes:

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Adequacy of the main and secondary runners supporting the ceiling fixtures and panels, The main control room ceilings consist of main and secondary runners supporting lightweight diffusers.

The main runners are supported by wire hangers on four foot centers.

Secondary runners are held in place with metal clips.

The diffusers are connected with screws at the corners and at the midpoint of the four-foot length.

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Adequacy of the lateral bracing or tiebacks of the entire ceiling frame to perimeter walls, The MCR ceiling frame is against the perimeter false drop ceiling with no clearance

and, E-3

therefore, no lateral movement.

There is no

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interaction or impact of the ceiling with the perimeter false ceiling.

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Adequacy of the overhead commodities above the light weight ceiling unit, The light fixture frames are hung from the ceiling with rod hangers and laterally braced by rods.

Overhead rigid conduit is typically supported by ceiling-mounted cantilever brackets or Unistrut channel mounted directly to the ceiling.

HVAC duct supports are rod-hung trapezes.

Duct lateral bracing is achieved with structural angles.

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Other attributes that may contribute to significant interaction hazards to the SSEL items below the ceiling, Other overhead commodities such as emergency lights and fire/smoke alarms were evaluated and determined to be adequately supported.

Therefore, MCR ceilings and other overhead features were evaluated by TVA and found to be acceptable for impact on SSEL equipment as well as impact on operator actions.

All control panels in the MCRs are secured to the floor and will not be a hindrance to operator actions.

Temporary equipment, including mobile equipment, is secured in accordance with the Housekeeping/Temporary Equipment Control procedure.

The procedure also identifies the Main Control Rooms as designated zones with Operations personnel identified as the designated zone inspector to,verify housekeeping practices are being maintained.

Many "desktop" items (e.g.,

computer printers) are housed in their own enclosures.

However, there are items such as telephones, computer monitors, etc.,

which are not secured to the desktops.

This condition has been evaluated for impact on control room equipment and found to present no threat.

Further, the control room floor area is relatively

large, and there is a rail (approximately waist height) located at the control panels in the "horseshoe" which would enhance the operators'bility to maneuver and respond to the seismic event.

Therefore, in the unlikely event that an unanchored desktop item would fall to the floor, TVA considers that the operators would not be impeded in performing their tasks.

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In conclusion, based on the above, there are no identified items which have not been addressed and there are no outstanding actions for resolution.

NRC Re uest Describe what reviews were performed to determine if any local operator actions were required to reposition "bad actor relays."

For any such activities describe 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 which were conducted to ensure operators would have adequate time and resources to respond to such events.

TVA Res onse Credit was taken for operator action to reset or restore systems to operational status following a safe shutdown earthquake for the following "bad actor" or "low ruggedness" relays:

Diesel Generator Loss of Field Relays General Electric (GE)

Type CEH.

Operations has made slight adjustments to the Abnormal Operating Instruction O-AOI-100-5, Earthquake, to include the "bad actor" relays.

Sections 4.2.6 (SSEL),

and Section 4.2.7 and 4.2.8, will ensure diesel generator and RMOV Board operation as well as list all identified instrumentation which should withstand seismic activity.

Seismic Safe Shutdown Equipment List (SSEL) identifies equipment which will withstand earthquakes per USI A-46 and IPEEE.

Instruments with the highest reliability are listed below:

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RX WATER LEVEL, 2(3)-LI-3-58A and 58B

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RX PRESSURE, 2(3)-PI-3-74A and 74B

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DRYWELL TEMPERATURE, 2(3)-TI-64-52AB and 2(3)-XR-64-50 DRYWELL PRESSURE~

2 (3 ) PI 64 67B~

1 60A~

2 ( 3 )

XR 64 50 i and 2 (3) -XR-64-159

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TORUS TEMPERATURES 2 ( 3 ) TI 64 1 6 1 and 1 62

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TORUS LEVEL, 2 (3) -LI-64-159A. and 2 (3) -XR-64-159

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RHR SYS I

FLOW, 2 (3) -FI-74-50 and 2 (3) -FI-74-56

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RHR SYS II FLOW, 2(3)-FI-74-64 and 2(3)-FI-74-70

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CS SYS I FLOW, 2 (3) 21

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CS SYS II FLOW, 2 (3) 49 E-5

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RHRSW A3 PUMP AMPS, 0-EI-23-85/2 (3)

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RHRSW B3 PUMP IMPS, 0-EI-23-88/2 (3)

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RHRSW C3 PUMP AMPS, 0-EI-23-91/2 (3)

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RHRSW D3 PUMP AMPS g 0 EI 23 94/2 (3)

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RHR HX 2 (3) A RHRSW

FLOW, 2 (3) -FI-23-36

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RHR HX 2 (3) B RHRSW

FLOW, 2 (3) -FI-23-48

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RHR HX 2 (3) C RHRSW FLOW~

2 (3) FI 23 42

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RHR HX 2 (3) D RHRSW

FLOW, 2 (3) -FI-23-54 IRM A

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2 (3)

NM 92 7/41A IRM B

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2 (3)

NM 92 7/41A The consequences of relay chatter on the diesel generator may result in the diesel being unable to start during the earthquake period (e.g.,

30 seconds) as well as possibly actuating the 86G lockout relays and tripping the exciter field breaker.

Tripping of the 86G lockout relays and the exciter field breakers will necessitate operator action to allow the diesel to start and load.

Resetting the following relays may have to be performed to ensure diesel generator operation:

~ 0-86-082-2547A/GA, DG A DIFF PROTECT LOCKOUT relay on panel 0-LPNL-925-0047A in Diesel Generator Room A

~ 0-86-082-2547B/GB, DG B DIFF PROTECT LOCKOUT relay on panel 0-LPNL-925-0047B in Diesel Generator Room B

~ 0-86-082-2547C/GC, DG C DIFF PROTECT LOCKOUT relay on panel 0-LPNL-925-0047C in Diesel Generator Room C

~ 0-86-082-2547D/GD, DG D DIFF PROTECT LOCKOUT relay on panel 0-LPNL-925-0047D in Diesel Generator Room D

~ 3-86-082-2547A/GA, DG 3A DIFF PROTECT LOCKOUT relay on panel 3-LPNL-925-0047A in Diesel Generator Room 3A

~ 3-86-082-2547B/GB, DG 3B DIFF PROTECT LOCKOUT relay on panel 3-LPNL-925-0047B in Diesel Generator Room 3B

~ 3-86-082-2547C/GC, DG 3C DIFF PROTECT LOCKOUT relay on panel 3-LPNL-925-0047C in Diesel Generator Room 3C

~ 3-86-082-2547D/GD, DG 3D DIFF PROTECT LOCKOUT relay on panel 3-LPNL-925-0047D in Diesel Generator Room 3D E-6

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Also,. a verification of the Exciter Field Breaker for any diesel generator whose lockout relay requires resetting will have to be made to ensure it is closed.

(Located inside the respective diesel generator Electrical Control Cabinet: ).

The following 480V RMOV Boards transfer to alternate power feed:

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480V RMOV Board 2D

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480V RMOV Board 2E

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480V RMOV Board 3D

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480V RMOV Board 3E If the 480V RMOV Boards are not powered or are on their alternate

feeders, the appropriate LPCI Motor Generator (MG) sets will be restarted and placed in service per O-OI-57B.

For the performance of previously mentioned items, the question of adequate lighting during Station Blackout has been addressed in the Appendix R program.

Emergency DC lighting is located and identified throughout the plant and tested quarterly by Fire Operations.

Out of service, or "failed" lighting is repaired on-site, typically within seven days.

Since these are self-contained, battery-powered

units, there is no reason not to expect them to perform their intended function during this scenario.

Operations staffing is in accordance with Current Technical Specifications and Safe Shutdown Instruction requirements.

These requirements ensure there are at least seven emergency responders for the postulated Appendix R fire.

Emergency responders have certain time-critical tasks to accomplish under extreme circumstances.

In that these times have been met in drills, and it is believed safe shutdown actions for the earthquake and loss of off-site power are bounded by Appendix R, it is reasonable to assume the tasks Operations has to perform in this scenario can be accomplished effectively.

As described in GIP-2, Part II, Section 3.2.5, the only potential events which must be considered in the USI A-46 program are a safe shutdown earthquake (SSE) and loss of off-site power (LOOP).

The plant operating procedures used to shut down the reactor following a LOOP have previously been validated for local operator actions.

This includes potentially adverse environmental conditions such as loss of lighting and excessive heat and humidity.

Note that the USI A-46 accident scenario (SSE and LOOP) explicitly exclude loss of coolant accidents (LOCA) and high energy line breaks (HELB).

Therefore, the heat and humidity conditions in the plant are postulated to be equivalent to those in a LOOP scenario.

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Describe which 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, what training and operator aids were developed to ensure the operators will perform the actions required to reset affected equipment.

TVA Res onse Resetting of relays which may have tripped as a result of a Safe Shutdown Earthquake is consistent with the skill and training required for BFN operators.

Resetting these relays is an activity which is included in the scope of the expected operator actions contained in Operating Instructions, Abnormal Operating Instructions, and Emergency Operating Instructions.

These type of actions (resetting relays) are also a part of the skills expected for day-to-day activities of an operator.

Operations personnel are also involved in functional testing of electrical boards which consists of verifying the required actions and resetting relays.

Also, both licensed and non-licensed requalification training includes training for the Earthquake and the Loss of Off-Site Power Abnormal Operating Instructions.

NRC Re est Assume the alarms associated with "bad actor relays" are expected to 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 operators'bility to implement the Normal, Abnormal, and Emergency Operating Procedures required to place the reactor in a safe shutdown condition?

TVA Res onse As described in EPRI Report NP-7148, Section 3.5.3, following an earthquake which causes the turbine to trip and the reactor to scram, 50 to 100 or more alarms are expected to annunciate.

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 E-8

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of relays.

When the avalanche of alarms occurs, 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 go through during which time the operators will be busy making these checks and not responding to specific alarms.

The earthquake motion 'is assumed to last less than a minute and the causes of the spurious alarms will have abated during this period while the operators are responding to the plant trip.

The NRC staff and SQUG representatives discussed this topic in detail, including discussions held at a meeting on August 3,

1988, where this was a primary topic of discussion.

The results of that evaluation and review are summarized in EPRI NP-7148, Section 3.5.3 where the following conclusion is reached.

"Accordingly, there appear 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 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.

Therefore, TVA does not consider it necessary to perform additional reviews of the effect spurious

alarms, caused by "low ruggedness" relays or other causes, as a result of a seismic event.

Procedures for Loss of Off-Site Power, O-AOI-57-1A, and Earthquake, O-AOI-100-5, will be performed in conjunction with the Emergency Operating Instructions (EOIs) for this postulated scenario.

These instructions are fully compatible with EOI usage and are routinely included in license training.

For thi.s scenario, one of the expected actions is to assign a designated licensed operator to the loss of off-site power procedure.

This licensed operator performs specific tasks, independent of alarms, to restore power to the 4kV shutdown boards and the 120-volt AC Reactor Protection System.

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To the extent that Normal, Abnormal, and Emergency Operating Procedures were modified to provide plant staff with additional guidance on 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.

TVA Res onse As stated

above, Abnormal Operating Instructions were revised.

Abnormal Operating Instructions O-AOI-57-1A, and O-AOI-100-5, were revised to include the SSEL list and to provide the operator with the required information needed to mitigate the loss of off-site power in conjunction with the earthquake.

Normal Operating Instructions were referred to as a means of re-starting and loading the diesel generators and the Low Pressure Coolant Injection MG sets for the RMOV Boards.

Training for these revisions is conducted in two different manners.

First, the procedure changes are issued in the operator (both licensed and non-licensed) required reading program, which the operator reads and provides a

signature attesting to his/her knowledge of the material.

Second, the Operations staff will normally review the procedures in class such that questions may be asked and items can be walked down in the plant if desired.

There is no specific training for "other plant staff" listed in the NRC Request.

However, Radiological Emergency Preparedness (REP) teams are made up of designated plant staff from multiple disciplines (electrical, maintenance, engineering, etc.).

These teams meet in the Technical Support Center (TSC) during events such as these, and include Senior Reactor Operators which have been trained on, and are familiar with, these types of procedures.

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