Text

Proposed Tech Specs for Temporary Extension to 250 Volt Dc Control Power Supply Sys AOT
	ML18037A876
Person / Time
Site:	Browns Ferry
Issue date:	05/11/1994
From:	; TENNESSEE VALLEY AUTHORITY
To:	;
Shared Package
ML18037A875	List: ML18037A874; ML18037A876;
References
	NUDOCS 9405170108
	Download: ML18037A876 (67)
	v • d • e

ENCLOSURE 2

TENNESSEE VALLEY AUTHORITY BROWNS FERRY NUCLEAR PLANT (BFN)

UNIT 2 PROPOSED TEMPORARY TECHN1CAL SPECIFICATION (TS)

CHANGE TS-347T MARKED PAGES I'FFECTED PAGE LIST 3.9/4.9-10a (added to TS) 3.9/4.9-11 3.9/4.9-6 II MARKED PAGES See attached.

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SURVE L CE RE UIR HTS 3.9.B 0

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8. From and after the date that one of the 250-V shutdown board batteries and/or its associated battery board is found to be inoperable for any reason, continued REACTOR POWER OPERATION is permissible during the succeeding five days in accordance with 3.9.B.7 except as noted in 3.9.B.S.a, b, and c below:

a.

For the purpose of shutdown board battery and component replacement

only, REACTOR POWER OPERATION is permissible for the succeeding forty-five (45) days providing:

1.

Only one of the shutdown board 'batteries and associated components is being replaced at a time.

2.

All components normally supplied from the shutdown board battery which is being replaced are fed from its alternate source.

3.

Units 1 and 3 are defueled.

b.

NRC notification for 3.9.B.7 is not required for shutdown board battery and component replacement.

c.

Resumption of REACTOR POWER OPERATION is permissible following a shutdown while shutdown board battery and component replacements are in progress.

From January 1, 1995, to December 31,

1995, the provisions of Specification 3.9.B.S on this page will apply while modifications are being performed on t

the shutdown board batteries and/or their associated battery boards.

BFN 3.9/4.9-10a Unit 2

NO%I'8 1988 LXMITIHG COHDITIOHS FOR OPERATXOH SURVEILLAHCE REQVIREMEHTS 3.9.B O

Kauimaat rom and after the date that one of the 250-V shutdown board batteries and/or its associated battery board is found to be XHOPERABLE for my t

reason, continued REACTOR POWER OPERATIOH is permissible during the succeeding five days in accordance vith 3.9.B.7.

9. When one division of the logic system is IHOPERABLE, continued REACTOR POWER OPERATIOH is permissible under this condition for seven days, provided the CSCS requirements listed in Specification 3.9.B.3 are

'atisfied.

The HRC shall be notified vithin 24 hours2.777778e-4 days 0.00667 hours 3.968254e-5 weeks 9.132e-6 months of the

. situation, the precautions to be taken during this period, and the plans to return the failed component to an OPERABLE state.

10. (deleted) ll. The folloving limiting conditions for operation exist for the undervoltage relays vhich start the diesel generators on the 4-kV shutdown boards.

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S ste 3.9.A.3. (Cont'd) d.

The 480-V shutdown boards 2A and 2B are energized.

e.

The units 1 and 2 diesel auxiliary boards are energized.

f.

Loss of voltage and degraded voltage relays OPERABLE on 4-kV shutdown boards A, B, C, and D.

g.

Shutdown buses 1 and 2

energized.

h.

The 480-V reactor motor-operated valve (RMOV) boards 2D & 2E are energized, with motor-generator (mg) sets 2DH, 2DA, 2EN, and 2EA in service.

4.

The three 250-V unit batteries, the four shutdown board batteries, a battery charger for each battery, and associate~battery boards are OPERABLE~

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Undervoltage Relays a.

(Deleted) b.

Once every 18 months, the conditions under which the loss of voltage and degraded voltage relays are required shall be simulated with an undervoltage on each shutdown board to demonstrate that the associated diesel generator will start.

BFN Unit 2 3.9/4.9-6 AMEHOMEQ'g0. y g g

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ENCLOSURE 3

TENNESSEE VALLEY AUTHORITY BROWNS FERRY NUCLEAR PLANT (BFN)

UNIT 2 PROPOSED TEMPORARY TECHNICAL SPECZFICATZON (TS)

CHANGE TS-347T SUPPORT DOCUMENTATION Conceptual modification schedule.

Battery maintenance history.

Figure 3-1 from FSAR FIGURE 8.6-1a showing 250-volt DC power supply lineup.

Figure 3-2 from FSAR FIGURE 8.6-3 showing 250-volt DC system separation.

Figure 3-3 from FSAR FIGURE 8.6-2b showing 250-volt DC shutdown board control power supply single line diagrams.

Figure 3-4 sketch showing shutdown board control power system physical layout.

SHUTDOWN BOARD CONTROL POWER SUPPLY MODIPICATZONS CONCEPTUAL SCHEDULE Task Name UNIT2 CYCLE 7 REFUEL OUTAGE Start Date 10/1/94 Date 1994 Complete sep oct Nov Dec Jan 11/14/94 1995 FCb M44/

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AUg POWER SUPPLY 3EB MODIFiCATION 10/1/94 11/14/94 TS APPROVALNEED DATE 12/1/94 12/1/94 SURV. AND MAINT.PERIOD 12/15/94 12/31/94 POWER SUPPLY 'A'ODIFICATION SURV. AND MAINT.PERIOD 1/1/95 2/15/95 2/15/95 2/28/95 POWER SUPPLY 'B'ODIFICATION 3/1/95 4/15/95 SURV. AND MAINT.PERIOD 4/15/95 4/30/95 POWER SUPPLY 'O'ODIFICATION 5/1/95 6/15/95 SURV. AND MAINT.PERIOD 6/15/95 6/30/95 POWER SUPPLY 'D'ODIFICATION 7/1/95 8/15/95 Baseline Actual Milestone Note:

The dates and modification sequence shown above are for illustrative purposes only.

MAINTENANCE HISTORY FOR C

& D 3DCU-9 BATTERIES INTRODUCTION The existing shutdown board control power supply batteries and the previous Emergency Diesel Generator (EDG) batteries (the EDG batteries were recently replaced with C

& D type KCR-7 batteries) are the same type with comparable ages.

Therefore, maintenance information has been included for both batteries.

The current shutdown board control power supply batteries'onstruction includes three cells per assembly (or jar).

This requires replacement of three cells even if only one cell has a

problem.

Shutdown Board Battery A 5/22/86 Replaced the following cells: 13/14/15, 46/47/48, 61/62/63.

Replaced interior jumper between cell 60 and 61 Shutdown Board Battery B

5/21/86 11/04/89 12/21/90 Replaced the following cells: 28/29/30, 58/59/60 Replaced the following cells: 1/2/3 Replaced entire battery bank due to low capacity (Replaced bank*with batteries from Watts Bar Nuclear Plant)

Shutdown Board Battery C

5/27/86 5/29/86 6/8/92 3/18/94 Replaced the following cells:

16/17/18 Replaced the following cells:

34/35/36, 70/71/72, 118/119/120 Replaced interior jumper between cell 60 and 61 Replaced the following cells:

43/44/45 Shutdown Board Battery D

12/20/91 Replaced entire battery bank due to low capacity (Replaced with new 3DCU-9 batteries)

Shutdown Board Battery 3EB 4/25/90 Replaced the following cells:

55/56/57 125-volt Diesel Generator A Battery 6/24/92 Replaced the following cells:

10/11/12, 28/29/30 E3-2

MAINTENANCE HISTORY FOR C

& D 3DCU-9 BATTERIES (Continued) 125-volt Diesel Generator B Battery 1/10/85 1/18/92 5/27/92 Replaced the following cells: 52/53/54 Replaced the following cells: 1/2/3, 58/59/60 Replaced the following cells: 7/8/9, 10/11/12, 40/41/42, 49/50/51, 52/53/54 125-volt Diesel Generator C Battery 10/21/88 3/25/89 6/8/92 Replaced the following cells: 31/32/33 Replaced interior jumper between cells 30 and 31 Replaced existing battery bank with new 3DCU-9 batteries 125-volt Diesel Generator D Battery 1/10/85 3/25/88 5/14/92 Replaced cells 58/59/60 for use on EDG A.

Replaced the following cells:

10/11/12, 31/32/33, 43/44/45, 58/59/60 Replaced existing battery. bank with new 3DCU-9 batteries 125-volt Diesel Generator 3A Battery 11/17/87 Replaced the following cells:

31/32/33 125-volt Diesel Generator 3B Battery 1/18/92 Replaced the following cells: 1/2/3, 58/59/60 125-volt Diesel Generator 3C Battery 4/29/92 Replaced the following cells: 1/2/3, 58/59/60 125-volt Diesel Generator 3D Battery 6/2/86 Replaced the following cells:

46/47/48 E3-3

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HISTORY OF BATTERY REPLACEMENT EFFORT 250-VOLT PLANT DC POWER SUPPLY BATTERIES As part of baseline calculation effort for the 250-volt DC systems required for Unit.

3 restart and the need to change batteries as they approach the end of their qualified life, the following plant DC power supply batteries have been replaced:

Unit Battery 1 Previously upgraded from LCUN-29 to LCUN-33 due to end of life prior to Unit 2 restart.

Replacement Date Sept 90 Capacity last test

>1004 Unit Battery 2 Upgraded from LCUN-29 to LCUN-33 due to capacity requirements for multi-'unit operation.

Replacement Date May 93 Capacity last test

>1004 Unit Battery 3 Upgraded from LCUN-29 to LCUN-33 due to capacity requirements for multi-unit operation and end of life.

Replacement Date Mar 93 Capacity last test

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ENCLOSURE 4

TENNESSEE VALLEY AUTHORITY BROWNS FERRY NUCLEAR PLANT (BFN)

UNIT 2 PROPOSED TEMPORARY TECHNICAL SPECIFICATION (TS)

CHANGE TS-347T REVISED PAGES I

AFFECTED PAGE LIST 3.9/4.9-10a (added to TS) 3.9/4.9-11 3.9/4.9-6 II'EVISED PAGES See attached.

4 AUXI IAR E ECT I AL SYSTE LIMITI G CO ITIO S FOR OPERATION SURVEILLA CE RE UIREMENTS 3.9.B 0 eration With Ino erable gguuiment

8. From and after the date that one of the 250-V shutdown board batteries and/or its associated battery board is found to be inoperable for any reason, continued REACTOR POWER OPERATION is permissible during the succeeding five days in accordance with 3.9.B.7 except as noted in 3.9.B.8.a, b,

and c below:

a.

For the purpose of shutdown board battery and component replacement

only, REACTOR POWER OPERATION is permissible for the succeeding forty-five (45) days providing:

1.

Only one of the shutdown board batteries and associated components is being replaced at a time.

2.

All components normally supplied from the shutdown board battery which is being replaced are fed from its alternate source.

3.

Units 1 and 3 are defueled.

b.

NRC notification for 3.9.B.7 is not required for shutdown board battery and component replacement.

c.

Resumption of REACTOR POWER OPERATION is permissible following a shutdown while shutdown board battery and component replacements are in progress.

From January 1, 1995, to December 31, 1995, the provisions of Specification 3.9.B.8 on this page will apply while modifications are being performed on the shutdown board batteries and/or their associated battery boards.

BFN Unit 2 3.9/4.9-10a

4.

AUXILIARYELECTRICAL SYSTE LIMITING CO ITIO S FOR OPERATIO SURVEILLANCE RE UIREMENTS 3.9.B 0 eration With Ino erable

~Eni ment

8'rom and after the date that one of the 250-V shutdown board batteries and/or its associated battery board is found to be INOPERABLE for any

reason, continued REACTOR POWER OPERATION is permissible during the succeeding five days in accordance with 3.9.B.7.

9 ~

When one division of the logic system is INOPERABLE, continued REACTOR POWER OPERATION is permissible under this condition for seven days, provided the CSCS requirements listed in Specification 3.9.B.3 are satisfied.

The NRC shall be notified within 24 hours2.777778e-4 days 0.00667 hours 3.968254e-5 weeks 9.132e-6 months of the situation, the precautions to be taken during this period, and the plans to return the failed component to an OPERABLE state.

10.

(deleted)

The following limiting conditions for operation exist for the undervoltage relays which start the diesel generators on the 4-kV shutdown boards.

From January 1, 1995, to December 31,

1995, the provisions of Specification 3.9.Be8 on page 3.9/4.9-10a will apply while modifications are being performed on the shutdown board batteries and/or their associated battery boards.

BFN Unit 2 PLLIC205/95 3.9/4.9-11

4 A

L AR ELECTRICAL SYSTE LIMITI G CO TIO S

FOR OPERATIO SURVEILLA CE RE UIREME S

3.9.A.

Aux lia Electrical E ui ment 4.9.A.

Auxilia Electrical S stem 3.9.A.3. (Cont'd) d.

The 480-V shutdown boards 2A and 2B are energized.

e.

The units 1 and 2 diesel auxiliary boards are energized.

f.

Loss of voltage and degraded voltage relays OPERABLE on 4-kV shutdown boards A, B, C, and D.

g.

Shutdown buses 1 and 2

energized.

h.

The 480-V reactor motor-operated valve (RMOV) boards 2D & 2E are energized with motor-generator (mg) sets 2DN, 2DA, 2EN, and 2EA in service.

4.

The three 250-V unit batteries, the four shutdown board batteries, a battery charger for each battery, and associated battery boards are OPERABLE.*

4.

Undervoltage Relays a.

(Deleted) b.

Once every 18 months, the conditions under which the loss of voltage and degraded voltage relays are required shall be simulated with an undervoltage on each shutdown board to demonstrate that the associated diesel generator will start.

~Except as specified in 3.9.B.8.c on page 3.9/4.9-10a from January 1, 1995, to December 31, 1995.

BFN Unit 2 3.9/4.9-6

ENCLOSURE 5

TENNESSEE VALLEY AUTHORITY BROWNS FERRY NUCLEAR PLANT (BFN)

UNIT 2 PROPOSED TEMPORARY TECHNICAL SPECIFICATION (TS)

CHANGE TS-347T PROBABILISTIC SAFETY ASSESSMENT 1 '

INTRODUCTION This evaluation documents the change in operational risk at the plant level (change in core damage frequency (CDF)) for a proposed extension of the allowed outage time (AOT) for the Unit 1/2 portion of the 250-volt DC control power supply system.

The proposed extension would be used one time only for each of the power supplies.

The AOT extension will allow the shutdown board control power supply systems to be upgraded while Unit 2 is operating.

This evaluation shows that extending the AOT does not significantly impact plant safety.

2.0 BACKGROUND

Technical Specification (TS 3.9.B.8) specifies an AOT of five days if one of the "250-volt shutdown board batteries and/or its associated battery board" (i.e., 250-volt shutdown board control power supply) is not operable.

TVA proposes to extend the AOT to 45 days in order to perform system upgrades needed for multi-unit operation and to replace the old batteries.

The system upgrades would be performed one at a time.

While the upgrades are in progress, the equipment supplied by each shutdown board control power supply would be powered by alternate sources (see Table 1-1 in Enclosure 1).

Additionally, Units 1 and 3 will remain shutdown and defueled.

3%0 DISCUSSION A one time TS change potentially affects risk since a

failure of a power supply providing both normal and alternate power will impact more equipment.

For example, while modifying shutboard control power supply "A", plant DC power supply "2" would be supplying power to its normal loads and control power for 4160-volt Shutdown Board "A" and 480-volt Shutdown Board "1A".

TVA evaluated five separate

cases, one for each shutdown board control power supply modification.

Each case reflects the proposed system alignment.

The potential impact was evaluated, quantified, compared to the base case (normal alignment),

and then summed to determine the total change in CDF.

A summary of the results are tabulated in Table 5-1.

The details of TVA's analysis,

<<ATTACHMENT 1 TO QIR LMEBFN94007,<<

are included at the end of this enclosure (Note:

The 250-volt shutdown board control power supplies are referred to as

<<250-v shutdown board batteries" and the 250-volt plant DC power supplies are referred to as the "Battery Boards" ).

TVA's evaluation used the BFNQUICK model.

BFNQUICK is identical to the model submitted to NRC with the exception of truncation limits.

The truncation limits were altered slightly to improve quantification time (approximately three and one-half days computer time versus eight, days).

The CDF obtained using BFNQUICK is comparable to the CDF provided in TVA's BFN September 1,

1992, submittal (4.6E-5/year compared to 4.8E-5/year).

3 ~ 1 SHUTDOWN BOARD CONTROL POWER SUPPLY tsAss This case models shutdown board control power supply

<<A<< being out of service for up to 45 days while system modifications are being performed.

Plant DC power supply

<<2<< is supplying its normal loads in addition to control power for 4160-volt Shutdown Board

<<A<< and 480-volt Shutdown Board <<1A<<.

The logic rules were modified as follows:

Failure of plant DC power supply

<<2<< would also fail equipment powered from 4160-volt Shutdown Board

<<A<<

and 480-volt Shutdown Board

<<1A<<.

3 '

SHUTDOWN BOARD CONTROL POWER SUPPLY "Bss This case models shutdown board control power supply

<<B<< being out of service for up to 45 days while system modifications are being performed.

Plant DC power supply

<<2<< is supplying its normal loads in addition to control power for 4160-volt Shutdown Board <<B<<.

Plant DC power supply

<<1<< is supplying its normal loads in addition to control power for 480-volt Shutdown Board

<<2A<<.

The logic rules were modified as follows:

Failure of plant DC power supply

<<2<< would also fail equipment powered from and 4160-volt Shutdown Board <<B<<.

Failure of plant DC power supply

<<1<< would also fail equipment powered from 480-volt Shutdown Board

<<2A<<.

E5-2

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SHUTDOWN BOARD CONTROL POWER SUPPLY s'C" This case models shutdown board control power supply "C" out of service. for up to 45 days while a new battery is installed.

Plant DC power supply "1" is supplying its normal loads in addition to control power for 4160-volt Shutdown Board "C" and plant DC power supply "3" is supplying its normal loads in addition to control power for 480-volt Shutdown Board "1B".

Also, shutdown board control power supply "A" is supplying power for Unit 2 ATWS channel "A" in addition to its normal loads.

The logic rules were modified as follows:

Failure of plant DC power supply "1" would also fail plant DC power supply "3" and equipment powered from 4160-volt Shutdown Board "C" and 480-volt Shutdown Board "1B".

Failure of shutdown board control power supply "A" would also fail Unit 2 ATWS Channel "A".

3 '

SHUTDOWN BOARD CONTROL POWER SUPPLY ssD's This case models shutdown board control power supply "D" out of service for up to 45 days while system modifications are being performed.

Plant DC power. supply "3" is supplying its normal'loads in addition to control power for 4160-volt Shutdown Board "D" and 480-volt Shutdown Board "2B".

Additionally, shutdown board control. power supply "B" is supplying power for Unit 2 ATWS channel "B" in addition to its normal loads.

The logic rules were modified as follows:

Failure of plant DC power supply "3" would also fail equipment powered from 4160-volt Shutdown Board "D" and 480-volt Shutdown Board "2B".

Failure of shutdown board control power supply "B" would also fail Unit 2 ATWS Channel "B".

3.5 SHUTDOWN BOARD CONTROL POWER SUPPLY "3EB" This case models shutdown board control power supply "3EB" out of service for up to 45 days while system modifications are being performed.

Plant DC power supply "1" is supplying its normal loads in addition to control power for 4160-volt Shutdown Board "3EB".

The logic rules were modified as follows:

Failure of plant DC power supply "1" would fail shutdown board control power supply "3EB".

E5-3

4 0

CONCLUSION As shown in the Table 5-1 there is a very small increase in risk (0.3264) associated with the proposed TS change if modifications are performed while Unit 1 and 3 are shutdown and defueled.

From a PSA perspective, the increase in risk to Unit 2 operation is negligible.

This result was expected due to the extreme diversity of the BFN electrical distribution system (e.g. eight EDG's and eight 4160-volt shutdown boards) and the fact that the electrical system was designed to support three unit operation.

Since only Unit 2 is operating during this activity, there is a large excess electrical capacity/capability available.

E5-4

TABLE 5-1 CASE CDF 4/CDF 9~

CHANGE*

BASE 4.6257E-05 N/A N/A SDBCPS

'tA 4.6494E-05 5.12E-03 0.0634 SDBCPS "B" 4 ~ 6765E 05 1 ~ 10E 02 0 ~ 135~o SDBCPS "C"

4.6546E-05 6.25E-03 0.0774 SDBCPS itD 4 '439E 05 3 '3E 03 0 '49~o SDBCPS 3EB 4 ~ 6263E 05 1 ~ 30E 04 0 ~ 002~o TOTAL 0.3264

RESULT MULTIPLIED BY (45/365)

TO REFLECT PROPOSED ALIGNMENT TIME SDBCPS Shutdown board control power supply E5-5

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ATTACHMENT 1 TO QXR LMEBPN94007 A base case consistent with the IPE submittal (Reference

1) is used as a baseline and then five sensitivity cases are modeled and run, each representing the alternate control power alignment for a particular battery replacement.

The base case is represented by model BFNQUICK. It is a model that differs from that used in the IPE submittal only in truncation frequencies.

The basis for using this model is that the run time is significantly less than the run time of the model used for the IPE submittal, while the results differ by a minimal (4.6E-5 vs.

4.8E-5) amount.

For each sensitivity case, the Event Tree logic rules will be modified such that failure of a battery board supplying alternate power fails both the loads it normally provides and the alternate loads it is providing for the battery being'replaced.

In most

cases, this is accomplished by simply ensuring that the batteries which appear second in the Event Tree are assigned the same state (success or failure) as the battery which appears first in the Event Tree.

Battery Boards 1, 2 and 3 (the alternates) have slightly higher unavailabilities than the Shutdown Batteries being replaced and thus, in cases where the Shutdown Batteries appear first in the event tree, their split fraction values were changed to Battery Board unavailabilities.

One should note that the IPE model combines a 4kV Shutdown Board with its associated 480V Shutdown Board.

This causes a modeling complication when the alternate control power for the 4kV board is different than the alternate control power for the associated, 480V Shutdown Board.

As indicated in Table 1, that is the case for 4kV Shutdown Boards B and C.

The solution to this complication is discussed in the "Computation" section.

Table 2 below lists the Top Events relevant to the battery boards.

They are listed in their order of appearance in the Electrical Support Event Trees in BFNQUICK.

The table is used to assist in modeling the various cases.

2 OF 9

ATTACHMENT 1 TO QIR LMEBPN94007 TABLE 2 TOP EVENTS

& CORRESPONDING SHUTDOWN BOARD BATTERY BOARDS TOP EVENT DA DE CORRESPONDING SHUTDOWN BOARD BATTERY BOARDS 250V DC CONTROL POWER FOR 4KV SD BD A AND 480 SD BD 1A UNAVAILABLE 250 V DC CONTROL POWER FOR 4KV SD BD 3EA AND 480 SD BD 3A UNAVAILABLE DC 250 V DC CONTROL POWER FOR 4KV SD BD B AND 480 V SD BD 2A UNAVAILABLE DH 250 V DC CONTROL POWER FOR 4KV SD BD 3ED UNAVAILABLE DB

~

DD 250 V CONTROL POWER FOR SD BD C AND 480 V SD BD 1B UNAVAILABLE 250 V DC CONTROL POWER FOR SD BD D AND 480 V SD BD 2B UNAVAILABLE 250 V DC CONTROL POWER FOR 4KV SD BD 3EC AND 480 V SD BD 3B UNAVAILABLE DF 250 V DC CONTROL POWER FOR 4KV SD BD 3EB UNAVAILABLE ASSUMPTIONS 1.(Specific to Case

3) Battery Board 3 is assumed to fail whenever Battery Board 1 is failed.

This is a simplifying assumption which provides conservative results.

The PRA model that was used as a basis f'r BFNQUICK is that contained in the IPE submittal (Reference 1).

The model vas quantified vith the master frequency file HFF93.

This frequency file is similar to that used for the BFN IPE submittal (BFN7232),

vith minor corrections which vere identified in subsecpxent revievs.

MFF 93 is currently used for all BFN PRA work.

The truncation limits changed for BFNQUICK are listed in Appendix A

3 OF 9

ATTACHMENT 1 TO QZR LMEBPN94007 The control power sources shown in Table 1 are taken from References 2 and 3.

COMPUTATIONS The output for the five cases is contained in Appendix B.

CASE 1 BATTERY BOARD A OUT OF SERVZCE Battery Board (BB) 2 is the alternate control power for both 4kV Shutdown Board (SDB)

A and 480V SDB 1A (Table 1).

Prom Table 2, Top Event DA corresponds to SDB battery A and Top. Event DH corresponds to BB2.

Since DA precedes DH in the Electric power event trees, the revised alignment can be implemented by modifying the logic rules such that DH is successful whenever DA is successful and DH is failed whenever DA i's failed.

Thus the logic rules in the ELECT12 Event Tree were modified by inserting the following two rules prior to the rules for DH2 and DH1:

DHF DA=F DHS -DA=F where DHF = 1.0 was already in the Master Frequency File and DHS 0.0 was added.

An additional change was required because split fractions for DH do not have the same value as equivalent split fractions for DA-Therefore the master frequency file was modified such. that the DA split fractions were set equal to the DH split fractions (DA2=4.4485E-3 and DA1 = 5.0032E-3).

CASE 2 BATTERY BOARD B OUT OF SERVZCE BB2 is the alternate control power for 4kV SDB B and BB1 is the alternate control power for 480V SDB 2A (Table 1).

From Table 2, Top Event DC corresponds to SDB battery B, Top Event DH corresponds to BB2, and Top Event DE corresponds to BB1.

The use of two different batteries for control power creates a unique situation since the 4kV and 480V are modeled as one entity.

In order to try and create a method to "decouple" the control power supplies for the 4kV and 480V board, it was first necessary to determine how the normal control power source (SDB battery B-Modeled as Top Event DC) was modeled.

Top Event AB models the 4kV Shutdown Board B and 480V Shutdown board 2A. It is evaluated under a variety of conditions, but they can be summarized as three cases.

The first is under normal conditions in which power is available from Shutdown Bus 1.

The second case is that the normal power from Bus 1 has been lost and a transfer must be made 4

OF 9

ATTACHMENT 1 TO QZR LMEBFN94007 to an alternate power supply.

The third case is a guaranteed failure, such as a loss of offsite power with the EDG failed.

A key here is that in the second

case, DC control power is required to operate the 4kV breakers.

However, the status of Top Event DC is not yet known when AB is evaluated in the event tree.

Therefore, it is evaluated as if the control power from DC is available.

Subsequent top events which require AB for motive power must then question DC for control power availability.

A component fed from AB and requiring control power from DC will thus fail if DC control power is not available, regardless of the conditions in which AB was asked.

iai Zn order to assess how top event DC was used in subsequent Top I<1 Event logic rules a text file was created from RISKMAN for the following event trees:

ELECT12 ELECT3 SIGL MESUPT HPGTET LPGTET MLOCA2 LLOCA1

[ as.

This text file was then searched for rules referring to "DC".

Table 3 delineates the Top Events using "DC" and describes the changes made to the rules.

The change made for equipment served directly off the 4kV board was to change the DC Control Source to the alternate.

This is also true for 480V equipment, with the additional change that failure of the control power for the 4kV board could also fail the equipment if the 4kV board was required to change position, as in LOSP conditions.

Zn Top Events RBC and PCA, control power was asked under LOSP or loss of the 500kV grid conditions.

For Top Event SL, that is not the case, so 4kV control power was explicitly required for LOSP or Loss of 500kV grid conditions in the logic rule modifications.

5 OF 9

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ATTACHMENT 1 TO QIR LMEBPN94007 above the rules for DG2 and DG1 DGF DE=F DGS

-DE=F.

The selection of DE as the

~gilead" Top event is based on DE appearing first in the Event Trees.

The master frequency file was also modified by inserting split fractions DGS and DBS with a value of 0.0.

CASE 4

BATTERY BOARD D OUT OF SERVICE BB3 is the alternate control power supply for 4kV SDB D and for 480kV SDB 2B, and SDB battery B is the alternate power for Unit 2 ATWS Channel B (Table 1).

The change in the ATWS Channel B power supply from SDB battery D to SDB battery B was modeled analogous to ATWS Channel A in Case 3.

The references to "DD" in the rules for RPS and RPT are replaced with "DC" (see Case 3 for additional details).

The change in control power to 4kV SDB D and 480V SDB 2B from battery D to BB3 was implemented by modifying the logic rules such that Top.Event DG is successful whenever Top Event DD is successful and DG is failed whenever DD is failed.

The following logic rules were placed above DGB in the ELECT3 tree:

DGF DD=F DGS

-DD=F.

The Master frequency File was modified by incorporating a new split fraction DGS with a value of 0.0.

An additional change was required because split fractions for DG do not have the same value as equivalent split fractions for DD.

Therefore the master frequency file was modified such that the DD split fractions were set equal to the DG split fractions (DD2~4.4975E-3 and DA1 =

4. 9311E-3)

~

CASE 5 BATTERY BOARD 3EB OUT OF SERVICE BB3 is the alternate control power supply for 4kV SDB 3EB.

From Table 2, Top Event DF corresponds to SDB 3EB and Top Event DG corresponds,to BB2 (Table 1).

Since DG precedes DF in the Electric power event trees, the revised alignment can be implemented by modifying the logic rules such that DF is successful whenever DG is successful and DF is failed whenever DG is failed.

Thus the logic rules in the ELECT3 Event Tree were modified by inserting the following two rules above the rules for

'DF2 and DFl:

7 OF 9

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ATTACHMENT 1 TO QXR LMEBFN94007 It is planned to perform the first battery changeout on the "3EB" Shutdown Battery.

Since this is the battery has the least impact on risk/safety

(.0024 increase in CDF) any unforeseen problems will be identified and resolved prior to work on the more risk/safety significance batteries.

The above facts, taken in consideration with the:

1.

Proposed compensatory measures.

2.

Increased reliability and capacity of the new batteries and associated equipment.

indicate that the proposed activity is essentially risk neutral and will, following implementation, increase overall plant safety and decrease overall plant risk.

REFERENCES 1 ~

2 ~

3.

4 ~

5.

6.

Tennessee Valley Authority, "Browns Ferry Unit 2 Individual Plant Examination" Revision 0, September 1992.

Electrical Drawing 0-45E709-1 R013 Electrical Drawing 3-45E709-2 R007 Electrical Drawing 2-45E763-13 R005 Browns Ferry Nuclear Plant Technical Specifications, Unit 2, Amendment 221 Browns Ferry Nuclear Plant (BFN) Abbreviated Level I Event Tree Model, B81 940323 802 9

OF 9

ATTACHMENT 1 TO QIR LMEBFN94007 APPENDIX A This appendix provides comparisons between the IPE model (BFNFINAL) and the BFNQUICK model used in this evaluation.

This information contains tables from reference 6,

"Browns Ferry Nuclear Plant (BFN) Abbreviated Level I Event Tree Model".

These tables document the different cutoff frequencies used and the resulting changes in the run times for the two models.

The cutoff frequencies for the top four initiators were not changed for the BFNQUICK model.

As can be seen by examining Table 2.1.1 and Table 2.2.2, the relative rankings for the top four initiators remain the

same, and accounts for approximately 854 of the total CDF.

Since the largest contributor to CDF beyond the top four initiators is less than 24, it is acceptable to use BFNQUICK in the place of the IPE model without affecting overall results or conclusions.

It should be noted that neither BFNQUICK or the BFN IPE submittal model is a QA model.

APPENDIX A 1 OF 3

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E

ATTA&QKENT X TO QXR APPENDIX B This Apppendix contains the output files for the base case and each of the five sensitivity cases.

APPENDXX B 1 OF 7

HQ)EL ~ Name: erhuull;L Initiator Contributions to End State Group:

ALL Total Frequency for the End State Group ~ 4.6257E-OS 14!46:08 07 HAR 1994 Page 1

lnitiatoro ~ ~ ~ ee Frequencyo

~ ~ e e e Unaccountedo

~ ~ ~

LOSP FLTB CIV LOFM LOAC LOCV TTMB TT IOTH ISCRAH L500 RIRU LRCLI SCRAHR HLOCA LLO IOOV LOPA PLRI SLOCA LLO LLS LLC ISLOCA LICA PRFO LUPS IOTV PLOC FL'RBSS BOC ELOCA VLOCA LICB FLPH1 UI VII FLR$2 FLR$3C LIIB LIIA LIB FLR$ 1 LIA 3.2942E.05 4.6469E.06 1.5990E-06 1.3146E-06 7.1232E-07 6.4408E-07 6.1882E-07 6.0401Ee07 4.7678E-07 4.3282E-07 3.5338E-07 2.2703E-07 2.0704E-07 2.0171E.07 1o9990E-07 1,9289E-07 1.8637E-07 1.0481E-07 8.8124E-OS 7.3180E-OS 6.0989E-OS 5.3457E-OS 4.7418E-OS 4.6335 E-OS 4.4355EeoS 4.2983E-OS 3.5032E-08 2e7178E-08 2 0910E-OS 1.8872E-08 1.3692E-OS 9.0715E-09 5 3360Ee09 3.2124E-09 1 1048E-09 6 3798E 10 2.7476E-10 2.5548E-10 2.410SE-10 0.0000E+00 0.0000E+00 0.0000E+00 O.OOOOE+OO 0.0000E+00 5 9235Ee04 4 0029E-05 1.9024Ee04 1.8553E-04 5.0443E-05 4o7247E-04 4.6569E-04 7 7020E-04 4.6409Ee07 8.6799E-04 1.0935E-04 3.0244E-04 4.2139Ee05 1o4018E-04 2 1604Ee06 6.4103E.OS 3 9337E-05 1.9772E-04 3.637SEe04 3.9697E-06 3.6836E-OS 3.4360E.OS 3e2548E-OS 6.4779E-11 1 2993E-05 5.3630E-OS 7 2340E-05 1 3015E-05 Se0200E 05 1.0444Ee06 6.2513E-07 3.1852E-10 3 1188E-05

'1.3377Ee05 3.4484E-OS 5.3M7E-07 4,4431E-07 4.4486E-OS 1 3308E-07 1.4432Ee05 1.4430E-05 1.4434E-OS 2.0MOE-OS 1 4430E-05 APPENDzx s 2 of 7

h+tC4 IIOulO~ AtWl Initiator Contributions to End State Group : ALL Total Frequency for the End State Group ~ 4.6494E-05 14s16:53 07 MAR 1994 Page 1

Initlatoros ~ ~ o ~ Frequency......

UnaccsElted~

~ ~ ~

LOSP FLTB CIV LOFM LOAC LOCV TTMB TT IOTll ISCRAll L500 FMRU LRCM LLD SCRAMR NLOCA IOOV LOPA PLFM SLOCA LLO LLS LLC ISLOCA LICA PRFO LUPS IOTV PLOC FLRB3S BOC ELOCA VLOCA LICB FLPH1 Ul Ul1 FLRB2 FLRB3C LIIB LIIA LIB FLRB1 LIA 3.3089E-05 4.6634E-06 1.6035E-06 1.3230E 06 7.1623E-07 6.4397E-07 6.1822E-07 6.0722E-07 4.7728E-07 4.4806E-07 3.5385E-07 2.3134E-07

2. 0860E-07 2.0404E-07

2. 0339E-07 2.0303E-07 1.8750E-07 1 0680E-07 8.8717E-OS 7.3410E-OS 6.5039E-OS 5.6956E-OS 5 0566E-OS 4.6335E-OB 4.4802E-OS 4.3171 E-OS 3.5425E-OS 2,7465E-OS 2.1070E-OS 1.8912E-OS 1.3727E-OS 9.0773E-09 5 3806E-09 3,2980E-09 1 ~ 1071 E-09 6.4072E-10 2.7674E-10 2.5602E-10 2.4'158E-10 0.0000E+00 0.0000E+00 0.0000E+00 0.0000E+00 0.0000E+00 5.8149E-04 3.8711E-05 1.8358E-04 1 7932E-04 4.8898E-05 4 5855E-04 4.5182E-04 7.4563E-04 4 4769E-07 8.4045E-04 1.0667E-04 2.9377E-04 4.1250E-05 6.1349E-OS 1.3553E-04 2.1033E-06 3.8073E-05 1 9244E-04 3.5316E-04 3.8427E-06 3.5344E-OS 3.2983E-OS 3.1265E-OS 6.4779E-11 1 2657E 05 5 1943E.05 7 0278E-05 1o2666E-05 4.868IE-05 1 0172E-06 6.0529E-07 3.1269E-10 3.0300E-05 1.3033E-05 3.3455E-05 5 2201E-07 4+2966E.07 4.3510E-OS 1.2897E-07 1.4051E-05 1 4050E-05 1.4054E-05 1.981 6E-05 1-4050E-05 APPENDIX B 3 of 7

H(QEL HSfQC bVoeK I Initiator Contributions to End State Group: ALL Total Frequency for the End State Group ~ 4.6765E-05 14:35:34 07 HAR 1994 Page 1

initiator...... Frequency......

Unaccented....

LOSP FLTB CIV LON LOAC TT LOCV TTMB IOTH ISCRAH L500 FMRU SCRAHR LRCM LLO HLOCA IOOV LOPA PLFM SLOCA LLO LLS LLC ISLOCA PRFO LICA LUPS IOTV PLOC FLRB3S BOC ELOCA VLOCA LICB FLPH1 Ul UII FLRB2 FLRB3C LIIB LIIA LIB FLRB1 LIA 3.3133E-05 4.6674E-06 1.6381E-06 1.3529E-06 7.1762E-07 6.?926E-07 6.5992E-07 6.3400E-07 4.7728E-07 4.4955E-07 3.5654E-07 2.3299E-07 2.2364E-07 2 OSSDE-07 2.0313E-07 2.0261E-07 1.8984E-07 1.1765E-07 1,0071E-07 7.3353E-OS 6.4071E-DB 5+6123E-08 4.9800E-OS 4.6335E-OS

. 4.5104E-08 4.4905E-DS 3.5529E-OS 2.?535E-OS 2 3418E-OS 1i88?2E 08 1,3736E-OS 9.0?23E-09 5,3S?9E-09 3.3349E-09 2.2939E-09 6 6860E-10 3.0513E-10 2.5548E-10 2 4108E-10 0 OOODE+00 0.0000E+00 0.000DE+00 0 OODDE+00 0,0000E+00 5.9163E-04 3.99?9E-05 1.9004E-04 1.8532E-04 5,0379E-05 7.6892E"04 4.7195E-04 4,6540E-04 4,628?E-07 8,661 5E-04 1 m0926E-04 3.0193E.04 1 o399?E-04 4o2152E-05 6.3745E-OS 2m154OE-06 3.9240E.05 1a9745E 04 3m6304E-04 3.9599E 06 3e6609E-08 3.4192E-OS 3a23?SE-08 6*47?9E-11 5.3591E-05 1 2990E-05 7.2249E 05 1.2994E-05 5.012?E 05 1.0421 E-06 6.2409E-07 3 1774E-10 3,1149E-05 1 33?3E 05 3.4376E.05 5+385 6E.07 4a4349E.07 4.4540E 08 1.3265E<<07 1.441 0E-05 1.4409E-05 1.4413E.05 2.0339E 05 1 4409E" 05 APPENDIX B 4 of 7

NOEL Haae:

Saao Initiator Contributfons to End State Croup s ALL Total Frequency for the End State Crcay ~ 4.6546E-05 13:53:16 07 HAR 1994 Page 1

Inltfatole ~ ~ ~ ~ ~ Frequencyo

~ ~ ~ ~ ~ Unaccountedo

~ ~ ~

LOSP FLTB CIV LOFM LOAC LOCV TTMB TT IOTH ISCRAH L500 FMRU LRCM LLO SCRAHR HLOCA IOOV LOPA PLFM SLOCA LLO LLS LLC ISLOCA LICA PRFO LUPS IOTV PLOC FLRB3S BOC ELOCA VLOCA LICB FLPH1 UI Ull FLRB2 FLRB3C LIIB LIIA i.ls FLRS1 LIA 3.3102E-05 4.6209E-06 1.6121 E-06 1.3316E-06 7.1519E-07 6.5200E 07 6.2573E-07 6 1537E-07 4.7779E.07 4.5136E-07 3.5934E-07 2.3407E-07 2.0992E-07 2.0638E-07 2.0611E-07 2.0445E-07 1.8923E 07 1.1821 E-07 9.0066E-OS 7 3674E-08 6.6258E-08 5.8022E-08 5.1519E-OS 4 6335E-OS 4 4551E-OS 4.3762E-OS 3.5680E-OS 2.7658E-OS 2.1360E-OB 1.9005E-OS 1 3790E.OS 9.0831E-09 6.4502E-09 3.3341E-09 2 1330E-09 6.4613E-10 2.8038E-10 2.5728E-10 2.4277E-10 0.0000E+00 0 0000E+00 0 0000E+00 0,0000E+00 O.'OOOOE+OO 5.6494E-04 3.6973E.05 1,7464E-04 1.7047E-04 4.6827E-05 4.3860E.04 4.3190E-04 7.0889E.04 4.233SE-07 7 9987E-04 1.0259E-04 2.S159E-04 3.9927E-05 5.7611E-OS 1.2874E-04 1.9978E-06 3.6261E-05 1 8481E-04 3.3703E-04 3.6605E-06 3.3187E-QS 3.0821E-OS 2 9335E-08 6.4779E-11 1 2164E-05 4 9752E-05 6.7183E-05 1.2131 E-05 4.6491E-05 9 7981E-07 5.7584E-07 3 0690E-10 2i8895E-05 1.2527E-05 3 1985E.05 4.9671 E.07 4,0939E-07 4,2125E-OS 1.2287E-07 1.3490E 05 1e3488E-05 1.3493E-05 1+8934E-05 1 3488E-05 APPENDIX B 5 of 7

flWgl hOWC ~

s>v&v initiator Contributions to End State Group : ALL Total Frequency for the End State Group ~ 4.6439E-05 14t42:52 OF HAR 1994 Page 1

lni't'latoro ~ ~ ~ ~ ~ Fl equencyo s ~ ~ ~ ~ Unaccountede

~ ~ ~

LOSP FLTB Clv LOFM LOAC LOCV TTWB TT lOTH 1SCRAH L500 FURU LRCM SCRAKR LLO KLOCA 1OOV LOPA PLFM SLOCA LLO LLS LLC 1SLOCA L1CA PRFO LUPS lOTV PLOC FLRB3S BOC ELOCA VLOCA LlCB FLPII1 Ul UlI FLRB2 FLRB3C L118 L11A L18 FLRB1 LlA 3.2993E-05 4.6616E-06 1.6105E-06 1.3283E-06 F 1755E-07 6.4950E 07 6.2340E-07 6.089?E-07

'.7716E-07 4.5111E-07 3.5703E-OF 2.3343E-OF 2.0939E-OF 2.0550E-07 2.0410E-OF 2.0176E-OF 1.8N1E-07 1.1783E.07 8.9071E-N 7.3534E-OS 6.2526E-N 5 4871E-08 4 862CE-08 4 6335E-08 4 4963E-08 4 2999E-08 3 5648E-08 2 7625E-08 2 1164E-08 1i8910E-08 1 3709E-08 9 07?SE 09 5.4038E-09 3.3534E.09 1 1071E 09 6.41 83E-10 2 7?8SE-10 2.5600E-10 2 4157E-10 0 0000E+00 0.0000E+00 0.0000E+M 0 0000E+00 0 OOOOE+00 5 S179E-04 3.8?51E-05 1.83?CE.04 1 7941E-04 4.8935E-05 4.5860E-04 4.5192E-04 7.46?SE-04 4.4828E-OF 8.420CE-OC 1.06?3E-04 2 9420E-04 4.1242E-05 1.3568E-04 6.156?E-OS 2 102ZE-06 3.8129E-05 1.9265E-04 3.5369E-04 3 8483E-06 3.5C21E-OS 3.3019E-08 3.130?E-OS 6.4779E-11 1.2661E-05 5.2018E-05 7.0369E-05 1 2680E-05 4.8?51E-05 1 0219E 06 6,0631E-OF 3.1220E-10 3.0313E-05 1.3040E-05 3.3499E-05 5.2218E-07 4 3038E-07 4.3548E-N 1.293?E-OF 1 4072E-05 1 40?1E-05 1 40?5E.05 1.981 5E.05 1 4071E 05 APPENDIX B 6 of 7

Illlt)A%ofValet l~rsrtw or roe TOtal Frequenoy far lha End State OrCap e 4.6263E-O5 10s20804 11 INR 1994 Page 1

loltlatoro error Frqq IOIIOVo~ oroo IAIaCCOIaItCClo~ ~ r I.OSP FI.TB Clv LOFII LOAC I.OCV TTMB TT lOTII lsCRAN L500 FMRU LRCII SCRAIIR IILOCA LLO lOOV LCPA PLY SLOCA LLO LLS LLC lSLOCA l.lCA PRFO LVPS lo'TV PLOC FLRBSS SOC ELOCA VLOCA LICS SLPHl Vl Vll FLRSZ FLRIQC Llla lllA LlQ FLRST LIA 3o 292SE.05 4.6498K-06 1 6011K 06 1o3159K 06 7ol549E-07 6.4623K-07 6o2084E 07 6.0465K 07 4o7686S 07 4.33578 07 "

3o52dZK"07 2-2781K 07 2.0724K-OF 2 0205Er07 lo9995E-07 1 9544E-07 1.86818.07 1,0518K 07 8,8249K"08 7o32248o08 6olS'l6E-08 5,4177E-08

.8062K-08 Cod335K-08 Ce 4431K-08 4.3045E.OS 3.5090K 08 2 7220E 08 2,0941E-08 1 e 887RE-08 1 5700K N 9.07168 09 5o3C218-09 3o RZbbE-09 1 ~1048Eo09 6o3855Er10 Ro751mr10 Ro5548Er10 2,4108Kr10 Oo0000KKS 0.0000EKlO O.'00002400 0.0000K+00 0,0000Et00 5 9282K 04 4 0004K 05 le9000E 04 1o 8531K.OC.

5 0397Eo05 4.7183K-04 4.65248o04 7o69078 OC 4.63388-07 SodbTSK-04 1 094CE-04 3o0218E-04 4o2113E 05 1 o40038 04 Re1558E-Ob 6e3984E-N 3o9319E 05 1o9757E 04 3o 6346E-OC 3o9676E 06 3odFd7E-08 3o 4285K-N 3o R489E-08 do4779E-11 1.29838-05 5.35948-05 7o2275E 05 1o2995E 05 5o0'lbCE-05 1o04488-06 do2435E 07 3 1836Eo10 3e11598.05 1o3367E-05 3o4803E 05 5e38ZTE 07 ioCMSEo07 io4739E 08 132918 07" 1o4413K-05 1e4411E 05 1.4415%-05 Ro0557E 05 lo4C11E 05 APPENDIX B 7 of 7

ENCLOSURE 6

TENNESSEE VALLEY.AUTHORITY BROWNS FERRY NUCLEAR PLANT (BFN)

UNIT 2 PROPOSED TEMPORARY TECHNICAL SPECIFICATION (TS)

CHANGE TS-347T COST BENEFIC1AL LICENSING ACTION (CBLA)-07 ANALYS1S I'UMMARYOF CBLA-07 TVA requests a temporary change to the Unit 2 TS that would allow performance of needed modifications to the Unit 1/2 480-volt and 4160-volt shutdown board control power supplies while Unit 2 is operating.

The change principally involves extending the control power supply allowed outage time (AOT) in TS 3.9.B.8 from five days to 45 days.

Extending the AOT to perform the modifications while Unit 2 is at power inv'olves substantial cost savings and low safety significance.

TVA estimates that approval of the temporary change will save approximately

$1,000,000.

II'ACKGROUND The Unit 1/2 480-volt and 4160-volt shutdown boards and Unit 3 4160-volt shutdown board "3EB" use control power that is supplied by the 250-volt DC control power supply system.

Each control power supply consists of lead-acid batteries,

chargers, circuitry, switches, indicators, and alarms.

These power supplies are referred to as the "shutdown board batteries and/or its associated battery board" in TS 3.9.B.8.

This system also supplies normal and alternate power-to the nonsafety-related Anticipated Transient Without Scram (ATWS) protection system.

LCO 3.9.B.8 states:

From and after the date that one of the 250-V shutdown board batteries and/or its associated battery board is found to be INOPERABLE for any

reason, continued REACTOR POWER OPERATION is permissible during the succeeding five days in accordance with 3.9.B.7.

The reference to LCO 3.9.B.7 requires that NRC be "notified within 24 hours2.777778e-4 days 0.00667 hours 3.968254e-5 weeks 9.132e-6 months of the situation, the precautions to be taken during this period, and the plans to return the failed component to an OPERABLE status."

1II~

REQUESTED NRC LICENSING ACTION TVA requests a temporary change to TS 3.9.B.S that would involve the following principle elements:

Extend the AOT from five (5) days to forty-five (45) days

'emove the NRC notification requirements if the batteries are inoperable to perform planned modifications.

Permit resumption of power operation if a shutdown occurs'VA requests that the change to the TS be granted for a period of one year.

This will allow time to perform the modifications to all four of the Unit 1/2 power supplies and allow time in between power supply out-of-service periods to perform maintenance and surveillance tests, setup for the next battery replacement, etc.

One year should also allow sufficient contingency time to handle unforeseen, short-term circumstances (e.g.,

short term outages, component

breakage, scheduling restrictions).

To support TVA's need to perform the power supply modifications prior to Unit 3 fuel load, TVA requests that the amendment granting the temporary TS change be issued by December 1,

1994.

TVA requests that the amendment be made effective, for the.period..of. January 1,

1995, to December 31, 1995.

The initial implementation period is needed to ensure that proper preparations are made to start the work.

IV.

BASIS FOR REQUESTED NRC LICENSING ACTION This temporary change to the Unit, 2 TS is requested so that TVA can perform modifications to upgrade the 250-volt DC shutdown board control power supplies while Unit 2 is operating.

The modifications are needed to support load growth requirements associated with Unit 3's return to service in late 1995/early 1996.

Additionally, prompt performance of the-system upgrades is needed as soon as practical for the following reasons:

The 250-volt control power batteries will soon need to be replaced since they are approaching the end of their qualified service life.

The first battery's qualified service life expires in November 1996.

Installing new components will increase system reliability.

TVA anticipates that the new batteries will have a lower failure rate.

E6-2

Installing new batteries will reduce the present maintenance requirements= associated with the old

'atteries.

The old batteries require annual maintenance as they approach the end of their qualified service life.

The new batteries will require biennial maintenance.

The annual maintenance requires that the batteries be removed from service, thereby reducing their availability.

Increasing the maintenance period back to two years will improve the system's overall availability.

TVA estimates that approximately forty-five days is needed to perform the modifications and conduct necessary testing for each power supply.

JUSTIFICATION FOR HIGHER PRIORITY REVIEW CBLA-07 Xs Safet Neutral TVA considers that extending the 250-volt DC shutdown board control power supply AOT to 45 days will not adversely impact the health and safety of the public.

The planned modifications will increase'he capacity and reliability of the 250-volt DC shutdown board control power supplies resulting in a net safety benefit.

The following considerations justify performance of the modifications while Unit 2 is operating:

250-volt DC control power will be provided through qualified, alternate safety-related power supplies.

Units 1 and 3 will be defueled during the modification.

This results in reduced electrical loading on the alternate power supplies and excess capacity being available.

All safety systems will have power available during the proposed modifications.

Only one shutdown board control power supply will be removed from service at a time.

At no time during a modification period will any of the three unit power supplies be removed from service for planned maintenance.

Performing the proposed 250-volt DC control power system modification will increase system reliability and is required for multi-unit operation due to increase in loads.

TVA performed a Probability Safety Assessment (PSA) to show that there is an insignificant increase in risk associated with the proposed amendment.

S 0

CBLA-07 Provides Si nificant Cost Savin s and Other Benefits The alternatives to extending the AOT and performing the modifications at power involve high cost.

TVA estimates that approval of this temporary TS change would save approximately

$1,000,000.

This amount is the least expensive of the two options considered by TVA.

The first option considered by TVA involves performing the power supply modifications during a refueling outage.

The next Unit 2 refueling outage is the only outage scheduled between now and Unit 3's return to service so it was the only one considered for cost estimation purposes.

The refueling outage duration is currently scheduled to be approximately 40 days.

To perform the power supply modifications during the refueling outage, the outage duration would need to be extended by at least 80 days (with or without defueling).

An 80-day refueling outage extension would be necessary since the modifications cannot be performed on all of the power supplies in parallel.

At least two shutdown board contxol power supplies are required to be functional to support heat removal needs during refueling.

Additionally, the limited access to the areas where the work would be performed precludes reducing the time required to perform the modifications/testing.

Extending the refueling outage would involve a minimum cost increase of approximately

$18.8 million.

This amount simply considers replacement power costs

($235,000/day) and does not include additional outage-related expenses (e.g.,

personnel costs).

The second option involves developing and installing a temporary control power system.

The temporary system would be used to supply shutdown board control power so that the modifications could be performed while Unit 2 is at power.

The temporary system would need to be designed and installed to meet applicable design requirements (e.g.,

environmental, seismic).

Of the two options, installation of a temporary control power system would be preferred since it involves substantial cost, savings over extending the refueling outage.

TVA estimates that design, installation, and procurement of the equipment necessary to support a fully qualified, temporary system would cost approximately

$ 1,000,00O.

E6-4

Vj0 CONCLUSZON Extending the AOT for the 250-volt DC shutdown board control power supplies has a negligible impact on plant safety.

This is demonstrated in TVA's PSA.

The alternatives to the AOT extension involve a significant cost burden that is not necessary to maintain an acceptable level of safety.

TVA has determined that a temporary TS change is a cost beneficial licensing action since it is safety neutral and provides significant cost savings.

Therefore, TVA requests expeditious NRC review of this proposed request.

E6-5

t k

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ENCLOSURE 7

TENNESSEE VALLEY AUTHORITY BROWNS FERRY NUCLEAR PLANT (BFN)

UNIT 2 PROPOSED TEMPORARY TECHNICAL SPECIFICATION (TS)

CHANGE TS-347T LIST OF COMMITMENTS The following commitment will be implemented prior to the anticipated approval of proposed technical specification change number TS-347:

Modifications to the 3EB 250-volt DC shutdown board control power supply will be performed during the next Unit 2 refueling outage (Cycle 7).

The following commitments will be implemented following approval of proposed TS change number TS-347:

Modifications will be performed in series such that only one 250-volt DC shutdown board control power supply is being modified at a time.

Succeeding modifications will be performed promptly while minimizing the impact on the plant.

While shutdown board control power supply modifications are in

progress, there will be no planned maintenance (corrective or preventive) on any of the safety related 250-volt DC power supplies (plant DC power and shutdown board control power) that could affect their operation.

Planned maintenance will be limited to those periods between control power supply modification outages.

Additionally, there vill be no planned maintenance activities which would render critical safety equipment (e.g., diesel generators, emergency core cooling system pumps) out of service unless authorized by the Plant Manager.

TUA vill develop a list of critical safety equipment within the scope of this limitation.

3.

While shutdown board control power supply modifications are in

progress, unplanned corrective maintenance vill not. be performed on critical safety equipment unless necessary to restore OPERABILITY.

This unplanned maintenance will receive the highest. priority.

Maintenance activities on critical safety equipment will be performed within the AOT's provided in the plant technical specifications.

Every effort will be made to minimize the amount of time maintenance is performed on critical components.

While shutdown board control power supply modifications are in

progress, surveillance testing on the 250-volt power supplies (both plant DC power and shutdown board control power) and critical safety equipment will be scheduled around control power supply modification outage periods where possible.

Daily, weekly, and monthly surveillances will continue to be performed in accordance with TS requirements at their specified frequency.

Surveillance testing performed at quarterly or longer frequencies will be scheduled around shutdown board control power supply modification periods where possible.

Plant Manager authorization will be required to perform these surveillances on critical safety equipment during a power supply modification period.

Pre-job briefings will be conducted prior to beginning each shutdown board control power supply modification.

These briefings will be held to ensure that individuals are familiar with the scope of the work, knowledgeable of their responsibilities, and aware of the hazards.

Training and procedures will be provided to operations personnel describing the actions to be taken if a 250-volt DC power supply failure occurs while it is supplying shutdown board control power loads.

Plant operating personnel (i.e.,

Shift Operations Supervisor, Assistant Shift Operations Supervisor, Senior Reactor Operators, Reactor Operators, and Unit Operators) will be appropriately trained in the use of this procedure prior to their assuming operator responsibilities while control power supply modifications are in progress.

A temporary power supply cable will be staged and made available so that control power can be restored to the shutdown boards using another power supply.

The appropriate procedures/work instructions will be developed to describe the actions to be taken in the unlikely event use of this restorative feature is necessary.

E7-2

1,

ML18037A876

Text

2.0 BACKGROUND

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