ML20054J581

Proposed Tech Spec Changes Re Requirement That Containment Sump Level Instrumentation Be Operable for Automatic Switchover from Refueling Water Storage Tank to Containment Sump & Accident Monitoring

ML20054J581
Person / Time
Site:	Sequoyah
Issue date:	06/18/1982
From:	TENNESSEE VALLEY AUTHORITY
To:
Shared Package
ML20054J578	List: ML20054J577 ML20054J581
References
NUDOCS 8206290290
Download: ML20054J581 (15)

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ENCLOSURE 1 ..  : t ,

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PROPOSED TECHNICAL. SPECIFICATIONS'

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s SEQUOYAH NUCLEAR PLANT UNITS 1 AND 2 Y '#""

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k 7-v, TABLE 3.3-3 (Continued) ~

'15 Ei ' ENGit:EERED SAFETY FEATURE ACTUATION SYSTEM INSTRUMENTATION

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HINIMUM Si TOTAL NO. CHANNELS CHANNELS APPLICABLE

FilNCTIONAL UNIT OF CHANNELS TO TRIP OPERABLE MODES ACTION'

7. LOSS OF POWER ,

a. 6.9 kv Shutdown Board

1. toss of Voltage 2/ shutdown 1 loss of 2/ shutdown 1, 2, 3, 4 20*

board voltage on board any shutdown np board

2. Load Shedding -2/ shutdown 1/ shutdown 2/ shutdown 1, 2, 3, 4 20*

board board board  ;

R 8. ENGINEERED SAFETY FEATURE

• • ACTUATION SYSTEM INTERLOCKS

a. Pressurizer Pressure - 3 .2 2 1,2,3 22a Hot P-11 *

b. T avg

- P-12 4 2 3 1,2,3 22b

c. Steam Generator _3/ loop 2/ loop 3/ loop 1, 2 22c j Level P-14 .any loop Note: ' Manual switchover of RHR pump suction from the RWST to containment sump will be employed-until containment sump level' indicators are returned OPERABLE. Automatic switchover is

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not required'0PERABLE during the interim.

yg TABLE 3.3-4 (Continued)

ENGINEERED SAFETY FEATURE ACTUATION SYSTEM INSTRuttENTATION TRIP SETPOINTS s

x i FUNCTIONAL UNIT- TRIP SETPOINT. ALLOWABLE VALUES C

E3 8. ENGINEERED SAFETY FEATURE ACTUATION

(( SYSTEM INTERLOCES (Continued)

b. T avg -

Prevents Mancal Block of Safety

. Injection P-12' < 540*F

< 542 F

c. T,yg Hanual-Block of Safety Injection,

-Steam Line Isolation, Block Steam Dump 1 540*F 1 538 F -

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30 d. Steam Generator Level us Turbine Trip, Feedwater Isolation j P-14 (See 5. above)

. . _ - . . _ . - ._ _ - - _ _ - . . . . . . - - ..~ . . . - . .

TABLE 4.3-2 (Continued) .

M E ENGINEERED SAFETY FEATURE ACTUATION SYSTEM INSTRUMENTATION SURVEILLANCE REQUIREMENTS

{

=

' CHANNEL MODES IN WHICH CHANNEL CHANNEL FUNCTIONAL SURVEILLANCE E TEST REQUIRED Q FUNCTIONAL UNIT CHECK CALIBRATION w 1, '

3 Main Steam Generator. Water R M

c. S Level-Lca-Low 4 d. S. I. See 1 above (all SI surveillance requirements)~

e. Station Blackout N.A. R N.A. 1, 2, 3 N.A. N.A. R 1, 2

f. . Trip of Main Feedwater Pumps N.A. M 1, 2,.3

g. Auxiliary Feedwater Suction R _ . _

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7. LOSS OF POWER .

w a. 6.9 kv Shutdown Board

, g Undervoltage Loss of. Voltage .S R M 1,2,3,4 1.

2. Load Shedding a 5- . R N.A. 1, 2, 3, 4

8. ENGINEERED SAFETY FEATURE ACTUATION SYSTEM INTERLOCKS

a. Pressurizer Pressure, N.A. R (4) N.A. 1, 2, 3 P-11 .

R (4) N. A. 1, 2, 3'

b. N.A.

T,yg, P-12

c. Steam Generator -

N.A. R (4) N.A. 1, 2 Level, P-14

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m TABLE 3.3-10 5

g ACCIDENT NONITORING INSTRUMENTATION

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MINItt' JM REQUIRED NO CHANNELS

[ OF CHANNELS OPERABLE 5

w INSTRUMENT

• 1. Reactor Coolant THot (Wide Range) 2 1

2. 2 1 Reactor Coolant TCold (Wide Range) ,

3. Containment Pressure 2 1

4. Refueling Water Storage Tank Level 2 1

5. Reactor Coolant Pressure 2 1 w 6. Pressurizer Level (Wide Range) 2 1 .

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^ 1/ steam line

7. Steam Line Pressure 2/ steam line m

8. Steat Generator Level - Wide 1/ steam generator 1/ steam generator

9. Steam Generator Level - Narrow. . 1/ steam generator 1/ steam generator

10. Auxiliary Feedwater Flow Rate 1/ pump 1/purp

11. Reactor Coolant System Subcooling Margin Monitor 1 0

12. Pressurizer PORV Position Indicator $ 2/ valve 1/ valve

13. Pressurizer PORV Block Valve Position Indicator ** 2/ valve 1/ valve

14. Safety Valve Position Indicator. 2/ valve 1/ valve

16. In Core Thermocouples 4/ core quadrant 2/ core quadrant "Not applicable if the associated block valve is in the closed position.

• • Not applicable if the block valve is verified in.the closed position with power to the valve operator removed.

TABLE 4.3-7 .

1 iE . ACCIDENT MONITORIN3 INSTRUMENTATION SURVEILLANCE REQUIREMENTS S!

E CHANNEL CHANNEL CHECK CALIBRATION c: INSTRUMENT i'i R

.l . Reactor Coolant THot (Wide Range) M

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• M R

2. Reactor Coolant TCold (Wide Range)

M R

3. Containment Pressure ,

Refueling Water Storage Tank Level M R

4. .

M R

5. Reactor Coolant Pressure M R

6. Pressurizer Level .

w R 3; 7. Steam Line Pressure M .

M R

8. Steam Generator Level - Wide

9. Steam Generator Level - Narrow Ji R R

10. Auxiliary Feedwater Flowrate M Reactor Coolant Systam Subcooling M R 11.

Margin Monitor R

12. Pressurizer PORV Position Indicator li M R

13. Pressurizer PORV Block Valve .

Position Indicator R ,

____ .__14. . Safety Valve Position Indicator M In Core Thermocouples M R _

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.TAllLE 3.3-3 (Continued)

X Et: Git.!ERED SAFETY FEATilRE ACTU.iTI0tl SYSTEt1 It3STRUr-tErlTAT10t1

= I4111111HM CllAtif3ELS CilArillELS APPLICAllLE TOTAL t10. ACTIOri g OF CilArirJELS 10 ll!IP OPE RAllt E t100ES g FUNCTIONAL UtilT 7 LOSS OF POLKR 4

d. 6.9 kV Shutdown Board 1, 2, 3, 4 20"

1. ' Loss of Voltage 2/ shutdown 1 loss of 2/ shutdown -

board voltage on board -d any shutdown board 20*

2/ shutdown 1, 2, 3, 4

2. Load-Shedding 2/ shutdown 1/ shutdown board board board g 6 D Ef1 git 4EEllET) SAFETY FEATURE g 8.

• ACTUAT10t1 SYSTEtt Itif ERLOCKS 4

~ 22a 2 1, 2, 3 Pressurizer Pressure, 3 2

a.

P-11 3 1,2,3 22b

, P-12 4 2

b. T 3/ loop 1, 2 22c 3/ loop 2/ loop

c. Steam Generator

. Level, P-14 any loop

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Note: Manual switchover of RHR pump suction from the RWST to containment sump will be employed until containment sump level indicators are-returned OPERABLE.

Automatic switchover is not required OPERABLE'during the interim.

i1 . . .. .._ ._. . . _ _ . . .

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g liiBLE 3.3-4 (Continued}

5 E!Gir4EERfD SAFETY FE ATURE ACitlATICit SYSIUt lil5lRt!Mf fiTAlI0ft TRIP SETP0ltlTS

'.E SE ALLOWABLE VALUES TulP SEfP0ltiT 5 Fut4CT10t1AL titill

8. EllGINELRLD AFElY FEATilRE ACTUAT10t1 SYSTEl1 littli:t OCKS (Continued)

b. E d'T. vents !!anual Block of Safety in jection P-12 5 540 F $ 542 F

c. T d v,)

hanual Blu % of Safety Injection, Stewa Line Isolation, Block Steam

> 540 F > 538 F Du:ap l i 4 d. Steam Generator Level (f lurbine Trip, Feedsater Isolation ,

y P-14 (See 5. above) 5 4

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1 m j ENGI!1EERED SAFETY FEATURE ACTUATIO!! SYSTEtt Ill5TRUf4ENTATION

, g SURVEILLAtlCE REQUIREf:ENTS .

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4 c CHANNEL H0 DES FOR M11CH

5. . CHANNEL CHANNEL FUNCTIONAL SURVE!LLANCE IS FUNCTIONAL UNIT CilECK ' CAllBRATION TEST REQUIRED-

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• ACCIDLili MONITORiflG INSTRUMilll A110N SURVElll AtiCE REQUIREMENTS

'E CllANNEL CHANi4EL Q CllECK CALIBRMION m INSTRUMENT M R

1. Reactor Coolant Tilot ( de Range) l H R

2. Reactor Coolant-TCold (We Range) .

H R

3. Containment Pressure

, l M R

4. Refueling Water Storage Tank Level H R S. Reactor Ccolant Pressure M R w 6. Pressurizer Level ';

2 .M R

7. Steam Line Pressure

o. R

$ M j

8. Steam Generator Level - (Wide)

M R

9. Steam Generator Level - (Narrow) 11 R

10. Auxiliary Feedwater Fiowrate M R

11. Reactor Coolant System Subcooling Margin Monitor

!! R

12. Pressurizer PORV: Position Indicator M R

13. Pressurizer PORV Block Valve

• Position Indicator M R

14. Safety Valve Position Indicator '

I M R

.16. In Core thermocouples

ENCLOSURE 2 JUSTIFICATION FOR PROPOSED TECHNICAL SPECIFICATIONS SEQUOYAH NUCLEAR PLANT UNITS 1 AND 2 A problem has been identified concerning containment sump wide range level instrumentation at Sequoyah units 1 and 2. The instrumentation has been evaluated, and it has been determined that the instrumentation will fail in harsh environments. Failure modes include: (1) off-scale high, (2) indication higher than true level, and (3) indication lower than true level.

The estimated time required to modify the instrumentation is approximately 30 days.

The containment level instrumentation is designed to perform two different functions: (1) input to the logic which controls automatic switchover of emergency core cooling systems' suction from the RWST to the sump, and (2) r postaccident monitoring, including accident diagnosis. The safety implications of losing each of these functions are addressed below.

Automatic Switchover The logic for automatic switchover from RWST to the containment sump requirca all of the following: (1) Safety Injection (SI) signal, (2) two out of four RWST level channels indicating below 130" level, and (3) two out of four containment sump level channels indicating at least 30" above elevation 680'. ,

The reason for the sump level input to this logic is to prevent early switchover due to spurious RWST level signals or due to a break in the RWST (postulated to be caused by a MSLB close to the RWST). However, the 2/4 logic of the RWST level inputs provides assurance that a spurious signal will not cause premature switchover (i.e., a single instrument failure would not cause early switchover). Many other Westinghouse Electric Corporation plants do not have containment sump level input to their switchover logic; this input was designed to provide an extra mergin of safety against early switchover at Sequoyah. Although it is beneficial Lo-have, we believe the plant can be safely operated, and accidents safely mitigated without this extra margin.

The postulated accident which causes an RWST rupture is a steam line break" in the vicinity of the tank, with subsequent violent pipe whip. If automatic switchover relief on low RWST level alone, then the arction would switch to the empty sump almost inmediately, rather than continuing to pull water from the moat around the RWST. The sump level logic input was designed to prevent this.

9

. e ENCLOSURE 2 JUSTIFICATION FOR PROPOSED TECHNICAL SPECIFICATIONS SEQUOYAH NUCLEAR PLANT UNITS 1 AND 2

Therefore, in the interim, we recommend that the automatic switchover logic be defeated in favor of manual switchover. Based on worst case accident conditions, RWST volume of 370,000 gallons, full ECCS system flow, and switching at 29 percent level, the switchover will not be necessary until approximately 14 minutes into the accident. Therefore, the operator will have sufficient time to perform the manual action in a timely fashion.

Further, even with inoperable containment sump level indication, containment sump inventory can be verified by the presence of adverse containment conditions .(i.e., pressure, radiation, and~ temperature).

Postaccident Monitoring The containment sump level instrumentation is presently used by the operator to help diagnose what accident is in progress and to help monitor the automatic switchover to the sump. After accident diagnosis and

• switchover, the only foreseeable use of the sump level instrumentation is to verify a leak in a component of the emergency core cooling systems during recirculation mode operation.

The diagnostic function which the sump level instrumentation serves is to aid in determining whether or.not a line break exists inside containment.

It in used in conjunction with containment pressure and radiation for this function; it is by no means the sole parameter upon which the diagnosis is based. The containment pressure and radiation parameters alone provide the operator sufficient information to make the diagnosis. Therefore there is no safety problem, with regards to accident diagnosis, caused by the inoperability of the containment sump level instrumentation.

The automatic switchover function is addressed in the preceding section.

According to present emergency operating instructions, the sump level ,

indication, in conjunction with RWST level, merely shows the operator when automatic switchover should be taking place. If manual actions are to be taken, the operator can rely on RWST level alone.

According to the Sequoyah FSAR (section 6.3.2.11), containment sump level Indication in not needed to verify an ECCS leak. Three independent means are available to provido information to the operator for use in identifying ECCS leakage. These include the auxiliary building flood detection system, the instrumentation and alarms associated with the drainage and waste processing system, and the auxiliary building passive sump level alarm instrumentation. Therefore we see no safety problem, concerning ECCS leak detection, caused by the inoperability of the sump level instrumentation.

Operational Limitations or Actions

The following actions should be taken to ensure safe operation until the l containment sump level instrumentation is modified, t

1. The logic for automatic switchover of ECCS suction from the RWST to the containment sump shall be defeated such that the switch can only be l performed manually.

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2. The E0Is should be revised to reflect the change from automatic to manual switchover. Manual switchover should not be performed until there is positive indication of abnormal containment conditions in conjunction with low RWST level. This will preclude the possibility of early switchover in the event of RWST rupture (as postulated above).

The E0Is should also be evaluated for any changes necessary to preclude reliance on containment sump level instrumentation in the event of adverse containment conditions.

Conclusions Dased on the above safety evaluation, continued operation of Sequoyah Nuclear Plant units 1 and 2 is justified provided the above operational limitations and actions are implemented. This change is being reviewed by the Nuclear Safety Review Board.

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