ML20006A163

Proposed Tech Specs,Reducing Min RHR Flow Rate During Mode 6 Operation

ML20006A163
Person / Time
Site:	Sequoyah
Issue date:	01/12/1990
From:	TENNESSEE VALLEY AUTHORITY
To:
Shared Package
ML20006A161	List: ML20006A160 ML20006A163
References
NUDOCS 9001250385
Download: ML20006A163 (12)

Text

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ENCLOSURE 1

-PROPOSED TECHNICAL SPECIFICATION CHANGE SEQUOYAH NUCLEAR PLANT UNITS 1 AND 2 1 . DOCKET NOS. 50-327 AND 50-328

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(TVA-SQN-TS-89-02) s LIST OF AFFECTED PAGES Unit I

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Unit 2 .

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, . ., f ., 1 REFUELING OPERATIONS -

_3/4.9.8 RESIDUAL HEAT REMOVAL AND COOLANT CIRCULATION -

ALL WATER LEVELS LIMITING CONDITION FOR OPERATION '

FP 3.9.8.1 At least one residual heat removal (RHR) loop shall- be in operation.

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APPLICABILITY: H00E 6.

ACTION: -

a'.

With less than one residual heat removal loop in operation, except as provided in b. below, suspend all operations involving an increase .~

in the reactor decay heat load or a-reduction in boron concentration of the Reactor Coolant System. Close all containment penetrations providing direct access from the containment atmosphere to the outside atmosphere within 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br />, b.

. The residual ' heat removal loop may be removed from operation for up to 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> per 8 hour9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> period during the performance of CORE ALTERATIONS in the vicinity of the reactor pressure vessel hot legs.

c. The provisions of Specification 3.0.3 are not applicable.  !

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SURVEILLANCE REQUIREMENTS i W.th less than 278 hours0.00322 days <br />0.0772 hours <br />4.596561e-4 weeks <br />1.05779e-4 months <br /> shnce aubersts cols ty ne. t

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4.9.1.l.li.0.0.1 AM least one residual heat removal loop 'shall be v,erified to be in operation and circulating reactor coolant.at a flow rate t,f greater than or FP equal to 2500 gpm at least once per 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br />.

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H H h greoler than or efva I +o 276 hours0.00319 days <br />0.0767 hours <br />4.563492e-4 weeks <br />1.05018e-4 months <br /> Tince soberiHe.al,h;,

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residua l heat removal loop shall b e' verife'ed to be in operaRon and greater tha n o r- c.lrculoRn3 reAc+or coolan4 at 4 flo w rate of e vaj to 2.coogpm ,a t leas + ontt p er 6 2. hoves.

psM September 17, 1980 SEQUOYAH - UNIT 1 3/4 9-8 ' '

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b REFUELING OPERATIONS i

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BASES ,

3/4.9.6 MANIPULATOR CRANE .

The OPERABILITY requirements for the manipulator cranes ensure that:

2) each crane has sufficient loao capacity to lift a drive ro I

- and 3) the core internals and pressure vessel are protected from excessive lifting force in the event they are inadvertently engaged during lifting operations.  ; -

_3/4.9.7 CRANE TRAVEL - SPENT FUEL PIT AREA fuel and control rod assembly and associated handling tool over assemblies in the storage pool ensures that in the event this load is dropped:

1) the activity release will be limited to that contained in a single fuel.

.assembly, result in a.and 2) any critical array.possible^ distortion of fuel in the storage racks will not release assumed in the accident analyses.This assumption is consistent with the activ 3/4.9.8 RESIDUAL' HEAT REMOVAL AND COOLANT CIRCULATION r

The requirement that at leas't one residual heat removal (RHR) loop be in operatio'n ensures that; 1) sufficient cooling capacity is available to remove decay heat and maintain the water in the reactor pressure vessel below 140*F as required during the REFUELING MODE, and 2) sufficient coolant circulation is maintained through the reactor core to minimize +ha affar+e i incident and prevent boron stratification. Add af boron dilution '

INSERT A .

. TP The' requirement to have two-RHR loops OPERABLE when there is less than 23 feet of water above the reactor pressure vessel flange ensures that a single. failure of the operating RHR loop.will not result in a complete loss of

, residual heat removal capability.

With the reactor vessel head removed and 23 feet of water above the reactor pressure vessel flange, a large heat sink I is available for core cooling. Thus, in the event of a failure of the I

operating to cool theRHR loop, adequate time is previded to initiate emergency procedures core.

3/4 9.9 CONTAINMENT VENTILATION SYSTEM The OPERABILITY of this system ensures that the containment vent and.

purge penetrations will be automatically isolated upon detection of high .

radiation levels within the containment. The OPERABILITY of this system is

- required to to atmosphere restrict the release of radioactive material from the containment the environment.

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The. reduction of the minimum required flow rate after 278 hours0.00322 days <br />0.0772 hours <br />4.596561e-4 weeks <br />1.05779e-4 months <br /> following. '

"subWitical'ity" reduces the probability of lo is ng an RER pump by air-entrainment from pump vortexing. This is a particular concern during -

reduced RCS inventory operation. The 278-hour value is based on required decay heat removal, and the 2000 gpm value is limited by cavitation in the control valve and valve chattering in the 10-inch check valve. -

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REFUELING OPERATIONS

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3/4.9.8 RESIDUAL HEAT REMOVAL AND COOLANT CIRCULATION ALL WATER LEVELS 1

LIMITING CONDITION FOR OPERATION l

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L 3.9.P.1 At least one residual heat removal (RHR) loop shall be in operation.

APPLICABILITY: MODE 6. . -

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ACTION:

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a. With less than one residual heat removal loop in operation, except I

as provided in b. below, suspend all operations involving an increase:

in the reactor decay heat load or a reduction in boron concentration of the Reactor Coolant System. Close'all containment penetrations providing direct access from the containment atmosphere to the- '

outside atmosphere within 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br />,

b. The reskdualh ' eat removal loop may be- removed from operation for u to I hour per 8 hour9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> period during the performancs of CORE ALTERATIONS in.the vicinity of the reactor pressure vessel hot legs.

( c.

The provisions of Specification 3.0.3 are not applicable.

SURVEILLANCE REQUIREMENTS ,

Nith 'less than 9.78 hours9.027778e-4 days <br />0.0217 hours <br />1.289683e-4 weeks <br />2.9679e-5 months <br /> since soberiKcol*19)At

+.9.8.1.1 ?.0 C.1 AM least one residual heat removal loop shall be verified to be in operation and circulating reactor coolant at a. flow rate of greater than or ~

equal to 2500 gpm at least once per 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br />.

4 et 4.<),6).2. wah yeale- Son or egual 1a zie haves s ce suheroWeal,ly ,

at leas + on e. ' residua l heat r'emove l loop s ha u. b e verthed to hs '

' in operalibn ' a n d e i r e.u la H n ryeaclo$ coolant- at a flow ro le 9realv ihan oe eguoI la z. coo 3pm a_4 g,3, f ,,e, ,.,

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SEQUOYAH - UNIT 2 3/4 9-9 .:

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. 3 REFUELING OPERATIONS BASES 3/4.9.6 MANIPULATOR CRANE' *

- The OPERABILITY requirements for the manipulator cranes ensure that:

1) manipulator cranes will be used for movement of drive rods and fuel assemblies,.

2) each crane has sufficient load capacity to-lift a drive rod or fuel assembly,

- assembly, and 3) the core internals and. pressure vessel are protected from ,

excessive lifting operations. lifting force in the event they are inadvertently engaged during 3/4.9.7 CRANE TRAVEL - SPENT FUEL PIT AREA e

The-restriction on movement of loads in excess of the nominal weight of a fuel and control rod assembly and associated handling tool over other fuel assemblies in the storage pool ensures that in'the event this load is dropped

1) the activity release will be limited to that contained in a single fuel assembly, and 2) any possible distortion of fuel in the storage racks will noti

' result in a critical array.

release assumed in the accident analyses.This assumption is consistent with the a 3/4.9.8 RESIDUAL HEAT REMOVAL AND COOLANT CIRCULATION -

The requirement that at least one residual heat removal (RHR) loop be in '

operation ensures that; 1) sufficient cooling capacity is available to remove decay heat and maintain the water in the reactor pressure vessel;below 140'F as. required during the REFUELING MODE, and 2) sufficient coolant circulation is maintained thru the reactor core to mini % th - "*M e e a boron dilution

, inciden.t and prevent boron strati,fication. Add ./NSERT The requirement to have two RHR. loops OPERABLE when there-is less-than

• t 23 feet of water above the reactor pressure vessel flange ensures that a '

. single failure of the operating RHR loop will not result in a complete loss of residual heat removal capability.

With the reactor vessel head removed and 23 feet of water above the reactor pressure vessel flange, a large heat sink is available for core cooling. '

i RHR the core.

loop, adequate time is provided to initiate emergency procedure 3/4.9.9 CONTAINMENT VENTILATION SYSTEM i

The OPERABILITY of this system ensures that the containment vent and

- purg'e penetrations will be automatically isolated upon detection of L.igh '

radiation levels within the containment. The OPERABILITL af:this system is required to restrict the release of radioactive material ~from the containment atmosphere to the environment.

O SEQUOYAH - UNIT 2 8 3/4 9-2

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' The reduction of..the minimum required flow rate after.278 hours0.00322 days <br />0.0772 hours <br />4.596561e-4 weeks <br />1.05779e-4 months <br /> following suberiticality reduces the probability of losing an RHR pump by air-entrainment from pump vortexing. This is a particular concern during reduced RCS inventory operation. The 278-hour value is based on required decay heat removal, and the 2000 gym value is limited by cavitation in the control valve and valve chattering in the 10-inch check valve.

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ENCLOSURE 2 PROPOSED TECHNICAL SPECIFICATION CHANGE SEQUOYAH NUCLEAR PLANT UNITS 1 AND 2 ,

DOCKET NOS. 50-327.AND 50-328

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(TVA-SQN-TS-89-02)

DESCRIPTION AND JUSTIFICATION FOR REDUCTION OF MINIMUM RESIDUAL HEAT REMOVAL FLOW' RATE DURING MODE 6 OPERATION t

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, ENCLOSURE 2 Description of Change Tennessee Valley Authority proposes to modify the Sequoyah Nuclear Plant (SQN) Units 1 and 2 technical specifications (TSs) to reduce the minimum residual heat removal (RiiR) flow rate during Mode 6 operation f rom 2500 gallons per minute (spm) to 2000 gpm after 278 hours0.00322 days <br />0.0772 hours <br />4.596561e-4 weeks <br />1.05779e-4 months <br /> following suberiticality. This change will decrease the probability of losing an RHR pump by air entrainment from vortexing during reduced reactor coolant system (RCS) inventory operation. -

Reason for Change During Mode 6 operation at SQN, residual heat is removed from the reactor core by the RHR system. Generic Letter 88-17. Loss of Decay Heat Removal, identified the Ipas of this cooling capability as a significant problem during reduced RCS inventory operation. Since vortexing is a function of flow rate, the probability of losing an RHR pump by vortexing and consequently losing RHR capability is reduced by decreasing the RHR flow rate. This proposed change should improve the availability of the RHR .

system during reduced RCS inventory operation.

Justification for Change Westinghouse Electric Corporation haw evaluated the minimum required RHR flow rate for SQN. The decay heat removal requirements, reactor coolant thermal stratification, reactor internals / core temperature change, boron mixing and stratification, control valve cavitation, check valve chatter, and RHR pump motor thrust bearing life have been included in the evaluation.

The primary function of the RHR system is to remove decay heat from the reactor core during the second phase of cooldown. The RHR flow rate necessary to maintain acceptable RCS temperature is a function of time after initial reactor shutdown. With the most restrictive plant .

configuration of one train of RHR and one train of component cooling water .i in service, the proposed flow rate of 2000 gpm is sufficient to maintain '

acceptable Mode 6 RCS temperature after 278 hours0.00322 days <br />0.0772 hours <br />4.596561e-4 weeks <br />1.05779e-4 months <br /> following shutdown. g

.1 Reactor coolant thermal stratification is not a concern with reduced RHR '1 flow rate since there is no mechanism within the core to cause thermal stratification. Additionally, the time restrictions imposed by the core differential temperature limits are bounded by the time restrictions determined by decay heat removal. Also, the saturation temperature of the appreximately one percent boren solution of the RER system is less than 32 degrees Fahrenheit. Therefore, boric acid precipitation would not occur. Even if mass evaporation occurred, local boron concentrations would increase, which is conservative. * * -

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T'he most limiting criteria for establishing a minimum RHR fDu rate are the valve iscues. Control valve cavitation may occur at flows below .

2000 gpm. Hanger pin and hange,r piu assembly wear in the check valves may also occur because of chattering that develops at' low flows.  :

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The final evaluation performed was on RHR pump motor thrust bearing life.

The life is affected by the hydraulic downthrust load, which is dependent on pump flow rate. Based on data collection from similar pumps, bearing replacement intervals could be as high as 8.3 years for single pump operation and 16.4 years for 50 percent service duty for each pump.

In summary, the most limiting criteria for establishing a minimum RHR flow rate are the valve issues. The value of 2000 spm, which was established by the valve issues, is sufficient to maintain accqptable decay heat removal capabilitier after 278 hours0.00322 days <br />0.0772 hours <br />4.596561e-4 weeks <br />1.05779e-4 months <br /> following shutdown.

Environmental Impact Evaluation The proposed change request does not involve an unreviewed environmental question because operation of SQN Units 1 and 2 in accordance with this change would noti

1. Result in a significant increase in any adverse environmental impact previously evaluated in the Final Environmental Statement (FES) as ,

modified by the Staff's testimony to the Atomic Safety and Licensing -

Board, supplements to the FES, environmental impact appraisals, or in any decisions of the Atomic Safety and Licensing Board.

2. Result in a significant change in effluents or power levels.

3. Result in matters not previously reviewed in tha licensing basis for SQN that nay have a significant environmental impact.

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9 ENCLOSURE 3 PROPOSED TECHNICAL SPECITICATION CHANGE SEQUOYAH NUCI. EAR PLANT UNITS 1 AND 2 ,

DOCKET NOS. 50-327 AND 50-328 (TVA-SQN-TS-89-02) -

DETERMINATION OF NO SIGNIFICANT HAZARDS CONSIDERATIONS 4

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ENCLOSURE 3 Significant Hazards Evaluation TVA has evaluated the proposed TS change and has determined that-it does not represent a significant hazards consideration based on criteria established in 10 CFR 50.92(c). Operation of SQN in accordance with the proposed amendment will nott '

(1) Involve a significant increase in the probability or consequences of an accident previously evaluated.

Accidents analyzed in Chapter lb of the Final Safety Analysis Report for Mode 6 operation are limited to fuel handling accidents, and RHR flo't rate is not a consideration in fuel handling accidents. The reduction of the minimum k'HR flow rate in Mode 6 should increase the availability of decay heat removal and therefore be a safety enhancement. The proposed change will not involve an increase in the probability or consequences of an accident previously analyzed. .

(2) Create the possibility of a new or different kind of accident from any previously analyzed.

The proposed TS change does not involve significant changes to the design basis of SQN. Reducing RHR flow is a manual operation from the main control room and does not include any :aodifications or irreversible actions. Therefore, no new or different kind of accident from any previously analyzed should be created.

(3) Involve a significant reduction in a margin of safety.

The proposed reduction of the minimum RHR flow rate in Mode 6 to 2000 gpm provides sufficient decay heat removal after 278 hours0.00322 days <br />0.0772 hours <br />4.596561e-4 weeks <br />1.05779e-4 months <br /> following shutdown. The reduction should also increase the availability of the RHR pumps and consequently the decay heat removal 1 capabilities. Therefore, the margin of safety provided will not be -

reduced but increased.

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