ML17319A962

Reactor Vessel Head Vent Operation.

ML17319A962
Person / Time
Site:	Cook
Issue date:	02/28/1981
From:	INDIANA MICHIGAN POWER CO. (FORMERLY INDIANA & MICHIG
To:
Shared Package
ML17319A959	List: ML17319A958 ML17319A960 ML17319A961 ML17319A962 ML17319A963 ML17331A772
References
AEP-AMP, PROC-810228-01, NUDOCS 8107210424
Download: ML17319A962 (16)

Text

REACTOR YESSEL HEAD YEHT OPERATION AEptAHP

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REYI SION 0 FEBRUARY, 1981 8107210424 810715 PDR ADOCK 05000315 P PDR

REACTOR VESSEL HEAD V El'lT OPERATIOI'!

A. PURPOSE The objective of these instructions is to specify required operator actions and precautions necessary to remove gases from the reactor s

vessel head by operation of the Reactor Vessel Head Vent.

CAUTIOII: This venting guideline should not be used as the primary means to mitigate an Inadequate-Cove Cooling event.

Refer to Inadequate Core Cooling:Guidelines -for appropriate operator actions and precautions.

CAUTION: ;his venting guideline assumes that the reactor containment conditions are near normal conditions and that any venting operation is performed prior to throttling safety injection flow during a POST-LOCA cooldowniand depressurization operation.

B. SYt1PTONS For plants with a RV level indication

1. Reactor vessel level is less than (insert plant specific value which includes an allowance for normal channel accuracy) percent of span.

For plants with/without a RV level in'dication

2. Abnormal reactor coolant system conditions such as large variations in pressurizer level during normal charging of spraying operations have occurred. &

3. If availab1e, reactor vesse1 head temperatures equal to or greater than saturation temperature.

Februa y, 1981 Revision 0 Page 1

4. Plant events have occurred (such as accumulator tank discharge,

. rapid RCS cooldown, or core uncovery events) that may result in the presence of a gaseous void in "he vessel head.

C. If1HEOIATE ACTIONS i(one D. SUSSBUUEllT ACTIONS CAUTIOH: Oo not trip any running or start any non-operating reactor

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coolant pumps during the performance of the following actions.

l(OTE: If the safety injection system is in operation, then the actions of steps marked by an asterisk will not be applicab'Ie

1. Terminate any changes to the reactor coolant system that may be in progress and bring the RCS to as close to a steady-state condition as possible.

• 2. Attempt to recombine any condensible gases by increasing RCS pr~ssure through the use of the pressurizer backup heaters and increased charging flow. If this step is successful in condensing the gas volume in the vessel head (as indicated by a return to normal readings in those parameters used to determine the presence of the gases) then return to the appropriate operating instruction.

CAUTIOli: Increased charging flow wi th condensihle gases in the RCS may resul: in a decreasing pressuri er level.. If pressurizer level decreases to less than 26".s of span, then attempt to restore level by continuing the charging flow or manually starting safety injection pumps. If level cannot be restored, then manua1ly initiate safety injection and proceed to EOI-O, Immediate Actions and Oiagnostics.

February, 1981 Revision 0 Page 2

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3. In preparation for venting, isolate the containment purge and exhaust system and the pressure vacuum relief line and start al 1 availab'le containment sir circulation equipment.

4. Increase the RCS sub-cooling to (insert plant specific value which is 50'F above the value which is the sum of the errors for the temperature measurement system used, and for the pressure measurement system translated into temperature using the saturation tables) by either initiating an RCS pressurization or by dumping steam from he non-faulted steam generators.

5. If required, perform the actions of Appendix 8 to determine the maximum allowable time period for venting {only for plants which vent directly to containment).

. *6. Isolate letdown and initiate an RCS makeup by the chemical volume and'on'.rol system to increase pressurizer level to greater than 50~ of span.

• 7. If not already performed, manually block the low pressure SI if initiation the permissive is energized.

CAUTIOtl: The venting operation may result in pressure decreasing below the SI setpoint. Action should be taken to manually block the automatic SI signal when the permissive is energized.

• 8. Increase charging flow to maximum to limit the pressurizer pressure and level decrease during the venting period.

t<OTE: Observe the pressurizer level trend during the venting and, from the following conditions, determine the probable status- of the reactor coolant system.

February, 1981 REYISION 0 Page 3

a,'pcl'!Icroseine pressuri =sr level - ";Hsecus voids exi st in the

'CS o:her than the re c.:.or vasss'I head or pr ssuri=sr.

b) Constant pressurizer level - t'o significant gaseous voids exist .in the reactor coolant system.

I c) Decreasino pressurizer level - 6aseous void exists in tl:e reactor vesse'I head.

9. Open the vent isolation valves in one@cad vent flow path.

'EMOTE: 'Lf one or both valves fail to open, close both valves and open the isolation valves'in the parallel flow path.

H l0. Close both vent isolation valves when:

a) Reactor vessel level indication sz,abilizes, OR b} .The time period determined in Step 5 is met, OR H c) Pressurizer pressure decreases by 200 psi, OR d) Pressurizer level decreases. below 20 percent of span OR e) Reactor coolant sub-cooling decreases below (insert plant specific value which's the sum of the errors for the temperature measurement system used, and for the pressure measurement sys em translated into temperature using the saturation tables).

OR f) The reactor vessel head is re<ilied as indicated by a decrease in the ra.e of a depressur.ization or a chance in the rate o-the pressurizer level .rend, February, lg81 Revision 0 Page 4

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CPJT NOH: If durino the venting period, a loss of reactor coolant pump operaon cccurs, continue the ventino and allow natural circulation to establ isi itself. I

• 11. Re-establish normal charging and letdown to maintain the pressurizer water level in the operating range.

• 12. Evaluate the response of the pressurizer level trend to determine if a gas bubble existed in the vessel. head. If a gas bubble existed and the venting was terminated prior to the vessel head being completely refilled, then return to Step 4.

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"(OTE: If multiple venting, operatiors are required and the con-tainment hydrogen concentration is equal to or greater than 3 volume percent, tho n provisions must be made to remove or reduce the volume of hydrogen from the containment prior to re-opening the reactor vessel head vent.

13. Return to the appropriate operating instruction following the successful completion of the venting of the reactor vessel head.

February 1981 Revision 0 .-"age 5

RCS G;.SEet.s VOI".

OETECTIOH r'il0 SIZING!6

l. Achieve a constant pressurizer level and pressure condition.

2. Place, the RCS wide range or pressurizer pressure and the pressurizer level on trend recorders. The scale should be 150 psig pressure and 10.. of span for level.

3. Record the following parameters.

RCS Pressure PSI PZR,Level Charging Rate GPfi "Seal Injection Flow =... retd.,

Seal Leakoff Low GPN Time

4. Isolate the PCS letdown flow, turn off all pressurizer heaters, and terminate the pressurizer, spray by placing the spray. control in manual and zeroing the demand signal.

,5. Allow the RCS charging flow to either increase RCS pressure 100 psi or increase pressurizer level 5~ of span.

6. Record the RCS pressur'e, pressurizer level and time.

RCS Pressure = PSI CI PZR Level ~ d Time

7. Reinitiate PCS letdown  : low and res ore normal pressuri=er pressure and leveI control.

February, 1981 Revision 0 Page 6

" 'cla-.e the initial and f',nal pressur.'r vaocr soace volures.

'O e)i cD 3 3 Initial Va"or Volume = (1-P7R Level '!,': 1658 Ft ) + (69 Ft )

FT Final Vapor Volume = (Initial Volume) - (a PZR Level X 1658 Ft 3 )

FT

9. Determine the total charged volume into the PCS.

Charged Volume = (Charging + Seal Injection - Seal Leakoff GP/i) X 1

. (Time) X

(~ <> Gal.)

~FT FT

10. Determine the expected pressurizer level change.

Expected a level = (Charging Volume FT ) X ( 100K 1658 Ft ll. If the ac';uaT pressurizer level change is less than the expected level change then a gaseous void exists in the reactor coolant system. Perform the following step to determine the volume of the RCS void.

12. The initial and final RCS gaseous void volumes ca'n be calculated from the following equations.

February, 1981 Revision 0 Paae 7

r initial ."-.CS Void = (Initial Vaccr Volure) - (Final Vapor Voiture) -',Cnarced Volur;.e.'nitial Pressure>

FT Final RCS Void = (Initial RCS Void) X (?nitial Pressure

'(Final Pressure)

FT February, 1981 Revision 0 Page 8

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APPENDIY "8" RV HEAD VE'lT O':I "ELIllE VE)ITillG TIRE PEP.IOD

1. Convert the containment free-volume to containment volume at standard temperature and pressure conditions.

C .li 5 )=(118*1 F FT

• Temperature in degrees Rankine ('F + 460)

• • Ifcontainment pressure has increased above 14.7 psia then use 14.7 ps g as pressure for conservatism.

2. Determine the containment hydrogen concentration in vol'ume percent units.

i'lOTE: The containment hydrogen concentration will be insigificant if there has been no leakage from the RCS to the containment.

3. Calculate the maximum hydrogen volume that can be vented to the containment which will result in a containment hydrogen concentration Haximum H2 to be Vented H Volume V 1

'3 of less than or equal to 3 volume percent;

.0 -Cont . H~ Concentration 00'~

.) X (Cont . Vol ume I STP )

4. From Curve -"'.1 (RCS Pressure vs. H2 Flow Rate) determine the allowable period which will limit the containment hydrogen concentration 'enting to 3 volume percent.

H2 Flow Rate twins.

February, 1981 Revision 0 Pane 9

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'e CURVE Pl, APPENOIX B 1

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2000 1500 (CS

'ressure (PSI) 1000 500' f l

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1000 2000 3000 4000 5000

.HYOROGEN FLOW RATE (SCFM)

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'ATTACHMENT 6 'O AEP:NRC:0584