ML20067D400

Procedure Q, Response to Void in Reactor Vessel

ML20067D400
Person / Time
Site:	Beaver Valley
Issue date:	12/07/1982
From:	DUQUESNE LIGHT CO.
To:
Shared Package
ML20067D395	List: ML20067D390 ML20067D400
References
RTR-NUREG-0737, RTR-NUREG-737, TASK-2.B.1, TASK-TM 1.6.4, NUDOCS 8212130245
Download: ML20067D400 (8)

Text

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OPERATING MANUAL PROCEDURE Q RESPONSE TO VOID IN REACTOR VESSEL 4

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8212130245 821207 PDR ADOCK 05000334 PDR P

BVPS - OM 1.6.4 Q. Response to Void in Reactor Vessel This procedure describes response to a detected, or suspected void, (condensible, or non condensible) in the Reactor Vessel.

The specific accident which caused the void to be formed will not be discussed, instead, it will be assumed that a void exists regardless of the specific accident scenario.

Symptoms

1. Variations from the normal pressurizer pressure and level response due to normal charging and spraying operations.

The pressurizer level may decrease during a RCS pressurization from charging due to RCS void contraction, and level may rise rapidly during spray operations due to RCS void expansion.

2. Reactor Core Cooling Monitor (SCM-RC-100] or the Margin to Saturation Meter [ SCI-RC-100] indicate departure from sub-cooled conditions.

3. A plant evolution that may result in the introduction of significant amounts of non condensible gases to the RCS, such as accumulator tank discharge has occured.

Automatic Actions - None Required.

Immediate Manual Action - lbne Required.

Follow Up Actions A. If the symptoms of a Reactor Coolant System Void Exist, attempt to determine the void size as follows:

1. Achieve a constant pressurizer level and pressure condition.

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

of pressurizer span.

I 3. Record the following parameters.

a. RCS Pressure PSI

b. PZR Level  %

c. Charging Rate GPM

d. Total Seal Injection Flow GPM

e. Total Seal Leak Of f Flow GPM 1

f. Time Readings Taken

BVPS-0M 1.6.4

4. Isolate the RCS letdown flow, turn off all pressurizer heaters, and terminate the pressurizer spray.

5. Allow the RCS charging ficw to either increase RCS pressure 100 psi or increase pressurizer level 5% of span.

6. Record the RCS pressure, pressurizar icval and time at the completion of the charging transient.

a. RCS Pressure PSI

b. PZR I4 vel  %

c. Time Readings Taken

7. Reinitiate F.CS letdown flow and restore normal pressurizer pressure and level control.

8. Calculate the initial and final pressurizer vapor space volumes as follows:

r sudzer =

,fa g (1-PZR. Level % x 528 FT *)+200 FT **

3

= FT

(,,I y,

= (Initial Volume)-(Change in PZR I4 vel x 528 FT *)

3

+200Fh**

, g

9. Determine the total volume of water charged to the RCS as follows:

Charged Volume =

(Charging Flow Rate Seal Injection Flow Rate, Seal Leak Off Flow Rate)

[ Step 3.c.] [ Step 3.d.] [ Step 3.e]

X Elapsed Time X 1

[Diff. Step 6.c. and 3.f.] 7.45 GAI,.

FT' 3

= FT

10. Calculate the expected change in pressurizer level from the volume charged as deteremined in Step 9.

3 100 %

Expected (Step 9.] Vol. FT ) X ( 528 FT **}=

Pressurizer, (Charged 3 Level Change

• A Voldme of pressurizer spanned by level instruments

• • Volume of pressurizer above spanned level

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11. If the actual pressurizer level change is less than the expected level change then a gaseous void exists in the ,

RCS. Perform step 12 to determine the volume of the RCS ~

void. '

^

12.

The initial and final RCS gaseousevoid volumes can be cal-

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culated from the ,following equations: ,' h ,, <

- o Initial RCf'"(Cha'rgedVo1U'I" *1 Y"E # Y 1"*" Final Vapor Volume Void

- [ Step 8] Mtep 8'

[ Step 9]

( Initial Pressure. (Step 3? )

/'

~

g' Final Pressure [ Step 6] / ,

3

= FT

• e  ?

FM RCS (Initial CS V id' ) 4 Void

=

[ Determined Above} [ StepX (I 3] itial Pressure) ,

(Final Pressure) ,

[ Step 6.a.L '#

• B. If a gaseous void is indicated by perfonnance of Step A, attempt '

to condense the void as described below. This attempt will g

ultimately succeed if the RCS void 'is steam.

• CAUTION: Do not stop any running RCPs or start any stopped <- *1 ~ t RCPs until completion of this procedure. , ,

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1. Record RCS pressure as indicated by trend recorder. '

RCS Pressure __ PSI

'( .s )

2. Verify that the RCS is in a stable condition by eradring that:

a. Pressurizer level is between 40% and 60% ,' j] ^.g

b. RCS pressure is stable '

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c. RCS hot leg temperature is st&ble ,,

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These stable RCS conditions must be achieved prior to '

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proceeding with this procedure.

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3. Turn on all pressurizer heaters and increase' RCS pressure 50 psi while maintaining a balanced charging arid letduwt flow I and while maintaining pressurizer

• level greater tFan 20%. -

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W NOTE: If pressurizer level drops below 20% of span, turn off the pressuri::er heaters and return the RCS to the stable conditica described in Step 2.

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4. Af ter raising RCS pressure 50 psi, perform step A to determine if the attempt to condense the steam bubble

, 1.hss been effective.

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a. If no further indication of an RCS void exists,

, 'this procedure is complete.

, b. If a RCS void is still indicated it umst be assumed

, ,the void consists of non condensible gas, and an

? RCS vent is required.

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/ C. Preparation of Containment for Vessel Head Vent.

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1. Verify the Containment Purge and Exhaust system is not in 6

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i operation, and is isolated.

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C i

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\ ,- i 2.- St2rt all available containment air circulation equipment.

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3. Monitor containment hydrogen concentration and if required place the hydrogen recombiners in operation ou BVPS 0.M.

Chapter 46 Sect. 4 Procedure A, B and C.

D. Determine Maximum Allowable Venting Period as follows:

1. Convert the containment free-volume to containment volume

, at standard temperature and pressure conditions.

Cont. Pressure ** 492 'R

, ('ont. Volume (STP)=[1,890,000 FT *] X [ 14. 7 PSIA ] X [ Cont. Temp.***]

~

=

FT

2. Recor,d the containment hydrogen concentration.

H2A-HY-101A'  % H2A-HY-101B  %

' ,~ 3. Calculate the maximum hydrogen volume that can be vented to j the containment which will result in a containment hydrogen concentration of less than or equal to 3 percent volume.

Cont. H Conc % Cont. Vol.

Max. H 2

Vol.= (3.0% - [Highes$ Reading from Step 2. ]) x ([ Step 1.])

l 10 0 %

, g 3

4. From Curve #1 (RCS Pressure vs. H2 Flow Rate) determine the allowable venting period which will limit the containment s hydrogen concentration to 3% volume.

Max. H p

VentingPeriod=[ Step $] Vented =

Mins.

~ H Flow Pete lberve#1]

• Containment Volume = 1,890,000 FT

• • If containment pressure has increased above 14.7 psia then use

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14.7 psia as pressure for conservatism.

• • • Temperature in degrees Rankine (*F + 460)

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

,' BVPS-0M 1.6.4 E. Vent Termination Criterion.

1. If any vent termination criterion listed below is reached or exceeded while venting, immediately stop venting.

a. Containment hydrogen concentration greater than 3%

as observed on Containment Hydrogen Analyzers [H2A-HY-101A or 101B].

b. Reactor Coolant Sub-cooling decreases below 50* as determined from Figure 53-1 or 53-1A.

c. Pressurizer level decreases below 20% of span.

d. Maximum vent duration determined in step D.4. is reached.

e. Expected vent duration determined by Curve 1 and the RCS void volume calculated in Step A.12.

f. RCS pressure decreases by 200 psi.

NOTE: Venting of hydrogen to containment through the direct path or through a ruptured PRT rupture disc will cause an increase of containment hydrogen concentration. If large quantities of hydrogen must be vented, the recom-biners must be in operation and even then hydrogen con-centration may approach combustible levels. If the concentration approaches combustible levels, the decision will have to be made to continue venting, or to secure venting until containment hydrogen levels decrease. The decision to continue venting should be based on full con-sideration of all plant conditions including the status of core cooling and containment hydrogen level.

Venting the reactor vessel should take priority over containment hydrogen limits due to the potential for interruption of core cooling with hydrogen in the vessel.

Venting the pressurizer should not take priority over containment hydrogen limits unless the pressurizer bubble is interferring with the ability to maintain pressure control.

F. Determine the optimum vent path using the following guidelines.

a. With only one power source available, vent through the powered solenoid valves to containment.

b. With power available to both valves and the PRT rupture disc blown, vent to the PRT if there is water in the tank to take advantage of the cooling provided by this water.

c. If there is no water in the PRT, vent to atmosphere.

The location of the atmospheric vent will provide more complete mixing with the containment atmosphere and quicker access to the hydrogen recombiners.

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, , BVPS-0M 1.6.4

d. With power availcble to both paths and the PRT rupture disc intact, small quantities of gas may be vented to the PRT snd thus not enter the containment atmosphere.

e. Large quantities of gas should be vented directly to containment.

G. Vent the reactor vessel as follows:

1. Increase the RCS subcooling to 50* as determined from Figure 53-1 or 53-LA by either initiating an RCS pressurization or by dumping steam from the non-faulted steam generators.

2. Isolate letdown and manually control charging to raise pressurizer level to greater than 50% and less than 90% of span.

CAUTION: The venting operation may result in pressure dropping below the SI setpoint.

3. Manually block the low pressure SI circuit if RCS pressurizer is less than 2000 psig, and the "PZR SI BLOCKED" status light is illuminated.

CAUTION: The circuit will be automatically unblocked if the RCS pressure increases above 2000 psig. If this occurs, the blocking will have to be repested when pressure is again reduced below 2000 psig.

4. Immediately before initiating vessel vent, manually raise charging flow to maximum. This limits the pressurizer pressure and level decrease during the vent.

5. Vent the reactor vessel to containment or the PRT by opening:

a. [SOV-RC-102A or 102B] Reactor Vessel Vent Valves and

[SOV-RC-104] Vent to PRT Isolation Valve jyt [SOV-RC-105]

Vent to Containment Isolation Valve.

i 6. Stop venting by shutting valves opened in previous step when

one of the vent termination criterion is met.

7. Return RCS pressure control and PZR level control to normal.

Verify RCS is stable.

8. When vent is complete and RCS is stable perform step A.1-12.

to determine the effectiveness of the vent on void removal.

If RCS void is still indicated repeat steps D, E, F and G until no further voiding is indicated.

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2000 . -

BVPS-OK..' 1.6.4 CURVE #1 1500 _

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a 3 1000 -

w d

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m

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t i

500 -

4 f

j r

• l 1000 2000 3000 4000 '000 5

HYDROGEN H 0W iLATE

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