ML20052A425

Forwards Addl Info Re TMI Action Item II.B.1,RCS Vents,Per 820224 Request

ML20052A425
Person / Time
Site:	North Anna
Issue date:	04/23/1982
From:	Leasburg R VIRGINIA POWER (VIRGINIA ELECTRIC & POWER CO.)
To:	Clark R, Harold Denton Office of Nuclear Reactor Regulation
References
RTR-NUREG-0737, RTR-NUREG-737, TASK-2.B.1, TASK-TM 127, NUDOCS 8204280323
Download: ML20052A425 (17)

Text

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VImOINIA ELucTalc Awn Powsm Cox m

Ricnwoxo, VamotwsA 20261 o+

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<f R.H.LnANBUno April 23, 1982

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Mr. Harold R. Denton Seri Office of Nuclear Reactor Regulation PSE&CS/DPB: jdm U.S. Nuclear Regulatory Commission Docket Nos.

50-338 Washington, D.C.

20555 50-339 License Mos. NPF-4 Attention:

Mr. Robert A. Clark, Chief NPF-7 Operating Reactors Branch No. 3 Division of Licensing Gentlemen:

1 1

REQUEST FOR ADDITIONAL INFOINATION REACTOR COOLANT SYSTB4 VENTS ( ITD4 II.B.1)

NORTH ANNA POWER STATION UNITS 'l AND 2 The attached responses concerning the Reactor Coolant System Vents are provided in reply to your request for additional information dated February 24, 1982.

Please advise if further information is required.

Very truly yours, N

b 1%d R.

H. Leasburg Attachment cc: Mr.

R. C.

DeYoung, Director Office of Inspection & Enforcement Division of Reactor Operations Inspection Washington, D.C.

20555 Mr. James P. O' Reilly, Regional Administrator Office of Inspection & Enforcement Region II 101 Marietta Street,' Suite 3100

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Atlanta, Georgia 30303 J

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82 04 2 8 D313

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U REQUEST FOR ADDITIO!1AL IllFORitATI0ll FOR 110RTH Atl!JA 1 & 2 s

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o Verify ' hat the reactor coolant systea (RCS) vent flow restricti.on.

i 1.

t orifices are smaller than the size corresponding to the definition of a loss-of-coolant accident (10 CFR Part 50, Appendix A) by providing the pertinent design parameters of the reactor coolant oakeup systen and a calculation of the maxinua rate of loss of reactor coolant through the RCS vent flow restriction orifices (reference HUREG-0737 Itea ll.B.1 Clarification A.(4)).

Response: The orifices on the vent system are 3/8 inch I.D.

Per the Westinghouse systen design basis the cass flos through'a 3/8 inch break is within the capacity of the normal nakeup water sy stem.

2.

The following iteas apply to the portions of the RCS vent systen that fora e part of the reactor coolant pressure boundary, up to and including the second noraally closed valve (reference HUREG-0737 Iten ll.B.1 Clarification A.(7)):

Provide the design teoperature and pressure of the piping, valves, a.

and ccnponents.

b.

Verify that the piping, valves, components, and supports are classified Seismic Category 1.

Describe the existing instrumentation cEpable of detecting a'nd c.

neasuring RCS vent system isolation valve seat leakage (reference Appendix A to 10 CFR Part 50, General Design Criterion 30).

d.

Describe the caterials of construction and verify that they are compatible with the reactor coolant chemistry and will be fabricated and tested in accordance with SRP Section 5.2.3, " Reactor Coolant Pressure Boundary Materials."

Response: a.

The design conditions of the piping and valves are 6500F, 2485 psig.

b.

The piping, valves, and supports designated QA Category 1 are classified Seismic Category 1 and Safety Class 1 or 2 where appropriate.

Leakage is detected by an increase in the amount of aakeup c.

required to aaintain a normal level in the pressurizer.

Leakage inside the containaent is drained to the containment suap where it is aonitored.

Leakage is also detected by measuring the airborne activity of the containment ataosphere and nonitoring the containnent p re ssu re.

• e

d.

The piping and ~ valve material in contact with reactor coolant water is austenitic stainless steel.

The material in contact with the reactor coolant'is compatible with the attached chemistry.

A.

Reactor Coolant Water l

Electrical Conductivity

<0 to 40 uMhos/cm at 250C Solution pH 4.2 to 10.5 at 250C 0xygen ef 0.005 ppm Chloride d 0.15 ppm Fluoride 4 0.15 ppm Hydrogen 25.to 50 cc(STP) Kg H O 2

Suspended Solids 4: 1.0 ppm 7

pH Control Agent (Li 0H) 0.7 to 2.2 ppa Li Boric Acid 0 to 4000 ppm B Silica 4 0.2 ppm Aluminum 4:0.05 ppm Calcium 4:0.05 ppm Magnesium 4:0.05 ppm B.

Reactor Coolant Makeup Water l

Cation Conductivity

<ll uMhos/cm at 250C Solution pH 6.0 to 8.0 at 250C 0xygen

< 0.10 ppm Chloride - Flouride

< 0.10 ppa Total Solids

< 1.0 ppm Suspended Solids

< 0.10 ppm Silica

< 0.10 ppm Potassium

< 0.01 ppa Sodium eC 0. 01 ppm Aluminum

< 0.02 ppm Calcium

(,0.02 ppm Magnesium 410.02 ppm 3.

Verify that the following RCS vent system failures have been analyzed and found not to prevent the essential operation of safety-related systems required for safe reactor shutdown or mitigation of the consequences of a design basis accident:

a.

Seismic failure of RCS vent system components that are not designed to withstand the safe shutdown earthquake, b.

Postulated missiles generated by failure of RCS vent system components.

c.

Fluid sprays f rom RCS vent system component failures.

Sprays f rom normally unpressurized portions of the RCS vent system that are Seismic Category 1 and Safety Class 1, 2, or 3 and have instrumentation for detection of leakage from upstream isolation valves need not be considered.

s s

Response: a.

All couponents and piping in the RCS. vent systen have been designed to withstand a safe shutdown earthquake.

b,c. Per NRC Branch Technical. Position MEB 3-1, it is ' nod,

necessary to postulate breaks in piping of diameter one inch or less.

Therefom, jet impingement, pipe whip, or missile analysis is not required.

4.

Denonstrate' using engineering drawings (including isonetrics) and design descriptions as appropriate, that the anticipated discharges of steaa, liquid and noncondensible gas from the RCS. vents to the refueling cavity will not adversely affect any nearby structures, systens, 'and components essential to safe shutdown of the reactor or aitigation of a design basis accident.

Response: The spray from both the RCS and Pressurizer Vent Systems are directed into the refueling cavity such that they do not iepinge on any components.

The pressurizer vent systen discharge is directed straight down into the refueling cavity.

The RCS Vent Systea discharge is directed at a 450 angle into the refueling canal from the reactor vessel head.

The attached sketch (Attachment III) details the approximate location of the vent system discharge for both units. All components in this area were originally designed or have been qualified to withstand the effect of a LOCA, therefore, no additional analysis need be pe rfo med.

S.

Verify that operability testing of the RCS vent systea valves will be perfomed in accordance with subsection IWV of Section XI of the ASME Code for Category B valves (reference NUREG-0737 Itea 11.B.1 Clarification A.(ll)).

y Response: Operability testing will be in accordance with subsection IWV of Section XI of the ASME Code for Category B valves.

6.

Submit operating guidelines for Ose of the RCS vent system including the following:

Guidelines to detemine when the operator should and should not a.

aanually initiate venting, and infomation and instrucentation required for this detemination (reference HUREG-0737 Itea ll.B.1 Clarification A.(2)).

The guidelines to detemine whether or not to vent should cover a variety of reactor coolant system conditions (e.g., pressures and temperatures).

The effect of the containment hydrogen concentration on the decisicn to vent or to continue venting should also be addressed considering the balance between the need for increased core cooling and decreased containment integrity due to elevated hydrogen levels.

b '.

Methods for detemining the size and location of a noncondensible gas bubble (reference Position (2) and Clarification A.(2)).

• = =

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Guidelines for operator u.se of' the vents, _ includ'ing information and c.

instrunentation available to the operator for initiating or terninating vent usage (reference Position (2)).

d.

Required operator actions in the event of inadvertent opening, or failure to close after opening, of the vents including a description of the provisions and instrunentation necessary to detect and correct these fault conditions (reference Position (2) and. Clarification A.(2)).

Methods which in lieu of venting will assure that sufficient liquid e.

or steam will flow through the stean generator U-tube region so that decay heat can be effectively renoved f rom the reactor coolant system (reference. Clarification C.(2)).

Response: a.

It is our intention to operate the RCS Head Vent Systen in accordance with the recently developed il Function Restoration Guideline, FR-1.3.

A copy of this generic guideline is provided for reference as Attachnent I.

Engineering basis for the guideline is included in a generic background document also supplied by W.

1.

The guidelina background docuaent lists, in addition to RYLIS, four synptons which should cause the operator to suspect the presence of voids in the RCS.

The conditions are covered as part of Operator Training.

l 2.

The guideline checks RCS stability, atteapts to collapse the void, checks pressurizer conditions, and RCS subcooling prior to vent operations.

3.

Instrumentation required for plant response is presently available with the exception of RVLIS. A teaporary alternative nethod for detecting and sizing voids has been provided -in the background docunent.

See Attachment II.

Hydrogen indication and control equipaent are avai.lable at present.

Step 11 of the guideline addresses containaent H2 concentration,and calculation of vent time based on the conservative assumption of the void consisting of 100% Hydrogen.

Termination due to Hydrogen concentration is addressed in Step 12.

b.

RVLIS is required to absolutely determine if the void is in the reactor head.

The methods described in Attachaent II are valid for deten.11 nation of void existance and size, but do not discriainate as to location.

At present the use of the pressurizer vent is not addressed in generic guidelines.

1 Guidelines for vent initiation are p,rovided in Ste'ps 1 thru-i c.

11 of FR-I.3.

Ternination ' criteria are reviewed in Step 12 prior to venting.

In Step 13 venting is stopped when RVLIS indicates a full or stable. level or when any of the-criteria of Step 12 are reached. :Instrucentation, with exception of RVLIS, is presently available and operable.

d.

The generic guideline does not address inadvertant opening of vent valves as such.

In Step 13 the operator is instructed to maintain redundant valves closed while not being operated.

This would preclude a single failure from opening a flow path.

The capability of local aanual isolation is provided.

Should the above methods fail, it is anticipated that the event would be detected and handled as a small break LOCA in accordance with existing plant procedures.

Pre sent instrumentaticn is appropriate for this condition.

e.

1.

The caution prior to Step 1 of the guideline atteapts to naintain void stability by leaving RCPs in their present condition.

Tripping RCPs could resJlt in gases collecting in S/G U-tubes, while starting a RCP would disperse gases collected in the. head or pressurizer and nake renoval difficult.

2.

An attempt is made to col:1 apse steaa voids prior to any venting operation.

3.

Pressurizer level is nonitored and maintained throughout the operation.

SI is initiated if level cannot be maintained.

4.

RCS subcool.ing is maintained greater than 500F.

5.

RCS pressure decreases are liaited to 200 psi for subcooling and RCP NPSH considerations.

6.

If during venting any RCPs stop, the venting is to continue.

This ainiaizes the amount of gas which will collect in S/G U-tubes while natural circulation establishes itself.

7.

Verify that all displays (including alarus) and controls, added to the control roon as a result of the TMI Action Plan requirement for reactor coolant systen vents, have been or will be considered in the human factors i

analysis required by HUREG-0737 Iten I.D.1, " Control-Roca Design Reviews."

Response: The controls and displays added to the control' roon by this codification will be considered in a huaan factors analysis to be conducted at a later date in accordance with HUREG-0737 Iten 1.D.1.

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ATTACHMENT'I w.

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FRl.3 RESPONSE TO VOID IN REACTOR VESSEL Bcsic

'.=5:3 1 Sept.1981 WEii STEP ACTION / EXPECTED RESPONSE RESPONSE NOT OSTAINED

...A Do not stop any running RCPs or start any stopped s

RCPs until completion of this guideline.

1 Ree:rd RCS Pressure -

PSIG

=E:.

= = _.

IE

2 Verify 51 System - NOT IN JF Si system is in operation, OPERATION THEN go to step 9.

1 3

Check Stchie RCS Conditions:

l

o. Pressurizer level - STABLE BETWEEN

c. Menuc!!y cdjust letdown and l

40% AND 60%

charging.

l

b. RCS pressure - STABLE

b. Opercte hecters cad sprcy.

c. RCS hot leg temperature - STABLE

c. Adjust steam dump.

4 Try To Colicpse Void in Reactor f-E Vessel:

a. Tum en pressurizer hecters to intrecse pressure by 50 psi

b. Mein'tcin bclenced charging and letdown flow

c. McIntein pressurizer level-

c. IF level less then 20%, THEN GREATER THAN 20%

turn off pressurizer hecters AND return to step 3.

5 Verify Void Coll =pse in Reactor Vessel:

a. Reacter vessel level -

c. IF level not rising, THEN go.to RISING TO FULL step 6.

b. Recctor vessel level -

b. IF level not full, THEN go to FULL step 6.

.;;a..

c. Return to procedures in effect

• 7 2'*~2

' ';* C 6

Isolete Letdown.

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i W. :en symFee/Tliis:

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FR l.3 RESPONSE TO VOID IN REACTOR VESSE!.

sesic

. (Cont.)

1 sept.1981 I.'i....5

.-2..

STEP ACTION /EXPEu D RESPONSE RESPONSE NOT OBTAINED C..l.h 7

Check Pressud:er Canditions:

a. Pressurizer level - GREATER

o. Increcse chercing flow, glevel THAN 10!?

cannot be maintcined cheve 10'/.

with maximum chcrging, THEN monucily initicte Si cnd go in E-0,

-_ =275-REACTOR TRIP OR SAFETY INJECil0N, STE? 5.

b. Pressurizer level - BETWEEN

b. Adjust chcrging flow.

20S? AND 90!?

c. RCS pressure - GREATER THAN

c. Energize heaters. IF pressure OR ECUAL TO PRESSURE RECORDED decreasing in an uncontrolled IN STEP 1 menner, THEN menucily initiate 51 i

cnd go to E-0, REACTOR TPJP OR I

l SAFEiY INJECTION, STEP 5.

l l

Nois Venting of the RPY may result in RCS pressure I

decreasing below SIinitiation serpoint.

}

~

8 Check Lew Pressudzer Pressure Si Signal Status:

c. Pressurizer Si signal - BLOCKED

o. Mcnucily block.

Check RCS Subeooling:

9

a. RCS subcccling - GREATER THAN o.1F. less than "/ "F, THEN increase

1. 1

• F steem dump. g n1 *F subcocling cannot be cbtcined, THEN go to E-0, REACTOR TRIP OR SAFETY INJECTION, STEP 5.

.m e.r..

(1) Er.ser surt of temperature and pressure mecsurement syste n errors arce. stated onto ter perature using sezuration tabler.

FLUS 30*F.

2 of 5

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Srm1r+,m/Titi :

AevisM Ha.rm RESPONSE TO VOID IN REACTOR VESSEL se:re FR l.3 (Cont.)

1 sept.1981

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STEP ACTION /EXPEti cD RESPONSE

' RESPONSE NOT OBTAINED 10 Prepers Contuinment For Reccior Ve:ssi Venting:

a. Isciate containment:

1) [ Enter plant specific list)

b. Start containment cir circulation

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equipment:

1) [ Enter plant specific list]

c. Veiify hydrogen control equipment available :

1) [ Enter plant specific list) 11 Determine Maximum A!!owchte Ven+ing Peried:

a. Centcinment Hydrogen

o. Reduce hydrogen concentration:

concentration - LESS THAN m %

[ Enter picnt specific means]

b. Cciculate maximum venting 7Ess.

(See grcph on page 5)

? IFl4NY vent termination criterion in step 12 is reached or exceeded while venting, immediately stop venting.

12 Review RPV Vent Termination Criteria With Control Room Personnel:

• Containment hydrogen concentration -

GREATER THAN 3% BY VOLUME

• RCS subccoling - LESS THAN m op

• Pressurizer level-LESS THAN 20%

=

• RCS pressure - DECREASES BY 200 PSI

• Venting period - GREATER THAN 3

PERIOD CALCULATED IN STEP 11.

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(1) Er.:er ;!act specs: value.

(') E:ter sum of te=m:ure ard pressure measureme=t system errers t:2r.s!ated in:o te=perstre usir.g saturatic: :atles.

3 of 5

Nu m b.c.

s N w m Set Revklon Na./h RESPONSE TO VOID IN REACTOR VESSEL ges:e l_

FRl.3

' (Cont.)

1 Sept.1981

. - =,...

STEP ACTION / EXPECTED RESPONSE RESPONSE NOT OBTAINED

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13 Yent Recctor Yessel

c. Open valves in one vent path

c. JF either of series valves in selected pcth fcils to open, THEN close both valves cnd open velves in secer.d path.

85

b. Cicse both volves when:

1) Reccior vessel level - FULL OR STABLE

-OR-

2) Any termination criterion of step 12 is recched

c.,lf, venting stopped beccuse of ANY criteria in step 12, THEN return to -

step 7.

5fh' 14 Check Pressurizer Level - STABLE Adjust injection end letdown, cs required.

15 Return To Guideline In Effect

-END-

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FRl.3 RESPONSE TO VolD IN REACTOR VESSEL co=re f....

(Cont.)

1 Sept.1981

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$ 7tc.a :

j A=centeinment volume (STP)

,ggg ! =(Cent. Vclume ft )X I

EI.

X (Cont. [tempercture) 3 14.7 psia

.... =

i B=Mcximum H Volume to be vented (3.05?-Cent. H; Cententration)X A i

100S?

A t

5?"

j:.2 1500-RCS

-PRESSURE (PSI)

.':=

1000-VENTING PERIOD = 8 /C_

=

500 -

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1000 2000 3000 4000 5000 6000 HYDROGEN FLOW RATE (SCFM) 5 of 5

ATTACHMENT II 7

4.0 ADDIT 10RAL INFORMATION FOR PLANTS WlTHOUT A L

g3 REACTOR ATSSEL 'LE til INSTRUMENTATION SYSTEM

.=

The inforration provided herein contains a rethod for ' detecting and sizing voids in the RCS.

No discrimination between voids in the reactor j

,g vessel and voids in the steam generators can be made. For plants

.((.[.

without a reactor vessel level system, this method can serve 'a critical

~

safety acnitor function, as well as confirming the success of void removal operations.

fh If gases are present in the reactor coolant system, then the pressurizer,

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pressure and l'evel controls will not respond as they normally' wouid.

The total gas volume can be estimated by performing a routine pressur-i~zer control operation and then. comparing the expected.esults with the actual results.

This is the technique utilized in the following steps.

If the safety infection system is in service, then the following steps are not applicable since normal pressurizer control will not be main t ained.

The recommended steps, followed by a brief explanation if needed, are given below.

5?5h 1.

Achieve a constant pressurizer level and pressure condition, with ncrmal controls being maintained.

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.

System pressure and level are placed on trend recorders to achieve

,g;g; 6etter accuracy for, i-ecording their values. The transient is not 557" expected to exceed a 150 psi.or 10% of span change in RCS conditions, fI5N:

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FR-1.3 13 E316T:1

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3.

Record th'e following parameters.

NEE' i =.

~=

RCS Pressure PSI PZR Level

=

~

Charging Rate

' =

.GPM

li Seal Injection Flow =

GPM 5

Seal Leakoff Low GPM

=

Time

=

ga These recordings. will become the initial paramete s in the following D

Calculation.

4 Isolate the RCS letdown flow, turn off all pressurizer heaters, and terminate the pressurizer spray by placing the spray control in,

manual and zeroing ~ the demand signal.

A condition is established where the pressurizer level will change only as a result of mass being injected into the RCS.

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 PZR Level

=

Time

=

These recordings will become the final parameters in the following

'EF calculation.

. re-

• e 7.

Reinitiate RCS letdown flow and restore normal pressurizer pressure and level control.

b!I?

=.

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FR-1.3 14 8316T :1

8.

Calculate the.init,ial-ana'fina.1-pressurizer. vapor space volumes.

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-Initial vapor Volume = (1-PZR Level % X Total Cylindrical PZR Vol. FT*3) ;

3 (Upper Spherical' Volume FT )

3 FT

=

F inal vapor Volume

= (Initial' Volume) + (a PZR Level X Total Cylincrical Volume *)

3 FT.

=

jf."

• Pressurizer volume less upper ano lower spherical dome volumes.

9.

Determine the total charged volume into the RCS.

-Chargeo volume = (Charging + 5eal Injection - Seal Leakoff GPM) X 1-(Time) X (

ggg) 7.453 FT

.&. E. G..

3:

FT

=

10. Determine the expected pressurizer level change.

3 100%

Expected a level = (Charging Volume FT ) y (

3)

Total P2R Volume FT

=

x. ::_

y,y

.'.'...E.

v;- v:=

. =.b..

.."T."

' "*ll

• F R-1.3 15 8316T:1

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11. If the actual' pressurizer level change is less than the expecteo

,===

level change then a gaseous voio exists in th5 reactor coolant system. Perform the following step to ceterniinc, tne volume df the RCS voia.

b 7=F If the actual pressurizer. level change is less than the expecteo

~

change (or if no level change was witnessed) then gaseous voios

~

exist in the reactor coolant system. This is_a result of the

_. = _

gaseous voids contracting when the pressure was increased by the

} $

charging flow. This will limit or prevent a normal pressurizer level increase. The void contraction may even be large gnough to cause an actual decrease in the-pressurizer level.

Step 12 should then be performed to estimate the' total. volume of the gas voios in the RCS.

12. The initial and final RCS. gaseous void volumes can be calculateo from the following equations.

r==-

Initial RCS Voio =.(Initial vapor Volumeh-(Final vapor Volume')-(Chargeo volune)

) _ Initial Pressure )

Final Pressure

=-

FT3 j

Final RCS Void = (Wal (F inal Pressure}J y

X (In a

essum) 3 FT.

=

. e.:.

gg.

The RCS voic volume contraction is equal to.tne chanSe in pressurizer level converted to volume. Also the ratio of final voio vclume to initial voic volume is equal to the ratio of initial RCS tg pressure to final _RCS pressure. From these two equations the two unknonns (initial ano final RCS voio volume) can be cetermineo by inserting one equation into another. The initial voio volume is calcu'lateo first ano then fit int.o the volute / pressure ratio to I ' f5.

cetermine the f'inal_ void volume, m:-

2 ER ].3 _

16 8316T:1L

ATTACHMENT III U N I T l.

REFUELING PRES IZER CAVITY i

l REACTOR I

I VENT l

\\

\\

./

PRESSURIZER VENT i

_d

\\

1 REACTOR

. VENT.

I l

g UNIT P

i REFUELING CAVITY 1

I f

RCS VENT SYSTEM DISCHARGE POINTS NORTH ANNA UNITS 1 AND 2 4

. _ _ _ __ - - _. - _.. _ _ _ _ _ _ _ _