ML20116A034

From kanterella
Jump to navigation Jump to search
Rev 0 to Temp Vs Distance Profile for 10 RHR Line Containing Stagnant Water
ML20116A034
Person / Time
Site: Comanche Peak  Luminant icon.png
Issue date: 07/17/1996
From: Navas C, Wojcik L
TEXAS UTILITIES ELECTRIC CO. (TU ELECTRIC)
To:
Shared Package
ML20116A016 List:
References
ME-CA-0260-4077, ME-CA-0260-4077-R00, ME-CA-260-4077, ME-CA-260-4077-R, NUDOCS 9607250262
Download: ML20116A034 (23)
v • d • e


Text

- . ..

1 i

r ,

a 4

ATTACHMENT 3 TO TXX-96413 Calculation ME-CA-0260-4077, Rev. 0 4

e l

1 a

9607250262 960718 PDR ADOCK 05000445 P pg

EM -01 Figure 7.1 Page 1 of 2: Change Verification Checklist Comanche Peak Steam Electric Station CHANGE VERIFICATION CHECKLIST DOCUMENT: Calc.31E-CA-0260-4077 revJL Page1of  ?

l CHANGE CLASSIFICATION: CLASS I1 CLASS II NON-SAFETY INPUT /IMPACTREQUIRED FROM: YES NO REVIEWER /STAKEllOLDER COMPLETE ENGINEERi$GDISCIPLINES:( , ~ ^ G% "~ a  %  ; A s kf * % QH.??? RCWQg r K9%\

CIVIL ENGINEERING X CODES AND STANDARDS X ELECTRICAL ENGINEERING X INSTRUMENTATION & CONTROLS ENGINEERING X MECllANICAL ENGINEERING X NUCLEAR /MECilANICAL ENGINEERING ANALYSIS X PROCUREMENT ENGINEERING X SYSTEM ENGINEERING X ENGINEERINGIMPACTSr Jl ~ ' l 7 "% bl ,

l r

, h% % *" Q;, ' ,

CIVIL ENGINEERING SYSTEMS INTERACTION X CIVIL ENGINEERING - PIPING X l

l COMBUSTIBLE GAS CONTROL ENGINEER X CONTAINMENT ANALYSIS ENGINEER X j DIGITAL SYSTEMS ENGINEERING X l ENGINEERING ALARA COORDINATOR X ENVIRONMENTAL EVALUATION (STA-717) X ENVIRONMENTAL EQUIP. QUALIFICATION ENGINEER X FIRE PROTECTION ENGINEER X IIUMAN FACTORS ENGINEER X MAINTENANCE ENGINEERING (PROGRAMS) X MAINTENANCE ENGINEERING (TESTING) X _

MECHANICAL EQUIPMENT ENGINEERING (MOVS) X )). m .[ h k u h)yyy) R / L

'1//b/g MECHANICAL EQUIPMENT ENGINEERING (COATINGS) X i NUCLEAR ANALYSIS & FUEL X RADIATION ENVIRONMENT ENGINEER X RADIOLOGICAL ENVIRONMENTAL ENGINEER X l RADIOLOGICAL ACCIDENT ENGINEER. X SEISMIC EQUIPMENT QUALIFICATION X SITE FACILITIES ENGINEERING X ECE 5.09 01 Rev.6 Page 7.1-1 of 2 l

l l

Figure 7.1 Page 2 of 2: Change Verification Checklist EDCN -01 ,

Comanche Peak Steam Electric Station CHANGE VERIFICATION CHECKLIST DOCUMENT: Calc 31E-CA-D260-4077 rev.A Page 2 of 2 INPUT /IMPACTREQUIRED FROM: YES NO REVIEHER/STAKEll0LDER COMPLETE

~

l ENGINEERINGIMPACTS$CONTL%UED): ,,  :

SOFTWARE QUALITY ASSURANCE X STATION BLACKOUT ANALYSIS X SYSTEMS INTERACTION (MECHANICAL) ENGINEER X TORNADO VENTING ANALYSIS ENGINEER X X

l l

X X

' Q ll; > W N0l%ESGINEERINGIMPACTS:b .,' ,  ; & ,e ,

,Qh

! CIIEMISTRY X ELECTRICAL MAINTENANCE X INSTRUMENTATION & CONTROL MAINTENANCE X MECllANICAL MAINTENANCE X J l NUCLEAR TRAINING (SIMULATOR DESIGN) X l NUCLEAR TRAINING (PROGRAMS) X l OPERATIONS SUPPORT X OPERATIONS WORK CONTROL X OPERATIONS FIRE PROTECTION _ . _

PLANT SUPPORT QUALITY ASSURANCE / QUALITY CONTROL X RADI ATION PROTECTION X REGL1ATORY AFFAIRS X

! X X

X Comments:

I Prepared by: (print) Carlos A.Navas _ . _____ (sign) _ [dl,M Date: Jul-15-1996 __

Approved by: (print) Lynn.Wojcik _. __ _ _.__ _ .._ _ (sign) ___ [A.dh (_ ._ _ . _ Date: 7/[7h/o _

u v ' '

ECE 5.09-01 ,,

l i

Figure 7.2: Design Verificction Form

. Comanche Peak Steam Electric Station t

DESIGN VERIFICATION DOCUMENT: Cale. ME-CA-0260-4077 rev. O Page1 of1 AREA REQ'DT METHOD NO.

  • COMMENTS? VERIFIED BY:(print) y (sign) . DA TE Mechanical Design Yes b No $ Vt b }{l @ rj h [ bf ~7 g IOC Design No Electrical Design No Civil Design No l

l Nuclear Design No l

Other Desig t Verifier No I

! Comments:

l l

a t

Prepared by:(print) Carlos A Navas (sign) ._ M2 Date: July _15.1996_

i Approved by:(print) LymWojcik . (sign) __b/d/h<2[___ Date: ~7 /1.7/96__

  • DV Methods are as follows: 1 - Design Review,2 - Altemate Cdculation,D - Qualification Test.

I Rev 6

, Page 7.2-1 of I l

4

. 1 FIGURE 7.1 TU ELECTRIC ENGINEERING EDCN-01 CALCULATION COVER SHEET d CALCULATION NO.: ME-CA-0260-4077 d ORGANIZATION : PAGE1 CALCULATION TYPE: INEC RSN* TOTAL NO. OF PAGES 15__

REVISION fJO.: 0 DM MM FX SCF NONE DOES THE CALCULATION AFFECT A LICENSING DOCUMENT 7 - DISCIP_L_INE CS EE YES NO IF YES. ME IC 1 CORRESPONDENCE NO.: '

X lg Ioo CALCULATION CLASSIFICATION. JLEFECT:.Q UNIT NUMEER: d CONFIRMATION REOUIRED:

1 COMMON $ j CLASS I OR ll L_.l NON SAFETY _

2  % BOTH YES NO l TITLE: Temperaturexs.Mistance profHe for a 10" RHR line c.ontalning Etagnantwater.

i i

1LJ DESCRIPTION: Thelemperaturntprofilesersusdistancea:ausedby conduMinn on a 10" RHR line fonnadedlah l

l 200J_sourceJsAeterrnined. This informatinn it.uSeilO.Addressi'leImalitindglgAffalvet i

l DO EXISTING SUPPLEMENTS APPLY TO NEW REVISION 7 YES NO 13 } ASSOCIATED CALCULATION INFORMATION:

SUPERSEDES (SUP)/

TYPE NUMBER AND

, 1 NA NA NA l

l d AFFECTED CALCULATION INFORMATION-KIND TYPE NUMBER NA NA NA l

l 15_] - NA_ /A EE /A _NA__ /A l DESIGN CHANGE TRENDING CODE l

d 18)

RESPONSIBLE ENGINEFJt1S1 DATE: C ECKER DATE CadosANava /// " 7 i % ID INC[B D e -

_& .A.y.Lil, Q ) 71@L IL} 18j DISTRIBUTION: RESPONSIBLE ENGINEERING SUPERVISOR, DATE:

P_ C Chiu F 15 LynILY ojcik yd apaps ECE 5.03 REV. 4 I- _ __

4 i

! FIGURE 7.2 INDEX SHEET l

l TU ELECTRIC ENGINEERING l

CALCEAD NNO.: PAGE2

(

INDEX SHEET ME-CA4260-4077 PAGES REVISED PAGES ADDED PAGES DELETED

! REV.No.

i Cover sheet page I, Table of NA NA i contents page 3, computer log 0 sheet page 4, Body ofcalculat l pages 5 through 14 Attachment I- 1 page

{

t l

l I

l i

I i

l l

i

{

l ECE 5.03 REV. 4

( PAGE 7.2. I OF I

FIGURE 7.3 TABLE OF CONTENTS SHEET TU ELECTRIC ENGINEERING PA E NO. 3 TABLE OF CONTENTS CALCULATION NO. ME CA.0760-4077 REVISION NO.: O SECTION PAGE NUMBER CALCULATION COVER SHEET I INDEX SHEET 2 TABLE OF CONTENTS 3-OBJECTIVE OF CALCULATION 5 REFERENCES 6 ASSUMPTIONS 7 DESIGN INPUTS R EQUATION

SUMMARY

(OR METHODOLOGY) 9 BODY OF CALCULATION 10 RESULTS 11 CONCLUSIONS 14 ATTACHMENTS Att_1. I nage ECE 5.03 REV. 4 PAGE 7.3 - 1 OF l

-- ~ _- -

FIGURE 7.4 4

COMPUTER OUTPtTT/ MICROFICHE LOG SHEET ORGANIZATilON: parimring Analym CCN/ CALC NO.: un-cAMMW77 REV.o PAGE 4 COMPUTER RUN UNIQUE IDENTIFIER COMPUTER 1 HARDCOPY (H) -1 1 JOB 1 RUN DATE OR ADD / PROG. NAME 2 VERSION / LEVEL 2 LIBRARY NAME 1 j NUMBER MICROFICHE (M) DELETE i l

884 07/03/ % H ADD HEATING 6 002 HEATING 6 EXE:1 l

885 07/03/ % H ADD HEATING 6 002 HEATING 6.EXE:1 naq 07/14/06 M Ann MFATfNed W HFATTNC4 FYF.1 I

f t

l i

i l

T

, I

. r 4 I r

I i' f i

i i

t j '

6

[

t i

r I

  • or unique identification number r
1) Mandatory
2) Optional ECE 5.03 Rev.4 Page 7.4 - 1 of 1

4 Calculation Number: ME-CA-0260-4077 Revision Number: 0 Page Number: 5 Obiective of Calculation:

During the initiation of a Loss of Coolant Accident (LOCA) water from the RWST is injected to the cold leg of the reactor using the RHR system. Upon depletion of the RWST, water from the containment sump is cooled (initially to approximately 200 *F) in the RHR heat exchanger and injected to the cold leg of the reactor. Some hours later, the injection is switched over to the hot leg of the reactor. To accomplish this, valve 8716A (or B for the opposite train) is required to be opened. This closed valve located approximately 4 feet (5 feet in Unit 1) away from the flowing

- 200 "F water has been exposed to roo;n ambient and slowly heated by the heat conducted through the RHR pipe and stagnant water. There is a concern that thermal induced pressure locking of the valve can occur due to the increase ofits temperature.

The objective of this calculation is to determine the temperature versus distance profile for a 10 inch schedule 40 RHR pipe filled with stagnant water from the point where it connects to a 200 *F temperature source (refer to the design input section of this calculation for the selection of 200

  • F). A conclusion is then drawn regarding the temperature rise due to this conduction process.

These results are then utilized by the MOV group to address the potential thermal induced pressure locking of the valve (see schematic below).

l l

4 4 feet y l 200 degrees F Stagnant water NValve 8716A Y

10" RHR line /

/

}

l

t ,

( Calculation Number: ME-CA-0260-4077 Revision Number: 0 l

Page Number
6 l

References:

l I

1. Heat transfer third edition Alan J. Chapman l
2. Calculations RXE-LA-CPX/0-018 rev.1 RXE-LA-CPX/0-015 rev. 2
3. HEATING 6, a program which allows multidimensional heat conduction analysis with the finite difference formulation. Design verified via RXE-TA-CPX/0-30 rev. O " Verification and Validation of the HEATING 6 code VAX Installation" D. Hiltbrand. Executable module HEATING 6.EXE;l dated June 14,199310:31:37.56. >
4. Crane technical paper no. 4101979.
5. Flow Diagram M1- 0260 rev. CP-25
6. BRP-RH-1-SB-009 rev. CPI f
7. DBD-hE-302 Rev. 4  ;
8. Specification MS-30 rev. 2
9. Flow Diagram M2- 0260 rev. CP-12
10. BRP-RH-2-SB-011 rev. CP4
11. BRP-RH-2-SB-015 rev. CP5
12. BRP-RH-1-SB-008 rev. CP1 l l l

7 e

Calculation Number: ME-CA-0260-4077 Revision Number: O Page Number: 7 Assumptions:

1. Radiant heat transfer from the surface of the insulation to the room surroundings is ignored, this is conservative.
2. Assume the convective heat transfer is natural and laminar.
3. Assume the pipe is horizontal. The heat transfer coefficient for a vertical pipe is greater, therefore this assumption is conservative.
4. Heat transfer through the water is assumed to occur by conduction only. This is a '

simplifying assumption used to model stagnant water. The water will actually move due to the difference in its temperature and some natural convection will be encountered. This assumption is considered acceptable in light of other conservatism.

t r

l 4

.r m-v -

Calculation Number: ME-CA-0260-4077 Revision Number: 0 Page Number: 8 Design Inputs:

1. RHR line description obtained from references 5, 6, 9,10,11,12,
2. Pipe diameter dimensions for schedule 40 pipe obtained from reference 4.

L 3. Insulation thickness (1.5 inches class B2) reference 8

4. ~ Insulation materialis calcium silicate reference 8
5. The fluid temperature of 200 *F is expected to the maximum bounding temperature where ,

cold leg to hot leg injection switchover could occur. This temperature is obtained from [

reference 2 and is based on the leaving temperature of the RHR heat exchanger following i entry to the recirculation phase of a LOCA. (when the containment sump waters are at the <

highest temperatures). Note that cold leg to hot leg switchover occurs later in the  !

transient when sump temperatures are cooler. Therefore, the selection of this temperature  ;

is conservative.  :

l l

l l

j l

4 1

l l

l l

Calculation Number: ME-CA-0260-4077 Revision Number: 0 ;

Page Number: 9 5

i Eaustion summary (or Methodolorv):

1. Simplified heat transfer coefficient for natural convection (horizontal cylinders):

h = 0.27( )*2' Reference 1 page 385' Where: h = heat transfer coefficient BTU /hr/ft'PF)

At = temperature difference betweenpipe surface androom environment.

[ D = pipe externaldiameter (ft.)

i l

I I

9

t.

! Calculation Number: ME-CA-0260-4077

Revision Number
"

0 i l Page Number: 10 l l \

Body of Calculation:

l A two dimensional HEATING 6 (reference 3) model in cylindrical coordinates is constructed to l evaluate the temperature versus distance profile.

The modelis described as follows:

The pipe ID = 10.02 inches (ref. 4). Therefore r = 10.02/2/12 = 0.4175' 1 The pipe OD = 10.75 inches (ref. 4). Therefore r = 10.75/2/12 = 0.4479' Boundary condition 2 0.573' _ k Insulation region No.3 0.4479' Pipe wall region No.1 A 0.4175' M Boundary I condition 1 Stagnant Water Region No. 2

  1. [ I 0.0' _

l l 0.0' 20.0*

l R

Boundary condition 1 = fixed temperature at 200 deg F A

Boundary condition 2 = Naturn! convection

>z i I  !

l l I

1 i

i

4 Calculation Number: ME-CA-0260-4077 Revision Number: 0 Page Number: 11 20 feet of pipe is modeled, previous experience indicates that the pipe surface temperature will be at room ambient temperature well before 20 feet.

In order to bound the maximum temperature increase (from initial conditions) 2 runs are performed as follows:

o The room ambient air temperature as well as the stagnant initial water temperature are selected at 40 deg F. This is the minimum normal operating temperature for the safeguards building. (ref. 7) o The room ambient air temperature as well as the stagnant initial water temperature are selected at 122 deg F. This is the maximum normal operating temperature for the safeguards building. (ref. 7)

An additional run is performed using 70 "F environment, this run is made to be more representative of plant conditions and be conservative (cool).

Water properties selected are as follows:

Thermal conductivity = 0.392 BTU /hr/ft/"F at 200 "F to maximize conduction ref.1 pg 586 Density = 62.4 lbm/ft' and specific heat = 1.0 BTU /lbm/ F (These 2 terms are not used since this ic a steady state mn)

The pipe is stainless steel (ref. 5 and 6) from ref 1 page 576 select the thermal conductivity for carbon steel: 31 BTU /hr/ft/ F Note that this is very conservative since the conductivity of stainless steel is approximately one third that of carbon steel.

Density 489 lbm/ft' and C, = 0.11 BTU /lbm/ F ( again these two are not required)

The heat transfer coefficient for boundary condition 2 is determined as follows:

h = 0.27(Atp2s = 0.261 (At)a2s (13.75/12)a2s Therefore the coefficients required by HEATING 6 for the convective portion are 0.261 and 0.25 exponent.

t-

L l

Calculation Number: ME-CA-0260-4077 Revision Number: O Page Number: 12 The thermal conductivity for the insulation is obtained from attachment 1. K= 0.35 BTU-in/(hr-ft 2'F). Again the density and specific heat are not used but entered as 12 lbm/ft' and 0.2 BTU /lbmf'F The following is the input deck for the HEATING 6 Model.

Input listing for the 40 deg F case:

& OPTION MAXPTS=25000,MAXREG=11,MAXBDC=6,MAXZFG=80,MAXGGL=18,HGEN=F, IPLOT=1,&END ,

RER temperature profile ambient at 40 F 20000 3 1 0.0 0.0 0.0 0 0 0 100 REGIONS

'l 1 0.4175 0.4479 0.0 0.0 0.0 20.0 10000012 2 2 0.0 0.4175 0.0 0.0 0.0 20.0 10000012 3 3 0.4479 0.573 0.0 0.0 0.0 20.0 10022202 MATERIALS 1 STEEL 31.0 489.0 0.11 2 WAT 0.392 62.4 1.0 3 INSU 0.0292 12.0 0.2 INITIAL TEMPERATURES l'40.0 BOUNDARY CONDITION '

1 2 200. 000 2 1 40.0 0 0 0 0.0 0.0 0.261 0.25 ,

XGRID

0. O.4175 0.4479 0.573 322 ZGRID 0.0 5.0 10.0 20.0 10 5 5 STEADY-STATE PARAMETERS 10000 The temperature profiles can be seen on the following page.

l .

Calculation Number: ME-CA-0260-4077 Revision Number: 0 Page Number: 13 Results:

Pipe temperature profile 200 i 1

,g 175- 'i Iid.

150 E,'s^s

h.
  • s
u. gs, N ,

l p25 g '-

r---

8  %

100 \, ,

m 3 .

E \ .'*.,_ l 4 75 gx ---

Legend 40 deg 25 - ----

122 deg

- --- 70 deg ,

0 j' i 0 5 10 15 20 Distance feet I

.. 1 l

i Calculation Number: ME-CA-0260-4077 Revision Number: 0 o . Page Number: 14 i

]

i

Conclusion:

)

i 1

i l The greatest temperature increase occurs when the ambient and the initial fluid temperature are - .!

colder. (40 dcg F) l L To account for the uncertainties associated with the partial mixing of water in the vicinity of the l tee where the 200 T water is in contact with the stagnant water, it is assumed that the 200 T i water migrates a full foot into the stagnant pipe (this is conservative).

i This can be accomplished by obtaining the temperature of the pipe 3 feet into the stagnant water i l (instead of 4 feet). The temperature at this point (82.3 T) corresponds to a 42.3 T temperature  !

rise above ambient.  :

t Run Temperature @ 3 ft. AT above ambient l 122 T- 140.9 7 18.9 7 .

70 7 104.5 T 34.5 T .

40 7 82.3 7 42.3 7 l ~i r  !

This calculation is very generic smce it detemtines temperature versus distance. This calculation .

can be used for both Units since the containment sump temperatures following a LOCA, the j RHR lines and insulation are the same. (references 2, 5, 6, 9,10,11,12)  :

i l'

i-I

.ATMc&t^

L To ckwurnou m*- cA- O tw.- 40 77 tze v, o j . ,9g, 3pecificatisn Data Thermo-12 ~

Pipe and Block Insulation N/

Physical Properties Surface Buming Characteristics Density (dry) Average 14 lbs per cu ft When Tested to ASTM E 84 Flexural Strength (based on 1W thickness 60 psi Flame Spread of block tested en 0 Smoke Developed 0 accordance with ASTM C 203)

Compressive Strength 200 psi to produce 5%

(based on 1W thickness of block) ccmpression Thermal Conductivity (k)'

Unear Shrinkage 1.1% after 24-hr soaking *- -

period at 1200*F g om Maximum Service Temperature 1200*F yir om -

Compilance with Outside Specifications 5: *.

Pipe and BlockInsulation g& M m

ASTM C 533, Type I I'j oco_

~

-- p o #

ASTM C 130 9 *Eo 4oow "

ASTM C 795 --

MIL-t 24244 a, MIL-t-2781E to 1200'1"(pipe) ig o.uu MIL l-2819F (block) o.io Class 2 to 1200*F .

U.S. Coast Guard Certificate of Approval 164.009/163/0

  • o too e I

soo soo

. NRC 1.36 Mean Temperature (*F) r., , ,v..e4m

.,,,,.ew,e,,, ,, esme,rra e.,u, N Pre se an,6SN c S18 Raru Nest Mene

'/

When ordering material to compty with any govemment specification, a statement of that fact must appear on the purchase order. Govemment regulatrons prohibit the certtfication of c:r>m-pliance after shipment has been made.

VJarranty Limitation of Liability We warrar't tt et our products are manufacturvd in accorcunce with our applicable motcrial ow.irwas and are free frum defec:s in Manville makes no representation or warrar.ty of any kind. express workmanship and matertats using our specmcanons as a standard, or irnpried, in fact or in law, including without limitation, the warranty Every claim under this warranty shall be deemed waived unless in of merchantability or the verranty of fitness for a particular purpose, other than the limited warranty set forth herein. Manvitta snari not writing and received by Murrville witnan tniny (30) cays of the date be flacle for any inex! ental. consequential, or other damages for the defect was discovered or should have been discovered and within one (1) year of the date of shiprnent of the product. any alleged negligence, brea::h of warranty, stect liabill:y or any otner theory.

District Offices Soutti Central Manville Canada,Inc.

Manville For information on other Eastern and Midwest 295 The West Mall Manville Insutations and Manvill, 3446 Lang Road Etobicoke, Ontarto M9C 4Z7 systems, write Manville 1850 East Main Street Houston. TX 77092 416-626-5200 Product Information Center.

St. Chartes. IL 80174 713-683-7116 Teler: 06-984559 RQ Box 5108. Denver, CO 312-377-7850 80217-5108, or cad Western For export Southessg MMo 303-9 4 2000 ,800-654 3103 or RQ B x 5100 ,yypg73,49oo, Manville Tblex:21ti115 MANV UR RQ Box 105545 Denver, CO 80217-5108

. Atlanta, GA 30302 303 976 4900 404-449-3300 l

1 -

! gd The phys; cal (or chcrnican properties of Thermo-f 2 Pipe used Block l

i -%ms. Insulation represent typicar average values oprained in accordance wtm artarited test motbode and aro cubject to normal manuf actv-

Mariville ing variations.

.uhiect to cnse,e -hou, They are notice. supplied

~umerica al service and are V, as a techn,ic,iamo s,,ead P.O Box 5108 not intended to ref:ect hazards presented by this or other materiale Denver, CO 80217 5108 under actua! fire conditinns. Check ene Manvillo district office to assure current inforrnation.

ING.3014 $.M l m itewiUsA l

I

I b -

4 i

1 i

i 1

3 i

4 ATTACHMENT 4 TO TXX-96413

EXCERPTS FROM CPSES OPERATOR TRAINING MODULE

J FOR " EQUIPMENT OPERATION" ,

! (MATERIAL CODE OPD1.ADM.XAD) I i

1 i

. i o

J

EXCERPTS FROM CPSES OPERATOR TRAINING MODULE FOR EOUIPMENT OPERATION" l (MATERIAL CODE OPD1.ADM.XAD)

SOER 84 07, " Pressure Locking and Thermal Binding of Gate Valves".

l SOER 84-07 provides informathn on Gate valve problems at Big Rock Point.

LaSalle 1, St.Laurent B 1, and San Onofre I Power Stations. These event involved inoperability of specified valves due to thermal binding or l pressure locking.

At Big Rock Point, a Boiling Water Reactor (BWR), three of the four Reactor

, depressurization valves failed to open during surveillance testing. These L valves are air operated flexible wedge gate valves.

l Failure of these valves was due to valve disc wedging into the valve seat resulting in insufficient air and spring operating force to open valves. Binding was determined to be a combination of previously increasing air pressure to improve valve closure l characteristics and closing the valves followed by a system cooldown. During cooldown the valve body contracts more than the valve disc causing pinching of the disc in the valve seat.

l At La Salle, the Residual Heat Removal system inboard suction valve failed to open either via the motor operator or in manual.

Failure was determined to be the result of manually backseating the valve during the previous operating period to stop leakage.

With the plant in Hot Shutdown and terrperatures less than when the valve was manually seated, failure to open was experienced due to thermal binding of the valve. Valve was opened by externally heating the valve body.

On two other separate occasions a RHR Heat Exchanger Outlet valve failed to open by either motor operator or manually. This is the same type of valve as the RHR suction valve discussed above. It was determined that the valve failed due to high pressure water being trapped in the bonnet cavity which does not have a mechanism to vent the cavity area.

At Saint Laurent B 1, a French PWR, two valves in the RHR suction path failed to open due to high pressure inside the valve bonnet cavity.

j Failure was determined to be due to leakage past the upstream disc

allowing bonnet cavity to reach primary press are. When primary j pressure was reduced, the high pressure - water in the valve bonnet was trapped causing the disc to press tightly against the valve seats preventing valve operation.

I 1

l l

! At San Onofre 1. both trains of a Safety Injection were inoperable during ,

l an actual Safety Injection condition due to two Anchor Darling valves which

! could not be opened.

Failure of the valves to open was determined to be high pressure ,

water trapped in the bonnet cavities. The trapped high pressure caused excessive differential pressure to develop disc-to-seat forces sufficient to prevent valve operation.

Sianificance 1

Significant Safety. concerns are raised due to binding of gate valves from bonnet pressurization or thermal binding for the following reasons:

These valves are used in a variety of applications in Nuclear Power Plant Safety Systems.

Valves may be required to open during or immediately following i postulated design basis events.

Events which most severely challenge plant safety usually involve most l rapid system cooldown and depressurization rates and the largest pressure differentials in and across the valves. i Analysis and Discussion of Gate valve oroblems 1 i

Thermal Binding occurs because of differences in the contraction rates of ,

the valve body and the valve disc. If the valve is closed when hot and J subsequently allowed to cool. the difference in thermal contraction . '

causes the seats to bind the disc so tightly that reopening is impossible until valve is reheated. Excessive closing force can also contribute to l thermal binding which causes the disc to be driven into the seat more i tightly and any subsequent cooling effects are increased. Excess closing i force could be the result of improper manual operation. excessive air pressure to the valve operator or misadjustment/ defective motor operator torque switches. ,

Bonnet pressurization results when the gate valve is closed with the system full and leakage into the bonnet cavity takes place. If the valve .

disc / seat and packing seal is sufficient. then high pressure buildup in the  !

cavity can occur. This trapped high-pressure fluid can cause valve failure due to:

l . Differential Pressure Lockina may occur in gate valves due to

differential pressure across the disc in he closed position. The
pressurized side of the flexible disc can move away from its seat l slightly allowing high pressure liquid to enter the bonnet cavity.

With time. bonnet pressure will equalizing with pressure in the body cavity. If pressure in the body is then decreased the bonnet i

pressure will force the disc against its seat. If no pressure equalizing path is provided for the bonnet, pressure locking may then occur.

Liouid Entraoment may occur when the system including the valve bonnet is full of cold liquid with the valve closed. As system temperature is increased, the bonnet liquid temperature,-

increases resulting in potential high pressure. (In theory, a one degree increase in temperature of a trapped liquid could result in an increased pressure of 100 psia). It should be noted that the

! valve does not have to be in a hot system, close proximity where

heat conduction will heat the. valve bonnet liquid could have the j same result.

l

SUMMARY

l Events involving gate valves in Safety Related systems have resulted in '

failure of the valves to open due to valve disc binding. These failures '

were due to either differential thermal contraction or high pressure water i trapped in the valve bonrat cavity.

RECOMMENDATION-l Personnel training should include instructions on valve failure mechanisms, including how to diagnose the failure mechanism and the action necessary to recover from the failure.

At CPSES the gate valves for the Containment Sump suctions to the RHR pumps and the Containment Spray pumps have had relief valves installed to relieve ,

the pressure between the two valve discs. The relief valves are set at .  :

approximately 76 psi for the CT valves which relieve to the suction of the CSP, and 470 psi for the RHR valves which relieve to the suction of the RHR '

pumps..

CPSES ASSESSMENT OF RECOMMENDATION Training Department has committed to include this SOER recommendation into all applicable training materials. This Lesson Note' satisfies this training requirement.

l l

i 1

Retrieved from "https://kanterella.com/w/index.php?title=ML20116A034&oldid=2912748"