ML20097F940
| ML20097F940 | |
| Person / Time | |
|---|---|
| Site: | Vogtle  |
| Issue date: | 02/08/1996 |
| From: | Mccoy C GEORGIA POWER CO. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| GL-95-07, GL-95-7, LCV-0681-B, LCV-681-B, NUDOCS 9602200255 | |
| Download: ML20097F940 (32) | |
Text
i U,,
Georgia Power Company 40 inverness Center Parkway Ppst Omce' Bon 1295 Birm.ngham. Alabama 35201 Telephone 205 877-7122 m
Georgia Power C. K. McCoy Vice Presdent, Nuclear Vogtle Project the Southem etwtnC System February 8,1996 LCV-0681-B Docket Nos.: 50-424 50-425 U. S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, D. C. 20555 Gentlemen:
VOGTLE ELECTRIC GENERATING PLANT GENERIC LETTER 95-07 PRESSURE LOCKING AND THERMAL BINDING 180-DAY SUBMITTAL The U. S. Nuclear Regulatory Commission (NRC) issued Generic Letter 95-07," Pressure
..9 Locking and Thermal Binding of Safety-Related Power-Operated Gate Valves" on August 17,1995. The letter requested that licensees identify any safety-related power-operated gate valves which may be susceptible to either pressure locking or thermal binding and that licensees perform additional analyses and take appropriate actions, as required, to ensure that susceptible valves are capable of performing th-ir design-basis ftmetion. Georgia Power Company has completed the engineering evaluations requested in the generic letter for the Vogtle Electric Generating Plant (VEGP). The enclosed document summarizes the results of those evaluations.
As a result of this review, it was determined that a number of valves may be susceptible to pressure locking and/or thermal binding. Operability determinations were performed for those valves which may be susceptible to ensure that the valves will be capable of performing their design-basis functions in their current configurations. In addition, a l
total of 16 valves were identified for modifications to provide additional assurance that j
the valves will be capable of performing their design functions in the future. The valves l
to be modified, the associated madifications, and an implementation schedule are outlined in the enclosure.
I 20C058 Vh 9602200255 960208 A
PDR ADOCK 05000424 P
PDR f/t
e.
- a
/*
t 3
U. S. Nuclear Regulatory Commission Page 2 Should you require any additional information regarding this response, please contact my ofrice.
l Sincerely, i
C. K. McCoy CKM/HET/het Enclosure xc:
Georgia Power Comnany Mr. J. B. Beasley, Jr.
Mr. M. Sheibani NORMS U. S. Nuclear Regulatory Commission Mr. S. D. Ebneter, Regional Administrator Mr. L L. Wheeler, Licensing Project Manager, NRR A.k C. R. Ogle, Senior Resident Inspector, Vogtle i
LCV-0681-B l
l i
Vogtle Electric Generating Plant Generic Letter 95-07 Pressure Locking and Thermal Binding 180 Day Response February 1996
l
' t.
- y v
j' l
TABLE OF CONTENTS l
I.0 INTRODUCTION 2.0 SCRELNiNG EVALUATION 3.0 POTENTIALLY SUSCEPTIBLE VALVE EVALUATIONS 3.1 R11R Pump Miniflow Valves 3.2 Turbine Driven Auxiliary Feedwater Pump Steam Admission Valves 3.3 Pressurizer Power-Operated Relief Valve Block Valves l
3.4 RHR Loop Suction Valves (Pump Side) 3.5 RHR Loop Suction Valves (RCS Side) 3.6 RHR to RCS Hot-Leg Isolation Valves 3.7 Boron Injection Tank Discharge Isolation Valves 1
3.8 S1 Pump to RCS Hot-Leg Isolation Valves 3.9 RHR Pump Containment Sump Suction Isolation Valves 3.10 RHR to RCS Hot-Leg Isolation Valves 3.11 Containment Spray Pump Discharge Isolation Valves 3.12 Containment Spray Pump Containment Sump Suction Isolation Valves 4.0 MODIFICATIONS i
1
.a
,s 1
1.0 INTRODUCTION
The U. S. Nuclear Regulatory Commission (NRC) issued Generic Letter 95-07, i
" Pressure Locking and Thermal Binding of Safety-Related Power-Operated Gate Valveson August 17,1995. The letter requests that licensees identify any safety-related power-operated gate valves which may be susceptible to either pressure locking or thermal binding and that licensees perform additional analyses and take appropriate actions, as required, to ensure that susceptible valves are capable of performing their design-basis function. Georgia Power Company has completed the engineering evaluations requested in the generic letter for the l
Vogtle Electric Generating Plant (VEGP) and this document summarizes the results of those evaluations and identifies actions which will be performed to provide additional assurance that safety-related power-operated gate valves will be capable of performing their design-basis function.
The initial step in performing this evaluation was the development of a list of all safety-related power-operated gate valves in service at VEGP. The list of valves was developed based on a review of P& ids, applicable FSAR tables, Generic Letter 89-10 documentation and the Inservice Test Program. A total of 190 valves were identified for further evaluation in conjunction with this review.
Following a determination of the scope of valves covered by the generic letter a screening criteria was developed to identify valves which were potentially susceptible to pressure locking and/or thermal binding. The objective of this step was to eliminate valves which were not susceptible to these phenomenon and to concentrate the remaining efforts on the valves which were determined to be potentially susceptible.
The valves which were determined to be potentially susceptible based on the screening process were evaluated in detail. In cases where the detailed evaluations concluded that pressure locking or thermal bin ing could occur, d
operability determinations were performed to ensure that
. ilves were capable of performing their design-basis function, and corrective actions were identified to provide additional assurance that the valves would be capable of performing their design functions in the future.
1-1
9 vi
/
j 2.0 SCREENING EVALUATION Criteria were developed to support the initial screening of the 190 valves covered by the generic letter for potential susceptibility to pressure locking and/or thermal l
binding. The objective of the screening process was not to identify valves which were susceptible, but rather, to eliminate valves which were clearly not susceptible. Valves which were not screened out in this process were considered to be potentially susceptible and required a detailed engineering evaluation.
Figure 2-1 outlines the flowchart which was utilized in performing the preliminary screening. The criteria which was identified for use in this screening process is relatively simple and straight forward. Criteria B-1 and B-2 are the basic criteria aimed at determining if the valve is associated with a water or steam system and if the valve has an active safety function to open. Following the basic criteria the flowchart splits to address thermal binding and pressure locking independently.
It should be noted that valves which do not have an active safety function to open were determined to be not susceptible to pressure locking and/or thermal binding when performing their safety function based on criteria B-2. However, normally open valves which have an open safety function were evaluated further to ensure that surveillance testing related activities would not introduce potential susceptibility for valves which are considered to be operable during testmg.
There were no surveillance test scenarios identified for normally open valves which resulted in potential susceptibility.
Criteria TB-1, TB-2 and TB-3 screen the valves for susceptibility to thermal binding. For the purposes of this evaluation, a valve was considered not susceptible to thermal binding if the valve was not exposed to a process fluid temperature exceeding 200* F. In addition, a flexible wedge gate valve was considered not susceptible if the maximum temperature decrease following closure and prior to opening did not exceed 100* F. It should be noted that there were no solid wedge gate valves identified in conjunction with these reviews.
These quantitative screening criteria were developed in conjunction with the Westinghouse Owners Group (WOG) Pressure Locking and Thermal Binding Task Team. The basis for this criteria is documented in Westinghouse letter ESBU/WOG-95-387, dated December 6,1995.
Criteria PL-1, TPL-1 and HPL-1 screen the valves for susceptibility to pressure locking. There were no quantitative criteria utilized in screening the valves for this phenomenon. ' For a valve to be excluded from susceptibility to thermally induced pressure locking it must be determined that the valve will not be required to open following a rapid increase in valve temperature due to process fluid or environmental conditions. Normal ambient temperature changes were not 2-1
,s s
considered relative to this phenomenon. For a valve to be excluded from susceptibility to hydraulic pressure locking, it must be determined that the valve
- will not be required to open following a rapid depressurization upstream or downstream of the valve. Although no specific minimum pressure was established relative to this review, in general, pressures below approximately 100 psig were not considered significant relative to hydraulic pressurc !ceking.
Table 2-1 identifies the 190 valves screened in conjunction with this review and the criterion for eliminating the valves which were determined to be not susceptible to pressure locking and/or thermal binding. The pressure locking and thermal binding fields are shaded for valves which were eliminated as a result of -
the basic criterion B-1 or B-2. Valves which were not eliminated by the basic l
criteria were evaluated further and blank fields under the pressure locking and/or thermal binding columns indicate potential susceptibility. Valves which were not eliminated from susceptibility in conjunction with this screening process were considered to be potentially susceptible to pressure locking and/or thermal binding, and detailed evaluations were performed for these valves.
I l
2-2
f Figurs 2-1 Pressure Locking and Thermal Binding Screening Evaluation Flowchart B-0 All Power Operated Safety Related l
Gate Valves.
l lf B-1 No Is the Process Medium g
Steam or Water?
Yes Thermal Binding Susceptibility lf Pressure Locking Susceptibility Yes B-2 Does the Valve Have an Active Safety Function to Open?
Yes 1
)f No 1f No TB-1 lit -
- Quit, is the Valve Exposed to Fluid Temperatures Greater than 200 Degree F?
lf Yes PL-1 No
[
Does the Valve Have a Flexible,
> Quit i
I Split or Double Disk Wedge?
No TB-2
- Quit, Does the Valve Have a Yes Solid or Flexible Wedge?
f I
Yes Jf TPL 1 HPL-1 j
=
TB-3 ls the Valve Required to No Is the Valve Required to No l
is the Valve Required to Open Open Following a Rapid y
Open Following a Rapid No After a Temperature Drop of:
Temperature increase Quit Depressurization of the Quit
}
Quit '
Due to Process Ruid or Piping Upstream or Solid Wedge > 50 Degrees F Environmental Conditions?
Downstreamof theValve?
Flex Wedge > 100 Degrees F Yes Yes Yes lf lf The Valve is Potentially Susceptible The Valve is Potentially Susceptible The Valve is Potentially Susceptible to Thermal Binding.
to Thermal Pressure Locking.
to Hydraulic Pressure Locking.
Expanded Evaluation Required.
Expanded Evaluation Required.
Expanded Evaluation Required.
2-3
y v
i Table 2-1 Pressure Locking and Thermal Binding Screening Evaluation Summary Tag No.
Valve Description Screened Out By Criterion:
Basic l Pressure Locking l Therm. Bind.
l liydraulic l Thermal l
I FV-0610 RilR Pump i Minillow l
l l TB-3 I FV-061 i RilR Pump 2 Minillow
' B-3 liiV-0780 Normal Containment Sump Pump Discharge B-2 lilV-0781 Normal Containment Sump Pump Discharge B-2 I HV-10957 Sludge Mixing Isolation to RWST B-2 lilV-10958 Sludge Mixing Isolation to RWST B-2 j
lilV-12975 Containment Air Radiation Monitor inlet B-1, B-2 liiV-12976 Containment Air Radiation Monitor Inlet B-1, B-2 lilV-15196 Feedwater Bypass isolation to SG B-2 l HV-15197 Feedwater Bypass isolation to SG B-2 lilV 15198 Feedwater Bypass isolation to SG B-2 l
lilV-15199 Feedwater Bypass isolation to SG B-2
)
tilV-19051 Thermal Barrier Supply isolation B-2 lilV-19053 Thermal Barrier Supply isolation B-2 IHV-19055 Thermal Barrier Supply isolation B-2 lHV-19057 Thermal Barrier Supply isolation B-2 l
tilV-2041 Thermal Barrier Return Isolation B-2 tilV-27901 Fire Protection lleader Cont. Isolation Pen 40 B-2 lilV-3006A Main Steam isolation Valve B-2 lilV-3006B Main Steam isolation Valve B-2 IHV-3009 Steam to AFW Pump Turbine B-2 tilV 3016A Main Steam Isolation Valve B-2 liiV-3016B Main Steam isolation Valve B-2 lilV 3019 Steam to AFW Pump Turbine B-2 tilV-3026A Main Steam Isolation Valve B-2 lilV 3026B Main Steam isolation Valve B2 IHV-3036A Main Steam isolation Valve B-2 Il1V-5106 Steam to AFW Pump Turbine PL-l tilV-5229 SG Feedwater Isolation B-2 liiV 8000A Pressurizer PORV isolation llPL-1 TPL-1 lilV-8000B Pressurizer PORV isolation HPL-1 TPL-1 IHV-8105 Charging Pump to RCS isolation B-2 1IIV 8106 Charging Pump to RCS isolation B-2 liiV-8146 Charging Pump to RCS isolation B-2 tilV-8147 Charging Pump to RCS isolation B-2 tilV-8438 Charging Pump B Discharge Isolation B-2 liiV-8471 A Charging Pump A Suction isolation B-2 2-4
?
Tag No.
Valve Description Screened Out By Criterion:
Basic Pressure Locking l Therm. Bind.
Ilydraulic l Thermal l
Charging Pump B Suction isolation lilV-8471B B-2 lilV-8485A Charging Pump A Discharge Isolation B-2 lilV-8701B RilR Loop 1 Suction isolation l
l lilV-8702A RilR Loop 4 Suction isolation l
l lilV-8702B RilR Loop 4 Suction isolation l
l lilV-8716A RilR to RCS Ilot Leg isolation l
l TB-3 lilV-8716B RilR to RCS Ilot Leg isolation l
l TB-3 lilV 8801 A Boron injection Tank Discharge isolation l
l TB-3 t ilV-880lB Boron injection Tank Discharge isolation l
l TB-3 tilV-8802A St Pump to RCS Ilot Leg isolation l
l TB-3 lilV-8802B St Pump to RCS Ilot Leg isolation TB-3 tilV-8803 A Boron injection Tank Inlet isolation B-2 lilV-8803B Boron injection Tank Inlet Isolation B-2 lilV-8804A RilR litx Train A to Charging Pumps llPL-1 TPL-1 TB-3 V 8804B _
llPL-1 TPL-l TB-3 lilV-8807A RilR to St Pump Suction isolation llPL-1 TPL-1 TB-3 lilV-8807B RilR to S1 Pump Suction isolation HPL-l PL-l 3
t ilV-8808 A Accumulator isolation Loop No I B-2 lilV 8808B Accumulator Isolation Loop No 2 B-2 lilV-8808C Accumulator isolation Loop No 3 B-2 lilV-8808D Accumulator Isolation Loop No 4 B-2 tilV-8809A RHR to RCS Cold Leg isolation B-2 lilV-8809B RilR to RCS Cold Leg isolation B-2 tilV-8811 A Containment Sump To RilR Pump Isolation TB-3 lilV-8811B Containment Sump To RilR Pump Isolation TB-3 t ilV-8812A RWST to RiiR Pump Isolation B-2 Q d f j f /.,;.V" L ' $ j; lilV-88128 RWST to RilR Pump Isolation B-2 6 /;.;. ;;;f 4 m;.i ;ic y,.
1IIV-8821 A Si Pump to RCS Cold Leg isolation B-2 E M k 4 Kl.i hy ;;.c ? ; f,.
lHV-8821B S1 Pump to RCS Cold Leg isolation B-2 ipfii.- n ! -lN: 7 :,.
tilV 8835 St Pump to RCS Cold Leg Isolation B-2 hh.Mi Jf..< f '.L.1,... ;
lilV 8840 RHR to RCS Ilot Leg isolation M TB-3 t ilV-8923 A St Pump Suction isolation B-2
..C.f W.d;V C D ;.,
IllV-8923B S1 Pump Suction isolation B-2 Hi.e v;m; QN ;f a 1.D 113 :
lilV-8924 RilR to S1 Pump Suction isolation B-2 gf,n g; u ;; M M L i, j g ;.
t ilV-8994 A Spray Additive Tank Outlet isolation HPL-1 TPL-l TB-1 tilV-8994 B Spray Additive Tank Outlet Isolation llPL-l l TPL-1 l TB-l t ilV-9001 A Containment Spray Pump Discharge isolation l
l TB-3 lilV 9001B Containment Spray Pump Discharge isolation l
l TB-3 lilV-9002A Containment Spray Sump Suction isolation llPL-1 l
l TB-3 tilV-9002B Containment Spray Sump Suction Isolation HPL-l l
l TB-3 j
t ilV-9003 A Containment Spray Sump Suction isolation llPL-l l TPL-1 l TB-3 lilV-9003 B Containment Spray Sump Suction Isolation llPL-1 l TPL-l l TB-3 t ilV-9017A RWST to Containment Spray Suction isolation B-2 Mg;nMBECW--_-__ _
2-5 j
~
f Tag No.
Valve Description Screened Out By Criterion:
Basic l Pressure Locking l Therm. Bind.
l liydraulic l Thermal l
lilV-9017B RWST to Containment Spray Suction isolation B-2 I HV-9380A Containment Atmosphere Service Air B-1
,B-2 I LV-0112B Volume Control Tank Outlet isolation B-2 ILV-0112D RWST to Charging Pump Suction Isolation HPL-1 TPL-l TB-3 I LV-0112E RWST to Charging Pump Suction isolation l IiPL-1 l TPL-1 l TB-3 2FV-0610 RilR Pump i Miniflow l
l l TB-3 2FV-0611 RilR Pump 2 Minillow FB-3 2ilV-0780 Normal Containment Sump Pump Discharge B-2 B
211V-10958 Sludge Mixing Isolation to RWST B-2 211V-12975 Containment Air Radiation Monitor Inlet B-1, B-211V-12976 Containment Air Radiation Monitor inlet B-1, B 211V-15196 Feedwater Bypass isolation to SG B-2 2ilV-15197 Feedwater Bypass isolation to SG B-2 2ilV-19051 Thermal Barrier Supply Isolation B-2 2ilV-19053 Thermal Barrier Supply Isolation B-2 2HV-19055 Thermal Barrier Supply isolation
- B-2 2ilV-19057 Therrnal Barrier Supply isolation B-2 211V-2041 Thermal Barrier Return Isolation B-2 2ilV-27901 Fire Protection lieader Cont. Isolation Pen 40 B-2 211V-3006A Main Steam isolation Valve B-2 2ilV-3006B Main Steam isolation Valve B-2 2iiV-3009 Steam to AFW Pump Turbine B-2 211V-3016A Main Steam isolation Valve B-2 211V-3016B Main Steam Isolation Valve B-2 211V-3019 Steam to AFW Pump Turbine B-2 2ilV-3026A Main Steam isolation Valve B-2 2ilV-3026B Main Steam isolation Valve B-2 2ilV-3036A Main Steam isolation Valve B-2 2ilV-5106 Steam to AFW Pump Turbine TPL-1 2ilV.5229 SG Feedwater Isolation B-2 2iiV-8000A Pressurizer PORV isolation llPL-1 TPL-1 2}lV-8000B Pressurizer PORV isolation llPL-1 TPL-1 211V-8105 Charging Pump to RCS isolation B-2 j.[i & dr i.i j;, 'i. /,
211V-8106 Charging Pump to RCS isolation B-2 1 ?.4 )$ Wi,1 jd:/ !'W-2ilV-8146 Charging Pump to RCS isolation B-2 O Q ;;c.i i; jf;Q,jE.a 2-6
v
-Tag No.
Valve Description Screened Out By Criterion:
Basic Pressure Locking l Therm. Bind.
1 liydraulic l Thermal l
2ilV-8147 Charging Pump to RCS isolation B-2 2ilV-8438 Charging Pump B Discharge Isolation B-2 2ilV-8471 A Charging Pump A Suction isolation B-2 211V-8471B Charging Pump B Suction isolation B-2 211V 8485A Charging Pump A Discharge Isolation B-2 211V-8701 A RilR Loop i Suction isolation 2ilV-8701B RilR Loop i Suction isolation l
l 211V-8702A RilR Loop 4 Suction Isolation l
l 2ilV-8702B RilR Loop 4 Suction Isolation l
l 2tiV-8716A RilR to RCS Ilot Leg isolation l
l TB-3 2flV-8716B RilR to RCS Ilot Leg isolation l
l TB-3 211V-8801 A Boron injection Tank Discharge Isolation l
l TB-3 211V-8801B Boron injection Tank Discharge Isolation l
l TB-3 2HV-8802A S1 Pump to RCS Ilot Leg isolation l
l TB-3 211V-8802B St Pump to RCS Ilot Leg Isolation l
l TB-3 211V-8804 A RilR litx Train A to Charging Pumps llPL-1 l TPL-1 l TB-3 ilPL-l TPL-1 TB-3 211V-8807A RilR to S1 Pump Suction isolation llPL-l TPL-1 TB-3 2HV-8807B RiiR to Si Pump Suction isolation llPL-l PL-1
'B-3 211V-8808A Accumulator isolation Loop No 1 B-2 211V-8808B Accumulator isolation Loop No 2 B-2 211V-8808C Accumulator Isolation Loop No 3 B-2 211V-8808D Accumulator Isolation Loop No 4 B-2 211V-8811 A Containment Sump To RilR Pump Isolation TB-3 211V-88 I I B Containment Sump To RilR Pump Isolation B-3 211V-8812A RWST to RilR Pump Isolation B-2 211V-8812B RWST to RiiR Pump Isolation B-2 2ilV-8840 RilR to RCS Elot Leg Isolation T3-3 2ilV-8923 A S1 Pump Suction isolation B-2 211V-8923B S1 Pump Suction isolation B-2 211V-8994A Spray Additive Tank Outlet Isolation llPL-1 TPL-1 TB-1 2ilV-8994B Spray Additive Tank Outlet isolation HPL-1 l TPL-1 l TB-1 2ilV-9001 A Containment Spray Pump Discharge Isolation l
l TB-3 211V-9001 B Containment Spray Pump Discharge Isolation l
l TB-3 211V-9002A Containment Spray Sump Suction isolation 11PL-1 l
l TB-3 211V-9002B Containment Spray Sump Suction isolation llPL-1 l
l TB-3 211V-9003 A Containment Spray Sump Suction isolation llPL-l l TPL-l l TB-3 2llV-9003B Containment Spray Sump Suction isolation HPL-l l TPL-1 l TB-3 2-7
I e
Tag No.
Valve Description Screened Out By Criterion:
Basic l Pressure Locking l Therm. Bind.
l Ilydraulic l Thermal l
2ilV-9017A RWST to Containment Spray Suction Isolation B-2 2ilV 9017B RWST to Containment Spray Suction isolation B-2 2}iV 9380A Containment Atmosphere Service Air B-l 211V 9380B Containment Atmosphere Service Air B-1 2ilV-9385 Service Air CIV Pen 80 B-1. B-2 2LV-0112B Volume Control Tank Outlet isolation B-2 2LV-0112C Volume Control Tank Outlet isolation B-2 2LV-0112D RWST to Charging Pump Suction isolation llPL-1 TPL-l TB-3 2LV-0112E RWST to Charging Pump Suction Isolation llPL-1
'PL-1
'B-3 AllV-19722 Electric Steam Boiler Isolation B-2 AllV 19723 Electric Steam Boiler Isolation B-2 2-8
a.
e f
3.0 POTENTIALLY SUSCEPTIBLE VALVE EVALUATIONS r
A total of 44 valves were identified as being potentially susceptible to pressure locking and/or thermal binding in conjunction with the screening process discussed in Section 2 of this document. These valves represent 12 different applications as identified in Table 3-1.
Table 3-1 Potentially Susceptible Valves Tag No.
Descrintion Suscentibility 1/2HV-0610 & 1/2HV-0611 RHR Pump Miniflow HPL,TPL,TB 1/2HV-5106 TDAFW Steam Admission HPL,TB 1/2HV-8000A/B PORV Block Valve TB 1/2HV-870) A/B RHR Loop Suction HPL,TPL,TB 1/2HV-8702A/B RHR Loop Suction HPL, TPL, TB 1/2HV-8716A/B RHR to RCS Hot-Leg Isol.
HPL,TPL 1/2HV-8801 A/B -
BIT Discharge HPL, TPL 1/2HV-8802A/B Si to RCS Hot-Leg Isol.
HPL,TPL
)
1/2HV-8811 A/B RHR Cont. Sump Suction HPL,TPL 1/2HV-8840 RHR to RCS Hot-Leg Isol.
HPL, TPL 1/2HV-9001 A/B Cont. Spray Discharge HPL, TPL 1/2HV-9002A/B Cont. Spray Sump Suction TPL Detailed evaluations were performed for each of the valves identified in Table 3-
- 1. For valves which were determined to be susceptible to pressure locking and/or thermal binding, operability determinations were performed to ensure that the valves would be capable of performing their design-basis functions in their current configurations. Finally, corrective actions were identified for susceptible valves to provide additional assurance that the valves would be capable of performing their design functions in the future.
Thermally induced pressure locking is caused by ar. increase in valve body temperature which causes a subsequent increase in the temperature of any fluid trapped in the bonnet area of the valve. Assuming die bonnet area is water solid and that the valve seats and packing are leak tight, the temperature increase can result in an increase in the pressure of the fluid trapped inside the valve. Testing performed by Commonwealth Edison has indicated, however, that for this phenomenon to occur the rate of heat addition must be sufficient to cause pressure to increase faster that the decay rate due to seat and/or packing leakage. Normal ambient temperature swings are not sufficient to cause this phenomenon nor are 3-1
q 1
e
{
I the relatively moderate ambient temperature increases experienced by many valves under accident conditions. For a valve to be considered potentially 3
susceptible to thermally induced pressure locking, the valve must experience a substantial heatup over a relatively short period of time. Examples of credible scenarios for thermally induced pressure locking would be steam impingement on the valve body or a sudden increase in process fluid temperature at the valve.
Hydraulic pressure locking can occur when the upstream or downstream side of a i
valve disk experiences a rapid depressurization prior to being required to open.
The system pressure acting on the valve disk can deflect the disk away from the valve seat, thereby allowing process fluid to enter the bonnet area of the valve.
' When the system pressure is suddenly removed the disk can reseat, trapping high pressure fluid in the bonnet area. It should be noted that a rapid decay of system
)
pressure is required to cause this phenomena. In cases where system pressure decreases slowly, the valve disk will not suddenly reseat and in those cases, l
bonnet pressure will tend to track system pressure. At some point, the system pressure will have decreased sufficiently to allow the disk to reseat, but this pressure will be lower than the maximum system pressure which must be i
considered in the case of a rapid depressurization. In addition, the bonnet will not remain pressurized indefinitely following a hydraulic pressure lock scenario.
Valves are not completely leak tight, and a relatively small amount ofleakage will relieve the bonnet pressure. Testing performed by Commonwealth Edison suggests that a pressure decay rate of 10 psi / min is conservative with respect to evaluating valves for potential pressure locking.
Thermal binding occurs when a valve is closed hot and is subsequently cooled -
prior to re-opening. Fle.xible wedge gate valves which are operated in systems in which the process fluid temperature may exceed 200* F, and which may be i
required to open after undergoing a cooldown of at least 100* F, were considered l
potentially susceptible based on the screening criteria. It should be noted that all L
of the valves evaluated in conjunction with this review were flexible wedge gate valves which are generally considered to be less susceptible to thermal binding than solid wedge gate valves. Valves are most susceptible to thermal binding while in the process of cooling' when thermal gradients exist across the various valve components. The additional loads associated with thermal binding are l
lower after the cooldown is complete and the valve components have reached an
- equilibrium temperature.
l t
3-2
p,.
1 3.1 RHR Pump Mini-Flow Valves Descrintion Valves 1/2HV-0610 and 1/2HV-0611 are 3 inch,2035 lb, Westinghouse flexible wedge gate valves. The valves are normally open to provide RHR pump miniflow. The valves have a safety function to close when RHR pump flow increases above a setpoint and to re-open when RHR pump flow decreases below a setpoint. The valves were screened in accordance with the criteria outlined in Section 2 of this document and were determined to be potentially susceptible to
)
hydraulic and thermally induced pressure locking as well as thermal binding.
Thermally Induced Pressure Locking In conjunction with a LOCA, the ambient temperatures in the rooms in which these valves are located are bounded by the normal operating temperatures. The normal ambient temperatures are not sufficient to present concerns relative to thermally induced pressure locking.
These valves are normally open, and close when RHR pump flow exceeds the pumps minimum flow requirements. In conjunction with a LOCA scenario, the pump suctions would initially be aligned to the RWST and the temperature of the water could be as low as 44' F. When the RWST is exhausted the pump suctions would be re-aligned to the containment sumps and when recirculation begins the initial fluid temperature at the heat exchanger outlets would be approximately 180* F. These valves are located in close proximity to the main RHR heat exchanger discharge piping and would be expected to heatup in conjunction with the transfer to recirculation. Therefore, thermally induced pressure locking must be considered if the valves are required to re-open in conjunction with the transfer to hot leg recirculation.
The scenario associated with transferring to hot-leg recirculation was evaluated with respect to the potential for thermally induced pressure locking. It was determined that when the transfer to hot-leg recirculation is made, RHR flow may be reduced to the point that these valves will receive a signal to open. However, although the opening setpoint may be reached, the flow during this evolution will not be reduced below the RHR pump's minimum flow requirements. Therefore, although the valve may be susceptible to thermally induced pressure locking at this point, the valves are not required to open to protect the RHR pumps.
However, assuming the valves received a signal to open, and failed to open due to thermally induced pressure locking, the valves would not be available subsequent to the event.
3-3
i
~,
?
i
}
Based on the results of this evaluation, it was concluded that these valves are not j
susceptible to thermal pressure locking with respect to performing their design-basis function which is to provide RHR pump minimum flow protection.
However, the potential exists for the valves to receive an open signal in i
L conjunction with the transfer to hot-leg recirculation, and at this point the valves may be susceptible to thermally induced pressure locking. In addition, certain 4
operating evolutions associated with the shutdown cooling mode of RHR system j
operation may expose the valves to conditions conducive to thermally induced pressure locking.
Hydraulic Pressure Lockino In conjunction with a LOCA, these valves are initially exposed to RHR pump discharge pressure which in this case would be equivalent to the RHR pump 4
J developed head plus the elevation head in the RWST. This pressure would gradually trend down as the RWST is depleted and the pump suctions are re-aligned to the containment sumps to initiate cold-leg recirculation. This pressure transient would be relatively slow and would not be expected to cause hydraulic 4
i i
In conjunction with the shutdown cooling mode of RHR system operation, normal evolutions such as switching trains of RHR or an RHR pump trip may expose these valves to conditions conducive to hydraulic pressure lockmg.
)
Based on the results of this evaluation, it was concluded that these valves are not susceptible to thermal pressure locking with respect to performing their design-basis function, which is to provide RHR pump minimum flow protection.
However, certain operating evolutions associated with the shutdown cooling mode of RHR system operation may expose the valves to conditions conducive to j
hydraulic pressure locking.
t Thermal Binding In conjunction with the shutdown cooling mode of RHR system operation, these valves may be exposed to temperatures as high as 350' F when RHR system operation is initiated. The RHR system temperatures will decrease substantially 1
in conjunction with the cooldown of the RCS and the miniflow valves will typically remain closed during this process. If the valves are required to open at this point, they may be at a substantially lower temperature than when closed.
Based on the results of this evaluation, it was concluded that these valves may be susceptible to thermal binding in conjunction with the shutdown cooling mode of RHR system operation.
3-4
l v
\\
{'
Corrective Actions These valves will not adversely impact the operation of the RHR system during accident scenarios. The valves may be susceptible to pressure locking and/or thermal binding while the system is operated in the shutdown cooling mode.
However, the RHR systems have been operated extensively in this mode and these valves have operated satisfactorily.
To provide additional assurance that these valves will be capable of providmg reliable minimum flow protection for the RHR pumps, the control schemes for these valves will be revised. The valves will be controlled in the closing direction by the limit switch, with the limit switch set to prevent hard wedging. These valves are not required to be leak tight and setting the valves up in this marmer will preclude both pressure locking and thermal binding.
3.2 Turbine Driven Auxiliary Feedwater(AFW) Pump Steam Admission Valves Descriotion Valves 1/2HV-5106 are 4 inch,900 lb Anchor-Darling flexible wedge gate valves. The valves are normally closed and have a safety function to open to admit steam to the AFW pump turbine. The valves were screened in accordance with the criteria outlined in Section 2 of this document and were determined to be potentially susceptible to hydraulic pressure locking and thermal binding.
Hydraulic Pressure Locking The upstream side of these valves are exposed to normal secondary system pressure, and the valves may be required to operate after a reduction in secondary system pressure. Should high pressure steam become trapped in the bonnet of these valves the reduction in secondary system pressure and temperature would cool the valves and cause the steam trapped in the bonnets to condense, thereby relieving the pressure. In addition, the valve stems are installed in a vertical orientation and the valves are not located at a low point in the system. Any condensation would flow back into the valve rather than collecting in the bonnet area.
Based on the results of this evaluation, it was concluded that these valves are not susceptible to hydraulic pressure locking.
3-5
v
?
\\
Thermal Binding The turbine-driven AFW system is tested on a quarterly basis and this valve is closed at a secondary system temperature of 545* F. The valves may subsequently be required to open at temperatures as low as 350* F to assist in a plant cooldown. The valw is of the flexible wedge design and utilizes a carbon steel material in both the valve body and disk. The valve design, and the fact that both the disk and body are manufactured from similar materials, minimize the risk of thermal binding. In addition, the valve body and connecting piping are insulated which minimizes the temperature differential between the valve body and disk. Finally, the valve vendor, Anchor-Darling, indicated that thermal binding would not be a problem for this valve unless steam temperatures decreased by 200* to 300* F.
Based on the results of this evaluation, it was concluded that these valves are not susceptible to thermal binding.
3.3 Pressurizer Power-Operated Relief Valve (PORV) Block Valves Descrintion Valves 1/2HV-8000 are 3 inch,2035 lb Westinghouse flexible wedge gate valves.
The valves are normally open and have a safety function to close to isolate a leaking or stuck open PORV. In the event that the valves are closed, the valves are required to open to mitigate a steam generator tube rupture. The valves were screened in accordance with the criteria outlined in Section 2 of this document and were determined to be potentially susceptible to thermal binding.
Thermal Binding During power operation these valves are exposed to steam at a temperature of approximately 653* F. If a valve is closed to isolate a leaking PORV, the valve will continue to be exposed to this temperature as long as the unit remains in power operation. In the event of a SGTR event, the Emergency Operating Procedures (EOPs) require that the position of the block valves be verified. If the block valves are not closed to isolate an excessively leaking or stuck open PORV, i
the EOP directs the operator to open at least one PORV block valve. This step l
ensures that a flowpath will be available later in the event should a PORV be required for RCS pressure reduction.
3-6
.y M
4 Based on the results of this evaluation, it was concluded that these valves would not be susceptible to thermal bincing in conjunction with responding to a SGTR.
3 In addition, these valves are of t'ie tiexible wedge design with a stainless steel valve body and disk. The valver, are also equipped with Limitorque SB operators with compensator spring packs. The valve design and the utilization of an operator with spring compensation minimize the possibility of thermal binding.
3.4 RHR Loop Suction isolation Valves (Pump Side)
Description Valves 1/2HV-8701 A and 1/2HV-8702A are 12 inch,1525 lb Westinghouse flexible wedge gate valves. The valves are normally closed and have a safety function to open when aligning the RHR system for safety grade cold shutdown.
The valves were screened in accordance with the criteria outlined in Section 2 of this document and were determined to be potentially susceptible to hydraulic and.
thermally induced pressure locking as well as thermal binding.
Thermally Indiwad Pressure Locking These valves are not required to operate in response to a LOCA and are exposed to a maximum ambient temperature of 120' F during normal operation. This ambient tamperature '.s not sufficient to present' concerns relative to thermally induced pressure locking.
These valves are closed in conjunction with a unit start-up when the RCS temperature is less than 350' F. The valves are separated from the RCS by approximately sixty feet ofinsulated piping and the 1/2HV-8701B or 1/2HV-8702B valve. As the RCS temperature is increased to normal operating conditions these valves may experience some temperature increase, however, the heatup will not be as significant as that which would occur on the 1/2HV-8701B and 1/2HV-8702B valves. The increase in RCS temperature, and any subsequent heatup of these valves, would occur over a period of hours and would not be at a j
sufficient rate to cause thermally induced pressure locking.
Based on the results of this evaluation, it was concluded that these valves are not susceptible to thermally induced pressure locking.
Hydraulic Pressure Locking Assuming the check valve bypass around the 1/2HV-8701B or 1/2HV-8702B valve leaks, these valves would be exposed to RCS pressure during normal unit 3-7
~.
1
.{
3 L
1 operation. The valves are not opened in conjunction with a unit shutdown until RCS pressure has decreased to a maximum of 425 psig. The decrease in RCS pressure associated with a nomial unit shutdown is gradual and takes place over a period of hours rather than the sudden decrease associated with a LOCA. In conjunction with the shutdown cooling mode of operation, the upstream disk of these valves would not be exposed to a rapid pressure decrease which would cause l
the disk to suddenly rescat, trapping pressure in the bonnet. Rather, the reduction l
in pressure would occur slowly and the bonnet pressure would be expected to track the actual RCS pressure as the cooldown progressed. In addition, if the l
upstream side of the disk did rescat at some point as RCS pressure was being j
reduced, the bonnet pressure would have sufricient time to decay prior to opening these valves. This scenario is a normal sequence of events for a unit shutdown and these valves have been operated successfully under these conditions on numerous occasions.
l Based on the results of this evaluation, it was concluded that t.*ese valves are not j
susceptible to hydraulic pressure locking.
l Thermal Binding i
L These valves are normally closed at approximately 350' F in conjunction with a l
unit start-up and are normally opened at approximately 350' F in conjunctio.1 with l
a shutdown. Therefore, the initial operation of the RHR system does not prerent l
any concerns relative to thermal binding. Switching trains of RHR, following l
initial RHR system operation, could require the valves in the train being placed in service to open at temperatures substantially lower than 350' F. However, RHR j
trains are switched routinely during refueling outages and no problems have been l
experienced with respect to thermal binding.
l Based on the results of this evaluation, it was concluded that these valves are not susceptible to thermal binding. In addition, the existing Limitorque SMB operators currently installed on these valves will be modified to the SB
(
configuration in conjunction with Generic Letter 89-10 modifications being l
implemented during the 1996 refueling outages. These modifications will provide additional assurance that these valves will not be susceptible to thermal binding.
l l
3.5 RHR Loop Suction Isolation Valves (RCS Side)
Description l
l Valves 1/2HV-8701B and 1/2HV-8702B are 12 inch,1525 lb Westinghouse flexible wedge gate valves. The valves are normally closed and have a safety 3-8
.o function to open when aligning the RHR system for safety grade cold shutdown.
The valves were screened in accordance with the criteria outlined in Section 2 of this document and were determined to be potentially susceptible to hydraulic and thermally induced pressure locking as well as thermal binding.
Thermally Induced Pressure Locking These valves are not required to operate in response to a LOCA and are exposed to a maximum ambient temperature of 120' F during normal operation. This ambient temperature is not sufficient to present concerns relative to thermally induced pressure locking.
These valves are closed in conjunction with a unit start-up when the RCS temperature is less than 350' F. The valves are connected to the RCS by approximately twenty feet ofinsulated piping and as the RCS temperature is increased to normal operating conditions, the temperature on the upstream side of these valves is expected to track RCS temperature. The increase in RCS temperature, and the subsequent heatup of these valves, occurs over a period of hours. While the rate of heatup may be sufficient to cause an increase in bonnet pressure, the overall length of time associated with this evolution will allow pressure to decay before it can become significant. In addition, the RCS must cooldown to less than 365* F prior to opening these valves which provides additional time for the bonnet pressure to decay.
1 Based on the results of this evaluation, it was concluded that these valves are not susceptible to thermally induced pressure locking.
Hydraulic Pressure Locking These valves are exposed to RCS pressure during normal unit operation and are not opened in conjunction with a unit shutdown until RCS pressure has decreased to a maximum of 425 psig. The decrease in RCS pressure associated with a normal unit shutdown is gradual and takes place over a period of hours rather than the sudden decrease associated with a LOCA. In conjunction with the shutdown cooling mode of operation, the upstream disk of these valves would not be exposed to a rapid pressure decrease which would cause the disk to suddenly reseat, trapping pressure in the bonnet. Rather, the reduction in pressure would occur slowly and the bonnet pressure would be expected to track the actual RCS pressure as the cooldown progresses. In addition, if the upstream side of the disk did rescat at some point as RCS pressure was being reduced, the bonnet pressure would have sufficient time to decay prior to opening these valves. This scenario is a normal sequence of events for a unit shutdown and these valves have been operated under these conditions on numerous occasions without difficulty.
3-9
z r
I i
Based on the results of this evaluation, it was concluded that these valves are not susceptible to hydraulic pressure locking.
l Thermal Bindino l
These valves are normally closed at approximately 350' F in conjunction with a unit start-up and are normally opened at approximately 350* F in conjunction with a shutdown. Therefore, the initial operation of the RHR system does not present any concerns relative to thermal binding. Switching trains of RHR, following initial RHR system operation, could require the valves in the train being placed in f
[
service to open at temperatures substantially lower than 350' F. However, RHR l
trains are switched routinely during refueling outages and no problems have been experienced with respect to thermal binding.
Based on the results of this evaluation, it was concluded that these valves are not susceptible to thermal binding. In addition, the existing Limitorque SMB operators currently installed on these valves will be modified to the SB configuration in conjunction with Generic Letter 89-10 modifications being l
implemented during the 1996 refueling outages. These modifications will provide additional assurance that these valves will not be susceptible to thermal binding.
3.6 RHR to RCS Hot-Leg Isolation Valves i
Description Valves 1/2HV-8716A/B are 8 inch,316 lb Westinghouse flexible wedge gate valves. The valves are normally open to crosstie the two trains of the RHR l
system. The valves have a safety function to close when transferring to cold-leg recirculation and to open when transferring to hot-leg recirculation. The valves were screened in accordance with the criteria outlined in Section 2 of this document and were determined to be potentially susceptible to hydraulic and thermally induced pressure locking.
Discussion These valves were previously modified by drilling a hole in the upstream side of the disk. Since this modification precludes the possibility of pressure locking, no j
further evaluations were required.
3-10
\\
q l
3.7 Boron Injection Tank Discharge Isolation Valves Descriotion Valves 1/211V-8801 A/B are 4 inch,1525 lb Westinghouse flexible wedge gate valves. The valves are normally closed and have a safety function to open on an SI signal to provide a flow path from the CCPs to the RCS cold-legs. The valves also have a safety function to open to provide an emergency boration flowpath if the normal charging path is not available. The valves were screened in l
accordance with the criteria outlined in Section 2 of this document and were determined to be potentially susceptible to hydraulic and thermally induced pressure locking.
Thermally Induced Pressure Locking In conjunction with a LOCA, the ambient temperature in the rooms in which these valves are located may rise to a maximum temperature of 145' F due to the j
recirculation of containment sump fluids in adjacent piping.110 wever, the temperature rise due to the recirculation of hot fluids from the sumps will not begin until after these valves have been opened.
Based on the results of this evaluation, it was concluded that these valves are not i
susceptible to thermally induced pressure locking.
IIvdraulic Pressure Locking These valves are separated from the RCS by two check valves and assuming the check valves leak, the downstream side of the disc could be exposed to RCS pressure. In the event of a LOCA, RCS pressure would decrease allowing the downstream side of the disc to rescat trapping high pressure fluid in the bonnet.
Ilowever, concurrent with RCS pressure acting on the downstream side of the disk, CCP discharge pressure acts on the upstream side of the disk. Since CCP pressure is higher than RCS pressure, the CCP pressure becomes the relevant force with respect to pressure locking. If the CCPs remain in operation and are pressurizing the upstream side of the disk in conjunction with the SI signal, pressure locking is not a concern for these valves. Ilowever, if a loss of offsite power (LOSP) occurs prior to the Si signal, pressure locking must be considered since the CCPs will trip, thereby depressurizing the piping upstream of these valves.
In the event of a LOSP, the CCPs and the 1/2ilV-8801 A/B valves receive simultaneous signals to start and open, respectively. The CCPs come up to speed in approximately 3 seconds, thereby pressurizing the upstream side of the disk on 3-11
x the 1/2HV-8801 A/B valves and releasing any pressure trapped in the bonnet. In the event that sufficient pressure was trapped in the bonnet to prevent the operator from opening the valve, the motor would experience a locked rotor condition for -
approximately 3 seconds, at which time the bonnet pressure would be released.
The operator motors are capable of surviving a locked rotor condition for 3 seconds without incurring damage.
Based on the results of this evaluation, it was concluded that these valves are not susceptible to hydraulic pressure locking.
3.8 St Pump to RCS Hot-Leg Isolation Valves Descriotion Valves 1/2IIV-8802A/B are 4 inch,1525 lb Westinghouse flexible wedge gate valves. The valves are normally closed and have a safety function to open when transferring to hot leg recirculation to provide a flowpath between the SI pump discharge and the hot-legs. The valves were screened in accordance with the criteria outlined in Section 2 of this document and were determined to be potentially susceptible to hydraulic and thermally induced pressure locking.
Thermally Induced Pressure Locking In conjunction with a LOCA, the ambient temperature in the rooms in which these valves are located may rise to a maximum temperature of 135' F due to the recirculation of containment sump fluids in adjacent piping. This ambient temperature is marginally higher than the maximum temperatures experienced during normal operation but would not be sufficient to provide a heat-up rate capable of causing thermally induced pressure locking.
The piping upstream of these valves is connected to the cold-leg recirculation piping which will be circulating hot containment sump fluids prior to transferring to hot-leg recirculation. Ilowever, approximately 200 feet of piping separate these valves from the cold-leg injection flowpath, and a substantial heat up of the valve body due to recirculation fluids would not occur in the eleven hours prior to transferring to hot-leg recirculation.
Based on the results of this evaluation, it was concluded that these valves are not susceptible to thermally induced pressure locking.
)
3-12
)
,. ~..
s l ~~;...
1 l
l Hydraulic Pressure Lockine These valves are separated from the RCS by two check valves and assuming the check valves leak, the downstream side of the disc could be exposed to RCS '
pressure, in the event of a LOCA, RCS pressure would decrease allowing the downstream side of the disc to rescat, potentially trapping high pressure fluid in the bonnet. However, since the transfer to hot-leg recirculation does not occur for approximately eleven hours following the initiation of the event, there would be sufficient time for the bonnet pressure to decay prior to opening the valve.
During cold-leg recirculation the upstream side of the disc is exposed to SI pump discharge pressure. When the transfer to hot-leg recirculation is made, the SI l
pumps are tripped prior to opening these valves. When the SI pumps are tripped l
the pressure in the SI pump discharge piping will decrease, allowing the upstream side of the disc to rescat, potentially trapping high pressure fluid in the bonnet.
Since the valve is required to open shortly after tripping the pump, there may not be sufficient time for the bonnet pressure to decay prior to opening this valve.
r Based on the results of this evaluation, it was concluded that these valves may be susceptible to hydraulic pressure locking in conjunction with the sequence of
~
events associated with transferring to hot-leg recirculation.
Corrective Actions The scenario associated with tripping the Si pumps prior to opening these valves was evaluated utilizing methodology developed by Commonwealth Edison and obtained in conjunction with the Westinghouse Owners Group (WOG) Pressure Lecking and Thermal Binding Task Team. The evaluation indicated that the valves have suflicient margin to perform their design-basis function in conj unction with the aforementioned pressure locking induced loads.
To p ovide additional assurance that these valves will be capable of performing 6.
esign-basis function, the valves will be modified by drilling a 1/8 inch hole in th downstream side of the disk.
3.9 kHR Pump Containment Sump Suction Isolation Valves Description Valves 1/2HV-8811 A/B are 14 inch,316 lb Westinghouse flexible wedge gate valves. The valves are nomially closed and have a safety function to open when transferring to cold leg recirculation to provide a flowpath between the 3-13
i ' ".,
- b
- sa..,
I containment sumps and the suction to the RHR pumps. The valves were s reened in accordance with the cn'eria outlined in Section 2 of this document and were determined to be potentially susceptible to hydraulic and thermally induc ed pressure locking.
Thermally Induced Pressure Locking In conjunction with a LOCA, the ambient temperature in the rooms in which these valves are located may rise to a maximum temperature of 135' F. However, the temperature rise is due to the recirculation of hot fluids from the sumps which will not begin until after these valves have been opened.
The piping upstream of these valves is connected to the containment sumps which would be exposed to hot water in the event of a LOCA. The heat input from the flow of hot water into the containment sumps may be sufficient to cause the valve body to heat-up prior to opening these valves to in.tiate cold-leg recirculation.
Based on the results of this evaluation, it was concluded that these valves may be susceptible to thermally induced pressure locking due to hot water entering the sumps in conjunction with a LOCA.
Hydraulic Pressure Locking These valves are separated from the RHR suction piping by a single check valve and assuming this check valve leaks, the downstream disks of these valves could be exposed to pressures as high as 450 psig when the RHR system is in service with the loop suction valves open. When the RHR system is secured and the loop suction valves are closed, the pressure in the RHR suction piping will decrease 1
allowing the downstream disk to rescat, potentially trapping high pressure fluid in the bonnet. However, this situation only occurs in conjunction with an RCS v
heatup or cooldown and any pressure which becomes trapped in the bonnet will decay prior to power operation.
Based on the results of this evaluation, it was concluded that these valves are not susceptible to hydraulic pressure locking.
Corrective Actions The scenario associated with hot water entering the sumps following a LOCA was evaluated in detail to determine if the valves would be capable of performing their design-basis function. The valves are located at an elevation approximately six feet below their respective sumps and are separated from the sumps by approximately thirty feet of piping which is filled with cool water prior to start-3-14
lh L
up. This arrangement is not conducive to the rapid transfer of heat from the sump to the valve body. Therefore, it was concluded that a significant heatup of the valve body would not occur prior to opening these valves in conjunction with the l
transfer to cold-leg recirculation.
l l
To provide additional assurance that these valves will be capable of performing their design-basis function, the valves will be modified by drilling a 1/8 inch hole in the upstream side of the disk.
3.10 RHR to RCS Hot-Leg Isolation Valve l
Description
' Valves 1/2HV-8840 are 12 inch,1525 lb Westinghouse flexible wedge gate l
valves. The valves are normally closed and have a safety function to open when L
transferring to hot leg recirculation to provide a flowpath between the discharge of the RHR pumps and the hot legs. The valves were screened in accordance with the criteria outlined in Section 2 of this document and were determined to be potentially susceptible to hydraulic and thermally induced pressure locking.
Thermally Induced Pressure Locking In conjunction with a LOCA, the ambient temperature in the rooms in which these valves are located may rise to a maximum temperature of 145' F due to the l
recirculation of containment sump fluids in adjacent pipin4 This ambient temperature is marginally higher than the maximum tempe ratures experienced during normal operation but would not be sufficient to pro' He a heat-up rate i
capable of causing thermally induced pressure locking.
The piping upstream of these valves is connected to the cold-leg recirculation piping which will be circulating hot containment sump fluids prior to transferring to hot-leg recirculation. However, this valve is isolated from the discharge of the RHR pumps by the 1/2HV-8716A/B valves which are closed during cold-leg recirculation. Therefore, a substantial heat up of the valve body due to recirculation fluids would not occur in the eleven hours prior to transferring to hot-leg recirculation.
t l
Based on the results of this evaluation, it was concluded that these valves are not
[
susceptible to thermally induced pressure locking.
J l
3-15
-w
m.
s Hydraulic Pressure Lockino i
These valves are separated from the RCS by two check valves and assuming the check valves leak, the downstream side of the disc could be exposed to RCS pressure. In the event of a LOCA, RCS pressure would decrease allowing the downstream side of the disc to rescat, potentially trapping high pressure fluid in the bonnet. Ilowever, since the transfer to hot-leg recirculation does not occur for approximately eleven hours following the initiation of the event, there would be sufficient time for the bonnet pressure to decay prior to opening the valve.
Based on the results of this evaluation, it was concluded that these valves are not susceptible to hydraulic pressure locking.
3.11 Containment Spray Pump Diaharge Isolation Valves Descrintion Valves 1/211V-9001 A/B are 8 inch,316 lb Westinghouse flexible wedge gate valves. The valves are normally closed and have a safety function to open on a high containment pressure signal to establish a flowpath between the discharge of the containment spray pumps and the spray header. The valves were screened in accordance with the criteria outlined in Section 2 of this document and were determined to be potentially susceptible to hydraulic and thermally induced pressure locking.
Thermally Induced Pressure Locking In conjunction with a LOCA the ambient temperature in the rooms in which these valves are located may rise to a maximum temperature of 145' F. However, the temperature rise due to the recirculation of hot fluids from the sumps will not begin until after these valves have been opened.
Based on the results of this evaluation, it was concluded that these valves are not susceptible to thermally induced pressure locking.
11vdraulic Pressure Locking l
The Containment Spray Pumps are teted on a quarterly bris and the upstream l
side of the disks on the discharge valves are exposed to the p :mp discharge l
pressure of 248 psig. Upon completion of the test, the containuert spray pump is tripped causing pressure in the containment spray pump dischaue piping to j
3-16 l
~
'p 4
decrease allowing the upstream side of the disk to reseat, potentially trapping high pressure fluid in the bonnet.
In the event of an accident the containment spray pump and the discharge valve receive simultaneous signals to start and open respectively. Tbc retainment spray pumps come up to speed in approximately 1.5 seconds, thereby pressurizing the upstream side of the disk on the discharge valve and releasing any pressure trapped in the bonnet. In the event that sufficient pressure was trapped in the i
bonnet to prevent the operator from opening the valve, the motor would experience a locked rotor condition for approximately 1.5 seconds, at which time the bonnet pressure would be released. The operator motors are capable of surviving a locked rotor condition for 1.5 seconds without incurring damage.
l Therefore. it was concluded that these valves would be capable of performing their design-basis function.
3.12 Containment Spray Pump Sump Suction Isolation Valves Descriotion Valves 1/2HV-9002A/B are 10 inch,150 lb Westinghouse flexible wedge gate valves. The valves are normally closed and have a safety function to open when transferring to recirculation to provide a flowpath between the containment sumps and the suction to the containment spray pumps. The valves were screened in accordance with the criteria outlined in Section 2 of this document and were determined to be potentially susceptible to hydraulic and thermally induced pressure locking, Thermally Induced Pressure Locking In conjunction with a LOCA, the ambient temperature in the rooms in which these valves are located may rise to a maximum temperature of 135' F. However, the temperature rise is due to the recirculation of hot fluids from the sumps which will not begin until aller these valves have been opened.
The piping upstream of these valves is connected to the containment sumps which would be exposed to hot water in the event of a LOCA. The heat input from the flow of hot water into the containment sumps may be sufficient to cause the valve body to heat-up prior to opening these valves to initiate cold-leg recirculation.
Based on the results of this evaluation, it was concluded that these valves may be susceptible to thermally induced pressure locking due to hot water entering the sumps in conjunction with a LOCA.
3-17
I Corrective Actions l
The scenario associated with hot water entering the sumps following a LOCA was evaluated in detail to determine if the valves would be capable of performing their design-basis function. The valves are located at an elevation approximately six feet below their respective sumps and are separated from the sumps by approximately twenty feet of piping which is filled with cool water prior to start-up. This arrangement is not conducive to the rapid transfer of heat from the sump to the valve body. Therefore, it was concluded that a significant heatup of the valve body would not occur prior to opening these valves in conjunction with the transfer to cold-leg recirculation.
To provide additional assurance that these valves will be capable of performing their design-basis function, the valves will be modified by drilling a 1/8 inch hole in the upstream side of the disk.
3-18
>.J.
4.0 MODIFICATIONS As a result of the reviews performed in conjunction with Generic Letter 95-07, a total of 16 valves were identified for modifications to provide additional assurance that the valves will be capable of performing their design-basis functions. Table 4-1 identifies the valves to be modified, the respective modifications and the implementation schedule.
Table 4-1 Generic Letter 95-07 Modifications Ing h Modification Schedule IHV-0610 Revise Control Logic 1R7 IHV-0611 Revise Control Logic 1R7 lHV-8802A Drill 1/8" Hole in Disk 1R6 IIIV-8802B Drill 1/8" Hole in Disk 1R6 1IIV-8811 A Drill 1/8" Hole in Disk 1R6 1HV-881IB Drill 1/8" Hole in Disk 1R6 lHV-9002A Drill 1/8" Hole in Disk 1R6 IHV-9002B Drill 1/8" Hole in Disk 1R6 2HV-0610 Revise Control Logic 2R5 2HV-0611 Revise Control Logic 2R5 21IV-8802A Drill 1/8" Hole in Disk 2R5 2HV-8802B Drill 1/8" Hole in Disk 2R5 2HV-8811 A Drill 1/8" Hole in Disk 2R5 2HV-8811B Drill 1/8" Hole in Disk 2R5 2HV-9002A Drill 1/8" Hole in Disk 2R5 2HV-9002B Drill 1/8" Hole in Disk 2R5 l
4-1