ML20097G029
| ML20097G029 | |
| Person / Time | |
|---|---|
| Site: | Wolf Creek  |
| Issue date: | 02/14/1996 |
| From: | Maynard O WOLF CREEK NUCLEAR OPERATING CORP. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| GL-95-07, GL-95-7, WO-96-0023, WO-96-23, NUDOCS 9602200361 | |
| Download: ML20097G029 (17) | |
Text
-
t W$LF CREEK NUCLEAR OPERATING CORPORATION Otto L Maynard Wce President Plant Operations February 14,1996 WO 96-0023 U.
S. Nuclear Regulatory Commission ATTN: Document Control Desk Mail Station P1-137 Washington, D.
C.
20555
Reference:
Letter ET 95-0111 dated October 11, 1995 from R.
C. Hagan to USNRC
Subject:
Docket No. 50-482:
180 Day Response to Generic Letter 95-07, " Pressure Locking and Thermal Binding of Safety-Related Power Operated Gate Valves" Gentlemen:
The attachments to this letter provide Wolf Creek Nuclear Operating Corporation's 180 day response to Generic Letter 95-07.
This information is being provided in accordance with the reporting requirements of the Generic Letter.
If you have any questions concerning this matter, please contact me at (316) 364-8831 extension 4450 or Mr. Richard D.
Flannigan at extension 4500.
Very truly yours, hW/'
sy Otto L. Maynard OLM/jra I
Attachments:
I.
General Information, and Summary II.
Preliminary Evaluation for Pressure Locking and Thermal Binding of Safety-Related Power-Operated Gate Valves III.
Results of the Initial Screening Evaluation of Motor Operated Gate Valves IV.
Summaries of Detailed Evaluations of Potentially Susceptible Valves cc:
L.
J.
Callan (NRC), w/a W. D. Johnson (NRC), w/a J.
F. Ringwald (NRC), w/a J. C. Stone (NRC), w/a i
9602200361 960214
)
PDR ADOCK 05000482 P
ppg
((
P O. Box 411/ Burlington, KS 66839 / Phone: (316) 364-8831 An Equal Opportunity Employer M T/HC/ VET g(j./
I l
i STATE OF KANSAS
)
)
SS J
COUNTY OF COFFEY
)
R 1
' Otto L. Maynard, of lawful age, being first duly sworn upon oath says that he j
is Vice President Plant Operations of Wolf Creek Nuclear Operating j
Corporation; that he has read the foregoing document and knows the content i
thereof; that he has executed that same for and on behalf of said Corporation j
with full power and authority to do so; and that the facts therein stated are j
true and correct to the best of his knowledge, information and belief.
By jfjf}V OttM.~ 'Mayn6rd' ~ ' ' / ~
Vice President Plant Operations SUBSCRIBED and sworn to before me this k day of Fee 1938.
i WM4. 0 MARY E. GIFFORD '
N tary Ptrblic
]
My Appt. Expires l A, 04 ll Kansas 199Q hd'm Nu I
OS.!993 Notary Public. tote o j
l i
Abt$achmhnt I to WO 96-0023 Paga 1 of 4 WOLF CREEK GENERATING STATION GENERAL INFORMATION, AND
SUMMARY
OF THE EVALUATION AND RESOLUTION OF PRESSURE LOCKING AND THERMAL BINDING OF SAFETY-RELATED POWER-OPERATED GATE VALVES PURPOSE The purpose of this document is to provide the ults of the Wolf Creek 2
Nuclear Operating Corporation (WCNOC) evaluation to satisfy the requirements of NRC Generic Letter. 95-07
" Pressure Locking and Thermal Binding of Safety-Related Power-Operated Valves."
The evaluation consists of two parts:
(1) a preliminary screening to identify those valves which are potentially susceptible to the pressure locking and thermal binding phenomena, and (2) detailed evaluations of those valves which are potentially susceptible to determine if corrective action is necessary, and to establish the corrective action to be taken.
SCOPE The subject evaluation includes 83 motor operated and 8 hydraulically operated gate valves.
Attachment III contains a list of the valves included in the evaluation.
Pressure locking and thermal binding only affect gate valves and only when the valves are closed and required to open, pnettuTunn_y genvuMIhfG TO ELTMTNATE NON-APPLIFAMLE VALVEB Preliminary screening evaluations have been performed on safety-related gate valves at the Wolf Creek Generating Station (WCGS) to determine the potential susceptibility to pressure locking and thermal binding, and to determine whether pressure loc'
.g or thermal binding can possibly affect their safety function.
The initial pressure locking and thermal binding study was completed in December 1994 to the requirements of Generic Letter 89-10 Supplement 6 guidelines.
The results of this preliminary evaluation served as the basis for WCNOC's initial Generic Letter 95-07 submittal, dated October 11, 1995, from R.
C.
Hagan to USNRC (letter ET 95-0111).
This submittal identified 13 valves that are potentially susceptible to pressure locking and/or thermal binding, and whose failure to open could have an adverse impact on plant safety.
Attachment II to this document summarizes the criteria used to screen the valves.
Attachment III provides a listing of the valves included in the screening evaluation and indicates the valves that are potentially susceptible to pressure locking or thermal binding and therefore must be evaluated in greater detail.
)
The initial screening evaluation was recently reviewed to ensure that it reflects current guidance in Generic Letter 95-07.
In this supplementary review the list of valves to be evaluated was increased by eight valves to include valves that are power operated, but do not have motor operators.
Four additional motor-operated valves were also included.
None of the twelve additional valves were determined to represent a safety risk due to pressure loc' king or thermal binding.
The valves that have been added meet the criteria outlined in le and ld of Attachment II.
i
Attachmtht I to WO 96-0023 2
Page 2 of 4 2
DETATT.un EVALUATIONS OF POTENTT17.TY SUSFWDTIBLE VAL M Following the preliminary screening, the 13 valves identified as being potentially susceptible to pressure locking or thermal binding were evaluated in greater detail to determine whether they can be operated safely in their current configuration and whether corrective action is required.
The following table summarizes the results of these detailed evaluations and the 1
corrective actions that have been or will be taken.
More complete summaries of the detailed evaluations are provided in Attachment IV.
In some cases, analyses were performed to confirm that the operator has sufficient capability. to overcome the effects of pressure locking.
These analyses were performed using a calculation methodology developed by.
Commonwealth Edison and considered to be the acceptable industry approach.
t conner"fIVE ACTIONS FOR POTENTTATTY SUSCEPTIBLE VALVES All corrective actions will be implemented prior to restart from the current refueling outage.
At that time all susceptible valves, except three, will i
also have the long term resolution completed.
The remaining three valves are awaiting NRC approval of the Westinghouse Owners Group (WOG) initiative to eliminate hot leg recirculation.
When approved, the initiative will provide justification to no longer require these valves to perform the safety related
{
opening function during hot leg recirculation which creates the conditions for 1
)
~
4 4
J E
Attachment I to WO 96-0023 Page 3 of 4 Sn---ev of Potentially Suscentible Valves Valve ID # and Description Susceptibility Evaluation Summary Corrective Action Summary BBPV8702A & B The preliminary screening indicated that these Pressure Locking : These valves are EJKV8701A & B valves should be evaluated for susceptibility to normally open during heat-up evolutions.
both pressure locking and thermal binding.
A caution will be added to the Residual Heat appropriate procedures prior to the Removal System Thermal Binding: The detailed evaluation restart from the current refueling Suction from RCS indicated that there is one condition that could outage to assure these valves remain Hot Leg Isolation cause thermal binding of these valves when cooling open during heat-up to prevent thermally the RCS fluid.
induced pressure locking.
Pressure Locking: The detailed evaluation also Thermal Binding: Corrective action will indicated that there is one condition that could be been taken prior to the restart from cause thermally induced pressure locking during the current refueling outage by revising plant heat-up.
the appropriate procedures to caution operators to not close the valves while hot, during cooldown without cycling before exposure to a 100*F temperature differential.
EJFCV0610 & 0611 The preliminary screening indicated that these One of these valves has been modified valves should be evaluated for susceptibility to and the other will be modified prior to Residual Heat thermal binding restart from the current refueling Removal Pump outage to be limit close controlled and Minimum Flow The detailed evaluation indicated that there is a soft seated to prevent thermal binding.
Recirculation susceptibility to thermal binding.
Valves EJHV8811A & B The preliminary screening indicated that these These valves will be modified during the valves should be evaluated for susceptibility to current refueling outage to add an air Residual Heat thermally induced pressure locking and thermal reservoir to the bonnet to limit the Removal System binding.
pressure to that which can be Suction from accommodated by the motor operator.
Containment The detailed evaluation indicated that thernal Recirculation Sump binding cannot occur in these valves, but that Isolation there is a susceptibility to thermally induced pressure locking under Loss of Coolant Accident (LOCA) conditions.
Attachment I to WO 96-0023 Page 4 of 4 Sn== mrv of Potentially Susceotible Valves (cont.)
Valve ID # and Description Susceptibility Evaluation Sn-ary Corrective Action Sununary EJHV8840 The preliminary screening showed that this valve Corrective actions will be taken prior should be evaluated for susceptibility to pressure to the restart from the current Resid'1al Heat locking.
refueling outage to administratively Removal System to control the downstream piping header The detailed evaluation indicated that this valve pressure to acceptable levels.
Hot Leg Recirculation is susceptible to pressure locking due to RCS Isolation check valve leakage.
Long term corrective action depends on the resolution of the WOG initiative to eliminate the function for hot leg recirculation.
If approved, no further action is required.
If not, alternate long term corrective actions will be evaluated at that time.
EMHV8802A & B The preliminary screening showed that this valve Calculations demonstrate that the valves should be evaluated for susceptibility to pressure are capable of overcoming the effects of Safety Injection locking.
Pump Discharge to The detailed evaluation indicated that these Long term corrective action depends on RCS Hot Leg Isolation valves are susceptible to pressure locking due to the resolution of the WOG initiative to RCS check valve leakage and safety injection pump eliminate the function for hot leg pressure entrapment.
recirculation.
If approved, no further action is required.
If not, alternate long term corrective actions will be evaluated at that time.
ENHV0001 & 0007 The preliminary screening indicated that these These valves will be modified during the valves should be evaluated for susceptibility to current refueling outage to add an air Containment Spray thermally induced pressure locking and thermal reservoir to the bonnet to limit the Pump Suction from binding.
pressure to that which can be Containment accommodated by the motor operator.
Recirculation Sump The detailed evaluation indicated that thermal Isolation binding cannot occur in these valves, but that there is a susceptibility to thermally induced pressure locking under LOCA conditions.
Aftachmeht II to WO 96-0023 Page 1 of 2 PRELIMINARY EVALUATION FOR PRESSURE LOCKING AND THERMAL BINDING OF SAFETY-RELATED POWER-OPERATED GATE VALVES The preliminary screening evaluation was performed using the following criteria.
1.
Initial screenino for A_onlicability The first step in the screening process was to exclude valves from
)
consideration for which pressure locking or thermal binding cannot occur or
)
does not pose a significant risk to safety if it does occur.
These valves include:
- a. All valves that are not gate valves are excluded because pressure locking and thermal binding have been phenomena exhibited only in gate valves.
- b. All valves that are non-safety-related are excluded because malfunction of these valves does not pose a risk to nuclear safety.
- c. All valves that are safety-related solely because they are part of the pressure boundary are excluded because pressure locking and thermal binding do not pose risks to the pressure boundary.
This includes valves that are normally open, with their safety position being open, or normally closed with their safety position being closed.
Mispositioning was not considered to be a common mode failure,
- d. All valves whose only safety function is to close are excluded because pressure locking and thermal binding only affect the opening function.
However, if a normally open valve may be closed as part of plant maintenance, testing or other unusual circumstances, and then is required to open for safety-related reasons, such valves were not excluded from consideration,
- e. All valves that are of the double disk, or parallel slide, design can be excluded with regard to thermal binding, but not pressure locking. This is because double disk valves have cams that bring the disks together when the stem is withdrawn, thus eliminating binding, and parallel seat valves have sufficient clearance to prevent thermal expansion binding.
2.
Screening for Pressure Locking and Thermal Binding Valves that were not excluded in the initial screening were screened for potential susceptibility to pressure locking and thermal binding.
This was a three step process, a.
First, it is confirmed that the valves meet one of the following three conditions:
- there is a required safety function for the valve to open from the l
closed position, or emergency procedures require the valve to be opened from the closed position, or the valve can be closed for maintenance or operational reasons and is required to be reopened during normal or emergency plant operation.
_. - = - - -.
Attaciukaht II to WO 96-0023 Page 2 of 2 b.' valves'are potentially susceptible to pressure locking if condition "a"
is met, and the valve design is such that the bonnet can be at a higher pressure than the two legs under normal or accident conditions due to 1) rapid system depressurization, or 2) temperature increases induced by plant operation.
- c. Valves. are potentially susceptible to thermal binding if condition "a" is met and 1) the valve can be in the full closed position with the temperature more than 60*F above ambient, and 2) the valve has a wedge type disk.
Note:
Initial screening stated that valve temperature differences greater than 60*F above' ambient were susceptible to thermal binding..The subsequent Westinghouse Owners Group analysis shows that a 100*F temperature difference
'is acceptable for-valves with flexible wedges and, that the likelihood of the thermal binding occurs at temperatures above 200*F.
Attachment III-is a listing of all the motor operated gate valves included in the initial evaluation with a listing of the additional valves added during the recent review.
This table indicates the valves that are potentially susceptible to pressure locking or thermal binding and therefore,. required I
detailed evaluation.
The net result of the screenings performed are that 13 valves have been found to be susceptible to pressure locking and thermal binding.
)
i B
1 i
J l
i
-, - - - - + -
--m--+o
Attachme'nt III to WO 96-0023 Page 1 of 3 Results of Screenina Evaluation of Motor Ooerated Gate Valves Pressure Thermal Locking Binding 1
Valve ID Valve Evaluation Evaluation Number Valve Description Type
ISO GATE, FW ALHV00035 CST TO MD AUX FW PUMP "A"
ISO GATE, FW ALHV00036 CST TO TD AUX FW PUMP ISO GATE, FW l
BBHV0013 RCP "A"
THERMAL BARR CCW RETURN ISO GATE, FW BBHV0014 RCP "B"
THERMAL BARR CCW RETURN ISO GATE, FW BBHV0015 RCP "C"
THERMAL BARR CCW RETURN ISO GATE, FW BBHV0016 RCP "D"
THERMAL BARR CCW RETURN ISO GATE, FW BEHV8000A PZR PORV BBPCV0455A INLET ISO GATE, FW BBHV8000B PZR PORV BBPCV0456A INLET ISO GATE, FO BBHV8037A
'PRT TO CTMT NORMAL SUMP ISO GATE, ~5U~
BBHV8037B PRT TO CTMT NORMAL SUMP ISO GATE, FW BBPV8702A RCS HL 1 TO RHR PUMP "A" SUCTION ISO GATE, FW Yes Yes BBPV8702B RCS HL 4 TO RHR PUMP "B" SUCTION ISO GATE, FW Yes Yes BGHV8105 CHARGING PUMPS TO REGEN HX/ CONT ISO GATE, FW BGHV8106 CHARGING PUMPS TO REGEN HX/ CONT ISO GATE, FW BGLCV0112B VCT LOW LEVEL ISO ON BGO20HCB-4 GATE, FW BGLCV0112C VCT LOW LEVEL ISO ON BGO20HCB-4 GATE, FW BNHV0003 RWST SUPPLY TO CTMT SPRAY PUMP "B"
GATE, FW BNHV0004 RWST SUPPLY TO CTMT SPRAY PUMP "A"
GATE, FW BNHV8806A RWST TO SI PUMP "A" SUCTION ISO GATE, FW BNHV8806B RWST TO SAFETY INJ PUMP SUCTION GATE, FW BNHV8812A RWST TO RHR PMP "A" SUCTION ISO GATE, FW BNHV8812B RWST TO RHR PMP "B"
SUCTION ISO GATE, FW BNLCV0112D RWST TO CCP "A" SUCTION ISO GATE, FW BNLCV0112E RWST TO CCP "B"
SUCTION ISO GATE, FW EFHV0091 ESW SCREEN "A"
SPRAY GATE, FW EFHV0092 ESW SCREEN "B"
SPRAY GATE, FW EFHV0097 ESW PUMP "A"
DISCHARGE AIR RELEASE GATE, FW EFHV0098 ESW PUMP "B"
DISCHARGE AIR RELEASE GATE, FW "EFPDV0019 ESW SELF-CLEANING STRAINER "A"
TRASH GATE, FW EFPDV0020 ESW SELF-CLEANING STRAINER "B"
TRASH GATE, FW EGHV0058 CCW TO RCS ISO GATE, DD EGHV0059 CCW RETURN FROM RCS ISO GATE, DD EGHV0060 CCW RETURN FROM RCS ISO GATE, DD EGHV0061 CCW RETURN FROM RCP THERM BARRIERS GATE, PS ISO EGHV0062
'CCW RETURN FROM RCP THERM BARRIERS GATE, PS ISO EGHV0071 CCW TO RCS ISO GATE, FW 0 DD = Double Disk, FW = Flexible Wedge, and PS = Parallel Slide
f Attacilment III to WO 96-0023 Page 2 of 3 Results of Screenina Evaluation of Motor Onerated Gatp Valves (cont.)
Pressure Thermal Locking Binding Valve ID Valve Evaluation Evaluation Number Valve Description Type
- Required Required EGHV0126 CCW SUPPLY TO CONTAINMENT /EGHV0071 GATE, FW BYPASS EGHV0127 CCW SUPPLY TO CONTAINMENT /EGHV0058 GATE, DD BYPASS EGHV0130 CCW RETURN FROM RCS/EGHV0060 BYPASS GATE, DD EGHV0131 CCW RETURN FROM RCS/EGHV0059 BYPASS GATE, DD EGHV0132 THERMAL BARRIERS /EGHV0062 BYPASS GATE, PS EGHV0133 THERMAL BARRIERS /EGHV0061 BYPASS GATE, PS EJFCV0610 RHR PUMP "A"
MINIFLOW CONTROL GATE, FW Yes EJFCV0611 RHR PUMP "B"
MINIFLOW CONTROL GATE, FW Yes EJHV8701A RCS HL 1 TO RHR PUMP "A" SUCTION ISO GATE, FW Yes Yes EJHV8701B RCS HL 4 TO RHR PUMP "B" SUCTION ISO GATE, FW Yes Yes EJHV8716A RHR "A" TO SIS HOT LEG RECIRC LOOPS 2 GATE, FW
&3 ISO EJHV8716B RHR "B" TO SIS HOT LEG RECIRC LOOPS 2 GATE, FW
& 3 ISO EJHV8804A RHR "A" TO CVCS CCP ISO GATE, FW EJHV8804B RHR "B" SUPPLY TO SI PUMP SUCTION ISO GATE, FW EJHV8809A RHR "A" TO ACCUM INJ LOOPS 1 & 2 ISO GATE, FW EJHV8809B RHR "B" TO ACCUM INJ LOOPS 3 & 4 ISO GATE, FW EJHV8811A CTMT RECIRC SUMP TO RHR PUMP "A"
GATE, FW Yes Yes SUCTION ISO EJHV8811B CTMT RECIRC SUMP TO RHR PUMP "B"
GATE, FW Yes Yes SUCTION ISO EJHV8840 RHR/SI TO HOT LEGS 2 & 3 RECIRC ISO GATE, FW Yes EMHV8801A BIT OUTLET ISO GATE, FW EMHV8801B BIT OUTLET ISO GATE, FW EMHV8802A SI PUMP "A" DISCHARGE TO HOT LEGS 2 &
GATE, FW Yes 3 ISO EMHV8802B SI PUMP "B" DISCHARGE TO HOT LEGS 1 &
EMHV8803A CHARGING PUMP DISCH HDR TO BIT ISO GATE, FW EMHV8803B CHARGING PUMP DISCH HDR TO BIT ISO GATE, FW EMHV8807A iHR HX A/CVCS TO SI PUMP A&B SUCTION GATE, FW EMHV8807B RHR HX A/CVCS TO SI PUMP A&B SUCTION GATE, FW EMHV8821A TO ACCUMULATOR INJECTION ISO GATE, FW EMHV8821B TO ACCUMULATOR INJECTION ISO GATE, FW EMHV8835 ACCUMULATOR INJECTION COLD LEG ISO GATE, FW EMHV8923A SI PUMP "A"
EMHV8923B
~
GATE, FW
I l
1 l
At' tach' ment III to WO 96-0023 Page 3 of 3
]Lesults of Screenino Evaluation of Motor Operated Gate Valves (cont.)
l l
Pressure Thermal Locking Binding Valve ID Valve Evaluation Evaluation j
Number Valve Description Type
- Required Required 1
ENHV0001 TO CONTAINMENT SPRAY PUMP "A" ISO GATE, FW Yes Yes ENHV0006 CONTAINMENT SPRAY PUMP "A"
DISCHARGE GATE, FW ISO ENHV0007 TO CONTAINMENT SPRAY PUMP "B"
ENHV0012 CONTAINMENT SPRAY PUMP "B" DISCHARGE GATE, FW ISO ENHV0015 SPRAY ADDITIVE EDUCTOR "A"
ISO GATE, FW ENHV0016 SPRAY ADDITIVE EDUCTOR "B"
ISO GATE, FW KCHV0253 FIRE PROTECTION CONTAINMENT ISO GATE, PS LFFV0095 CONTAINMENT NORMAL SUMP DISCHARGE ISO GATE, FW LFHV0105 AUX BUILDING SUMP PUMP DISCHARGE ISO GATE, FW LFHVC106 AUX BUILDING SUMP PUMP DISCHARGE ISO GATE, FW l
Additional Valves Added to the Initial Screenincr Motor Operated EPHV8808A SI ACC TANK A OUTLET ISO GATE, FW EPHV8808B SI ACC TANK B OUTLET ISO GATE, FW EPHV8808C SI ACC TANK C OUTLET ISO GATE, FW EPHV8808D SI ACC TANK D OUTLET ISO GATE, FW Hyd.
Operated ABHV0011 SG "D" MAIN STEAM LINE ISO GATE, DD ABHV0014 SG "A" MAIN STEAM LINE ISO GATE, DD ABHV0017 SG "B" MAIN STEAM LINE ISO GATE, DD ABHV0020 SG "C" MAIN STEAM LINE ISO GATE, DD AEFV0039 SG "A"
FW SUPPLY ISO GATE, DD AEFV0040 SG "B"
FW SUPPLY ISO GATE, DD AEFV0041 SG "C"
FW SUPPLY ISO GATE, DD AEFV0042 SG "D"
{
l Xt'tachEnsnt IV to WO 96-0023 page 1 of 6 i
l SUMMARIES OF DETAILED EVALUATIONS OF POTENTIALLY SUSCEPTIBLE VALVES BBPV8702h & B, RRR System Suction from RCS Hot Leg Isolation BJHV8701A & Ba RRR System Suction from RCS Hot Leg Isolation DeAcription BBPV8702A & B and EJHV8701A & B are 12 inch, 1525 psi Westinghouse flexible wedge gate valves in the suction lines from the RCS hot legs that lead to the RHR pump suctions.
Valves BBPV8702 and EJHV8701 are in series; the BBPV8702 valve being closest to the RCS.
The valves are located inside containment and each is equipped with an SMB-2-80 Limitorque motor operator.
These valves are remotely operated from the control room.
Normal containment temperature is never greater than 120*F when these valves are required to operate. These valves are not used to I
mitigate the effects of a LOCA but are used after a steamline break in containment.
The valve bonnets are insulted and not exposed to active steam heating.
Valve Functions The valves in these lines are closed during normal power operation with power removed from BBpV8702A & B.
These valves are not required to bring the plant to a j
safe shutdown condition.
They are opened after the plant is cooled down to l
approximately 350*F, as part of establishing RHR circulation for further cooldown l
to cold shutdown and also provide cooling during refueling or during plant maintenance.
l EyA uantion for Thermal Binding l
Thermal binding could occur in these valves if a valve is closed after operating l
at 3 5 0*F during RHR cooling and then desired to be opened again at a lower temperature.
To avoid this unlikely situation, procedure changes will be made to caution the operators about closing these valves after hot system fluids have flowed through them.
These changes ensure that the valves, which have flexible wedges, are not subjected to more than a 10 0'F temperature decrease in the i
continuous closed position.
Analyses provided by the Westinghouse owners Group show that a 100'F temperature change is acceptable for valves with flexible wedges and that the likelihood of thermal binding occurs at temperatures above 200*F.
Evaluation for Pressure Locking Pressure locking is not a concern for these valves because they do not have to operate following a Loss of Coolant Accident (LOCA) depressurization.
Operation i
l following a steam line break accident is not required until eight hours after the accident and no rapid depressurization of the primary system occurs.
Thermally induced pressure locking is a possibility for these valves under j
conditions where the valves are closed cold and are then heated up by conduction from the RCS.
To avoid this unlikely condition, procedure changes will be made to caution the operators about having one of these valves closed during plant heat up evolutions.
i l
I i
l 1
i
Attachment IV to WO 96-0023 page 2 of 6 RJFCV0610 & 0611, RHR Pump Minimum Flow Recirculation Valves Description EJFCV0610 and 0611 are 3 inch, 2035 psi flexible wedge Westinghouse gate valves.
They are used to ensure a minimum flow rate through the RHR pumps.
They have SMB-000-10 Limitorque motor operators.
The valves are located in the RHR pump room that is cooled by a safety-related room cooler.
Valva Functione These valves are open during normal plant operation.
They provide protection to the RHR pump by ensuring that the RHR pump discharge flow is greater than the minimum pump requirements.
They automatically open when the flow drops below approximately 800 gpm and automatically close when the RHR discharge flow reaches approximately 1,600 gpm.
If the valve fails to close for any reason, flow to the
+
RCS is diminished.
The minimum flow to the RCS is still ensured by the redundant l
system.
If the valve were to fail to open for any reason, the RHR pump could be
[
damaged as a result of too. low a flow rate.
The safety function to guard against for pressure locking and thermal binding effects is failure to open.
Evaluation for Thermal B4nding These valves can open and close automatically during operation of the RHR pumps if flow adjustments are made, mispositioning a valve in the pump flow path is considered or RCS pressure increases unexpectedly.
These pump flow fluctuations can cause thermal transients on this valve as it automatically cycles.
Exposure to adverse thermal transient conditions is considered more likely during plant heat-up than cooldown.
A design change has been issued to limit close, rather than torque close these valves.
The design change will stop the operator on a limit switch control (soft seat) when the disk is approximately 1/2 inch from the fully seated position.
One valve has been modified and the other will be modified during the current refueling outage. This change will preclude thermal binding.
Evaluation for Prasaura Locking There is no concern for pressure locking of these valves.
Ahtac' ment IV to WO 96-0023 h
page 3 of 6 BJHV8811A & B, Residual Heat Removal System Suction from Containment Recirculation Sump Isolation I
Dancription EJHV8811A & B are 14 inch, 316 psi flexible wedge Westinghouse gate valves that provide isolation between the containment building sump and the RHR pumps.
These valves are located in the auxiliary building pipe chase and are encapsulated.
The valves are not exposed to significant ambient temperature changes.
The valves have SB-1-60 Limitorque motor operators.
Valva Punctiona These valves are closed during normal operation.
They are opened on a safety injection signal coincident with a refueling water storage tank (RWST) low-low level signal to supply water to the RHR pumps when switching from the injection to recirculation mode of operation.
They are stroke tested during cold operating
- modes, 6
Evaluation for Thermal Bindina These valves are not closed in a hot condition and are not susceptible to thermal binding. Stroke testing is restricted to cold operating modes.
Eyaluation for Pressure Lockina_
pressure locking of these valves could possibly occur under two scenarios,
- a. Water can fill the bonnets of these valves from either the static head of the RWST or from the RHR system. Following a LOCA, elevated temperature water can enter the sump pipes causing the valves to heat up, thereby causing thermally induced pressure locking.
- b. There is a potential for the valves to pressure lock by thermal effects during a normal plant shutdown (closed loop).
Because the subject valves are connected to the RHR pipe by approximately a 10 foot long horizontal run, the l
valves can be heated to 350'F by water flowing through the RHR pipe early in j
the cooldown (closed loop).
This could cause thermally induced pressure locking of the valves.
However, this condition occurs when RHR containment sump recirculation is not required (open loop).
This condition can be i
detected during stroke testing which is done at temperatures less than 200*F.
Accordingly, this would not pose a safety risk be'cause closed loop RHR operation, not open loop, is required at this time.
Corrective action has been taken, and further action is planned, to ensure that
'these valves will not pressure lock. These corrective actions are as follows:
- 1. A temporary modification was made to fill the containment sumps with water.
If the sumps are already filled with cold water prior to a LOCA, hot water produced during the LOCA cannot enter the pipes and heat the valves to the point where pressure locking occurs.
- 2. These valves will be modified during the current refueling outage to add air reservoirs to the tops of the valve bonnets. The air reservoirs will be sized to ensure that enough air is trapped in the bonnet to keep the bonnet pressures within the capability of the motor operators to open the valves.
Attachmbnt IV to WO 96-0023 Page 4 of 6 RJHV8840, Residual Heat Removal to Hot Leg Recirculation Isolation Dancription EJHV8840 is a 10 inch, 1525 psi flexible wedge Westinghouse gate valve that is normally closed with power locked out.
It is installed in the RHR system and isolates the hot leg injection line from the RHR heat exchanger discharge headers.
It is located outside containment in the pipe penetration room where it is not subject to significant ambient temperature changes based on actual 1988 test data.
The valve has a SBD-3-150 Limitorque motor operator.
Valva Functions This valve remains closed during normal operation.
It is opened and close'd-for stroke testing during refueling outages and opened to permit hot leg recirculation 10 hours1.157407e-4 days <br />0.00278 hours <br />1.653439e-5 weeks <br />3.805e-6 months <br /> after a LOCA.
Evaluation fo-Thermal Bindina This valve is not susceptible to thermal binding.
Evaluation for Prasaura Lockina There is one scenario in which the valve could potentially be susceptible to pressure locking.
This valve is normally closed and is isolated from the RCS by two check valves in series.
Because check valves are subject to leakage there is potential for the downstream side of this valve to become pressurized to the RCS pressure of 2,235 psi and if leakage past the downstream seat were to occur with the bonnet water solid, pressure of 2,235 psi can exist in the bonnet.
Following a LOCA, the downstream side of the valve would be depressurized resulting in pressure entrapment.
The upstream side of the valve would be at a relatively low pressure.
To limit the potential to pressure lock these valves to an acceptable level, the-pressure on the down stream side of the valves will be administratively controlled and monitored.
If there is indication of RCS pressures, the pressure in this location will be relieved to an acceptable level.
Long range plans are being made to eliminate the hot leg recirculation safety function of this valve through a Westinghouse initiative.
i L
~ ~ ' " ~
1 AItac'hbient IV to WO 96-0023 page 5 of 6 RNNV8802A & B, Safety Injection Pump Discharge to RCS Hot Z,eg Isolation Dam.CIlption t
EMHV8802A & B are 4 inch, 1525 psi flexible wedge Westinghouse gate valves that are normally closed.
They are part of the RCS boundary and isolate the discharge of the safety injection pumps from the RCS hot legs.
They are located in the piping penetration room adjacent to containment.
These valves are not subject to significant ambient temperature changes.
The valves have SBD-00-15 Limitorque motor-operators.
Valva Functions These valves are closed during normal operation with power locked out.
They are opened and closed quarterly during testing and are opened to permit hot leg recirculation 10 hours1.157407e-4 days <br />0.00278 hours <br />1.653439e-5 weeks <br />3.805e-6 months <br /> after a LOCA.
Evaluation for Thermal Binding These valves are not subject to thermal binding.
Evaluation for Pressure Locking There are two scenarios in which these valves could potentially be susceptible to pressure locking.
Each valve is normally closed and is isolated from the RCS by-two check valves in series leading to two RCS hot legs.
Because check valves are subject to leakage, there is potential for the downstream side of this valve to become pressurized to the RCS pressure of 2,235 psi and for leakage past the seat to fill the valve bonnet to this pressure.
Following a large break LOCA, the downstream sides of the valves would be rapidly depressurized leading to pressure locking.
In the second scenario, the bonnet could be filled with water at the safety injection pump pressure of approximately 1,700 psi in the interval when switching from cold to hot leg recirculation.
Both of these scenarios could result in pressure locking if the operator is not capable of overcoming this bonnet pressure.
However, pressure locking does not pose a safety risk for these valves because analyses show that the operators are capable of opening these valves with the. bennet at pressures greater than RCS pressure.
In the longer term, plans are being made to eliminate the hot leg recirculation safety function of this valve through a Westinghouse initiative.
Attachm'ent IV to WO 96-0023 page 6 of 6 RNNV0001 & 0007, Containment Spray Pump Suction from Containment Recirculation Sump Isolation Description ENHV0001 and 0007 are 12 inch, 150 psi flexible wedge Anchor Darling gate valves that are normally closed. They isolate the suction of the containment spray pumps from the containment sump.
They are located in the auxiliary building pipe chase and-are encapsulated valves that are not exposed to significant ambient j
temperature changes. The valves have SMB-00-15 Limitorque motor operators.
)
valva Functinna These valves are closed during normal operation.
They are opened on a RWST low-low level to supply water to the containment spray pumps when the plant is switched from the injection mode to the recirculation mode.
Evaluation for Thermal Binding These valves are not closed in a hot condition and are not susceptible to thermal 1
binding.
1 Ryaluation for Pressure Locking j
Pressure locking of these valves could possibly occur under the following j
scenario.
During operation, the downstream sides of these valves and their bonnets could become filled with water from the RWST as a result of leakage past the check valves.
Following a LOCA, elevated temperature water can enter the sump pipes causing the valves to heat up, thereby causing thermally induced pressure locking.
Corrective action has been implemented, and further action is planned, to ensure that these valves will not pressure lock.
These corrective actions are as follows:
- 1. A temporary modification was made to fill the containment sumps with water.
If the sumps are already filled with cold water prior to a LOCA, hot water produced during the LOCA' cannot enter the pipes and heat the valves to the point where pressure locking occurs.
2.
These valves will be modified during the current refueling outage to add air reservoirs to the tops of the valve bonnets.
The air reservoirs will be sized to ensure that enough air is trapped in the bonnet to keep the bonnet pressures within the capability of the motor operators to open the valves.
._