ML20097F259
| ML20097F259 | |
| Person / Time | |
|---|---|
| Site: | Seabrook  |
| Issue date: | 02/08/1996 |
| From: | Brown P NORTH ATLANTIC ENERGY SERVICE CORP. (NAESCO) |
| To: | |
| Shared Package | |
| ML20097F257 | List: |
| References | |
| GL-95-07, GL-95-7, NUDOCS 9602150373 | |
| Download: ML20097F259 (17) | |
Text
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NORTII ATLANTIC ENERGY SERVICES COMPANY SEABROOK STATION GENERIC LETTER 95-07 PRESSURE LOCKING AND TIIERMAL BINDING OF POWER-OPERATED GATE VALVES l
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TABLE dF CONTENTS PAGE TABLES ii l
l.0 EXECUTIVE
SUMMARY
l 2.0 PURPOSE 1
3.0 BACKGROUND
1 4.0 DISCUSSION 2
i 5.0 METilODOLOGY 3
5.1 APPROACH 5.2 THERMAL BINDING 5.3 LIQUID ENTRAPMENT PRESSURE LOCKING 5.4 DIFFERENTIAL PRESSURE LOCKING 5.5 CORRECTIVE ACTIONS 1
4 5.5.1 S110RTTERM ACTIONS 5.5.2 LONG TERM CORRECTIVE ACTIONS 6.0 PRESSURE LOCKING / THERMAL BINDING STAGE 1 EVALUATION 5
7.0 PRESSURE LOCKINGfrHERMAL BINDING STAGE 2 EVALUATION 8
8.0 PRESSURE LOCKINGfrHERMAL BINDING STAGE 3 EVALUATION 10
9.0 CONCLUSION
13
10.0 REFERENCES
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l i
l l
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TABLES TABLE OF CONTENTS PAGE Table 1: PLfrB Evaluation Stage i Valves 6
Table 2:
PL/TB Evaluation Stage 2 Valves 8
Table 3:
PL/TB Evaluation Stage 3 Valves 10 J
d
i 1.0 EXECUTIVE SUMM ARY This document describes the actions taken by Seabrook Station to address NRC Generic Letter 95-07,
" Pressure Locking and Hermal Binding of Safety-Related Power-Operated Gate Valves" All safety-related power-operated gate valves were evaluated for susceptibility to the pressure locking and thermal binding phenomena. In addition, power operated gate valves in selected non safety-related systems were also evaluated. The pressure locking and thermal binding evaluation was performed in stages. Initially, normally closed safety-related motor-operated gate valves that had a safety function to open were evaluated.
Additionally, open valves that are subjected to high system fluid temperatures and are required to close or may be required to close and then reopen were also evaluated for the potential for thermal binding. Normally open safety-related gate valves were then reviewed for their susceptibility to both pressure locking and thermal binding. The initial two stages evaluated the gate valve population that met the scope of Generic Letter 89-10," Safety-Related Motor-Operated Valve Testing and Surveillance". Pneumatic and solenoid operated power-operated gate valves were subsequently identified and evaluated to determine their susceptibility to pressure locking and/or thermal binding. Finally, non safety-related power-operated gate valves were evaluated. The evaluation identified gate valves that are required to open to perform a safety i
ftmetion and identifying system and environmental conditions to determine if the valve was susceptible to pressure locking and/or thermal binding. Engineering Evaluation 95-07 documents the results of the i
evaluations performed.
An operability determination was perfonned on safety-related gate valves that were determined to be potentially susceptible to pressure locking as part of Engineering Evaluation 95-07. The conclusions for each operability determination were included in Adverse Condition Report (ACR) 95-34. A total of twelve valves were identified as being potentially susceptible to thermal binding, pressure locking or both thermal binding and pressure locking. A procedure change was recommended for two of the valves that were i
determined to be potentially susceptible to thermal binding. Valve and system modifications were performed during the fourth refueling outage in accordance with Design Coordination Report (DCR)95-023 and Minor Modification (MMOD)95-509 to climinate the potential for pressure locking for ten motor-operated gate 2
valves.
2.0 PURPOSE The purpose of this document is to summarize the actions taken to address the recommendations provided in NRC Generic Letter 95-07. MOV design changes that have been incorporated to address potential pressure locking and thermal binding concerns are also discussed.
3.0 HACKGROUND The NRC issued NRC Generic Letter 95-07, " Pressure Locking and Thermal Binding of Safety-Related Power-Operated Gate Valves" on August 17,1995. This generic letter requested that licensees perform or confinn that they have previously performed, (1) evaluations of operational configurations of safety-related, power-operated (including motor, air-and hydraulically operated) gate valves for susceptibility to pressure locking and thermal binding and (2) further analysis, and any needed corrective actions, to ensure that safety-related power-operated gate valves that are susceptible to pressure locking or thermal binding are capable of perfonning the safety functions within the current licensing basis of the facility.
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The NRC'had previously provided guidance on an acceptable approach for addressing pressure locking and thermal binding of motor-operated valves (MOVs) in Supplement 6 to Generic Letter 89-10. Generic Letter 95-07 confinns that licensees are expected, under existing regulations, to take actions as necessary to ensure that safety-related power-operated gate valves susceptible to pressure locking or thermal binding are capable of performing their required safety functions.
The NRC issued NUREG-1275, Volume 9," Pressure Locking and Thermal Binding of Gate Valves"in March of 1993. This NUREG gave the history of pressure locking and thermal binding events, described the phenomena, discussed the consequences of pressurc locking or thermal binding on valve functionality, summarized preventive measures, and assessed the safety significance of the phenomena. Pressure locking l
or thermal binding can cause a power operated gate valve to fail to open, resulting in an inability of the l
associated safety train or system to perform its safety function. Pressure locking and thermal binding represents a potential common cause failure mode that can render redundant trains of certain safety-related l
or multiple safety related systems incapable of performing their safety functions.
l Seabrook Station had performed previous evaluations for pressure locking and thermal binding of gate valves. Independent Safety Engineering Group (ISEG) Memo 8801-004," Pressure Locking and Thermal Binding of Gate Valves" was issued to address INPO SOER 84-7. Engineering Evaluation 93-33," Thermal l
Binding and Pressure Locking of Safety Related Gate Valves" was prepared to address NRC Information Notice 92-26, " Pressure Locking of Motor Operated Flexible Wedge Gate Valves" 4.0 DISCUSSION Seabrook Station performed a re-evaluation of the conclusions reached in Engineering Evaluation 93-33.
This re-evaluation is documented in Engineering Evaluation 95-07, " Pressure Locking and Thermal Binding of Gate Valves" The re-evaluation was warranted based on questions regarding the potential for liquid entrapment pressure locking that was raised at other plants. Information Notice IN 95-14: " Susceptibility of Containment Sump Recirculation Gate Valves to Pressure Locking", identined the potential for liquid l
entrapment pressure locking of the containment sump suction valves. Engineering Evaluation 95-07 l
documents the screening evaluation and operability determination requirements for NRC Generic Letter 95-07, " Pressure Locking and Thennal Binding of Safety-Related Power-Operated Gate Valves" Motor operated gate valves are susceptible to thermal binding and pressure locking under certain operating conditions. This problem is a concern for those valves which must open in order to perform their safety I
function. When a valve is experiencing thermal binding or pressure locking, it is possible that the motor operator will not be able to provide sufficient force to open the valve. There are three mechanisms for thennal binding or pressure locking to occur. A description of these mechanisms follows-l Thermal Binding. When a wedge gate valve is closed while the system is hot, thermal binding of the valve can occur as the system cools. The valve body and disc could mechanically interfere because of the different thennal expansion and contraction characteristics of the valve body and the disc. The difference in thermal contraction, the valve body contracting a proportionally greater amount than the valve disc, can cause the seats to bind the disc so tightly that reopening the valve is either very difficult or impossible until the valve is reheated. It is important to note that double-disc, parallel-seat gate valves are not as susceptible to thermal binding as flexible-wedge gate valves. This is due to the fact that the wedging mechanism between the double discs collapses as the stem rises, thus, permitting the parallel discs to move imvard and raise regardless of the change in system temperature. Excessive closing force can contribute to thermal binding because excessive closing force causes the disc to be driven into the seat more tightly and upon cooling the 2
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thermal binding effect is increased. Solid-wedge gate valves are most susceptible to thermal binding.
However, flexible-wedge gate valves experiencing significant temperature changes or operating with significant upstream and downstream temperature differences may also be susceptible to thermally binding.
Liquid Enkapment Pressure Locking. When a gate valve is closed with a system full of cold liquid, the liquid becomes trapped in the bonnet cavity. A subsequent temperature increase of the fluid will cause an increase in bonnet cavity pressure due to thermal expansion of the fluid. A condition results where a high pressure in the valve bonnet and disc is produced if not relieved. The pressure buildup would be significant if there is no air trapped in the bonnet and the valve disc / seat and/or the packing did not leak. The valve does not have to be in a high temperature system but only in close proximity to a high temperature system where heat conduction through the pipe or the environment will heat the trapped fluid in the valve bonnet. The rate of pressure rise can be as high as 100 psi per F temperature increase for a water solid bonnet for system temperatures above 450 F. For lower system temperatures (~ 100 F) the rate of pressure rise is approximately 33 psi per F of temperature rise. High pressure forces the disc more tightly against the seat or, in extreme cases, permanently deforms the valve bonnet or disc. Valves that are closed in a cold liquid-filled system and then heated are susceptible to this condition.
Differential Pregsgre Locking. When a system is pressurized after a valve is closed, the pressurized side of the flexible disc may move slightly away from its seat, allowing high pressure liquid to enter the bonnet cavity. This would most likely occur when reactor coolant pressure forces one side of the disc of a normally closed valve away from the valve seat creating a leakage path and pressurizing the bonnet. If the pressure in the system is subsequently decreased, which would occur under a LOCA or other transient condition causing pipe line depressurization, the bonnet pressure would force the disc against one or both seats more tightly than normal if the bonnet pressure is not relieved. The valve actuator may not have been sized for the increased loads due to bonnet pressurization.
5.0 METilODOLOGY The review of the power-operated gate valves to determine their susceptibility to pressure locking and thermal binding consisted of the following:
5.1 Approach The review of the Seabrook Station's power-operated gate valves for potential susceptibility to pressure locking and thermal binding was performed in three stages. The following provides a brief description of the three stages used to evaluate the power-operated gate valves at Seabrook.
During the initial stage, normally closed safety related motor-operated valves along with selected normally open motor-operated gate valves which are included in Scabrook's Generic Letter 89-10 Program were reviewed for susceptibility to the phenomena. There were 26 valves evaluated during this stage of the evaluation.
In the second stage, the remaining nomially open safety-related motor-operated gate valves that are included in the Generic Letter 89-10 MOV Program were then reviewed. There were 29 valves evaluated during the second stage of the evaluation.
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In'the last' stage, most of the non-safety-related motor-operated gate valves as well as air-operated and solenoid operated gate valves were reviewed for susceptibility to pressure locking and thermal binding.
There were 36 motor-operated gate valves reviewed during this stage of the evaluation. The power-operated containment isolation gate valves that were not motor-operated valves were identified by using UFSAR Table 6.2.83, " Containment Isolation System Design Information" There were 15 non-MOV power operated gate valves that met this criteria. Air-operated gate valves were identified using the Air-Operated Valve (AOV) List. This list was used in conjunction with a Probabilistic Risk Assessment (PRA) to prioritize the valves in the list. Another group ofgate valves was identified by using the Automated Valve List, the Engineering data base, the Commonality database, applicable component specifications and vendor prints. There were an additional 10 air-operated gate valves identified in this review. Several systems were not considered for evaluation, based on the lack of plant operational consequences due to pressure locking, thermal binding or because they are gaseous or air systems which are not susceptible to the phenomena.
ilowever, systems in contact with the containment atmosphere were evaluated because of their potential exposure to high temperature and condensate. The nongaseous systems that were excluded from evaluation were Boron Recovery, Chilled Water, Chlorination, Hot Water Heating, Solid Waste Processing and Water Treatment. Solenoid power-operated gate valves were identified during the review of vendor manuals for the suppliers, Valcor and ASCO. A subsequent review of P&lDs identified additional ASCO valves, that were
- included on skid-mounted equipment supplied by other vendors. There were no additional solenoid power-operated gate valves identified as a result of this review. Electro-hydraulic and hydraulic-pneumatic power-operated gate valves were identified by P&lD, engineering database and/or vendor print review as applicable.
There were no additional power-operated gate valves identified as a result of this review.
All of the identified power-operated gate valves were then reviewed for their susceptibility to liquid entrapment and differential pressure locking and thermal binding. For normally closed power-operated gate valves, each individual valve was evaluated to determine ifit must open to perform a safety function. For normally open power-operated gate valves, each valve was evaluated to determine ifit must close and must re-open after closure to perform a safety function. Additionally, the valve was evaluated for pressure locking and thermal binding under normal operating conditions. The evaluation consisted of the following:
5.2 Thermal Binding Valves were determined to be potentially susceptible to thermal binding if they are open while the system temperatures are relatively high and are closed and the system is subsequently cooled. If the open stroke did not have any safety significance, no further actions were required. If the valve susceptible to thermal binding is required to open to perform a safety function then additional evaluation / corrective action was required to assure valve operability.
5.3 Liquid Entrapment Pressure Locking Each valve was evaluated by determining if the valve is closed or could be closed and subsequently could be heated by the system process temperature or the environment. Changes in environmental temperature were i
identified if they were step changes due to a high energy line break or an accident. Normal ambient temperature swings based on seasonal weather changes were not considered. Valves meeting this criteria were identified as being potentially susceptible to liquid entrapment pressure locking. If the valve did not have to open to perform its safety function no further actions were taken. If the valve is required to open to perform its safety function both short term actions and long term corrective actions were performed.
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5.4 D'ifferential Pressure Locking
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Valves were evaluated to determine if the valve is closed or could be closed, the valve bonnet pressurized and the piping subsequently depressurized. Valves meeting this criteria were identified as being potentially susceptible to differential pressure locking. If the valve did not have to open to perform its safety function no further actions were taken. If the valve is required to open to perform its safety function both short tenn actions and long term corrective actions were performed, if not bounded by the conditions determined for liquid entrapment pressure locking.
5.5 Corrective Actions 5.5.1 Short Tenn Actions Valves that were determined to be potentially susceptible to either thermal binding or pressure locking were further evaluated to assure that each identified valve was capable of perfonning its safety function. The valve's operating history was reviewed to determine if any operational occvtrences of pressure locking or thermal binding at Seabrook Station had been identified. For the press ure locking evaluation an additional analysis was performed. If the valve was located in a poteatially hot environment or if the valve could be heated by the process fluid a Gothic valve model was developed to determine the extent of valve bonnet heat up. Valve bonnet pressure was calculated assuming an initial bonnet pressure based on the maximum process fluid pressure and accounting for any increased bonnet pressure due to heat up using a heatup factor of 33 psi per i F increase in bonnet temperature. Valve required thrusts using three different methods were detennined using the maximum bonnet pressure. The required thrust values were compared to the derated motor operator thrust capability and the derated stall thrust capability. Using this approach it was concluded that all ten valves that were identified as being potentially susceptible to pressure locking were determined to be operable.
5.5.2 Long Term Corrective Actions Safety related power-operated gate valves that are required to open to perform their safety ftmetion and were determined to be potentially susceptible to pressure locking were modified by incorporating a way to depressurize the valve bonnet. Valves potentially susceptible to thermal binding were l
addressed by either a qualitative evaluation or by recommending procedure changes as applicable.
6.0 PRESSURE I OCKING/TilERMAL HINDING STAG 1 EVALUATION 1
The following normally closed and selected normally open motor-operated gate valves were included in the first stage of the evaluation. Table 1 identifies the valve, valve function and provides a conclusion of the results of the pressure locking and thennal binding evaluation identifying valves that could be potentially susceptible to pressure locking (PL), thermal binding (TB) or both pressure locking and thennal binding (Pl/fB). Corrective actions taken to address PI/fB for valves identified as being potentially susceptible to either or both phenomena are provided following Table 1.
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I TABLE 1: PL/TB EVALUATION STAGE 1 VALVES VALVEID FUNCTION POT. SUSCEPTIBLE TO PL/TB C BS-V-8 Isolation Valve for Containment Recirc Sump Tank 101 A PL CBS-V-11 Containment Spray lleader Train 'A' Isolation Valve CBS-V-14 Isolation Valve for Containment Recire Sump Tank 101B PL CBS-V-17 Containment Spray 11eader Train 'B' Isolation Valve CBS-V-38 SAT Supply to RWST Isolation Train 'A' CBS-V-43 SAT Supply to RWST isolation Train 'B' CS LCV-112D Charging Pump Suction from RWST - Train 'A' CS-LCV-112E Charging Pump Suction from RWST - Train 'B' CS-V-460 SI And Charging Pump Suction X-Connect from R11 Pump Disch CS-V-461 SI And Charging Pump Suction X-Connect from Ril Pump Disch j
FW-V-156 EFW X-Connect Isolation from SUFP FW-V-163 SUFP X-Connect to EFW lleader RC-V-22 RilR Pump 'A' Suction Isolation from Loop i 110t Leg PIIFB l
RC-V-23 RiiR Pump ' A' Suction Isolation from Loop 1 Ilot Leg Pl/FB RC-V-87 RilR Pump 'B' Suction Isolation from Loop 4 liot Leg Pl/TB RC-V-88 RilR Pump 'B' Suction isolation from Loop 4 Ilot Leg PUTB i
i RC-V-122 PORV 456A Block TB i
RC-V-124 PORV 456B Block TB Ril-V-32 RilR Train 'B' Common Supply to llot Leg Recire PL Ril-V-35 RilR Pump 'A' Discharge Isolation to SI/ Charging Pumps Ril-V-36 RilR Pump 'B' Discharge Isolation to SI/ Charging Pumps Ril V-70 RilR Train 'A' Common Supply to liot Leg Recire PL SI-V-77 Si Train 'B' Discharge Isolation to 110t Legs 1/4 PL S!-V-102 St Train 'A' Discharge Isolation to liot Legs 1/4 PL SI-V-138 Charging Pumps Supply to RCS Cold Legs i
l SI-V-139 Charging Pumps Supply to RCS Cold Legs 4
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CBS-V-8/CBS-V-14 CBS-V-8 and CBS-V-14, the Containment Sump Isolation Valves, were determined to be potentially j
susceptible to liquid entrapment pressure locking. Rese normally closed Velan flexible wedge gate valves l
were modified in Refueling Outage 04 to eliminate the potential for pressure locking. A vent path was installed from the between seat drain to the upstream piping to eliminate the potential for pressurizing the
,j valve bonnet. This work was performed in accordance with Engineering design document MMOD 95-509.
RC-V-22/RC-V-87 j
RC-V-22 and RC-V-87, the RCS to RHR Pump Suction Inboard Isolation Valves, were determined to be potentially susceptible to pressure locking. Rese normally closed Westinghouse flexible wedge gate valves were modified in Refueling Outage 04 to climinate the potential for pressure locking. The valve packing was modified and a vent path was installed from the packing leakoff connection to the upstream piping (RCS l-side) to climinate the potential for pressurizing the valve bonnet. His work was performed in accordance with Engineering design document DCR 95-023.
j RC-V-22 and RC-V-87 were determined to be potentially susceptible to thermal binding. He valves are j
closed when the process temperature is in the 280 F to 340 F range and the valves are subsequently cooled to the ambient containment temperature of approximately 120 F. The closing action in the hot condition and subsequent cooldown to ambient conditions provides the potential for thermal binding. Based on successful
{
operation of these valves for approximately 13 heatup and cooldown cycles there has been no evidence of i
thermal binding. Since this condition is related to the metal thermal expansion coefYicient properties, the 13 successful cycles provides sufficient evidence that the valves are not subject to thermal binding.
RC-V-23/RC-V-88 i
RC-V-23 and RC-V-88, the RCS to RHR Pump Suction Outboard Isolation Valves, were determined to be potentially susceptible to pressure locking. Rese normally closed Westinghouse flexible wedge gate valves were modified in Refueling Outage 04 to eliminate the potential for pressure locking. The valve packing was modified and a vent path was installed from the packing leakoff connection to the upstream piping (RCS l
side) to climinate the potential for pressurizing the valve bonnet. This work was performed in accordance with Engineering design document DCR 95-023.
RC-V-23 and RC-V-88 were determined to be potentially susceptible to thermal binding. He valves are closed when the process temperature is in the 280 F to 340 F range and the valves are subsequently cooled F
to the ambient containment temperature of approximately 120 F. He closing action in the hot condition and subsequent cooldown to ambient conditions provides the potential for thermal binding. Based on successful i
operation of these valves for approximately 13 heatup and cooldown cycles there has been no evidence of thermal binding. Since this condition is related to the metal thermal expansion coefficient properties, the 13 successful cycles provides sufficient evidence that the valves are not subject to thermal binding.
RC-V-122/RC-V-124 '
RC-V-122 and RC-V-124, the PORV Block Valves, were determined to be potentially susceptible to thermal binding. These valves are normally open Westinghouse ficxible wedge gate valves that are exercised quarterly at power and may be closed to isolate a leaking PORV. Reopening these valves to prevent a challenge to the pressurizer safety valves or for a feed and bleed operation would be performed at similar 7
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=
teinperatu're and pressure conditions as existed when the valve was closed, precluding a thermal binding condition. For low temperature overpressure protection functions, the temperature at which the valve would be opened would be considerably lower than the temperature at which the valve was closed, creating the necessary conditions for thermal binding.11owever, LTOP protection can also be provided by the RiiR suction relief valves or by providing an RCS vent path. Therefore, should thermal binding of these valves occur, no safety function would be impaired. Procedure changes have been made to the appropriate operating procedure to address the thermal binding concern.
Ril-V-32/Ril-V-70 Ril V-32 and Ril-V-70, the Low licad flot Leg Recirculation Valves, were determined to be potentially susceptible to pressure locking. These normally closed Westinghouse flexible wedge gate valves were modified in Refueling Outage 04 to climinate the potential for pressure locking. The valve packing was modified and a vent path was installed from the packing leakoff connection to the downstream Si piping (RCS side) to climinate the potential for pressurizing the valve bonnet. This work was performed in accordance with Engineering design document DCR 95-023.
4 SI-V-77/SI-V-102 SI-V-77 and SI V-102, the Intermediate llead 110t Leg Recirculation Valves, were determined to be potentially susceptible to pressure locking. These normally closed Westinghouse flexible wedge gate valves were modified in Refueling Outage 04 to climinate the potential for pressure locking. The valve packing was modified and a vent path was installed from the packing leakoff connection to the downstream piping (RCS side) to eliminate the potential for pressurizing the valve bonnet. This work was performed in accordance with Engineering design document DCR 95-023.
7,0 PRESSURE LOCKING /TilERMAL BINDING STAGE 2 EVALUATION l
The following nonnally open motor-operated gate valves were included in the second stage of the evaluation.
Table 2 identifies the valve, valve function and provides a conclusion of the results of the pressure locking and thermal binding evaluation. Although it could be postulated under certain conditions that some of the evaluated valves may be potentially susceptible to either pressure locking, thermal binding or both, there were no valves identified that have a safety function to re-open following valve closure. Accordingly, no valves in Table 2 were identified as meeting the pressure locking and thermal binding criteria and no corrective actions were required to address PL/TB concerns for valves evaluated in Stage 2.
TABLE 2: PL/TB EVALUATION STAGE 2 VALVES VALVE ID FUNCTION POT. SUSCEPTIHLE TO PL/TB 1
AS-V-175 Train 'A' ilELB ! solation - AUX Steam Supply to PAB And WPB AS-V-176 Train 'B' liELD isolation - AUX Steam Supply to PAB And WPB 8
TABLE 2: PL/TB EVALUATION STAGE 2 VALVES i
VALVE ID FUNCTION POT. SUSCEPTIBLE TO PL/TB CBS-V-2 RWST to R11R/CBS Pump Suction Isolation (Train 'A')
i CBS-V-5 RWST to RilR/CBS Pump Suction Isolation (Train 'B')
CBS-V-47 RWST to S1 Pump 'A' Suction Isolation CBS-V-49 RWST to S1 Pump 'A' Suction isolation CBS-V-S I RWST to SI Pump 'B' Suction isolation CBS-V-53 RWST to Si Pump 'B' Suction isolation CC-V-395 PCCW Isolation from RCP 'B' Thermal Barrier CC-V-428 PCCW Isolation from RCP 'A' Thermal Barrier CC-V-438 PCCW Isolation from RCP 'C' Thermal Barrier CC-V-439 PCCW Isolation from RCP 'D' Thermal Barrier CS-LCV-112B Charging Pump Suction from VCT - Train 'A' CS-LCV-112C Charging Pump Suction from VCT - Train 'B' l
CS-V-142 Train 'A' Charging System to Regen llX Isolation 1
CS V-143 Train 'B' Charging System to Regen llX Isolation i
CS-V-149 Regen llX Outlet to Letdown IIX CS-V-475 SI And Charging Pump Suction X-Connect from Rif Pump Disch Ril-V-14 RliR Train 'A' to Cold Legs 1 And 2 Ril-V-21 Ri1R Train 'B' Discharge X-Connect i
Ril-V-22 R11R Train 'A' Discharge X-Connect Ril-V-26 R11R Train 'B' to Cold Legs 3 And 4 SI-V-3 Accumulator 'A' Discharge Isolation SI-V-17 Accumulator 'B' Discharge Isolation SI-V-32 Accumulator 'C' Discharge isolation SI-V-47 Accumulator 'D' Discharge Isolation SI-V-111 Si Train 'B' Discharge X-Connect SI-V-112 SI Train 'A' Discharge X-Connect SI-V-114 SI Pumps Conunon Isolation to Cold Legs 4
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i 8l0 l RESSURE LOCKING /TilERMAL BINDING STAGE 3 EVALUATION The following power--operated gate valves were included in the third stage of the evaluation. Table 3 j
identifies the valve, identifies whether the valve is safety related (SR) or non nuclear safety-related (NNS),
valve function and provides a conclusion of the results of the pressure locking and thermal binding evaluation. Although it could be postulated under certain conditions that some of the evaluated valves may be potentially susceptible to either pressure locking, thermal binding or both, there were no valves identified that have a safety function to re-open following valve closure. Accordingly, no valves in Table 3 were identified as meeting the pressure locking and thermal binding criteria and no corrective actions were required to address PLffB concerns for valves evaluated in Stage 3 All valves in Table 3 should be considered as having motor-operators unless noted otherwise.
TABLE 3: PL/TB EVALUATION STAGE 3 VALVES VALVE ID SRINNS FUNCTION POT. SUSCEPTIBLE TO PL/TB AB-V-36 NNS Aur. Boiler Deacrator Tank High Level Dump (AOV)
ASC-V-359 NNS Aux Steam Condensate Discharge Retum to Deacrator (AOV)
ASC-V-967 NNS Recirc Supply to Sparger on Aux Steam Condensate Tank (AOV)
Call-FV-6572 SR Containment Radiation Monitoring Isolation (Solenoid-operated)
CAH-FV-6573 SR Containment Radiation Monitoring Isolation (Solenoid-operated)
Call-FV-6574 SR Containment Radiation Monitoring Isolation (Solenoid-operated)
CO-V-59 NNS FW Heaters 21C and 22C Inlet CO-V-71 NNS FW 11 eaters 2i A and 22A Inlet CO-V-73 NNS FW Heaters 21B and 22B Inlet CO-V-75 NNS FW Heaters 21 and 22 'A', 'B', and 'C' Bvpass CO-V-82 NNS FW lleaters 21 A and 22A Outlet CO-V-84 NNS FW Heaters 21B and 22B Outlet CO-V-86 NNS FW Heaters 2 tC and 22C Outlet CS-V-625 SR UD System to PDT Iso from LCV-112A CS-V-633 SR Letdown Degasifier Supply EX-V-1 NNS FW-E-26A Hi/Hi licater Isolation EX-V-4 NNS FW-E-26B Hi/Hi ficater Isolation 10
l TABLE 3: PL/TB EVALUATION STAGE 3 VALVES VALVEID SR/NNS FUNCTION POT. SUSCEPTIBLE TO PL/TB EX-V-13 NNS 24C Hi/Hi lleater Isolation EX-V-16 NNS 23C lii/Hi Heater Isolation EX-V-19 NNS 24B lii/Ili lleater Level Isolation EX-V-22 NNS 23B Hi/Ili licater Isolation EX-V-25 NNS 24A lii/Hi Heater Isolation EX-V-28 NNS 23A Ili/Hi Heater Isolation EX-V-34 NNS Extraction Steam Drain isolation EX-V-35 NNS Extraction Steam Drain isolation FW-V-2 NNS Feed Pump 'A' Discharge Isolation FW-V-13 NNS-Feed Pump 'B' Discharge Isolation FW-V-23 NNS 26A Ileater Outlet Isolation
+
FW-V-25 NNS 26B lleater Outlet Isolation FW-V-28 NNS Feedwater Regulating Block Valve 'A' FW-V-30 SR Main Feedwater Isolation (Hydraulic Pneumatic operated)
}
FW-V-37 NNS Feedwater Regulating Block Valve 'B' l
FW-V-39 SR Main Feedwater Isolation (Hydraulic Pneumatic j
]
operated)
FW-V-46 NNS Feedwater Regulating Block Valve 'C' i
FW-V-48 SR Main Feedwater Isolation (Hydraulic Pneumatic operated)
FW-V-55 NNS Feedwater Regulating Block Valve 'D' FW-V-57 SR Main Feedwater Isolation (Hydraulic Pneumatic operated)
IID-V-240 NNS Heater Drain Tank Vent MS-V-86 SR Main Steam isolation (Hydraulic-Pneumatic operated)
MS-V-88 SR Main Steam isolation (Hydraulic-Pneumatic
)
operated)
MS-V-90 SR Main Steam isolation (Hydraulic-Pneumatic operated) i1
TABLE 3: PL/TB EVALUATION STAGE 3 VALVES VALVEID SR/NNS FUNCTION POT. SUSCEPTIBLE TO PL/TB MS-V-92 SR Main Steam Isolation (Hydraulic-Pneumatic operated)
M S-V-100 NNS Reheater Steam Supply for MSR 'A' MS-V-101 NNS Reheater Steam Supply for MSR 'A' MS-V-150 NNS Reheater Steam Supply for MSR 'D' MS-V-158 NNS Reheater Steam Supply for MSR 'C' MS V-185 NNS Main Steam Supply to Aux Steam Isolation (AOV) a RC-V-81 SR Regenerative 11 cat Exchanger Letdown isolation from Loop 3 S B-V-1 SR Steam Generator Blowdown to Flash Tank isolation (AOV)
S B-V-3 SR Steam Generator Blowdown to Flash Tank isolation (AOV)
SB-V-5 SR Steam Generator Blowdown to Flash Tank Isolation (AOV)
S B-V-7 SR Steam Generator Blowdown to Flash Tank isolation (AOV)
S B-V-9 SR Steam Generator Blowdown Isolation (AOV)
S B-V-10 SR Steam Generator Blowdown isolation (AOV)
S B-V-11 SR Steam Generator Blowdown Isolation (AOV)
SB-V-12 SR Steam Generator Blowdown Isolation (AOV) l SSS-V-18 NNS Steam Seal ficader Bvpass to Condenser SSS-V-20 NNS Steam Seal Feed Valve Isolation SSS-V-22 NNS Steam Seal Auxiliary Steam Isolation WL-V-166 NNS Waste Test Tank Isolation (AOV)
WL-V-168 NNS Waste Test Tank Isolation (AOV) 1 12
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9.0 CONCLUSION
This report documents Seabrook's actions that were taken to implement the recommendations provided in NRC Generic Letter 95-07. Twelve valves were identified as being potentially susceptible to thermal binding, pressure locking or both thermal binding and pressure locking. A procedure change was implemented for two of the valves that were determined to be potentially susceptible to thermal binding.
Valve and system modifications were performed during the fourth refueling outage in accordance with Design Coordination Report (DCR)95-023 and Minor Modification (MMOD)95-509 to eliminate the potential for pressure locking for ten motor-operated gate valves. No additional actions regarding pressure locking and thermal binding are planned.
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15.
IkEFERENCES 1.
Engineering Evaluation 95-07, " Pressure Locking and Thermal Binding of Safety-Related Power-Operated Gate Valves".
2.
NUREG-1275 Volume 9," Pressure Locking and Thermal Binding of Gate Valves" 3.
AEOD Special Study AEOD/S92-07, " Pressure Locking and Thermal Binding of Gate Valves" 4.
DCR 95-023 5.
MMOD 95-509 6.
- 1. E. Notice 92-26, " Pressure Locking of Motor-Operated Flexible Wedge Gate Valves" 7.
Engineering Evaluation 93-33, " Thermal Binding and Pressure Locking of Safety Related Gate Valves" 8.
INPO SOER 84-7, " Pressure Locking and Thennal Binding of Gate Valves" 9.
NAESCO Letter NYN-95080, " Response to Generic Letter 95-07" dated October 13,1995 l
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