ML20097E780
| ML20097E780 | |
| Person / Time | |
|---|---|
| Site: | Waterford  |
| Issue date: | 02/13/1996 |
| From: | Burski R ENTERGY OPERATIONS, INC. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| GL-95-07, GL-95-7, W3F1-96-0013, W3F1-96-13, NUDOCS 9602140264 | |
| Download: ML20097E780 (16) | |
Text
-.
- p. 9
" ENTERGY M "*""'""*'
Killona. LA 70066 Tel 504 739 6774 R. F. Burski rd W3F1-96-0013 A4.05 PR February 13,1996 U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, D.C. 20555
Subject:
Waterford 3 SES Docket No. 50-382 i
License No. NPF-38 NRC Generic Letter 95-07 Gentlemen:
The NRC on August 17,1995 issued Generic Letter 95-07, " Pressure Locking and Thermal Binding of Safety Related Power-Operated Gate Valves." The NRC requested that licensees provide the following information within 180 days of the date of the Generic Letter:
1.
The susceptibility evaluation O' operational configurations and further analyses performed in resp e to (or consistent with) the requested actions, as well as, the criteria for determining susceptibility to pressure locking or thermal binding.
2.
The resuits of the susceptibility evaluation and any further analyses including a listing of the susceptible valves identified.
3.
The corrective actions, or other dispositioning, (including completion schedule) for the valves identified as susceptible to pressure locking er thermal binding.
This letter provides the foregoing information in the attached report.
I 944Crse c
9602140264 960213 h[U PDR ADOCK 05000302 P
(
l
NRC Generic Letter 95-07 W3F1-96-0013 Page 2 February 13,1996 Please contact me or Robert J. Murillo at (504) 739-6715, should there be any j
questions regarding this submittal.
l Very truly yours, c
Y-lk At^
W 9
R.F. Burski Director Nuclear Safety 4
RFB/RJM/ssf Attachment cc:
L.J. Callan, NRC Region IV C.P. Patel, NRC-NRR R.B. McGehee N.S. Reynolds I
NRC Resident inspectors Office
= '
9 L
ll
~
UNITED STATES OF AMERICA i-NUCLEAR REGULATORY COMMISSION I
In the matter of
.)
)
Entergy Operations, Incorporated
)
Docket No. 50-382
- Waterford 3 Steam Electric Station
)
AFF'9AVIT'
. William Harold Pendergrass, being duly sworn, hereby deposes and says that he is (Acting) Director, Nuclear Safety - Waterford 3 of Entergy Operations, incorporated; that he is duly authorized to sign and file with the Nuclear Regulatory Commission the attached Response to NRC Generic Letter 95-07; that he is familiar with the content thereof; and that the matters set forth therein are true and correct to the best of his knowledge, information and belief.
k),Ww kandA wd wo
~
William Harold Pendergrass (Acting) Director, Nuclear Safety - Waterford 3 STATE OF LOUISIANA
)
) ss PARISH OF ST. CHARLES
)
L Subscribed and sworn to before me, a Notary Public in and for the Parish and State above named this I &* day of FE a n v A u
.1996.
3 a E '. Ic Q Notary Public My Commission expires cv < m
'*u r
p,y-p e
a
. s
._m
_aA
.A
.aA
_a J
w-
.h44 A.
4..
4.-5-.
.A 4
-.w.a, 4
43 4m J
ENTERGY OPERATIONS WATERFORD 3 STEAM ELECTRIC STATION NRC GENERIC LETTER 95-07 180 DAY RESPONSE l
l i
i 4
i t
e ll I
i
NRC GInIric LettIr 95-07180 DIy RIsp:nse TABLE OF CONTENTS Section Title Paae 1.0 l N T RO D U CTI O N............................................................................. 1 i
2.0 SCOPE............................................................................................2
3.0 REFERENCES
................................................................................3 4.0 THERMAL BINDING & BONNET PRESSURIZATION EVA L U ATIO N C RITE RI A................................................................ 4 4.1 Thermal Binding Evaluation Criteria................................ 4 4.2 Hydraulic Locking Evaluation Criteria.
.........................5 4.4 Boiler Effect Evaluation Criteria...............................6 i
5.0 EVA L U ATI O N R E S U LTS................................................................ 8 6.0 WATE R FO R D 3 ACTIO N P LAN.................................................... 10 APPENDIX l WATERFORD 3 SES GL 95-07 VALVE LIST (1 page)
)
1 4
i d
3 1
~ - - - -
NRC Generic Lett:r 96-07180 Day R:sp nse
1.0 INTRODUCTION
The Nuclear Regulatory Commission issued Generic Letter 95-07: Pressure Locking and Thermal Binding of Safety-Related Power-Operated Gate Valves to request that licensees perform evaluations of operational configurations of safety-related, power-operated gate valves for susceptibility to pressure locking and thermal binding and perform any needed evaluations or corrective actions.
Valve failures due to pressure locking and thermal binding have prevented safety-related systems from performing their required function. Binding of the valve disc in the closed position due to differential thermal contraction (i.e.,
thermal binding) or high pressure water trapped in the bonnet cavity (i.e.,
pressure or hydraulic locking) represent potential common mode failure mechanisms for these valves.
As part of the response to GL 95-07 the NRC requested that within 90 days of issuance of the generic letter, each licensee complete the following actions:
- 1. Perform a screening evaluation of the operational configurations of all safety-related power-operated (i.e., motor operated, air operated and hydraulically operated) gate valves to identify those valves that are potentially susceptible to pressure locking or thermal binding; and
- 2. Document a basis for the operability of the potentially susceptible valves or, where operability cannot be supported, take action in accordance with individua! plant Technical Specifications.
In addition, the NRC requested that within 180 days of issuance of the generic letter, each licensee perform further analyses as appropriate, and take needed j
corrective actions (or justify longer schedules), to ensure that the susceptible valves identified are capable of performing their intended safety function (s) i under all modes of plant operation, including test configuration.
i j'
The NRC requested that the following information be submitted within 180 days j
of issuance of the generic letter.
j
- 1. The susceptibility evaluation of operational configurations and further analyses performed in response to (or consistent with) the requested actions, j
as well as, the criteria for determining susceptibility to pressure locking or thermal binding.
i L
- 2. The results of the susceptibility evaluation and any further analyses including a listing of the susceptible valves identified.
- 3. The corrective actions, or other dispositioning, (including completion schedule) for the valves identified as susceptible to pressure locking or thermal binding.
1 j.
NRC Generic LettIr 95-O'l 180 Day R:sp ns) 2.0 SCOPE This report documents the status of the forty-eight (48) power-operated valves evaluated under GL 95-07. These valves represent all safety-related power-operated gate valves at Waterford 3. Appendix l provides a listing of all GL 95-07 valves, operators, gate types and function.
The evaluations encompass all system modes of operation which are within the plant's design basis. The evaluations were completed through review of the Waterford 3 system operating and emergency operation procedures, the system design basis documents, the system flow diagrams, surveillance testing and maintenance evolutions. The scenarios reviewed bound those conditions during emergency and normal system operations, maintenance and testing with the exception of system hydros which would be governed by PORC approved special test procedures.
These procedures typically include controls for returning equipment back to service.
Each valve evaluated was categorized under hydraulic locking, boiler effect or thermal binding, as Not Susceptible, Non-Priority Susceptible or Priority Susceptible. The difference between Non-Priority and Priority Susceptible is whether the valve has a safety function to open. As stated during the NRC sponsored workshop on GL 95-07 held at Region 4, valves witnout an active safety function to open are not considered part of the scope of GL 95-07, l
i i
i i
I I
e I
2
).
NRC Gen:ric Lettir 95-07180 Day R:sp:nse
3.0 REFERENCES
1.
NRC Generic Letter 95-07, Pressure Locking and Thermal Binding of Safety-Related Power-Operated Gate Valves 2.
NUREG 1275 Volume 9, Operating Experience Feedback Report - Pressure Locking and Thermal Binding of Gate Valves 3.
INPO SOER 84-7 dated December 14,1984.
4.
IE Circular 77-05 dated March 29,1977.
5.
AEOD/S92-07, "Special Study, Pressure Locking and Thermal Binding of Gate Valves,".
6.
W3 SES NRC Generic Letter 95-07 Screening Document.
i A
J 1
3
NRC Ccniric Lett:r 95-07180 DIy R:sp:nse 4.0 THERMAL BINDING & BONNET PRESSURIZATION EVALUATION CRITERIA 4.1 Thermal Binding Evaluation Criteria Piping Thermal Expansion Loads are generally not significant and in fact are not discussed as a failure mechanism in SOER 84-7, AEOD/S92-07, NUREG 1275 Vol. 9 or GL95-07. In addition, no documented industry gate valve failures presented in Information Notice 92-26, SER 20-84, SER 77-83 and i
SER 8-88 have been attributed to this failure mechanism. Therefore, review of Waterford 3 gate valves for piping thermal expansion loads is not necessary.
Valve Thermal Expansion Loads (Stem Elongation) may create an excessive closing force which can contribute to thermal binding. This closing force will tend to drive the disc more tightly into the seat and on cooling, the Thermal Contraction Load (Body Contraction) effects may be increased.
These phenomena were evaluated concurrently using the criteria defined below.
A.
System Temperature: Valves located in systems with operating temperatures of 200'F or less are not considered to be susceptible to thermal binding. The dividing point between a hot and cold system has been selected as 200*F based upon past evaluations of thermal binding for Limerick, Perry, Susquehanna and Grand Gulf nuclear power stations.
INPO confirmed the acceptability of the 200*F dividing line during the Susquehanna evaluation (gal /PP&L Study ME-277 Rev. 0). The line temperatures used for this evaluation were the maximum service condition values specified in the Valve and Line List, Operations Procedures or the System Temperatuie Histograms in Ebasco Nuclear Safety Ulass 1 Piping Specification.
B.
Disc Configuration: Double-disc type gate valves are not susceptible to thermal binding. The wedging mechanism between the discs collapses as the stem rises allowing the discs to move inward away from the seats.
This allows the discs to be raised regardless of system temperatures.
C.
Potential for Movement: Valves that have power removed or are in some other way disabled or locked in position were also considered for thermal binding since they may be expected to functionally change positions post-accident, for normal system operations and during plant maintenance and testing evolutions. Normal valve position was determined through the use of the P&lD's and operation procedures.
D.
Valve Function: Thermal binding occurs when valves are closed hot and allowed to cool before re-opening.
Plant procedures, system design criteria and system operating instructions were reviewed to determine valve functions and system operating modes. Valves without an active safety function to open do not affect the design basis plant safe shutdown if they are bound shut, and are outside the scope of GL 95-07.
4 4
i
- ~
NRC G:neric Lcttir 95-07180 DIy Rssp2nse 4.3 Hydraulic Lc a Evaluation Criteria A.
Disc Configuration: Solid-wedge gate valves were not considered for hydraulic locking. It is not possible for the faces of a solid wedge to be pu::hed in opposite directions against both seating surfaces.
B.
Bonnet Relief: Valves with a bonnet drain, a bonnet relief valve or a small hole through the upstream side of the valve bridge or valve disc are not considered for hydraulic locking. Any pressure that leaks into the bonnet area has an escape path that prevents hydraulic locking. If a bonnet drain is provided, it must be connected to an open piping path (drain piping installed and any in-line valves are open) to be considered not susceptible to hydraulic locking. The existence of open bonnet drain paths were determined by use of P&lD's, valve drawings or discussions with system engineers.
C.
Potential for Movement: Valves with power removed or which are in some other way disabled or locked in position were also considered for hydraulic locking since they may be expected to functionally change positions post-accident, for normal system operations and during plant maintenance and testing evolutions. They were evaluated for potential I
damage during valve stroking. Normal valve position was determined through the use of P&lD's and operation procedures.
D.
Valve Function: Hydraulic locking can occur when a closed flex-wedge or double-disc gate valve is required to open after a differential pressure condition has allowed higher pressure fluid into the bonnet cavity. Plant procedures and system design criteria were reviewed to determine valve i
functions. Valves that do not have an active safety function to open do not affect the design basis plant safe shutdown if they are bound shut, and are outside the scope of GL 95-07.
E.
Line Pressure: If the pressure in the piping upstream or downstream of i
the valve is greater than or equal to the pressure in the valve bonnet (valve bonnet pressure resulting from preceding system conditions) prior l
to opening the valve, it was not considered for pressure locking. The i
reason for this is that the line pressure will offset the pressure trapped between the faces of the disc resulting in a maximum differential pressure 7
across one face of the disc. The upstream piping pressure at opening was determined by using the plant operating procedures.
i 5
l i
1 NRC Gen:ric Lett:r 96-07180 Day R:sponse 4.4 Boiler Effect Evaluation Criteria.
A.
Disc Configuration: Solid-wedge gate valves are not considered for boiler effect. It is not possible for the faces of a solid wedge to be pushed in opposite directions against both seating surfaces.
B.
Gas Systems: Valves which are part of gas systems were not considered for liquid entrapment (Boiler Effect) if their valve stems were oriented above the horizontal. It is highly unlikely that the valve bonnet would contain liquid with these orientations. Without the bonnet containing a significant amount of liquid, it is not possible to buildup the high bonnet-pressures that would arise from heating an incompressible fluid.
C.
Bonnet Relief: Valves with a bonnet drain, a bonnet relief valve or a small hole through the upstream side of the valve bridge or valve disc were not considered for boiler effect since any water that leaks into the bonnet area will have an escape path that will prevent any pressure buildup. If a bonnet drain is provided, it must be connected to an cpen piping path (drain piping installed and any in-line valves are open) to be considered not susceptible to boiler effect. The existence of an open bonnet drain path was determined by use of the P&lD's, valve drawings or discussions with system engineers.
D.
Potential for Movement: Valves with power removed or which are in some other way disabled or locked in position were also considered for boiler effect since they may be expected to functionally change positions post--
accident, for normal system operations and during plant maintenance and testing evolutions. Normal valve position was determined through the use of P&lD's and operation procedures.
l E.
Valve Function: Boiler effect occurs when a fluid-filled or partially filled bonnet is heated. The resulting pressure may prevent the valve from reopening.
Procedures, system design criteria and system operating j
instructions were reviewed to determine valve functions. Valves without an active safety function to open do not affect the design basis plant safe j
shutdown if they are bound shut, and are outside the scope of GL 95-07.
F.
Valve Heat-up: Valves which have water in their bonnets can experience the boiler effect phenomenon only when the trapped water is heated. For this criteria to apply, the valve must be in the closed position when the i
heat source is applied.-
The following potential heat sources were considered for this evaluation.
l 6
l
NRC Gcntric LettIr 95-07130 DIy R:spsnsa The temperature increase may' be a result of close proximity to another i
heat source, such as, heat conduction through the piping from a hot adjacent branch line. In addition, the surrounding air temperature can increase due to plant events such as a LOCA. This will heat the bonnet liquid and could cause locking.
Additionally, if a gas or steam system valve is installed with the stem orientation either horizontal or below the horizontal, liquid could collect in the valve bonnet. If a valve in this configuration has a bonnet completely filled with liquid while closed and experiences a temperature increase, the resultant pressurization could prevent the valve from re-opening.
Normal ambient conditions: Normal ambient conditions are typically not expected to cause bonnet pressurization since the normal ambient temperature swings are small enough and gradual enough not to cause binding. There are not any building areas where the maximum normal ambient temperatures are excessive and may cause boiler effect binding.
Accident ambient conditions: These conditions could potentially impact the fluid if they elevate the area temperature to a point more than a couple of degrees above the normal area temperatures for a significant period of time (several hours) while the valve is closed.
Fluid Temperatures: If the closed valve is located in a branch of a hot -
system, there is the potential that the heat will conduct through the fluid or the piping.
The piping temperature histograms provide the thermal gradient that bound the temperatures utilized in the evaluations.
i I
L l'
t i
7 i
~
NRC Ccntric Lett:r 95-07180 Dry RIsp2nse 5.0 EVALUATION RESULTS The hydraulic locking screer.ing indicates that there are eight (8) Priority Susceptible valves, e
six (6) Non-Priority Susceptible valves and thirty-four (34) Not Susceptible valves.
The screening for boiler effect indicates that there are no Priority Susceptible valves, e
four (4) Non-Priority Susceptible valves and forty-four (44) Not Susceptible valves.
e The screening for thermal binding indicates that there are no Priority Susceptible valves, e
ten (10) Non-Priority Susceptible valves and e
thirty-eight (38) Not Susceptible valves.
The following table contains a listing of the Priority and Non-Priority Susceptible valves. Blank spaces indicate that the valve is Not Susceptible to the associated phenomenon.
Valve UNID Hydraulic Locking Boiler Effect Thermal Binding BD-102A Non-Priority Non-Priority BD-102B Non-Priority Non-Priority BD-103A Non-Priority Non-Priority BD-103B Non-Priority Non-Priority FW-184A Non-Priority FW-184B Non-Priority SI-120A Non-Priority SI-120B Non-Priority SI-121 A Non-Priority SI-121 B Non-Priority SI-125A Priority SI-125B Priority SI-135A Non-Priority Non-Priority SI-135B Non-Priority Non-Priority SI-219A Non-Priority SI-219B Non-Priority Si-331 A Priority SI-3318 Priority SI-332A Priority SI-332B Priority SI-412A Priority SI-412B Priority 8
d NRC Generic LettJr 95-07180 Day Rispense The valves that are Non-Priority are outside the scope of GL 95-07, and these
' valves require no further evaluation within the scope of this generic letter.
Valves ~ SI-331 A(B), SI-332A(B), Sl-125A(B) and SI-412A(B) are Priority Susceptible to hydraulic locking. SI-331 A(B) and SI-332A(B) are Safety injection Tank (SIT) discharge isolation valves and are susceptible to hydraulic locking j
only during a Loss of Cooling Accident while in Mode 4. Although unlikely, this i
scenario can occur during both heat up and cool down. These valves are j
normally open during Modes 1, 2 and 3 with power removed and are closed in l
Mode 4 at an RCS pressure no greater than 377 psig. The SIT pressure in l
Mode 4 is maintained between 235 and 300 psig (plus elevation head). In the event of a rapid depressurization of the RCS, while in this configuration, the i
valves would receive an Safety Injection Actuation Signal (SIAS) to open. The rapid depressurization could cause 377 psig to be trapped in the valve bonnet with the highest upstream pressure being no greater than 326 psig in the SITS.
j SI-125A(B) and SI-412A(B) are the Shutdown Cooling heat exchanger isolation i
valves. These valves are susceptible to hydraulic locking following surveillance testing of the Low Pressure Safety injection and Containment Spray pumps.
i Operability of all Priority Susceptible valves was demonstrated by Engineering Calculation EC-M95-011, which uses the Entergy hub" method. The calculation shows that all eight vulves are capable of overcoming the increased unseating thrust associated.with hydraulic locking.
This calculation uses a sliding coefficient of friction for stellite on stellite of 0.40. The calculated additional thrust due to the hydraulic locking condition is added to the 'As Left" static unseating thrust. The resulting total required thrust is compared to the maximum allowable thrust which is the lower of either the valve limiting component thrust or the actuator capability at reduced voltage. For conservatism, this calculation does not use piston effect to reduce the total required thrust.
The results indicate that all Priority Susceptible valves are capable of opening against calculated hydraulic locking loads. Therefore, there is no operability concern.
9
NRC G:n:ric Lett:r 95-07180 DIy R:sp:nse 6.0 WATERFORD 3 ACTION PLAN The A-train Shutdown Cooling Heat Exchanger inlet isolation valve, Sl-125A, will be modified by using the existing abandoned packing leak-off line, which currently provides constant fluid communication with the valve bonnet, as a j
bypass line to the upstream piping. The B-train Shutdown Cooling Heat Exchanger intet isolation valve, SI-125B, has an operable packing leak-off line j
which will be eliminated and used as a bypass line. This valve will be repacked to allow constant fluid communication between the bonnet and leak-off line. This i
work will be completed by the end of the Refuel 8 outage currently scheduled for the spring of 1997.
The remaining six Priority Susceptible valves will not be modified based on the results of Engineering Calculation EC-M95-011. This calculation shows that all
~
eight Priority Susceptible valves have sufficient margin and are capable of overcoming the increased unseating thrust associated with hydraulic locking. In addition, none of the valves are included in Waterford 3 Probabilistic Safety Analysis model, as determined from calculation EC-S93-008, because these valves do not affect events which contribute to core damage frequency.
Waterford 3 reserves the right to alter these plans. In the event additional information becomes available to the industry, Waterford 3 will re-evaluate the long term operability of its valves and the need to make modifications.
In addition, tuture operational procedure changes that would eliminate the conditions that lead to pressure locking may eliminate the need for any valve modifications.
10
i NRC C2neric L;tt:r 95-07180 D:y R:sp:ns2 APPENDIX 1 GL 95-07 Gate Valve Listing Valve UNID Operator Gate Type Description BAM-113A,B Motor Solid Wedge Boric Acid Gravity Feed BAM-133 Motor Solid Wedge Emergency Boration-BD-102A,B Air Flexwedge Steam Generator Blowdown inside Containment isolation BD-103A,B Air Flexwedge Steam Generator Blowdown Outside Containment isolation
_CS-125A,B Air Sluice Containment Spray Header Isolation CVC-183 Motor Solid Wedge Volume Control Tank Outlet isolation CVC-507 Motor Solid Wedge RWSP to Charging Pumps Suction Isolation FW-184A,B Hydraulic Double Disc Feedwater Isolation MS-124A,B Hydraulic Double Disc Main Steam isolation MS-401A,8 Motor Flexwedge EFW Pump AB Turbine Steam Supply SI-120A,B Motor Flexwedge SI Recirculating Header to RWSP Upstream Isolation SI-121 A,8 Motor Flexwedge SI Recirculating Header to RWSP Downstream Isolation SI-125A,B Motor Flexwedge Shutdown Cooling Heat Exchanger inlet SI-135A,B Motor Flexwedge Shutdown Cooling Warm-up SI-219A,B Motor Flexwedge HPSI Discharge Header Orifice Bypass St-301 Air Double Disc Hot Leg injection Leakage Drain SI-302 Air Double Disc Hot Leg injection Leakage Drain SI-303A,8 Air Double Disc Safety injection Tank 1 A,B Leakage Drain SI-304A,B Air Double Disc Safety Injection Tank 2A,B Leakage Drain St-331 A,8 Motor Flexwedge Safety injection Tank 1 A,B Outlet isolation SI-332A,B Motor Flexwedge Safety injection Tank 2A,B Outlet Isolation SI-343 Air Double Disc Safety injection Tank Drain Header to RWSP lsolation SI-401 A,B Motor Flexwedge Shutdown Cooling Upstream Suction isolation SI-405A,B Hydraulic Flexwedge Shutdown Cooling Suction inside Containment Isolation SI-407A,8 Motor Flexwedge Shutdown Cooling Suction Outside Containment isolation SI-412A,B Motor Flexwedge Shutdown Cooling Heat Exchanger Outlet Isolation SI-502A,8 Motor Solid Wedge Hot Leg injection isolation 1
-