ML18065A496
| ML18065A496 | |
| Person / Time | |
|---|---|
| Site: | Palisades  |
| Issue date: | 02/13/1996 |
| From: | Smedley R CONSUMERS ENERGY CO. (FORMERLY CONSUMERS POWER CO.) |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| GL-95-07, GL-95-7, NUDOCS 9602210156 | |
| Download: ML18065A496 (23) | |
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lllllCHl&AN'S l'RO&RESS Palisades Nuclear Plant: 27780 Blue Star Memorial Highway, Covert, Ml 49043 February 13, 1996 U S Nuclear Regulatory Commission
. Document Control Desk Washington, DC 20555 DOCKET 50-255 - LICENSE DPR PALISADES PLANT 180 DAY RESPONSE TO GENERIC LETIER95-07 This letter provides the requested 180-day response to Generic Letter 95-07, "Pressure Locking and Thermal Binding of Safety-Related Power-Operated Gate Valves". The requested information is contained in Attachments 1 - 5. contains a description of the process used to evaluate operational configurations of safety-related power-operated gate valves for susceptibility to pressure locking and/or thermal binding. This summary includes a description of the bases or criteria for determining that valves are or are not susceptible to pressure locking or thermal binding as well as a description of the evaluation process for valves found susceptible. contains a list of Palisades power-operated gate valves and those found susceptible to pressure locking and/or thermal binding. Attachment 3 provides the corrective actions or justifications associated with each of the susceptible valves. provides a list of inputs and assumptions associated with the methodology used in evaluating pressure locking and thermal binding. Attachment 5 provides justification on how valve modifications were scheduled using the benefits of
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SUMMARY
OF COMMITMENTS This letter contains three new commitments and no revisions to existing commitments.
The new commitments are:
- 1.
The susceptibility of the PORV Block valves to possible pressure locking will be
- eliminated by modification of the valve disc or by a system operating configuration change.
- 2.
The operating procedures will be revised to reduce the temperature differential seen by the PORV Block Valves.
- 3.
The HPSI Pump Subcooling Isolation Valves will be modified by drilling a hole in the valve discs to equalize the bonnet and high side line pressure.
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Richard W Smedley Manager, Licensing CC Administrator, Region Ill, USNRC Project Manager, NRR, USNRC NRC Resident Inspector - Palisades 5 Attachments
CONSUMERS POWER COMPANY To the best of my knowledge, the contents of this 180 Pay Response to Generic Letter 95-07, are truthful and complete.
By WJ*~-s:?~--~
Richard W. Smedley Manager, Licensing 1J Sworn and subscribed to before me this M_ day of~
1995.
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Alora M. Davis, Notary Public Berrien County, Michigan (Acting in Van Buren County, Michigan)
My commission expires August 26, 1999
[SEAL]
ATTACHMENT 1 CONSUMERS POWER COMPANY PALISADES PLANT DOCKET 50-255 180 DAY RESPONSE TO GENERIC LETTER 95-07, Description of Process used to Evaluate Safety-Related Power-Operated Gate Valves.for Susceptibility to Pressure Locking and/or Thermal Binding 1 Page
A review of valves at Palisades was performed to identify power-operated gate valves susceptible to pressure locking and/or thermal binding. This review used written instructions to ensure power-operated gate valves in safety-related applications were properly identified and evaluated. The review and evaluations were documented in Engineering Analyses EA-PL TB-00 and EA-PL TB-01.
An initial screening process was used to identify the population of power-operated gate valves in safety-related applications. This initial screening identified 54 power-operated gate valves in safety-related applications.
A functionality review was then performed for each of the 54 valves. This review was used to screen valves based on function and evaluated each valve to identify those with
. a safety function to open. An additional review for valves with an inactive open safety function was performed to identify surveillance testing which could result in pressure locking and/or thermal binding. Valves that did not meet the criteria of the functionality review were excluded from further evaluation. Guidance for performing these reviews.
is found in Engineering Analysis EA-PL TB-00.
For the valves identified in the functionality review, a pressure locking and thermal binding susceptibility review was performed. This review included a review of: 1)
System Operational Sequence and Operational Parameters, 2) Plant Operational Parameters, and 3) System Layout. The product included the worst case pressures and temperatures against which the susceptible valves could open or close. The conditions that were evaluated included pressure locking as a result of rapid changes in line pressure as well as pressure locking resulting from increases in valve ambient temperatures. Any decreasing temperature change between valve closure and subsequent opening met the criteria used for identifying valves susceptible to thermal binding. In addition to identifying valves susceptible to pressure locking and/or thermal binding, this review provided corrective actions and/or justifications for valves found*
susceptible.
The plant corrective action process (Administrative Procedure 3.03) was used for valves identified as susceptible to pressure locking and/or thermal binding. Condition Report C-PAL-95-1721 was prepared, and operability justifications were performed for the valves found susceptible prior to the 90 Day Susceptibility review as required by the Generic Letter. The justifications for operability are included in Attachment 3. The justifications identified are periodically reviewed upon receipt of new industry or plant information and updated as needed. This will continue until all corrective actions are completed. Methods for operability justification included engineering analysis, testing, and reviews of surveillance testing.
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ATTACHMENT 2 CONSUMERS POWER COMPANY PALISADES PLANT DOCKET 50-255 180 DAY RESPONSE TO GENERIC LETTER 95-07 Summary Results of Pressure Locking and Thermal Binding Evaluation of Palisades Power-Operated Gate Valves
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5 Pages
Palisades GL 95-07 Scope Motor Operated Valves Air Operated Valves Total Results of Susceptibility Evaluation Valve No.
Description Valve Actuator
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M0-1042A PORV Block Valve Double Disc MOV M0-1043A PORV Block Valve Double Disc MOV M0-2140 Boric Acid Pump Feed Flex Wedge MOV Isolation M0-2160 SIRW Tank to Charging Flex Wedge MOV Pump Isolation M0-2169 Boric Acid Tank Gravity Flex Wedge MOV Feed Isolation Valve M0-2170 Boric Acid Tank Gravity Flex Wedge MOV Feed Isolation Valve CV-0521 Alternate Steam Supply to Solid Wedge AOV P-8B from Steam Generator B CV-3070 HPSI Pump P-66B Double Disc AOV Subcooling Isolation Valve CV-3071 HPSI Pump P-66A Double Disc AOV Subcooling Isolation Valve 29 25 54 Susceptibility PL& TB PL&TB PL& TB PL& TB PL&TB PL& TB TB PL&TB PL& TB
Complete Population of Palisades Safety-Related Power-Operated Gate Valves 2
Valve No.
Actuator System Description Exclusion Pressure Thermal Based on Locking Binding Function Yes/No Yes/No CV-0521 AOV FWS Alternate Steam Supply from E-508 to P-88 No No Yes M0-1042A MOV PCS PORV Block Valve No Yes Yes.
M0-1043A MOV PCS PORV Block Valve No Yes Yes CV-3055 AOV ESS Shutdown Cooling Inlet to Shutdown Yes Cooling Hx CV-3070 AOV ESS HPSI Pump P-668 Subcooling Isolation No Yes Yes
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CV-3071 AOV ESS HPSI Pump P-66A Subcooling Isolation No Yes Yes CV-3027 AOV ESS SIRW Tank T-58 Recirculation Yes CV-3031 AOV ESS SIRW Tank T-58 Outlet Isolation Yes CV-3056 AOV ESS SIRW Tank T-58 Recirculation Shutoff Yes CV-3057 AOV ESS SIRW Tank T-58 Discharge Shutoff Yes CV-0704 AOV MSS Control Valve for Slowdown Tank Discharge Yes to Condenser Discharge CV-0733 AOV CDS Hotwell Makeup Valve Yes M0-0501 MOV MSS MSIV Bypass Yes M0-0510 MOV MSS MSIV Bypass Yes CV-3212 AOV ESS Shutdown Cooling Hx E-608 Inlet Yes
Complete Population of Palisades Safety-Related Power-Operated Gate Valves 3
Valve No.
Actuator System Description Exclusion Pressure Thermal Based on Locking Binding Function Yes/No Yes/No CV-3213 AOV ESS Shutdown Cooling Hx E-608 Outlet Yes CV-3223 AOV ESS Shutdown Cooling Hx E-60A Inlet Yes CV-3224 AOV ESS Shutdown Cooling Hx E-60A Outlet Yes M0-0798 AOV FWS Auxiliary Feedwater Isolation Yes M0-3041 MOV ESS Safety Injection Tank T-82A Outlet Isolation Yes M0-3045 MOV ESS Safety Injection Tank T-828 Outlet Isolation Yes M0-3049 MOV ESS Safety Injection Tank T-82C Outlet Isolation Yes M0-3052 MOV ESS Safety Injection Tank T-820 Outlet Isolation Yes CV-3036 AOV ESS HPSI Pump P-66A to HPSI Train 2 Isolation Yes CV-3037 AOV ESS HPSI Pump P-66A to HPSI Train 1 Isolation Yes CV-3059 AOV ESS HPSI Pump P-668 to HPSI Train 1 Isolation Yes M0-0743 MOV FWS Auxiliary Feedwater Isolation Yes M0-0748 MOV FWS Auxiliary Feedwater Isolation Yes M0-0753 MOV FWS Auxiliary Feedwater Isolation Yes M0-0754 MOV FWS Auxiliary Feedwater Isolation Yes M0-0755 MOV FWS Auxiliary Feedwater Isolation Yes
Complete Population of Palisades Safety-Related Power-Operated Gate Valves 4
Valve No.
Actuator System Description Exclusion Pressure Thermal Based on Locking
. Binding Function Yes/No Yes/No M0-0759 MOV FWS.
Auxiliary F~edwater Isolation Yes M0-0760 MOV FWS Auxiliary Feedwater Isolation Yes M0-3080 MOV ESS HPSI Hot Leg Injection Mode Select Yes M0-3081 MOV ESS HPSI Hot Leg Injection Mode Select Yes M0-3189 MOV ESS LPSI Pump P-67B Inlet form SIRW Tank Yes M0-3198 MOV ESS LPSI Pump P-67A Inlet form SIRW Tank Yes CV-0939 AOV scs MZ-11 Shield Cooling Surge Tank T-62 Yes Inlet M0-2087 MOV eve VCT Outlet Isolation Yes CV-0437A AOV ESS Iodine Removal Tank T-102 Outlet Yes CV-0437B AOV ESS Iodine Removal Tank T-102 Outlet Yes CV-0438A AOV ESS Iodine Removal Tank T-102 Outlet Yes CV-0438B AOV ESS Iodine Removal Tank T-102 Outlet Yes M0-2160 MOV eve SIRW Tank to CVCS Isolation No Yes Yes M0-2169 Mov eve Boric Acid Tank Gravity Feed Isolation No Yes Yes M0-2170 MOV eve Boric Acid Tank Gravity Feed Isolation No Yes Yes M0-2140 MOV eve Boric Acid Pump Feed Isolation No Yes Yes
Complete Population of Palisades Safety-Related Power-Operated Gate Valves Valve No.
Actuator CV-3018 AOV M0-3190 MOV M0-3199 MOV M0-3015 MOV M0-3016 MOV CV-3029 AOV CV-3030 AOV System Designations:
System Description ESS HPSI Train Cross Connect Isolation ESS LPSI Pump P-678 Shutdown Cooling Inlet Isolation ESS LPSI Pump P-67 A Shutdown Cooling Inlet Isolation ESS PCS to Shutdown Cooling Isolation ESS PCS to Shutdown Cooling Isolation ESS Containment Sump Isolation ESS Containment Sump Isolation PCS Primary Coolant System ESS Engineering Safeguards System CVC Chemical and Volume Control System SCS Shield Cooling System MSS Main Steam System FWS Feedwater System CDS Condensate and Condenser System Exclusion Pressure Based on Locking Function Yes/No
- Yes Yes Yes Yes Yes Yes Yes 5
-~
Therm*a1 Binding Yes/No
1 ATTACHMENT 3 CONSUMERS POWER COMPANY PALISADES PLANT DOCKET 50-255 180 DAY RESPONSE TO GENERIC LET-TER 95-07 Corrective Actions/Justifications for Power-Operated Gates Valves Found Susceptible to Pressure Locking and/or Thermal Binding 5 Pages
"J M0-1042A, M0-1043A PORV Block Valves Susceptible to Pressure Locking and Thermal Binding:
These valves are double disc (Edwards Equiwedge) gate valves which are not a "true" parallel dquble disc design and are susceptible to both pressure locking and thermal binding. The valves remain closed during power operation but are opened to enable L TOP when cooling down or heating up the plant.
Corrective Actions/Justifications:
Pressure Locking:
Justifications: Interim operability was justified using engineering analysis to calculate the additional thrust required to overcome the effects of a worst case pressure locking condition and the result compared with the operator capability. Margin was determined to be 63% for M0-1042A and 22 % for M0-1043A. Attachment 5
. contains additional justification using PRA.
Corrective Action: Cor;rective actions to eliminate the susceptibility of the PORV Block valves to possible pressure locking will require modification of the valve disc or system operating configuration change.
Completion Schedule: 1996 Refueling Outage Thermal Binding:
Justifications: For thermal binding, the most extreme operating conditions indicate that the valves can be closed at a maximum of 643 ° F and opened at a minimum of 495 ° F. Based on engineering judgement and MOV test experience, this 148° F temperature difference is not considered large enough to cause the valves to become thermally bound. In addition, these valves have been routinely and successfully operated with no history of thermal binding. Usually the valves are closed and opened at similar temperatures. This worst case minimum temperature for opening occurs during a rapid cooldown of PCS temperature. In reality much of the heat would be retained in the Pressurizer, piping and valve body metal and would not cool down as quickly as the PCS fluid. Furthermore, the plant operators, being especially sensitive*
to pressurized thermal shock, are directed by the EOPs to open the PORV Block Valves early in an accident. With this in mind it is very
. i 2
-likely that the temperature difference would not approach 148 ° F.
The valves are considered capable of performing their function with this temperature differential however, corrective actions will be made to reduce this value.
Corrective Actions: The corrective actions include revising operating procedures to reduce the temperature differential seen by the PORV Block Valves.
Completion Schedule: 1998 R~fueling Outage eves Boric Acid Valves M0-2140, M0-2160, M0-2169, M0-2170 Susceptible to Pressure Locking and Thermal Binding These valves are flex wedge gate valves and are susceptible to both pressure locking and thermal binding.
Corrective Actions/Justifications:
Pressure Locking:
Justifications: While these valves are not subjected to rapid depressurization events that could lead to pressure locking, they were analyzed to determine their ability to open u11der pressure locking conditions. Engineering analysis was used to calculate the additional thrust required to overcome the effects of a worst case pressure locking condition (150 psi line pressure) and the results compared with the operator capability. This analysis determined the additional thrust resulting from pressure locking to be 376 lbs, and that the motor operators remained capable of overcoming this additional thrust. The resulting margins are listed below:
Valve M0-2140 M0-2160 M0-2169 M0-2170 Margin 95%
264%
46%
31%
Corrective Actions: No corrective actions planned based on the above margins. It is important to note that the additional force
3 caused by pressure locking is an extremely small fraction in relation to the pull out force and the operator's capability.
Thermal Binding:
Justifications: These valves are all heat traced (except M0-2160) and maintained in a temperature band of 145° F - 170° F.
M0-2160 can be closed at a peak temperature of 95° F and opened at a minimum temperature of 50° F. Based on engineering judgement and MOV test experience, these temperature differences are not considered large enough to cause the valves to become thermally bound.
Corrective Actions: No corrective actions planned.
CV-0521 Alternate Steam Supply from E-508 to P-88 from Steam Generator 8 Susceptible to Thermal Binding:
This valve is a solid wedge gate valve and is therefore not susceptible to pressure locking.
Thermal Binding:
Justifications: The condition identified that could cause the valve to be potentially susceptible to thermal binding occurs when the valve is closed to permit the line to be blown down with steam. The duration this valve is closed, however, is only three minutes.
Engineering evaluation determined this is not sufficient time for the valve to cool down enough to cause it to become thermally bound.
Corrective Actions: No corrective actions planned. Additionally, the valve is being retired by FC-966 as part of an auxiliary feedwater improvement project.
CV-3070, CV-3071-HPSI Pump(s) Subcooling Isolation Valves.
Susceptible to Pressure Locking and Thermal Binding:
These valves are double disc gate valves which are not a true parallel double disc design and are susceptible to both pressure locking and thermal binding.
Corrective Actions/Justification:
Pressure Locking:
4 Justifications: The condition that makes these valves susceptible to pressure locking occurs during the performance of Q0-10 "Containment Spray Check Valve Test" and during a normal plant start up when the LPSI Pumps (shutdown cooling) are secured.
The valves remain operable at this time because subsequent to Q0-10 testing (performed during cold shutdown) and securing shutdown cooling, they were successfully cycled to support Q0-05, "Valve Test Procedure (Includes Containment Isolation Valve)",
testing. Any pressure that may have been trapped in the valve bonnet would have been relieved when the valve was stroked. In addition, thermally induced pressure locking does not affect operability. This form of pressure locking could occur between the Recirculation Actuation Signal ( RAS) and the subsequent opening of these valves. However, the time between the RAS and the opening of these valves is not sufficient to heat the valve enough to produce a pressure locking condition. Attachment 5 contains additional justification using PRA.
Corrective Actions: Corrective action is to modify the valves by drilling a hole in the valve discs to equalize the bonnet and high side line pressure.
Completion Schedule: 1998 Refueling Outage Thermal Binding:
Justification: For thermal binding, these valves can be closed at a normal maximum temperature of 104 ° F and opened at a minimum of 72° F. By engineering judgement and test experience, this 32° F temperature difference is insufficient to cause the valves to become thermally bound.
Corrective Actions: No corrective actions planned.
Other Corrective~Actions Associated with GL 95-07 In addition to the specific actions required by Generic Letter 95-07, the following actions have been taken or are planned as program enhancements to address pressure locking and thermal binding:
5 Testing: Testing was performed on motor operated valve M0-3199 in an attempt to quantify the thrust requirements associated with thermal binding. This valve is a 14" solid wedge Aloyco gate valve located at the suction of one of the Low Pressure Safety Injection Pumps and has no history of thermally binding. Just prior to the 1995 refueling outage, the valve was diagnostically tested using the VOTES system and valve pullout thrust measured 6915 lbs. The valve was closed in August at a temperature of 186 ° F when the shutdown cooling system was removed from service following a refueling outage.
In November 1995 pullout was again measured when valve was reopened at a temperature of 73 ° F (ambient). Measured pullout was found to be 5248 lbs for the temperature difference of 113°,F. Even though this is a single data point, it lends credibility to the concept that low differential temperature is not a contributing factor to additional forces at disc pullout.
Administrative Procedure Changes:. Administrative Procedures 9.03, "Facility Change", and 9.04, "Specification Changes", have been revised to include an initial screening for PL TB in the design change process.
This screening would identify design changes that could possibly lead to a pressure locking or thermal binding condition and require further evaluation by the valve group for design changes found to have an impact.
Maintenance Procedure Changes: Permanent Maintenance Procedure MSE-E-21, "VOTES Diagnostic System Operating Procedure", was revised to ensure that test data is reviewed for impact on pressure locking calculations (i.e. force at disc pullout changes). Additionally, the thrust at control switch trip is administratively co.ntrolled to occur lower in the thrust window for select valves which are susceptible to pressure locking.
Training: Plant technical staff training for pressure locking and thermal binding of power-operated gate valves is scheduled for the first quarter of 1996. The purpose of this training is to heighten the awareness of the plant technical staff to the pressure locking and thermal binding phenomenon and would include a review of industry PL TB events as well as corrective action options for resolving PL TB conditions.
. i, ATTACHMENT 4 CONSUMERS POWER COMPANY PALISADES PLANT DOCKET 50-255 180 DAY RESPONSE TO GENERIC LETTER 95-07 Generic Letter 95-07 Assumptions and Inputs
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2 Pages
- '1, General Solid wedge gate*valves are assumed not to seal on both sides of the disc (both valve seat rings) simultaneously and are therefore not susceptible to pressure locking. All other gate valve designs were considered susceptible.
Temperature differences of 0 Fare used to identify valves susceptible to thermal binding. Valves identified as susceptible are evaluated and justified on a case by case basis.
Room ambient temperature changes due to seasonal environmental changes are not considered. Only environmental changes due to accident (ie: loss of HVAC, or line break) are considered for evaluation of ambient air effects.
Conditions at the temperature/pressure source (ie: reactor, SIRWT, etc.) are conservatively assumed to be the conditions at the valve.
Density for water and borated water are assumed to be constant disregarding the
- effects of temperature.
PORV Block Valves (M0-1042A and M0-1043A)
The PORV Block Valves are double disc gate valves and it is conservatively assumed that the entire inside disc surface is subjected to the bonnet pressure.
Pressure locking forces are estimated using the standard industry equation for differential pressure load and is the differential pressure between the bonnet and discs acting on the disc area.
Coefficient of friction values for the valves were conservatively assumed to be 0.45 which is based on INEL test data for stellite on stellite. The average valve factors found during this testing were 0.35 with a standard deviation of 0.06. This yields a valve factor of 0.41.
COF's were based of the results of static testing and increased by 0.03 for added -
conservatism.
Valve pullout forces were obtained from static testing and include diagnostic test errors.
Valve operator torque capability assumed pullout efficiencies, degraded voltage, and elevated temperatures.
It is assumed that there is no fluid in the valve bonnets because of system conditions and piping configuration. The valves are installed with the bonnets
upright and upstream piping is insulated and sloped such that any condensate would flow back to the pressurizer.
l It is assumed that there will be no fluid in the bonnet at the maximum opening temperature since it will be the saturation temperature of the pressurizer at which the valves are opened during normal shutdown/cooldown.
eves Valves (M0-2140, M0-2160, M0-2169, and M0-2170)
The eves valves are all flex wedge design.
Engineering analysis used to justify interim operability utilized Roark thin plate equation to calculate thrust requirements due to pressure locking.
Valve factors were conservatively assumed to be 0.5 in the open direction.
eOF's were based of the results of static testing and increased by 0.03 for added conservatism.
Valve pullout forces were obtained from static testing and include diagnostic test errors.
Valve operator torque capability assumed pullout efficiencies, degraded voltage, and elevated temperatures.
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ATTACHMENT 5 CONSUMERS POWER COMPANY PALISADES PLANT DOCKET 50-255 180 DAY RESPONSE TO GENERIC LETTER 95-07 Modification Schedule for PORV Block and HPSI Subcooling Valves 1 Page
.J The implementation schedule for modifications to the PORV Block and HPSI Subcooling valves included consideration of the risk significance for operation of these valves in their current configurations. The current schedule for implementation of modifications to the valve discs is:
- 1) PORV Block Valves 1996 Refueling Outage
- 2) HPSI Subcooling Isolation Valves 1998 Refueling Outage The conditions which could lead to pressure locking, identified in the pressure locking/thermal binding evaluation, were analyzed for relative risk significance in an attempt to establish a priority for modification implementation. Results of this analysis found no identified risk scenarios in which pressure locking would be expected to substantially change the currently analyzed risk for power operation.
The schedule for implementation of the valve modifications is based on enhanced safety during shutdown operation for valve disassembly. Attempting to modify the HPSI Subcooling valves during the 1996 refueling outage would require the use of a freeze seal on the shutdown cooling system. From an outage perspective, disassembly of the PORV Block valves to implement the modifications has a very low risk to shutdown safety. These valves may be worked with the primary coolant system vented and without having to implement a rigorous contingency plan as would be required for the subcooling valves. Therefore, the HPSI Subcooling valves will be disassembled and modified during the 1998 refueling outage when the reactor core is scheduled to be off-loaded.
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