ML20100F502
| ML20100F502 | |
| Person / Time | |
|---|---|
| Site: | Peach Bottom, Limerick  |
| Issue date: | 02/13/1996 |
| From: | Hunger G PECO ENERGY CO., (FORMERLY PHILADELPHIA ELECTRIC |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| GL-95-07, GL-95-7, NUDOCS 9602210366 | |
| Download: ML20100F502 (10) | |
Text
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Et;_ tion Support Deprrtm:nt G.L 95-07 PECO ENERGY
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965 Chesterbrook Bealevard Wayne, PA 19087-5691 February 13,1996 Docket Nos. 50-277 50-278 50-352 50-353 License Nos. DPR-44 DPR-56 NPF-39 NPF-85 U. S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555
SUBJECT:
Peach Bottom Atomic Power Station, Units 2 and 3 Limerick Generating Station, Units 1 and 2 180 Day Response to Generic Letter 95-07, " Pressure Locking and Thermal Binding of Safety-Related Power-Operated Gate Valves."
REFERENCE:
Letter from G. A. Hunger, Jr., (PECO Energy Company) to NRC dated October 16,1995
Dear Sir:
The NRC issued Generic Letter (GL) 95-07, " Pressure Locking and Thermal Binding of Safety-Related Power-Operated Gate Valves," on August 17,1995.
In the GL the NRC requested that addressees perform, or confirm that they previously performed, evaluations of operational configurations of safety-related, power-operated gate va!ves for susceptibility to pressure locking and thermal binding.
GL 95-07 contained both a 60 and 180 day reporting requirement. The referenced letter provided PECO Energy's 60 day response. This letter provides our 180 day response for the Peach Bottom Atomic Power Station (PBAPS) Units 2 and 3, and the Umerick Generating Station (LGS), Units 1 and
- 2. The information requested by GL 95-07 is provided in Attachments 1,2 and 3 of this submittal. The requested information, as stated in the GL, has been restated and followed by our response.
j 960221o366 96o213 PDR ADOCK 0500o277 i
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February 13,1996 Page 2 If you have any questions concerning this submittal or require additional information please contact us.
Sincerely, La G. A. Hunger, r.
Director-Ucensing Attachments 1,2,3 cc:
T. T. Martin, Administrator, USNRC, Region 1 W. L. Schmidt, Senior Resident inspector, PBAPS N. S. Perry, Senior Resident inspector, LGS i
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ATTACHMENT 1 NRC Roquested Information All addressees, includog those who have already satisfactorily addressed pressure locking and thermal bindmg for MOVs by implementing the guidance in Supplement 6 to GL 89-10 (or equivalent industry ireicds), are requested to provide a summasy description of the following:
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1.
The susceptibility evaluation of operational configurations performed in response to (or consistent with) 180-day Requested Action 1, and the further analyses performed in response to (or consistent with) 180-day l
Requested Action 2, including the bases or criteria for determining that valves are or are not susceptible to pressure locking or thermal binding.
PECO Enerov Resoonse to item 1 Death of Review PECO Energy evaluated the operational configuration of safety-related power-operated gate valves at both Peach Bottom Atomic Power Station (PBAPS) and Limerick Generating Station (LGS) to identify valves that were susceptible to pressure locking or thermal binding. All modes of plant / system operation were considered, including test configurations.
l This susceptibility evaluation consisted of a comprehensive review of system and component configurations which included information from the following sources:
Valve Assembly Drawings System Piping and instrumentation Diagrams Piping Isometric Drawings i
Updated Final Safety Analysis Report (UFSAR)
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Plant Technical Specifications
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System Operating Procedures System Surveillance Test Procedures j
GL 89-10 Design Basis dP calculations Piping Specifications Environmental Conditions Specification (including normal, LOCA, HELB, and Appendix R conditions)
ASME Section XI Inservice Testing Program documents System Process Diagrams i
System Design Baseline Documents Topical Design Baseline Documents 3
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l In addstion to the above, PECO Energy performed an experience assessment i
review of pressure locking or thermal binding industry event information. This 4
review included the following documents.
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NRC/AEOD Study AEOD/S92-07 NUREG/CP 0146 NUREG-1275, Volume 9 NRC Information Notice (IN) 95-14 J
NRC IN 95-18
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NRC IN 95-30 LGS valve maintenance history j
PBAPS valve maintenance history r
Susceptibility Cnteria j
PECO Energy eliminated solid wedge valve types from susceptibility to pressure locking or thermally-induced pressure locking. It should be i
noted that the majority of low pressure gate valves at PBAPS are of the solid wedge design. Ukewise, double-disc valve types were eliminated l
from thermal binding susceptibility. These wedge types were eliminated i
based on generally accepted industry knowledge and experience which indicate that they are not susceptible to their respective phenomena.
Wedge design types were determined by reviewing valve manufacturer's assembly drawings.
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f Thermal Bindina (TB)
PECO Energy pedormed an experience review of all documented industry TB (binding when a valve cools down after being closed at a high temperature) events. This j
review found no conclusive industry TB events involving system temperatures less than 200
- F. Most TB events Involved valves which were closed at a reactor coolant i
temperature of greater than 500* F and then failed to open
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after cooldown.
i Based on this review, PECO Energy eliminated valves from TB susceptibility consideration if they were located in a j
system with a maximum operating temperature of 200* F or less. Most valves in this category experience maximum i
system temperatures of 150 F or less.
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I All other non-double-disc g;te valves were considered potentially
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susceptible to TB provided the valves were closed hot and then required to open to perform their intended safety function. These valves were then further evaluated with some eliminated from further thermal binding susceptibility consideration if they did not l
experience a cocidown prior to opening, or when significant plant operating experience under the same or more challenging conditions venfied valve capability.
Pressure Lockina (PL) 4 l
Valves are considered potentially susceptible to PL (locking induced by system pressure transients) if their bonnet pressure is greater than both the upstream and downstream piping pressures when the valve is opened. Minor variations in pressures (e.g., pump suction source pressure variations) were not considered significant due to conservatism i
i incorporated into actuator sizing criteria.
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All non-solid wedge gate valves were considered potentially susceptible
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to PL provided the valves were required to open under those conditions l
to perform their intended safety function.
i Thermally induced Pressure Lockina (TIPL) i Thermally Induced Pressure Locking (TIPL) is defined as pressure locking induced by a temperature increase in trapped bonnet fluid due to 1) heat transferred through the t
l pipe / pipe fluid or, 2) heat transferred from the surrounding
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environment.
Non-solid wedge gate valves are considered potentially susceptible to i
l TIPL if the valves are subjected to a significant temperature increase prior to opening. This assumes that the valves are required to open under those conditions to perform their intended safety function.
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Significant temperature increases for the system include changes due to alternate system operating modes as well as any inter-system effects. Significant temperature increases for the valve environment include effects due to I
design basis LOCA, HELB, and Appendix R scenarios.
Normal ambient temperature variations and minor system fluid temperature changes due to daily / seasonal changes, l
HVAC operation, and system operation were not considered significant. The performance of LGS and PBAPS valves under these conditions has been verified through system and component surveillance testing.
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PECO Energy performed an experience review of all documented industry pressure locking events. This review j
found no conclusive pressure locking events involving TIPL due to normal ambient temperature variations nor any due to normal minor system fluid temperature changes. All of the TIPL events involved large temperature increases (100 to 200
- F) due to heat conduction through the adjoining pipe. There were no events caused by ambient 2
temperature variations of any magnitude. Based on this review, the above TIPL screening criteria is considered appropriate. Valves were eliminated from further TIPL j.
susceptibility if the valve's requirement to open was early in l
i the temperature transient. This would prevent the valve from experiencing any effect of the transient.
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i 2.
The results of the susceptibility evaluation and the further analyses referred to in 1 above, including a listing of the susceptible valves identified.
i PECO Enerav Resoonse to item 2 Susceubt,ility Evaluation Results l
t Using the above susceptibility criteria, our evaluation yielded potentially l
susceptible valves as indicated in Attachments 2 and 3 for PBAPS and LGS j
j respectively. The information contained in the Attachments includes the tag number of the valve, its primary function, the associated phenomenon (a), the current disposition for the valve, and a schedule for corrective action where appropriate. Also included for valves with scheduled corrective actions is a summary description of the basis used to determine the valve's acceptable i
status in the interim.
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3.
The corrective actions, or other dispositioning, for the valves identified as susceptible to pressure locking or thermal binding, including: (a) i equipment or procedural modifications completed and planned (including the completion schedule for such actions); and (b) Justification for any i
determination that particular safety-related power-operated gate valves
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i susceptible to pressure locking or thermal binding are acceptable as is.
PECO Enerav Resoonse to item 3 4
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in addition to the information provided in Attachments 2 and 3, PECO i
Energy initiated a process to revise appropriate design control 4
procedures requiring that changes to the plant configuration be reviewed against the pressure locking and thermal binding phenomena.
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ATTACHMENT 2 PBAPS VALVES SUSCEPTIBLE TO PRESSURE LOCKING OR THERMAL BINDING CORRECTIVE VALVE ACTION NUMBER SYSTEM FUNCTION PHENOMENON (a)
DISPOSITION SCHEDULE MD-2-10-025A RHR LPCI INJECTION PL MITIGATING MOD COMPLETE MD-2-10-025B RHR LPCI INJECTION PL,TIPL MITIGATING' MOD COMPLETE MO-2-14-012A CS CS INJECTION PL MITIGATING MOD COMPLETE MD-2-14-0128 CS CS INJECTION PL,TIPL MITIGATING MOD COMPLETE MO-2-13-021 RCIC RCIC INJECTION PL,TIPL MITIGATING MOD COMPLETE M0-2-23-019 HPCI HPCI INJECTION PL,TIPL MITIGATING MOD COMPLETE M0-3-10-025A RHR LPCI INJECTION PL MITIGATING MOD COMPLETE t
M0-3-10-025B RHR LPCI INJECTION PL,TIPL MITIGATING MOD COMPLETE M0-3-14-012A CS CS INJECTION PL MITIGATING MOD COMPLETE M0-3-14-012B CS CS INJECTION PL,TIPL MITIGATING MOD COMPLETE M0-3-13-021 RCIC RCIC INJECTION PL,TIPL MITIGATING MOD COMPLETE M0-3-23-019 HPCI HPCI INJECTION PL,TIPL MITIGATING MOD COMPLETE l
ATTACHMENT 3 LGS VALVES SUSCEPTIBLE TO PRESSURE LOCKING OR THERMAL BINDING CORRECTIVE VALVE ACTION NUMBER SYSTEM FUNCTION PHENOMEN0Nfa)
DISPOSITION SCHEDULE HV-51-lF017A,B,C,0 RHR LPCI INJECTION PL MITIGATING MOD COMPLETE (1)
HV-52-1F005 CS CS INJECTION PL,TIPL MITIGATING MOD COMPLETE (1)
HV-52-1F037 CS CS INJECTION PL MITIGATING M00 COMPLETE HV-49-1F013 RCIC RCIC INJECTION PL,TIPL MITIGATING MOD COMPLETE (1)
HV-55-lF006 HPCI HPCI INJECTION TO CS PL MITIGATING MOD COMPLETE (1)
HV-55-lF105 HPCI HPCI INJECTION TO FW PL,TIPL MITIGATING MOD COMPLETE (1)
HV-49-lF029 RCIC RCIC SUPPRESSION PL SUCT TIPL MITIGATING MOD 1R07 (2)(7)
HV-49-lF031 RCIC RCIC SUPPRESSION PL SUCT TIPL MITIGATING MOD 1R07 (2)(3)
HV-55-lF042 HPCI HPCI SUPPRESSION PL SUCT TIPL MITIGATING MOD 1R07 (2)(3)
HV-51-1F014A,B RHRSW RHRSW TO RHR HX TIPL MITIGATING MOD 1R07 (2)(6)
HV-51-IF016A,B RHR DRYWELL SPRAY OUTBOARD PL MITIGATING MOD 1R07 (2)(4)
HV-51-2F017A,B,C,D RHR LPCI INJECTION PL MITIGATING M00 COMPLETE ilV-52-2F005 CS CS INJECTION PL,TIPL MITIGATING MOD COMPLETE i
HV-52-2F037 CS CS INJECTION PL MITIGATING MOD COMPLETE HV-49-2F013 RCIC RCIC INJECTION PL,TIPL MITIGATING MOD COMPLETE HV-55-2F006 HPCI HPCI INJECTION TO CS PL MITIGATING MOD 2R04 (4)
HV-55-2F105 HPCI HPCI INJECTION TO FW PL,TIPL MITIGATING MOD 2R04 (4)(5)
HV-49-2F029 RCIC RCIC SUPPRESSION PL SUCT TIPL MITIGATING MOD 2R04 (2)(7) 1
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ATTACHMENT 3 cent.
LGS VALVES SUSCEPTIBLE TO PRESSURE I4CKING OR THERMAL BINDING CORRECTIVE VALVE ACTION NUMBER SYSTEM FUNCTION PHENOMENON (a)
DISPOSITION SCHEDULE HV-49-2F031 RCIC RCIC SUPPRESSION PL SUCT TIPL MITIGATING MOD 2R04 (2)(3)
HV-55-2F042 HPCI HPCI SUPPRESSION PL SUCT TIPL MITIGATING MOD 2R04 (2)(3)
HV-51-2F014A,8 RHRSW RHRSW TO RHR HX TIPL MITIGATING MOD 2R04 (2)(6)
HV-51-2F016A,B RHR DRYWELL SPRAY OUTBOARD PL MITIGATING MOD 2R04 (2)(4)
Notes for Attachment 3:
1R07 = Unit 1 Refueling Outage 7 (Scheduled for April 1998) 2R04 - Unit 2 Refueling Outage 4 (Scheduled for January 1997) l l
(1)
Includes valves being modified during Unit 1 Refuel Outage 6 (IR06) (Jan-Feb 1996).
(2)
Modification may not be performed if valves are determined to be not susceptible via further analysis.
(3)
Interim acceptability is based on a conservative analysis demonstrating that required leakage rate to prevent bonnet pressurization during room heat up is several orders of magnitude less than typically measured leak rates for this valve.
In addition, this valve cannot be isolated for maintenance and therefore rarely receives in-body maintenance.
(4)
Determinations for interim acceptability under PL conditions have been prepared for these valves using current industry methods with reasonable inputs and assumptions regarding system, valve, and actuator parameters. These or similar determinations have been previously reviewed by the NRC.
(5)
Interim acceptability for this valve concerning TIPL was verified by satisfactory stroking at full power and maximum expected temperature. Verification of seat leakage via qualitative upstream temperature information provides added assurance that the valve is not susceptible to locking in its current condition.
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ATTACHMENT 3 cont.
(6).
Interim acceptability is based on a conservative analysis demonstrating that required leakage rate to prevent bonnet pressurization during room heat up is several orders of magnitude less than typically measured leak rates for this type of valve.
In addition, this valve is in raw water service and is an ASME XI. IST Category B valve with no leakage requirement, and is not maintained to achieve leak tight performance.
(7)
Interim acceptability is based on a conservative analysis demonstrating that required leakage rate to prevent bonnet pressurization during room heat up is several orders of magnitude less than typically measured leak rates for this valve.
In addition, this valve is an ASME XI IST Category B valve with no leakage requirement, and is not maintained to achieve leak tight performance.
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