ML20116D162
| ML20116D162 | |
| Person / Time | |
|---|---|
| Site: | Sequoyah  |
| Issue date: | 10/30/1992 |
| From: | Joshua Wilson TENNESSEE VALLEY AUTHORITY |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| NUDOCS 9211050218 | |
| Download: ML20116D162 (7) | |
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u u n.uwm wq,w n ra a October 30, 1992 U.S. Nuclear Regulatory Commission ATTN Document Control Desk Washington, D.C. 20555 I
Gentlemen In the Matter of
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Docket No. 50-327 Tennesset Valley Authority
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SEQUOYAI NUCLEAR PLANT (SQN) - REQUEST FOR WAIVER OF COMPLIANCE FOR UNIT 1 LIMITING CONDITION FOR OPERATION (LCO) 3.3.2.1 This letter serves to document TVA's request for a waiver of compliance for Unit 1 LCO 3.3.2.1 to support maintenance activities on the main feedwater regulating end bypass valves'while operating in Mot-3..
TVA. requested a waiver for a. period of.06 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> of the feedwater isalation actuation login provision relative to the isolation response times' applying to the main anr1 bypasa feedwater regulating valves.
Feedwater isolation capability incended by the technical-specification (TS) will be ensured during'these activitics by maintaining the motor-operated feedwater-isolation valves in the closed and deactivated' L
'cond it ion.. TS LCO 3.3.2.1, governing Engineered Safety Feature Actuation System Instrumentation, through Tables 3.3-3 andl3.3-5, requires automatic isolation.within defined response times utilizing the~-
air-operated feedwater regulating valves. Necessary maintenance and.
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testing.of these valves will result in the inab!11ty to ensurt isolation p
of these valves-(when opened during the-activititt);within those specified times utilizing any channel lor train inputs.-
Only the end device air-operated regulating valves will be affectedf y-.
b these activities. The feedwater isolation actuation: instrumentation:and~
logic channels, including. input to other protective actions, are unaffected. Tha actuation system instrumentation-TS is conservatively applied to the subject-situation involving dhe actuation end' devices (regulating valves).. This is a -conservative application of the TS.
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U.S. Nuc' ar Regulatory Conunission Page 2 October 30, 1992 request has been reviewed and approved by the Plant Operations Review Committee. The detailed justification for the waiver of compliance is provided in the enclosure.
NRC approval of the 96-hour waiver of compliance for LCO 3.3.2.1 by S. D. Ebneter, Region II Regional Administrator, was provided verbally to TVA by B. A. Wilson at 5:40 p.m. Eastern standard time on October 29, 1992.
If you have any questions concerning this issac, please call Russell R. Thompson at (615) 843-7470.
Sincerely, t.
.$ W
.. L. Wilson Enclosure cc (Enclosure):
Mr. D. E. LaBarge, Project Manager U.S. Nuclear Regulatory Commission One White Flint., North 11555 Rockville Pike Rockville, Maryland 20852 Mr. Michact H. Mobley, Director (w/o Enclosure)
Division of Radiological Health 3rd Floor L & C Annex 401 Church Street Har,hville, Tennessee 37203 NkC Re.ident inspector Saquoyah Suct ar Plant 2600 Igou Ferry Road Soddy Daisy Tennessee 37379 Mr. B. A. Wilson, Project Chief U.S. Nuclear Regulatory Connission Region 11 101 Marietta Street, NW, Suite 2900 Atlanta, Georgia 30323
ENCLOSURE JUSTIFICATION FOR WAIVER OF COMPLIANCE FOR UNIT 1 LIMITING CONDITION FnR OPERATION (LCO) 3.3.2.1 BACKCROUND On October 26, 1992. Unit 1 experienced a turbine trip / reactor trip from a high-high steam generator level signal. The initiating event leading to the trip was attributed to the entrainment of water into the plant's service / control air system. The entrained vnter adversely impacted the performance of the No. 3 steam generator nmin feedwater regulating valve, which ultimately resulted in the unit trip. The unit was stabilized in Mode 3 with the usin feedwater isolation valves, the main feedwater regulating. valves, and the bypass feedwater regulating valves closed.- A feedwater isolation occurred as designed.
As part of the recovery efforts, various air-operated components are to be disassembled and inspected. Maintenance and_ testing will be performed as required. The disassembly and inspection of somu of the Unit i feedwater and bypass feedwater regulating valve current-to-pneumatic (1/P) converters and valve positioners are-part of this work scope.
Postmaintenance response time testing will require the bypass and regulating valves to be opened without having documented compliance with technical specification response time requirements.
These activities will require the valves to be declared inoperable in a mode'in which they are required to be operable.
Since the feedvater isolation valves will be closed and deactivated during these activities. TVA has determined that operating for a period of up to 96 hours0.00111 days <br />0.0267 hours <br />1.587302e-4 weeks <br />3.6528e-5 months <br /> in devintlon from the LCO requhements associated with response time for closure of the feedwater regulating valves (Table 3.3-5, Items 2.c. '3.c 6.c, and 8.b) would not place the ' plant in n
o unsafe condition. The event leading to this situation was unforeseent continued Unit 1 operation in Mode 3 wculd not present a safety reduction; and timeliness of such NRC' action is necessary to provent the imposition of an unnecessary plant shutdown to Mode 5, which would result in a significant delay in return to power operation. The situation resulting in this request was temporary and nonrecurring; therefore, a permanent license amendment is not being requested. Accordingly, TVA has concluded that a request for an-NRC waiver of compliance is warranted.
The basis for the'detsrmination.that operating in deviation of the LCO requirements _would not place-the plant _in an unso+e condition is providad as follows.
The planned maintenance activities for the bypass regulating valves include inspection and-potential changeout of_the-I/P converters, inspection of the volume boosters. inspec ion _of the valve positioners, and requisite postmaintenance response tim. testing..The expected duration of the activity. for each bypass valve is 181/2 hours.
The planned maintenance activities f or the noin regulating valves similarly include inspection or changeout of the I/I' converters, inspection of the solenoid valves, inspection of the valve positioners, and requisite postmaintenance response-time testing.
The expected duration of the activity for each noin regulating valve is 21 1/2 hours.
The overall approach will be to first perform the activities on the steam generator No. 3 main regulating valve and on a bypass valve in parallel.
After completion of the work on these valves, their overall condition will be evaluated to determine the need to perform maintenance activities on the renmining Unit 1 bypass and main regulating valves.
Assuming that all eight valves are included in the scope of the activities the total duration of the activities will be approxicately 96 hours0.00111 days <br />0.0267 hours <br />1.587302e-4 weeks <br />3.6528e-5 months <br />.
During the conduct of the maintensnee activities, the motor-operated feedwater isolation valves will be maintained in the closed position with power removed. This will maintain the feedwater system in an isolated configuration throughout the maintenance activity, satisfying the function of the LCO 3.3.2.1 feedwater isolation requirements.
Additionally, the feedwater/ condensate system will be configureu such that there is no significant motive force of water that must be isolated, i.e., no operating main feedwater pumps.
It is important to note that the bypass and main regulating valves will also be closed during the majority of the maintenance activity.
SAFETY ANALYSIS The feedwater system is a TVA Class B safety system f rom the steam generators (reference the Updated Final Safety Analysis Report (UFSAR)
Figure 10.4.7-2) back through the motor-operated isolation valves (FCVs-3-33. -47. -87, and -100) including the check valves (3-508
-509,
-510, and -511).
This portion of the feedwater system is an integral part of the auxiliary feedwater system.
Locat9d upstream of the isolation valve and check valve are the feedwater regulator valves (FCVs-3-35, ~48, -90, and -103) and the bypass regulating valves (FCVs-3-3bA, -48A, -90A, and -103A).
The regulating and bypasn valves are located in that portion ot the feedwater system that is TVA Clas.11.
Feedwater flow to the steam generators must be interrupted within 5.5 seconds from receipt of a feedweter isolation signal during full power operation. This isolation signal is part of the ergineered safety features actuation system and serves to limit the core energy release in the case of a steamline break, to limit the magnitude of the reactor coolant system cooldown, and to prevent or mitigate the ef fect of excessive cooldown. This isolation, accompanied by a reactor trip, is accomplished by closure of redundant valves in the piping to each steam generator.
The feedwater regulating valves (FCVs-3-35, -48, -90, and
-103) close in a nominal 6.5 seconds after receipt of a feedwater isolation signal. The feedwater isolation response time, which includes the closure time and all electronic delays of the feedwater regulating valves and bypass regulating valves (FCVs-3-35A, ~48A, -90A, and -103A),
is less than 8 seconds. The signal to initiate closure of these valves
is available from both Train A and B power.
The Class 2 motor-operated feedwater isolation valves close within 7.5 seconds from receipt of the isolation signal. The isolation valves for Steam Generators 1 and 3 are powered from Train A and Steam Generators 2 and 4 are powered from Train B.
The feedwater bypass regulating valves associated with Steam Generators 1 and 3 are powered from Train B, while those associated with Steam Generators 2 and 4 are powered from Train A.
The feedwater isolation valves are 16-inch, TVA Class B, motor-operated gate valves. The feedwater regulating valves are 16-inch air to open, spring to close, fail closed control valves.
The associated solenoid valves are connected to redundant trains of IE power.
The feedwater bypass regulating valves serve as an isolation valve when they are in cervice. These valves have the same design requirements as the regulating valves and are served by 1E power.
Complete isolation of main feedwater to all steam generators occurs upon receipt of arv of the fo..owing isolation signals from the reactor protection systemt high-high steam generator level in any steam generator a.
b.
Safety injection signal Reactor trip coincident with low reactor coolant T vg c.
a In addition, the valves will remain in the closed position if the resctor protection signals are resett however, each valve can be opened or closed manually after the reactor protection system isolation signals are reset.
The assumptions utilized in the determination of the isolation time for accident analysis purposes are:
1.
SQN is an ice condenser plant that by design reduces peak pressures in the containment, both in magnitude and duration.
2.
The unisolatable volume of the feedwater system between the regulating valves and the steam generators is no more than 104 cubic feet, which is less than the maximum volume of-150 cubic feet recommended by Westinghouse Electric Corporation.
3.
The main feedwater-pumps are tripped on a feedwater isolation signal. This. action causes the orderly shutdown of-the_ condensate-feedwater system pumps.
The ferdwater regulating valves are the Trinary mechanism for feedwater isolation' assumed in the loss of1 coolant accident (LOCA) and non-LOCA-analyses. Closure of the feedwater li.n. tion valves.is considered a backup mechanism-for isolation in the analysea to the regulating valves,-
-in conjunction with the tripping'of the nein feedwater pumps. The actual-analysis value utilized is 9 seconds for feedwater isolation via'the bypass and main feedwater regulating. valves.
e
-4 Based on the administi tive 2imits of opetation during the maintenance
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activity, the pot-dal for an accident or transient relative to those predicted in thu analyses is considered niinimal because of the cargin if -
between actual plant conditions during the tivities and those casumed in the UFSAR analyses. Thecefore, the po'
.ai for a dt-gn basis event o
daring plant operation that could potentia ';> result in a feedwater c ~N isolation r,vaal is also considered miniaa, ;or those accidents and tansients aluated in the FSAR (i.e.,
fcedline ruptures, steanutne
~r'.ures, feedwater malfunctions, LOCAs, and steam generatt tube ptures).
)
- cause the feedwc*or isolaulon valves will be claced w'th power removed, 2
J4c c iclacicn time is moot because the icolation f unction has been achii 'ed.
Also, the need for redundancy is eliminated as there is nu pcssibility
'hct the isolat'on valves will fail to isolate.
The aoility la utilize tra main feedwater isolation valves to perform the Isolution f unction to allc w maintenance on the regulating and bypass W
!1 valves is censidered acceptable.
The design features associated with e 5F isolation valves, combined with the activity configuration controls, F"Tvide an acceptable alternative te maintaining isolation capability with the regulatin and bynass valve; to meet the intent of LCO 3.3.2.1
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a during the waivered timef)
TVA REQUEST FOR WAIVER OF PLIANCE waiver of compliance for LCO
.a.2.1 Table 3.3-3.
TVA rer x
Items a
- n. a.b regarding the automatic actuation logic for feedwater isolatien manction, as applied to the main feedwater regulating and bypass regulacing valvas, as required by Table 3.3-5, Items 2.t 3.c, 6.c an? H.b.
LCO 3.3.2.1 requirea the f eedwater isolation f unct ion to be operaule in Modes 4 and above. The planned maintenance activities will reauire the reguisting valves and bypaas regulating valves *, be de:lared inoperable while in the applicable modes, deviating from the LCO requirement to maintain the automatic and manual isolation capab'lity of these valves within tne tesponse times provided in Table 3.5-5.
T7A requested a waiver for a period of 96 hours0.00111 days <br />0.0267 hours <br />1.587302e-4 weeks <br />3.6528e-5 months <br /> of the feedwater isolation actuation logic provision relative to the isolation response times applying to the main and bypass feedwater regulating va?.ss.
Feedwacer isolation capability intended by the technical specification (TJ) will be ensured during these activities by maintaining the motor-operated feedwater isolation valves in the closed and deactivated ecndition.
TS Ltd 3.1 ?.1, governing Engineered Safety Feature Actuation Sys teia Inst rumentation, through Tables 3.3-3 and 3.3-5, requires automatic isolation within defined response '?.mes utiilzing the air-operated feedwater regulating valves. Necessary maintenance and testing of these valves will result in the inability to ensure isolation of these valver (when opened during the activities) within those specified times utilizing any channel or train inputs.
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5 Only the end device air-operated regulating valves will be affected by these activities. Tne feedwater isolation actuation instrumentation and logic channela, including input to other protective actions, are unaffected. The actuation system instrumentation TS is conservatively applied to the subject situation involving the actuation end devices (regulating valves).
The requested action was determined to have no safety significance because the intended isolation of the feedwater system will be maintained by the motor-operated isolation valves for the duration of the subject activities. Accordingly, the requested waiver cannot result in an increase in the probability sr consequences of a previously evaluated 1
accident, cannot create the possibility of a new accident, and cannot
~
j reduce the margin of safety. Therefore, the action does not involve a significanc hazards consideration.
Similarly, the waiver does not involse an unreviewed ensironmental question because it does not increase any adverse environmental impacts, change effluents or power levels, or result in unreviewed environmental matters.
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