ML20116J935

Application for Amends to Licenses DPR-77 & DPR-79,revising TS Re Response Time Requirement for ESF FW Isolation & Request for Waiver of Compliance for LCO 3.3.2.1 Re Maintenance Activity on Main FW Regulating Valve

ML20116J935
Person / Time
Site:	Sequoyah
Issue date:	11/09/1992
From:	Joshua Wilson TENNESSEE VALLEY AUTHORITY
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
Shared Package
ML20116J937	List: ML20116J935 ML20116J947
References
NUDOCS 9211160461
Download: ML20116J935 (8)

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e Teorwee va%g AuthoMy Post omco Bcw 2000 LdA D+sy. Tentw:ssee 37379 J L Wnson Vce Presen. Seqeyan Ntclev P' ant November 9, 19s2 TS-SQN-72-15 10 CFR 50.90 U.S. Nuclear Regulatory Commission AT*IN: Document Control Desk Washington, D.C. 20555 Gentlemen:

In the Matter of ) Docket Nos. 50-327-Tennessee Valley Authority ) 50-328 SEQUOYAH NUCLEAR ptANT (SQN) - REQUEST FOR WAIVER OF COMPLIANCE FOR LIMITING CONDITION FOR OPERATION (LCO) 3.3.2.1 - EMERGENCY TECHNICAL SPECIFICATION CH/ME 92 MAINTENANCE ACTIVITY ON MAIN FEEDWATER REGULATING VALVE

Reference:

NRC letter to TVA dated October 30, 1992, " Temporary Waiver of Compliance - Sequoyah Unit 1" This letter serves to document TVA's request for, and NRC approval of, a waiver of con.pliance for Unit 1 LCO .3.3.2.1 to' support maintenance activities on the Loop 2 main 'eedwater regulating valve 1-FCV-3-48 while operating in Mode _1 at approximately 1.5 percent power. This request for waiver'is similar to the reference shown above and is required as a result of the overly conservative constraints of the current TSs.

Accompanying this waiver request is an emergency permanent license amendment request that, if granted, would preclude the potential for unit shutdown.while allowing for appropriate long-term capability to perform:

necessary feedwater valve maintenance and/or testing and to-prevent additional tnivers. IVA requested a waiver of the' feedeater ' isolation-actuation logic provision relative to the isolation response times applying to the main-feedwater regulating. valves ut.til_NRC staff approval-of the enclosed emergency TS change request.

Feedwater isolation capability intended by the technical specification (TS) will be.ensur ! during these maintenance and/or testing activities by maintaining'the associated manual isolation valve 1-3-541 (and-its associated bypass valve 1-3-545) tagged in the closed position.

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.i e a U.S. Nuclear Re6ulatory Commission Page 2 November 9, 1992 ,

Feedwater. flow will be provided through the Loop 2 bypass regulating valve 1-FCV-3-48A. TS LCO 3.3.2.1, governing Fugineered Safety Feature Actuation System Instrumentation, through Tables 3.3-3 and 3.3-5, requir-e automatic isolation within defined response times utilizing the air-operated feedwater regulating valves. Necessary maintenance and testing of valve 1-FCV-3-48 will result in the inability to ensure isolation of this valve (when opened during the activities) within_those specified times utilizing any channel or train inputs. Only-the end device, air-operated regulating valve will be affected by these activities. The feedwater isolation (WI) actuation instrumentation and logic channels, including input to other protective actions, are unaffected. <

In accordance with~10 CFR 50.90, we are enclosing a requested amendment to Licenses DPR-77 and DPR-79-io chenge the TSs of SQN Units 1 and 2.

The proposed change will add the provisico to allow isolation of the feedwater flow path associated with FWI air-operated valves to satisfy the response time requirement for FW1. The proposed TS change is-identified in Enclosure 2. The justification for the ptoposed-TS change is provided in Enclosure 3. A proposed-determination of no significant hazards consideration performed pursuant to 10 CFR 50.92 is provided in Enclosure 4. This request has been reviewed and approved by the Plant; Operations Review Committee. The detailed justification ~for the waiver of compliance is provided in Enclosure 1.

These provisions are proposed to prevent unit shutdown to perform valve maintenance when the WI safety function can be otherwise fully satisfied. NRC has approved two waivers of compliance because of this TS problem. This change will eliminate the need for future waivers to perform maintenance or-testing on these valves.- TVA requests emergency processing of thic TS change request to prevent unnecessary challenges-to-plant safety systems resulting from unit shutdown.

This change request is being reviewed by TVA's Nuclear Safety Review

' Board (NSRB) in parallel with NRC review. Any changes resulting from the NSRB review will be'provided to NRC in a timely manner.

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' NRC approval of the waiver of comp 11anca for LCO 3.3.2.1 was provided verbally to TVA by G. C. Lainus, Assistant Director, Region II Reactors at 4: 12 p.m. Eastern standard -time _ on November 9, :1992.

l TVA is. additionally evaluating the viability of incorporating more extensive NUREG-1431 TS provisions as a_long-term enhancement. .It is

! expected _that any further changes resulting from that evaluatien would be L subm(tted tv NRC following the currently scheduled May 1993 SQN-NSRB' meeting.

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U.S. Nuclear Regulatory Comnission Page 3 November 9, 1992 If you have any questions concerning this issue, please contact J. D. Smith at (615) 843-6672.

Sincerely,

5. r1A J L. Wilson _

Sworn this C to/and day ofsubscribed.de v before 1992 me s eqtt4ef Notary PubYic EY COMMISSION EX? IRES KPRit 9,1995 My Commission Expires

' Enclosures i cc (Enclosures):

Mr. D. E. LaBarge, Project Manager U.S. Nuclear Regulatory Commission One White Flint, North 11555 Rockville Pike Rockville, Maryland 20852

'Mr. Michael H. Mobley, Director (w/o Enclosure)

Division of Radiological Health 3rd Floor L L 0 Annex 401 Church Street Nashville, Tennessee 37203 NRC Resident-Inspector Sequoyah Nuclear Plant 2600 Igou Ferry Road Soddy Daisy, Tennessee 37379 Mr. B. A. Wilson, Project Chief.

U.S. Nuclear Regulatory Commiasion Region II 101 Marietta Street,.NW, Suite 2900 Atlanta, Georgia-30323 1

7 1 ENCLOSURE 1

. JUSTIFICATION FOR WAIVER OF COMPLIANCE FOR LIMITING CONDITION FOR OPERATION (LCO) 3.3.2.1 MEGEQWD Following the Unit 1 power escalation after the turbine / reactor trip on October 26, 1992, the unit operators observed indications that the Loop 2 main feedwater regulating valve 1-FCV-3-48 and its control loop were not ,

responding properly. Troubleshooting activities were-initially commenced on November 4,1992, with the reactor at approxir cely_60 percent power, when the operstor noted minor oscillations in the Loop 2 steam generator (S/G) level. Instrument Maintenu.e was dispatched to the valve and a minor adjustment was made to the volume booster. - While no ef fect was observed from this adjustment, the oscillations subsequently stopped.

On November 5 1M2, with the unit operating at approximately 100 percent power, Operations noted a decreasing water level in S/G No. 2 with feed-flow falling below steam flow. Upon noting the decreasing level, the main feedwater regulating valve on Loop 2 was placed in the manual position. Levels were eventually controlled with the main feedwater regulating valve in manual and the bypass regulating valve open in automatic. Further investigations on valve 1-FCV-3-48 have noted that air leakage at the bottom of the actuator spring case is noticeable.

Conversations with the valve manufacturer's representative have confirmed that an air leak caused by a degraded 0-ring between the shaft and bushing as the most.likely cause of the observed control problems.

S/G 1evel is currently being maintained with the main regulating valve in-(fixed position) manual with the bypass valvo controlling in automatic.

The current major concern is with the ability _of the r.it to withstand a secondary side transient, even with operator action, or further.

degradation of the existing condition. The identified condition of the valves does not affect ability to quickly close upon receipt of a feedwater isolation (FWI) signal.

The planned malatenance activities for the main regulating valve include evaluating and/or replacing the inner 0-ring (s), volume tooster, and air regulator. In addition, recalibration will- be. required along with the requisite postmaintenance response time testing. _ Provided that no unanticipatad problems occur, the estimated duration of the activity is approximately 16 hours1.851852e-4 days <br />0.00444 hours <br />2.645503e-5 weeks <br />6.088e-6 months <br />. The replacement of the inner 0-rings on valve 1-FCV-3-48 and other related valve work may affect the valve's I response time. Thus, this activity will require the valve to be declared inoperable in a mode in which it is required to be operable.

During the conduct of the maintenance activities, the associated manual isolation valve 1-3-541 and its bypass will be tagged in the closed L position. This will maintain the Loop 2 main feedwater regulating valve L in'an isolated configuration throughout the maintenance activity, satisfying the intent nf.the LCO 3.3 2.1 feedwater isolation requirements. Reactor power will be reduced to approximately 15 percent. While at this power level, the feedwater bypass valve is capable of supplying adequate feedwater flow to the S/G.

Both the feedwater isolation and bypans regulating valve will be fully functional during this maintenance activity. Note that while the current-condition is isolated to valve 1-FCV-3-48, similar future activities could' occur on other feedwater regulating or bypass valvenfthat would necessitate applying similar constrainta.

Since the manual upstream valve 1-3-541 will be closed during necessary maintenance and testing activities, TVA has determined that operating in-deviation from the LCO requirements essociated with' response time for-closure of the feedwater regulating valves (Table 3.3-5, Items 2.c, 3.c, 6:c. end 8.b) would not placa the plant in an unsafe condition. The event leading to this situation was unforeseen; continued Unit 1 operr. tion in Mode 1 would not present a safety reduction; and timeliness of such NRC action is necessary to prevent the imposition of an unnecessary plant shutdown. The altuation resulting in this request is temporary and will be corrected. However, a permanent license amendment, including generic provisions, consistent with those provided by the intent of the recently approved FUREG-1431 is being proposed to NRC to provide continuing long-term capability to conduct necessary feedwater valve maintenar, e and/or testing. Accordingly, TVA has concluded that a request for g, 67

• waiver of compliance is warranted until NRC approval of the requesteu .ergency TS change. The detailed basis for the determination that operating in deviation of the LCO requirements would not place the plant in an unsafe condition is provided as follows.

SAFSIY_ ANALYSIS The feedwater system is a TVA Class -B safety system f rom the S/Cs (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. Auxiliary feedwater capabilities will be unaffected by the subject activities. Located upstream of the isolation valve and check valve are the feedwater regulating valves (FCVs-3-35

-48, -90, and -103) and the bypass regulating valves (FCVs-3-35A, -48A,

-90A, and -103A). The regulating and bypass-valves are located in that portion of the feedwater system that is 1VA Class H, and are provided with individual manual isolation' valves immediately upstream.

The feedwater isolation signal-is part of the engineered 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 SG. The feedwater regulating valves (FCVs-3-35, -48, -90, and.-103) close in a nominal L 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 i

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9 8 seconds. The signal to initiate closure of the feedwater regulating valves is available from both Train A and B power. The Class 2 motor-operated feedwater isolation valves are designed to close within 7.5 seconds from receipt of the isolation signal. The isolation valves for S/Gs 1 and 3 are powered from Train A and S/Gs 2 and 4 are powered from Train B.- The feedwater bypass regulating valves associated with j S/cs 1 and 3 are powered from Train B, while those associated with S/Gs 2  !

and 4 are powered from Train A and are response time tested to ensure closure within the same timeframe as the main feedwater regulating v&ives.

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 solation valve when they are in s e rvice . These valves have the same design requirements as the j regulating valves and are served by 1E power. The manual isolation valve 1-3-541 is a 16-inch gate valve and is frequently used as a hold-order boundary for maintenance activities durin6 refueling outages.

Complete isolation of main'feedwater to all S/Gs occurs upon receipt of any of the following isolation signals from the reactor protection system:

a. High-high S/G 1evel in any S/G - ,

h. Safety injection signal

c. Reactor trip coincident with low-reactor coolant T,yg In addition, the valves will remain in the 'losed position if the reactor protection signals are reset; 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 volumu 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 Electr! Corporation.

3. The main feedwater pumps are tripped on a feedwater isolation signal.

The feedwater regulating valves are the primary mechanism for feedwater isointion assumed in the loss of coolant accident (LOCA) and non-LOCA analyses. Closure of the feedwater isolation valves is considered a backup mechanism for isolation in the analyses to the regulating valves in conjunction with the tripping of the main feedwater pumps.

~4-The ability to utilize the manual isolation valve to perform the-isolation function to allow maintenance on the regulating (and bypass) valves is considered acceptable. The closure of the manual valve (1-3-541) just upstream of the Loop 2 main feedwater regulating valve provides'an acceptable alternative for meeting the intent of LOO 3.3.2.1-during the waivered period. The open feedwater isolation valve and controlling bypass regulating valve will remain fully operational during this activity and their isolation time is unaf fected.

1YAJEQUESUDILWAIVER OF COMPLI4liC.E TVA requests a waiver of compliance for LCO 3.3.2.1, Iable 3.3-3, Items 1.b and 5.b regardin6 the aetomatic actuation logic for feedwater isolation function as applied to the main feedwater regulating valves as required by Table 3.3-5, Items 2.c, 3.c, 6.c and 8.b. LCO 3.3.2.1 requires the feedwater isolation function to be operable in operating modes. The planned maintenance activities will require the Loop 2 regulating valve to be declared inoperable while in the applicable modes, 4 deviating from the LCO requirement to maintain the automatic and manual isolation capability of this valve within the response times provided in Table 3.3-5.

TVA requested a waiver of the feedwater isolation actuation logic provision relative to the isolation response times applying to the main feedwater regulating valves pending staff approval of the proposed- .

emergency TS change. Feedwater isolation capability intended by the technical specification (TS) will be ensured during these activities by maintaining associated manual isolation valve 1-3-541 (and its associated bypass-line 1-3-545) in the closed position. TS LCO 3.3.2.1, governing Engineered Safety Feature Actuation System Instrumentation, through Tables 3.3-3 and 3.3-5, requires automatic. isolation within defined response times utilizing the air-operated feedwater regulating valves.

Necessary maintenance and testing of valve 1-FCV- 3-43 will result in the inability to ensure isolation of this valve (wher. opened during the

, activities) within those sper."'ied times utilizing any channel or train inputs.

Only the end device, air-operated regulating valve will be affected by q this activity. The feedwater isolation actuaticn instrumentation and i logic channels, including input to other protective actions, are unaffected. The actuation system instrumentation TS is conservatively applied to the subject situation involving the' actuation end device (regulating valve).

The requested waiver was determined to have no safety significance because the intended isolation capability of the feedwater system will be

. maintained by the closed manual isolation valve and. operable FWI and l bypass regulating valve for the duration of the subject activity.

Accordingly, the requested waiver cannot result in an: increase in the 1

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probability or' consequences of a previously evaluated accident, cannot create the possibility of a new accident, and cannot reduce the margin of ,

safety. Therefore, the action does not involve a significant hazards consideration. Similarly, the waiver does not involve an unreviewed environmental question because it does not increase any adverse ,

environmental impacts, change effluents or power levels, or result in unreviewed environmental mattere.

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