ML20116J947

Proposed Tech Specs Table 3.3-5 Re Response Time Requirement for ESF FW Isolation

ML20116J947
Person / Time
Site:	Sequoyah
Issue date:	11/09/1992
From:	TENNESSEE VALLEY AUTHORITY
To:
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ML20116J937	List: ML20116J935 ML20116J947
References
NUDOCS 9211160468
Download: ML20116J947 (10)

Text

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' ' '- ENCLOSURE 2 PROPOSED TECHNICAL SPEN!FICATION-(TS) CHANGE

- SEQUOYAll NUCLEAR P1 ANT UNITS 1 AND 2 DOCKET NOS. 50-32'/ AND 50-328 (T/A-SQN-TS-92-15 )

LIST OF AFFECTED PAGES Mail.1 3/4 3-33 4 UniL2 3/4 3-33 7

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4 TABLE 3.3-5 ' Continued) )

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TABLE NOTATION (1) Diesel generator starting and sequence loading delays included. Response time limit includes opening of valves to establish SI path and attainment .

of discharge pressure f orTentrifugal charging pumps. 51 and RHR pumps. l (2) Using air operated valve. ( App Tgggy @- >

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(37 The following valves are exceptions to the response times shown in the table and will have the values listed in seconds for the initiating siO* i nals and function indicated:

Valves: FCV-26-240, -243 -

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Resp m s, tities: 2.d. 21(8/

3.d. 22(8)/ 8) 31 3 4.d.'21(0)j 33(9) 9) >

5.d.21 24(0)/31/3f9) 6.d. I Valves: FCV-61-96, -97, -110, -122, -191, -192, -193, -194 Response times:

R21 2.d.

3.d. 3231(I0) 8)

4.d. 31 50) o mth 5.d. 34 IO) 6.d. 31(0)

Valve: FCV-70-143 Response times: 2.d. 61(0)/71I9)

~2(8) 3d[61(0)/71I9) 4!d

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Y (4) On 2/3 any Steam Generator (5) -On 2/3 in 2/4 Steam Generator L.

(6) Radiation detectors for Containment Ventilation Isolation may oe excluded l

from Response Time Testing.

(7) Diesel generator starting and sequence loading delays riot included. Offsite R59 L power available. Response time limit includes opening'~alid closing _ of valves L to establish SI path and attainment of discharge pressure -for centrifugal charging pumps.

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(8)~-Diesel generator starting-and sequence loading-delays not included. -Response-time limit includes operating time or valves.

(91 Diesel Generator starting and sequence loading delays included. Responsa; f

time limit includes operating time of valves.

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SEQUOYAL UNIT-1 3/4 3~33 - Amendment No. ~ 87// 55-May.12,'198F

9 IJNSTRUMENTATION TABLE J.3-5 (Continued)

TABLE NOTATION (1) Diesel generator starti.9e .1a 53 pence loading delays included. Response time ifmit_ includes opening of valves to establish SI path and attainment ,.

of discharge pressure for centrifugal charging pumps, SI and RHR pumns.

we n v v n (2) Using air operated valve . (Apo h ccr A) l s n _A 1

< (3) The following valves are excaotions to the response times shown in the j table and will have the val w listed in seconds for the initiating '

signals and function indicated:

Valves: FCV-26-240, -243 I9)

Response tiroes: 2.d. 21(8) 3.d. 22(0)/31 5: I. !4 6.d. 21(0)/  !)

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R8 Valves: FCV61-96. -97, -110 -122. -191, -192, -193. -194  ;

Response times ,

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3.d. 3231(O)

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'%hW 4.d. 31(8) 5.d. 34(8) 6 d. 31(0)

Valve: FCV-70-143 Response times: 2.d. 61(0)/71I9) d' 62(8) 8)f 4.d.61({N'7)({9)-

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(4) On 2/3 any Steam Generator (5) On 2/3 in 2/4 Steam Generator (6) Radiation detectors for Containment Ventilation Isolation may be excluded from Response Time Testing. .

(7) Diesel generator starting-and sequence loading delays.not included.- ^

Offsite power available. Response time limit includes opening and R4~

closing of valves-to establish SI path-and attainment-of discharge pressure for centrifugal charging pumps. .

3) Diesel generatar starting and sequence-loading delays net included.

Response time 1_imit includes operating time of valves, o

(9) Diesel generator starting and sequence ioading delays included. Response

, time limit includes operating time of valves.

=SEQUOYAH - UNIT-2 3/4 3-33 Amendment No.$/47 .

Hay .12,1987

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. The response time-requirement for a specific feedwater air-operated valve can also be satisfied when the air-operated valve is either closed with air supply (d) isolat'ed. Isolated.by a closed manual valve,.or isolated by a closed feedwater isolation valve with power removed. When using one of  :

these provisions for satisfying the air-operated' valve response. time, the

. closed or isolated coadition described above will be verified et'least once per 7 days.

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ENCLOSURE 3 -

PROPOSED TECHNICAL SPECIFICATION (TS) CHANGE . .

oEQUOYAll NUCLEAR FIANT UNITS 1 AND 2 DOCKET NOS. 50-327 AND 50-328 ,

(TVA-SQN-TS-92-15)

DESCRIPTION AND JUSTIFICAT10N FOR ,

AN ALTERNATE METi!0D FOR SATISFYING THE t.

FEEDWATER IS01ATION RESPONSE TIME ,

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DescIlptiottoLChenge

,1VA proposes to modify the Sequoyah Nuclear Plant (SQN) Units 1 and 2

. technical specifications (TSs). TS Table 3.3-5. Table Notation 2 to provide an_a1tornate method for satisfying the response time requirement for the engineered saf ety feature feedwater isolation (INI). This addition to the notation is as follows:

The response time requirement f or a specific f eedt <,ter air-operated valve can also be satisfied when the air-operated valve is either closed with air supply (s) isolated. Isolated by a closed manual valve, or isolated by a closed feedwater isolation valve with power removed. When using one of these provisions for satisfying the air-operated valve response time, the closed or isolated condition described above will be verifled at least once per 7 days.

Etasottfor_Chunge The TSn for SQN require the response time for INI to be maintained within the limits assumed in the accident analysis. Review of recent needed maintenance activities associated with the air-operated INI valves in Modes 3 and above involved a conflict with literal TS compilance while performing these activities. NRC a roved two valvers of compliance to allow the implementation of these maintenance activities based on etternate isolation capability. These waiverr, were required because the ptesent TS wording does not provide alternate means for satisfying the INI response time even when isolation of feedwater flow is provided in the affected flow path. The current TS is overly conservativet this was recogniecd as such and resolved through similar provisions in NUREG-1431. The proposed change will allow future maintenance of the air-operated INI valves when adequate isolation of feedwater flow is provided. This will eliminate the need for future waivers from NRC associated with performing INI_ valve maintenance or unit shutdown to perform the maintenance activity. Unit shutdown could present unnecessary challenges to safety systems when the maintenance can be pe-formed at power without adverse impact to necicar safety.

Jus t1Lkstion_for_ Change The feedwater system is a TVA Class 11 safety system f rom the steam generators (S/Gs) (reference the Updated Final Safety Analysis Report (UFSAR) Figure 10.4.7-2) back through the motor-operated isolation valves (FCVs-3-33, 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. Located upstream of the isolation valve and check valve are the feedwater regulating valves

'l (TCVs-3-35. -48, -90, and -103) and the bypass reculating valves (FCVa-3-35A, -48A, -90A, and -103A).- The regulating and hypass valves are located in that portion of . the icedwater system that is IVA Class 11 and are provided with individual manual-1 solation 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 L of a steamline break, to limit the magnitude of the r: actor coolant system cooldown, and to prevent or mitigate the effe i of excessive cooldown. This isolation, accompanied by a reactor trip, is accomplished

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f by closure of redundant valves in the piping to each S/G. The feedwater regulating valves (FCVs-3-35. -48, -90, and -103) close in a nominal 6.5 seconds after receipt of a feedvater isolation signal. The feedwater isolation response time, which includes the closure time and all ciectronic 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 valve: 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 I and 3 are powered from Train A and S/Gs 2 and 4 are powered from Train B. The feedwater bypass regulating valves ascociated with S/Os 1 and 3 are powered from Train B, while those associated with S/Gs 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, fall-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 service. These valves have the same design requirements as the regulating valves and are served by '1B powe*. The manual isolation -

valves associated with the feedwater regulating valves are 16-inch gate  ;

valves and are f requently uced as a hold-order boundary for maintenance  ;!

activities during refueling outages. Similarly, the manual isolation valves for the bypass feedwater regulating valves are 4-inch gate valves.

Complete isolation of main feedwater to all SfGs occurs upon receipt of any of the following isolation signals from_the reactor protect!on-systems

a. liigh-high S/G 1evnl- in any S/G

b. Safety injection signal

c. Reactor trip coincident with low reactor coolant T,yg in addition, the valves will remain in the closed position if the reactor protection signals are reset; however, each valve can be opened or closed manually after the reactor protection system isolu;1on signals are reset.

The assumptions utillr.ed in tha determination of the isolat.an time f or accident analysis purposes are:

1. SQN la an ice condenser plant that by design reduces peak pressures la the containment, both in magnitude and duration.

2. The unisolatable volume of the feedwater system between1the-regulating valves and the S/Gs-is no more than 104 cubic fcet, which is less than the maximum volume of 150 cubic feet recommended by a Westlighouse Electric. Corporation.

3.= The main feedwater pumpa are tripped on a feedwater isolation signal. s

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P The feedwater regulating valves are the primary mechanism for feedwater isolation assumed in the loss of coolant accident (loCA) and non-LOCA analyses. Clonure of the feedwater isolation valves is considered a backup mechanism for isolation in the anriyses to *he regulating valves, in tonjunction with the trippinB of the main feedwater pumps.

The proposed TS change will allow the isointion of the affected feedwater ' '

flow path to satisfy the response time requirement for FWI. With the flow path isolated, the safety function provided by the air-operated FWI valves is already achieved. The response time assumed in the accident analysis for FW1 is met because under these conditians the response time is zero. The TSs require a response time of less than or equal to 8 seconds for FWI o* containment pressure high, pressurizer pressure low, and stenm line pressure low conditions, and less than or equal to 11 seconds for the S/G water level high-high condit ion. _

For the alternative to close the air-operated valve and isolate the air cupply(s), the safety function is already achieved to isolate feedwater flow. Isolation of the air supply (s) ensures the valve is deactivated to prevent inadvertent operation. These valves fall close with air pressure required to overcome the spring force holding the valve in the closed position. For the use of a closed manual isolation valve, the same isolation of feedwater flow is provided that is assumed by closure of the air-operated FWI valve with no time delay. For the closed motor-operated FMI valve with power removed method, once again feedwuter flow is isolated from the main and bypass air-operated valves to the S/Gs. Both flow paths associated with the air-operated valves go through the motor-operated FWI valve. By removing power to the motor operator of this valve, inadvertent operation is prevented. The requirement to verify the provisions of each of these methods at least once every 7 days provides additional assuranc" that the safety function is adequately maintained. Therefore, thece methods implement the FWI safety function of the air-operated valves with no time-delay and meet all the assumptions utilized in the SQN accident analysis for FWI. _

Environmentallwactlyaluation The proposed change _ request does not involve an unreviewed environmental question because operation of SQN Units 1 and 2 in accordance with this change would nott 4 1. Result in a significant increase in any adverse environmental impact previously evaluated in the Final Environmental Statement (FES) as modified by the staff's testimony to the Atomic Safety and Licensing Board, supplements to the FES, environmental impact appraisals, or decisions of the Atomic Safety and Licensing Board.

2. Result in a significant change in ef finents or power levels.

3. Result in matters not previously reviewed in the licensing basis for SQN that may have a significant environmental i.npact.

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l'ROPOSED TECl!NIC.' % SPECIFICATION (TS) CilANGE SEQUOYAll NUCLEAR PLANT UNITS 1 AND 2 DOCKET NOS. 50-327 AND 50-328 (WA-SQN-TS-92-15 )

DETERMIiATION OF NO SIGNIFICANT IIAZARDS CONSIDERATION e

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Significant llazards Evaluation TVA has evaluated the proposed technical. specification (TS) change and has detennined that it does not represent a significant hazards consideration baced on criteria established in 10 CFR 50.92(c).

Operation of Sequoyah Nuclear Plant (SQN) in accordance with tne proposed amendment will not

1. Involve a significant increase in the probability or consequences of an accident previously evaluated.

The proposed TS change fully maintains the feedwater isolation (FWI) functions assumed in the accident analysis. In addition, no component functions will be af fected by utilizing the alternate methods to ensure ccmpletion of the FWI function for accident mitigation. Since maintaining the conditions to provide FWI is not postulated to create an accident, there is no increase in the probability of an accident. By maintaining icolation cf the

, feedwater flow path when tb? response time for automatic actuation of the air-operated FWI valve is considered inoperable, all safety f unctions assumed in the accident analysis for FWI are met to ~i mitigate accident conditions. Therefore, there is no increase in the consequences of an accident because the safety functions for accident mitigation are maintained by the alternato isolation methods that are more conservative than the normal time delayed valve actuation. .

2. Create the possibility of a new or different kind of accident from any previously analyzed. '

The isolation of feedwater flow is not considered the source of an accident although inadvertent isolation may initiate automatic unit  ;

shut hwn that is an analyzed event. This change will not alter any '

plant design or operating parameters such that conditions could be.

crea'ed that would create new accident potenticis. .The isolation-methods are the same as or equivalent to the closing of the air-operated valves and will not create any additional safety concern or plant operating impact. Therefore, *.he use of these methods to maintain the FWI function will not create a new or different kind of accident.

3. Involve , significant reduction in a margin of safety.

This change provides alternate FWI methods that _ are more conservative than the delayed isolation assumed in the accident analysis. By placing the flow path in an isolated condition, the safety function is already achieved without-the need for the valve actuation and the ,

associated response time. Therefore, the use of these alternate FWI methods to satisfy TS response time requirements will'actually result in an increase in the margin of safety when compared with normal plant operation.

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