ML20077D700

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Proposed Tech Specs Change 91-04,revising Steam Generator lo-lo Trip Setpoints Allowed by Upcoming Installation of Modified Steam Generator Level Transmitters
ML20077D700
Person / Time
Site: Sequoyah Tennessee Valley Authority icon.png
Issue date: 05/24/1991
From:
TENNESSEE VALLEY AUTHORITY
To:
Shared Package
ML20077D699 List:
References
NUDOCS 9105310128
Download: ML20077D700 (8)
v • d • e


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ENCLOSURE 1 PROPOSED TECilNICAL SPECIFICATION CHANGE SEQUOYAll NUCLEAR PLANT UNIT 1 DOCKET NO. 50-327 (TVh-SQN-TS-91-04)

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TABLE 3.3-4 (Continued)

N ENGINEERED SAFETY FEATURE ACTUATION SYSTEM INSTRUMENTATION TRIP SETPOINTS 8

i M E FUNCTIONAL UNIT TRIP SETPOINT Att0VABLE VALUES

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I g fi. RCS Loop AT Equivalent to

  • l l Power > 50% RTP

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Coincident with (5.0 I4M Steam Generator Water 1 %#E 4 of narrow range 144-4% of narrow range tevel - Low-Low (Adverse) instrument span instrursent span R145 and A-- ^ ~ /

l Containment Pressure (EAM) $ 0.5 psig < 0.6 psig i G.'7 l

Steam Generator Water > H-9% of narrow range 144L-4% of narrow range f level -- Low-low (EAH) instrument span instromant span d w n f A > d D d. S.I. See 1 above (all SI Setpoints)

e. Station Blackout 0 volts with a 5.0 second 0 volts with a 5.0 1.0 second a time delay time delay
f. Trip of Main feedwater N.A. N.A.

Pu:ps

g. Auxiliary Feedwater Suction 1 2 psig (rnotor driven punp) 1 I psig (trotor driven ptrp)

, Pressure-Low 113.9 psig (turbine driven 1 12 psig (turbine driven g EC pump) pump) a d k<

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h. Auxiliary Feedwater Suction Transfer Time Delays 4 seconds (motor driven puep) 4 seconds t 0.4 seconds (motor driven pump)

C 5.5 seconds (turbine driven 5.5 seconds i 0.55 secends 6 g; ptsp) (turbine driven pump)

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ENCLOSURE 2 PROPOSED TEClISICAL SPECIFICATION CllAfiGE SEQUOYAll NUCLEAR PLANT UNIT 1 DOCKET No. 50-327 (TVA-SQN-TS-91-04)

DESCRIPTION A'iD JUSTIFICATION FOR REVISION TO STEAM GENERATOR LO-LO LEVEL TRIP SETPOINY 4

E5 CLOSURE 2 Qescription_of Change TVA proposes to modif y the Sequoyah Nuclear Plant (SQN) Unit I technical specifications (TSs) to revise the steam generator wate. level trip setpoints (Table 2.2-1, Reactor Trip System Instrumaatation Trip Setpoints, Items 13.a and b, and Table 3.3-4, Engineered Safety Feature Actuation System Trip setpoints, item 6.c) to account for the installation of modified International Telephone and Telegraph Corporation (ITT) Barton Model 764 steam generator level transn:itters for Unit 1 only. This change to the TS was previously implemented for SQN Unit 2 by NRC Amendment 132.

Reason for Change The revised trip setpoints and allowable values reflect the improved accuracy of the modified Barton steam generator level transmitters being installed in Unit 1 during the upcoming Unit i Cycle 5 refueling outage.

The modification to these transmitters is performed by the manufacturer and eliminates errors associated with thermal nonrepeatability (environmental heatup and subsequent cooling) of the transmitter. The present steam generator setpoints in the TS are for unmodified Barton transmitters. This change will also make the Unit 1 TS agree with the Unit 2 TS.

Justification for Change The original setpoints in the Westinghouse Electric Corporation Setpoint Methodology. WCAP-11239 (transmitted to NRC by letter dated April 23, 1990, "Sequoyah Nuclear Plant (SQN} - Eagle 21 Setpoint Methodolexy Westinghouse Electric Corporation WCAPs 11239 and 11626"), provided values for both unmodified and modified Barton level transmitters to accommodate the installed steam generator level transmitters and to provide values for ,

the modified Earton transmitters TVA planned to install when available.

As documented in the letter from Westinghouse, TVA 00-792 dated May 13, .

I 1990, adjustments to steam generator level setpoints (adverse) for reference leg heatup were issued for unmodified Barton transmitters.

TVA's letter to Westinghouse, Letter No. NB212, dated June 27, 1990, and Westinghouse letter to TVA, TVA-90-1071, dated October 12, 1990, documented the applicability of this correction to the modified Barton Model 764 steam generator transmitters, and because of the increased accuracy over Barton 764 unmodified level transmitters, supports the icwer setpoints for environmental allowance modifier (EAM) and adverse steam generator lo-lo level.

The installation of the modified steam generator level transmitter is being performed for Unit I during the upcoming Cycle 5 refueling outage.

With the modified Earton level transmitters, the revised setpoints in this revision will still meet the requirements assumed in the SQN safety analysis. The lower setpoints will also provide additional margin for steam generator lo-lo level trips, within the safety analysis, to decrease j the occurrences of challenging SQN safety systems during startup and

~

normal operation feedwater transients. When this TS cnange is  !

implemented, both units will have the same setpoints for steam generator lo-lo level trips, thus eliminating any possible confusion between the units.

ENCLOSURE 3 PROPOSED TECHNICAL SPECIFICATION Cl!ANGE SEQUOYAll NUCLEAR PLANT UNIT 1 DOCKET NO. 50-327 (TVA-SQN-IS-91-04)

DETERMINATION OF NO SIGNIFICANT HAZARDS CONSIDERATION r

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. . . ~ - - - - - - .

ENCLOSURE 3 1 Significant flazards Evaluation TVA has evaluated the proposed technical specification (TS) change and has determined that it does not tepresent a significant hazards consideration based on criteria established in 10 CFR 50.92(c). Operation of Sequoyah Nuclear Plant in accordance with the proposed amendment will nott

1. Involve a significant increa'e s in the probability or consequences of an accident previously evaluated.

The modified transmitters are the same model as the existing transmitters but have been modified to provide increased accuracy l under thermal heatup and cooldown evolutions to improve repeatability. They perform the same function in the same manner with only the accuracy being improved to ensure identification of an ,

accident condition with the revised setpoints. This will provide accident mitigation initiations at the appropriate time to limit the consequences of the event _as assumed in the safety analysis. These transmitters are'not a device that could create an accident. but instead identify conditions associated with an accident to initiate logic for accident mitigation. Therefore. the installation of the

  • modified steam generator level transmitters and revision of the steam generator lo-lo level trip setpoints will not increase the probability or consequences of an accident.

I

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

The steam generator level transmitters and associated trip setpoints are not a source for any accident. They provide actuation of mitigation logic for specific accident parameters. Therefore, this .

change cannot create any new or different kind of accident.

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

The reduction in the steam generator 1o-10 level trip setpoints is the result of the-improved accuracy of the modifled steam generator level transmitters. This improved ace,uracy allows the use of a lower setpoint and still maintains the same level of confidence of accident  ;

condition identification without reducing the existing margin of safety. This is accomplished by only reducing the instrument inaccuracy values and not the margin of safety limits to allow the ,

lower setpoints. Therefore, there is no reduction in the margin of  !

safety.

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