ML19332E505

Safety Evaluation Supporting Amends 129 & 116 to Licenses DPR-77 & DPR-79,respectively

ML19332E505
Person / Time
Site:	Sequoyah
Issue date:	11/28/1989
From:	Office of Nuclear Reactor Regulation
To:
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ML19332E504	List: ML19332E503 ML19332E505
References
NUDOCS 8912070304
Download: ML19332E505 (5)

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NUCLEAR REGULATORY COMMISSION 3

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1 SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION SUPPORTING AMENDMENT NO.129 TO FACILITf OPERATING LICENSE NO. OPR-77 AND AMENOMENT N0. tir, TO FACILITY OPERATING LICENSE NO. DPR-79 TENNESSEE VALLEY AUTHORITY l

SEQUOYAH NUCLEAR PLANT. UNITS 1 AND 2 DOCKET NOS. 50-327 AND 50-328 l

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1.0 INTRODUCTION

,y In its letter dated May 25, 1989, theTennesseeValleyAuthority(TVA)3b at proposed to modify the Sequoyah Nuclear Plant (SQN), Units 1 and 2. Tschets Stt.

Specifications (TSs). The proposed changes would revise Tables 3.3-3, W~

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" Engineered Safety Feature Actuation System Instrumentat90n", 3.3-4,

" Engineered Safety Feature Actuation System Instrumentat"on Trip Setpos and 4.3-2, " Engineered Safety Feature Actuation System Instrumentation Surveillance Requirements." The proposed changes would add requirements for the logic time delays associated with the motor-driven and turbine-driven i

auxiliary feedwater (AFW) pump automatic suction transfer. Specifically, the following changes are proposed:

(1) a " Functional Unit" 6.h is added to each of the above tables to inclues repirements for the AFW pump suction transfer time delays, (2) the current wording of Table 3.3-3, Action 21, is replaced with'a new action appropriate for the AFW pump suction transfer pressure switches and time delays, and (3) the " Action" and " Minimum Channels Operable" columns for Table 3.3-3, Item 6.g. are revised to reflect the new Action 21 described above.

In addition, the wording of Table 4.3-2, " Functional Unit," Item 6.g.

is revised to correct an inadvertent omission from a. previous license amendment.

In its letter dated December 30, 1988, the staff approved amendments to the TSs which-1 servative direction, the AFW pump suction pressure-low trip s ble value of Table 3.3-4, Item 6.g. for both units L

for the

~ lof g the time delay circuitry in the switchover logic

pump.

In the letter, the staff discussed the I

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that trees

. Suction from the condensate storage tank to the L

Emergence ter(ERCW)Systge.

Currently, them is no mention of this time delay feature in the TSs even though it is an integral part of the actuation sequence for the AFW pump switchover to the ERCW system.

The staff's interpretation of the NRC policy statement on technical specification content (as published in the February 6,1987 edition of the Federal Rocister) was that the time delay circuitry does meet the policy statement criter'a and should be included in TSs.

In its letter dated November 23, 1988 TVA committed to submit these additional TSs by June 1, 1989.

8912070304 891128 PDR ADOCK 05000327 P

PDC 7

This was acceptable to the staff.

In the interim, the staff expected TVA to maintain assurance, through periodic testing, that the time delay circuitry complies with the analytical results (4.0 seconds for the motor-driven AFW pumps and 5.5 seconds for the turbine-driven AFW pumps) contained in TVA's letter dated November 17, 1987.

The application dated May 25,1989.. fulfills TVA's commitment to propose, to be included in the TSs. the time delay values for the time delay circuitry in the switchover logic for the AFW pumps.

2.0 EVAL.UATION As described in SQN Final Safety Analysis Report (FSAR), Section 10.4.7.2

'l the AFW system supplies feedwater to the steam generators to remove primary system stored and residual core energy in the event of a loss of the main feedwater supply. The two units have separate AFW systems composed of two.

motor-driven pumps (440 gpm) and one turbine-driven pump (880 gpm).

Each s?

of the two motor-driven pumps serves two steam generators and the single $

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turbine-driven pump serves all four steam generators. The preferred sourcei of water for the AFW pumps is the two non-seismic condensate storage tanksin (CSTs). A train of ERCW is also available to each vtor-driven AFW pump. A

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l as a seismic and unlimited backup water supply. The turbine-driven AFW pump-4:,g has. both trains of ERCW available as a backup water supply.

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Assuming the worst single active failure, the AFW pump (s can be supplied indefinitely from the ERCW system. Because the ERCW i.e. Tennessee river water) is poor quality water, it is not used except in emergencies when the water in the CST is not available As explained in the submittal for TS change 87-40 dated November 17, 1987, i

TVA evaluated the pressure switch setpoints and the logic tine delays for the

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AFW pump. suction switchover in an engineering calculation entitled " Auxiliary i

Feedwater System Pressure Switch Setpoints" Lprovided in enclosure 2 of the TS

' 40 submittal). The calculation was to ensure that adequate net positive suction head (NPSH) for the AFW pumps was maintained during the pump suction transfer sequence.

TVA stated,that, forg

. actor-driven AFW pumps, the combination of a 4-second f

1 pressure switch setpoint limit of 0.0 pounds per time es1 Vandal (ama

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was shown to ensure adequate NPSH. Similarly for the squareine(fgge gage psi MR)(combination of a 5.5-second time delay turbine-dr i

1 ressure switch setpoint limit of 10.93 psig was shown timer) an{

These time delays were accepted by the NRC in the to ensure safety evaluation dated December 30, 1988 which approved TS change 87-40.

Therefore. TVA ts proposing to add the 4.0 and 5.5-second values to Table 3.3-4 l

as the trip setpoint values for the motor-driven and turbine-driven AFW pumps, respectively.

4 TVA applied a 10 percent tolerance to the trip setpoints to obtain the allowable values for Table 3.3-4 to ensure adequate NPSH for the AFW pumps. Any negative tolerance is acceptable from a safety standpoint because this would initiate suction transfer earlier. TVA stated that the positive tolerance was acceptable

' by quantifying the conservatism in the calculated available NPSH for the pumps.

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q TVA stated 'that the available NPSH for the motor-driven pumps is calculated

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assuming a meter level in the supply header that would not be reached until 7.9 seconds. Themfore, over 3 seconds of margin exists for the motor-driven AFW pump ties delay of'4.0 seconds.

Similarly, the available NPSH for the turbine-driven AFW pump was calculated by TVA assuming a water level that would not be reached until 15.8 seconds.

Therefore, over 4 seconds of margin exists L

for the turbine-driven AFW pump time delay of 5.5 seconds when accounting for the two timers in series.

The turbine-driven AFW pump has two timers because i

this pump can be switched to either of the two trains in the ERCW system:

r timer is for the transfer to one of the two trains.

one The timers operate in sequence to assure that the turbine-driven AFW pump is transferred to one of the ERCW trains.

The Sequoyah AFW system will provide the mquired flow of 440 gpa to at least two steam generators regardless of any single failure.

Based on the NRC letter dated December 30, 1988 and the NPSH calculations made by TVA, the staff concludes that the proposed changes adding the l

AFW pump suction. transfer trip setpoints to Table 3.3-4 are acceptable i

The proposed changes to Table 3.3-3 and 4.3-2 are made for completeneskykym.

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the TS requirements on the logic time dela actuation system instrumentation (ESFASI) ys. The engineered safety f$a 3.3-4 am for the ESFASI given in Table 3.3-3 and Table 4.3-2. trip setpoin

,%. g"1 Table E lists the required number of ESFASI channels and the actions to be taken 1f any are inoperable and Table 4.3-2 lists the surveillance requirements 04 these

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a channels.

TVA stated that the proposed entries in Table 3.3-3 reflect that there is one timer for each motor-driven pump and two timers for the turbine-driven The " Applicable Modes" are consistent with the suction pressure switches pump.

of Item 6.g.

The additions to Table 4.3-2 am consistent with surveillance intervals for other timers of similar quality in the TSs.

Again, modes in which the surveillance is required am consistent with Item 6.g.

The proposed changes to Tables 3.3-3 and 4.3-2, except for the proposed action statement for Tab' e 3.3-3, are consistent with the NRC Standard Technical Specifications for Westinghouse Pressurized Water Reactors (WSTS), Revision 4a.

which are applicable to Sequoyah.

in the plant and are con The proposed changes reflect the equipment The stent with the Sequoyah TS for similar equipment.

number, of channels required to be operable is the total re, the staff concludes that these changes are accep t

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TVA 1's -

Action 21 for Table 3.3-3 by an action to provide an apprep the inoperability of an AFW pump suction transfer pressure switch at logic timer.

The inoperability of just one. pressure switch or logic timer requires the licensee to enter the' proposed action statement.

Currently, the TSs require that an inoperable AFW suction transfer pressure switch be returned to operable status within 48 hours5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br /> or a plant shutdown must be initiated.

This is the current Action 20 of s

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4 Table 3.3-3.

TVA states that the inoperability of a given pressure switch or loq1c timer affects only its associated AFW pump, not the entire AFW system.

TVA concluded that the inoperability of a piece of equipment that is attendant to one AFW pump does not warrant a forced shutdown of the plant. TVA states that it is more prudent to declare the affected AFW pump inoperable and comply with the associated actions of Specification 3.7.1.2.

This type of action is consistent with Table 3.3-3, Action 25 for the main steam line isolation valves; Table 3.3-6. Action 27. for reactor _ coolant system leakage detection; and Table 3.3-6, Action 28 for the containment purge isolation system.

There is no instrumentation listed in Table 3.3-3 that uses Action 21. The,e-fore, replacing the existing Action 21 by an action statement for inoperable AFW pump suction transfer instrumentation is acceptable. The proposed action statement requires that with less than the minimum number of instrumentation channels operable, the associated AFW pump is declared inoperable and the requirements of Specification 3.7.1.2. Auxiliary Feedwater Systems, are fol-lowed. The action to be taken for Specification 3.7.1.2 when any of the three AFW pumps and associated flow paths are inoperable should apply if the instru-mentation channels for switchover is the reason that the AFW pump is inoperable.

Therefore, the staff concludes that the proposed action statement for Table 3.3-3 is acceptable, k

l The remaining proposed changes are administrative in nature.

The first two i revise the action and minimum channels operable of Table 3.3-3. Item 6.g. AFW suction pressure-low, to implement the new action statement discussed above.

The new action statement applies to this item.

The other corrects an inadver-l tent omission made in an earlier license amendment.

License amendments 29 l

(Unit 1) and 18 (Unit 2) dated May 3, 1983 incorrectly deleted " Pressure-Low" i

from the description of Item 6.g in Table 4.3-2.

The phrase " Pressure-Low" l

is in the description of Item 6.g in Tables 3.3-3 and 3.3-4.

Therefore, the staff concludes that these amiinistrative changes to Tables 3.3-3 and 4.3-2 are acceptable.

3.0 ENVIRONMENTAL CONSIDERATION

These amendments involve a change to a requirement with respect to the installa-tion or use of a facility component located within the restricted area as defined in 10 CFR Part 20 and changes to the surveillance requirements.

The staff has determined that the amendments involve no significant increase in the amounts, and no significant change in the types, of any effluents that may be released offsite, and that there is no significant increase in individual or cumulative occupational radiation exposure. The Connission has previously issued a proposed finding that these amendments involve no significant hazards consideration and there has been no public comment on such finding. Accord-ingly, the amendments meet the eligibility criteria for categorical exclusion setforthin10CFR51.22(c)(9).

Pursuant to 10 CFR 51.22(b),'no environmental L

impact statement nor environmental assessment need be prepar' d in connection e

with the issuance of these amendments.

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4.0 GQNGLU$1E The Commissidande a proposed determination that the amendment involves no i

significant hazards consideration which was published in the Federal Register (54 FR 32717) on August 9, 1989, and consulted with the State of Teiinessee, i

No public comments were received and the State of Tennessee did not have any contents.

t The staff has concluded, based on the considerations discussed above, that:

(1) there is reasonable assurance that the health and safety of the will not be endangered by operation in the proposed manner, and (2) public such activities will be conducted in compliance with the Commission's regulations, and the issuance of the amendments will not be inimical to the comion defense i

and security nor to the health and safety of the public.

Principal Contributor:

J. Donohew r

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Dated: November 28, 1989 cd

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