ML20235A123

Proposed Tech Specs Adding Requirements for long-term Containment Cooling Following non-LOCA Event.Description & Justification for Containment Cooler Requirements Encl

ML20235A123
Person / Time
Site:	Sequoyah
Issue date:	09/16/1987
From:	TENNESSEE VALLEY AUTHORITY
To:
Shared Package
ML20235A031	List: ML20235A028 ML20235A123
References
NUDOCS 8709230215
Download: ML20235A123 (16)

Text

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.t CONTAINMENT STEMS l

-eetfTAM:NT f COOLING SYSTEMS (UT EL' (L e t ;-. f a i; din; r; rec.l by

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LowCR Cop 1hN/nf'A ff' VCp]f* COOffRS

• LIMITING' CONDITION FOR OPERATICN ,

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t 3.6.2.7 (Two[ independent f.Frak gr;up;ofcflower ce&%en+

nt:inment  :::lin;veerF coolefs f;n; shall be OPERABLE t::: to eac4 gr;;p. (E:;ur/ci:nt t: 100" :: TMH; ::;;;i t.7 '

with f,twoj!L':ndoo cy:/d/3 \ ./m;n.

APPLICABILITY: MODES 1, 2, 3 and 4. ,

~ 'I ACTION:

/ ewer C & w " I Y' O N e d

a. With one geewp-of the above required [::ntai ::nt :::1'n; ':n:

inoperable =d b;t.' ::nt:f = t :; ,

, :y;t;;; C '"LE, restore ee-in:;r:bi: grr_; f = :1'n; f n: to OPERABLE status within 7 days or be in at least HOT STANDBY within the next 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> and in COLD

. SHUTDOWN within the following 30 hours3.472222e-4 days <br />0.00833 hours <br />4.960317e-5 weeks <br />1.1415e-5 months <br />.

no fuer rowdsmed VMf Coolers of 8e same +a;n.

b. With tu: gr;;p: uf th; ;bre: r;;;; ired :;ndeir:=t =:1'; ':w inoperable, end both ::nt:f = nt :pr:y :y:t; : TE? *.S LE , res tore -e4.

1;:.n n: gr:;p :f = 1'n; f=: to OPERABLE status within 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />

. or ce in at least HOT STANDBY within the next

- 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> an.d in COLD SHUTDOWN within the following 30 hours3.472222e-4 days <br />0.00833 hours <br />4.960317e-5 weeks <br />1.1415e-5 months <br />. ' " - - - '"' xn r::;;i r:d geup: ef : =!'n; fan t 0 EE h ,4:tu: ith' ' d; : ' '- i t ::.1 -

M: -be":t ' ::t "0" !~" *S M ' " ner: EW r' COL :::L'TDC'.?" ith" the f:11:.4 ng 20 heu c. i With one group of the abo <e required containment c$oling fans ino and one containment spray system inoparable, res - a inoperaole spr . m to OPERABLE status within " m s or be in at least HOT STANDBY wit gxc6 ano in COLD SHUTDOWN within the following 30 houre 6o c a, inoperable group of containment cooli .o o OPERABLE status yi 4 d vs of initial loss o at least HOT STANDBY within the next 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> . 4 SHUTDOWN within the following 30 hours3.472222e-4 days <br />0.00833 hours <br />4.960317e-5 weeks <br />1.1415e-5 months <br />.

SURVEILLANCE REQUIREMENTS ,

b r L lowec culaiwetrt yer,} tooler

.$o@'f. 4.6.L 7 Each cro; c' :crt:i ent :=n; f=: shall be demonstrated OPER/ ELE:

o~o co on a. Atleastonceper31daysby/p

' it -ti g =cr f:r gre; ' :- th :;rt :' =: verifying thn

-u each fan r,r wa operates for at least 15 minutes.

no y g. 2 Verifying a cooling water flow rate of creater than or equal to pao ppm to each cooler. c a

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b. At least oncs per lS months by:;:

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CONTAINMENT SYSTEMS 3/4.6.2 DEPRESSURIZATION AND COOLING SYSTEMS l LOWER CONTAINMENT VENT COOLERS , _ _-

l LIMITING CONDITION FOR OPERATION f i

3.6.2.2 Two independent trains of lower containment vent coolers'shall be OPERABLE with two coolers to each train.

APPLICABILITY: MODES 1, 2, 3 and 4.

ACTION:

a. With one of the above required lower containment vent coolers inoperable, restore to OPERABLE statue within 7 days or be in at least HOT STANDBY within the next 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> and in COLD SHUTDOWN within the following 30 hours3.472222e-4 days <br />0.00833 hours <br />4.960317e-5 weeks <br />1.1415e-5 months <br />.

b. With two lower containment vent coolers of the same train inoperable, restore to OPERABLE status within 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> or be in at least HOT STANDBY within the next 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> and in COLD SHUTDOWN within the following 30 hours3.472222e-4 days <br />0.00833 hours <br />4.960317e-5 weeks <br />1.1415e-5 months <br />.

SURVEILLANCE REQUIREMENTS 4.6.2.2 Each lower containment vent cooler shall be demonstrated OPERABLE:

a. At least once per 31 days by verifying that each fan operates for at least 15 minutes.

h. At leasL once per 18 months by:

1. Verifying from the control room that each fan starts.

2. Verifying a cooling water flow rate of greater than or equal to 200 gpm to each cooler.

SEQUOYAH - UNIT 1 3/4 6-16a e

4" CONTAINMENT SYSTEMS j -[:g BASES l

3/4.6.1.8 EMERGENCY GAS TREATMENT SYSTEM (EGTS)

.  ;. 1 The OPERABILITY of the EGTS cleanup subsystem ensures that during LOCA conditions, containment vessel leakage into the annulus will be filtered

• through the HEPA filters and charcoal adsorber trains prior to discharge to '

the atmosphere. This requirement is necessary to meet the assumptions used' in the accident analyses and limit the site boundary radiation doses to within FP the limit.a of 10 CFR 100 during LOCA conditions. Cumulative operation of the system with the heaters on for 10 hours1.157407e-4 days <br />0.00278 hours <br />1.653439e-5 weeks <br />3.805e-6 months <br /> over a 31 day period is sufficient to reduce the buildup of moisture on the absorbers and HEPA filters. ANSO N510-1975 will be used as a procedural guide for surveillance testing.

3/4.6.1.9 CONTAINMENT VENTILATION SYSTEM Use of the containment purge lines is restricted to only' one pair (one supply line and one exhaust line) of purge system lines at a time to ensure that the site boundary dose guidelines of 10 CFR Part 100 would not be exceeded in the event of a loss of coolant accident during purging operations. The analysis of this accident assumed purging through the largest pair of lines (a 24 inch inlet line and a 24 inch outlet line), a pre-existing iodine spike in the reactor coolant and four second valve closure times.

( 3/4.6.2 DEPRESSURIZATION AND COOLING SYSTEMS 3/4.6.2.1 CONTAINMENT SPRAY SYSTEM The OPERABILITY of the containment spray system ensures that containment depressurization and cooling capability will be available in the event of a LOCA. The pressure reduction and resultant lower containment leakage rate are y, consistent with the assumptions used in the accident analyses.

3/Y.6. 2. L.

3/4.6.3 CONTAINMENT ISOLATION VALVES The OPERABILITY of the containment isolation valves ensures that the containment atmosphere will be isolated from the outside environment in the event of a release of radioactive material to the containment atmosphere or pressurization of the containment. Containment isolation within the time limits specified ensures that the release of radioactive material to the environment will be consistent with the assumptions used in the analyses for a  !

LOCA. By letters dated March 3, 1981, and April 2, 1981, TVA will submit a I report on the operating experience of the plant no later than startup after R8 the first re fueling. This information will be used to provide a basis to re-evaluate the adequacy of the purge and vent time limits.

SEQUOYAH - UNIT 1 B 3/4 6-3 A_m um.a . . t 5

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INSERT 3/4.6.2.2 CONTAINMENT COOLING FANS The OPERABILITY of the lower containment vent coolers ensures that.

adequate heat removal capacity is available to provide long-term cooling "

followin5 a non-LOCA event. Postaccident use of these coolers ensures containment temperatures remain within environmental qualification limits for all safety-related equipment required to remain functional.

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CONTAINMENT STEMS CCNTAIN S T COOLING SYSTEMS (C."T:CNAL; (;.mJ.; tamo fcr indin: r;;;s.1 by ~ ~

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LIMITING CONDITION FOR OPERATION 1 f-hain of lower c&me,1+ ve,1F cooleo 3.6.2.7 (Twol independent gr u;; cf ::nt:f r =t =;1i ; f=: shall be OPERABLE with (twon f= :;:t::: to eac4 ;r=p. (Equ; =l at t: 1005 :::l'n; =;::ite.)

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APPLICABILITY: MODES 1, 2, 3 and 4.

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ACTION:

/owei Cs'hlewd ved coolec.s

a. With one geewp- of the above required [::nt:f :=t :=1

• n; '=:

inoperable =d b;th = nt:f := t :;r:3 :y: t:.- : OP:P*. ELE, restore %e-

'n:;:rdl; gr=; cf :=1'n; fr: to OPERABLE status within 7 days or be in at least HOT STANDBY within-the next 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> and in COLD SHUTDOWN +,.,o tower within conMwedthe following 30 hours3.472222e-4 days <br />0.00833 hours <br />4.960317e-5 weeks <br />1.1415e-5 months <br />.

Ve# coolers o f Ae same +rtin.

b. With t= gr;i;; -f th; ob= : r:auired := t i-- ni = 1'n; ':n inoperable, end bett =nt i :=t :pr:y :y:t=: CPEP";2LE , restore -et-i=: n: gr=; cf :=1'n; f=: to OPERABLE status within 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />

. or be in at least HOT STANDBY within the next 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> and in COLD SHUTDOWN within the following 30 hours3.472222e-4 days <br />0.00833 hours <br />4.960317e-5 weeks <br />1.1415e-5 months <br />. Ec tor: b;th ;b;s: 7:quir:d group: ef :: !'n; 'rt + 0"E" ELE :t:tur .

ith' ' d:y: cf '-iti:1 -

1:= or 5: ' :t ' rrt ""' r-*""'Y 'th'- th; non ? Mu : :"d '-

COLO "UTOCU" ith'- th: f:11:;.'n; 20 Mum With one group of the above required containment cooling fans ino and one containment spray system inoperable, res " ...

inoperable spr . m to OPERABLE status within s or be in at least HOT STANDBY wit xt 6 na in COLD SHUTDOWN within the following 30 hour3.472222e-4 days <br />0.00833 hours <br />4.960317e-5 weeks <br />1.1415e-5 months <br /> o inoperable group of containment cooli #

. o OPERABLE status w1 - s of initial loss o at least HOT STANDBY within the next 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> i SHUTDOWN within the following 30 hours3.472222e-4 days <br />0.00833 hours <br />4.960317e-5 weeks <br />1.1415e-5 months <br />.

SURVEILLANCE REQUIREMENTS 1 p / ewer e,4ime/rt ved cooleC 4.6.2.7 Each t ro; c' n n ui = t : =1'n; '=: shall be demonstrated OPERAELE:

a. Atleastonceper31daysby/p St:rting :=r far grou '--- the = ntr ' = verifying that each fan psawa operates for at least 15 minutes.

g. 2 Verifying a cooling water flow rate of greater than or ecual to poo gpm to eacn cooler. g At least once per 18 conths by:. r '  ; :.nn _ .:. ':

b.  ; tu m m = =:= . -- ~-

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CONTAINMENT SYSTEMS 3/4.6.2 DEPRESSURIZATION AND COOLING SYSTEMS LOWER CONTAINMENT VENT COOLERS ,,

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LIMITING CONDITION FOR OPERATION 3.6.2.2 Two independent trains of lower containment vent coolers shall be

. OPERABLE with two coolers to each train.

APPLICABILITY: MODES 1, 2, 3 and 4.

ACTION:

a. With one of the above required lower containment vent coolers inoperable, restore to OPERABLE status within 7 days or be in at least HOT STANDBY within the next 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> and in COLD SHUTDOWN within the following 30 hours3.472222e-4 days <br />0.00833 hours <br />4.960317e-5 weeks <br />1.1415e-5 months <br />,

b. With two lower containment vent coolers of the same train inoperable, restore to OPERABLE status within 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> or be in at Isast HOT STANDEY within the next 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> and in COLD SHUTDOWN within the following 30 hours3.472222e-4 days <br />0.00833 hours <br />4.960317e-5 weeks <br />1.1415e-5 months <br />.

SURVEILLANCE REQUIREMENTS 4.6.2.2 Each lower containment vent cooler shall be demonstrated OPERABLE:

a. At least once per 31 days by verifying that each fan operates for at least 15 minutes,

b. At least once per 18 moaths by:

1. Verifying from the control room that each fan starts.

2. Verifying a cooling water flow rate of greater than or equal to 200 spm to each cooler.

SEQUOYAH - UNIT 2 3/4 6-16a

4 >

CONTAINMENT SYSTEMS BASES 3/4.6.1.8 EMERGENCY GAS TREATMENT SYSTEM (EGTS) .

The OPERABILITY of the EGTS cleanup subsystem ensures that during LOCA conditions, containment vessel leakage into the annulus will be filtered through the HEPA filters and charcoal adsorber trains prior to discharge to the atmosphere. This requirement is necessary to meet the assumptions used in the accident analyses and limit the sits boundary radiation doses to within the limits of 10 CFR 100 during LOCA conditions. Cumulative operation of the system with the heaters on for 10 hours1.157407e-4 days <br />0.00278 hours <br />1.653439e-5 weeks <br />3.805e-6 months <br /> over a 31 day period is sufficient to reduce the buildup of moisture on the absorbers and HEPA filters. ANSI N510-1975 will be used as a procedural guide for surveillance testing.

3/4.6.1.9 CONTAINMENT VENTILATION SYSTEM Use of the containment purge lines is restricted to only one pair (one supply line and one exhaust line) of purge system lines at a time to ensure that the site boundary dose guidelines of 10 CFR Part 100 would not be exceeded in the event of a loss of coolant accident during purging operations. The analysis of this accicent assumed purging through the largest pair of lines (a 24 inch inlet line and a 24 inch outlet line), a pre-existing iodine spike in

(- the reactor coolant and four second valve closure times.

3/4.6.2 DEPRESSURIZATION AND COOLING SYSTEMS 3/4.6.2.1 CONTAINMENT SPRAY SYSTEM The OPERABILITY of the containment spray system ensures that containment depressurization and cooling capability will be available in the event of a LOCA. The pressure reduction and resultant lower containment leakage rate are 7ggggg7- consistent with the~ assumptions used in the accident analyses.

3/4.6.3 CONTAINMENT ISOLATION VALVES The OPERABILITY of the containment isolation valves ensures that the containment atmosphere will be isolated from the outside environment in the event of a release of radioactive material to the containment atmosphere or pressurization of the containment.

Containment isolation within the time limits specified ensures that the release of radioactive material to the environment will be consistent with the assumptions used in the analyses fer a LOCA.

3/4.6.4 COMBUSTIBLE GAS CONTROL The OPERA 8ILITY of the equipment and systems required for the detection f and control of hydrogen gas ensures that this equipment will be available to

( maintain the hydrogen concentration within containment below its flammable limit during post-LOCA conditions. Either recemoiner unit or the purge system SEQUOYAH - UNIT 2 8 3/4 6-3

• T.

INSERT 3/4.6.2.2 CONTAINMENT COOLING FANS The OPERABILITY of the lower containment vent coolers ensures that.

adequate heat removal capacity is available to provide long-term cooling '

following a non-LOCA event. Postaccident use of these coolers ensures containment temperatures remain within environmental qualification limits for all safety-related equipment required to remain functional, i

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1 ENCLOSURE 2  !

L PROPOSED TECHNICAL SPECIFICATION CHANGE

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

(TVA-SQN-TS-87-37)

DESCRIPTION AND JUSTIFICATION FOR l CONTAINMENT COOLER REQUIREMENTS

'l

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1

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I

ENCLOSURE 2 Description of Change '

The Tennessee Valley Authority proposes to modify the Sequoyah Nuclear plant (SQN) Units 1 and 2 Technical Specifications to add additional requirements for containment cooling for non-loss of coolant accident (LOCA) events.

Revised calculations for a main steam line break (MSLB) inside containment (the most severe non-LOCA event for containment temperature) indicate that ~

temperatures would exceed environmental qualification (EQ) limits for certain equipment in the lower compartment and pressurizer enclosure. The proposed change will impose limiting conditions for operation and associated surveillance requirements for the lower containment cooling fans to ensure that temperatures following a MSLB remain below the EQ limits.

Reason for Change Current EQ temperatures inside containment are based on the reactor coolant system (RCS) conditions reaching cold shutdown. Plant cooldown to cold shutdown is accomplished postaccident by recirculation mode core cooling or by placing the residual heat removal (RHR) system into operation approximately four hours af ter reactor shutdJwn, once RCS temperature and pressure are approximately 3500 F and 380 psig, respectively. However, an MSLB inside containment creates flooding conditions at the single RCS suction line that could prevent the use of che RHR because one of the series suction isolation valves is submerged. Failure of either suction valve to open would prevant RHR system operation for plant cooldown. Without RHR capabilities, the RCS would have to be maintained in hot standby. This is the-present licensing basis for SQN. This causes additional long-term heat loads that drive lower containment and pressurizer enclosure temperatures above the EQ limits.

Postaccident use of the lower containment coolers will ensure containment temperatures remain below the current EQ curve. Technical specification requirements are being added since these coolers now have an assumed role in accident mitigation.

Justification for Change The postaccident effects of an MSLB for containment temperature environment l were evaluated using the " MONSTER" containment computer code. The containment was modeled according to standard NRC practice. The model included the upper, ,

lower, ice condenser, and dead-ended regions plus major concrete and steel <

heat sinks. The RCS was modeled as a time-dependent heat source based on infonnation from Westinghouse, and a separate region for the pressurizer was included. A supporting calculation to establish cooler performance was performed to provide a basis for the cooler model used in the MONSTER analyses. The MSLB analyses from Westinghouse were used to establish initial  !

conditions for the MONSTER runs. Sections 6.2.1 and 15.4.2 of the Final Safety Analysis Report (FSAR) discuss the MSLB. The MONSTER analyses extended  !

the transient after the end of steam generator blowdown until a steady state containment temperature was reached. The results show that the present I

environmental temperature qualification curve remains bounding for all areas of the lower containment, including the pressurizer enclosure. Key assuniptions and cooler data are provided in attachment 1.

l

The lower containment coolers have been upgraded to safety grade coolers for use in handling RCS heat loads when the plant is in a hot standby condition.

This upgrade required the coolers to be 1E, environmentally qualified, and seismic category 1. The coolers were procured as seismic category 1. The documentation was reviewed and determined to still be valid. The ductwork was ,

designed to be seismic category 1L. Upgrading the ductwork to seismic category 1 required the addition of four new supports and a modification to one existing support. These physical modifications have been completed. The adequacy of the remaining duct supports has been formally documented in calculations. The cooler motors and associated cables were powered from 1E trained boards, and the cables are environmentally qualified. However, qualification of the motors could not be established. The motors were rewound under a contract with Buffalo Forge that establishes environmental qualification by reference to Buffalo Forge test reports. The rewind program also upgraded the motors to 1E, and a seismic report has been provided. The coolers are supplied with essential raw cooling water (ERCW), and the piping is TVA class C or better. The coolers, ductwork, and ERCW piping were also reviewed to establish that pipe whip or jet impingement from secondary side breaks would not impair system operatAon. The FSAR will be revised to reflect this information in the next annual update.

The new technical specification requirements for the containment cooling system were derived from the Standard Technical Specifications (NUREG-0452, revision 4). The action statements were modified to delete containment spray operability requirements. The analyses assume long-term cooling is provided by the coolers only and do not take credit for containment spray once the coolers are placed in operation. The required times to return inoperable equipment to an operable status are consistent with other requirements for loss of containment cooling systems.

The surveillance requirement (SR) for manual fan actuation was modified to reduce the testing interval to 18 months rather than every 31 days. Since these fans are used during normal operation, thus proving fan performance, a SR to stop the fan and then restart it every 31 days is unnecessary.

Verifying manual actuation every 18 months will provide reliable assurance of fan performance and is consistent with manual actuation test intervals for engineered safety feature actuation system instrumentation and emergency core 4 cooling equipment. l The testing interval to verify cooling water flow rate was reduced from every  !

31 days to at least once every 18 months. The purpose of the SR is to demonstrate that a 200-gal / min cooling water flow rate is delivered to the )

coolers. The SR for ERCW operability (SR 4.7.4.9) requires verification of j proper valve alignment to safety-related equipment every 31 days. The plant surveillance instruction that satisfies this requirement will be revised to include necessary lower containment cooler valve verification. Verification q

of proper valve alignment and throttle position will ensure a proper flow path 1 exists to the coolers. Verification of the 200-gal / min flow rate demonstrates ]

i the pump's capability to deliver the required flow.

The SR to verify automatic actuation has been deleted because the fans will only require manual actuation. The analyses showed that the coolers would not i

be required until after ice bed meltout. This will occur approximately 10 hours1.157407e-4 days <br />0.00278 hours <br />1.653439e-5 weeks <br />3.805e-6 months <br /> into the event. Operator guidance has been established to start the coolers between one and four hours after the event. The one-hour time period ensures that the coolers will not be operating until well after the cf- -

end of steam generator blowdown, even for very small breaks. This delay -

in cooler actuation is necessary to ensure that work performed by the fans does not exceed motor capacity. The containment air pressure after steam generator blowdown will have dropped sufficiently at this time to lower the air density the fans are expected to move. The four-hour time period ensures that the coolers will be operating well before a conservative determination of ice bed meltout. Based on these long time periods, manual actuation of the coolers was determined to be acceptable. The coolers can be started and ERCW flow to the coolers established from the main control room. Operator actions outside the control room would only be required if there was a loss of one power train. In this instance, two ERCW valves per cooler located outside containment would have to be manually opened.

Postaccident use of the lower containment coolers and the proposed technical specification requirements ensure the present environmental temperature qualification curve remains bounding for all safety-related equipment inside containment required to remain functional following a non-LOCA event.

1

ATTACKMENT 1 COOLER DATA

, , - 1 Design cooler heat removal capacity at 900 F air outlet and 1200 F air inlet 1.

temperatures: 2,000,000 Btuh. (4,000,000 Btuh per pair.)

2. Design cooler airflow under clean coil conditions: 65,000 cfm (130,000 cfm per pair).

3. Heat Removal per Cooler Pair (Btuh at 122 0F) Total efm Per Cooler Pair clean (new) fan cooler: 3,700,000 at 100,000 cfm clean (new) fan cooler: 100,000 dirty (old) fan cooler: 2,965,000 at 90,000 cfm dirty (old) fan cooler: 90,000 (analyzed) (analyzed)

ASSUMPTIONS

1. The operator will cool the RCS to 350 0F at a rate greater than or equal to 190 F/ hour commencing at 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br /> following the MSLB. The decrease in temperature to 350 F should take 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> following the MSLB.

2. The operator will further cool the RCS in order to attain an RCS hot leg temperature of 250 0 F, 200 hours0.00231 days <br />0.0556 hours <br />3.306878e-4 weeks <br />7.61e-5 months <br /> (8.5 days) following the MSLB.

3. Two lower containment coolers are available for use no earlier than one hour and no later than four hours following the MSLB. The combined flow of these coolers is at least 90,000 cfm and a combined heat removal rate of 2,965,000 Btub at 122 0F air inlet temperature. In addition, the water side of each cooler is assumed to have an inlet water temperature of 83 0 F and a volumetric flow rate of 200 gal / min.

4. Only one train of containment spray operates, and it becomes unavailable after the RWST level reaches its low-low level setpoint. The low-low level setpoint is estimated to occur at 4,250 seconds following the MSLB.

5. Only one air return f an is available and activated 10 minutes af ter a phase B signal is generated. This fan continues to operate throughout the 100-day postulated event.

l i _ - _ _ _ _ -

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.'9' v tr ENCLOSURE 3-

-PROPOSED TECHNICAL SPECIFICATION CHANGES ,, . . .

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SEQUOYAH NUCLEAR PLANT UNITS 1 AND 2' DOCKET NOS. 50-327 AND 50-328 (TVA-SQN-TS-87-37)

DETERMINATION'0F NO SIGNIFICANT HAZARDS CONSIDERATIONS k

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SIGNIFICANT HAZARDS EVALUATION TVA has evaluated the proposed technical specification change and determined that it does not represent a significant hazards consideration based on criteria established in 10 CFR 50.92(c). Operation of SQN in accordance with the proposed amendment will not:

(1) involve a significant increase in the probability or consequences of an accident previously evaluated. The 1SAR assumes the worst case condition for long-term cooling following a steam line break is a loss of offsite power with failure of one emergency power train.

This condition requires the greatest amount of operator action and the longest time to achieve cold shutdown. The analyses demonstrate that the plant can be maintained safely at hot standby conditions for extended periods of time.

With only onsite power available, the plant can be maintained in a safe hot standby condition using the intact steam generators by supplying feedwater with the auxiliary feedwater system end venting steam through the secondary side, power-operated relief valves. The relief valves will be controlled to gradually reduce pressure and  ;

temperature as the core residual heat decays. Two of four steam generators are required to maintain the plant in this safe shutdown condition.

The FSAR considers the containment temperature response resulting from a LOCA to be bounding in all cases. No further consideration was given to the effects of long-terr. recovery from an MSLB or other less severe non-LOCA events, since the mass and energy release had ended within a short period of time. Therefore, the containment EQ i curve was developed without considering the primary system as a major long-term heat source in establishing the most severe inside l

! containment EQ time-dependent temperature profile. Use of the lower (

containment coolers for non-LOCA accident mitigation and the proposed l technical specification requirements will ensure containment temperatures remain within EQ limits for all safety-related equipment ;

required to remain functional following non-LOCA events. >

(2) create the possibility of a new or different kind of accident than l previously evaluated. The proposed change will not affect normal I operation of the plant. A rigorous evaluation of the major heat i sourcer present during the entire accident timeframe has been performed to ensure equipment EQ limits are not exceeded, j Modifications were made to upgrada the lower containment coolers to I ensure reliable operability during accident conditions. All safety l system interfaces have been evaluated to ensure that the required use of the coolers does not degrade other safety systems expected to be i operable during the accident. Operator action during the accident is not a burden because a very flexible time period is allowed to complete the required actions. The proposed testing requirements do not require unusual plant configuration and thus do not create a different type of accident than previously evaluated.

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(3) involve a significant reduction in a margin of safety. The proposed change adds technics.1 specification requirements for the lower  !

containment coolers since thesa coolers now have an assumed role in accident mitigation of non-LOCA events. This role.is to keep _,

containment temperature within operating limits of equipment required

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to maintain the safety of the plant. Continued reliable operation of safety-related equipment provides assurance that the margin of safety has not been reduced.

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