ML20207J656

Proposed Tech Specs,Revising Limiting Condition for Operation 3.2.2 & Surveillance Requirement 4.2.2.2 to Reflect Reduction in Heat Flux Hot Channel Factor Limit from 2.237 to 2.15

ML20207J656
Person / Time
Site:	Sequoyah
Issue date:	09/21/1988
From:	TENNESSEE VALLEY AUTHORITY
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ML20207J647	List: ML20207J644 ML20207J656
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NUDOCS 8809280073
Download: ML20207J656 (28)

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,f a ENCLOSURE 1 PROPOSED TECHNICAL SPECIFICATION CHANGE SEQUOYAH NUCLEAR PLANT UNIT 1 DOCKET NO. 50-327 (TVA-SQN-TS-88-28) -

LIST OF AFFECTED PAGES Unit 1 3/4 2-5 3/4 .'-6 3/4 2-7 d

8809280073 PDR P

86092}27 ADOCK 050003 PDC 1

r ..- l POWER OISTRIBUTION LIMITS 3/4.2.2 HEATFLUX-HOTCHANNELFACTOR-Fg LIMITING CONDITION FOR OPERATION i 3.2.2 F9 (Z) shall be limited by the following relationships

4./5" 4

Fq (Z) 1 [e-9-3+2 [K(2)] for P > 0.5 P

a./S' .

i F9 (Z) 1 [P-fW) 0.5

[K(Z)] for P 10.5 w ere P = THERMAL POWER RATED THERMAL POWER i

and K(Z) is the function obtained from Figure 3.2-2 for a given core height location.

APPLICABILITY: MODE 1 n23 7 ._ . . _ . _ ACTION: -

With Fq (Z) exceeding its limit:  !

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Reduce .aERMAL POWER at least 1% for each 1% q F (Z) exceeds the limit

l 1 within 15 minutes and similarly reduce the Power Range Neutron j Flux-High Trip Setpoints within the next 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br />; POWER OPERATION may proceed for up to a total of 7? hours; subsequent POWER OPERATION 3

may proceed provided the Overpower Delta T Trip Setpoints (value of K4 ) have bean reduced at least 1% (in .iT span) for each 1% F (2)

, exceeds the limit. 9 (

4 j b.

Identify and correct .the cause of tr.e out of limit condition prior '

to increasing THERMAL POWER; THERMAL. POWER may ther. be it.crissed

provideo Fq (Z) is demonstrated *?. ough incrc mapping to be within l l its limit. $

$URVE!LLANCE REQUIREMENTS 4.2.2.1 The provisions of Specification 4.0.4 are not applicable.

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e 4 $ '

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POWER DISTRIBUTION LIMITS SURVEILLANCE REQUIREMENTS (Continued) 1.

4.2.2.2 Fq (z) stia11 be evaluated to determine if F (Z) is within its limit by: 9

a. Using the movable incore detectors to obtain a power distribu- ,

tion map at any THERMAL POWER greater than 5% of RATED THERMAL POWER.

b. Increasing the measured Fggg) componsnt of the power distribution map by 3 percent to a.ccount for manufacturing tolerances and further increasing the value by 5% to account for measurement uncertainties.

c. Satisfying the following relationship:

2./f i

FQ "(z) < P g W(z)* U 2) for P > 0.5 FQ "(z) < W(z) x 0.5) for P < 0.5 -

where F"(z) is the measured F (z) increased by the allowances for 9

manufacturing tolerances and measurement uncertainty,q F limit is the Fq limit, K(z) is given in Figure 3.2-2, P is the relative THERMAL POWER,and W(z) is the cycle dependent function that accounts for power distribution transients encountered during normal operation. This function is given in the Peaking Factor Limit Report as per Specification 6.9.1.14.

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d. Measuring Fq (z) accort ng to the following schedule:

1. Upco achieving equilihefum conditions after exceeding oy 30 porcent or more cf RATED THERMAL POWER, the THERftAL POWER

, at which F (z) was Inst determined,* or q

2. At Itast ence per 31 effective full power o,,s, whichever occurs first.

"During power escalation at the beginning of eact, cycle, power level may be increased until a power level for extended operation has been achieved and a power distribution map obtained. 1 9

0 ;; 'c- ? ? . 1^ S 2:

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SEQUOYAH - UNIT 1 3/4 2-6 s c m ,t- A -t9-

,y -.-egrem,me+-r&q y-=-- yN--=1- *

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~ POWER DISTRIBUTION LIMITS l

1 SURVEILLANCE REQUIREMENTS (Continued)

e. With measurements indicatin f

maximum F0 (2) over z k K(z) I has increased since the previous determinatin of F "(z) either -

of the following actions shall be taken: 0

1. F M(z) shall be increased by 2 percent over that specified in 9

4.2.2.2.c, or 2 Fg M(z) shall be measured at least once per 7 effective full power days until 2 successive maps indicate that maximum F" (z) is not increasing. R23 over I K(z)

( j

f. With the relationships specified in 4.2.2.2.c above not being satisfied:

1. Calculate the percent F (z) exceeds it' limit by the following expression: 9 r

1lImaximum H

Fn (z) x W(z) I -1 x 100 for P ), 0. 5 S' over z 2 0

7 x K(z)

M /I .. ,

M -

maximum Fn (z) x W(z) _1 x 100 for P < 0.5 over z ,y M- l 1 O.T'

• KC3) 'j '

r %I5 - ,1

2. Either of the following actions Shell be taken:

a. Olact the core in an equilibrium condition where the limit in 4.2.2.2.c is satisfied. Power level may then be increased provided the AFD limits of Figure 3.2-1 are reduced 1% AfD for each percent qF (z) exceeded its limit, or

b. Comply"with the requirements of Specification 3.2.2 for F (2) exceeding its limit by the percent calculated above.

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SEQUOYAH - UNIT 1

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ENCLOSURE 2 r

PROPOSED TECHNICAL SPECIFICATION CHANGE SEQUOYAH NUCLEAR PLANT UNIT 1 DOCKET NO. 50-327 (TVA-SQN-TS-88-28) .

DESCRIPTION AND JUSTIFICATION FOR REDUCTION IN HEAT FLUX HOT CHANNEL FACTOR LIMIT 6

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ENCLOSURE 2 Description of Change Tennessee Valley Authority proposes to modify the Sequoyah Nuclear Plant Unit i technical specifications to revise limiting condition for operation 3.2.2 and surveillance requirement (SR) 4.2.2.2 to reflect a reduction in the heat flux hot channel factor (Fq[z]) limit from 2.237 to 2.15.

Season for Change By letter dated August 15, 198R, TVA submitted proposed license amendment 88-20. This proposed change revised the upper head injection (UHI) isolation setpoint and tolerances of SR 4.5.1.2.c.1. Enclosure 2 of the August 15 letter describes that, as part of the setpoinc change, the delivered UH1 water volume band was being expanded from the range of 1,130.5 to 900 cubic feet to the range of 1,130.5 to 850 cubic feet. The change in the delivered UHI water volume band was supported by Wastinghouse Electric Corporation (W) evaluations, which indicated that the potential decrease in delivered water volume to the core would result in increased peak clad temperatures (PCTs); but in all cases, PCT remained below the 2,200 degree Fahrenheit (F) limit of 10 CFR 50.46.

In telephone conversations on September 1 and 2,1988, NRC informed TVA that the increased PCTs described in the August 15, 1988 submittal could not be wholly justified by the sensitivity studies provided. NRC stated that restart of unit 1 could be supported by the sensitivity studies (provided a temporary exemption to certain administrative requirements of 10 CFR 50.46(a)(1) was obtained) and that operational restriction be imposed to provide at least 100 degrees F of margin between the calculated PCT and the 10 CFR 50.46 limit.

TVA's request for a temporary exemption to certain administrative requirements of 10 CFR 50.46(a)(1) will be transmitted by separate correspondence.

Evaluations by E have determined that at least 100 degrees F PCT margin can be obtair.ed by administrative 1y limiting steam generator tube plugging to 5 percent and by reducing Fq(z) from 2.237 to 2.15. This proposed technical specification change is being submitted to reflect the reduction l in the Fq(z) limit. l Justification for Change As defined in'SQN Final Safety Analysis Report (FSAR) section 4.3.2.2.1, Fg(z) is the maximum local heat flux on the surface of a fuel rod

, divided by the average fuel red heat flux. Limiting this ratio minimizes the magnitude of localized "hot spots" along the fuel cladding surface. ,

This in turn helps ensure that PCTs will remain below the 10 CFR 50.46 '

limit of 2.200 degrees F during postulated loss of coolant accident (LOCA) gonditions. l 1

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The proposed reduction in Fq(z) is a conservative change and will provide additional margin in PCT. As described in the attached y evaluation (page 4), a reduction in Fg(z) from 2.237 to 2.15 reduces PCT by 87 degrees F for the limiting imperfect mixing case and by 96 degrees F for the limiting pdrfect mixing case. As summarized on page 5 of the evaluation, this PCT reduction, combined with the reduction obtained by  ;

administrative 1y limiting steam generator table plugging to 5 percent, i results in PCTs of 2,089 degrees F for the limiting imperfect mixing case '

and 2,067 degrees F for the limiting perfect mixing case. As can be seen, these PCT values provide over 100 degrees of margin to the regulatory PCT l 1

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September 14, 1988 Westinghouse PowerSystems Electric Corporation NVC!ttf I M hn0lCgy Sr*$ Daca b 315 PmsutgiPeesyNan!a 15m 0355 Mr. P. G. Trudel 'IYA-88-761 Sequoyah Project Engineer NS-OPLS-OPL-II-88-572 Tennessee Volley Authority Ref.1) TVA RD #428873 Sequoyah Nuclear Power Plant, DSC-A 2) W G.O. CO-42680 P. O. 2000 3) TVA-88-746 Soddy Daisy, TN 37379 TDINESSEE VALLEY AUTHORITY SEQUOYAH UNITS 1 & 2 CECREASED UHI VOLUME DELIVERY LOCA SAFETY EVALU (SECL-88 1417 Revision 1)

Dear Mr. Trudel:

In accordance with our telecon of Septcrtber 7,1988, the LOCA safety evalua SGTP, and a supplemental inforr.ation doeur.cnt is be NRC request for additional infomation addressing the LOCA models refere clarification of the appropriate limiting breaks, and clarification of the effect of the postulated instrtcentation thimble and guide tube flexuro failurcs.

The revised LOCA safety evaluation, SECL-68117, Revision 1, entitled, Safe 4

Evaluation Volu:ne (LOCA, forSOTR, a 50Post-LOCA Cubic Feet Decrease Long Tem Core Coolingin the UHI and Hot Acomulator Leg Switcho Accident), is attached.

This revision incorporates the impact of reducing F(Q) frca

55. 2 32 to 2.15 and the Steam Generator Tube Plugging (SGTP) level tecn 10 The supple:nental Infontation interv.ation to SECL-88-417, Revision doctment

1. is also attached and is entitled Supp If you have any ecccents or questions, please contact the undersisned.

Vory tettly yours, WESTINGHOUSE ELECTRIC CORPORATION

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rdi, Manager ESSD Projects L. V. Tomasic/tu Hid-South Area Attach:r.cnt -

cc.: D. W. Wilson W. R. Mangiante S. J. Smith R. W. Headows J. A. Vcgel R. C. Weir M. J. Bur ynski R. G. Davis R. E. Ibniels M. J. Ray i

SECL NO:_SECL-88-417 Rev, i Cucttmar R3forcnco No(o) .

Westinghouse Ref. No.

WESTINGHOUSE NUCLEAR SAFETY EVALUATION CHECK LIS"

1) NUCLEAR PLANT (S) SEOUOYAH UNITS 1 AND 2 (TVA/ TEN) _ . _ _ _

2) CHECK (subjectLIST APPLICABLE To: SAFETY EVALUATION FOR A 50 CU.FT. DE of Change)

_THE UNI ACCUMULATOR DELIVERABLE WATER VOLUME

3) The written or safety evaluation of the revised procedure, design change modification required by 10CFR50.59 has been prepared to the extent required and is attached.

If a safety evaluation is not required or is inconplete for any reason, explain on Page 2.

"s-Parts A and B of this safety Evaluation Check List are to be comploted only on the basis of the safety evaluation performed.

CHECK LIST - PART A _ -

(3.1) Yes X No _AchangototheplantasdescribedinthehSAR'?-~ ,

(3.2) Yes No X _ A change to procedures as described in tho FSAR?

(3.3) Yes _

No X A test or experiment not described in the FSAR?

(3.4) Yes_ X No A change to the plant technical specifications (Appendix A to the operating License)?

4) CHECK LIST - PART B (Justification for Part B answers must be included on Page 2.)

(4.1) Yes No X

_ Will the probability of an accident previously (4.2) Yes No X evaluated in the FSAR be increased? <

Will the consequences of an accident previously (4.3) Yes No X evaluated in the PSAR be increased?

May the possibility of an accident phich is different than any already evaluated in tho ,

FSAR be, created?

(4.4) Yos_. No X' Will the probabi.lity_of a malfunction'of equipment important to safety previously evaluated in the FSAR be increased?

i (4.5) Yen __ Ho__X__ Will the consequences of a malfunction of equipment important to safety previously evaluated in the FSAR be increased?

(4.6) Yes No X May the possibility of a malfunction of equipment j

important to safety different than any alrnady evaluated in the FSAR be created?

(4.7) Yen Ho X Will the margin of safety as defined in the bases to any technical specification be reducod?

PAGE 1 OF 2

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• SECL-88-417 Ravicion 1 If the answers to any of the above questions are unknown, indicate under 5) REMARKS and explain below.

If the the answer to any of the above questions in 4) cannot be answered in negative, approved withoutbased on written safety evaluation, the change cannot be pursuant to 10CFR50.90. an application for license amendment submitted to NRC

5) REMARKS:

The following surunarizes the justification upon evaluation, (1) for answers the writton safety Check List: given in Part B of the Safety Evaluation N.

seo the attachment

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(1) Roference to document (s) containing written safety evaluationt -

11S -S AT-S AI-8 8 - 3 6 2 FOR FSAR UPDATE Section:-- Pago (s) : Tabl e (s ) : __15. 4 .1-9 ._

Reason for/ Description of Change:

_ Chance reflect Table 15.4_.19 for UHI AccuM>1ator_ water volume delivered to 850 cu.ft, mininum volume evaluated in this safety evaluation and the associated footnote. -- ,_

6) APPROVAL LADDER ,  ; ,

(6.1) Prepared by (Nuclear Safety): 4^- ( S AI i Date: / b Roviewed by (Nuclear Safety):.7//. 8. 23dadu ISAI)

(6.2) Coordinated with Engineer (s)D A/O 86V/GWO(SATI) '

Datos_f/h'/88

_Dato:

Coordinated vith Engineer (s):

Coordinated with Engineer (s): A/6d N M M(TSA1_.Date:

PBon//OO4 AF-(coal _Date s Coordinated with Engineer (s):yPPoud<- 5 ruasAI) Dato u-(6.3) Coordinating Group Managor(s) l A PPuc_a:;. s/W4%AII) Dates coordinating Group Managor(s) )CULY Ml4C (TSA) Date:

Coordinating Group Managor(s)

(6.4) Nuclear Safety Group Managers PMAL h b blOCA' d d /SA1)coa /6Date Date: [.M4A/CE~D_

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. WESTINGHOUSE PROPRIETARY CLASS 2 SECL-88-417 REVISION 1 SAFETY EVALUATION FOR SEQUOYAH UNITS 1 AND 2 FOR A DE IN THE UHI ACCUMULATOR DELIVERABLE WATER VOLUME BACKGROURQ In 1 and order2,to accommodate relaxed UHI system tolerances at Sequoyah Units of Tennessee Valley Authority (TVA) has requested a widened set decrease limits on the allowable UHI water delivered volume. Specifically, a uncertaintyin the required from 900 to minimum UHI delivered water volume considering 850 ft3 has been requested.

presents the summaries of The following effect of a 50 ft 3 safety evaluations performed to assess the reduction in the minimum volume on the LOCA-related analyses UHI delivered water performed by Westinghouse for Sequoyah Units 1 and 2.

N._

BASES

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LARGE BREAK LOCA - FSAR CHAPTER 15.4.1 ~~

In 1 order to accommodate relaxed UHI system tolerances at Sequoyah Units water and dalivered 2, TVA has requested a widoned set of limits on the allowable UHI volume. To this ond, the Sequoyah Large Break ECCS performanco analysin has been reviewed to justify a decrease in the required minimum 850 ft3 UHI delivered water volume considering uncertainty to The limiting case break in the UHI presented in the original Evaluation Model EccS analysin sequoyah FSAR with imperfect mixing of was the C D=0.6 DECLG break Comp 11anco with regulatory UHI water assumed in tho vasool uppor head.

limits was achieved for reducing the allowable core peaking this case b y..

Minimiting the volume of UHI f factor (F q) from 2 32 to 2.237.

imperfect mixing UHI LOCA cases. wator._ delivered is conservative for volume delivery established in The lower bound value for UHI water the original FSAR C9=0.6 imporfect mixing caso is 900 DECLG ft 3.

the imperfect mixing cases of Thin value also was amployed in analysis performed in thethe 10% steam generator tube plugging I

(SGTP) 1982-83 timeframe and reported in ROferenco 1.

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• WESTINGHOUSE PROPRIETARY CLASS 2 SECL-88-417 REVISION 1 SAFETY EVALUATION FOR SEQUOYAH UNITS 1 AND 2 FOR A DECR IN THE UNI ACCUMULATOR DELIVERABLE WATER VOLUME A complete spectrum of perfect mixing cases wa s. analyzed for the original Sequoyah FSAR.

water assumed in the The limiting case with perfect mixing of UHI vessel upper head was calculated peak clad temperature the C p=0.6 DECLG; the UHI delivered (PCT) for this case is 2111'F at an Fq of 2.32 with a sensitivities water volume of 1053 f t3

.* Using have previouslyappropriate been made to UHI plant perfect mixing cases, trade-offs increasing the maximum among various input assumptions to justify 1130.5 3 allowable UMI delivered water volume to ft . Maximizing the value of UHI water conservative for perfect mixing UHI LOCA analyses. delivered is Specification Fq of 2.237 in force, With a Technical delivered 1130.5 ft 3 is a valid maximum water of the limiting volume for the sequoyah UNI system; the calculated -PCT C p =0.6 DECLC water delivery is 2163*F.

perfect mixing caso at 1130.5 ft3 UHI

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The Cp=0.8 and CD=0.6 DECLG 10% SGTP analysis havo been reviewed to imperfect mixing cases from the 1982-83 reducing the delivered UHI assess the PCT impact of Reference 1 PCTs for the C =0.8 water volume to 850 ft3 The calculated p and CD =0.6 DEcLG cases which compriso the current licensing basis for Sequoyah are 2111'T and 2113'F, respectively.

mixing case will reducoReducing the UHI water delivory in an imperfect the couling of L

drains during blowdown. the fuel as the uppor head During the core reflood phace, thin hottor fuel will cause tho axpulsion liquid, producing a degraded of moro injection water as entrained flooding rate. Existing Soquoyah imperfect mixing cases defino the penalty in coro heat-up associated with decreasing UMI fuel es a flooding rate penalty, water delivery to 850 ft 3. Expressed roducing UHI watsr delivery to 850 ft3 reduces core inlot, velocity .

mixing cases. by; 7% for the licensing basis icporfect The effect of been dotermined degraded by flooding rates upon hot rod calculated PCT has WREFLc0D/LOCTA sensitivity runs. Expressed as an imperfect mixing case PCT sensitivity relationship, decreaco in a one ft3 in calculated PCT.

UNI water delivery results in approximately a l'F incresco cro acceptable The 10% SGTP licensing basia imperfect mixing cason at an 850 ft 3 delivered UH1 water volume becauco the degradod reflood penalty only increases calculated PCT as followst Page 2 e.- . . . - - - . .-%,..--. = = ~ -

• WESTINGHtOSE PROPRIETARY CLASS 2 SECL-88-417 REVISION 1 SAFETY EVALUATION FOR SEQUOYAH UNITS 1 AND 2 FOR A DECRE IN THE UHI ACCUMULATOR DELIVERABLE WATER VOLUME CD=0.8 DECLG PCT =2151*F CD=0.6 DECLG PCT =2166*F

! A separate safety ' evaluation 1986 performed for Sequoyah during November, considered tube flexure failures. the impact of a possible but unlikely scenario of guide The PCT penalties imposed upon perfect and imperfect mixing cases under this scenario respectively. are O'F and 20'F4 The not PCT for the limiting imperfect mixing C D=0.6 DECLC case therefore becomes 2166'T + 20'F = 2186'T whhn-postulated guide tube flexure failures are considered. -

t A further phenomenon PCT values is which could impact the Sequoyah Plant calculated- -

filling of the instrumentation thimbles in the core ~

during the reflood phase volume which must be filled has of a large break LOCA event. The thimble

, Sequoyah large break LoCA analyses. not been explicitly treated in the  !

that the thimble plugging Westinghouse had initially assumed devices would be sufficiently tight to prevent the ingress of water was later identified into thimbles during reflood. However, it i

and the flows were sufficiently that the plug clearances were sufficiently large ,

low reflood to allow the thimbles to fill with water even withduring plugs installed.

which thimble The impact ~

casossed for filling will exert on the calculated PCT values has been perfectSequoyah, and the appropriate PCT penalties to be imposed '

on the and 12'F. The not imperfect mixing casen are established as O'F and I becomes calculated PCT for the limiting imperfect mixing cane 6 L

{ 2186'T + 12'F = 2198'T _ - - - - --

1 co compliance with the regulatory limit is maintained.

j Ao previously noted, the imperfect mixing cases of Reference 1 have been i

performed assuming 10% uniform steam generator tube plugging. The cetual SGTP level at Sequoyah Units  ;

oteam generators. 1 and 2 is less than 3% in all WCstinghouse In performing the 1982-83 imperfect mixing analyses, PCT and identified the sensitivity relationship between calculated assumed SGTP level.

nixing ' case, increasing the SGTp For the limiting C =0.6 D DECLC imperfect level from 2% to 10% produced an increase of 36'T in calculated PCT to the 2113'T value.

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WESTINGHOUSE PROPRIETARY CLASS 2 SECL-88-417 REVISION 1 SAFETY EVALUATION FOR SEQUOYAH UNITS 1 AND 2 FOR A D IN THE UHI ACCUMULATOR DELIVERABLE WATER VOLUME Taking credit for the excess margin in SGTP will calculated permit the not case to be PCT for the reduced. Sequoyah To Units 1 and 2 limiting imperfect mixing plugging of steam retain some margin for the possible future 5% uniform plugging generatorlevel.

tubes, revise the SGTP basis to reflect a (36'F), or 22'F, Then the calculated PCT is reduced by 5/8 giving a new not calculated for the limiting PCT of C =0.6 D DECLG imperfect mixing case, 2198'T - 22*F = 2176'T The NRC Staff has specified that at least 100*F margin regulatory limit of 2200*F to the should bo demonstrated in e)aluation to justify Sequoyah Unit 1 Cycle this safety benefits must therefore be found to 4 operation. Further imperfect mixing reduce both the perfect and limiting case calculated taken is PCT values. The approach- ~

to maintain 100% power operation while reducing the technical specification allowable maximum peaking factor (Fq) value.

The sensitivity relationship between calculated PCT and Fq has been ostablished for analysec. both imperfect and perfect mixing UHI evaluation model is For UHI impe:"act mixing casos, the sensitivity relationship 10*P decrease in calculated DCT 0.01 decresse in Fq value ,

For Sequoyah Unito 1 and 2, decrease the Fq value from 2 237 The corresponding decreano to 2.15.

87'F, giving a net calculated in calculated PCT is (0.087) (10'F/0,01) =

limiting C =0.6 p DECL4 cane.  ;

PCT of 2176'F - 87'F = 2089'F ter the~

For UHI octablished. perfoot mixirg caoos, tne equivalant sensitivity has also been The sensitivity rolationship for perfoct mixing in ll'F decreaso in calculated pct 0.01 decrease in Fq value Therefore, the reduction in (11*F/0.01) Fq to 2.15 will produce a PCT benefit of (0.087) = 96*F for Sequoyah perfect mixing cacou.

limiting co =0.6 DECLG perfect mixing The of 2163 - 96 a 2067'T at an Fq value of 2.15. case exhibits a calculated PCT Page 4

' ' WESTINGHOUSE PROPRIETARY CLASS 3 SECL-88-417 REVISION 1 SAFETY EVALUATION FOR SEQUOYAH UNITS 1 AND 2 FOR A DECREA IN THE UMI ACCUMULATOR DELIVERABLE WATER VOLUME To summarize, by reducing peaking factor the technical specification limit on total obtained for Sequoyah (Fq) to 2.15 additional peak clad temperature margin is Units 1 and 2.

become 2089'F The net calculated PCT values cases respectively; greater thanand 2067'T for the imperfect and perfect mixing limiting the regulatory limit of 100*F margin in PCT is available to delivered water volume band of 850 -2200'F for Segacyah Units 1 and 2 with a UHI 1130.5 cu. ft.

SMALL BREAX LOCA The Current was performedFSAR small break LOCA analysis for Sequoyah Units 1 and 2, using the NRC-approved UHI Small Eviluation Model (Reference 2), which resulted in the most limiting PCT Break LOCA ECCS of 1486'T for a 8 inch safety evaluation equivalent diameter break (Reference 1). A shortfall increased this result by which considered the ef fect of charging /SI pump flow- -

200*F, resulting in an overall licensing basis PCT of 1686'F.

The because reason the 8 inch break is limiting and exhibits a low PCT value is UHI provides otandard plant systema. enhanced safety injectica capability relativo to or four-inch equivalent Typically, 4 loop plants demonstrate the throo diameter break to ho limiting at a higher calculated PCT than the Sequoyah valuo.

inherently beneficial Becauso UHI injection is the Sequoyah FSAR for the evaluation model r, mall break LocA evout, the minimum UHI doliverable analysis has assumed a conservatively lov value for ~

water ft. Thorofore, volumo which is loss than 850 cu.

cu. ft. a decrease in the delivorablo UHI water volume to 650 does not adversoly affect the FSAR small break LOCA results.

! ROD EJECTION HASS AND ENERGY R2 LEASE

' FOR DOSE CALCULATION - FSA i

CHAPTER 15. 5. 7 AND TdBIE 15. 5. 7 3 - -

Similar to a small break LOCA, parformed a rod ejection accident analysin is to provida primary and secondary mass and energy releases for uce in computing the radiological consoquences of a rod ejection accident as por Regulatory Guido 1.77.

trannient performed specifically to dete rmine This analysis is a long term primary RCS hass and energy releanos through the upper head break and secondary maus and Cnergy releases via the secondary code safoty valves.

These mass and energy releases aro then upod to computo the radiological consequences Pago 5

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' WESTINZHLUSE PROPRIETARY CLASS 2

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SECL-88-417 REVISICH 1 SAFETY EVALUATION FOR SEQUOYAH UNITS 1 AND 2 FOR A DECRE!3E IN THE UMI ACCUMULATOR DELIVERABLE WATER VOLUME of a rod ejection accident.

water A reduction in the minimum deliverable UMI of the volume will result in an increase in the mass and energy releases releases. primary coolant and a decrease in the secondary mass and enorgy However, was used regarding for the Sequoyah Units, a conservative assumption the primary mass and energy releases such that the not effect of a 50 ft3 reduction in the minimum deliverable UHI water volume is a reduction in secondary mass and energy releases. Since a net reduction in secondary mass and energy releases would slightly reduce the computed doses, the current doses as reported in Table 15.5.7-2 of Reference i remain bounding.

CONTAINMENT INTEGRITY -

FFAR-CHAPTER 6.2 (SHORT AND LONG TEKM MASS AND ENERGY RELEASE The containment analyses sections for the Sequoyah Units are described in FSAR- ' -

6.2.1.3.3, 6.2.1.3.4, sections consider, respectively, 6.2.1.3.6. and 6.2.1.3.11. Theno ~

long and short term analyse 4 containment pressure transients for LOCAs and mass and energy releases for postulated containment subcompertments, and containment maximum temperature renponse following a main oteamline break.

For Cnergy the containment subcompartment analyses and the short term mass and relcare analyses no modelling of tne UHI accumulator is included. Therefore, a 50 ft3 veduction in the minimum delivorable water volume to 850 ft3 will have no effect on the current analyses. ~

The long term me r.s and enorgy rolosse analysin is performed to calculate the maximum availa'ola releasos which can enter the containnant foll owing a LOCA.

no modelling of the Simil.nr to the subcompartment analyses, deliverable UHI waher volunk of'650 ft3is included therefore, a minirum UHI accumulator mass and energy releases to contaihmenc.

.will.not effect the long term The evaluation for no change in the mass main and steamline break concluded that there would be reduction in minimum deliverable energy releases to the containment for a UHI water to less than 850 ft3 Therefore, the containment maximun temporaturo tain response following a steamline break will not be effected. Hence, based upon the above internation, the results of the current Chaptor Integrity analyses continue to be valid. 6.2 containment Pago 6 we ,

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^ WESTINGHOUSE PROPRIETARY CLASS 2 SECL-88-417 REVISION 1 SAFETY EVALUATION FOR SEQUOYAH UNITS 1 AND 2 FOR A DECR -

IN THE UMI ACCUMULATOR DELIVERABLE WATER VOLUME STEAM GENERATOR TUBE RUPTURE - FSAR CHAPTER 15.4.3 The steam generator equilibrates tube rupture event as analyzed in the Sequoyah FSAR in pressure UHI nitrogen gas pressure at a value which greatly exceeds the maximum actuated of 1300 psia. Since the UMI system is not during change in UHI a design basis steam generator tube rupture event, any delivered this analysis. water volume upon actuation is irrelevant to BLOWDOWN N. m REACTOR VESSEL AND LOOP FORCES - FSAR CHAPTER 3.9 The blowdown hydraulic forcing functions resulting coolant accident are considered from a loss of Under LOCA in Section 3.9.1.5 (Analysis Nethods- ~

and Loadings), and Section 3.9.3.5 (Blowdown Forces Due-to. Cold' decrease Hot Leg Break) of Volume 4 of the Sequoyah Units 1 and 2 FSAR. The i

LOCA in thehydraulic blowdown UHI accumulatorloads since water volume will have no effect on the within the first few the maximum loads are generated this reason tenths of a second after break initiation. For in the the ECCS, including the UHI accumulator, is not considered accumulator LOCA hydreulic forces modeling and thus the decrease in the UHI hydraulic forces water voluno will have no of fect on the resu?.ts of the LOCA calculations.

POST LOCA LONGTERM CORE C00L7NG SUBCRITICALITY REQUIREMENT; WESTINGHOUSF LICENSING POSITION - 7SAR CHAPTER 15 4.2 i

The Westinghouse 100FR Part licensing position for satisfying the requirements o is defined 50 sect' ion 50.46 Paragraph..(b)_ Item (5) "Long Tarn cooling" in WCAP-8339 (Reference 4, pp. 4-22). The Westinghouse commitment is that the reactor water residing in the sump Will remain shutdown by boratnd ECCS following a i credit for the control rods is LOCA (Reference 5). Sinco

borated ECCS water provided not taken for large break LOCA, the concentration that, when mixedbywith the RWST and Accumulators must have a other sourcos of water, will result in the reactor core remaining suboritical assuming all control roda out The docrease in the minimum (ARO)3 50 ft UHI water delivered voluno or

. _ results in a reduction of approximately 1 ppm in the mixed 1

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.a r 4-.oo Ao; v r.12 WESTINGHIUSE PROPRIETARY CLASS 2 SECL-88-417 REVISION 1 SAFETY EVALUATION FOR SEQUOYAH UNITS 1 AND 2 FOR IN THE UMI ACCUMULATOR DELIVERABLE WATER VOLUME mean sump boron concentration.

boron concentration This reduction in the mixed Aean sump the current cycles of operation for Sequoyah Unita 1 and 2.can b 1

NOT LEG SWITCHOVER TO PREVENT POTENTIAL CHAPTER ' 2.2 BORON PRECIPITATION - FSAR The het <-

• or Sr reoirculation switchover time analysis has been performed kot ' nits 1 and 2 to determine the time following a LOCA that com 4 41stion oren should be initiated. This analysis addresses the

' nt precipitation in the rea? tor vessel following a LOCA j '

- ir performed to support the decrease of 50 cubic feet in the ator volume to 850 cubic feet. - -

Du. a the largeRWST break LOCA the plant switches to cold leg recircula lon- '

afti in the cold leg switchover setpoint has been reached. If the break is will fail to there establish flow is a concern that the cold lag injection water entering the broke.n loop through the core, safety injection the intact cold legs will spill out the break, wn11e SI entering break. will, circulate around the downcomer and out the coro rkeajns With no flow path established through the core the fluid in t no stagnant. Au .

heat, the boron associated stcan is produced in the core from decay Thus, .n w water with the steam will renain in the vessel'.'

the is boiled off with no circulation present in the core vesselbocic acid concentration incraases. ,

i will increase until the solubility The boron concentration in tho colution limit of the boric acid the boron in reached, at which time boron will begin to precipitate. As -

cdversely affect the'ir heat transfer characteristics.precipitatus, The provide purposethe of the hot leg recirculation switchover time analysis in to prevent boron precipitationtime at which in hotthe legcore.

recirculation munt be established to An evaluation has been performed ,

reduction of to determine the effect of tho the hot 3cg the deliverablo voluno of water in the UllI accunulator on that the time recirculation switchover time. This evaluation concluded is bounding .

for hot leg switchover contained in the FSAR (13 hours1.50463e-4 days <br />0.00361 hours <br />2.149471e-5 weeks <br />4.9465e-6 months <br />)

Therefore, the valuo in the FSAR need not be changed.

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.* WESTINEHOUSE PROPRIETARY CLASS 2 SECL-88-417 REVISION 1 SAFETY EVALUATION FOR SEQUOYAH UNITS 1 AND 2 FOR A DECREAS IN THE UMI ACCUMULATOR DELIVERABLE WATER VOLUME CONCLUSIONS The 50 effect on the 00CA related analyses for Sequoyah Units 1 and 2 of a ft 3 reduction in the minimum deliverable UHI water 850 ft3 has been evaluated by Westinghouse. volume to the change on the The potential effect of accidents was FSAR analysis results for each of the LOCA-related evaluated, of the chance did not and it was shown in all cases that the effect result limit. in exceeding any design or Regulatory Therefore, it is be concluded that the proposed decrease in the minimum deliverable UHI water to 850 ft" for Sequoyah Units 1 and 2 is acceptable from the standpoint of the FSAR accident discussed in this safety evaluation. analyses Table 1 lists the effect of the change on the various accidents which are discussed here.

REFERENCES 1.

Sequoyah Station (TVA/ TEN) FSAR - Updated 6/16/86 Amendment 3.

2. WCAP-8479 Rev. 2 (Proprietary), WCAP-8400 Rev. 2 (Hon-Proprietary), Young, H.Y.,

Emergency Core et. al., "Westinghouse Cooling System Evaluation Model Application to Plante Equipped with Upper Head Injection", January 1975.

3. WCAP-9220-P-A (Proprietary),

Eiche1dinger, WCAP-9221 (Non-Proprietary), '

C., "Westinghouse Version", Revision 1, 1981. ECCS Evaluation Model - 1981

4. KCAP-0339 (Non-Proprieta ry) , Btrdslon, F.H., 9t. al.,

"Westinghouse Ecc3 Evaluation Model - Summary", June 1974.

5. Westinghouse Technical Bulletin NSID-TB-86-08, i "Post-LCCA Long-Term Coolingt Boron Requirements", October 31, 1986. ,

)

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1 WESTINGHOUSE PROPRIETARY CLASS 2 SECL-88-417 REVISION 1 SAFETY EVALUATION FOR SEQUCYAH UNITS 1 AND 2 FO IN THE UHI ACCUMULATOR DELIVERABLE WATER VOLUME TABLE 1 FSAR CHAPTER ACCIDENT DESCRIPTION IFFECT ON RESULTS 15.4.1 Large Break LOCA P clad

$gk 100 by temperagure is re$uc$ng"t$egoaS h$tk 10C maintained. 56.46bf$b$f Ss 15.3.1 Small Break LOCA No adverge SAR or gffectonthe{$nk 1 t $ax:,mbm'$$ add "

oxkhat$gn$o$ max:. gum hydroge 15.5.7 $bCfR50N6b(1-hfbah,$ta$ned.

Rod Ejection Accident No adversg effect on magn and h$tk kbC 6.2 maintained.hR100.1$ lE$$t!

Containment (Short and LongIntegrity Term No pdverse effect on short Mass and Energy Release) or ton torn mass and one geas vgs '

g on Sn$ts u thus 15.4.3 Steam Generator Tube Rupture No adverno effect on primary-o-s g gpa$ntaLned.

g$$$to ary g s g goc 1

3.9 B1 an$wdownMoactorVassal Loop Torcee No advprse off at an LOCA aydrausicforcIngfunctions.

15.4.1 g CA Longterm core g doog in g gs CA 6.3.2.2 Hot to

$0bfR$0$$6b($fI Switchover to Preven Potential PSAR ont-10CA hot lea Prec;p tation Boron MVite over time remains Dound ng.

Pago 10 O

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, .. ... .... .~ r .,.v. .v... c.is ATTACHMENT!

' . SUPPLT. MENTAL INFORMATION TO SECL-88-417 REVISION 1 1ARGE BREAX 14CA ANALYSIS The UHI Evaluation Mod 71 dates from 1978 (Reference 2), and it received NRC approval in NUREG-0297. On May 15, 1981 Westinghouse requested via Reference 3 that changes be incorporated in its ECCS evaluation models.'

The primary change being made was to implement the cladding  ;

swelling and rupture medals contained in NUREG-0630.

The NRC approved 1 the changes in Reference 3 on December 1, 1981,  !

noting that the model "is in compliance with 10 CFR 50 for all

PWR's currently being supplied with Westinghou'ne manufactured

{ Zircaloy clad fuel." The changes in Reference 3 pertinent to the NUREG-0297-approved UMI model were then in.plemented to create a revised UHI Evaluation Model. Perfect and imperfect mixing l analyses were performed in 1982-83 for Sequoyah Units 1 and 2 utilizing the UHI Evaluation Model computer codes which contain the NUREG-0630 fuel and other models as approved in Reference 3.

Note that Reference 2 still constitutes the UHI Evaluation Model, except for the minor changes instituted per Reference 3.

) The 1982-83 Sequoyah UNI analysis effort perfect mixing cases werc 4

pertorned to augment the perfect mixing cases analyzed initially for the sequoyah FSAR. That 1978 analysis parforried in accordance With Reference ?

showed the limiting case with perfect mixing of UHI water assumed in the vassol upper head was the Co*0.6 DECLGt its calculated peak ,

clad temperature (PCT) is 21110 F at an Fq of 2.32 ,

for a UHI delivered water volume of 1053 cu. ft. The perfect mixing cases performad in conformance With Reference 3 in 1982-83 l Here less limiting than the earlier result; tho 1978 limiting PCT value of 21110F bout.ds the perfect mixing case results obtained using the revised UHI Evoluntion Model.

result has continued as The 1970 ncforenca 2 the reference case for sequoyah perfoot nixing caso performance evaluations, and it remains conservative relative to the Reference 3 UHI Evaluation Model results. With a Technical Specification Fq of 2.237 in force, 1130.5 cu. ft. in a valid maximum delivered water volume for the Sequoyah UHI systemt the c,alculated PCT of the limiting C =0.6 D DECLC perfect mixing case at 1130.5 cu. ft. UHI water delivery is 2163 0F.

page Al

y . . _ _ _ _ . ._ __ . _ _ . _ _ . - . _ _

m-,., ,,_,,,,- ,,,,, __, ; , y ny_ -

" Tho CD =0.s and Coa 0.6 DECIA itportcet cixing cacco from tho

,. ~ .1982-83 104 sGTP onalycio havo impact. of reducing b3cn rCvicw

d to cocG00 the PCT The calculated PCTs the delivered UHI water volume te $50 cu. ft. I for the C *0.8 and CD =0.6 DECI4 imperfect i mixing cases, which utilize theD Reference 3 version of the UHI l

Evaluation Mode and are presented in Reference 1, equal 2111 F I

and 2113'F, respectively.

Reducing the UNI water delivery in an imperfect mixing case 3

will reduce the cooling of the fuel as the hyper head drains during blowdown.

j During the core reflood phase, this better fuel will cause the expulsion of more injection water i as entrained liquid, producing a degraded flooding rate. Existing j Sequoyah imperfect mixing cases  ;

define the penalty in core fuel i heatup associated with decreasing UNI delivery to 850 cu. ft.

Expressed as  !

a flooding rate penalty, reducing UHI water delivery i

to 850 cu. ft.

reduces core inlet velocity by 74 for the licensing 4

basis iriparteet mixing cases.

'l The impact of degraded floodi. g rates upon hot rod calculated PCT

han been detemined by WREFLOOD/LOCTA sensitivity runs for each

{ licensing basis imperfect mixing case.

Expressed as an imperfect Mixing case PCT sensitivity relationship, one cu. ft  ;

decrease in

[ UHI water delivery results in approximately a l'F increase in

[ calculated PCT for the limiting Cp=0.6 DECLG casa; the PCT l sensitivity is even less severe for the C =0.8 p DECLG case. The i 10% SGTp licensing basis imperfect mixing cases are acceptable at

{ an 850 cu. ft. daliveed UNI water volume because the degraded j

reflood penalty only increases calculated PCT as follows:  !

i t j

Cp=0.8 DECI4 PCT =21510F l Cp=0.6 DECLG PCT =21660F

~

i

It may further be nota that a Cp =0.4 DECIA imperfect mixing case was perfornid in 1982 using the UHI Evaluation Model as i

) modified per Reference 3. On an equivalent input basis, the '

j calculated PCT for the C)=0.4 DECLG imperfect mixing case is '

over 200 degrees less limiting than the above cases.

Thorofore, consideration of the p  ;

i C =0.6 and 0.5 DECLG cas..es is sufficient in i this ase.essment.

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' An indep:nd:nt caf0ty cycluatien p;rform d for S qucych during

. , *

• N vcmb r, 1986 (R3ferenc0 4 OttCchtd) consid r0d tho impact of a possible but unlikely scenario of guide tube flexura failures.

The PCT penalties imposed upon perfect and imperfect roixing cases under this scenario are 0*F and 20 0F, respectively. This highly improbable event delivery transient, and it affects the initial portion of the UHI that the UHI sys' tem is no longer has any effect by the time isolated. Therefore its magnitude of impact is unaffected by a change in the UHI delivered water volumo to 850 cu. ft. The not PCT for the limiting imperfect mixing Co =0.6 DECL4 case including this scenario becomes 0

2166 F + 200F = 21860F when postulated guide tube flexure failures are considered.

A furtner phenomenon which could impact the sequoyah Plant calculated PCT values in the is filling of the instrumentation thimbles core during the reflood phase of a large break LOCA event.

The thimble volume which treated in the sequcyah large must be filled has not been explicitly break LOCA analyses. Westinghouse had initially assumed that the thimblo plugging devices would be sufficiently tight to prevent the ingress of water into thimbles during re f) cod. However, it was later identified to the PRC Stuff that the plug clearancos waro sufficiently largo and the flows were sufficiently low during reflood to allow the thimbles to fill with water even with plugs installed.

The impact which thimble filling will for sequoyah, exert and on the calculated PCT values has been assessed the perfect and imperfect the appropriate PCT penalties to be imposed on mixing cases are established as 0 00 and 12 F.

The imperfect mixing penalty equals the maximum value

previously identiflod by Westinghouse in WCAP-9561-P-A, Addondur 3 i because its PCT occurs during the traditional cora reflood phase.

The net calculated PCT for the limiting C =0 6 DECLC imperfect mixing case becomes D l

0 2186 F + 120F = 21980F

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... . i and compliance with the regulatory limit is maintained. The l perfect mixing case calculated PCT occurs at the very inception of the core reflood phase, so it is not subject to a thimble filling penalty. '

Both the perfect and imperfect mixing cases of the sequoyah large break loCA analysis remain in compliance with 10CFR50.46 if the UMI water delivered volume is set within the bounds 850 - 1130.5 cu. ft., with calculated PCT values of 21630 F anft 21980F respectively.

CMALL BREAR loCA The Current FSAR small break ICCA analysis for Sequoyah Units 1 and 2, wcs performed using the NRC-approved UNI Small Break 14CA ECCS Evaluation Model (Reference 2), which resulted in the most limiting PCT of 1484'F for a 8 inch equivalent diameter break (Reference 1). A cafety evaluation which considered the effect of charging /8I pump flow chortfall increased this result by 200'F, resulting in an overall licensing basis PCT of 1586'F.

Wostinghouse Letter NS-TMA-2147, dated November 2, 1979, responded to NRC concerns related to the fuel rod models used in the Westinghouse ICCS evalu*ation models, subsequently, in December,1979 letter j

NS-TNA-2174 identified a metho2 ology by which the impact of NUREG-0630 fuel rod models on existing analyses could be determined. This opproach was employed to justify continued operation of Westinghouse

! plante until MUREG-0630 fuel rod models were implemented into the l W stinghouse cosputer codes.

Note that in applying this *ethodology l

Wootinghouss was only required by the NRC Staff to examine the limiting cace break; in all plant analyses this was a large break IOCA case.

N0vertheless, it can be concluded that the Reference 2 model results remain applicable for sequoyah. As indicated above, the not licensing bcois calculated FCT is icss*F for the eight-inch equivalent diameter cold leg break.

i Fuel red burst le predicted to occur in not only the cight-inch break but also in the six-inch break case analyzed for sequoyah using Reference 2 methods.

Because rod burst has been predicted to occur in the analysis of record, applying the NUREG-0630 fuol red models would not produce a major change in the reported results.

since the magnitude of the change is minor and copious PCT nargin exists, the scall break LOCA remains non-limiting for sequoyah, and cocpliance with 10CFF50 is assured.

G

.ne .c. ne - ..- . ,. ..e .n., . ..- . . . .

,7 o ,REFEREiiCES

1. Sequoyah Station FSAR - Updated 6/16/86, Amendment 3.

2. WCAP-8479 Revision 2 (Proprietary), WCAP-8480 Revialon 2 (Non-Proprietary), Young, M. Y. at, al., "Westinghouse Emergency Core Cooling system Evaluation Model Application to Plants Equipped with Upper Head Injection", January, 1975.

3. WCAP-9220-P-A (Proprietary), WCAP-9221 (Non-Propriettry),

Eicheldinger, C., "Westinghouse ECCS Evaluation Model - 1981 version", Revision 1, 1981.

4. Westinghouse SECL-86-461, "Impact of Guide Tube Flexure Cracking on ECCS Performance, Sequoyah Units 1 and 2.

5. WCAP-9561-P-A, Addendum 3, Young, M. Y., "Addendum to:

BART-Alt a Cocputer Code for the Best Estimate Analysis of Reflood Transients (Special Report: Thimble Modeling in Westinghouse ECCS Evaluation Model), 1986.

6. NUREG-0297, "Safety Evaluation Report on Wantinghouse Electric Company ECCS Evaluation Model for Plants Equipped with Upper Head Injection," April 1978.

7. NS-TMA-2147, Letter from T. M. Anderson, Westinghouse to D.

G. Eisenhut, NRC, dated November 2, 1979.

8. NS-TMA-2174, Letter from .T. M. Anderson, Westinghouse to D.

G. Eisenhut, NRC, dated December 7, 1979.

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SUPPL.EMENTARY INFORMATION I

The reference documents the possib8.11ty of guide tube flexure failure at sequoyah.

In the extressly unlikely event that AIL four flexures of 1

one particular 15X15 guide tube containing an insert were to fail, the i insert aislarge during calculated break 14CA to liftevent. off the housing plate upon which it resides It may either fall directly downward back into piece mz twist and become suspended on the broken flexure stubs er be expelled completely from the guide tube assembly, increasing the flow area between the upper head and upper plenum regions. Guide tubes and/or hollow support columns provide flow communication from the core j outlet to the upper head for 185 of the 193 sequoyah fuel assemblies. The housing plate in only millisecondst no espect of the large br transient can be affected in the slightest during such a trivial length of time.

calculated Thelarge locationbreak of IccA the insert performancewhen itisfalls at allwill determine if the affected. If it falls i

back into place, there is no impacts other identifiable configurations all

involve an increase in flow communication with the upper head region. The j greatest impact will occur if the insert is missing completely from the

gui'de tube in question.' The scenario in which a 15X15 guide tube insert i et sequoyah ovents disappears is evaluated below. at the inception of the postulated large break LOCA

! As documented in the sequoyah FSAR, cases modeling perfect and -

imperfect be analyzed. mixing of UNI water in the reactor vessel upper head must both ossumption will be limiting for Sequoyah with the UNI delivered waterL ,

volume limits being adopted for the next cycle of plant operation.

i perfect nixing cases are characterized by an extended interval during blevdown during which subcooled imI water in the upper head is heated to

. the guide

.the boiling point by steam flowing in from the core outlet plenum through tubec l clad temperature (PCT) e Dt. ring this reheat period core flow is low, and peak l

increases monotonically., The postulated loss of a guide tube insert will enhance steam flow into the upper head and reduce 3

!' the duration drain sooner. ofSince the reheat period, allowing the upper head to begin to i

! this is accomplished with no loss of : support colu:tn -

l flow capability, the drain flow from the upper head will cool the core as j -

previously analyzed.* The not effect of the loss of a 15X15 guide tube i

insert is a reduction in calculated PCT for the limiting perfect mixing ossumption.

< Imperfect sixing cases arsi characterited by early flashing of the "

j fluid in the upper head and un early upper head draint the top of the i

guide of tubesbreak the large is uncove, LOCA.red The approximately 10-15 seconds after the inception  !

impact on the calculated ECCS performance of a missing 15X15 insert should be small in magnitude for the imperfect

• Diving such a assumption short time during because the blowdown. liquid flow through the guide tubes exists for 0

cases exhibit more than 80 F margin in calculated PCT to the 2200 7The 0 sequoyah F regulatory limit.

I Inasauch as p e impact of a missing guide tube insert i L

l with the regulatory limitthan 10 estinated to be less is assured.20 F in imperfect mixing cases, compliance Therefore, both the perfect and i

inperfect. aixing cases of the sequoyah large break IcCA retain acceptable i

Eccs performance analysis results for the highly unlikely scenario of the co:plete ejection of a 15X15 guide tube insert.

l i

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'"--'*TJP9M-'t9=--'erye ww- ,w wmee-r---y-wism*m >meaw e w^mwy-

• e*--- - " - ' ' -9"-" " " - " ' " ' " - " " '

,c*

ENCLOSURE 3 PROPOSED TECHNICAL SPECIFICATION CHANGE SEQUOYAH NUCLEAR PLANT UNIT 1 9

DOCKET NO. 50-327 (TVA-SQN-TS-88-28)

DETERMINATION OF NO SIGNIFICANT HAZARDS CONSIDERATIONS 1

c ~ .

ENCLOSURE 3 1 Significant Hazards Evaluation TVA has evaluated the proposed technical specification change and has determined that it does not represent a significant hazards ec4.ileration based on criteria established in 10 CFR 50.92(c). Operation of SQN in accordance with the proposed amendment will nott -

(1) Involve a significant increase in the probability or consequences of an accident previously evaluated. Fo(s) is defined as the maximum local heat flux on the surface of a fuel rod divided by the core average heat finx. iq(s) is used to limit the nagnitude of hot spots and is used as a bounding input for accident analyses. Fq(z) is not postulated as being the initiating event for any accident scenario. Therefore, the proposed change does not affect the probability of any accident previously evaluated. The proposed reduction in Fq(z ) frem 2.237 to 2.15 is conservative in nature, in that it results in reduced PCTs during a postulated accident. The F0 (s) reduction serves as an operational restriction to ensure that PCTs remain below the 10 CFR 50.46 limit of 2.200 degrees F. Because

, of the reduction in calculated PCT, the proposed change will not increase the consequences of a previously evaluated accident.

l (2) Create the possibility of a new or different kind of accident from any previously analyzed. As stated above. Fq(s) is not assumed to be the initiating event for any accident scenario. The proposed change to Fq(s) provides additional PCT margin to ensure that the

' 2,200 degrees F limit is not exceeded. The presence of additional margin will not create the possibility of a new or different kind of i accident.

(3) Involve a significant reduction in a margin of safety. The proposed reduction in Fq(z) is conservative in nature as it lowers the calculated PCT for the limiting LOCA analysis case. As calculated by i M, the proposed reduction in Fq/z) from 2.237 to 2.15 lowers the calculated PCT by 87 degrees F for the limiting imperfect mixing case

, and by 96 degrees F lar the limiting perfect mixing case. These

! reductions, ecmbined with PCT margin obtained by administrative 1y 4

limiting steam generator tube plugging to 5 percent, result in calculated PCTs of 2.089 degrees F for the limiting imperfect mixing i case and 2.06/ degrees F for the limiting perfect mixing case.

I Beceuse the calculated PCT remains below the 2,200 degrees F limit of

10 CFR 50.46, there is no reduction in the margin of safety to

! cladding failure, and additional margin is being added.

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