ML20082T484

Application for Amend to License NPF-29,revising Tech Spec Table 3.3.4.1-2 to Increase ATWS Recirculation Pump Trip Sys Instrumentation Setpoints to Alleviate Operational Problems Associated W/Reactor Protection Sys Actuations

ML20082T484
Person / Time
Site:	Grand Gulf
Issue date:	09/11/1991
From:	Cottle W ENTERGY OPERATIONS, INC.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
Shared Package
ML20082T488	List: ML20082T484 ML20082T489
References
GNRO-91-00136, GNRO-91-136, NUDOCS 9109190005
Download: ML20082T484 (10)

Text

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m RQ Eetergy Operauona,Inc, c== ENTERGY W. T. C ottis-September 11. 1991 U.S. Nucient Reguint ory Commisdon fin il Stat ion Pl-137 Washingt on, D.C. 20 % 5 Atieut lots: Dot oment. Cont t ol Doni S ubj ec t. ' U t atul Gill f Nuc l eai r S t a t ict.

Unit !

Doc k e t No. '0-416 ,

1,1cenne No. NPF-29 Revised Trip Setpoint f or ATWS Recirullat ton pump Trip on Renctor Pressure lligh Pit, posed Amendment to t he Opet at ing 1,1 cense (PC0h-91/18)

GNPD-91/00136 Gontlemen:

Ent ergy Opet ntions, Inc. has developed a proposed change to t hn Operntjug I.J a.n s e to t evise the Grand Gulf Nucient Station (GGNS) Technical Speciffentions (TS). The chango would increnne t he Ant icipnt ad 'I r nnn ient W i t hout Scram (ATWS) decirculat ion rump Trip (RPT) System Inst rumentatloa Setpoints in Table 3.1.4.1-2 for the Peactor h ensure liigh Trip runct lon.

This revision in bning roqunnled in oides to help nllevint n operat ionn) prohloms nssociated with unnecessnry RPf net ont ions during in n-ATWS pinot transients. it niso ful fills a previons commit ment. to t he Commission to evninnin intning the picsnuro notpoint nn a po.entfoi solutlon to such problems IAECM-9n/0026).

The set point. va loen in thn proposed revinlot are dortvol ftom pinnt-spec i fic ATWh ana lyses recent ly pnr formed f or GGNS. *l h e current pressurn ne t point s n e bnned to a large degree on generic ItWR nonlyses contnining overly conservative limit at inns resul'ing in lower volons. Thn GGNR speci fic annlyses no lon;,er inly on sur.h generic eva lunt ions and t hernforn al low thn set point s to be inised to approximat ely t hn values originni ty licens ed for Grand Gul f.

In accordnute with the provisions of 10CFR50.4, the sigund or.lginni of the requested amendment is enclosed. At t.nchment 2 provides the technieni justi fiention nnd dincussion t.o suppor t thn requested amendment. This ameedmont has been rnvit we'l and accept ed by the Plnut Sofety Review Committee nial t he Sa fety Poview Commit t ee.

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Septetnber 11. 1991 CNRO-91/00136 Page 2 of 3 Boswl on the guidelinen picsonted in 10CI'R50.92, l'.ntergy Operntions has concluded thnt t his ptoposed aniemiment involves no rigniftenut horsrds considerations.

It is our desire to perform the adjustmont of the ATWS kPr high pressure trip setpotut during t he next refueling outage. Accordingly, we arn request ing nppt ovn t by March 1,1992, so t hat t he tiernsunry arrangements may be trimplet ed.

Yours t ruly, Ark WTC/KI,W/mtc nttnchments: 1. Affirmation per 10C1'R 50. 3u

2. GGNS PCOL-91/la cc: Mr. D. C. Illntz (w/n)

Mr. J. L. Mathln (w/n)

Mr. R. B. McGohne (w/n)

Mr. N. S. Reynolds (w/n)

Mr. II. L. Thomas (w/o)

Mr. Stewart D. F.bneter (w/a)

Regional Adminir.trator U.S. Nuclent Regulatory Commission Reglon !I 101 Marint in St . , N.W. , Suite 2900 Atinntn, Georgin 30123 Mr. P. W. O'Connor, Project linnagnr (w/n)

Office of Nuclear Reactor Regulntion U.S. Nuclear Regulatory Commission Mn11 Stop 13113 Washington, D.C. 20555 Dr. Alton B. Cobb (w/n)

State llentth Of ficer State Board of lloalt h P.O. Box 1700 i Jnckson, Mississippi 39205 09107291/SNLICFlR - 2

ItEPOWE Tile UNITED STATES NUCt. EAR REGUI.ATORY COMMISSION LICENSE NO. NIT-29 DOCKET NO. 50-416 IN Tile MATTrR 0*/

MISSISSIPPI POWER 6 f.lGilT COMi'ANY and SYSTEM ENERGY RESOURCES, INC.

and SOUTil MISSISS1PPI EI.E('1RIC POWER ASS 00l AT10N and l'NTERGY OPERATIONS, ING.

6.FLLMhuot1

1. W. T. Cot tle, being duly sworn, state that I am Vice President, Operatlons GGNS of Entergy Operattons Inc.; that on bohn)f of Ent orgy Operatlons, Inc., System Energy. Resources, Inc., and South Hir.sissippt Electric Pownr Association I am authorized by Entergy Operations, Inc. to sign and file with the Nucinar Regulatory Commission, this application for amendment of the Operating License of thn Grand Gulf Nuc1 car Station;

-that.I signed this application as Vice President, Operations GCNS of Entergy Operations. Inc. ; and that the stat ementn mado and the mattern set forth therein are true and corrnet to the best of my knowindgn, Information and belinf.

, e-** f~~ C*2<-w ..

W. T. Cottle STATE OF HISSISSIPPI t:0VNTY OF Cl.A180RNE

' SUllSCRIllED AND RWORN .TO before me, a Notary Public, In agd for the County and Stato above named,~this- _ \\ ,_, day of h n%%\M.,_,,, 1991.

\-

( SEAT.)

ANem OwnMSg!n,_

Notary Publ My commission expires:

gJ f6cJt.dm Expbei My 1,199)

G9107291/SNLICPLR - 4

. . /,tt achment 2 to GNRO-91/00136 l

Page 1 of 6 A. SUIUECT

1. NPF-91/02 Revised Trip Set point for ATWS Mecircuint ton Pump Trip on Konctor Pressute liigh

2. Af fect ed Technical Specifient ions:

Table 3.3.4.1-2, "ATWS Recirculat ion Pump Trip Fystem Inst rument nt ton Set point s", it em 2. Wouctor Vessel h essure -

liigh Trip Sntpoint and Allownble Value, Page 3/4 3-39 B. DISCUSSION

1. The proposed change revit<cs Table 3.3.4.1-2 of t he Grand Gul f Nuc1cor Statinn (GGNS) Technlen) Spacificntions (TS). This Table specifies t he re<pii r ed set point s for the Ant i ipated Transient Without Sctnm (ATWS) Recirculation Pump Trip System lust rumentat ion. The proposed chnoge raises the Trip Setpoint and Allownble Valne for the Ronctor Vessel Piesnure - liigh Trip lunction.

2. The ATNS Just ruttentat ion is designed to initiate the Alternate Rod insertion (ARI) and Recirculation Pump Trip (RPT) functions a r. reqntred by 100FR50.62. 110th of these functions are actunted upon receipt of either n high renctor pressure vessel (RPV) stenm dome pressure or low (i.evel 2) reactor water level algun1. I,ogic is two out-of-two for either signal, hath functinns can also he initiated manually by tractor operators.

3. The ARl/RPT f unct lons are intended to mitigate the consequences of an ATWS event by providing alternate methods of reducing reactor power in the unlikely event that the Renctor Protection Syntrm (RPS) falls to do no as designed, ARI provides a separate logic path to cause control real insertion independent of RPS.

The purpose of the RPT port ion of the ATWS instrumentation is t.o cause the renctor recirculatjen pumpe to trip to zero speed, thus quickly reducing core flow. This in t urn result s in the crention of nddit ional moderator volds, thereby inserting negative renet tvity and decreasing, reactor power j;enernt lon. The signals ured to init' ate the ARl/RPT functions f1.c., high reactor pressure and/or low reactor water level) nre indicat ive of cont inued ennrgy generrit ion in t he ranctor vessel following a failure to atram.

4. The high react or pressure netpoint must be selected so that the ATWS event is mitigated without exceeding ATWS limits which protect the pinnt radiological release barriors. Interaction with the RPS scram setpoluts is niho considered. The ATWS pressure setpoint must initiate the necessary protective fontures at a point higher then the normni RP3 ncram pressure, but low enough t o prot ect t he fuel, vessel, and conte nment from demnge.

09107291/SNLICFLR - $

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. Attachment 2 t o GNRO-91/00136 page 2 of 6 4

S. Thero is also another important considerat ion t olative to establishing an optimal high vessni pressure ATWS setpoint.

During anticipated pressurir.ation transinnts idt.h scram, a spurious RPT may occur if the ATWH initiation la not not sufficiently above tho vessel prensuro expected to result from automatic bypass valve or safety-relief valvo (SRV) pressure control during such events. This in highly undesirable due to potential thermal st ratificat ion pinblems associated with reduced coolant mixing in the core once the recirculation pumps havn t ripped. Two such events have in fect occurred at GGNS in the past, resulting in cooldown rates in the vessel bottom head region in excess of the TS nilowed rato of 100"r/hr. These incidents can be further complicated by the innbility t o rn-estabilsh forced mixing due to thermal limitations preventing racirculation pump restart. Following the most recent incident, Entergy Operations, Inc. committed to evaluato a possible incronso in the A1WS ARl/RPT high pressurn antpoint in order to help avoid such recirculat inn pump t rips. This evaluntion is now complete.

6. As a result of the nbove evaluntfon, GGNS proposts to raise the Reactor Vessel Pressurn - liigh Trip Sntpoint and Allowable Vnlun in Table 3.3.4.1 2 (ltem 2) to 1126 psig and I?39 psig.

respectively. It is calculated thnt thoso values will result in an acceptable plant responsn to limiting /.TWS events at GCNS while providing a high prohnbility that spurious FPTs will be avoided during non-ATWS pressurir.ation transients.

The marked up TS page reflecting the proposed TS changes described above is includnd.

C. JUSTIFICATION

1. The current ATWS kenctor Pressure Vessel - liigh Trip Sotpoint is r,nt at 1095 psig. This is derived from an Upper Analytical himit (bAL) of 1113 psig as described by Entorgy Operations, Inc. In it s previous submit tal under AECt1-87/0152 npproved by the Commission an TS Amendment No. 41.

The 1113 psig value was based on preventing opening of more than two SRVu, given the current GGNS SRV relief setpoints and logic.

This ensures, that without initiation of ARl/RPT, the amount of stnam discharged into the suppression pool will bo 15%, or less, than the Nuclear Boller Rating (NDP). Based on generic analyses for simlint BWRo, thin 15% limit wns found to bn necessary in order to prevent extending 185"P supprossion pool temperat. urn GGNS12R89-012-00, September 13, 1989 GGNS LER 89-019-00, Janunry 29, 1990 GGNS 1.ER 90-001-00, February 9, 1990 (Note: This LER reports the excessivo cooldown event which occurred dur>ng the event described in /

hER fi9 -019-00, )

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~ L-i Attachtunt 2 to GNWO-91/00136 i

pago 3 of 6 r

, during transients inillated at less than rated power. 6 inis temperaturn, which in the containment temperaturn design limit, t was at t hat timo dntoimined to bo the limiting parameter for ATWS '

protisurization events at GGNS. P 'rformanco criteria also '

examined include primary sp lem pressurn, fuel latogrity l!mits. i 7

long torm shutdown cooling can. (lity, and radiological releaso ,

consequencen. Those parametern remained well within established limits for all events analyzmt.

2= Subsequent. to implomontation of N ndment No. 41, two high  ;

reactor vossol ptessure ATWS RpT at.tuations have occurred at GGNS during non-ATWS plant. transients (sco D.5 abovo). On both occasions, the resulting cessation of forced coolant mixing  ;

caused the cooldown rate in the vossal bottom head ragion to

• oxceed its TS limit. _In each event, vessel prennurn incenamed

--above the-1095 psig ATWS pressurn setpoint. The lown e ElW ,

rollot pressure is not at 1103 psig. Thus, an RpT may occur -i during anticipated pressurization events beforn normal pressurn i control _nechan(sms can operato, even though ATWS protective _

}

features are unnecessary. Since this has ptoven to be t undesirable, GGNS has evaluat ed the possibility of raising thw sotpoint to precludn such occurrencon in tho future.. An  ;

descrlhed bnlow, results of this analysis. show th9t. At in 4 allowabin to incrensa the ATWS prosauro sotpoint well abovn tho  !

1 lowest relic ( valvo lift pressurn while maintaining adequatn ATWS i

-pretection. 1 L

3. In ordor to dnterminn the amount. by which the setpoint could be rafaed, a new GGNS-specific ATWS analynis was performed.

• Contrary to the previous analysis.which was the bases for lowering the sotpoint to its current value, this analysis does i not rely on the generic limitation of 157. NPP, steam flow to the '!

suppre,nsion pool. Instead, detalled calculatinns of plant. j i performance _ are dono to determino an accept able inctnase in the  !

- pressure setpoint which still provides the nonded protection for .j ft11 ATWS parameters.

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4. Eventn specifically analyecd are the Turbine Trip. nnd the Main j Steam isolat. ion Valve (tiSIV) Closuro._ .All othnr 'cyonts which .  ;

havn boon analyzed in the past are dif ferent forms of these two j

- events and are t.hus bounded, wit h t ho exception 'of inadvertent ];

Opening _of a-Felief Valvo (10RV). _The slow progrnssion of tho 10RV ovent requires s.inual operator action, however, and in .I therefore not afincted by thn RPV high pressure setpoint. l

-l 1

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" _ Bor.ed on CE Report. NEDE-25055-1, " Study of ATWS Evenin for A1tornato i 3A Plants;0perating at Loss Than' Rated Pcwor"  !

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4 Attachnient 2 to GNRO-91/00136 Page 4 of 6 The analysna were performed for Entergy Operations, Inc. b:,

General Electric Company using the same tools -and methodology as in previous ATWR analyses for Grand Gulf. The REDY computer codo was used to assess the response of the nuclear boiler and the STEMP code was used to determine thn responso of the pressure i suppression pool. Those are the procedures and codes l historically used in performing generic BWR ATWS anulyses, as well. The analyses assumptions and results were reviewed and accepted by GGNS.

5. Evaluation of possiblo initial power / flow conditions has shown that any ATWS ovent initiated at thn GGNS Haximum Extended Operating Domain (MEOD) control rod line " knee point." of 100%

pownt/75% corn flow on the power / flow map results in a higher suppression pool temperaturo and RPV pressure than any other .,

point. As shown in Tabic 1, the analyzed ATWS events result in a i peak suppression pool temperature of less than 185'r and peak RPV l pressure, at the RPV's bottom, less than 1500 psig (Servico Level i U) even when occurring at this most severe point. This assumes >

that ARl/RPT is not initiated dun to a ATWS RPV high pressure setpoint being reached. ARl/RPT are assumed to be initiated by j the ATWS low water level setpoint for the MSIV closure event or j that the operator initiates AR1/RPT logic 10 minutes into thn l turbine trip event. Supprension pool cooling is initiated by the '

operator 10 minutes into both events. This assumption of operator action in 10 minutos is consistent w!th the plant design basis assumptiens and past analyses, as well as Emergency Operating Procedures. Other ATWS parameters not shown in Table 1 remain bounded by previous analyses. Thus, the analyzad events do not require ATWS.RPV high pressure initiation and thus are not limiting. ,

6. As a result of the above plant-specific analyses, GGNS proposos

, to raise the ATWS arf /RPT~ pressure setpoint. so that it will again be based on the 1150 psig Upper Analytical Limit originally licenned for GGNS.. Even though the new analyses show that there is no historically analyzed ATWS .,vont which requires automatic ARl/RPT init iation,. dun to RPV hfAh pressure, in.under 10 minutes  ;

in order to prevent exceeding ATWS paramotor limits, GGNS feels that it in prudent. and_appropriato to consnrvatively establish ,

this limit. The original ATWS analyson applicable to CGNS showed that the 1150 psig:UAL adequately protected against exceeding the 1500 psig vessel pressure limit. Those analyses were very conservative as evidenced by.the newer, plant-specific analyses ,

results which show that. automatic pressure actuation of ARI/RPT -

is in fact not necessary. Nevertheless, GGNS intends to apply-this limit in the determination of the TS Allowablo Valun (AV) <

and Trip Setpoint (TSP). '

-7. GGNS has calculated the proposed AV and TSP based on the UAh of 1150 psig. These are derived from the UAh by applying the appropriato instrument loop uncertainties and drift effects.

'They ara determined to be 1139 psig and 1126 psig, respectively.

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These dif fer slightly f rom the original values (1140 psig and 1125 psig) due to minor changes in the methods of calculating inst rument uncertainty since the original setpoint determinat ion.

The calculated TSP also provides a probability of over 955 that spurious RPT actuations on high RPV domo pressure will be avoided in tho- future if this revision is approved.

8. linsed on the above analysca and calculations, GGNS concludes that the proposed TS revision raising the Tablo 3.3.4.1-2 Reactor Vessel Pressure - liigh Allowablo value and Trip Sotpoint providos an acceptable lovel of plant saf ety consistent with thn requirements of 10CFR50.62 and plant spncific perfornanco criteria. These changes also increase the probability of avoiding unnecessary RPT ictuations and their associated negativo corsequeneca during non-ATWS events. Finally, this revision completes Entergy Operations, Inc. previous commitment to the ,

Commission to evaluate the feasibility and effects of the I proposed setpoint increase as a means of reducing the frequency  ;

of spurious RPTs. i 1

D. NO SIGNIFICANT llAZARDS CONSIDERATIONS Thn proposnd changes would raiso the ATWS Reactor Vessel Prensure -

High Allowable Value and Trip Set points in TS Table 3.3.4.1-2. This is required to help avoid unnecessary RPT initiations during non-ATWS plant transients and is acceptable based on analyses of GGNS ATWS ,

events.

The Commission has_provided standards for determining whether a no-significant hazards consideration exists as stated in 10CFR50.92(c).

, A proposed amendment to an operating license involvos no signfiicant hazards considerations .if operation of the facility in accordanco with the proposed amendment would not: (1) involve a significant increase in the probability or consequences of an accident previously ,

- evaluated; or (2) creata the possibility of a now or different kind of accident from any accident previously evaluated; or (3) involve a .i significant reduction in a margin of safety.  !

1.

No nignificant increase.in the probability or consequences of an accident previously evaluated results from this change.

a. . The increase in the ARl/RPT sotpoint does not affect the probability of an ATVS event occurring. The change is rotated only to the ability of these features to mitigato an ATWS ovent and not to event procursors. The only other type of FSAR: accident potentially impacted by this change is an inndvertent Recirculation Pump Trip (Section 15.3.1). The likelihood of this event occurring is actually lossened since raising the trip setpoint moves it farther above normal operating RPV pressure. Thus, the chances of a spurious RPT 1 during normal operation, as well as during other plant

, transients, is decreased. The abovo is also true of an inadvertent reactor scram via ARI, alt hough this evnnt is not separately considered in the FSAR sinco reactor scram is a designed safety feature.

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Attachment 2 to GNRO-91/00136 l l'agn 6 of 6 j t  ;

. . b. Raising thn ATWS setpoint also does not affect accident l consequences. The denign of the ARl/RPT logic and hardwaro f is unchanted. The system will still respond to adoquatoly

-mitigat a the consequences of an ATWS as described in the FSAR ,

and remains in full compliance with the intent of 10CFR50.62.  !

?.11 annlyzed ATWS events remain within established limiting j paramotors and there is no incronso in radiological relenne i due to raining t he setpoint. No other pinnt equipment nonded  ;

to mitigate the consequences of an accident is affected. I

c. Thus, thn probability or consequences of a previously analyzed accident are not significantly incronsed by thn proponnd chango,

2. The changn would not. croat o the possibility of a new or dif ferent kind of accident from any previously analyxod.

n.- rho proposed changa does not install any now plant equipment or introduce any new failure mechanisms not alrondy considered in UFSAR sainty annlyson. No now pinnt proceduros or oporating modes are created. Plant monitoring capability is unnf fected.

h. Thn ATWS-AR1/RPT system servos only as n backup to othnr existing safety-rointed systems. The incronsed notpoint ensures that the system is less likely-to produen spurious RPTs whiln continuing to fulfill its intended function.

Modification of the setpoint in no way crent.os the possibility of a malfunction of other pinnt equipment not alrondy considered in the PSAR.

c. Thorofore, there is no por,sibility'of a new or dif ferent kind of accident from any previously analyzed.

3. - This chango would not involvo n significant reduction in the margin of snicty.

n. Safety margin is catah11shed through the GGNS safety analysos as reflect ed in the Technical Specificat ions and linses. With the proposed change, thn ATWS-AR1/RPT continues to provido adequatn protnction for anticipat ed transients in which the normal scram paths infl, as stated in the linses for TS 3/4.3.4. Thn system continues to. ment the letter and intent of 10CFR50.62. As nhown by now and oxisting safnty g analyses, it n1so continues to meet natnblished ATWS-pnrformnnen critnrin limits for GGNS.

b.- With regnrd to the margin of snfoty associated with other plant. syntoms, this change has 1.0 impact except to increnso the margin of snfoty related to thoso systems for which L ARI/RPT serves as a backup,

c. Thus, this change will not involve n significant reduction in the margin of snfoty.

Based on the abovn ovaluntJon, F.ntorgy Operations. Inc. has concluded that operation in accordance with the proposed amendment involves no significant hazards considerations.

ls l G9107291/SNh1GFhR 10

Table 1 Summary of Results GGNS ATWS Analysis (Bounding events and conditionn)

Max. RPV Press. (psig)

ATWS F.vnnt Max. Sup. Pool Temp. (*F) (Time to Hax., Soc.)

_(Power /F_lpi . _Rimo t_o H.axa Soc.J _ _ -RPV Steam Domo RPV Bottom MSIV Closure -165.8 1160.0 1186.3

-(100%/75%) (676.0) (5.6) ('.9) ,

Turbine Trip" 175.7 1130.0 1153.3 -I (1001/75%) -(630.0) (1.8) (1.7)

-~1 Automatic initiation of ARI/RPT dun to RPV high press,ure in neglected.. ,

Instead ARl/RPT is Initjated on' low voman) water levnl approximately. -!

108 acconds into the event. Supprossion pool cooling is manually '!

Initiated at 600 seconds. t

Assumes . manual ARI/RPT logic niid suppression pool cooling initiat.lon at '

600 seconds, i;

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b N

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