ML20082H025

Application for Amend to License NPF-29,removing 4.16 Kv Bus Undervoltage (balance-of-plant Load Shed) Actuation Instrumentation Tech Spec Requirements

ML20082H025
Person / Time
Site:	Grand Gulf
Issue date:	08/15/1991
From:	Cottle W ENTERGY OPERATIONS, INC.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
Shared Package
ML20082H027	List: ML20082H025 ML20082H029
References
GNRO-91-00146, GNRO-91-146, NUDOCS 9108220246
Download: ML20082H025 (9)

Text

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ES Ent:rgy f"'= y="a"* '"'

Operations -

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J W. T. Cottle August 15, 1991 O.S. Nuclear Regulatory Commission Hall Station PI-137 Washington, D.C. 20555 Attent(on: Document Control Desk

Subject:

Grand Gulf Nuclear Statlon Unit 1 Docket No. 50-416 License No. NPF-29 P.emoval of 4.16 kV Bus Un6 rvoltage (BOP Lond Shed)

Actuat ion Instrumentation Technical Specification Requirements Proposed Amendment to the Operating License (PC0h-91/20)

GNRO-91/00146 l'

Gentlemen:

Entergy Operations, Inc. is submit. ting by this lett-r a proposed amendment to the Grand Gulf Nuclear Station Opernin.- License. The proposed aroendment requests changes to fechnical Specification Table 3.3.3-1, " Emergency Core Cooling Syttom Actuation Instrumentation,"

Table 3.3.3-2, " Emergency Core Cooling System Act.uation Instrumentation E 'ints," and Table 4.3.3.1-1, " Emergency Core Cooling System Actuation Ins umentation Surveillance Reluirements."

The proposed change would remove requirement > for-tne Balance of ilant

-(DOP) Land Shedding feature of the Land Shed and Sequencing System. This feature uns a causal factor in two automatic reactor trip t.ransients init iated by non-valid DOP load shed r,!gnals. Due to the severity of the transients (i.e., multiple snfety system acturitions), the prohnbility of recurrence, nnd absence of a safety basis for thn BOP Load Shedding feature, we request that. this proposed amendment receive expedited review and response. Upon approval, Entergy Operations intends to nroceed with disabli .g the BOP Load Shedding feature in order to prevent similat

-transients in the future.

In accordance with the provinionn of 10CFR50.4, .the signed original of the requested amnndment is enclosed. Attachment 2 provides the discussion and justification to support the requested amendment. This amendment request has been reviewed and accepted by the Plant Safety Paview Committee and the Safety Review Committee.

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August 15, 1991 GNRO-91/00146 Page 2 of 3 Based on the guidelines given in 10CFR50.92, Entergy Operations has 4

concludnd that. thir. proposed amondment involves no significant hazards considerations.

Yours truly,

} w ro*ent"~

WTC/BSF/ams attachments: 1. Affirmation per 10CFR50.30

, 2. GGNS PCOL-91/20 Mr. D. C. liintz (w/a) cc:

4 Mr. J. I.. Mathis (w/a)

Mr. R. B. McGehen (w/a)

, Mr. N. S. Reynolds (w/a)

Mr.11. I.. Thomas (w/o)

Mr. F. W. Titus (w/a)

Mr. Stewart D. Ebneter (w/a)

Regional Administrator

, U.S. Nuclear Regulatory. Commission Region II 101 Mariotta St...N.W., Suito 2900 Atlanta, Georgia 30323 Mr. L.1.. Kintner, Project Manager (w/a)

Office of Nuc1 car Reactor Regulation U.S. Nuclear Regulatory Commission Mail Stop 11D21 Washington, D.C. 20555 Dr. Alton B. Cobb (w/a)

Stato lloalth Of ficer State Board of floalt h P.O. Ilox 1700 4

Jackson, Mississippi 39205 G9108081/SNLICFLR - 2

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l-11EPORE Tile UNITED STATES NUCI. EAR REGill.ATORY COMMISSION I.ICENSE NO. N PF- 29 DOCKET NO. 50-416 IN Tile MATTER OF MISSISSIPDI POWER & I,1CIIT COMPANY and SYSTEM ENERGY RESOURCES, INC.

and SOUTil MISSISSIPPJ El.ECTRIC l'0WER ASSOCI ATION and ENTERGY OPERATIONS, INC.

AFFIkMATIDS 1, W. T. Cottle, botng duly sworn, stato that I am Vice Prnsident, Operations GGNS of Entorgy Operations, Inc.; that on behalf of Entergy ,

Operations. Inc., System Energy Rnsourcos, Inc., and South Mississippi Electric Pownr Assocle. tion I am authorized by Entorgy Operations, Inc. to sign and filn with thn Nuclear Regulatory Cammission, this application for amnndment of thn Operating 1,lennso of the Grand Gulf Nuclear Station; that I-signnd this application ari Vice Prnsident, Operations GGNS of Ent ergy Operations, Inc.; and that thn statements mado and the matters set forth thornin are trun and correct to thn bnst of my knowindgn, informat ion and bolinf.

My - /' b r==

W. T. Cottle STATE OF MISSISSIPPI COUNTY OF CI.AIBORNE SUBSCRIBED AND SWORN f0 bnfore me, a Notary Public, in and for the County and State abovn named, this \h day of by d , 1991,

( SEAI.)

d h edYb1; ara \D O M Notnry ibi My commission expires:

yy ccmmhdan Drhes l# L M G9108081/SNLICFI.R - 4

Attachment 2 to GNRO-91/00146 PROPOSED CHANGE TO THE 0PERATING LICENSE-REMOVAL OF 4,16 KV BUS UNDERVOLTAGE (BOP LOAD SHED) ACTUATION INSTRUMENTATION TECHNICAL SPECIFICATION REQUIREMENTS

-(GGNS PCOL-91/20) 4 4

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Attachmnnt 2 to GNRO-91/00146 Page 1 of 5 l

A. SUBJECT

1. Removal of 4.16 kV Bon Undervoltage Balance of plant (DOp) Load Shedding Actuation Instruunntation Technical Specification Requirements.

2. The affected Technical Specifications are:

a. Table 3.3.3-1 page 3/4 3-29,

b. Tahlo 3.3.3-2 page 3/4 3-32, and

c. Table 4.3.3.1 pago 3/4 3-35a.

B. DISCUSSION

1. Thn proposed amendment request.s changns to Technical Specification Table 3.3.3-1, " Emergency Core Cooling System Actuation Instrumentation," Table 3.3.3-2, " Emergency Core Cooling System Actuat. ion Instrumentation Sotpoints," and Tabic 4.3.3.1-1, " Emergency Core Cooling dyntem actuatloc Instrumentation Surveillanco Requirements." The proposed change is described below.

2. The requested revision removes the requirementr, contained _in Iter. D.1.b of each of the a f fected tahins. This revision removes the operability, setpoints, and survn111ance requirements for the 4.16 kV Bus Undervaltago DOP Load Shedding circuits.

3. The affected Technical Specification pages are attached and marked up to reflect the proposed changes.

C. JUSTIFICATION / BACKGROUND' The 4.16 kV Bus Undervoltage BOP Load Shedding circuits are part of l

t he Load Shndit 3 and Sequencing . System (LS : rystem). Thi basic function of the 1.SS System is to disconnect (shed) and connect, automatically in sequence, loads on the Class IE buses. The hSS=

accomplishes this without degrading the -integrity, voltage, or frequency of thn Class IE pownr supply.

LSS System Safety Related Functions As discussed;in References 1 and'2, the LSS System depends on two means of detncting unacceptabic voltage levels in the Class 1E electrical system. These two methods are detecting the completo loss of voltage (primary method) or a sustained,- degraded voltage condition (secondary method) on a Class 1E 4.16 kV hus.

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Attachment 2 t o CNRO-91/00146

' age 2 of 5 One set of bistables monitor voltage at the 4.16 kV Class IE bus of its safety division. These bistablos are the primary method for detecting unacceptable voltage levels. A measured nominal voltage of less than 70 percent for 0.5 seconds indicates unacceptable degradation (completo loss of voltago) of the preferred (offsite) source powering the bus. The LSS then dt. connects the Class 1E niectrical system from the offsite source and sequences the loads onto the orsite Class lE source.

A second set of bistables act upon observing a nor.inal bus voltage between 70 porcent and 90 percent for 9 seconds when the bus is powered by the of fsite sourco. 7 %se histables provido the secondary method of detecting unacceptable voltage levels in the Class lE olectrical system. This condition is indicative of a severe degradation of the entirn grid since automatic relaying on the network would normally restore nominal voltage in much less than 9 seconds if tho transmission system were manageable. The LSS then disconnects the Class 1E niectrical system from the offsite souren and sequences the loads onto the onsite Class IE source.

These two methods provide the basis for the bounding accident analyses.

LSS System BOP Load Shedding Feature As discussed in Reference 1, a third set of hist 6bles measu o voltage on the Class IE buses. These bistables are actuated by an observed bus voltage of 80 percent, or less, of nominal. Upon receipt of both a Loss of Coolant Accident-(LOCA) signal and the 80 percent bus voltage signal, the LSS then disconnects (sheds) the BOP 6.9 kV and 4.16 kV buses from the offsite power source. Tho' BOP Load Shedding feature is inhibited if the second level of undervoltage protection provided by the LSS System has already act'iated. The operation of the BOP Load Shedding feature does not af fect the, operation of the Class 1E onsite clectrical power system. The successful operation of the BOP Load Shedding capability is not a prerequisite for any safety function.

This BOP Load Shedding capability was designed to offer a possible improvement in the voltago profile at the Class -1?E electrical buses

-under extreme system operating conditions. These operating conditions includa minimum grid voltage during -full power operation of both Units 1 and 2 with one service transformer out of service followed by a LOCA on one unit. This voltage improvement was desired to optimize Class 1E bus voltage when offsite power is available cluring the Design Basis Accident (DIIA).

The potential for. the extreme system operating condition. of minimum grid voltage during full-power operation of both' units no longer.

exists due to the cancellation of Unit 2. . As a reeult, tha potential for voi tage improvement is outweighed by the potential for trarcilents resulting from the non-valid operation of this feature. The successful operation of this feature is not credited in.the system voltage calculations for Unit 1.

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Attachment 2 to GNRO-91/00146 Pago 3 of 5 Summary Deletion of the .hnical Specification requirements on the operability, setpoints, and testing of the BOP 1.oad Shedding capability is rnquested. This will allow for the fut uro removal of this feature of the LSS Syntem. Either this capability is not ,

required or its removal would rnsult in a nnt benefit to safety for the following reasons:

1. The potential for the extremo system operating r.ondition of minimum grid voltage during full-power operation of both units no lons,nr oxista due to the canenllat ion of Unit. 2.

2. Tho successful operation of this featuro is not credited in the system voltagn calculatious for Unit 1.

3. The successful operat.fon of this featurn is not a prorcquisite for any safety function including the proper operation of the Class lE elect.rical system. Thereforn, t.ho equipment associ9tod with the performance of this is non-safety related.

.4. The B0p Load Shedding circulty resulted'in non-valid sh6dding of the BOP loads on 09/16/90 and-07/28/91.- The shedding of-the B0p loads resulted in reactor trips (via turbine trips) and subsequert challenges to safety systems. Conroctivn actions taken prevent recurrence of these specific events. Ilownver, removal of-~this feature would provent recurrence of this trancient resulting from any event causing this featurn's--

non-valid operat.fon.

In order to segregate. the non-safety related equipment f rom thn-safety related LSS Systnm equipment, the LSS do ign 'Is modular. This allows for casy retroval of the BOP Load Shodding feature whilo assuring thorn is no adverso affect on the LSS Systora safety related functions.

l D. NO SIGNIFICANT IIAZARDS_ CONSIDERATIONS-

1. Entergy Operattons, Inc.1s- proposing the delotion of the requirement.n for t.be 4.16 kV Bun Undervol Lago 110P Load Shedding feature from the Technical Specificat.fons and subsequent removal of this featurn f rom the LSS System.

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2. Thn Commiss!on has provided standaros for.dotermining whethor a-no significatt nazards consideration exists as stated in 10CFR50.92(c).- A proposed amendment to an operating licenso involves no algnificant hazards' consideration if operation of

=the facility-in accordance with-the proposed amondment~ would not: -(1) InvcIve a significant increase in the probability or.

consequencen of an accident previously evaluatod; or (2):creato the possibility of a new or dif ferent kind of accident. from any accident previously evaluated; or (3) 17volve a significant~  !

reduction in a margin of safety.

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Attachment 2 to GNRO-91/00146 page 4 of 5

3. Entergy Operations has ovaluated t he no significant hazards considerations in its request for a license amendment, in accordnnce with 10CPR50.91(a), Entergy Operatious is providing tho analysis of the proposed amendment against. the three-standards .In 10CFREO.92:

a. No significant increase in the probability or consequences of an accident previously evaluated results from this chango.

(1) lon successful operat Jon of this feature is not assumed to prevent any accident. The potentini for the extremo system operating condition, for which this 4 feat.ure provided the greatest benefit, no longer exists due to tae cancellation of Unit 2.

Consnquently, the probability of occurrence of a_DBA LOCA with degraded grid conditions resulting in a concurrent Loss of Of fsito Power (LOP) could not. be significant ly af fected by the disabling of t.his <

i featuro. As a-result, the removal of the requirements (and thn removal of the font. urn) will not i significantly increase the probability of an accident.

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(2) The success ful operation of th.is function is not -a-

proroquisito for any safety function including tho-proper operation of the Class 1E: electrical system.-- l 1

As-a result, the removal of thn' requirements (and tho

- removal of the feature) will.not increase tho -

consequences of: an accident.

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, (3) Thornfore,-tho-probability or. consequences of previously analyzed accidents are not; increased.

b. The chango would not creato- the possibility of a new or '

i dif forent kind of accident - from any previously ' analyzed.-

4 (1) Tho - requested change wilI not cdd any plant- equipment,

' introduce any now modos ~ of pla,t operation,lorj add any -

new testing configurations.-

(2) Curront accident analysis . boun'd' degraded ' voltage .

conditions:affected by the removal of L this fnature.

(3) Thorofore, ' operating thn plant with_ the.proposet change will notferente the possibility of,s new or-

- dif forent: kind of accident; from 'any accident previously evaluated.

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Attachment 2 to GNRO-91/00146-page 5 of 5

c. This change would not involve a significant reduction in the margin of safety.

(1) The proposed change does not affect the methodology used in the offsite dose analysis nor the acceptance criteria associated with any accident analysis.

(2) The successful operation of this feature is not a prerequisite for any safety function and is not taken-credit for in the system voltage calculations for Unit 1.

(3) The non-inlid operation of this feature has resulted in challenges to safety systems at, the result of two turbino trips and associrted ' reactor trips. Removal of this feature will remove the possibility of this cause of unnecessary challenges to safety systems.

(4) Removal of the Bop Load Shedding capability-will result in a-not benefit to safety.

4. Based on the above evaluation, operation in accordance with the proposed amendment involves no significant hazards considerations.

E. REFERENCES

1. Grand Gulf Nuclear Station _ Final Safety Analysis yepoyte Updated-through Amendment 5, section 8.3.1.1.~3.

2. NUREG-0831, Safety Evaluation Report Related to-th9 Operation of Grand Gulf Nuclear Station, U.ij ts 11 and- 2, and Supplemen't v.

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