ML20205R173

Application for Amend to License NPF-3,correcting Error in Tech Spec Section 3/4.3.2, Safety Sys Instrumentation & Section 3.3.2.1,Table 3.3-3, Safety Features Actuation Sys Instrumentation. Fee Paid

ML20205R173
Person / Time
Site:	Davis Besse
Issue date:	03/31/1987
From:	Shelton D TOLEDO EDISON CO.
To:
Shared Package
ML20205R137	List: ML20205R134 ML20205R159 ML20205R173 ML20205R183
References
TAC-65028, NUDOCS 8704060249
Download: ML20205R173 (10)

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APPLICATION FOR AMENMENT TO FACILITY OPERATING LICENSE ?;0. NPF-3 FOR DAVIS-BESSE NUCLEAR POWER STATION UNIT NO. 1 Encicotd are requested changes to the Davis-Besse Nuclear Power Station, Unit Ns. 1, Facility Operating License No. NPF-3. Also included are the Safety Features Actuation System / Emergency Diesel Generator Sequencer Logic Description. Safety Evaluation and Significant Hazards Consideration.

Ths preposed changes (submitted under cover letter Serial No. 1369) ccnccrn:

S:ction 3/4.3.2, Safety System Instrumentation, Specification 3.3.2.1 Table 3.3-3, Safety Features Actuation System Instru-mentation.

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/ By ,

D. C. Shelton Vice President. Nuclear Sworn to and subscribed before me this 31st day of March, 1987.

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. M Notary Public, State of Ohio d[ My commission expires d /8!f/

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8704060249 870l$01 PDR ADOCK 05000346 P PDR

d Drcket No. 50-346 Licsnte No. NPF-3 Sarici No. 1369' Actzchaent 1

Tha following information is provided to support issuance of'the rsquzoted changes to the Davis-Besse Nuclear Power Station, Unit No. 1 -

Op: rating License No. NPF-3,. Appendix A. Technical Specification Section 3.3.2.1 Table 3.3-3.

A. Time required to inplement: This change is to be effective immediately upon issuance of the License Amendment.

l B. Reason for change (Facility Change Request No. 87-0093): Revise Technical Specification 3.3.2.1. Table 3.3-3, Safety Featuren Actuation System Instrumentation, to require that 3 sequencer channels be operable at a mininum rather than 4. To aid in the understanding of this change, salient operational features of the Davis-Besse Safety

. Features Actuation System / Emergency Diesel Generator. Sequencer are .

provided as an attachment. As described in the attached Safety Evaluation, these changes do not involve an unreviewed safety question.

C. Safety Evaluation: See attached Safety Evaluation.

D. Significant Hazards Consideration: -See attached Significant Hazards Consideration.

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Dickot No.-50-346 1 Liesnso No..NPF-3 Scrial No. 1369 Attcchment 1 Pega 1 g DESCRIPTION O_F_ DAVIS-BESSE SPAS /EDG_ SEQUENCER LOG _IC Tho starting circuitry of each of the two (2) Emergency Diesel Generatora (EDG)' at Davis-Besse includes two (2) independent sequencers that prevent ovorlording of the EDG when an STAS actuation signal is coincident with tha less-of-offsite power. The sequencers are an integral part of the Safety Features Actuation System (SFAS). Each of the four (4) SFAS logic chtnnals employs one (1) sequencer. The sequencer causes components to be loedsd in five (5) steps following a coincident SFAS signal and loss-of-offsite power. The sequencing is done by blocking of SFAS signals to the activated equipment.

The calient operational features of the sequencer logic are summarized balcwi

c. The seq 2encer does not block the SFAS signal to the actuated equipment if offsite power is available,

b. If offsite power is lost, the SFAS signal is blocked from the

, actuated equipment by the sequencer. The sequencer then completes the actuation of ECCS equipment on a prodocarmined time sequence to ensure staggered loading of the EDG,

c. Either of the two sequencer channels associated with an EDG will provide the above sequenced loading of the EDG, Tha following describes the detailed interface logic (see Figure 1 of the ettschad Safety Evaluation) of the sequencer with the SFAS logic channel.

Tha sequencer output signal is OR-gated with the trip signal of the SFAS Output Module. In the normal state (sequencer OFF) the signal state is a l1egical"0". In the. trip block state (sequencer timing) the signal state is a icgical "1". The trip signal of the SFAS Output Module to the same

'OR-gata maintains a logical "1" while in the untripped mode and changes to a Icgical "0" with a 2-out-of-4 SFAS trip condition present on the input of the Output Module. .The output of the OR-gate is determined by tha $FAS trip signal and changes to a logical "0" with a trip signal prosent unless the sequencer is timing. In this case the output signal of tho OR-gate remains or returns to its normal (untripped) state of a l icgieci "1".

Functionally the outputs of the OR-gates of SFAS logic channel 1 and

icgic channel 3 are taken through another OR-gate logic. The output of 3 thio OR-function changes to a logical "0" only if both inputs are trippsd. A logical "0" will actuate the associated components of cctuatien channel 1. With the described arrangement the nequencer in

cith2r channel 1 or channel 2 is capable to block the actuation of the

SFAS components until the proper time step has occurred. This prevents

cvariccding of the EDG during its startup. Logic channels 2 and 4 are

similcely combined to form actuation channel 2.

D:ckat No. 50-346 Lic2nte No. NPF-3 Serial No. 1369 Attachment 2 Pega 1 i SAFETY EVALUATION ,

INTRODUCTION The purpose of this safety evaluation is to correct an error in Technical Spscification Section 3.3.2.1 Table 3.3-3 by changing the minimum number of esquencer channels required to be operable from 4 to 3. The present requirement is overly restrictive and is inconsistent with the Action Statenant in that the Action Statement cannot be followed once it is entered.

SYSTEMS AFFECTED

. Scfety Features Actuation System (SFAS)

. Emergency Diesel Generator (EDG)

, DOCUMENTS AFFECTED Technical Specification 3.3.2.1 USAR Sections 7.3 and 8.3

, FUNCTIONS OF SYSTEMS AFFECTED The cafety function of SFAS is to automatically prevent or limit fission

, product and energy release from the core, to isolate the containment vascal, and to initiate the operation of energency safety features (ESP) i cquipt:nt in the event of a LOCA.

Tha cafety function of the emergency diesel generators (EDG) is to provide emergency onsite elec,trical power in case the normal power sources are lost. .

Tha safety function of the EDG sequencer logic is to automatica13y energize ths ESF equipment at a predetermined sequence in case the Safety Feature Actuation System has been tripped concurrent with a loss of offsite power.

EFFECTS ON_ PLANT SAFETY The starting circuitry of the EDG includes an SFAS sequencer that prevents overlording of the EDG when an SFAS actuation signal is coincident with a Icss-of-offsite power (undervoltage condition existing on the essential 4.16 kv bus). Each of the four SFAS channels has its own sequencer with no commonality with the redundant channels. This ensures channel separation criteria are satisfied. The logic sequencer causes components to be load:d onto the EDG in five steps following a coincident SFAS signal and 1ccc-of-offsite power. When the sequencer is actuated the SFAS signal to a comp:nent is blocked until the proper time step has occurred. This pf0v:nts overloading of the diesel generator during its startup.

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m Dockst No. 50-346 License No. NPF-3 Sarial No. 1369 j Attachment 2 l Page 2 4

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-Each EDG receives these signals through two parallel SFAS channels including

, cecociated sequetter (See Figure 1). During normal plant operation both , i esqutacer channels associated with an EDG are in a condition that permits start-up of ESF equipment upon receipt of an SFAS signal. Following a lozs-of-offsite power both sequencers send ' signals that cause the EDG sequsncer to naquence starting of ESF components. Only one sequencer usads to operate to allow sequencing of the ESF components associated with ths appropriate EDG. Having an individual sequencer channel with each SFAS channel ensures that the single failure criteria is satisfied. This is bscause a single sequencer channel failure will not affect both EDGs.

1 l Since only one sequencer channel per EDG is required to be operable to

! clicw proper sequencing of ESF components, there is no necessity that the Tschnical Specifications specify the minimum number of operable sequencers ha four, as presently stated. This is supported by the Action Statement id:ntified by the Technical Specification being Action Statement 9. This Actien Statement requires that the inoperable unit be placed in a tripped

, cendition and that the minimum units operable be satisfied. Requiring all fcur sequencer channels to be operable makes it impossible to satisfy Action Statement 9 for the SFAS sequencers once this Action Statement is 4

entered. Additionally, in Table 3.3-3 for all other components that have

~a oimilar number of total units (4) and units to trip (2) the minimum

' unita cperable is three. The SFAS sequencer is the only component in Tcble 3.3-3 where four trains exist and four trains are the minimum

, rsquired to be operable.

, Ths revised Technical Specification will allow one sequencer channel to be incperable an long as the sequencer is placed in a state that allows ESF components to be started under all possible plant scenarios. To I i natizfy this condition Action Statement 9 is also revised to identify the I

! prepar safe condition /of the inoperable sequencer. The condition identified en:uros ESF components are actuated properly both with or without icss-of-offsite power.

UNREVIEWED SAFETY QUESTION EVALUATION 1 Tha preposed action would not increase the probability of occurrence or

consequences of an accident or a nalfunction of equipment important to cafety previously evaluated in the Updated Safety Analysis Report (USAR).

Tho proposed action does not involve a modification to any plant systems cr aquipment and as such does not increase the probability of an accident

prsvicuely evaluated. It is shown above that with the inoperable sequencer t chann21 in a tripped condition, the safe operation of the ESF equipment is not affected. The revised action statement r,quirements provide for i physical removal of the sequencer module. This puts the logic in a state that ESF equipment are properly started and sequenced (if required) in the i

avant of SFAS actuations independent of whether a loss of offsite power i

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D:ckst No. 50-346 Licente No. NPF-3 Ssris 1 No. 1369 Attcchment 2 Pcg2 3 )

has cr has not. occurred.- Thus the proposed action does not increase the prsbcbility for malfunction of equipment important to safety. Similarly, ,

tha proposed action does not increase consequences of accident or malfunction of equipment important to safety previously evaluated.in the USAR.

Tha preposed action would not create a possibility for en accident or a' malfunction of equipment important to safety of a different type than prsviously evaluated in the USAR. The proposed action does not involve a codification to any plant system or component. It is shown above, that with the inoperable sequencer channel in a tripped condition, the safe eparation of the ESF equipment is not affected.

Tha preposed action does not decrease the margin of safety defined in the b: sis,for the Technical Specifications. It is shown above with the

, insparable sequencer channel placed in a tripped condition the operability

, cf ths SFAS channels is ensured by maintaining the required coincidence Icgic. Since proper sequencing is still ensured by the revised action statem:nt and minimum operable unit requirements, the response time of ESF equipaint is maintained within the assumptions of the Safety Analysis Rsp rt. In addition, compliance with the single failure criteria is not affected.

, CONCLUSION Furcurnt to above it is concluded that the proposed action does not involva an unreviewed safety question.

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D:ckst No. 50-346 Licante No. NPF-3 Ssrial No.1369

, .Attcchment 3 Fago I g SIGNIFICANT_RAZARDS CONSIDERATION j i

INTRODUCTION Th2 purpose of this License Amendment Request is to correct an error in Technical Specification Section 3.3.2.1, Table 3.3-3, by changing the minimum number of sequencer channels required to be operable from 4 to 3.

, The present requirement is overly restrictive and is inconsistent with the Action Statement in that the Action Statement cannot be followed once it is entsred.

SYSTEMS AFFECTED Safet'y Features Actuation System (SFAS)

. Emargancy Diesel Generator (EDG)

DOCUMENTS REFER __EN_C_ED l

Technical Specification 3.3.2.1 USAR Saetions 7.3 and 8.3 l FUNCTIONS _0.F SYSTEMS AFFECTED The safety function of SPAS is to automatically _ prevent or limit fission product and energy release from the core, to isolate the containment vcssal, and to initiate the operation of emergency safety features _(ESF) squip sat in the event of a LOCA.

, Ths safety function of the emergency diesel generators (EDG) is to provide

.easrgsney onsite electrical power in case the normal power sources are lect, f

i Th2 safety function of the EDC sequencer logic is to automatically energize tha ESF equipment at a predetermined sequence in case the Safety-Feature Actuation System has been tripped concurrent with a loss of offsite power.  ;

' EFFECTS ON PLANT SAFETY Tha starting circuitry of the EDG includes an SFAS sequencer that prevents cvsricading of the EDG when an SFAS actuation signal is coincident with a leso-ef-offsite power (undervoltage condition er.isting on the essential 4.16 kv_ bus). Each of the four SFAS channels has its own sequencer with no commonality with the redundant channels. This ensures channel separation critoria are satisfied. The logic sequencer causes components to be Icedsd onto the EDG in five steps following a coincident SFAS signal and Icec-of-offsite power. When the sequencer is actuated the SFAS signal to a comptnent is blocked until the proper time step has occurred. This

'priv:nts overloading of the diesel generator during its startup.

Dicket No. 50-346

, :Licante No. NPF-3 Sarici No. 1369 i

Attachment 3 1 Pcgs 2 .

g Ecch EDC receives these signals through two parallel SFAS channels including casociated sequencer (See Figure 1 of the Safety Evaluation). During 3

1 norm 31 plant operation both sequencer channels associated with an EDG are in a condition that permits start-up of ESF equipment upon receipt of an SFAS aignal. Following a loss-of-offsite power, both sequencers send signtis that cause the EDG sequencer to sequence starting of ESF components.

Only cne sequencer needs to operate to allow sequencing of the ESF components esecciated with the appropriate EDC. Having an individual sequencer chtnnal with each SFAS channel ensures that the' single failure criteria is eatisfied. This is because a single sequencer channel failure will not affect both EDGs.

Since only one sequencer channel per EDG is required to be operable to allcw proper sequencing of ESF components, there is no necessity that the Techn'ical Specifications specify the minimum number of operable sequencers be four. as presently stated. This is supported by-the Action Statement idsntified by the Technical Specification being Action Statement 9. This Action Statement requires that the inoperable unit be placed in a tripped J csndition and that the minimum units operable be satisfied. Requiring all four esquencer channels to be operable makes it impossible to satisfy Action Statement 9 for the SFAS sequencers once this Action Statement is a

antered. Additionally, in. Table 3.3-3 for all other components that have a sicilar number of total units (4) and units to trip (2) the minimum units operable is three. The SFAS sequencer is the only component in Table 5.3-3 where four trains exist and four trains are the minimum rsquired to be operable.

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Ths ravised Technical Specification will allow one sequencer channel to  ;

bs in:perable as long as the sequencer is placed in a state that allows ESF components to be started under all possible plant scenarios. To 4

estisfy this cordition Action Statement 9 is also revised to identify the prepsr safe condition'of the inoperable sequencer. The condition identified susures ESF components are actuated properly both with or without iloss-of-offsite power.

' BASIS FOR NO SIGNIFICANT HAZARDS CONSIDERATION i

Ths preposed changes do not involve a significant hazards consideration ibaccuse the operation of the Davis-Besse Nuclear Power Station, Unit

!Ns. 1. in accordance with these changes would not:

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j 1. Involve a significant increase in the probability or consequences of 1 en accident previously evaluated (10CFR50.92(c)(1)).

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7 Dockst No. $0-346 Licante No. NPF-3 S2 rial No. 1369 Attachment 3 Pcga 3 g The proposed action does not involve a modification to a'ny plant systems or equipment and as such does not increase the probability of.an accident previously evaluated. It is shown above that with '

tho inoperabic sequencer channel in a tripped condicion, tne sate cperation of the ESF equipment is not affected. Thus the proposed.

rction does not increase consequences of accident previously evaluated in the USAR.

2 Create the possibility of a new or different kind of accident from rny previously evaluated (10CFR$0.92(c)(2)) .

The proposed action does not involve a modification to any plant systen or component. It is shown above, that with the inoperable esqueocer channel in a tripped condition, the safe operation of the ESF equipment is not affected.

l 3. Involve a significant reduction in a margin of safety (10CFR50.92(c)(3)).

It is shown above with the inoperable sequencer channel placed in a tripped condition the operability of the SFAS channels is ensured by maintaining the required coincidence logic. Since proper sequencing io still ensured by the revised action statement and minimum operabir unit requirements, the response time of ESF equipment is maintained within the assumptions of the Safety Analysis Report. In addition, ccepliance with the single failure criteria is not affected.

CONCLUSION

!Cn tha basis of the above, Toledo Edison has determined that the amendment

requsst does not involve a significant hazards consideration.

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