2CAN069801, Application for Amend to License NPF-6,revising Portion of Plant Protection Sys Design to Ensure That ESFAS Meets Its Applicable Design Requirements.Rev 1 to Engineering Rept 97-R-2015-01 Encl

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Application for Amend to License NPF-6,revising Portion of Plant Protection Sys Design to Ensure That ESFAS Meets Its Applicable Design Requirements.Rev 1 to Engineering Rept 97-R-2015-01 Encl
ML20236J122
Person / Time
Site: Arkansas Nuclear Entergy icon.png
Issue date: 06/30/1998
From: Hutchinson C
ENTERGY OPERATIONS, INC.
To:
NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
Shared Package
ML20236J126 List:
References
2CAN069801, 2CAN69801, NUDOCS 9807080056
Download: ML20236J122 (12)
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Text

i Entergy opwelions,Inc.

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g inesa m FkssfMe, AR T2901 Tel 501-8%4688 I CR Hutchinson I

W@s AO June 30,1998 2CAN069801 U. S. Nuclear Regulatory Conunission Document ControlDesk Mail Station OPI-17

' Washington, DC 20555

Subject:

- Arkansas Nuclear One- Unit 2 Docket No. 50-368 License No. NPF-6 .

Request for NRC Review of ANO-2 Plant Protection System Change under 10CFR50.90 t

Gentlemen:

At*=ekad for your review and approval is a proposed change to the Arkansas Nuclear One, Unit-2 (ANO-2) Plant Protection System (PPS) which has been determined to involve an Unreviewed Safety Question in accordance with 10CFR50.59(a)(2).

Entergy had identified that a failure of a DC bus (FODCB) could result in an u==ceaa*= hie plant response as discussed in ANO-2 LER 96-04 dated November 27,1996 (2CANI19 and supplemented in letter dated January 30,1997 (2CAN019701). The FODCB, with an assumed secondary plant trip, results in the loss of offsite power to one division of Engineered Safety Features Actuation System (ESFAS) (loss of control voltage to offsite switchgear

' results in failure of one 4160 bus to transfer with individual breakers remaining "as is" due to i loss of control voltage). The power division failure includes the de-energization of one pair

! of vital instrument buses (VIBs) that could have disabled two measurement chann certain parameters. Given a channel in indefinite bypass under the current design, FODCB could have resulted in an unacceptable PPS response. As a result of this condition, controls were promptly established to prevent a PPS channel remaining in bypass for greater than 48 hours5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br />. The failure of two channels of vital *mstrument power had not been fully evaluated in

! the PPS design bases for each ESFAS function.

The proposed change modifies the ESFAS portion of the ANO-2 PPS design to defeatJ.' the backup power supply for the auctioneered power sources for ek--I A and D RPS and

' ESFAS bistables, and to provide selective logic for Emergency Feedwater Actuation Signals and Main Steam Isolation Signals This will ensure that ESFAS will have the redundancy and l

  • = '= rte sufEcient to assure that (1) no single failure results in loss of the protection function with a channel in indefinite bypass, and (2) removal from service of any component g

E

' or channel does not result in loss of the required minimum redundancy required by the ANO-2 Technical Specifications (TSs). The proposed facility changes including the PPS failure modes and effects conclusions and the proposed ANO-2 Safety Analysis Report (SAR) i

__ _x 4

U. S. NRC June 29,1998 2CAN069801 Page 2 changes are enclosed. The design change package, while substantially complete, has not been finalized. If any significant changes occur as a result of design change package completion, they will be provided to the NRC for review.

The existing failure modes for evaluated equipment in the ANO-2 Safety Analysis Report (SAR) do not accurately reflect the de-energization of either pair of VIBs caused by a FODCB. Even though the proposed modification does not, in itself, create a new malfunction, the proposed SAR change description has been concluded to be a malfunction of equipment of a different type than previously reported in the SAR and therefore, meets the criteria of 10CFR50.59(a)(2). Therefore, a request for NRC review and approval under the requirements of 10CFR50.90 is being requested for the proposed changes. Upon NRC approval of the proposed changes and ANO's completion of the final design, the SAR will be revised to resect these changes.

The proposed change has been evaluated in accordance with 10CFR50.91(a)(1) using criteria in 10CFR50.92(c), and it has been determined that this change involves no significant hazards considerations. The bases for these determinations are included in the attached submittal.

Entergy Operations has committed in LER 96-04-01 to implement this change by startup from the 2R13 outage which is scheduled to commence on January 8,1999. We request your review and approval of this proposed change by December 30,1998. Although this request is neither exigent nor emergency, your prompt review is requested.

Very trul rs, i

CRH/sab Attachments To the best of my knowledge and belief, the statements contained in this submittal are true.

SUBSCRIBED AND SWORN TO before me, a Notary Public la and for Nu County and the State of Artansas, this Jo" day of OW , 1998. '

V

,.. 2.m , . J " OFFICIAL SEAL" L Notary Public f gota,y $ $ ( *,f br ansas My Commaission Empires /.2//5/czoo 7 county of Pope L _My Com_mjasion Exp.12/15/200_7_ g :

, U. S. NRC June 29,1998 2CAN069801 Page 3 cc: Mr. Ellis W. Merschoff Regional Administrator U. S. Nuclear Regulatory Commission Region IV 611 Ryan Plaza Drive, Suite 400 Arlington, TX 76011-8064 NRC Senior Resident Inspector Arkansas Nuclear One P.O. Box 310 London, AR72847 l Mr. William D. Reckley NRR Project Manager Region IV/ANO-1 & 2 l

U. S. Nuclear Regulatory Commission i NRR Mail Stop 13-H-3 One White Flint North 11555 Rockville Pike Rockville, MD 20852 Mr. David D. Snellings Director, Division ofRadiation Control and Emergency Management Arkansas Department ofHealth 4815 West Markham Street Little Rock, AR 72205

I l

l ATTACHMENT IQ 2CAN069801 RESPECTIVE SAFETY ANALYSES IN THE MATTER OF AMENDING LICENSE NO. NPF-6 ENTERGY OPERATIONS. INC.

ARKANSAS NUCLEAR ONE. UNIT TWO DOCKET NO. 50-368

Attachment to l 2CAN069801 Page 1 of 8 DESCRIPTION OF PROPOSED CHANGES l

The proposed change modifies a portion of the ANO-2 Plant Protection System (PPS) design to ensure that the Engineered Safety Features Actuation System (ESFAS) meets its applicable design requirements and to ensure adequate plant protection under design events when selected trip channels are in indefinite bypass. The proposed modification of PPS is within the existing licensing basis of ANO-2, however, the resulting failure modes and effects analysis l

will change from that described in the ANO-2 Updated Safety Analysis Report (SAR).

l Specifically, the proposed modifications correct the ESFAS response to a failure of a DC bus (FODCB) with a channelin bypass by:

1. defeating the backup power supply for the auctioneered power sources for channel A and D bistables for all ESFAS and RPS functions,
2. providing selective open and close logic for Emergency Feedwater Actuation Signals (EFASI and EFAS2) valves (interposing relays), and
3. providing selective logic to the Main Steam Isolation Signal (MSIS) signal to close EFASI and EFAS2 valves (interposing relays).

BACKGROUND The ANO-2 PPS includes the electrical and mechanical devices and circuitry (from sensors to actuation device input terminals) involved in generating signals associated with the two protective functions, ESFAS and Reactor Protective System (RPS). The RPS is that ponion of the PPS which generates signals that actuate a reactor trip. The RPS consists of sensors, calculators, logic, switchgear and other equipment necessary to monitor selected nuclear steam supply system conditions and to effect reliable and rapid reactor shutdown (reactor trip) if any one or a combination of the monitored parameters reaches a limiting safety system setting.

The ESFAS is that portion of the PPS which generates signals that actuate Engineered Safety Features (ESP) to mitigate the consequences of an accident. The ESF actuation signals controlled by the ESFAS include Containment Isolation Actuation Signal (CIAS),

Containment Spray Actuation Signal (CSAS), Containment Cooling Actuation Signal (CCAS), Safety Injection Actuation Signal (SIAS), MSIS, Recirculation Actuation Signal (RAS), EFAS1, and EFAS2.

The ANO-2 vital power design consists of two power divisions. Each power division for the PPS consists of one emergency diesel generator (EDG), one battery bank, two inveners, and one pair of VIBs for each power division. The PPS is designed such that no single channel failure results in loss ofits protective functions. RAS was specifically designed not to actuate upon loss of a pair of VIBs assigned to a power division. Power supplies for the refueling water tank (RWT) level instrument loops for RAS channels B and C are auctioneered so that only one instrument loop fails with a power division loss. The remaining ESFAS input

Attachment te 2CAN069801 Page 2 of 8 instrumentation loops (steam generator level, steam generator pressure, pressurizer pressure, containment pressure, etc.) are not equipped with auctioneered power supplies. The PPS has internal auctioneered power supplies for the bistable and channel bypass functions.

The ANO-2 TS previously allowed one PPS channel to be in bypass for up to 48 hours5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br /> to perform maintenance or testing based upon the low probability of a fault such as loss of a power division affecting more than one channel during that time interval. Amaad-aat 159 to ANO-2 TS 3/4.3.1 and 3/4.3.2 increased the time allowed during plant operation at full power :

with one PPS channel bypassed from 48 hours5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br /> to "until the next cold shutdown" (referred to as indefmite bypass).

Subsequent to receipt of the TS amendment, a condition was identified where upon a power

! division failure (loss of DC bus) and a PPS channel bypassed on the functional division, CIAS, l~ CSAS, and EFAS could fail to actuate. This was reported to the NRC in ANO-2 Licensee Event Report 96-04 dated November 27,1996 (2CANI19603) and supplemented in letter dated January 30,1997 (2CAN019701). The SIAS and CCAS functions would have failed to actuate on the containment pressure signals, but the functions would have been satisfied by the RCS pressure signal input fading low. However, if a channel was not in bypass, all PPS l functions would be available if a power division is lost.

As a result of this condition, controls were promptly established to prevent a PPS channel remaining in bypass for greater than 48 hours5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br />. It was also committed that plant modifications, as determined necessary, would be installed by completion of refueling outage 2R13. Changes to the Safety Analysis Report (SAR) would also be provided in an amendment following the 2R13 outage. Outage 2R13 is scheduled to commence on January 8,1999.

i DISCUSSION OF CHANGE The ANO-2 design bases for the PPS require a four channel system design with two out of three coincidence logic with one channel bypassed This logic combined with single failure criterion of 10 CFR 50 Appdr A ensures that no credible functional failures of the PPS exist. A single failure scenario identified by the condition discussed in LER 96-04-01 documents that the failure of one of two redundant 125 VDC power distnbution divisions could result in partial de-energization of one of two pairs ofPPS measurement channels.

ANO-2 has two redundant power distribution divisions. As mentioned previously, each of the two power divisions has two uninterruptible power supplies (UPS). The channel one and i three pair (1/3) are assigned to the red power division and channel two and four pair (2/4) are assigned to the green power division. Each ANO-2 UPS has three power sources: the battery backed DC bus, preferred 480 VAC, and alternate / bypass 480 VAC. The 480 VAC system is wmnally powered via a stepdown transformer feed from a 4160 VAC safety bus. The 4160 VAC safety buses are powered by offsite power with an onsite EDG backup.

F Attachment to 2CAN069801 Page 3 of 8 Each measurement channel of RPS and ESFAS includes both a process instrument loop and a histable comparator card. With the exception of the Refueling Water Tank (RWT) level, the process instnament loops have single power sources (the bistables are currently provided with auctioneered power from both divisions). De-energization of a single VIB results in de-energization of the process loops De-energization of a process loop results in tripping of the bistable for those functions with decreasing signal setpoints (the bistable remained energized).

RWT channels B and C instrument process loops feature auctioneered power supplies to prevent inadvertent RAS actuation during loss of a power division (loss of two VIBs). Since L

the process loop fails low with the bistable remaining energized, those functions with an l increasing signal setpoint do not trip. Assuming one channel is bypassed in a non-fauked I

cimnel, only one channel would remain functional and two channels would fail non-tripped l

fx nnetions with increasing signal setpoints Gven a channel in indefinite bypass under the

! current design, FODCB wouluesult in an unacceptable PPS response.

Details of the existing actuation scenarios and the proposed design changes with subsequent actuation scenarios for plant response to a FODCB are contained in Enclosure 1; hgi%

Report 97-R-2015-01, "PPSResponse to Failure ofa DC Bus. " A summary of the proposed ANO-2 modi 6 cations to correct the ESFAS response to a FODCB with a channel in bypass consist of the following changes:

Measurement Channels A measurement channel consists of a process loop with power source and a bistable that has auctioneered power supplies. The measurement channels that have bistables with increasing signal setpoints require modification to ensure a system level safe response to a FODCB. For PPS channels A and D, the bistable auctioneered power mapply located in the adjacent channel will be defeated (spared). The specific modification include:

  • Channel A bistable backup power supply PS3 located in channel B will have both input and output power wiring liAed.
  • Channel D bistable backup power supply PS6 located in channel C will have both input and output power wiring lifted.
  • PS3 and PS6 power supply trouble alarm output contacts will be defeated.
  • PSI located in channel A and PS8 located in channel D (the unaffected primary power supplies) will power the bistables in the associated channel.

Matrix Logic Each ESFAS matrix logic has two power supplies (i.e., one powered from power division 1 and one powered from power division 2). Each power supply has a pair of matrix relays assigned to each load group / power division (1 & 3) or (2 & 4). De-energization of a power ,

supply results in a half trip in the ESFAS logic. There are no modifications required to maintain operability of the matnx logic for de-energization of'a pair of VIBs. The RPS matrix logic is similar to the ESFAS matrix logic with the following exceptions:

Attachment to 2CAN069801 Page 4 of 8

1. all matrix power supply (PS) pairs are not powered from opposing power divisions (i.e.

two logics have PS pairs supplied by different divisions while the remaining four logics have PS pairs supplied from the same division), and

2. PS/ matrix relay groupings are not based on a common power division (i.e. the matrix relays are paired (1 & 2 or 3 & 4) regardless of the PS power division.

Initiation Logic The PPS initiation logic consist of single power supplies, one per trip path, in series with contacts from the six matrices and a set of trip path output relays. No changes are necessary to this initiation logic.

The initiation logic output through trip path (TP) relays are arranged in a selective logic configuration. For an RPS trip, logic is (TPI or TP2) and (TP3 or TP4) [the TP number corresponds to its power cource channel). RPS de-energization of VIB pair 1 & 3 or 2 & 4 l results in a trip response. The initiation logic output (TP relays) is arranged in a selective logic configuration for ESFAS. The logic is (TPI or TP3) and (TP2 or TP4) for ESFAS. For the FODCB de-energization of 1 & 3 or 2 & 4, ESFAS generates a half-leg trip by the initiation logic.

Actuation Lonic With the modification, the actuation logic for MSIS, EFASI and EFAS2 interposing relays will be changed from single trip path actuation to a selective 2 out of 4 trip path logic. The MSIS interposing relay will be wired the same as other MSIS subgroup relays. EFASI and EFAS2 actuation logic will be wired such that (TP1 or TP3) and (TP2 or TP4) will de-energize the interposing relays to provide an open demand to the EFW pump discharge valves. Trip paths (TP1 and TP3) or (TP2 and TP4) will energize the interposing relays to provide a close demand to the EFW pump discharge valves.

Wiring changes to incorporate the selective logic actuation of EFASI and EFAS2 interposing relays defeat the existing control room actuation alarm for de-energization of an EFAS lockout relay or an interposing relay. For each EFAS function, normally open contacts from the two interposing relays and the two lockout relays will be wired in series with the coil of a relay located on Diverse Emergency Feedwater Actuation System (DEFAS) subpanels. The subpanel relay contacts will be used to maintain existing control room alarm monitoring and EFAS blocking of DEFAS. EFAS actuation interconnection with DEFAS will be wired such that either interposing relay or either lockout relay de-energization will block the DEFAS function.

Summary of PPS Response to the Channes The proposed change permits any one channel to be bypassed and, when required, tested or calibrated 'during power operation without initiating a protective action at the system level.

During this operation, the active parts of the system shall, of themselves, continue to meet the single failure criterion. PPS (ESFAS and RPS) functions with decreasing signal setpoints (excluding RAS and EFAS) actuate, and those functions with increasing signal setpoints (including EFAS) remain functional with one measurement charmel tripped and one t

Attachment to 2CAN069801 Page 5 of 8 measurement channel not tripped by a FODCB. RAS remains functional with one measurement channel tripped and the other three operable. Acceptable functional response is achieved even with any single channel in bypass Table 2 of the enclosed Fmp% Report 97-R-2015-01 provides a detailed matrix of the modified measurement channel response to FODC3.

The revised PPS Failure Modes and Effects Analysis (FMEA) in Enclosure 1, indicates the acceptability of the PPS response to licensing basis events. As indicated in the FMEA, deenergization of the two bistable power supplies corrects the response to the FODCB scenario. Although the modification corrects the description of the plant response, the single channel faiiure causes have also been expanded to include failure of a single bistable power supply.

With the proposed modification, e PPS will have the redundancy and independence sufficient to assure that (1) no single failure results in lou of the protection function, and (2) removal from service of any component or channel does not resuk in loss of the required minimum redundancy required by the TS.

  • PPS will be designed to fail in a safe state or into a state demonstrated to be acceptable.
  • PPS will meet the single failure criterion ofIEEE 279-1971 to the extent that any single failure within the system does not prevent proper protective action at the system level and no single failure will defeat more than one of the four protective channels associated with any one trip function.

LicensingBasis Analysis The ANO-2 SAR section 15.1.31 " Loss Of One DC System" analyzes the FODCB as an l

l initiator and discusses its failure analysis. The causes for the FODCB are DC leg to leg fault in the bus or in the power distribution circuit from the battery. Since the proposed change has no imphet on an accident initiator, the frequency of occurrence is not changed. In order for the FODCB as a single failure with an accident to de-energize two VIBs, the FODCB would have to occur prior to the safety bus energization by offhite bus fast transfer or prior to safety bus energization by the emergency diesel generator (EDG). The potential for de-energization of one pair of VIBs is, therefore, limited to time from initiation of the accident to time for safety bus response to the secondary plant and Reactor Protection System trips.

A copy of the proposed ANO-2 SAR changes reflecting the planned design modifications and <

to correct the existing SAR related failure modes description is contained in Enclosure 2.

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Attachment to 2CAN069801 Page 6 of 8 DETERMINATION OF NO SIGNIFICANT HAZARDS CONSIDERATION An evaluation of the proposed change has been performed in accordance with 10CFR50.91(a)(1) regarding no signi6 cant hazards considerations using the standards in 10CFR50.92(c). A discussion of these standards as they relate to this amendment request follows:

Criterios 1 - Does Not Involve a Signincast Increase la the ProbabRity or Consequemees of as Accident Previously Evaluated.

The ANO-2 Plant Protection System (PPS) includes the electrical and mechanical devices and circuitry (from sensors to actuation device *mput terminals) involved in generating signals associated with the two protective functions, Engiaa-ed Safety Feature Actuation System (ESFAS) and Reactor Protective System (RPS). The RPS is that portion of the PPS which generates signals that actuate a reactor trip. The ESFAS is that portion of the PPS which generates signals that actuate Engineered Safety Features (ESF) to mitigate the consequences of an meddaat. .

The ANO-2 Safety Analysis Report (SAR) section 15.1.31 " Loss Of One DC System" _

analyzes failure of a DC bus (FODCB) as initiator and its causes. The causes for the FODCB are DC leg to leg fault in the bus or in the power distnbution circuit from the battery. Since the proposed change has no impact on the accident initiator, the frequency of occurrence is not changed. In order for the FODCB as a single failure with an accident to de-energize two VIBs, the FODCB would have to occur prior to the safety bus energization by offsite bus fast transfer or prior to safety bus energization by the emergency diesel generator (EDG). The potential for de-energization of one pair of VIBs is, therefore, limited to time from initiation of the accident to time for safety bus response to the secondary plant and Reactor Protection System trips.

The effects of the FODCB are being revised to assume a secondary plant trip that results in de-energization of one power division. The existing analysis conclusions remain unchanged.

The accident analysis is being revised to include de-energization of a pair of vital AC instrument channels. De-energization of two vital AC sources has not been previously j documented as a des'qpt bases event.

l Auctioneered bistable power supplies for Plant Protection System (PPS) channels A and D are being moddied to a single power source for each of these two channels. Single channel trips will resuh for all PPS functions in channels A or D for loss ofits single channel bistable power source. The PPS channels B and C auctioneered power supplies remain unchanged to maintain Recirculation Actuation Signal (RAS) response to a FODCB.

Regarding PPS measurement channels withm' creasing signal setpoints, de energization of a sirigle power supply either results in failure of a measurement channel (B or C) to a non-tripped state or in failure of a measurement channel (A or D) to a tripped state. Neither single

Attachment to 2CAN069801 Page 7 of 8 channel failure scenario impacts accident initiation or mitigation. For PPS measurement channels with decreasing signal setpoints the single channel de-energization events result in failure of a single affected measurement channel to a tripped state. The PPS two out of three logic design with a channel bypassed ensures operability with a single channel failure. Neither condition impacts accident frequency or consequences With the exception of Recirculation Actuation Signal (RAS) and Emergency Feedwater Actuation Signal (EFAS), a FODCB results in an automatic ESFAS initiation for those functions with decreasing signal setpoints. For other ESFAS functions with.a decreasing signal, channels A and C or channels B and D fail to the tripped state. For those functions with an increasing signal setpoint (including EFAS), a FODCB results in a single channel failing not tripped, one channel tripping, and two channels remaining functional. System level functions remain operable with either a one out of two logic (no channels bypassed) or a one out of one logic (with a channel bypassed).

Interposing relay actuation logic has changed from single trip path to selective trip path logic.

This change insures emergency feedwater (EFW) discharge valves will receive an automatic open or close demand based on steam generator level and pressure demands.

Therefore, this change does Dat involve a significant increase in the probability or consequences of any accident previously evaluated.

s Criterion 2 - Does Not Create the Possibility of a New or Diferent Kind of Accident from any Previously Evaluated.

In response to de-energization of a pair of Vital Instrument Buses (VIBs), those ESFAS functions with increasing signal setpoints, as a minimum, remain functional with one out of one logic. One channel trips, one channel does not trip, and two channels remain functional.

One of the functional channels may be bypassed without impact on operability. The trip response of those ESFAS functions with decreasing signal to trip setpoints remains unchanged.

i EFAS coincidence logic to close the EFW discharge valves requires three out of four channels to be in a non-tripped state. With a FODCB one channel is tripped, one channel is not

! tripped, and two channels are functional. The close logic becomes two out of two with a FODCB.

By defeating the auctioneered bistable power sources for PPS channel A and D bistables, PPS measurement channel A or D will fail to its tripped state. This change ensures no more than one channel (B or C) fails to a non-tripped state for the FODCB.

L With selective logic EFAS pump discharBe valves will receive control signals to initiate emergency feedwater and to terminate emergency feedwater flow by open and close demands

[ generated independent of the 120 Volt channel pair de-energization.

I

Attachment to 2CAN069801 Page 8 of 8 The existing ANO-2 Failure Modes and Effects Analysis does not demant failure of a pair of vital instsument AC channels. Neither the 120 Volts AC nor the 125 Volt DC system single failure analysis assumes failure of two channels of 120 Volts AC. Even though the failure of either pair of VIBs caused by a FODCB is not a result of the proposed change, the SAR change will address the potential for de-energization of a pair ofinstrument buses The ANO-2 SAR will be updated to renect the documentation and modification of the PPS design to ensure safe plant response.

Even though the plant response to FODCB is being modified, the proposed ANO-2 PPS design resolution does not create the possibility of a new or different kind of accident from any previously evaluated in the SAR. The PPS will have the redundancy and independence sufficient to assure that (1) no single failure results in loss of the protection function, and (2) removal from service of any component or chanr.el does not result in loss of the required minimum redundancy required by the TS. PPS will also meet the single failure criterion of IEER 279-1971 to the extent that any single failure within the system does not prevent proper protective action at the system level and no single failure will defeat more than one of the four protective channels associated with any one trip function.

Criterion 3 - Does Not Involve a Significant Reduction la the Margin of Safety.

Technical Specification Bases 3/4.3.1 & 3/4.3.2 assure sufficient PPS redundancy is maintained to permit a channel to be bypassed. Under the current design, a FODCB will result in reduction of margin by decreasing the number of functional channels to less than two.

However, with the proposed modification removal from service of any component or channel for indefinite bypass will not result in loss of the minimum redundancy required by the TS.

This activity will restore the margin by ensuring ESFAS required functions remain capable of automatic actuation with a FODCB.

Therefore, this change does not involve a significant reduction in the margin of safety.

Based upon the reasoning presented above and the previous discussion of the amendment request, Entergy Operations has determined that even though the proposed PPS design description results in an accident or malfunction of a different type, the requested change does ,

1 DQ1 involve a significant hazards consideration.

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