ML20137P417

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Rev 0 to JPN-PSL-SEES-95-034, Safety Evaluation for Provisions to Trip EDG Output Breaker on Cias in Plant Modes 5 & 6
ML20137P417
Person / Time
Site: Saint Lucie NextEra Energy icon.png
Issue date: 10/23/1995
From:
FLORIDA POWER & LIGHT CO.
To:
Shared Package
ML20137M095 List:
References
FOIA-96-485 JPN-PSL-SEES-95, JPN-PSL-SEES-95-034, JPN-PSL-SEES-95-34, NUDOCS 9704090247
Download: ML20137P417 (18)
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Text

-- 10-04-1995 08:05M1' St Lucie Ras 2d2nt OH ica 407 451 4622 'P.02'

.,. l PAGE 1 OF 10

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.FIORIDA POWER AND LIGHT COMPANY ST. LUCIE UNIT 2 SAFETY EVALUATION FOR TIG PROVISIONS TO TRIP EF AGENCY DIESEL GENERATOR OUTPUT BREAKER ON CIAS IN PLANT MODES 5 AND 6 f

P JPN-PSL-SEES-95-034 .

REVISION O SAFETY RELATED NUCLRAR ENGINEERING DEPAR7 MENT CUNO BEACH, FLORIDA l

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i 7-9704090247 970401 PDR FOIA SINDER96-485 PDR n j

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Date: October 23,1995 ,

Tot S. A. Vatcer Departrnent: JPN/PSL From: D. J. Denver Nucasar Engineeri ST, LUC 6E UNIT 2 Sut(ect:

SAPETY EVALUAT10N FOR THE PROVl510NS TO TRIP WAERQENCY DIEEE GENERATOR. OUTPUT BREAKER C,N CIAS IN PLANT MODES 5 AND 4 M _=_ -- M_ e nam, o .

Attachea for your use is safety Evolustion (SE) JPN-PSL-SEES.95 034. Rev. O which evoluetes provis6ons to tr, Emergency Diesel Generator (EDOI output breakere on CtAS in plant mooes 5 and 6 The referenced SE is to be used to support the Jurrper Ld:ed Lead which will be required to f aclitete Urdt 2, EDO testing, during modes 6 and 6. The SE eve 69etes the insteRetaon of jumpers in the ESFA8 cabinets,6n order to tr9 the EDG output toekere rm receipt ci e CIAS signet. The SE le m response to the 2A EDO test failure which occt:rred on October 12 (rof. STAR 9613911 end is en 6nterim EDO protective mesours until a permanent modifeatum oen be implemented.

M you hows any questions, please contact Warren Busch at ext. 7464.

. I WAs/essert f

cel R. Kuisv6ch (with ett.)

L. A. Rogers C. H. Wood L. J. Boes.nger tite i

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~ 10-24 '995 09:06AM 'St Lucie Fes: dent OHice . 407 461 4622 P.03 o

Sn]-P5L- 5Fes-95-034 gsutstou o REVIEW AND APPROVAL RECORD PMC W IO 4

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  • Sor Contretter Evals As Detemined By Projects ** Review interface As A ftin On All 10CFRSO.59 Evals anc FLAs FPL PROJECTS APPROVAL: ____ M DATE: <c/n/R~ i OTHER INTERFACES I

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~ 110-24-1995 008 06Af1 - St Lucie Restdant Gefica  ; 407 461 4622 P.04 JPN-PSL-SEES-95-034 REVISICN 0 ,

PAGE 3 OF 10 T m E Olr CONTENTS P

IITLE E SKC.ICIE 1

-- Cover Review and Approval Record 2 3

-- Table of Contents i

4

-- Abstract Purpose and Description 4

- 1.0 ,

Licensing Requirements 5 2.0 3.0 Analysis of Effects on safety 7 Failure Modes and Effects Analysis 8 4.0 Plant Restrictions 8 5.0.

Effect on Technical specifications 8 6.0 7.0 Unreviewed Safety Question 8 Determination l s

S.O Actions Required 10 9.0 Referenceo 10 ATTAC1 DENTS M g 1 Typical Mcdification Sketch ' 1 i

24- N .Osr06AW St Lve s, Ris; dant Off ies . e 461 4622 p,c5 JPBI-PSL-SEES-95-034 REVISION O PAGE 4 OF 10 c

i AESTRACT t

while performing a portion of the safeguards on October 12, 1995, an unexpected l f testing required by Technical Specification, (EDG) trip occurred. Review of the Emergency event Diesel Generatorrevealed a sequence of events leed to EDGin whic l trip damage.

signal was blocked creating a scenario that co This caused the grid when a CIAS (without SIAS) was initiated.

~

I (load follow / share) to a EDG governor mode to switch from " droop"This condition led to a reve fixed frequency reference. Since the protective signals are J

protective relay actuation.

bypassed under emergency operating conditions, the leadEDGto con under long term exposure could potentially run, which j

degradation.

The proposed modification will trip the EDG output d 6 only,.therefore l I

br,eaker upon CIAs initiation in plant modes 5 anThis change will not elhinating a potential EDG failure mode.

tion J

affe6c plant operating practices and will enhance EDG i

~in modhs ,5 and 6 safety question and does not does not constitute an unreviewed require a Technical Specification chango Dm =am =d Bamerletian 1.0 l

The purpose of this safety evaluation is to provide basis for a plant temporary modification (plant modes 5 and 6 only), output invo i tripping of an emergency diesel generator (either.2A or/

breaker on a CIAS, I damage if an actual or a spurious TheCIAS CIAsoccurs functionwhile the EDG is required by bei tested is connected to the grid.

Technical Specification to be operational in all plant modes, including 5 and 6 if core alterations or fuel movement take place.This m The SIAS is not required in plant modes 5 and to

  • deenergize 6. close" CIAS spare involves wiring any convenient (A or B, as required) to trip the EDG contact in the ESFAS cabinet output breaker and prevent the scenario described in the abstract.

Attachment 1 shows the required connections and typical available  !

contacts. ]

l

. . 1 i

1 ~

10-24-1995i 08:07AM St Lucie Res: dint Office  : 4;y; 461 4622 . P.06 I

JPN-PSL-SEES-95-034 REVISICN O '

PAGE 5 OF 10 l.0 pu d en ==d namerisselon (cont'd) f in following changes:

The proposed modification will result PROPOSED CEANGE AsstaEPTIctis PRESENT C00lF19URATICet CIAS trips the EDG e Plent in modes 5 or SIAS is blocked. CIAS output breaker and 6.

changes the governor EDG remains running

  • Off-site power mode to isochronous. awaiting manual available EDG breaker remains closed resulting in a operator action. No e EDG in test mode reverse power or an potential for e EDG Connected to equipment damage, power Grid over current e CIAS Generated condition.

CIAS trips output

  • Plant in modes 5 or EDG breaker does not breaker, bus sheds  ;

6.

trip and the CIAS loads, EDG breaker '

e Loss of Off-site loads are loaded I immediately, re-closes in Power Event. approximately 1.2 "  !

e EDG powering an seconds and LOOP /CIAS isolated bus. loading sequence is e CIAS Generated initiated.

" This delay is not a concern because under the analyzed loss of offsite power scenario the EDG does not reach full speed and begins the loading sequence until 10 seconds af ter receiving a CIAS or other start signal.

2.0 Lic===:4me Emernir - en St. Lucie Unit 2 FSAR, section 8.3.1.1.1.f, makes following statements oncerning the BDG operational performance:

  • 1) The diesel generator sets start upon loss of voltage in the safety 4.16 KV buses or actuation of the engineered safety features actuation signals from the ESFAS which are safety in-jection actuation signal (SIAS), containment isolation actuation signal (CIAS) or containment spray actuation signal (CSAS).
2) Upon loss of voltage on the 4.16 kV safety busen, these buses are automatically separated from the nonasafety supply buses.

10-24-1995 ' 088 07AM St Lecte Residmt OH ice ". 407 461 4622 P.07 i

JPN-PSL-SEES-95-034 l REVISION 0 {

PAGE F OF 10 ,

I 2 . 0 Lie === % ==auir --a ta (Cont'd)

After each diesel generator set has_ attained normal frequency and voltage, the respective breaker closes if preferred ac

3)  ;

l power has been lost, thus block immediately for which " startingrequired" starting all loads '

belonging to the first signals are present (from ESFAS) or from circuit condit$ons indicating th&t they were previously running. If preferred ac power is still present, the diesel generator breaker does not close but the set remains at full frequency and voltage until manual actions are taken.

4)

The starting of subsequent loads are delayed by tir.ing relays with three or five second intervals between them.

5) i If preferred ac power is lost but no Engineered Safety Features actuation signal is present, only the loads shown under the column " Loss of Offsite Power" in Table 8.3-2 are automatically started.  :

above an SIAS appears, all i

6) If,, while operating as per step (5) loads are stripped and loading is perfomed per Table 8.3-2.

testing of the diesel

7) Means are provided for periodic generator sets under load when preferred bus supply is from the unit aux'iliary transformer. If preferred ac power.ir Tost occurs during this testing, the diesel or an accident generator breaker is opened and the sequence returns to step (3)." '

FSAR section 8.3.1.1.2k (ii) :

  • If the diesel is started as a result of an SIAS, CIAS, CSAS or loss of offsite power, all but two of the diesel generator lockout signals are overridden. Those which remain functional are engine over speed and generator differential, ...This rationale is in accordance with the intent of BTP EICSB 17, " Diesel' Generator Protective Trip Circuit Bypass"."

These commitments compey with Regulatory Guide 1.9 and IEEE 387 and are reflected in the present plant design.

FSAR section 15.7.4.1.2 discusses fuel handling accidents and bounds all in-containment accidents' radiological consequences by an accident (Fuel Handling of dropping a fuel element in a spent fuel pool Building).

4

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10-24-;995' as m - p ,. 407 4'61 4622 P.08 JPN-PSL-SEES-95-034 REVISION O '

l PAGE 7.0F 10 l I

2.0. tie === 4 ne meeruir--tm - (Cont ' d) d l The' CIFiMivotes a minimum contingent - Control of loads, Room ~ namely Isolation' a Shiel f Building Ventilation fans (HVE-6A and'68), Should these loads be 3 l

fans (HVE-13A and 13B) andla few valves.

required-to start with offsite power available or with EDGloss If the powering of I an isolated bus, they would start instantaneously.

off-site power occurs at'approximately same time aswith coordinated CIAS,thethese otherloads ,

are picked up in a loading sequence required loads.

that the ESFAS CIAS function be Technical Specification requires of irradiated fuel operational during core alterations or movementThe highis radiation reset CIA within the containment. 6.

to a lower value in mode .

anfaty 3.0 **=1 vain af Effeats an i 4 have the same effect The proposed temporary change will make the CIAS that is, if '

on the RDG in modes 5 and 6 as SIAS in modes 1 through 4, theEDGikoperationalandconnectedtothegrid,upon  ;

manual action and, if loss of power occurs, the EDG breaker will'close ,

and the loading sequence will he initiated.

Since the proposed change will result condition, in a system it is response bounded concluded that by this the previously analyzed. SIAS temporary mcdification is acceptable.

4.0 patiura +Ama ==d affneta a==1vala The proposed. modification will eliminate an existing failure modeThe of creating a potentially damaging operating condition for the EDG. they proposed changes will noc create any new failure modes since will result in EDG response identical to SIAS in modes 1 through 4.

5.0 M ant m*=tricti-=

This temporary modification shall be implemented only in plant modes l

5 and 6.

l- l f

l 6.O mefact on Tech =4 cal namelftencians  !

There is no effect on any existing Technical Specifications.

i I F

j N 03:0941 et 1.scs, ge8* cent Offs:e i 407 (=51 t.622 p,y j 4

l JPN-PSL-SEES-95-034 REVISION O PAGE 8 OF 10 unravie==d safety onenti e nat=c=3nati n I 7.0 (1) f As defined in 10 CFR 50.59, an unreviewed safety questica exists;  ;

if the probability of occurrence or the censequences of an accident or malfunction of equipment importent to safety previously evaluated in the safety Analysis Report (SAR) may be increased; or (ii) if a possibility of an accident or malfunction of a differentiftype than any the margin I

previously evaluated in the SAR may be created; or (iii)o reduced.

the fellowing evaluation serves to In accordance with 10CFR50.59, determine whether the temporary modification of tripping the EDG output breaker upcn CIAS actuation in plant modes 5 and 6 addressed in this safety evaluation constitutes an unreviewed safety question:

7.1 Does the proposed activity increase the probability of occurrence of an accident previously evaluated in the SAR?

The scope of the proposed codification, to make the ef fects of CIAS on the EDG same as SIAS, do not increase the probability of an occurrence of an accident previously evaluated in the SAR.

EDG start / trip are not accident initiating events.

consequences of an a

7.2 Does the proposed activity increase the accident previously evaluated in the SAR7 The proposed modification will not increase the consequences Tripping cf ,

of an accident previously analysed in the SAR.

the ED3 under test in the event of any ESFAS actuation results in a return to an analyzed leading sequence and therefore do not affect the accident analysis.

the probability of an 7.3 Does the proposed activity increase important to safety cecurrence of a malfunction of equtpment previously evaluated in the SAK7 The proposed modification will not increase the probability of cecunence of malfunction of equipment important to safety The modification of the EDG previously evaluated in the SAR. breaker trip circuit - additzon of normal operatienal parameters for the EDG and its output breaker,

15-24-1975 00 @ St Lscle %s tcent Offs:3  ; c .;51 4622 F.;0

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' ggyISION 0 FAGE 9 0F M (cone'd) of d 7.0 h *

  • ity j increase iv the ilmportant to consequencespreviously safety Does the proposed of actequipment 7 ,4 ralfunction SAR7 change the basicwere evaluated in the difications do Thenot modificacionsbility nor the output The proposed physical moequipment affected. increase the p of the do not of the EDG or its vent will Tre functionsanalyzed and they of a tnalfunctiCndtenporarym0dification f"**4uencesetikQ'gopose Po a an sec. .

7.5 Does the proposed activity create the possibility of an accident of a different type than any previously evaluated in the SAR7 The proponer2 modifications will result in the EDG res W ag to a CIAS the same way it responds to SIAs, which has been previously analyzed. The EDG or its breaker are not accident initiators, therefor the modification can not create the possibility of an accident of a different type than previously evaluated in t.he SAR.

7.6 Does the proposed activity create the possibility of a malfunction of equipment important to safety of a different type than any previously evaluated in the SAR?

Since the basic functions of the EDG syotem remain unchanged, the m;difAcation proposed does not create the possibility of a malfunction et equipmant important to safety of a different type than any previously evaluated in the SAR.

7.7 Doco the propoond activity reduce the margin of safsty as dofined in the basis for any Technical Specification?

The temporary modification preposed will increase the overall margin of safety for the plant by eliminating the potential fmilure mode ci operating the EDG connected to the grid with its protective featurco bypassed and trip conditions almost certainly generated by such an eparation.

As demonstrated above, the proposed modification la bounded by previously anslyzed TSAR scenarica.

w ag:N St Lucie Pes: dent Offtee . -*07 461 4622 p,.1 JPN-PSL-SEES-95-034

. REVISION O PAGE 10'OF 10 d

4.O let W =.Enquisad t

CIAS shall be incorporated into the trip circuit.of the EDG outpu '

breaker by wiring any available "deenergize to close" spare CIAS contacts in parallel with the SIAS contact as shown in Attachment 1.

The relay, contact of which will be used, should be, verified

+

to be operational prior to implementation of the modification.

a CIAS A contact is used for A train logic and Ensure that CIAs E contact is used for B train logic,

+

Verify by test that the CIAS contact provides an EDG breaker trip signal.

9.0 mafaramatas 9.1 STAR 951391 Rev.17 9.2 control Wiring Disgram 2998-B-327, Sh.757, Sh.967, Rev.14 9.3 Control Wiring Diagram 2998-B-327, 9

9.4 St. Lucie Unit 2 FSAR, Amendment 9.5 St. Lucie Unit 2 Technical Specification, Amendment 78 9.6 Instruction Manual 2998-15662. Rev.5 9.7 Regulatory Guide 1.9 i 9/10 IEEE Standard 387 e

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... - . f MODIFIED REFERENCE : 2998-B.327, SH. 957 REV.17 i

2988.B.~,27, SH.967, REV.14 f

TYPICAL SPARE CONTACTS l

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B540(10.111 TB637(7 ti RECOMMENDED TB539(3,4) TB642(1,2 )

TB 539(6,7) TB639(10,ll)

TB541(6,7) TB636(10.111 JPN-PSL-SEEP-95-034 ATTACHMENT 1 '

REV.0

10-24-1995 0831 Oft 1 St Luc a Sea:aint Offsee 4C"7 461 4622 A.13 4

l i

The test was exited prior to completing steo B.5 and resume step 8.6.

e Aligns both 2A and 23 EDGs with offsite power at or near full load

  • Initiates a Channel A CIAS then resets ,

e Initaties a Channel B CIAS then resets .I Initiates a Channel A SIAS then resets e

  • Initaties a Channel B SIAS then resets .

e Initiates'a Channel A CSAS then resets

. Initaties a Chanrel B CSAS then resets  ;

After each ESTAS Channel is actuated individuni component actuations are vertfled, of Nf#

This particular step had been rev1 sed. -n The previous procedure r

Iw Revision inserted a SIAS Signal Lrc ":teaW the CIAS Signal. This did not allow for separate verification of the CIAS Signal actuations since the SIAS also generated a CIAS The licensee believed thet changing the Signal by cesign.

crcer would erhance the procedure and ::rovide more detailed ESFAS Signal verifications.

i

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~ ~ 10-24-1995 Oe81;At1 St Lsete Reatdint oH ica  ; 407 461 4622- P.14 e

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After the Channel A CIAS Signal was inserted and the component At this time ,

actuations verified. Channel A CIAS was reset.

the 2A EDG tripped on reverse power. The test was secured and i

the 2A EDG declared inoperable.

STAR #951391 was written which identified a design deficiency of the Unit 2 EDGs.

An investigation by the licensee determinea that during the performance of Section 8.6 of'0P 2 0400050. EDG 2A was runnin CIAS-A was parallel to the grid and loaded to >3600kW.

manually initiated in accordance with step 12 of the test procedure. Actuation of CIAS inputs to the EDG 4governor circuit to change it from the droop mode (i.e. follows the grid frequency) to an isochronous mode (i.e. reverts to preset The EDG 2A frequency and does not follow the grid frequency).

preset frequency was lower than that of the grid. This resulted in reducing fuel to sicw the EDG down. leading to sa-reverse 40wer flow and causing the generator to act as a motor (or synchronous capacitor). The ERDADS printout of Bus 2A3 voltage and current and EDG current confirmed a sudden Cnange at the approximate time CIAS was initiated. The reverse pcMer relay actuated; newever, due to the presence of the CIAS-A signal. the relay trip function was blocked. Upon resetting cf the CIAS-A signal. the reverse power relay trip block was 60 l

+

24-1995 ' 08811Gr1 St Lucie Realdint DFfice 1 407 461 4622 P.15 .

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removed and the EDG tripped. Total time of EDG operating under reverse power was approximately 45 seconds.

A review of the EDG control circuits by engineering found that the EDG starts on SIAS. CSAS or CIAS.and that these signals cause the EDG to change from droop mode to isochronous mode (Ref. CWDs 957 & 958 and Vendor Manual 2998-7434). Opening the Bus 2A2-2A3 tie breaker will also change the EDG from droop t.

1sochronous modes.

In the case of SIAS and CSAS (CSAS will only occur with SIAS), the EDG circuit breaker will trip if closed, permitting the EDG to run separate from the offsite power source.

However. CIAS without SIAS does not trip the EDG breaker. resulting in the EDG operating in isochronous mode while still connected to offsite power.

EDG 2A was operated in synchronism with the offs e source prior to manual imtiation 6f CIAS A. The is ronous mode

/

frequencysetpointfor,EOG2Aislowertha hat of the offsite 4 source.

Therefore.,w[eNtheEDG2Agov nor changed from droop

/ tk, to isocnronous .thehelracks ted to slow the EDG from j

theoffsitesc[cefrequenctot isochronous frequency

)

')f setpoint.

is resulted in th EDG " motoring" (a reversal of power toptte generator) wi the nerat:or trying to run the engine /(Ifthe1sochr ous frequency setDolnt is higher thant that,df tne offsite s rce.theEDGw$i>1dattempttospeedthe load (the grid) up.)

61 ,

' ~ 10-24 '995 08 1.r41 s*, Luc 1o Res2d:nt off es. 407.461 4622 P. 6 The situation described above could only occur with the EDG running in parallel with the offsite source and an actuation of J

the CIAS relay without SIAS. This condition is not expecteo during normal operation or any design basis event recuiring the EDGs. )

J 4 l Following the trip of the 2A EDG due to the reverse power i

relay, the testing was halted. The 2A EDG voltage regulator j 4

was visually inspected with Satisfactory results and the 2A E[iG was started and loaded successfully as an operability check. +l l

The current drawn by the EDG 2A generator during the reverse

  • power incident was approximately 330 amps, as shown by the ERCADS printout. From the ERDADS Printout the licensee ,

determined that the 2A EDG output current of 477.54 amps reversed to 330.38 amps for a net change of 807.84 amps which was sufficient to actuate the reverse power relay. Concurrent with this. Bus 2A3 voltage changed from 4331.7 volts to 4360.2 as a result of the generator producing additional MVARS, i.e.,

acting as a synchronous capacitor with a high power factor.

This value is well within the 660 amp continuous,ratg capacity; of the generator windings. Based on the abov 4 DG 2A "M w

= & M te n damageo by the incident. Further, performance of the regular 18 month preventative maintenance (Maintenance Procedures 2-22000 g g-M-00180) sc % 1 e to PC & Y thorough inspectien on the Qg1}5/{-

EDG e M g-1d e " 1.J .J. M any damage p c M % . b 62

~

~ ;0-24-;995 '08:12AM St Lucie Restdint Office  ; 407 461 4622 F.;7 e .

EDG 2B has not been tested with a manual CIAS actuation, therefore its operability was not affected.

1 The Unit 1 EDGs governor control design is different from the l Unit 2 EDGs. The Unit 1 EDGs have been successfully tested )

using an essentially identical ESFAS test procedure.

Therefore, there is no operability concern fron the Unit 1 EDGs.

b Based on the above, the EDGs A# considered operable. l The Inspector reviewed the above assessment and noted that Wile actuation of the CIAS relay without SIAS is not expected during normal operation both Unit 2 EDGs are tested monthly and operated a minimum of 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> eseh':;aralleled 10 the offsjte,g a.,JW M - ,

4 L power source. Ocuid air tuation of CIAS occur, abste,~.ai p s/ 4

!N camage to the EDG,1; pes;,Lic M l The Inspector was concerned by several aspects relateo to tttts--  ;

design deficiency identified during testing:

outA.6L P'

1. Integrated Safeguards testin ad, received a high level of management and technical support attention due to the l licensee's misinterpretation of testing requirements particularly rela ad to swing bus components. The current i h revision r the test sequence for initiating f

'E3 P

~ - .. . . - _ . - _ ~ . . - .

  • ' 10-PA-1995 Der 12AM. St Lucie Pes: dint Offica  ; 407 461 4622 P.18 CIAS/SIAS/CSAS Signals in step 8.6 as a procedural enhancement. Although tgsggsgsgugcjsgugy p performed earlier on Unit 1[lt was not~ reviewed in l sufficient detail to assess the impact upon equipment or l system operation on Unit 2. .
2. This condition has existed since initial construction.

There was no liceps e identii'ication of this failure mode, ,

i.e. receiving aids Signal while paralleled to an -

offsite power source.

3. The 2A EDG was operated for approximately 45 seconds with a reverse power trip blocked. A review of the CIEs determined that a local reverse power alars occurred which the licensee believes also generated a control room alars.

y Since operators were either unaware or did not question jff these alarms, it's dubious whether operator actions would

have prevented damage if the CIAS had not been reset -

! unblocking the reverse power trip. ,

The licensee has placed a temporary hold on EDG testing pending Zh -

resolution of their STAR. Options being considered include:

e Plant Change / Modification (Long Tenn)  ;

  • Jumper / Lifted Lead 1solating the effected relay (Short Term)  ? ,

s 64 i

ToTCL P.10

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