05000331/LER-1993-001, :on 930211,discovered Automatic Standby DG Starts Due to Momentary Essential Bus Undervoltage Due to Ice Storm.Operators Took Appropriate Actions to Restore RWCU & Well Water Sys

:on 930211,discovered Automatic Standby DG Starts Due to Momentary Essential Bus Undervoltage Due to Ice Storm.Operators Took Appropriate Actions to Restore RWCU & Well Water Sys

ML20034H172
Person / Time
Site:	Duane Arnold
Issue date:	03/04/1993
From:	Kerr J, Denise Wilson ILLINOIS POWER CO.
To:	Davis A NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III)
References
LER-93-001, LER-93-1, NG-93-0929, NG-93-929, NUDOCS 9303160129
Download: ML20034H172 (5)

LER-1993-001, on 930211,discovered Automatic Standby DG Starts Due to Momentary Essential Bus Undervoltage Due to Ice Storm.Operators Took Appropriate Actions to Restore RWCU & Well Water Sys

Event date:
Report date:
Reporting criterion:	10 CFR 50.73(a)(2)(iv), System Actuation
3311993001R00 - NRC Website

text

E l}1b Iowa Electric Light and Power Company March 4, 1993 NG-93-0929 Mr. A. Bert Davis Regional Administrator Region III U. S. Nuclear Regulatory Commission 799 Roosevelt Road Glen Ellyn, IL 60137 Subject: Duane Arnold Energy Center

~~

fp de",

Docket No:

50-331 Op. License DPR-49 Licensee Event Report #93-001, Rev. O Gentlemen:

In accordance with 10 CFR 50.73 please find attached a copy of the subject Licensee Event Report.

Very truly ours, W

David L. Wilson Plant Superintendent - Nuclear DLV/RM/eah cc: Director of Nuclear Reactor Regulation Document Control Desk U.S. Nuclear Regulatory Commission Mail Station P1-137 Washington, D. C.

20555 NRC Resident Inspector - DAEC 160061 9303160129 930304 PDR ADOCK 05000331 S

PDR Duane Arnold Energy Center

• 3277 DAEClload

• Palo. Iowa 52324

• 319lB514611 I?hR ] 3 }Qg3

g.._

k a. m.. ;....::. u.o.

....;,t: ;..: 3 x a en LICENSEE EVENT REPORT (LER) i,,. a. x.,

is.t e e.c..:i= i..i.s.o.si, e c: e < *. s s

.o...-

ce

.s e....e ca..i. s..ic s ic.:.o so. sis..w..e.ic -i.es :: :s

..o.u i.u.n.c..iz

.s

. 03

. e ist

..e.i e.v C.O..au.c. w.sm.0 0. X ?"sil.c u.

5

.i Cw

.0.*C.a.

i.ps.c t.o. e..cL.i t PW 0

• a S88 Ci o,f e.ai

...ci.

. ace. s.c :. x mei

- ooc..

u.....

.a 2 10 t o i 3 ' 3 '1 ! ' io'!O 4

..c.c......

0 15 ' D Daare Areld Enercy Center

" *Autor.atic Standby Diesel Generator Starts Due to Momentary Essential Bus Under-Voltace Durino Tre Storm ev e...c m.n...o6. s o..

v

...o. ' r,.,a v.

I

..... c. i (

- a..mi...

• • c.

..se not.e

...ua s

.:v - ; :. ' e.. i e..

l l" f ',;,' f -

[' ;*,yl;.c.'- l :..

e.e None o4 5,oio.o, j,

j 012 1 l1 913!9}3 0l0l1- 0l0 013 0!4 9\\ 3 o,5,oio,o,

,....o.,

.r s e.v..u..,, o.... w..... +i.. c..,

e... -., -..

~

, n.

. n...n.,

g i

Nj n...

. n....

n,.

i

. n.

.o...

t i 1 m

= n n.,

e.

.c.

,s +..,~..

I~~

i

. n.,a, i

St o.t t il ioini n...o "..

......c 4,

.e ?).i3H.a i

e. 734sn3Heen.e J.6..

i = eADet Het 73.egHee.H.4 n

.att heel l

tS.ntnes W F94.#Wh.#

30 t..et n.

l

.0 73ase@same 6,C8ed.4. Co t.CT p TM. Lt. (tSt t.8.-o 0.wwet.

...g

..t. Cob 6 7 4 ig !?

John Kerr, Technical Support Specialist 3!1,9 815,1! t 1

c o a,.... e.......e.

........ =.. u

'. k

.C

.f C

8,.o. *. 6 8 C..Sf 9' 8* 8 Co.s.o t.?

0 658

$ l' t.

00w*0 5.*

g

,p, i

l 1

i i

I ! :, I I !

1 ! ! i i I.

i e i r I

I ! !

l ! l I

I i t i ! I

.0.

- i

• i

.t..

as** L s.g es t.L.t po.T g.*s Cv t p s t snegC gD

'di,"lf' r n...,.-,,.., c., o.....

o.,g,.

pe a v.. e,. -. a..

. ~,,.. n On February 11, 1993 with the plant operating at 100% power, both Standby Diesel Generators (SBDGs) automatically started three separate times but were not required to load.

The cause of each of the automatic starts was a sensed momentary under-voltage condition on both essential buses which was monitored by bus under-voltage relays that feed the SBDG start logics. The sensed momentary under-voltage conditions were caused by momentary grid disturbances during an ice storm.

Following verification that the essential buses were being powered from their normal sources, the SBDGs were secured and returned to standby mode. Reactor

'it' power was temporarily reduced until the weather improved.

This event had no effect on the safe operation of the plant.

.. :.... m.

. s w..u.m.. n-iso.

....:.i: :. m : s e.

LICENSEE EYENT REPORT (LER) i...n. x n n.,C* es.i e...ei....n.g.e.u : ::.< <,- i w

uw(.'1 LD.i.f:'c s.gc a.. o.cs,agstg s' w.3 -e s

....e.

s

'O e

g g

• t *: '-f.g ::

C.D.C.t>;. 'g es..o.ct ug.9 4st.e.C 9 3c

.tCw.A.tc t s.yes.33 0.

..g...:'O. X P3tl.C L.a 3'sC 0*0

08. Cl

'.t

. I.c....gDwC1C.. 180'.:

o.

...:c.

..e. x r,.. : ximi ooc..,....,

..a s

..c.c.....

Lane t.r.cle Ener y Center o is i o !o ! o ; 3 3 0 ' i :c'!O 4

"

• Automatic Standby Diesel Generator Starts Due to Momentary Essential Bus Under-l Vnitage n rine Ice Stor-e~i...c.w,n

..ais..

u a..

...e., o., + i

- i..;-...l Nt ;,..)

t.7,.,;;

c - j :..j....

..c.

ac:. r...... i

~

None o,sio;o:ci, i j

312 1 l1 913l913 0 l0 l 1

- 0l0 0l3 0 14 91 3 o isto t o i c e i e t i

...o.,... - r i o. v........ u.....

.. c.. i e.

n.

1. N i i..u...

i x

.,w...,

n,...

• • o-

.o...

i i i n

.nn.,

i...n.

.,w n,..

s,.e s

,!1. O!0 t a=~""--

==*

ri n-'o"-'

---._e'-i.5.+....~.c~..'.-

,...o....

t.,w m o.,

.,w n.,

,,.m

..,n,..

., we..,

,w....

..n..

i., w..

.,w...

uC88.b8 8 Co.e,.C, f.est Lt. etti

..a.

.... ca.

5 li

,7 4 39 g John Kerr. Technical Support Specialist 31li9 81 1

1 co-a n..

c.

.. i.c-co-o......w.

onc..no.. m....o.,.

l I

l

..isls s*

I j *t*f,.c ne7,+;;;c

! :o we.a.+ ; **;df t*0*l;'

cu

.cs.

co-o.s,

I

! ! 1 1

i ! '

' t !

i i i !

I I t I

i ! 8 f ? I t....

as-a. =' 6.: o.,

..s e s e..

'si":?'

rn

.....,,,,c.,,,.,.,2,......,.

p:

i e..e,.-..x-.......,..-.-n..

On February 11, 1993, with the plant operating at 100% power, both Standby Diesel Generators (SBDGs) automatically started three separate times but were not required to load.

The cause of each of the automatic starts was a sensed momentary under-voltage condition on both essential buses which was monitored by bus under voltage relays that feed the SBDG start logics. The sensed momentary under-voltage conditions were caused by momentary grid disturbances during an ice storm.

Following verification that the essential buses were being powered from their normal sources, the SBDGs were secured and returned to standby mode. Reactor power was temporarily reduced until the weather improved. 'i 8 '.

• This event had no effect on the safe operation of the plant.

?

e

)

P hRC Form 2t4A U S NuCLLAR REGULATORY COMMI55 SON APPROVED OMB NO 11h0-0104 (6 80

' LICENSEE EVENT REPORT (LER) cxpiRes no n TEXT CONTINUATION tsrmtro evRoch ecR RosnoNsr ro coMpLv wwwis E'oEI=^iScESSE'c' a"UREWs'r5rEN Iuf REEERos AND R[PORr5 MANAG(MtNr BRANCH (P $13) U 5 NUCLE AR' M 'f 0 ".*oEE"a E'u's 'o # C fr % 5 & l # 8t OF Mate ACIMENr AND BUDGER WASHNGTON DC 70573 f ACILIT Y N AME t u DOCKET NUMBLR LD LER NUMisERist PAC E i3p Tuus7R On"

"^"

Duane Arnold Energy Center 0

5 0 0 0 3

3 1

93 001 00 2

0F 4

1a u o1.,.,e-.,,

.o...a~,

< Nec o.

.w m m

I. DESCRIPTION OF EVENT

On the evening of February 11, 1993, the plant was operating at 1007, power and was in day 4 of a 30 day limiting condition for operation (LCO) on the "A" residual heat removal (RHR) pump. The weather conditions were rainy, icy, and windy with the temperature about 27 degrees F. An ice storm in the area had c.aused several grid disturbances but none that had yet directly af fectec' the plant.

At 1721, both Standby Diesel Generators (SBDGs) automatically started but were not required to load, the emergency service water (ESW) pumps started for SBDG cooling, the "A" reactor water cleanup (RWCU) pump tripped, and the "B" and "D" well water pumps tripped. Also at this time, switchyard breakers 8090 ("A") and 3110 ("B") opened. At 1722, the "D" well water pump automatically restarted and the "A" and "C" well water pumps were manually started to restore well water flow to the plant. At 1733, the "A" RWCU pump was restarted and returned to service and the "A" well water pump was secured. At 1739, the "A" SBDG was secured and returned to standby mode after running for 18 minutes. At 1740, the "B" SBDG was secured and returned to standby mode after running for 19 minutes. The ESW pumps were then secured. At 1840, the "B" well water pump was restarted and the "C" well water pump was secured. At this time, plant conditions were the same as prior to the SBDG starts except that the "A" and "B" switchyard breakers l

remained open.

At 1914, both SBDGs automatically started but were not required to load, the ESW pumps started for SBDG cooling, the "A" RWCU pump tripped, the "D" well water pump tripped and automatically restarted, and alarms were received from the instrument AC under-voltage and uninterruptible AC inverters. Also at this time, switchyard breaker 9180 ("G") opened and automatically re-closed, and switchyard breaker 0220 ("H") opened but did not re-close. At 1936, the "A" RWCU pump was restarted and returned to service. At 1937, after an electrician inspected the "H" breaker relays in the switchyard, the "H" breaker was re-closed with permission from the load dispatcher. At 1938, the instrument AC under-voltage and uninterruptible AC inverter alarms were reset. At 1941, the "A" SBDG was secured and returned to standby mode after running for 27 minutes. At 1942, the "B" SBDG was secured and returned to standby mode after running for 28 minutes. The ESW pumps were then secured. At this time, plant conditions were the same as they were just prior to the second start of the SBDGs. The "A" and "B" switchyard breakers remained open.

At 1950, both SBDGs automatically started but were not required to load, the ESW pumps started for SBDG cooling, the "A" RWCU pump tripped, the "D" well water pump tripped and automatically restarted, and alarms were received from the instrument AC under-voltage and uninterruptible AC inverters. Also at this time, switchyard breakers "G" and "H" opened.

r f

l l

1

(

g mA v s uctcA. m.utAroay coM ss.o.

m oviooysu m m LICENSEE EVENT REPORT (LER) expiats A so:::

TEXT CONTINUATION rsTmTtD sonotn nR nespousno coMety wiTu T-s M HTS REGARD NG BUR N I STi ATE 1 E FCORDS REGU TORY COM Ss ON WASH NGTO O 55 A O

MANAGE (9.T AND E

A N T 7

F Aclu f Y #i AME O f [mti h0MBLR (21 LER NUMBLJei6)

PALEW

"^*

'2A"S*'

EE Duane Arnold Energy Center 0

5 0 0 0 3

3 1

93 001 00 3

0F 4

m i o,...,,,-.,,..e,.o...~.. ec r.,,,, w. n m At 1951, the "G" breaker automatically re-closed. At 1959, after an electrician inspected the "H" breaker relays in the switchyard, the "H" breaker was re-closed.

The instrument AC under-voltage and l

uninterruptible AC inverter alarms were reset. At 2002, the "A" SBDG was secured and returned to standby mode after running for 12 minutes. At 2003, the "B" SBDG was secured and returned to standby mode after running for 13 minutes. The ESW pumps were then secured. At 2009, the "A" RWCU pump was restarted and returned to service. At this time, plant conditions were the same as they were just prior to the second and third starts of l

the SBDGs. The "A" "B" switchyard breakers remained open.

l l

l At 2010, the decision was made to begin reducing reactor power to 75% using the recirculation pumps, in anticipation that more severe grid disturbances may cause a plant trip. At 2120, reactor power was being held at 75%. At 0500 on February 12, 1993, after weather conditions had improved, operators began increasing reactor power using the recirculation pumps. At 0531, the plant was back to 85% power and by 0700 the plant was operating at 100% power. At 1015, after power line inspections were completed, the load dispatcher closed the "A" and "B" switchyard breakers.

At this time, plant conditions were the same as prior to the first SBDG starts.

1 i

l

II. CAUSE OF EVENT

1 The cause of each of the automatic starts of the SB0Gs was a sensed momentary under-voltage condition on both essential buses which was i

monitored by bus under-voltage relays. The relays feed directly into the

)

I SBDG start logics which seal in upon actuation. The ESW pumps started automatically when the SBDGs started. The sensed momentary under-voltage conditions were also the causes for the breakers opening in the switchyard, the RWCU and well water pump trips, and the alarms received.

The sensed momentary under-voltage conditions were caused by momentary grid disturbances during an ice storm. High winds and ice buildup on l

transmission lines caused the lines to whip around and eventually touch I

each other causing grid disturbances.

III. ANALYSIS OF EVENT

This event had no effect on safe operation of the plant, nor would it have an effect cn afe operation during any other plant conditions. The SBDGs started as designed in response to the sensed momentary voltage dips on the essential buses, but were not required to load. The ESW pumps started as designed when the SBDGs started. The RWCU and well water systems are not safety related and tripping of these pumps had no adverse consequences. The instrument AC under voltage and uninterruptible AC

N 864C f orrn MA b b WUCLEAR REGULATORY COMM15s40M APPRDvf D OMS NO 314010A C CBI LICENSEE EVENT REPORT (LER) imRes mir EXT CONTINUATlON gtgt,rguy Rr,sgs,c,vge,OMP,tv w;igs EO"E"Em"s'MA,fA2fMt7e' ROC,'"Es'xl v's',"lltiT Oft % T 2 !'O'u'#"O,' = s "1&d MZ' OF MANAGEMENT AND BUDGFT. WASHINGTON. DC 20501 F AClul V,eAM6 (1J DOCK (f NUMBER (2)

LER NUsrBERill PAGEi);

'! vUa'tR 753fR Duane Arnold Energy Center 0 5l 0 0 0

3' 3 1

93 001 00 3

0F 4

im m..

nu..

,m...a. m..aa e e Rc 1.,,, mwmm At 1951, the "G" breaker automatically re-closed. At 1959, af ter an electrician inspected the "H" breaker relays in the switchyard, the "H"

+

breaker was re-closed. The instrument AC under-voltage and uninterruptible AC inverter alarms were reset. At 2002, the "A" SBDG was secured and returned to standby mode after running for 12 minutes. At 2003, the "B" SBDG was secured and returned to standby mode after running for 13 minutes. The ESW pumps were then secured. At 2009, the "A" RWCU pump was restarted and returned to service. At this time, plant conditions were the same as they were just prior to the second and third starts of the SBDGs. The "A" "B" switthyard breakers remained open.

At 2010, the decision was made to begin reducing reactor power to 75% using the recirculation pumps, in anticipation that more severe grid disturbances may cause a plant trip. At 2120, reactor power was being held at 75%. At 0500 on February 12, 1993, after weather conditions had improved, operators began increasing reactor power using the recirculation pumps. At 0531, the plant was back to 85% power and by 0700 the plant was operating at 100% power. At 1015, after power line inspections were completed, the load dispatcher closed the "A" and "B" switchyard breakers.

At this time, plant conditions were the same as prior to the first SBDG starts.

II. CAUSE OF EVENT

The cause of each of the automatic starts of the SBDGs was a sensed momentary under-voltage condition on both essential buses which was monitored by bus under-voltage relays. The relays faed directly into the SBDG start logics which seal in upon actuation. The ESW pumps started automatically when the SBDGs started. The sensed momentary under-voltage conditions were also the causes for the breakers opening in the switchyard, the RWCU and well water pump trips, and the alarms received.

The sensed momentary under-voltage conditions were caused by momentary grid disturbances during an ice storm. High winds and ice buildup on transmission lines caused the lines to whip around and eventually touch each other causing grid disturbances.

III. ANALYSIS OF EVENT

l This event had no effect on safe operation of the plant, nor would it have an effect ca safe operation during any other plant conditions. The SBDGs started as designed in response to the sensed momentary voltage dips on the essential buses,.but were not required to load. The ESW pumps started as designed when the SBDGs started. The RWCV and well water systems are not safety related and tripping of these pumps had no adverse consequences. The instrument AC under-voltage and uninterruptible AC i

l'I p.

I

'gaCg,m au u s Nacttan necetAtouv coMMI5 SON APPROv[D OMB NO UMMs4 LICENSEE EVENT REPORT (LER) rxnears A2an TEXT CONTINUATION tsT,Mano av=Dr., ein arss.oNsr To cOMety w,Tn T-s IMORMAf tDN cot LECfloh EE OUE ST % 0 HRS FORWARD A D [

RTS MAN G[M[N RANC 53 U $ NJCL A nrA'#0t!%'fs'oN =ML"'4"o,*"a' OF MAhACIM{ hi AND BUDGET wA$HtNGTON DC 70W3 f ACiulv hAME tu DOCKLTNumetR m LL R NUMBI Hibi PAL L t3' "NIsY?'

Uu"u$~

N Duane Arnold Energy Center 0 l5l 0 0l0 l 3 3 l1 93 001 00 4

0F 4

iu u or,,,....ou. a.

.n,.a.

...ao,,.

a N nc o.,,,, mA.nm inverter alarms were due to loss of sync between the instrument power sources, which is expected under these circumstances.

The switchyard breakers opened as expected in response to the grid disturbances. There were no bus transfers or load sheds during these events. All alarms and auto actuations that were received were expected.

IV. CORRECTIVE ACTIONS

Following each of the SBDG and ESW pump starts, operators verified that the essential buses were being powered from their normal sources and contacted the load dispatcher to share information and coordinate actions.

The SBDGs and their associated ESW pumps were secured, one at a time, after verifying that the grid was stable. Operators took appropriate actions to restore the RWCU and well water systems and to clear alarms as discussed above. The operators and the load dispatcher worked together to re-close the switchyard breakers at the appropriate times. The "A" and "B" breakers were not closed until the following day as a precaution due to very high winds in that direction from the plant. As discussed above, reactor power was reduced to mitigate the consequences of possible further grid disturbances until the weather improved. Since all equipment operated properly and personnel actions were appropriate, no further corrective actions were required.

V. ADDITIONAL INFORMATION

A. Previous Similar Events LERs 91-08 and 92-11 report automatic SBDG starts due to weather conditions.

B. EIIS System and Component Codes Systems: FK-Switchyard System EK-Emergency Onsite Power Supply System CE-Reactor Water Cleanup System EE-Instrument and Uninterruptible Power System AD-Reactor Recirculation System KG-Nonessential Service Water System BI-Essential Service Water System Components: EK-DG-Diesel Generator This report is being submitted pursuant to 10CFR50.73(a)(2)(iv).