05000266/LER-2002-003, Re Possible Common Mode Failure of AFW Due to Partial Clogging of Recirculation Orifices

Re Possible Common Mode Failure of AFW Due to Partial Clogging of Recirculation Orifices

ML030830161
Person / Time
Site:	Point Beach   (DPR-024, DPR-027)
Issue date:	12/26/2002
From:	Cayia A Nuclear Management Co
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
FOIA/PA-2003-0094, NRC 2002-0111 LER 02-003-00
Download: ML030830161 (6)

LER-2002-003, Re Possible Common Mode Failure of AFW Due to Partial Clogging of Recirculation Orifices

Event date:
Report date:
2662002003R00 - NRC Website

text

SE:60 WOE-0-7-D2:39 NUclear Managcnient C'onpav), L.l.C Point Beach Nuclear Plant 6610 Nuclear Road f\\& u iveis, "W! 3424 i NRC 2002-0111 December 26, 2002 Document Control Desk U.S. NUCLEAR REGULA'I ORY COMMI SION Mail Station P 1-137 Washingion, D.C 20555 La dies/l~ent1 em n:

Docket Numbers 50-266 and 50-301 Point Beach Nuclear Plant, Units I and 2 Licensee Event Report 26612002-003-00 POSSIBLE COMMON MODE FAILURE 10 CFR 50 73 OP AFW DUE TO PARTIAL CLOGGING OF RECMIRCUiL'ItN ORIFICES Enclosed is Licensee Event Report 266/200 This report discusses the discovery of a pos have resulted in the partial clogging o rthe auxiliary feed water system pumps.

Corrective actions, completed and propose commitments have been identified in italic If you have questions concerning the info Mr. C. W. Krause at (920) 755-6809.

Sincerely,

'A.JC a V ce Presiden Enic s e CWK/kmd cc:

NRC Regional Administrator NRC Resident Inspector 2-003-00 for the Point Beach Nuclear Plant, Units 1 and 2.

ýiblc common mode failure mechanism that potentially could low restricting orifices in the recirculation line for the 1, have been identified in the attached report. Ne%%

iation provided in this report, please contact NRC Project Manager PSCW I

Cominfod la tNuclar Etendkoce S.

./

. r.

NRC FORM.166

-. *,u..L-:,[, I t-"..-,'" 4 t"..cl, 1,',

C

,.i.'

20 ", d 9 E : 60 Fe w07Z-D.E.

S... ""Z,....

....,*:*-~o Fr,, *,,'r...,.¢.*('/*7*

" r -:B *'O *, O L* C _.*Srb Cr_

-.IV;' *T %

• r

• ... " r "'

i+/-Lvc: r, o-,c f:f,*.u rcd.

UI(;Tt j

FAMI"IrY lNAMF fit POINT BEACIi NUCLEAR PL/I IT U41 i 1.

TITLE (4)

POSSIBLE COMMON MODE FAILLIFUE CF AFW DUE EVENT DATE (51 t E N-

.'*L'-L1' (6I) 10 29 2002 2002

- 00

- 0 OPERATING I"L I =5POPT Is S'ULI MODE (9) 1

{ 20 2201 Z)

LEVEL (10!)

100 20"221____,

120_21;_'!ta iI T

20 2 '23t).2)(iI

- 1220 2201fe) jiv)

LICENSEE G'_

SUPPLEMENTAL REPORT EXPECt ED (1-SI YES (If yes. complete EXPECTED SUBIN.S 1O0 DATE!

ABSTRACT (Limit to 1400 Spaces. I e. approx'Mr.tely 1" sngle-c On October 24. 2002, while conducting post mainten; recirculation flow was slightly reduced Initial investbgý line from the pump discharge to the condensate stor="

and evaluations, NMC concluded on October 29. 200 common mode failure mechanism to result in the plul pumps This Could result in the loss of safety functoi inadequate flow existed in the recircJlation line to pre made on October 29, and interim compznsatory mea completed which restored the AFW system to operat changes and training for the operators Analy'sis and mode and assessment of the safety significance of tt evaluations will be provided in a supplement ' - tf-s L

.. TG t. -,1! ý 1J.1,*.l

-- Ni "U.N fh-,,*i*~'0jY I

"*1' I*,.J.J.~ =.**,

,-h

, t, O

,"J

-'n,. r ccrr 1 r, d " rioi U,."

i #U'er

.i, C*" A h; O 34_ IfO lr nim.'f lhlL *~\\'

'C,

3

.0-0

- I 1-10 rn~~~

1 1T',i

- 4 bf-A~F' I

05o00 L

W t :t-o-3 1

To p/-RT'-,,_ CLCGII4G OF PECIRCULATIOiH (JRIFIOES PEPR~rIEi4 Hr~ ;AC-~10iF.5 IiiOV5 (r)___

ICI-L.

.~M 777ii'.7 WiUM*I.

I.:,

r, y-.

Point Beaclh Unit 2 05000301 F -107 I- -I....

12 2u 2002

()5 0

[rE, PUP*,UTO 1H. REOUtirEMENIS OF 10 CFR, Clie* "i tha!,r, i lii 20)50 2._.'".73,0

)2 60 7C 731: 2,,,iAi

?.h,=

50.. 'l2!d 0 731LIL2.1ýj...

r3 3efc V
,*Ai LA 50 "5';i)21 iv(A 7371 -fly"l 50 36tt..

1 5A S0 73: a(2)(':t(A) 73 71(a) (5) 50 74(')j2'i)rA1.

7'l 5C."3(aUl('2-v]*D Form_______

50 7i C 2

)(iC.

50 73.()(2)(vKP).

50 7*.,)Z2l',,l(A)

(073aL2(vi}(D)

- D NTACT r-:R THIS LER (121 paced typewritten IhneS) i16) tnce testing of the Po36A motO driven auxiliary feedwater pump.

lions discovered that the flow restricting orifice in the recirculation ge tanks was partially restricted. Following engineering analyses

2. that the potential existed uwder specific conditions for jglng of the orifices irt the recirculation lines for i1, four AF-r kif the dischargc from the AF5V pumps were throttled and

- lude pump failure due to overheeiing An EN-notification was sures cons'stnn of crew briefings and informatior posting wee I-status. Addi:ic"na, actions included temporary procedure evaluation of 1, c bJsceptibility of the AFW syster-i to this fa*ive is postulated condiLion are continuing The resi't. -f those

- R

6E:B80 E00E-02-:ia r~n~rr..i~3~L 1

,-,LL.

i, N T1 I.I:

.r-f- ;

j Point Beach Nuclear Plant Unri: 1 TEXT (if morc 0"I~

Event Descririon:

At 10:27AM CST on October 29. 2002 with boll, units [BA] for the Po.nt 2each Nuclek.ar Plant,PrPN'), Uils inoperable d',e to a concern for a singlc-mechanisn t, specific con-iticns.

[The concern f:,r tlii. c

,:non r i extent of coriditio, eva~uation foi, i.* reduced retir..,:

observed during post mainienmncat sur~eill]nze testitid During that test, :he rectr flaliori lne flow was ob~erv line is approximately 75 gpm. Tht rrin rurrn art. epti,'

discrepancy was documented Ed IL' 0111-C;Vc i' the. PEN.

venting of the flow transmitter ait,,ecahlib-.ticn of the tested again: howvver, the obser,- c recirculation flow recirculatio i flow orifice [OR] v as ieiviovod and inspec that appeared to be corro-Ton parliclet.

The AFW flow restricting onfic,' use a multi-stage an [FCV] to limit flow. This style *; o.fiCe a liuo% restrictc modifications over the past few yearE to aectlfy riip!,ig flow rostrictor uses very small channel shaped holes torturoJs path to limit flow and prevent c?',talion. Aft in 24 of the 54 holes in the outermost sletve. No a'di of the particles removed from the orihce were retaine.

at the orifice location revealed no evidence of debn.

and the P-38A AFW pump retested ut-ig procedure I Valves (Quarterly)" This test was succe-sfully compli was also successfully completed on the c.her three A were back in service at 1206 on October 25, 2002.

During the next several days NMC personnel evaluate cause evaluation was iiiated with specific directions action plan wet. developed to identify The sour.t: o. the other testing or flushing would be requio:l to.st ure tt the AFW system was not in question because of the r verification of recirculation flcws on October 25, 2002.

As the investigations co-ntinued, questions developed its safety related water supply, the service v,

syste basket strainer [STR], it was recognired that th,. strair These concerns culminated in a meeting early on Octi reasonable assurance that operation o; Lhe AFW sysit result in potential AFW recirculation o:ilicc clop;inog fr.

determined that it may be possible, allhough u`hiil.ely, 1 of the four AFW pumps, to re.trict the flow through tIN hypothesized that if the discharge valves for the A.FV,'

the recirculation line to avoid ovei henting the pumps.

At 1027 on October 29, 2002, all four Ar W pumps we required action 3.7.5.2.1 wnich directs imrnmediate acti:

corrective actions consisted o' :-iefing the orn-shitl cre e=oI

.1~5 r3~~~- or:,,

operatic il iut pb,,,,er. tl.

. daary teed walcr (AFW) system 1aid 2.,.~,.-: dJct~rzcd in,.;;':

e.

The systeirr wos decl* e" resul: iri ine failure of zll four cf the AFW pumrps. JPJ uri.or re ia.u,

'enititlei by NIMC prrsonnel vAh;lC-conducting en

.t,on io,:" on W! P 30A A!,FW purmp. This recu-ec fltw W,,qs

)of ;1,t P-'J$S,. mnoto dliwen f.r\\W pump or, O:tober 24, 2002.

ýd to t-a-:,ro, irnawl)c 64 gpmn. Normal flov, 0oi this recitculation Ibo~

fo

,h. pump by the tst oro-edure is 70

.pm. This P corre,'twe ac*,ior progjiarn (CAP 29906). Afien addituonal

[!ow iistruerrn' F-T]. the P-3E., AFW pump was started and v,; s e*- (?,, 1 unchanc L-c Fotlowing that lest run the ted. T -. irsprctlion revealecd ocbiis in the flew restricting orifice

ýi-:.vitetion trim [.-.kag-e installeo in the body of c, globe valve ii was installed in i!,,/..-V recirculation lines by plant wroblerrs releted to ci.viiatioo. ca the old orifices. Thls type of approximately, 5 niils by 90 ills) in each stmae along wi-,h a iremo\\,al ol the or-ficc internals. rartial bloi:l-age was observed tiorial p,*.ri-les wie* fcjind on any of the inner sleeves. Samp.es for analysis. A boroscope inspection of the recirculation pioing Following cleening and,eassembly, the orifice was reinstalled

- 10, 'Tes'. of Elec:-ically Driven Auxaliay Feed Pumps and

ed wi,' an Idic.'led recirculaton flow of about 75 gpm. Testing "W pure;':, I verify acceptable recirculation flow. All fnu, pumps d the it,-.alions of the orifice plugging event. An apparent [o

L.ssec-s and evaluate the potenitial extent of condition. An foreigna material found ir' the flow orifice and tc determine what iat future plugging did r-* occur At this time the operabnlity of

C it opcr Ct-1ig ex:,erience with the purmps. F'id the successful "onlcemi-g the operability ot thF AFW system wh;le supplied by

`(I [BI 8*)lthough the service water supply is piovided through a er mesh is W/C inch and the orifice channel hoies are much fine:

ber 29 at which N'MC concluded that there was no longer a

,rn on i*ts safety related suction sour; e of service water would not rn service water d.bnis. In a,:,,rwi ca$,,e -cenrnotl, Wlfi/

or each of the four flow cont-orifi:es, cachi associated wvith one "ssoclted recirculation line. Un- *r such conditions, r' is purnps -.re throttled, adeouati flICe, may be utiavai:able through an pump da-niage coul,' oc=.'r

" eclref inoperable. Soto units entered TSAC,.7.5.E and

)n o re:t1 re ;&n /--W system,to operable styus !-nn-iedate A, of the po~ontial corinequences of restricti,: reci;.laion flow.

=



NAC FORM 363A (7-I)0, 1)

d

%86 C

". C Y::.'

SY

?E!jT

,. P

• .-,,,ON 1 I G'

IC rACLI) 4'11.)Lr n2; !1 LEP I'JUMBER' I ACE.

IIA-Ii s6CiU[-rJTIAL P:i C H Point beach Nuclear Plant Unit 1 1

05000256 tjuM&E r iv&UM 3 OF 5

~

ir 2~0,')2 003 00_

i The operators were also directed to sect I e a rurinino AFVV pump f.lie pump d*liclFirge flows should be decreasceJ to less than 50 gpm for the mot; cirive pur,.ip, u, 1 rjopin for thie turirie driven pumpb. These flow rmtes are substantially above the point at wricti pump d~rni,'

could occu-Information tags were placed at the AFW purno flow indicators [Ft] on the main control bozros d cnnicy tI at rtfo-niatcn Triese actio i.. wi$,e completed at 1305 CSr At that time, with these admirr.-trative centre.,. ir, place iMC declared the AFWS o*,,...a:)le. An incident investiga.xr was

-,.r 11'.

fs,,r,,r hn,-

nnn wth !ih. Licoverv of the P-36A AFW pump ilnitiate Ito.collecL a[In IL 1liii 1 ULIU O,,.

V.I U4I Z, I-,

degraded recirculaton flow during p,st mriintcnai.nce system inoperable In accordance with 10 CFR 50.72(b)(3)(v) 2n ejht rc October 29, 2002, for `Any event or conditlon that at safety function of s:~uctures or systems haVt are need consequences of an accident"

Cause

A multi-discipline e~ent resolution team was appointE of this condition. Activities included initiation of a roo causes for the postulated cornmion mode failure that rates The RCE has preliminarily concluded that th reached erroneous conclusions based on unverified design functions being omitted from the zsfety evaluz The RCE further has identified that another modificat recirculation open function to safety-related, which w*

susceptibility of the recirculeaion line onfices to plugai pressures resulting from inadequate planning, combi a safety function upgrade), may have contributed to components.

Corrective Actions

es',ing Eind conciurl iig with lh'ý. diecisiort to declare the F jr EIIS noti*icztion (Lii.'39330) was made at 1711 CST or, he tirnc of ar..covcry could have prevented the fulfillrnen" of the

!d to. (5) Remove rriduail hoet... or (D) Mitigate th,..

J to identify and resolve the issues associated with the discovery cause evaluation (RCE) to determine the root and contributing Vould render all AFW pump recircu;ation lines with restricted floe,,

Sinadequate design resulted from a safety evaluation that iformation This resulted in key information regarding important Lion.

3n, untoated to the orefiCe modification, to upgrade the AFW/N s completec earlier this year, also did not evaluate the ig. The RCE initial assessment indicates that time and schedule iec with an evoluilon that was infrequently performed (specifically ri i*adequate design review of the AFW recirculatior line Immediate compensatory actions to restore tne operbility of the AFW system were identified in the Event Description Interim Corrective Actions included On coming operating crews were briefed on I AFW pump forward flow or to srcure the pur An operability determination was completed operable but non-conforming because the AF available under all operating transient conditi Changes were made to affected AOPs. EOP flow is maintained thro.igh the AFW pumps c November 7, 2002 Just-in-timr.

operator training on Ihe procedul sequences of interest was conduc(ed for sck November 9, 2002.

'ns potential failure mode and the necessity to maintain adequate ips 1[ 1850 on October 30 which co-icluded that the AFW pumos were W pump recirculation paths described in the FSAR may not be

)ns otht-" critical procedures to ensure that minim um forward r toe pumps were -:ecured. These changes were completed on e changes to estahlish appropriate operator guidance for accident cttd licensed operators prior to assuming the watch starting on

1.-.-

---

:80 E00E-07*-D3a

ii NJAVil Z

coiJruW LLRUMt3E-it r~

(°--*

1-

! G UE4TI;,_ '

t:..

I Point eeachi Nu',4 r Plant Unit 1° 0

1 0-.

TEXT (It m:,,e.B:*ccuz*f*.LUe:.ar e, i.i

• q ;,n/

w= r, I

( 1: j An independent evaluation rif t*Ic prt.,:(.dure ;ihariu.c tIc, acequaziz. of V,e briefings anc tining orovided tc the crews, and the effectiveness --I the

Ier, po, ar intormablin tags was corrpietced 0

An objective evaluation of th, u-sisio,- to dec on October 2c was also cc,

,eted An assessment of flow re,tricting devices ti I of the other saft:ty related i*c.

rf-strictino de%

clogging.

lore tre AF\\'.' sy-tOe, opa.rabic after taiinc the immediate ar.t,',r:

sen safety relatzc applicaiorv at PBNP was completec

' IV ci.a at PBNP wej fround to be Fuceptib:e to small particle Additional corrective actions proposed or JiiCorwzy irdclude.

Evaluate hydraulic system response to determ' ie if tite onfices could actually becoane plugged Evaluate a redesign of the recirculation ithI., c,,ttces wirth an aperture size of grF,-,'er than 1/8 inc I.

Evaluate the AFWsj -tem to determine the source uiltne poteriral corrosion produc.s.

Revise training materials and review the licensing ba4is.locuments to ensure that ley accurate'), describe the AF.,'/

recirculation I'ne design functions during accident cor ditions Other corrective actions identified in the completed R corrective action program.

Component znd System Descri-tion:

'E will be entered into and treacked to completion in the PBNP The following component end system dec-ription con es from Section 10.2 of the PBNP FSAR The auxiliary feedwater system consists of two electrl suction and discharge pip;ng, and the controls and ins is provided by utilizing two different pumping methods of water supply to the pumps The AFWS is categoriz will not obstruct the system function One AFWS water source uses a steam turbine-driven from either or both steam generators [SG]

Each turb its dedicated unit, or 200 gprri to each steam generatc The feedwater flow rate from the turbine-driven, &Fxhliz motor operated valves (MOVs)

Each pump has an A tanks to ensure minimum flow to dissipate pump heat from cold standby and is directly connected to the pun isolation valves between the turbine supply steam hea isolation valves The turbine and r mr) are normally c from the firewater system [KP]

The other AFW source is common to both units and u electrical power from the plant emergency diesel gene capable of supplying the "A" steam generator r. either normally closed MOVs and with the other pump capat through an AOV back-pressure control valve and norn

, motor-driven pumps, two steam turbine-driven pumps. pump trumentation necessary for operation of the system Redundant) two different sources of pov~or for the pumps, and two sources Wd as seismic Class I and is designed to ensure that a single faul:

purip for each unit with the steam capable of being supplied ne driven pump is capable of supp:ying 400 gpm of feedwater to r through niorrrially throttled molor-operatec discharge valves ry feedwater pump oepends on the throttle position of these OV controlled recirculatio-line back to the condensate storage The pump drive is a single-stage turbine, capable of cuich starts ip. The turbine is Itarted by ovening either one or both of tl',o den anc the main steam liner, upstream o' the mari steam

)oled b-service water with an alternate sour.ce of cooling water L

3ottwo similar motor-driveni pumps each capable of obtaining itt, rat rs Each pump has e capacity of 200 g;m willt one pump or both units thi oucr an AOV batl--pressure co'irol valve" and le rif supplying the 'B" steam generator in either or both units ially closed MOVS Nlr., "FORM 3 A (20f. J1)

- _ýE':Be FOCE-K-Dau t

LId

-'I-S UuC FORM 3tA U

oS N'C r

l 01,'-*B,-"c'r."

'i.j (7 2-t)

LJ L'*I*

£E*

7.*':

J pj.,,,.'r., n,,"

,E t).

TEX"I

'NI'TNU/-V ION

-. FACILITY 14AEIAF OiilI ii1~c ~

LEA NUMCPt fiA 4

Point Beach Nuclear Plant Unit 1 05000206 W42ER IJUJOER f5 Or

__ _ _ _I I

0 0 3 Both back-pressure control valves fail open vl;en instruument air to thv aahes is Io,.t The discharge valves are proviccd with a backup nitrogen supply to provide pneumatic ptessure in tne event of a loss, of instrument air This backup supply assures tVat the discharge valve, do iot mo-,* to the fL',l open pcsit;on vncr.h, combined wth low steam generatur pressures. may cijuse the pump motor to t1ip on oer-currerit due to higrn flow conditions. Each pum-, has ai AOV controlled recirculatoon line back to the condensate storage tanks to ensure rminimum flow to prevent hydraulic instablities and dissipate pump neat The dischtzrge lieadors also provide pipil ig, valves, and tanks for chemical additions to any steam gert rator The purrip bearings are ring lIubricsted and bearing oil is cooled by service water.

The water supply source for the; auxiliary feedwater sý norrinal capacity 45.000 gallon condensate storage t(

plant service water system whose pumps are powere Safety Assessmont:

As part of the event resolution activities associated,vt expert contractors, is evaluating the AFW system hyd given realistic system operating scenarios. The NMC evaluating the risk significance of the potential commi will be needed to complete the probability analysis to system suction from the CSTs or service water. Thes previously, analysis of the corrosion products found in The results of these analyses and our conclusions coi supplement to this LER.

Similar Occurrences:

A review of recent LERs (past two years) identified th(

function involving the auxiliary feedwater system.

LER NUMBER 266/2001-005-00 26612001-006-00 Title sterm is redundant 1 he normal source is by gravity feed from tAo rnkc (CST) [TK], while the safety-related supply is taken from the I from the diesel generators [ElI if station power is lost

,h this postulated event, NMC. with the assistance of outside "aulic response to oetern*ine if the orifices could become plugged piDbabilistic risk assessment (PRA) engineers are also in mode failure identified in this LER. Additional analytical results le1ermine the frequency of orifice plugging assuming AFW c items include the hydraulic response determinations mentioned the onfce, and the analysis of CST and service water sediment icermning the safety significance of this event w.11 be provided in a following events which involved the potential for a loss of safety PRA Assessment of At1 xlfary Feedwater System Reveals Procedural Inadequacy Related to Loss of Instdument Air Appendix R Requirem nts Not Satisfied for Unanalyzed Fire Induced Damage to the Auxiliary Feedwater Sy tern rWC FORMt, 30,0A (7-2001)

GE : Be TEXI