ML20042F326

LER 90-005-00:on 900404,intergranular Attack & IGSCC Results in Both Steam Generators a & B Being Categorized as C-3.All Defective Tubes Plugged & Sludge Lancing & Crevice Flushing conducted.W/900504 Ltr

ML20042F326
Person / Time
Site:	Kewaunee
Issue date:	05/04/1990
From:	Evers K, Webb T WISCONSIN PUBLIC SERVICE CORP.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
CON-NRC-90-54 LER-90-005, LER-90-5, NUDOCS 9005080173
Download: ML20042F326 (7)

Text

. .

NRC-90-54 WPSC (4141433-1598 TELECOPIER 64141433-b544 f ASYLINK 62891993 hCONSIEYuaUd~siRMCEY6EM655Ild5 600 Nort.h Adams

• P O. Box 19002

• Green Bey.WI '07 9002 I

May 4,1990 10 CFR 50.73 U. S. Nuclear Regulatory Conrnission Document Control Desk Washington, D.C. 20555 Gentlemen:

Docket 50-305 ,

Operating License DPR-43 Kewaunee Nuclear Power Plant Reportable Occurrence 90,-005-00 The attached Licensee Event Report for reportable occurrence 90-005-00 is being submitted in accordance with the requirements of 10 CFR 50.73, " Licensee Event Report System."

Sincerely, 4

K. H. Evers Manager-Nuclear Power PMF/jms Attach, cc - INPO Records Center Mr. Patrick Castleman, US NRC US NRC, Region III q 1

, j 9005080173 900394 fj.h (

gDR ADOCK 05000303 PDC ,

f

. l

r-

...,,.. ,, e ~c i t . . .t . . .. , c .

&#Ph0vl0 Oest a,0 lito-eies LICENSEE EVENT REPORT (LERI "*" "'"

. . cit.. . . t n ,

ta.4 i viet. a, - - =

Kewaunee Nuclear Power Plant o is I o 10 I o G 1015 t lorl016 Inter raranu' ar Stre BothkranulrAttackabdIntbategor'zedasbsCorrosionCrackingResultsin teambenerators eing -3 6 Wikt Daf t it tin s:Ja.bd8 set ht#0011 Daf t 178 .YMt t 8 hC,4,Titt ,ervotytD it, u% f m par vtan vtau '8[*M' h*L i IQ$ w0ert a Day . tam 8 8C'L't . nault DOCat t mvwet a gi N/A o 161010101 i i

~ ~

Ol4 014 90 9}0 i...e, 0 l0 l 5 0l0 0l5 0l 4 9l0 oi l l o io f oi l i

....,,o i u .mo,.Iv..,,,o I.iov,.t.t r...itc. ire... .. ~. ,nu

'a" = u n== n. a n an., n , ..

g _

m mi.iniva m mi.in, m n weim nnm

,,., , io = = mn,-

a e, nn.,

.n...,,. r gg ,7,,.f; g.

.I ni.. ,,,a

~~

. .. n.n n., ,

~

n inn t

1. u nmi. m n .,an n., Tech. Spec.

~

n amn n., m n...n. . ni.nt. .. 4.2.5.a & 4.2.5.c tics.sett gosetect poa tuis Lam ng, ahtscoDt Tom J. Webb - Plant Nuclear Engineer CO Pitti Ott Li48 80A R &Ces CO.spotte,t 84149 4 OttCastt0 su teset 808001#13' 4li i 4 38 i i Bi2 i i S60 i 1 C. vet telttw C0we0Ng , we aC R i,8 p 0,#,t,a C ov64 Sv8?tW COU'Ohth? N 0 Tg0,",','[tL8

• B AB i StG i i Wili 2:0 Y i i i i ~ .;

I i i 1 I I I I I I I I i t 1 l l 7:

everstantavat atoont q ueletto na, uowtm car vgan 7:n m , . emeno svewwo= o.re, T] o sve.'uio= <

.=,..r,n-...,..,,.....,,<.....,n., " "* N / A 1 1 I At 1810, on April 4, 1990, with the plant in refueling shutdown, eddy current inspection and plugging of the steam generator (SG) tubes were completed for the 1990 refueling outage. The inspection found that 97 tubes in SG A and 75 tubes in SG B met the Technical Specification definition of defective. Since the number of defective tubes exceeded 1 percent of the total number of tubes inspected in each steam generator, both steam generators were categorized as C-3. As required by Kewaunee's Technical Specifications, the Nuclear Regulatory Commission was notified within 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> of determining that a steam generator was in the C-3 category.

e The majority of the defects are assumed to be caused by intergranular attack and outside diameter intergranular stress corrosion cracking (IGA /lGSCC).

All the defective tubes were plugged. An additional 25 tubes in SG A and 34  !

', tubes in SG B were plugged as a preventive measure. To ameliorate the effects of IGA /lGSCC and reduce the probability of further tube damage, Kewaunee has implemented on line secondary system boric acid addition, low power soaks with boric acid in the secondary system, crevice flushing, sludge lancing, and annular searches, in order to further characterize the tube indications, portions of two defective tubes were removed from SG B.

i,".*3,'" "

, i.e . vi evem eisv6. . co . ,

LICENSEE EVENT REPORT (LER) TEXT CONTINUATION .w.ovio o e =o v o .oio.

. . . .. < s e v ,,

..c,6. . n, com e avao + 5....,., ..o u, m " tta.* ' -

'ff.t:

Kewaunee Nuclear Power Plant 0 1610101013 1015 910 -

01015 -

0 10 0 12 0F 0 16

,m ,, . e m. ., n n Description of the Event At-1810, on April 4, 1990, with the plant in refueling shutdown, the inspection l and plugging of the steam generator [SG) tv' 5 [TRB] were emnpleted for the 1990 refueling outage.

The SG tube eddy current inspection program included:

1.

an inspection of all the unplugg'ed and non-repaired tubes from the hot leg side through the first tube support plate on the hot leg side (2701 tubes),

2. an inspection of 62.2% of the unplugged, non-repaired tubes through their  !

entire length (1679 tubes),

3. an inspection of 56.5% of the unplugged repaired tubes through their '

entire-length (2055 tubes).

In addition, selected tubes (including samples of degraded tubes, defective tubes, no detectable degradation (NDD) tubes, and Row 1 U-bend tubes) were ,

inspected using a motorized rotating pancake coil (MRPC). The MRPC inspection was implemented in an effort to characterize tube degradation and to supplement the bobbin coil probe inspection results. The MRPC inspection .'ound indications in the hot isg crevice region in tubes that had been identified as NDD tubes by bobbin coil. The results of the MRPC inspection were presented to the NRC in .

references 1 and 2.

• f The Kewaunee Nuclear Power Plant Technical Specification (KNPP TS) 4.2.b.2.a -

requires that the initial inspection include at least 3% of the non-repaired l

tubes and at least 3% of the repaired tubes in each SG from the point of entry

! around the U-bend to the top support plate on the opposite. leg. Since this  !

I t

year's inspection program resulted in approximately 62% of the non-repaired tubes and 56% of the repaired tubes being inspected through their entire length (see items 2 and 3 above) the program satisfies the TS requirements.

. i l The inspection found that 7.2% of the inspected tubes in' steam generator A (97 r tubes) and 5.5% of the inspected tubes in steam generator B (75 tubes) met the i

KNPP TS definition of defective. The steam generators at Kewaunee are r

! Westinghouse model 51 with mill annealed inconel 600 tubes. Since' greater than l 1 percent of the inspected tubes in the hot leg crevice area in each steam

generator were found to be defective, both steam generators were categorized as. -l C-3. The C-3 category requires:

1. prompt notification of the Nuclear Regulatory Consission (NRC),

i 2. a written followup to the NRC, r

b C 0 4 2..

e..

*". vs ucts..ne.v6crom,

, UCENSEE EVENT REPORT RERI TEXT CENTINUATCN .wovio o =o vio co.

..cio,. 4. n , nei.r ev =

oocan =veia m 6... . . , . . , ,

Kewa'.: nee Nuclear Power Plant ,,.. ....a....

~" . .p' vm . . e % .,m I I I lI I -

1I -

010 Ol 3 0F 0 16

3. plugging or repair of all detective tubes,

4. an inspection of additional tubes in the affected areas if the initial sample size is less than 100% in the affected area,

5. increasing the required steam generator inspection frequency to once per 20 months.

When SG A was categorized as C-3, the NRC was notified at 1900 on March 17, 1990 via the emergency notification system (ENS) telephone. When SG B was categorized as C-3, the NRC was notified via the ENS telephone at 1700 on March 28, 1990.

Both notifications were made within 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> of categorizing the SG as C-3. This licensee event report is supplied as the written' followup.to the initial notifi-cations. As described later in this report; all defective tubes were plugged.  !

Since all the unplugged non-repaired tubes were inspected to the first support plate, the additional inspection requirements specified by Table'TS 4.2-2 were satisfied. The steam generators will be re-inspected in the Spring'of 1991 during Kewaunee's annual refueling outage.

The steam generator tube inspection and plugging results for the 1990 refueling outage sre sumarized in the following tables.

No. of Tubes No. of No. of No. of ilugged as a Defective Tubes .!

SG Defective Defective Preventive Removed for -!

Tubes Tubes Plugged Measure Analysis 1 A 97 97 25 0 B 75 75 34 2 i

i 1

ga4.oa a 1

i some own anna

'*". u a mucttaa as;utitant consmanand a LICENSEE EVENT REPORT (LER) TEXT CONTINUATION a aovio o e =o vie.oio. ,

sie,ais ev 8acs6str =Amt ni ioccast muestia sas Lee asunspea ici pagg igi

'saa " b'X." 'tf.i:

Kewaunee Nuclear Power Plant o ls to j o jo 131015 910 -

tem . .as .ac w an.wnn 0 i O! 5 -

Ol 0 0 14 0F 0 16  !

t The defects in SG A were located in the following areas:

Area Number of Tubes Percent ,

Hot Leg Crevice 68 70.1%

Top of Tubesheet-Hot Leg Side 7 7.2% lt Hot Leg Support 15 15.5% ,

Plates Cold Leg Support 7 7.2%

Plates TOTAL 97 100%

The defects in SG B were located in the following areas:

Area Number of Tubes _ Percent Hot Leg Crevice 54 72 %

Top of Tubesheet- 10 13.3%

Hot Leg Side Hot Leg Support 6 .

8%

Plates

, Cold Leg Support 5 6.7%

i Plates -

1 TOTAL 75 100%

Cause of Event '

The majority of the steam generator tube degradation at Kewaunee is assumed to be caused by intergranular attack and outside diarreter intergranular stress corrosion cracking (IGA /IGSCC). This assumption is based on eddy current response and on industry experience with steam generator tube degradation.

IGA /IGSCC is usually associated with a restricted geometry; e.g., the tube sheet crevice or a sludge pile, and with a caustic environment; i.e., a pH greater than 10.

L l

l g3.a.. ,.a.

l l

' ~ - - - - - - - - -

e . . me.

• • ", ve avean cowwonv ses.ener UCENSEE EVENT REPORT (LER) TEXT CONTINUATIDN maovio o=e ao sm-o*

laceptV48.#4In ttp ass g 3146 Dottii wvesten m

- tem nuest4R m 96 4 m pu "t%P "'2.n Kewaunee Nuclear Power Plant 015 lo Io 1o l 31015 910 or 0 16 run. . .c w m wim 010 l 5 -

0IO O15 Analysis of Event ==

This report is supplied in accordance with TS 4.2.5.a and TS 4.2.5.c which require a written report to be submitted to the NRC within 30 days of completing the steam generator tube repair and plugging.

]=

The following table provides a historical summary of the number of SG tubes plugged each year.

SG 1983 1984 1985 1986 1987' 1988 1989 1990 Total 2 A 23 9 26 26 44 27 21 122 298 B 50 17 22 46 79 26 31 109 38C g 678 in addition to the plugged tubes,'3638 tubes were sleeved during previous '

outages, resulting in an equiva %nt plugging percent of 10.9% in SG A and 13.4%

in SG B. A safety evaluation, h,cluding the transient and loss of coolant acci-dent analyses presented in Kewaunee's Updated Safety Analysis Report (USAR), was performed assuming a plugging level of 13.9% per SG. This safety evaluation demonstrated that this level of plugging is bounded by Kewaunee's USAR;-there-fore, operation of the plant does not represent a significant hazard to the health and safety of the public.

Corrective Actions In accordance with Kewaunee's Technical Specifications, all defective tubes were plugged. In order to minimize the possibility of primary to secondary leakage during the 1990-91 operating cycle, fif ty-nine other tubes were also plugged as a preventive measure. -

Sludge lancing and crevice flushing were conducted during this refueling outage to reduce the amount of sladge and to remove contaminants from the tube sheet crevice. Also, in an effort to reduce the caustic environment in the tube crevice and prevent tube support plate denting a secondary system boric acid' -

addition program has been implemented including boric acid soaks at low power. -

levels and on line boric acid addition at normal power levels. A secondary side annular seerch was also conducted to identify and remove foreign' objects, which could damage the SG tubes. "

.In order to further characterize the inditations, portions of two defective "

tubes were remo'ed v from SG B for laboratory analysis.

~

o su

J .  !

..o . ..m.m............  ;

, LICENSEE EVENT MEPORT (LER) TEXT CONTINUATION ....ovio o ~o d w . l l

......i,, ..,-.o,  ;

,,.. ......... . . .o-Kewaunee Nuclear Power Plant -

ru, .

.e w ar., nn o 16 t o lo lo 13 l 0J5 910 -

01015 -10l0 0 16 or 0 16_  ;

. i Additional Infonnatioit i Equipment failure Westinghouse Model 51 steam generator tubes. The tubing is  ;

m111 annealed inconel 600. '

Similar Events:

1. LER 89-007, Intergranular Attack and Intergranular Stress Corrosion Cracking Result in Defective Steam Generator. Tubes-

2. LER 88-001 Intergranular Attack and Intergranular 3

Stress Col.ssion Cracking Result in Defective Steam Generator Tubes *

3. Letter from D.C. Hintz (WPSC) to the U.S. NRC Document Control Desk, dated March 31, 1987. '

4. Letter from D.C. Hintz (WPSC) to G.E. Lear (NRC)

, dated April 23, 1986. ,

5.. LER 85-06.

6. Letter from C.W. Giesler (WPSC) to S.A. Varga (NRC) dated May 1, 1984.

References:

1. Letter from K.H. Evers (WPSC) to the US NRC Document Control Desk dated April 6, 1990. -

2. Westinghouse WCAP 12558 *Kewaunee Tube Sheet Crevi'.3 Indications Returr to Power" ['

I s

D 9

. - . . - . . . -- .. -. . . - . . - - - - -