Text

LER 89-006-01:on 891015,steam Generator Tubes Found Degraded,W/Undefined Signal & W/Axial Indications in Tubesheet Area.Degradation Caused by Time.Affected Tubes Plugged or Preventively sleeved.W/891114 Ltr
	ML19327C200
Person / Time
Site:	Point Beach
Issue date:	11/14/1989
From:	Fay C; WISCONSIN ELECTRIC POWER CO.
To:	; NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
	CON-NRC-89-143 LER-89-006-01, LER-89-6-1, VPNPD-89-596, NUDOCS 8911210150
	Download: ML19327C200 (8)
	v • d • e

f ,F' {

i 9 !

G' V' ' WISCORSin ;

Electnc i POWER COMPANY i i

231 W Mctgm PO ban 204o. Mwa.*oa WI 53?01 (414)221 2345 L VPNPD-89-596 10 CFR 50.73 !

NRC-09-143 [

Noveinber 14, 1989 i i

U. S. NUCLEAR REGULATORY COMMISSION l Document control Desk :

Mail Station P1-137 t Washington, D. C. 20555 i t

Gentlemen DOCKET 50-301 i LICENSEE EVENT REPORT 89-006_QA -

DEGRADATION OF STEAM GENERATOR TUBES POINT BEACH NUCLEAR PLANT. UNIT 2 Enclosed is Licensee Event Report 89-006-00 for Point Beach i Nuclear Plant, Unit 2. This report is provided in accordance '

with Technical Specification 15.4.2.A.7(a), "After each inservice' examination, the number of tubes plugged or repaired ;

I, in each steam generator shall be reported.to the Commission as soon as practicable" and 15.4.2.A.7(c), " Reports required by Table 15.4.2-1, ' Steam Generator Tube Inspection', shall .

f provide the information required by Technical Specification 15.4.2.A.7(b) and a description of investigations conducted to determine the cause of the tube degradation and corrective ,

, measures taken to prevent recurrence." LER 89-006-00 is filed l according to the above table under the reporting requirement of 10 CFR 50.73 (a) (2) (ii) .

If any further information is required, please contact us.

l Very truly yours, 0

du C. W. a Vice President Nuclear Power l

l' Enclosure ,

l Copies to NRC Regional Administrator, Region III l NRC Resident Inspector 8911210150 891114 gDR ADOCK0500ggi gp i

A nk&qdkwsin DxvgrOmwkw

su ue aue6ename.964v.av m.sa.e=

g' n ioveoon.e.osieo4 .

UCENSEE EVENT REPORT ILER) e.ei me.n ai =

, ,,'1oint5 ,,,,,, o , Beach Nuclear Plant o I5 l o Ie i e 131011 1 lofl 017 mai m Degradation of Steam Generator Tubes sv.sv man a sp .vu . m , u n ni oi ea eaciutas ==veo =

.owi- n., n= vs a ==gg,*

3 wo ,. oav vein .*sisit =a.a oocu t av.***

015101010 1 i i

~ ~

1l 0 1!5 89 8l9 0l0l6 0l 0 1l 1 1l4 8 l9 0 isto io ioi i i

,,,,,,,,,, e . . .u rn. ., , o , .. .. ., i. c , . , ,c - ., - n u

=== . . . ..i . nm.n.i n.,i m yn _

. ini.

. s. ini, _

. nma n.i nin.i i i o . . in im

. . .i _

. n .i . _ =g,;.g,,,,

, ns :;e _

= ==n na _

.umima _

. 'anen-nai =

yy 1-

= =mn ni.i

= =mn n.i

.ssman.i

. nemum

..nm a n.n.i

. nma n.i tooe se e0= Tact ,04 Ts.t tem nti e na, o e =v ea aae a coo.

C. W. Fay, Vice President - Nuclear Pcwor 4 :1 1 4 22li i i i 2 i 8ll i l oe snen t . ene couname=, enitune oe.ca o m v . ee. oat nei Cav.e stettw Cou.obeht way=@c- efo A

gaggg , y ,y g , gou,og gi,9 ugp m & f;

,_ 3 A IB i IS IG Wili2 1 0 Yes i i i i i i i .

I I l l l l l l ,

I I I l ! l *

== ., t .. , e m en o n.,

=om nav vsaa

] vee t,, e e #x.ecreo stemmo= catas ] e,o l l l a .c , ,6 . .. . . = m ., .- , nei Unit 2 was shut down for Refueling 15 on September 22, 1989. Eddy current examination of the steam generator tubes was conducted from October 4 to October 15, 1989, using a digital :aulti-frequency l eddy current system. In the A steam generator hot leg, inspection results indicated 4 tubes degraded equal to or greater than 40% of the wall thickness, one tube with an undefined signal, 20 tubes with axial indications in the tubesheet area, and 2 restricted tubes.

All 27 of these tubes were plugged.

In the B steam generator a total of 7 tubes were degraded equal to or greater than 40% of the tube wall thickness, and 2 tubes had axial indications in the tubesheet area. Six of these tubes were mechanically plugged and the remaining three were included in the ;

sleeving program. A total of 298 tubes were preventively sleeved in the cold leg to address wastage concerns. I The 800 psid leak test revealed 4 mechanically plugged sleeved tubes 4 and two sleeves leaking slightly in the B hot leg while 3 other l tubes showed dampness. One explosively plugged tube and three i sleeved tubes were leaking slightly in the A hot leg. The leaking 1 mechanical plugs were repaired by the plug-in-plug repair and the i others were left as found because of the minimal leakrate (<1 drop /2 min) or the lack of any indications during eddy current 1 testing. The leaking sleeves were left as found as the sleeves are leak limiting by design.

g..

c..au v =ve6 a en:vato.= co=viisio L . LICENSEE EVENT REPORT (LER) TEXT CONTINum elON *=ovgo ows ao vio-c*

lape>Il 695 96 j ,

pace 6ste haast ete occa s t woestt a 6p' 48. huutt h as, 9669 13

. . . "t:l;;t- "'a* n Point Beach Nuclear Plant o plolo;o p p p B;9 _ 0 0j g6 _ 0 ;0 0 l2 or 0 l7 mn v . - e ., m.

EVENT DESCRIPTION 800 PSID LEAK CHECK Prior to eddy current inspection on both steam generators, 800 psid secondary to primary leak checks were performed in the hot and cold legs of each steam generator. The checks were performed visually with the aid of remote video equipment. The leak check revealed 3 leaking sleeves and 1 explosive plug in the A steam generator hot leg. In the B steam generator hot leg 4 mechanically plugged sleeved tubes, and two sleeves were noted to be leaking. Also, 3 tubes showed signs of dampness in the B steam generator hot leg. Leakage noted was less than or equal to 1 drop /2 min in all cases.

EDDY CURRENT INSPECTION SCOPE Eddy current inspections began shortly after the leak testing was completed. The eddy current program addressed the following items:

1. A 10 percent full-length sample on B S/G and a 9.6% full length sample on A S/G. (Technical Specifications require 3.0%)

2. Previously degraded tubes that had not been repaired.

3. A 10 percent sample of the tubes which had sleeves installed in the hot leg in each steam generator in 1983.

4. One hundred percent of the remaining unsleeved tubes in the hot leg to the first support plate in each steam generator, looking particularly for tube 5heet crevice corrosion.

5. A 10 percent sample of tubes which had sleeves installed in 1988 in the cold leg in each steam generator.

6. One hundred percent inspection of the unsleeved tubes in the B steam generator from the cold leg tube end to the first support plate for wastage and pitting.

7. A 14% sample of the A cold leg unsleeved tubes from the tube end to the first support plate for wastage and pitting. This included all of the peripheral tubes and those tubes in the area where wastage had been noted in previous inspections.

l jg}...o

m

== . m. . .ia . wato., com.m.a LICENSEE EVENT REPORT (LER) TEXT CONTINUATION .-novio o e no ow-++

e ...is ev en witn, m = .ii a m ia m 6...., .. . o l

.... 'u m ;:s w .n '

Point Beach Nuclear Plant ,p ,go;,} 9 1 0 f mn ,. . =ac w .,im 0pf _,

3f 0l 3 or 0l7 The number of tubes inspected and the extent of the inspections are as follows: '

A Steam Generator Number of Tubes From From '

Extent of Inspection Hot Leg Cold Leg f

Full length 138 Through U-Bend to #6TSPC 20

1 TSP to tube end 1420 435 ,

Sleeves 138 12 To Top of Hot Leg Sleeve 138

6TSPC to tube end 20 TOTAL 1716 605 B Steam Generator

Number of Tubes From From i Extent of Inspection Hot Leg Cold Leg ;

Full length 150 Through U-Bend to #6TSPC 21

1 TSP to tube end 1512 2229 Sleeves 141 48 To Top of Hot Leg Sleeve 141 '

6TSPC to tube end 21 TOTAL 1824 2439 <

c

1 TSP First support plate

6TSPC Sixth support plate cold leg side Inspections from the cold leg side were performed due to concerns '

with cold leg wastage found during the U2R11 outage. As a result of these inspections cold leg sleeves were installed in the B steam -

generator as part of an optional preventive maintenance program.

Steam Generator Mechanical Tube Plug Repair

-During this outage a total of 189 plug-in-plug repairs were made (65 on A, 124 on B) to address industry concerns, described in IE Bulletin 89-01, regarding certain Westinghouse mechanical plugs which were susceptible to intergranualar stress corrosion cracking (IGSCC). One hot leg sleeve plug in the B steam generator was removed and replugged following an unsuccessful plug-in-plt;1 inser-tion attempt in the original plug.

,.g. ... m.

s

, m . . as v sc. a . :v m o., s o.,

UCENSEE EVENT REPORT (LER) TEXT CONTINUATION **.c.ae owe =o vio-e+

i. ..is a mi

..c on n, oomi av . u, o . .,u . , ...i o

~u= " t M." "'22:

Point Beach Nuclear Plant e p;o;o;o p p p 3 ;9 __0 [0 l6 ._0 l0 0 ;4 or 0l7 vm m, . e w an..,nw A STEAM GENERATOR TUBES EXCEEDING PLUGGING LIMIT On October 15, 1989, review and verification of all eddy current data for tubes with indications exceeding the plugging limit was completed. A total of 27 tubes were plugged. Four tubes in the unsleeved region of the A steam generator were found having degradation equal to or greater than the plugging limit of 40% of the nominal tube wall thickness (Technical Specification 15.4.2.A 5).

In addition, 20 tubes having axial indications were identified using a magnetic rotating pancake coil (MRPC). Another tube had an undefined signal while two other tubes were restricted and failed to pass a

.650" probe.

The following is a list of the affected tubes:

TUBES THAT WERE PLUGGED Tube Defect Location Cause RSC4 MAI 5.9" ATE HL Crevice Corrosion R15C7 SAI 6.1" ATE HL Crevice Corrosion R18C7 MAI 8.0" ATE HL Crevice Corrosion R20C10 UDI 3.9" ATE HL Crevice Corrosion R37C28 SAI 8.6" ATE HL Crevice Corrosion RIC30 SAI 0.2" ATS HL Wastage R42C31 REST. #5 TSP HL Denting R37C33 78% 7.2" ATE HL Crevice Corrosion R42C33 REST. #5 TSP HL Denting R32C35 90% 8.6" ATE HL Crevice Corrosion R37C40 MAI 4.0" ATE HL Crevice Corrosion R37C52 85% 10.3" ATE HL Crevice Corrosion R39C54 MAI 4.1" ATE HL Crevice Corrosion R33C59 SAI 3.8" ATE HL Crevice Corrosion R33C61 MAI 4.1" ATE HL Crevice Corrosion RSC72 MAI 13.8" ATE HL Crevice Corrosion R31C75 MAI 2.8" ATE HL Crevice Corrosion R35C76 MAI 4.7" ATE HL Crevice Corrosion R6C77 MAI 14.9" ATE HL Crevice Corrosion R8C77 MAI 7.3" ATR HL Crevice Corrosion R9C79 SAI 10" ATR HL Crevice Corrosion R6C80 MAI 6.1" ATE HL Crevice Corrosion R11C84 MAI 2.3" ATE HL Crevice Corrosion R1C85 MAI 3.2" ATE HL Crevice Corrosion R10C85 SAI 1.6" ATE HL Crevice Corrosion R12C86 MAI 3.8" ATE HL Crevice Corrosion R13C89 80% 8.1" ATE HL Crevice Corrosion 1

ATR - Above Tube Roll SAI - Single Axial Indication ATE - Above Tube End MAI - Multiple Axial Indication ATS - Above Tube Sheet REST - Restricted 5 .650" Dia. Probe ;

HL - Hot Leg UDI - Undefined Indication TSP - Tube Support Plate E*d,' ** * *"

]

_y

==. .mu vi con ::. ci o c ,o. c = vimio.

' LICENSEE EVENT REPORT (LERI TEXT CONTINUATION ** .ovie owe =o a m -c +

e se,.s sv es

. won n, ooan aveen ie. . . . , . . . . , ...<>

u.. "h'd P h*.*1 : l Point Beach Nuclear Plant a p ;,9,;, p p p 89g _,

0 l0 ;6 0;0 o; 5 or o l7 ;

wri . . -- w<=-mu.,nw B STEAM GENERATOR TUBES EXCEEDING THE PLUGGING LIMIT In the B steam generator, 7 tubes were found with indications equal to or greater than the plugging limit of 40% and 2 tubes were found ,

to have axial indications as identified with MRPC. Six of these tubes were plugged, and the remainder (3) were sleeved on the cold leg side.

The following is a list of the affected tubes:

TUBES THAT WERE PLUGGED Tube Defect Location Cause R6C1 48% #1 TSP HL Wastage R6C7 SAI 3.9" ATR HL Crevice Corrosion R17C18 40% #1 TSP CL Wastage R31C19 41% #1 TSP CL Wastage RIC50 80% 4.1" ATE HL Crevice Corrosion R33C78 MAI 2.1" ATE HL Crevice Corrosion TUBES THAT WERE SLEEVED Tube Defect Location Cause R16C35 40% 0.8" ATS CL Wastage R7C50 41% 0.9" ATS CL Wastage R16C51 41% 0.8" ATS CL Wastage ATE - Above Tube End SAI - Single Axial Indication ATS - Above Tube Sheet MAI - Multiple Axial Indication HL - Hot Leg CL - Cold Leg TSP - Tube Support Plate The 1988 data from both steam generators was compared to the 1989 data to determine indication growth rate. The results are as follows:

1. In terms of tube wall thickness, degradation percentages and affected steam generator area, the degree of cold leg wastage at the top of the tubesheet in the A steam generator is less than in the B steam generator.

2. In the A and B steam generator hot leg, previous indications showed growth rates under 10% since last inspection in 1988.

However, several indications which exceeded the plugging limits have appeared in random locations, g,. o.. .

^

F' !

..e . . vi =se m a aes o p.tco==*s.oi. ;

"'. UCENSEE EVENT REPORT P.ER) TEXT CONYlNUATION ****ovie ove *o * -c * :

se.4:s eve 96ce6ef t osaani ni pocast wueelt 68' 9601 68 tie husste si

.t.. "tt;t- ?@ l Point Beach Nuclear Plant o p;olojop p f 3 l9 __ 0 p l6 0l0 0 16 0' Ob m . . . c % am. ., ni,

3. In the B steam generator cold leg, 5 tubes wit'h previous reportable indications required repair. Three of these tubes were included in the sleeving program and two were plugged.

4. The rate of indic . tion growth was about 8-10%, which is a slight increase from our 1988 average. -

COLD LEG WASTAGE AND PITTING ,

Tubes in both steam generator cold legs showed signs of being affected by wastage. The B steam generator has been affected more than A. In the B steam generator, 72 tubes (in addition to the 298 sleeved tubes) have indications. In the A steam generator, only '

5 tubes showed indications of this type. Pitting, which has been found at other plants, has not been found at Point Beach.

TUBESHEET CREVICE CORROSION Twenty-four tubes were found in the A steam generator unsleeved portion of the hot leg with signs of crevice corrosion. Three unsleeved tubes were found in the B steam generator hot leg with signs of crevice corrosion. All of these tubes were plugged.

SLEEVED TUBES A total of 339 previously installed sleeves were inspected (150 in A, 189 in B) with no reportable indications in either steam generator. An additional 298 tubes were sleeved in the B steam generator cold leg as a preventive maintenance measure.

PROBE RESTRICTIONS Probe restrictions were noted in both steam generators in the unsleeved regions. In the A steam generator, 66 tubes would not pass a 0.720" probe, 18 of these tubes would not pass a 0.700" probe, and 7 of the 18 tubes would not pass a 0.680" probe. A 0.650" probe was able to go through 3 of these tubes. Two tubes would not pass a .650" probe and were plugged. A .610" diameter probe was used to inspect these tubes and showed no defect. In the B steam generator, 58 tubes would not pass a 0.720" probe, and 17 of these tubes would not pass a 0.700" probe. A 0.680" probe was passed through all of these tubes. No tube had to be plugged in the B steam generator because of unacceptable restrictions. The restrictions in both steam generators appear to be a result of denting at the tube support plates in both generators.

l f

i

(

uoeu us.

m _ , _ _ _

rg, 4

e* Seem mea U $ LUCLilm C61UL1108V C78888860h

/ . LICENSEE EVENT REPORT (LER) TEXT CONTINUATION anaovio cas ao mo-o*

t apimit 84146 Eh f att6tTv essent sti Doca:T Nunesta u8 Les h6masta et, P&Of I vi a "em. - 2 33:

Point Beach Nuclear Plant n p go;ogo f p p B;9 _ 00;69 0 ;0 01 7 0F 01 7, varf n- . we % mu.nm SLUDGE LANCING Sludge lancing was performed this outage.

154 pounds of sludge was removed from the A steam generator and 102 pounds from the B steam generator. Routine visual checks with fiber optics were made to assecs the cleanliness after lancing. The visual check results were satisfactory.

MINIMIZATION OF TUBE DEGRADATION Other measures continue to be taken to minimize degradation of the steam generator tubes. These include crevice flushing prior to heating up to normal operating temperature and maintaining stricter chemistry controls in accordance with the prescribed guidelines.

PREVENTATIVE MAINTENANCE Wisconsin Electric continues to monitor tube integrity on the hot leg of each steam generator and plug those tubes which exceed cr approach the plugging limit in the Technical Specifications. In the cold legs, we are continuing to plug or sleeve tubes which exceed the plugging limit in the Technical Specifications.

o l

l l

l conw Mea

. . . . _ . -

ML19327C200

Text

Navigation menu

Search