ML20086C074

Suppl to Deficiency Rept Re Steam Generator Head Cladding Indications.Initially Reported on 760408.Cause Still Under Investigation.Ultrasonic Exam Conducted

ML20086C074
Person / Time
Site:	Salem
Issue date:	05/28/1976
From:	Schwalje E Public Service Enterprise Group
To:	James O'Reilly NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I)
Shared Package
ML20086C053	List: ML20086C049 ML20086C055 ML20086C074 ML20086C084
References
10CFR-050.55E, 10CFR-50.55E, NUDOCS 8311220549
Download: ML20086C074 (5)

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h Public Service Electric and Gas Company 80 Park Placo Newark, N.J. 07101 Phono 201/622-7000 Kf,7'.

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May 28, 1976 p.jg l

Mr. James P. O'Reilly, Director tJ03 fS h

l2:YV,'F U.S. Nuclear Regulatory Commission $d Y. 2 k Office of Inspection and Enforcement  % C . j

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Dear Mr. O'Reilly:

STEAM GENERATOR HEAD CLADDING INDICATIONS NO. 1 UNIT SALEM NUCLEAR GENERATING STATION i

DOCKET NO. 50-272 c Supplenentary to our verbal report of April 8, 1976 and pre- gm .

liminary written report of May 5, 1976 concerning indications bi?.g. y' - .

in the stainless steel cladding of No. 1 Unit Steam Generator ((;.c 'r J E Heads, the following detailed report is submitted in accordance h*[.:h,.J.:

with orovisions of 10CFR50.55(c).

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A Subsequent to our May 5, 1976 report, nondestructive examinations of the stsinless steel cladding in the heads of No. 1 Unit Steam kf j #91

.7 r Generators (11-14) were conducted using the water washable dye --/'j',%

penetrant method. The results of these examinations Along with P

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7 metallurgical evaluation using replicar, have been reviewed by Westinghouse at Tampa, Florida. These evaluations have not re- M*);l[O i vealed the cause of the cladding indications. A program for YQy,g

• • 74 ultrasonically monitoring a representative single area of clad-

_ ding indications in 'the cold leg of No. 14 Steam Generator is L f,,W,sg f planned, access permitting. If the studies show that these re- A;-

[ presentative cladding indications can be referenced successfully, %p.Q ,

a surveillance schedule vill be incorporated into the nuclear ((fy plant inservice inspection program. gig y p q. , w -

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c. s Mr. J. P. O'Reilly 5/28/76 EXAMINATIONS A. NDE '

Nondestructive examination of the Unit 1 Steam Generators (ll-lb) using the water washable dye penetrant method revealed -

extensive transverse and longitudinal cladding indications at ___

bead overlaps and within the weld beads on the No. 14 Steam Generator. These defects were concentrated at one location -

on the upper bowl of the cold leg side in an area approximately 2' x 4'. The other steam generators No. 11, 12 and 13 and the hot leg cide of No. 14 Steam Generator showed minor, randomly _

scattered indications. In addition, the No. 11 hot leg ~and j No. 14 cold leg have indications at the toe of fillet veld on , __

the cladding joining the partition plate, to the head.

Although there were some clad indications in the nozzle of -

No. 14 Steam Generator cold leg, and minor indications in

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other steam generator nozzles, there were no clad defects ta evident in any inner corner radii of the nozzle s.

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E B. FERRITE ANALYSIS 2, A ferrite composition examination was conducted on the No. 14  ?

Steam Generator within the indication (2' x 4') zone as well ^

O as in areas where dye penetrant found no indications. .

Starting from the top of the channel head bowl, at the junction .:

of the tube sheet cladding to bowl cladding, each weld bead O was measured for ferrite with a Severn Gage. A series of _

locations across the No. 14 steen generator, approximately .c-'

18" apart, were checked for ferrite level. Results of the  ;

analysis revealed that weld beads measured by the Severn Gage contained 3.5% to 12.5% measured ferrite. There was no significant difference in ferrite content between the areas -

with dye penetran.t indications and areas free from indications. -

C. MPLICATION h Four areas with dye penetrant indications were selected for replication of the surface condition. Replicas of acetate film were taken of the No. 14 Steam Generator cladding of the _

following surface conditions: -

(1) as deposited clad .

(2) polished clad (3) polished and etched clad.

• These replicas were examined at the Westinghouse Tampa Metallography Laboratory at 50 to 500 magnifications. The results show the indications to be fine, intergranular cracks.

O The mechanism explaining the formation and the d.ynamics of its propagation has not been formulated. -

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1 O O Mr. J. P. O 'Reilly 5/28/76

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EXPLORATORY GRINDING Four areas where cracks were present in No. 14 cold leg were ground to a depth approximately one-half of the nominal cladding thickness to avoid exposing base metal. The cladding is nominally 0.250", therefore the maximum depth excavated was 0.125". All explored cracks propaged into the cladding normal to the clad surface. The four ground areas were re-examined with dye penetrant.

Three areas following grinding showed the cracks still present, while the fourth area 2" x 3", where grinding for chemistry was conducted, was free of any dye penetrant indications.

CHEMICAL ANALYSIS An area approximately 2" x 3" in the cracking zone of No. 14 Steam Generator was selected for chemical analysis. Results of spectrographic and chemical analysis of the chips revealed the clad metal to be within the specification for all metallic elements.

The carbon content was above the specification, however, this could be traced to the particles of grinding cutter abraded into the sample.

CONC LUSION S

\-The work jointly conducted by Westinghouse and PSE&G has succeeded in defining the scope of the problem at Salem Buelcar Generating Station (No. 1 Unit). The transverse and longitudin'al cracking is concentrated in one area (2' x 4') of the upper bowl of the cold leg of No. 14 Steam Generator. There are minor indications in the No. 11, 12 and 13 Steam Generators as well as the hot leg side of No. 14. The investigation to date has not determined the cause of the cracking but it.has determined that the condition at Salem closely parallels the defects revealed in channel head cladding at Consolidated Edison's Indian Point No. 3 Huclear Generating Station.

The controlled investigation conducted at Salem by Westinghouse and PSE&G has shown that in one isolated area 2" x 3', the defects in the cladding were removed prior to exposure of base metal.

Exposure of base metal was averted at Salem to prevent extensive veld repairs which have been previously experienced by others.

A review of the safety implications conclude that the cracks in the cladding at Salem Nuclear Generating Station, No. 1 Unit are acceptable as the integrity of the system is not compromised.

The Boiler and Pressure Code allows cladding indications and the subject of surface indications in cladding is defined as part of Section XI Code Case No. 1738 (attached).

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O O Mr. J. P. O'Reilly 5/28/76 OCONCLUSIONS (Continued)

The intent of the code case is to verify that the cracks are indeed confined to the cladding and do not progress into the base metal.

This condition can be reasonably substantiated by ultrasonic examination of representative cladding defects.

l This inspection conducted on the channel head will attempt to:

l l (a) identify the cladding indications on the cladding surface from the 0.D. of the head.

(b) measure the thickness of the cladding in the vicinity of the indication from the I.D. of the head (c) verify whether the cladding defect has propagated into the base metal.

If successlul, the ultrasonic exc.mination will then serve as the baseline pre:ervice inspection of the steam generator cladding.

The cladding indications will then be monitored as part of the inservice inspection program for the life-time of the nuclear plant. This examination will be complete by June 30, 1976.

( )fhe results of these exaninations will be available at the site.

If you require additional information our engineers will be available to discuss the details with you.

Very truly yours, k N.bc '

i E.N. Schwalje Manager of Quality Assurance Engineering and Construction Department CC: Dr. Ernst Volgenau Washington, D.C. 20555

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, CASI AS.\1Eltoll.Elt AND Pltr.SSt;IIC VESSEL COI Approved by Council, December 22, I975 ,

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Case 1738 Examination-Acceptance Standarcis for Surface Indica.

tions in Cladding Section XI

• l Inguiry: Isit permiwihlc to accept surface indications in the patches of clad surf.:cea examined in accordance with Category 1:l.1 and I:12.Tahte IWl:"600,iretion XI, gmided that the dtpths of the flaws are within the cladilin;; material?

Reply: It is the oi. inion of the Conunit tee that surface indications in the i.atches of clail >urfaces, namined in accordance with Catep.ry it i 1 and 111-2. Ta!.le IWII.

2600,Section XI, may 1.e permitted and the acceptance stand.irds of IWit.3'217.1 n:ay be waised, provith d the depths of the flaws are within the cl.nhiin: material.The prosisions of this Case may not !.c applied for the exand.

nation of clad surfaces on the inner corner r.idii of nozz!cs.

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.Public Service Electric & Cas Company Docket No. 50-272 Attention: Mr. E. N. Schwalje QA Manager 80 Park Place Newark, New Jersey 07101

Reference:

Steam Cencrator Cladding Indications .

Salem Unit 1 Centlemen:

Thank you for your letter dated May 28, 1976 which forwarded a report pursuant to 10 CFR 50.55(e) regarding the above referenced item.

Please note that your final report of this matter must include the results of the proposed nondestructive examination of the cladding as stated in yor.r letter and any cther relevant information, such as your planned inservice monitoring program of the steam generator cladding.

Your ccoperation is appreciated.

Sincerely, lk{ Yr James P. O'Reilly

' Director a bec: .

IE Mail & Files (For Appropriate Distribution)

Central Files Public Document Room (PDR) -

Local Public Document Room (LPDR)

Nuclear Safety Information Center (NSIC)

Technical Information Center (TIC)

REG:I Reading Room State of New Jersey C 04 gyp (, $0CRWt*nh oh fr(VtOLU gOjhi tIW ') ')'A')*5~

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Public Service Doctric and Gas Company 80 Park Place Newark,N.J. 07101 Phone 201/622 7000

_ May 28, 1976 Mr. James P. O'Reilly, Director U.S. Nuclear Regulatory Commission Office of Inspection and Enforcement Region 1 631 Park Avenue King of Prussia, Pennsylvania 19406

Dear Mr. O'Reilly:

STEAM GENERATOR HEAD CIADDING INDICATIONS NO. 1 UNIT SALEM NUCLEAR GENERATING STATION DOCKET NO. 50-272

' Supplementary to our verbal report of April 8, 1976 and pre-liminary written report of May 5, 1976 concerning indications in the stainless steel cladding of No. 1 Unit Steam Generator Heads, the follcwing detailed report is submitted in accordance with provisions of 10CFR50.55(c).

INTRO DUCTION Subacquent to our May 5, 1976 report, nondestructive examinations of the stainless steel cladding in the heads of No. 1 Unit Steam Generators (11-14) were conducted using the water washable dye penetrant method. The results of these examinations along with me tallurgical evaluation using replicas , have been reviewed by Westinghouse at Tampa, Florida. These evaluations have not re-vealed the cause of the cladding indications. A, program for ultrasonically monitoring a representative single' area of clad-

-ling indications in 'the cold leg of Ho. 14 Steam Generator is planned, access permitting. If the studies show that these re-presentative cladding indications can be referenced successfully, a surveillance schedule will be incorporated into the nuclear plant inservice inspection program. .

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P. O'Reilly Mr. J. EXAMINATIONS NDE A.

Nondestructive examination of the Unit 1 Steam Generators

( 11- 14 ) u s i n g the wate r washable dye penetrant method revealed extensive transverse and longitudinal cladding indications at bead overlaps and within the veld beads on the No. 14 Steam Generator. These defects were concentrated at one location on the upper bowl of the cold leg side in an area approximately 2' x 4'. The other steam generators No. 11, 12 and 23 and the hot leg side of No. 14 Steam Generator showed minor, randomly scattered indications. In addition, the No. 11 hot le g and No. 14 cold leg have indications at the toe of fillet weld on the cladding joining the partition plate, to the head.

Although there were some clad indications in the nozzle of - -

No. 14 Steam Generator cold leg, and minor indications in other steam generator no r t le s , there were no clad defects .

evident in any inner corner radi1 of the noz z le s .

B. FERRITE AN A LY S I S A ferrite corrosition examination was conducted on the No. 14

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Steam Generator within the indication (2' x 4') zone as well as in areas where dye penetrant found no indications.

Starting from the top of the channel heed bowl, at the junction of the tube sheet cladding to bowl cladding, each w eld bead was measured for ferrite with a Severn Gage. A series of locations across the No. 14 steam generator, app r o x ima t e ly 18" apart, were checked for ferrite level. Results of the an a ly s i s re ve a le d that veld beads measured by the Severn Gage contained 3.55 to 12.56 measured ferrite. There was no s i r,n _ f i c a n t difference in ferrite content between the areas with dye p e ne t ra n.t indications and areas free from indications.

C. RE P LI C A TI O N Four areas with dye penetrant indications were s e le c te d for replication of the surface condition. Replicas of acetate film were taken of the No. 14 Steam Generator cladding of the following surface conditions:

(1) as deposited clad (2) polished clad --

(3) polished and etched clad.

These replicas were examined at the Westinghouse Tampa Metallography L1boratory at 50 to 500 magnifications. The .

results show the indications to be fine, intergranular crackc. ~

The mechanism explaining the formation and the d.ynamics of its propagation has not been formulated. _

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Mr. J. 'P. O 'Reilly 5/28/76 EXPLORATORY GRIUDING s

Four areas where cracks were present in No. 14 cold leg were ground to a depth approximately one-half of the nominal cladding thickness to avoid exposing base metal. The cladding is nominally 0.250", therefore the maximum depth excavated was 0.125". All explored cracks propaged into the cladding normal to the clad surface. The four ground areas were re-examined with dye penetrant.

Three areas following grinding showed the cracks still present,

while the fourth area 2" x 3", where grinding for chemistry was conducted, was free of any dye penetrant indications. ..

CHEMICAL AUAlYSIS -

An area approximately 2" x 3" in the cracking none of No. 14 Steam Generator was selected for chemical analysis. Results of spectro 6raphic and chemical analysis of the chips revealed the clad metal to be w. thin the specification for all metallic elements.

The carbon content was above the specification, however, this could be traced to the particles of grinding cutter abraded into

the sample.

[ CONC LUSIO N S The work jointly corducted by Westinghouse and PSE&G has succeeded in defining the scope of the problem at Salem Kuclear Gererating

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Station (No. 1 Unit). The transverse and longitudinal cracking is concentrated in one area (2' x 4') of the upper bowl of the cold leg of Uo. 14 Steam Generator. There are minbr indicativ.Es in the

No. 11, 12 and 13 Steam Generators as well as the hot les cide of

[ No. 14 The investigation to date has not determined the cause of E

the cracking but it has determined that the condition at Sale =

F closely parallels the defects revealed' in channel head cladding a t Consolidated Edison's Indian Point No. 3 Nuclear Generating Station.

1 The controlled investigation conducted at Salem by Westinghouse and PSE&G has shown that in one isolated area 2" x in the cladding were removed prior to exposure of base metal.

3", the defects i]li ~ ~ - ~

Exposure of base metal was averted at Salem to prevent extensive weld repairs which have been previously experienced by others.

w A review of the safety implications conclude that the cracks in the cladding at Salem Nuclear Generating Station, No. 1 Unit are s acceptable as the integrity of the system is not compromised.

The Boiler and Pressure Code allows cladding indications and the subject of surface indications in cladding is defined as part of E '

Section XI Code Case No. 1738 (attached).

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O Mr. J. P. O'Reilly -h- 5/28/76 _

CONC LUSION S (Continued) .

The intent of the code case is to verify that the cracks are indeed confined to the cladding and do not progress into the base metal.

This condition can be reasonably substantiated by ultrasonic

• cxamination of representative cladding defects. .

This inspection conducted on the channel head will attempt to:

(a) identify the cladding indications en the cladding surface from the O.D. of the head. . - ,

(b) mecsure the thickness of the cladding in the vicinity of the indication from the I.D. of the head (c) verify whether the cladding defect has propagated into the base metal.

If succcesful, the ultrasonic examination will then serve as the baseline pre se rvice inspection of the steam generator cladding.

The cladding indications will then be monitored as part of the inservice inspection program for the life-time of the nuclear .

plant. This examination vill..be complete by June 30, 1976. .

The results of these examinations vill be available at the site.

If you require additional information our engineers will be available to discuss the details with you.

Very truly yours,

_ 6 19. 5 : k E.N. S chwalj'e Manager of 0.uality Assurance Engineering and Construction Department CC: Dr. Ernst Volgenau Washington, D.C. 20555 6

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.. *t CASI' - AS11Cllull.Elt ANI)1*Ill3SI:ltU VD8El. Col Approved lay Council, Decernber 22, I975 Case 1738 Examination-Acceptance Standards for Surface Indica.

tions in Clodding ,

Section XI fnguiry: Is it perini=>ilde to accept surface indicatiuns in the pstches of cl.id entf.:cet emnine d in accordance with Category ll l.1 and 1: 12. Tahic IWl: 2(;00. itction XI, provided that the depths of the flaws.tre within the

- cladding niatcrial!

, Reply: It is the opinion of the Conunittre that surface indications in the pateir of clail >ntfaces cssinined in accordsuce with Categ ory 1:11 and 1312. Table IWil.

2000, Section NI, insy 1,e :.erinitted and the secri.tsnee standards of IWittl7.1 n:ay be wahed providctl the l depths of the fisws are within the claddin::inateris!.The provisions of this Case snay not he app!ied ic.r the exand.

nation of clad surfaces on the inner corner radii of nozzles.

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