Text

Responds to Generic Ltr 88-01 Re NRC Position on IGSCC in BWR Austenitic Stainless Steel Piping.Includes Insp Plans & Mitigation Plans.Separate Submittals Will Address Resistance Heat Stress Improvement & Change to Tech Specs
	ML20151X102
Person / Time
Site:	FitzPatrick
Issue date:	08/16/1988
From:	Brons J; POWER AUTHORITY OF THE STATE OF NEW YORK (NEW YORK
To:	; NRC OFFICE OF ADMINISTRATION & RESOURCES MANAGEMENT (ARM)
References
	RTR-NUREG-0313, RTR-NUREG-313 GL-88-01, GL-88-1, JPN-88-041, JPN-88-41, NUDOCS 8808250222
	Download: ML20151X102 (150)
	v • d • e

123 Ma:n Street Wh.ie P:a:ns, New Yor k 'C(41 914 fil C240 4 NewYorkPower ses" c 8<e"-

E xecutivo Vao Pr esident 4# Authority w ~rme -

August 16, 1988

', JPN-88-041 U. S. Nuclear Regulatory Commission

. Mail Station F1-137 Washington, D.C. 20555 Attn: Document Control Desk

Subject:

James A. FitzPatrick Nuclear Power Plant Docket No. 50-333 Response to Generic Letter 88-01 NRC Position on IGSCC in BWR Austenitic Stainless Steel Piping

Reference:

1. NRC Generic Letter 88-01, dated January 25, 1988, which transmitted NUREG-0313 Rev. 2 "Technical Report on Material Selection and Processing Guidelines for BWR Coolant Pressure Boundary Piping".

Dear Sir:

Reference 1 requested that the Authority provide our current plans relating to piping replacement, inspection, repair and leakage detection. The Authority intends to follow the staff positions included in Reference 1 with three inspection exceptions as described in Attachment I. In addition, the Authoriuy takes credit for inspections performed in 1984/1985, although the qualifications for inspectors at that time pre-dated the upgraded program initiated in September 1985. Justification for this approach is discussed in 1.ttachment I.

Attachment I includes the Authority's plans for intergranular stress corrosion cracking (IGSCC) inspections during the September 1988 outage. In accordance with 10 CPR 50.55a(o), the Authority will notify the NRC of any flaws identified that do not meet IWB-3500 criteria of Section XI of the ASMS code. The NRC will be notified of any change found in the condition of welds previously identified to be cracked.

This submittal also includes future plans for IGSCC mitigation. A separate submittal will be provided which will discuss resistance heating stress improvement. Another separate submittal will address a change to the Technical Specifications to include a statement on inservice inspection of piping covered by Reference 1.

q l I khk khjCK 22 8e0816 05o003 3 P

PD -

~

/ .

FitzPatrick Technical Specifications related to leakage detection are in c.nformance with the staff position included in Reference 1.

t Should you or your staff have any questions regarding this matter, please contact Mr. J. A. Gray, Jr. of my staff.

very truly yours,

,e vu.

John C. Brons Executive Vice President Nuclear Generation

)

STATE OF NEW YORK COUNTY OF WESTCHESTER Subscribed and sworn to before me this /[8 day ofdb n- 1988 Notary Public IdetA HOLDet tenst g ene meest t Me"ss= as m.uma cc: U. S. Nuclear Regulatory Commission Region I I

475 Allendale Road King of Prussia, PA 19406 Office of the Resident Inspector U. S. Nuclear Regulatory Commission P. O. Box 136 Lycoming, New York 13093 Mr. Harvey Abelson Project Directorate I-l Division of Reactor Projects - I/II l U.S. Nuclear Regulatory Commission l Mail Stop B14 2 Washington, DC 20555 Mr. R. McBrearty U. S. Nuclear Regulatory Commission Region I 475 Allendale Road King of Prussia, PA 19406

l .

l !

l 6 ATTACHMENT 1 l

INTRODUCTION The Authority conducts an aggressive Intergranular Stress l Corrosion Cracking (IGSCC) detection / mitigation program l including comprehensive inspections of susceptible welds. The program also includes:

[ e induction heat stress improvement (IHSI) of most of the recirculation system, e planned selective replacement or removal of piping, and a hydrogen water chemistry: water chemistry upgrade, hydrogen addition system, and crack arrest verification system.

Since the last submittal, the Authority has comprehensively reviewed all FitzPatrick IGSCC susceptible welds. Previously, the welds had been categorized according to NUREG-0313 Rev. 2, (Draft), and incorporated in a computer database. With the issuance of Generic Letter 88-01 and NUREG-0313 Rev. 2, the computer database has been updated and is included in Attachment 2A. Corrections to the computer database as provided in previous NRC submittals are included in Attachment 2B.

A report is also provided in Attachment 3 which details the IGSCC status of the FitzPatrick plant. Structural Integrity Associates completed this report as an overall third party review of the FitzPatrick IGSCC program. This report also includes a summary of IGSCC indications and supporting fracture mechanics evaluations for each weld. Induction Heating Stress Imprevement or veld overlay has been performed on all welds that contain IGSCC. This report also describes the Core Spray weld overlay designs. Weld overlay designs for the Reactor Recirculation System were provided in a previous submittal, JPN-87-008, dated March 10, 1987. ,

l As part of the high priority the Authority places on IGSCC issues, a Level III EBASCO Services, Inc. inspector reviews all NRC submittals with respect to scope and content. Structural Integrity Associates has also provided third party review services of the Authority's IGSCC program and NRC submittals.

l l

l

I Some of the more significant topics covered in this submittal are:

e The Authority's IHSI mitigation program. !

e Water Chemistry Program Upgrade.

e Fracture mechanics evaluation on IGSCC-cracked weldsents and weld overlay design bases.

e Limited pipe replacement.

e IGSCC inspection program and ISI calibration block program.

e NUREG-0313 conformance and exceptions taken to the NUREG.

i 1

MITIGATION ACTIVITIES

1. IHSI As part of the IGSCC program, IHSI was applied to welds in the Reactor Recirculation and Residual Heat Removal (RHR) Systems during two maintenance outages in 1984. In most cases, an ultrasonic examination was performed both before and after the IHSI application. In all cases a post-IHSI examination was performed except as noted in Exception 3. Qualified personnel from EBASCO Services Incorporated, the New York Power Authority, and Universal Testing Laboratories /Kraf twerk Union (KWU) performed the required ultrasonic examinations. The total radiation exposure to personnel during these two outages was 502 person-rem. Of this total, inspection personnel received 62 person-rem. The Authority plans to take credit for these inspections as part of the IGSCC program.

The inspectors were qualified in accordance with NRC I&E Bulletin 83-02. The inspections performed in 1984, as part of the Authority's stress improvement program are considered the initial examinations for the Authority's NUREG-0313 inspection program.

Resistant Heating Stress Improvement (RHSI) was performed on two welds, 28-50 and 28-108, during the 1987 refueling outage. The supporting documentation regarding the residual stress state will be forwarded to the NRC under separate cover. Following NRC approval of the RHSI process, the two welds will be considered to be in the same NUREG category as welds that have been IHSI treated.

2. Pine Reelacement Two major piping modifications were completed during the 1987 refueling outage. The Reactor Recirculation System bypass lines were removed and capped. This eliminated 20 IGSCC susceptible welds (NUREG-0313 Category D) . The cap material is 304L and the existing 304 weld-o-let had a corrosion resistant cladding (308L l weld metal with FN greater than 8) installed for IGSCC resistance. The four cap welds are considered to be Category A.

Radiation exposure to field supervisors and craft labor was 48 person-rem to complete this work.

The RER suction piping and Reactor Water Clean-up suction piping were also replaced. The stainless steel pipe material was l replaced with high toughness carbon steel material. The type 304 pipe end was clad with 308L weld metal (FN greater than 8) prior i to welding to the carbon steel pipe. This eliminated seven ;

Category D welds. The radiation exposure to field supervisors and craft labor was approximately 88 person-rem to complete this work. Installation costs of the above modifications were approximately $1.5 million.

l

\

The "A" Core Spray piping was replaced with 316L material in '

1981. The weld metal used was 316L for pipe welds, while the one dissimilar metal weld used 309L as the butter material. i The control rod drive return line was cut and capped in 1983.

Acceptable results were obtained from liquid penetrant tests, I

which were performed on the Inconel 182 weld butter prior to I welding. This weld used Inconel 82 as the weld filler material.

j It is considered a Category G weld for program administrative purposes due to the Inconel 182 weld butter. The weld will be inspected during the 1988 refueling outage. ,

The "B" Core Spray piping is scheduled to be replaced during a maintenance outage scheduled for September, 1989. The replacement safe end and pipe material which will be used is 347 l modified stainless steel, a resistant material. The use of bent !

piping spools will reduce the number of welds in this system from nine (9) to three (3) when the pipe is replaced. This will result in a reduction in future radiation exposure to both craft and inspection personnel. ,

In addition, the Authority is investigating the possibility of injecting Recirculation System water into the Jet Pump Instrument (JPI) Assembly drain line. This would protect the JPI assembly (10 welds total) from IGSCC when hydrogen water chemistry is (

implemented. Conceptual engineering has been completed, and i detailed design engineering is presently on schedule for i implementation during the 1988 refueling outage. This method is l also under consideration to protect the six (6) RHR tri-metallic welds which contain Inconel 182 from IGSCC.

l j

3. Weld overlava -

1 Installation History Weld overlays were first installed at the FitzPatrick plant upon detection of IGSCC during the Fall 1984 INSI outage. During this outage, five standard weld overlays were installed on the Reactor Recirculation System.

During the 1985 refueling outage, one additional standard veld overle.y was installed on the Reactor Recirculation System due to IGSCL.

During the 1987 refueling outage three weld overlays (2-standard and 1-designed) were installed on the "B" Core Spray system due to IGSCC.

Detailed information such as design basis thickness, as-built data upon completion of surface finishing, pc-CRACK computer runs for overlay designs, and stress inputs into computer runs on all weld overlays installed at the FitzPatrick plant is provided in Attachment 3.

Inspection History Weld overlays installed before the 1987 refueling out&ge wara surface finished (field criteria of 250 RMS-Flatness of 1/32" per inch) for inspectability in 1987. All overlays have been evaluated to the design requirements of NUREG-0313 Rev. 2, Draft, "Standard Wald Overlays". Inspections were performed by personnel qualified in this method by the Electric Power Research Institute Boiling Water Reactor Owners Group (EPRI-BWROG) training program.

Weld overlays (3 total) installed during the 1987 refueling outage were designed in accordance with NUREG-0313 Rev. 2 7 Draft. A comparison of the draft NUREG-0313, Generic Letter 88-01, and NUREG-0313 Rov. 2, final, shows that the design basis for weld overlays was not changed, and thun, all weld overlays installed at the FitzPatrick are in full compliance with the recently issued NRC requirements. Two weld overlays are the "standard weld overlay" as defined in NUREG-0313. One weld overlay is the "designed type" as defined in NUREG-0313. This overlay is installed on a weld that has four axial IGSCC flaws.

All overlay thickness measurements do not take credit for the first dye penetrant tested clear layer.

J l

.- __ .--- . . - - _ - =- - . - . _ . _ _ - _ _ --

Because of the high estimated radiation exposure (8 person-rem),

1 surface finishing and inspection of the overlays is not being performed at this time.

Desian Basis All wild overlays installed at the FitzPatrick plant were

installed and designed in accordance with Generic Letter 34-11, NUREG-0313 Rev. 2, Draft, and the criteria of ASME Section XI, Article IWB-3641, 1986 Edition. Eight veld overlays installed were designed in accordance with the requirements of a NUREG-0313

, "standard overlay" and thus were designed to repair a circumferentially oriented 360 degree through wall crack. One overlay was the "designed type", since the weld contained only axial flaws. Low carbon weld metal, type 308L with high ferrite :

(>8FN), was used for the application of the weld overlay.

Because of possible dilution effects with the base material (304) the weld overlay design basis did not take credit for the first layer installed. The overlays were installed by the GTAW procena.

Recent NRC directed research, NUREG/CR-4667 Vol. III and IV, has proved the effectiveness of weld overlays in arresting IGSCC crack growth and the immunity of 308L weld metal with high ferrite to crack propagation.

L The Authority uses the Structural Integrity computer program pc-CRACK to perform weld overlay designs. Structural Integrity is under contract to the Authority to provide IGSCC consulting services as required.

4. Fracture Mechanics Evaluations Structural Integrity Associates performed fracture mechanics flaw

] evaluations of IGSCC indications using the pc-CRACK computer j program. The Authority has purchased the program to permit third party audits by Authority engineering personnel. The evaluations were performed in accordance with NUREG-0313 Rev. 2, Draft, with weld residual stress distributions used in the computer runs.

s Attachment 3 includes a detailed discussion of the fracture

, mechanics methodology and pc-CRACK analyses. Attachment 3 also details the Recirculation System piping stress used in the pc-CRACK evaluations. A detailed evaluation of each weld location that may contain a flaw and a discussion of previous inspection history has been provided in JPN-87-018, dated April 9, 1987.

l 4

l I

11 future flaw evaluations will use the cre,ck growth law as detailed in NUREG-0313 Rev. 2 on page A.2. The analyses summarized in Attachment 3 incorporate this crack growth law.

NOTE The pc-CRACK program that the Authority will use for all crack growth evaluations uses a third-degree polynomial for curve fitting of the weld residual stress curve, and for subsequent stress intensity factor calculations of the welding residual stress. The final version of the NUREG

' l states that a fourth degree polynomial should be used for J residual stress curve fit and stress intensity factor l calculations of the weld residual stress. The pc-CRACK 4

program will yield essentially identical stress intensity 4

factor results as the fourth degree polynomial recommended in the NUREG.

5. Personnel cualifications During the 1987 refueling outage, all personnel performing IGSCC examinations were training program. qualified IGSCCin detectionaccordance with the EPRI-BWROG was performed by EBASCO using manual examinations, and Independent Testir.g Labs (ITL) using l automated P-scan during the 1987 refueling outage.

Two independent examiners performed sizing of IGSCC indications during the 1987 refueling outage. Both examiners were qualified in sizing in the EPRI-BWROG training program. The examiners were also from two independent firms (EBASCO and General Electric).

Detection and sizing of IGSCC indications prior to 1987 (1985 refueling outage and 1984 IHSI outages) were performed in part or in combination with one of the following, EBASCO, JAF Level III inspector and XWU. All inspectors were qualified in accordance with the EPRI-BWROG program in effect at the time inspections were performed, l i

l 1

1 I

(

W 4

1 4

,-._.-_._.-,_.,..._--._,._.,-...--.,..,-Y.

l

6. Insoection Plans for the 1988 Refuelina Outaae r

The following table addresses the total number of welds within the scope l -

of NUREG-0313 Revision 2 per Generic Letter 88-01. This refueling outage is considered to be the beginning of the NUREG inspection schedule. All inspection personnel for nanual and automated IGSCC examinations will have been qualified via the EPRI-BWROG training program which is conducted ht the EPRI NDE Center.

Inspections performed in 1984, 1985 and 1987 are included and inspection credit is taken within the NUREG inspection totals. Detailed justification is provided at the end of the following table.

WELD

SUMMARY

TOTAL NUREG No.of Welds NUREG Req. No. of welds scheduled Category by Category (f welds req.) for inspection this outage A 26 25% in 10 years 1 (1.3)

C-1 53 100% in the next 27 two refuel outages (26.5)

C-2 11 100% in 10 years O See Note 1 (0)

C-3 2 stress >1.0 Sm 1 See Note 2 (0)

C* 2 0 0 See Note 3 D 18 100% in 2 fuel cycles 1 See Note 4 (0)

E 11 100% in 2 fuel cycles 4 See Note 5 (0)

F 5 All every outage 2 See Note 6 (5)

G 23 All every outage 18 See Note 7 I

(23)

TOTAL 151 54 See Note 8 Expansion due to new incidents of IGSCC shall be in accordance with paragraph 5.3.4 of the NUREG. There are no NUREG category B welds within the weld population.

All welds that contain Inconel 182 (l?-safe end to nozzle welds and 6-tri-metallic RHR valve velds) have been classified as NUREG Catecorv G for orocram administrative ourposes. Crackino incidents have been relatively few in corcarison to 304 stainless steel.

- _ _ . . -. . . . . - = . - -- .. --.- - .-- - - - - - - . - . - = -

, 1984/1985 Insoection Credit I l

As discussed previously IHSI was applied to welds in the Reactor !

. Recirculation System. Qualified personnel from EBASCO services I Incorporcted, the New York Power Authority, and Universal Testing Laboratories /KWU performed the associated ultrasonic examinations.

Total radiation exposure to personnel during these two outages was 502 person-ren including 62 person-rem to inspection personnel.

i l

During the 1985 refueling outage IGSCC inspections were performed in )

accordance with Generic Letter 84-11.

The qualifications for inspectors in the 1984 and 1985 outages I pre-dated the upgraded program initiated in September 1985. All inspectors were qualified in accordance with the EPRI-BWROG program 1 in effect at the time inspections were performed. Personnel qualifications are discussed in Section 5.0 of this attachment. In '

many cases examinations were performed in 1984 and 1985 by both manual and automated inspection techniques. Independent examinations 1 were also performed by the Authoricy's Level I1? examiner. I l

A review of the inspectors certifications for examinations performed in 1984 and 1985 shows the following:

1. Eight (8) inspectors from ETASCO and KWU whc performed i examinations during the 1984 and 1985 outages are qualified per l

the recent EPRI registry dated January 1988. The Authority's Level III inspector has recently qualified in sizing and detection (June 1988) . The Level III inspector also performed inspections in 1984 and 1985.

2. Twelve (12) welds that had been IMSI'd and ultrasonically examined in 1984 were inspected in 1987. Only one weld, 28-56, was found to contain IGSCC. This weld was examined (Post-IHSI) in 1984 and Ir4CC was detected by EBASCO. This weld was evaluated by KWU during a sizing examination and the indication was determined to be attributable to root geometry. This weld was selected for inspection in 1987 based on this data discrepancy.

This weld is discussed in detail in the Authority's letter JPN-87-018 dated April 9, 1987.

3. Two (2) welds that were examined in 1985 were again inspected in 1987 due to the application of RHSI (Post-RHSI examination). No j IGSCC was detected.

1 2

4. Based on the inspections performed in 1987 (48 welds), no new overlays were required on welde that had been IHSI'd in 1984.

One additional fracture mechanics evaluation was required on an i r

IHSI'd weld (28-56) as discussed above. !

1 5. Inspections of Categories C-1 and C-3 planned for this refueling i catage include 28 welds that had been IHSI'd in 1984.

I As a result, a total of 40 welds that had been IHSI'd in 1984 and l j

had received a Post-INSI exam will have been inspected upon completion of the 1988 refueling outage. There will be 27 wilds !

remaining (IHSI with a UT exam performed in 1984) that will be l inspected in 1990.

4 L !

i l

7. Water Chemistry Unarade The FitzPatrick Water Chemistry Program includes implementation of the EPRI BNROG Water Chemistry guidelines, a hydrogen injection system, and a crack arrest verification system.

Installation and pre-operational testing have been completed and the Authority plans to begin operation following the 1988 refueling outage. The Water Chemistry Guidelines have been implemented as guidelines and are not treated as mandatory requirements.

l NOTES

\

- - NOTE 1 All Category C-2 welds were inspected during the 1987 !

refueling outage. These velds have had a post-INSI examination performed in 1984. {

, i

- - NOTE 2 Two welds, 12-58 and 12-67, have service stress (deadweight, pressure, and thermal) greater than 1.0 Sm. This is in accordance with NUREG-0313, Rev.2, '

Jaragraph 4.5, "SI crack Mitigation criteria." Wald 12-58 was inspected in 1985. Wald 12-67 was inspected l in 1984 by a Pre and Post INSI ultrasonic examination. '

Since no IGSCC indications have been noted, the SI treatment is not considered a repair mitigation method as discussed in Section 3.2 of the NUREG.

The Authority interprets section 4.5 of the NUREG to apply to weldments with cracking in which the service stress is greater than 1.0 Sm.

An additional weld, 12-61, has a service stress > 1.0 Sm and is noted in Note 5 below. It will be inspected d

this outage.

, *** NOTE 3 These welds have been RHSI treated, and a post-RHSI inspection was performed in 1987. These welds were also inspected in 1985. The RHSI analysis and j

justification is provided under separate cover.

I 1

- - NOTE 4 All Category D welds were inspected in 1987. Tbsse welds consist of the welds on the Core Spray "B" loop !

and the safe and to nozzle welds which contain Inconel 182. The safe end to nozzle calibration blocks represent the actual mockup or "as-built" condition of I the welds. These calibration blocks were used for ultrasonic examination procedure calibration prior to inspection in the field.

a One Core Spray "B" loop weld will be inspected. !

l i

)

i

- - NOTE 5 Six welds within this Category have full structural weld overlays which were surface finished and' inspected

. by EPRI qualified personnel during the 1987 refueling

! outage. These welda are not required to be inspected 2

until 1990 in accordance with Section 5.3.2.5 of the NUREG.

d 4

Five welds contain IGSCC and have had IHSY performed in l 1984. All welds vers inspected in 1987 and thus are

D21 required to be inspected per NUREG 5.3.1.5 and i

5.3.2.5. One of the five welds (12-61) has a service stress greater than 1.0 Sa (2.5 kai greater than 1.0 Sm). This weld was inspected by two independent examiners in 1985, KWU and Ebasco. This weld was also inspected in 1987 by two independent examiners, Ebasco and GE, with no change in data noted. Four welds, i

including 12-61, are planned for inspection during tho

1988 refueling outage.

- - NOTE 6 Two welds contain IGSCC and had IHSI performed in 1984 but do not meet the requirements of NUREG section 4.5 1

with. etch to crack length (length is greater than

' 10%). >: se two welds will be inspected during the 1988 1-rueling outage.

One weld, on the "B" core spray line, had a designed

overlay installed as a result of four axial cracks detected during 1987. Two welds are full structural i

overlays installed on the same "B" loop in 1987.

Surface finishing and inspection was not performed at

this time. This pipe will be replaced during the 1989 September maintenance outage.

See Excention 1 k *** NOTE 7 Three of these welds (out of a population of six) are RHR welds that contain Inconel 182. See Excention 2.

Two of these welds (out of a population of four) are Recirculation system welds in which an effective IGSCC

examination was not performed. see Eveention 3.

- - NOTE 8 This total does not include two creviced safe ends on

! the core spray "A" and "B" loops, one of which will be j inspected this outage. The thermal sleeve is connected a

to the safe end by a threaded connection and will be inspected for IGSCC due to crevice corrosion

! conditions. A calibration block that is a duplicate of l the as-built conditions has been fabricated ;

for use.

1 Three carbon steel welds have not been included in the i

weld population total but are noted on the computer l database. These welds were originally stainless steel l and were replaced in 1987.

I i

i i

,_,,,,-.,----.,,.,,m,.m,_,_,_w.,w.m,,,----w_m_...m_.,,,e mm....m ,. ..m-m __mmem.,-m--~,- em.--m

EXCEPTIONS TO NUREG-0313 l *** EXCEPTION 1 l

Two standard and one designed weld overlays were installed on the !

Core spray "B" loop during the 1987 refueling outage. The weld -

overlays will not be surface finirhed and. inspected during this ;

i outage, because the piping will be replaced during the currently ,

scheduled september 1989 maintenance outage. These welds are l considered NUREG Category F, because a qualified inspection was l l not performed. j i During the September 1989 maintenance outage the Core Spray "B" !

1 loop piping will be replaced. When the eine reelaceinent effort i is completed the nine NUREG Catecorv D.E or F wolds in the line <

will be reolaced by only three Cateaory A welds due to a nine )

redesian effort and the use of bent eine in lieu of fittinas.

This is a future ALARA savings based on the reduced number of l s

welds required for inspection. '

l The weld overlays were installed in accordance with Generic Letter 84-11 and NUREG-0313, Rev. 2, Draft requirements. All !

] overlay designs did not take credit for the first dye penetrant I tested clear layer. In addition, no "blowthroughs" were detected '

during installation of the weld overlays. Design information and ,

] as-built data is provided in Attachment 3.

i The Authority requests relief from the inspection requirements of

NUREG paragraphs 5.3.1.5 & 6 and 5.3.2.5 & 6 for the three weld overlays. The Authority requests that the NRC allow operation for more than one fuel cycle (from the November 7, 1988 outage i j

completion, to the currently scheduled r.41ntenance outage for I i september 1989) with the weld overlays presently installed. !

) surface finishing and inspection is not in keeping with "as low as reasonably achievable" person-rem), since the pipe (ALARA) principles (estimated 8will be replaced with

*** EXCEPTION 2 i Six NUREG Category G welds in the RNR system contain Inconal 182 weld metal which was used during construction as the weld {

j butter. The total of six welds is composed of two welds of each '

l of three different configurations. Each RHR loop contains three i

welds-one of each configuration. The Authority requests that relief be granted and that only three welds on one loop be inspected during the 1988 refueling outage. If IGSCC is detected i

in one of the welds, the other three welds will be inspecteAt :

The ALARA savings is estimated at 12.5 person-rea due to the high i

area radiation levels, craft labor support for scaffolding,

) insulation removal and the surface finishing required prior to i the weld inspection. The inspection technique currer.tly under j development requiras inspection from the weld surfa:e and thus i

1 the complete weld must be surface finished prior to inspection. l

! Currently unique calibration blocks are being fabricated for each l

weld configuration which represent the actual as-built conditions

!' ~12-

1

~ b2ccd Cn a rCvicw of tho origin 3l c3nDtructicn Cnd wolding j records. The Authority's ISI vendor, EBASCO Marvices, will ;

develop ultrasonic transducers and procedures upon fabrication of '

the calibration blocks.

It is noteworthy, that during the 1987 refueling outage the safe end to nozzle calibration blocks were used which represented actual as-built conditions. These calibration blocks were used for ultrasonic examination procedure calibration prior to use in the field. No IGSCC indications were detected in the 8 welds inspected.

Upon completion of the 1988 refueling outage, 20 welds, out of a total population of 23 that contain Inconel 182 weld butter, will have been inspected. This weld population includes the 17 safe end to nozzle welds and the 6 RHR welds that contain Inconel 182 butter. Based on the inspection results of the Inconal weld butter in 20 of the welds (i.e., that no IGSCC is detected), the Authority is confident that no IGSCC would be anticipated in the l three RHR welds that were not inspected. The three uninspected l welds will be inspected during the next scheduled refueling outage in 1990.

If IGSCC is detected in one of the RHR welds, the other three welds will be inspected. l

- - EXCEPTION 3 i

There are four Recirculation System welds (Category G- two on each loop) in which an effective IGSCC examination was not i performed upon completion of the IHSI process performed in 1984 !

due to complex weld geometries. A sero degree inspection was performed at that time. Subsequent reviews of the data revealed that the zero degree inspection had been incorrectly recorded as !

an IGSCC-effective inspection. This was reported to the NRC in JPN-87-035 dated July 2, 1987. ]

1 Presently unique calibration blocks are being designed, based on a review of construction records and thickness contours, by the Authority's ISI vendor with final approval by the Authority's JAF 4

site Level III. IGSCC procedures will be developed upon procurement of the fabrication blocks. The inspection procedures

, may require examination from the weld crown and thus surface finishing of the weld crowns will be required.

The Authority requests relief from the requirements of NUREG !

paragraph 5.3.2.7. The Authority proposes to inspect two of the four welds (one of each weld geometry) due to ALARA 2 considerations, i.e., estimated 3 person-rem to inspect the two i additional welds. The high anticipated exposure is due to the surface finishing requirements in addition to scaffolding and insulation removal / replacement requirements. The twr remaining welds will be inspected during the next scheduled ret ling l

, outage. In ariition, the Authority's past experience >ith the post UT inspection of IHSI-treated welds has been excellent with no significant cracking noted.

l If IGSCC is detected in one of these welds, the additional two l welds will be inspected during the refueling outage. l

! l 4

._.-.---..---_--,-------._,-l

1 9

s 9

ATTACHMENT 2A COMPUTER DATABASE i

1 1

l 1

1 i

i i

. . - u . . . . - - - - - - .

i R 8 8

=

a a a a a e a e u a ! I 111IIIIIIi11 X

. . . 7 . 7 . . . 7 I#

X X X X X X X X X A X.

s a a a a a a a a s a a E E E E E E E E E E E E H H H a

HB '

R g_ei . . . . _ _ _ _

EE8!

R[g . - --

et g a l_ :

e : .

eng - i g2, - - - ,

y ggl -.......... 3 3 :

Ei rrr r rrr r r rr rr 1 1 Y1' % 8 % 8 % B M % % 8 % 8 % % % ,

gt u u u u u a u u u a u a u a u l

^w a,.,

9

)

g * * .

}

i 1

1 1

I-I v

i ,

g" g a g g g g g g g a g g g l c.

D.

s

~ ~ ~ _ ~

lR0 g=. ~ ~ M B Ril

~ - - -

as$_'i . _ _ _ ~

n- " ~ ~ .

g,9: - - -

gag l

ggl 2 3 s s s s s s z s s s j a

EB 2 x ! r 2 2 I r 1 2 f r 2 1 r i Il % I! h h h E E % % % % % % % 3!

gt a a u a a a a a a a a u a a =

4 m k + A -~~ _ . .

. .. . -. w . .i .. . . w. . .

}

O l

l l 1 - -

I I i i e a !

g i ! !,

, e , I a g a a a a a a a a a a a a l l

l 5

81 k.

. Ini- -

i ggl - . .

ai=r a

9 m tji : ,,

E*W. p ggl s s s . s s s . : s s . z

! e EB f r 2 x 2 E E E % x r r x !

!!! E E E E 9 9 8 9 9 9 9 9 9 gs u a u u . u u . . . . . . . .

A -

N N g g g g g e

l d

I. I i lill !

iiiii

,iiniii i n Ill,i ati I s

ls il d

lui - - -

gg -

l gig;-

3l. - - - - - - - -

1 ,

ggl s a s : s . 3 s - 3 a . . =

a ,

I b 2 1 2 2 I 2 2 2 Y I ltl 9 9 9 9 9 9 9 9 9 9 n1 . . . . . . . . . . . u u a u

+ L - . . . . . . . .

a hh E I-I lll 1 I 11 5 5 g

e g i a eis a a

. . a a a a a a E

NE

" s a a kg E t Eu

~

lg . _

!al-ist as 1

.3 % 5 3 - Z 3 3 . 3 5

{Hf 4

E$ % % ! r 2 2 r T r 2 2 Y r 2 2

% 9 g1 . . u u u u n n n u u u u u u

s i 1

. l l

l l

1 i

I I

!u I.

h 4 .

H H H H H H H H H H H H H H H A

NE E

a Eg ag

. _ w

~ ~

E gig . .

lit --

4 gst ______ _ _ _ _ _ -

I 2 s s s s s s lEl 2 . s s . s .

El rr 2 2 x rr 2 x eaaa3 x Ili 8 8 8 8 4 E E E E 9 8 9 9 9

gg u u u u u a u u u a u a a .

~~ ^

I l I 1 i i i "

n i ni a g ia a a i n a n n iin E M 2

s t" t -

in! - --

gg l4 - -

gy ;

sq z z . z z z z e z z z z _ . z Mi r : : : I rr 2 r: I r 2 1 -r I!i 9 9 9 9 9 9 9 9 9 9 9 9 9 g!; e m . e e e e e e a e e a m .

. . . . . . . . . . . . l l

1 1

i I R E w :

X m

[

8 I i g l l 1 l lill!!!8 lXl1 ll1 x!Is

!l i i i i i i . . . i e,,,, l x

= e kg !

E E -

g .a -

gRf- - -

na,e g g E89 '

B "9.

9c9 ! " - - ~ ~ .

gagi ~

$@ 5 5 a a a a . . . s . . . . .

ni 2 2 2 x 2 2 x x i 1 rr2 2 Il 9 9 4 9 9 9 fi4 4 6 6 1 g!- = = = = = = . . . . = = = = =

r 4

5 a

g y :

l 1 i g 1 -

a a aaa 1 ii 1

, i i iii ! a aa n l Wl ng i! o d

= = = _

[gj . .

1 18!: I

go,-

m, .

ggl ...............

4 El r z 2 r a r r r 2 r z 2 r 2 x i, il 6 6 6 6 6 4 6 9 9 4 6 4 4 4 4 31 = = = = = = = = = . e a = = =

, 'm w w b *. . . w w = = = w . .

i

, s ! !-

, s. ,

i

'.; j vf8 I,e i i i i i s

3 e

a ea e av e a a l l,' l y e

iaal1111**li 3

I a i >

1 1

a ,a gg c

IIII9 - :

E I

s !

lli E

- - ! ! ! E E ,

l lRh R

sRg si - - - . . .

M g

k 14 - - -

ggl .. ............

rs z armi 1 1 e...... '

! 11 5 8 5 5 5 5 5 5 5 . .: i

at c === c = = c

.a

. . - - L '

- . v i -

U .- . . . , j , ,

k S

e a

2 3 $

% 3 E E k 2

5 Y d [

E, i R a

g a

l N

E E E l

5 8 1

==-

1 E' I !

i! A h !

I 53 p-l h1

- ,a l C -- ;

1 e

m ,

l O M M M l

e.d S $

a .. I l l

' Hp' '

l ATTACHMENT 2B Corrections to previous submittals of the IGSCC Computer Program Log.

Welds 28-02-2-27 (Key 35) and 28-02-2-85 (Key 85) are reducer to ct 3s welds. These welds were incorrectly noted in JPN-87-035 as Category F welds. These welds are now correctly incorporated in Category G. See Excention 3.

Welds 28-02-2-30 (Key 38) and 28-02-2-88 (Key 88) are cross to RHR tee welds. These welds were incorrectly noted in JPN-87-035 as Category F welds. These welds are corrected to Category G.

See Exceotion 3.

Weld 10-14-495 (Key 130) was incorrect).y categorized as Category E. This weld overlay is a designed overlay and has been correctly categorized as F. Welds 10-14-493, 496 (key 128, 131) have also been re-categorized as F although the overlays are of a standard design. The three welds were not surface finished after installation nor was a IGSCC examination performed.

Weld 12-02-2-58 was incorrectly noted as having been inspected in 1987. The correct weld was 12-02-2-59. Weld 12-58 was inspected in 1985.

9 e

4 e

e ATTACHMENT 3 IGSCC MITIGATION AND REPAIR ACTIVITIES

i Report No.: SIR-87-022 Revision 1 -

Project No.: NYPA-17 l May, 1988 l

l l

IGSCC Mitigation and Repair Activities at James A. FitzPatrick Nuclear Power Plant Prepared by:

Structural Integrity Associates Prepared for:

New York Power Authority l

Prepared by: /

hY 6 Date: /} U /lI8 l

L Gustin i Prepared by:

\.) h jag' b-) b M wt4Date: 8-17-88 a u i

/ /

Reviewed and /

Approved by: s /44 A_ _

Date: 5/27/ff P' . C. Ricd6rdella ~ '

STRUCTURAL INTEGRITY A&TX3ATEINC

EXECUTIVE

SUMMARY

i Intergranular stress corrosion cracking (IGSCC) has been observed at thirteen locations i~n the recirculation system at the l

FitzPatrick Plant. Weld overlay repairs were applied to six of these locations in 1984-85. The remaining seven locations contained only very small indications. These were treated with the induction heating stress improvement (IHSI) process, and shown to be acceptable without repair by analysis. An additional three IGSCC-flawed locations in the core spray B loop were repaired with weld overlays in 1987. l This report documents the technical justification for continued long term operation of the FitzPatrick recirculation system l without replacement or further repair of these flawed locations.

The justification for continued operation of the weld i overlay-repaired locations is based upon the following items:

1. The weld metal used for overlays (308L) is highly resistant to IGSCC, so that crack propagation into the overlay is not expected to occur.

2. The residual stress distribution which results from weld overlay application is highly compressive on the inside surface of repaired piping. This will inhibit furthe. crack propagation and initiation of new cracks in the original pipe weld.

3. The overlays were shown to meet NRC guidance (as summarized in NURIG-0313, Revision 2 Draft), issued subsequent to the time of the FitzPatrick repairs. This guidance remains unchanged in the recent, issued version of NUREG-0313, Revision 2.

11 STRUCTURAL INTEGRITY ASSOCIATESINC

1

4. Effective ultrasonic inspection techniques developed recently by EPRI make monitoring flaws beneath an overlay practical.

5. Although not addressed in this report, the New York Power Authority (NYPA) is implementing hydrogen water chemistry.

This will result in recirculation water chemistry which will be very effective in arresting future IGSCC.

The justification for continued operation with the seven IHSI-treated flaws is based on the following arguments:

1. IHSI produces a strongly compressive residual stress field on the inside portion of treated pipes. This results in complete arrest of shallow flaw growth and inhibition of new flaw initiation. l I

2. The flaws treated with IHSI are very short and shallow.

They are acceptable by a large margin with respect to ASME Section XI standards. They also satisfy the NRC position on IHSI of flawed pipe welds contained in NUREG-0313 Revision 2

{

Draft. This guidance also remains unchanged in the recent, !

issued version of the NUREG.

3. Two welds in the 28 inch portion of the recirculation system contain flaws slightly longer than 10% of circumference.

l These flaws were conservatively evaluated without credit for

)

the beneficial effects of IHSI. These locations were shown l to be acceptable without repair for at least the next fuel cycle, currently scheduled to end on August 24, 1988.

4. The implementation of hydrogen water chemistry will make further propagation of the flaws even more unlikely.

A total of 39 welds in the recirculation and related systems at FitzPatrick have been treated with IHSI. In addition, two welds 111 STRUCTURAL INTEGRITY ASSOCIATESINC

were treated using a Resistance Heating Stress Improvement (RHSI)

~

, process developed by NYPA. These processes effectively minimize the potential for further IGSCC initiation and growth.

To further minimize IGSCC susceptibility, NYPA removed piping sections from the Residual Heat Removal (RHR) suction, reactor water clean up (RWCU), and recirculation bypass lines in 1987.

The RHR and RWCU lines were replaced with a high toughness carbon steel material, which is immune to IGSCC. The recirculation bypass lines were removed, and the pipe stubs were capped with 304L material. The 304 side had a corrosion resistant cladding (308L weld metal) applied. Twenty seven IGSCC-susceptible welds were eliminated by these modifications.

Consequently, continued operation of FitzPatrick with its recirculation system in the present configuration is technically justified.

iv STRUCTUIML INTEGRITY ASSOCIATESINC

4 TABLE OF CONTENTS Section Page .

1.0 INTRODUCTION

. . . . . . . . . . . . . . . . . . . . 1-1 1.1 Background . . . . . . . . . . . . . . . . . . . 1-1 1.2 U.S. Regulatory Position on Weld Overlay Life Extension . . . . . . . . . . . . . . . . . 1-2 1.3 Purpose of Report . . . . . . . . . . . . . . . 1-3 2.0 WELD OVERLAY ACTIVITIES AT FITZPATRICK . . . . . . . 2-1 2.1 Weld Overlay Repairs in the Recirculation System . . . . . . . . . . . . . . . . . . . . . 2-1 2.1.1 Evaluation Criteria From NUREG-0313, I Revision 2 (Draft) . . . . . . . . . . . 2-1 l 2.1.2 Criteria for Inspection . . . . . . . . 2-2 :

2.1.3 Evaluation of Recirculation System Weld Repairs . . . . . . . . . . . . . . 2-2 l 2.2 Weld Overlay Repairs in the Core Spray System . 2-3 !

2.3 Evaluation of Flawed Welds for Acceptance Without I Repair . . . . . . . . . . . . . . . . . . . . . 2-5 i 3.0 l DISCUSSION OF MAJOR TECHNICAL ISSUES . . . . . . . . 3-1 1 3.1 Weld Metal IGSCC Resistance . . . . . . . . . . 3-1 3.1.1 Field Experience . . . . . . . . . . . . 3-2 3.1.2 Laboratory Experience . . . . . . . . . 3-4 3.1.3 Modelling Studies . . . . . . . . . . . 3-9 3.1.4 Model Results . . . . . . . . . . . . . 3-11 3.2 Residual Stress Benefits . . . . . . . . . . . . 3-11 3.2.1 Georgia Power Company / Structural Integrity Associates (SI)/ Welding Services Incorpor-ated (WSI) 28 Inch Notched Pipe Test . . 3-12 3.2.2 EPRI/GE Residual Stress Results . . . . 3-14 3.2.3 Nutech/ Georgia Power Company 12 Inch Weld Overlay Hockups . . . . . . . . . . . . 3-14 3.2.4 EPRI/J.A. Jones 24 Inch Weld Overlay Mockup . . . . . . . . . . . . . . . . . 3-15 i 3.2.5 EPRI/BWROG II Pipe Tests . . . . . . . . 3-16 !

3.2.6 Destructive Assay of Hatch Unit 2 Overlay Specimens at Argonne National Laboratory j (ANL) . . . . . . . . . . . . . . . . 3-16 l STRUCTURAL v DfTEGRITY ASSOCIATESINC

TABLE OF CONTENTS (continued)

Section Pace 3.3 Non-Destructive Examination . . . . . . . . . . 3-17 3.3.1 Recent Developments at the EPRI NDE Center Workshop on Weld Overlay Inspections (RP1570-2) . . . . . . . . . . . . . . . 3-18 3.3.2 Argonne National Laboratory (ANL) 11T Inspection Workshops . . . . . . . . . . 3-19 4.0 WELD METAL FRACTURE TOUGHNESS . . . . . . . . . . . . 4-1 4.1 Battelle/NRC Degraded Pipe Tests . . . . . . . . 4-2 !

4.1.1 Test Objectives . . . . . . . . . . . . 4-2 4.2 Application of Test Data to FitzPatrick Weld i Overlays . . . . . . . . . . . . . . . . . . . . 4-3 '

4.3 Summary . . . . . . . . . . . . . . . . . . . . 4-3 5.0 IGSCC MITIGATION ACTIVITIES AT FITZPATRICK . . . . . 5-1 5.1 Induction Heating Stress Impro.ement (THSI). . . 5-1 1 5.2 Resistance Heating Stress Improvement (RHSI) . . 5-2 '

5.3 Piping Modifications . . . . . . . . . . . . . . 5-3 5.4 RHR Dissimilar Metal Welds . . . . . . . . . . . 5-4 5.5 Jet Pump Instrumentation Nozzles . . . . . . . . 5-5 5.6 Hydrogen Water Chemistry . . . . . . . . . . . 5-5 6.0

SUMMARY

AND CONCLUSIONS . . . . . . . . . . . . . . . 6-1

7.0 REFERENCES

. . . . . . . . . . . . . . . . . . . . . 7-1 APPENDIX A: FLAW EVALUATION CALCULATIONS STRU N INTEGRITY ASSOCIATEINC

i LIST OF TABLES l

Table Pace 2-1 Weld Overlay Repair Dimensional Data for Recirculation System Repairs . . . . . . . 2-7 2-2 Summary of Recirculation System Piping Stresses I at Weld Overlay Repair Locations . . . . . . 2-8 2-3(a) Inspection Results in Core Spray Wellds. . . . 2-9 2-3(b) Weld Overlay Repair Dimensional Data !

for Core Spray System Repairs . . . . . . . 2-10 2-4 Summary of Core Spray System Piping !

Stresses at Weld Overlay Repair Locations . . . 2-11 l 2-5 Reinforcement Sizing Calculation for Core Spray Weld 10-493 . . . . . . . . . . . 2-12 2-6 Reinforcement Sizing Calculation for Core Spray Weld 10-496 . . . . . . . . . . . 2-13 2-7 1987 Flaw and Stress Data for Seven Recirculation System Welds . . . . . . . . . . . . 2-14 2-8 FitzPatrick Flaw Evaluation Results . . . . . 2-15 3-1 Four-Inch Pipe Weld Overlay Residual Stress Mockup Parameters . . . . . . . . . . . 3-21 4-1 Summary of Differences between Battelle/NRC Weld Overlay Test Pipes and FitzPatrick Weld Overlays. 4-5 l

l l

4 STRUCTURAL vil m ASSOCIATESINC l

LIST OF FIGURES

. Flaure Pace 2-1 Weld Overlay Repair Design Sketch for Core Spray Weld 10-493 . . . . . . . . . . . . . . .2-15 l

1 2-2 Weld Overlay Repair Design Sketch for Core Spray ;

Weld 10-496 . . . . . . . . . . . . . . .2-16 3-1 Cracking in Weld Metal of NMP-1 Recirculation Line. .3-22 3-2 Weld Metal Crack!.ag in NMP-1. . . . . . . . . .3-23 3-3 Subsurface Crack Present in Weld Metal in Quad Cities Core Spray Line. . . . . . . . . . . . . .3-24 3-4 Cracking Morphology of Bolt-Loai.7d WOL Specimen EA1 of 316L Stainless Steel. . . . . . . . . . .3-25 i 1

3-5 Cracking Morphology of Bolt- aded WOL Specimen EB1 of Type 316NG Stainless Ste . . . . . . . . .3-26 3-6 Cracking Morphology of Beit-Loaded WOL Specimen EB2 of Type 316NG Stainless St eel. . . . . . . . .3-26 3-7 Cracking Morphology of Bolt Loaded WOL Specimen EJ1 of Type 30A Stainless Steel. . . . . . . . . .3-27 1 3-8 Weld Overlay Arrest of IGSCC Specimen RSP-14 (Ref. 19).3-28 3-9 Influence of N L n the Intergranular Corrosion Behavior of Aged Samples of Wrought and Weld-Deposited Type 308 Stainless Steel. Open Symbols Indicate IGSCC per ASTM A262 Practice E Testing; Closed Symbols Indicate No IGSCC (Ref. 3-7). . . . . . . . . .3-29 3-10 Number of Intercepts of a Random Test Line with Austenite-Ferrite Boundaries per Unit Length of Test Line, N g, Versus Volume % Ferrite for Type 308 Compositions. . . . . . . . . . . . . . .3-30 3-11 MgCl 2 Test Set-Up Using 28 inch Pipe as Vessel. . . .3-31 3-12 Circumferential and Axial Notch Sizes and Locations (Bottom Half is Mirror Image of Top Half of Drawing) -

Showing Stainless Steel B&ffle to Permit Separate Testing with MgCl 2 f Top and Bottom Halves of Pipe (Seal Against MgCl 2 Fumes). . . . . . . . . .3-32 STRUCTURAI.

vill N ASSOCIATESINC

l LIST OF FIGURES (Concluded) ;

1 Flaure Pace i

3-13 Metallographic Sections (100X) of Moderate Depth, l Circumferential Notch Tips from GPC/0I/WSI 28 Inch '

Notched Pipe Test (Ref. 22]. . .3-33

)

3-14 Through-Wall Residual Stresses (Ref. 23). . . . . .3-34 !

3-15 Through-Wall Residual Stresses (Ref. 23]. . . . . .3-35 3-16 ID Stress for 24 Inch Overlay (Ref. 23). . . . . .3-36 i 1

3-17 Calculated Through-Wall Stresses after the First and Second Weld overlay Layers for a 24 Inch Pipe with 1.48 Inch Wall. Overlay contains five weld layers for i a total thickness of 0.35 inch) (Ref. 23]. . . . .3-37 )

3-18 Calculated Through-Wall Stresses after the Fifth and Final Weld Overlay Layer for a 24 Inch Pipe dith 1.48 Inch wall. (Overlay contains five weld layers for a total thickness of 0.35 inch) (Ref. 23) . . .3-38 4-1 Illustration of Cracked Pipe and Wald Overlay Configuration Used in Battelle/USHRC Experiments (Ref. 26). . . . . . . . . . . . . . . .4-6 4-2 Schematic Illustration of Test Setup Used in Battelle/

USNRC Weld Overlay Experiments. . . . . . . . .4-7 4-3 Comparison of Recent Battelle/USNRC Degraded Piping l Program Weld Overlay Tests with Overlay Design Basis I Calculations. .4-8

)

l 4-4 Comparison of FitzPatrick Design and As-Built Weld !

Overlay Data to ASME Design Limits and Recent Pipe I Failure Data. . . . . . . . . . . . . . .4-9 l

l 1

ix ASSOCIATESINC I

1 i

.- l 1

1.0 INTRODUCTION

1.1 Background

Intergranular stress corrosion cracking (IGSCC) has been detected in locations in the stainless steel portions of the recirculation system at J. A. FitzPatrick Nuclear Power Plant since 1984. The initial observations led to application of five weld overlay repairs on welds in the 12 inch recirculation risers. In the spring of 1985, a weld overlay repair was applied to the 22 inch recirculation ring header end cap. All of the repairs to welds in the recirculation system were originally designed to the requirements of NRC Generic Letter 64-11 (1). These repairs were re-evaluated in 1986 and found to conform to the requirements of '

NUREG-0323 Revision 2 (2). These weld overlay repairs were ground to improve surface finish and enhance inspectability in !

1987, as recommended by Reference (2). The original design and analysis of the recirculation system weld overlay repairs is presented in (3) and is summarized in Section 2.

l In order to ninimize the potential for continued IGSCC, the New !

York Power Authority (NYPA) has treated those welds in the recirculation system which are potentially susceptible to IGSCC with residual stress inprovement processes (induction heating stress improvement (IHSI) or resistance heating stress improvement (RHSI]). Also, NYPA is planning to implement a hydrogen water chemistry program, which will further inhibit IGSCC initiation and growth.

A section of piping containing IGSCC was removed from the RKx system suction line in 1987, and the removed piping spool was replaced with piping of an IGSCC-resistant material. In ,

addition, the 4 inch recirculation bypass lines were removed and capped. The purpose of these activities was to minimize the IGSCC susceptibility of the recirculation system and related systems. >

l-1 gg INTEGRITY ASSOCIATESItC

During the Spring 1987 outage, flaws requiring repair were identified at three locations in the 10 inch core spray system loop B. These locations were repaired with weld overlays designed in accordance with the requirements of NUREG-0313 Revision 2 (Draft). However, the surfaces of these three repairs I were not ground, since the NYPA is considering replacement of the I affected lines in 1988. If the Authority decides not to replace the lines during the 1988 outage, the piping will be replaced during the September 1989 maintenance outage.

1 l

The design and application of the repairs to the core spray system is discussed in Section 2.

1.2 U.S. Nuclear Regulatory Commission (NRC) Position on Weld overlay Life Extensien The published documents which contain the U.S. NRC position for repair of IGSCC flaws in operating plants include Generic Letter l 84-11 (1) and NUREG-1061 (Volumes 1 & 3) (5). In addition, !

Revision 2 of NUREG-0313 (2) consolidates the regulatory position represented by the previous documents, and includes recent regulatory actions and research results.

Although the position stated in Generic Letter 84-11 is that weld overlays on circumferential1y-flawed pipe are acceptable for a maximum of two fuel cycles, the USNRC has recently been receptive l to extending that limit on a case by case basis. To date, two plants have received positive responses from the NRC on their j

plans for weld overlay life extension. These plants have as many '

as 35 weld overlays in place in their recirculation and associated piping systems. Some of these overlays will be going into operation for a fourth fuel cycle, and have seen up to five years of service.

Reference (2) provides new guidelines for crack evaluation and repair, including specific provisions for extended use of weld 1

1-2 STRUCTURAL INTEGRITY ASSOCIATESINC

overlay repairs. It recognizes that, with proper attention to overlay surface finish, effective ultrasonic inspection methods are now available which can detect cracking in or near the overlay. It permits long term operation of weld overlay repaired welds, with the provision that they be inspected ultrasonically, using qualified NDE examiners and procedures, every two refueling cycles. Similar provisions will apply to unrepaired cracked welds, except that the inspection frequency is each refueling cycle, unless they have been treated with a stress improvement remedy such as IHSI. These provisions of NUREG-0313, Rev.;sion 2 more closely reflect what has been the NRC approach in case by case licensing reviews.

1.3 Purpose of Report The purpose of this report is to document the status of IGSCC mitigation and repair activities at J.A. FitzPatrick as of the Spring 1987 refueling outage. The activities addressed include surface finish improvement and re-evaluation of the six weld overlays which were originally applied to the recirculation system in 1984-1985. The design and as-built configurations of the three weld overlays applied to welds in the core spray B loop piping in 1987 are also discussed.

l The report provides technical justification for continued operation of the FitzPatrick recirculation system without pipe replacement. The justification is based on a detailed review of weld overlay designs and fracture mechanics analyses for the observed indications at FitzPatrick. It is also based on analytical and experimental results developed by the industry regarding weld overlay resistance to IGSCC crack propagation, the residual stress benefits of weld overlay application in crack arrest, and the strength and toughness of weld overlay material. I Section 2 of this report summarizes the inspection results, reviews the weld overlay design analysis for the six repaired 1-3 STRtJN INTEGRITY 4

ASSOCIATESINC

4 welds in the recirculation system, and compares the as-built I repairs to current practices and requirements. The design of the repairs to the three welds in the core spray system is also l included in this section. Section 3 discusses the pertinent technical issues involved in extended use of weld overlay

{

repairs, including experimental demonstrations of the IGSCC resistance of weld metal, residual stress analyses, and l experimental results for weld overlay repairs, IHSI remedies, and RHSI remedies. Discussion of weld overlay strength and toughness considerations, including recent test data from an NRC sponsored degraded pipe program at Battelle Columbus Laboratories, is presented in Section 4. Section 5 discusses the other IGSCC mitigation activities conducted or planned at FitzPatrick, l

including IHSI, RHSI, spool piece replacement, and hydrogen water I chemistry. Section 6 summarizes the status of IGSCC-susceptible welds at FitzPatrick, and Section 7 presents the report references.

i 1-4 STRUCTURAL INTEGRITY ASSOCIATEINC

2.0 WELD OVERLAY ACTIVITIES AT FITZPATRICK 2.1 Weld overlay Repairs in the Recirculation System The six weld overlay repairs which have been applied to locations in the recirculation system were designed and applied in 1984-85.

Although the design bases for these repairs was in keeping with the design practice common at the time, the regulatory guidance concerning weld overlays has changed since these repairs were !

applied. In order to justify continued operation of FitzPatrick with these repairs in place, the repairs were re-evaluated to current criteria. As recommended by Reference (6), the surfaces of these repairs were smoothed by grinding to allow ultrasonic )

4:,.3mination of the weld overlay volume and a portion of the l underlying pipe wall. The as-built repair thickness following the surface finish improvement was used in the re-evaluation, to demonstrate that the existing weld overlay repairs were adequate by current criteria for continued service. l l

l 2.1.1 Evaluation Criteria from NUREG-0313 Revision 2 ]

l NUREG-0313 Revision 2 (2) contains the latest published criteria for extended service with weld overlay repairs. Weld overlays are categorized by their design basis to determine their long term acceptability. A weld overlay designed to repair a circumferentially-oriented 3600 long through wall flaw is classified as a "standard " weld overlay. Such an overlay repair is considered acceptable for use as a long term repair, provided that the weld overlay and some portion of the underlying component wall are inspectable (e.g., by ultrasonic examination).

Other factors which must be considered in demonstration of extended serviceability include the IGSCC resistance and l toughness of the weld overlay material and the applied stresses at the repaired location.

2-1 gg INTEGRITY ASSOCIATESINC

\

2.1.2 criteria for Inspection l

l The purpose of volumetric inspection of weld overlay-repaired locations is to demonstrate that the design thickness of the overlay has not been degraded due to continued flaw propagation.

It is, therefore, desirai.e to show that a flaw has not grown into the weld overlay metal. Ideally, it should be possible to 1 demonstrate that the original flaw which led to the necessity for I the repair has not grown since the time of the repair.

Studies conducted by EPRI (6) have demonstrated that ultrasonic examination of the weld overlay volume and approximately the outer 25% of the underlying pipe wall is possible if the surface of the weld overlay is smoothed to a finish of 250 rms, with a flatness of 1/32 inch or better. These requirements generally make grinding or similar operations necessary.

2.1.3 Evaluation of Recirculation System Weld Repairs The surface finish of the six recirculation system weld overlay repairs was improved in Spring 1987 to levels which met the EPRI criteria discussed above. The thickness of the weld overlays was then measured and compared with the design thickness which would '

be required to qualify the repairs as standard weld overlays as l defined in Reference (2). In all cas.es the as-built weld overlay '

thickness exceeded the minimum design thickness based upon the i

NUREG-0?13 Revision 2 criteria.

The design basis flaw employed in the re-evaluation was a circumferentially-oriented flaw extending through the original pipe wall for a length of 3600 That is, no credit was taken for the load carrying capability of the remaining uncracked pipe ligament. Stress components due to pressure, deadweight and seismic (OBE) loads (7) were considered in the section XI stress ratio defined in IWB-3641 (8) to determine the required overlay thickness to qualify the repairs as sts.ndard weld overlays as 2-2 STRUCTURAL INTEGRITY AssocuMEINC

. 1 l

defined in Reference (2). The stress components are listed in Table 2-2. No credit was taken for the first welded layer in :

meeting the required overlay thickness. 1 l

The re-evaluation demonstrated that the as-built weld overlays exceeded the design minimum thickness defined by analysis to current criteria in all cases. Table 2-1 lists the required (new criteria) and as-built dimensions for each of the recirculation l weld overlays.

2.2 Weld Overlay Repairs in the core Spray System During'the in-service inspection of IGScc susceptible welds at FitzPatrick in Spring 1987, flaws . requiring repair were identified in three welds in the 10 inch diameter core spray loop B piping. Weld overlay repairs were designed in accordance with

, the requirements of Reference (2). The observed flaws at each location, the design dimensions, and the as-built data for each weld are summarized in Table 2-3. Unlika the weld overlays on the recirculation system, the core spray repairs were not ground to improve surface finish.

These repairs are being treated as temporary repairs at this time, since NYPA is considerir.g replacement of the cora spray loop B piping during the next refueling (1988) or maintenance outage (1989). The following paragraphs discuss the design and application of the core spray repairs, and the as-built data taken at the repaired locations.

The affected locations are in lo inch stainless steel piping with nominal wall thickness of 0.593 inch. None of these locations

'have been treated with induction heating stress improvement l

(IHSI) or similar process. The applieu stresses for each of the locations were taken from Reference (9) and are summarized in Table 2-4. '

Weld overlay repairs for the affected locations were designed i

based upon the guidance of Reference (2). In particular, the 1 3

i 2-3 STRUC"IllRAL l Drramwrf i

ASSOCUCTSIC ,

I h l

repairs for welds 493 and 496, which contain circumferentially- )

oriented flaws, were designed to meet the requirements of the "standard weld overlay" as defined in paragraph 4.4.1 of the '

NUREG. In the design process, no credit was taken for the remaining unflawed original pipe u.aterial. The weld overlay repair for weld 495, which contains only axially oriented flaws, was designed as a leakage barrier or "designed weld overlay", as defined in paragraph 4.4.2 of Reference (2].

Weld overlays were designed in accordance with the criteria of ASME Section XI, Article IWB-3641, 1986 Edition (8). The primary stresses listed in Table 2-4 (pressure + dead weight + seismic) were used. The allownble stress from ANSI-ASME B31.1 (15.9 ksi)

(10) as taken from (7), was used in the overlay design process rather than the Section III allowable S, (16.95 ksi), for l I

additional conservatism.

T'le veld overlay design calculations for welds 493 and 496 were performed using the proprietary computer code pc-CRACK, which automates the Section XI calculations. The pc-CRACK calculations for these welds are attached as Tables 2-5 and 2-6, together with design sketches for the repairs (Figures 2-1 and 2-2). The design thickness for these welds does not include the first weld layer acceptable by dye penetrant inspection.

The weld overlay repair for weld 495 was not required to restore 1 I

structural adequacy to the weld, since the weld contains only l axially-oriented flaws. This repair was required by Reference l (2) to be two welding layers thick, beyond the first surface to pass a dye penetrant examination.

Weld overlay length was determined for all three repairs by two independent factors. The first of these was that the repair must be long enough to provide adequate structural reinforcement of 2-4 STRUCTURAL INTEGRITY ASSOCIATESINC

~

1 0

the flawed location. For this purpose, the minimum full thickness length of the repair was taken as:

L = 1.54Rt , or approximately 3 inches for the purposes of the design. The second consideration was that the overlay must be long enough to allow adequate ultrasonic inspection through the weld overlay. The necessary length to support inspection was determined in the field.

2.3 Evaluation of Flawed Welds for Acceptance without Repair During the inservice inspection of the recirculation system at FitzPatrick, as a part of the 1987 refueling outage, flaw ,

indications were identified at seven selds, as shown in Table 2-7 )

[4). Stresses from the design stress report [7] are also shown I in Table 2-7. These welds had all previously received IHSI treatment.

The seven welds in Table 2-7 were evaluated for possible IGSCC flaw growth of the indications (after IHSI), and for flaw acceptance margin in accordance with ASME Section XI, IWB-3640

[8). The evaluations were done in accordance with NUREG-0313, Rev. 2 (Draft) (2) procedures, as shown in the Tables 2-7 and 2-8 and the attached pc-CRACK analyses (Appendix A). Since the flaw indication lengths reported for welds 28-53 and 28-113 exceeded 10% of the pipe circumference (per NUREG-0313, Rec, 2 guidance),

crack growth analyses were also performed for the assumed as-welded condition for these two welds. All weld residual stress distributions 'used in the crack growth analyses were in accordance with Reference (2) and earlier flaw evaluations done for these welds at FitzPatrick (Reports SIR-84-038, Feb. 4, 1985 (11) and SIR-85-015, Rev. 1, May 7, 1985) (3).

The results of the above flaw evaluations are summarized in Table 2-8. It can be seen that no IGSCC crack growth is predicted in 2-5 STRUCTURAL INTEGRITY ASSOCIATESN3

any case for the post-IHSI welds. Furthermore, there is ample margin between the current indication sizes and the Section XI allowable flaw sizes, even assuming low toughness SAW welds, and flaws as much as 30% of the pipe circumference in length.

As mentioned, welds 28-53 and 28-113 were also evaluated for the as-welded case because of flaw lengths in excess of 10% of circumference. In 40,000 hr. (about 4.5 yr) these flaws were predicted to grow from 15% and 18% of wall in depth, to 42.8% and 42.6% of wall in depth, respectively. These predicted flaw depths are still below the section XI allowable flaw depths of 60% of wall, even if the flaw is assumed to be 30% of the pipe circumference in length.

Thus, the above flaw indications in the seven welds are judged acceptable at this time without further repair.

2-6 STRUCTURAL INTEGRITY ASSOCIATESINC

\

.~ l l

. Table 2-1 l

Weld Overlay Repair Dimensional Data for Recirculation System Repairs 12.B.Z l

l Year D2 sign Design As-Built 2 Weld i ADDlied Lenath! Thickness! Lenath Thickness 2 ,4 (in.) (in.) (in.) (in.)

12-12 1984 3.00 0.32 2.893 0.47 12-23 1984 3.00 0.24 3.36 0.48

)

12-64 1984 3.00 0.28 2.953 0.61 )

12-69 1984 3.00 0.29 *s.25 0.45 12-70 1984 3.00 0.24 3.37 0.30 l 22-22 1985 4.87 0.35 5.29 0.58 i NOTE: 1 1

ALL WELD OVERLAYS WERE RE-EVALUATED TO CURRENT CRITERIA IN 1986.

2 ALL WELD OVERLAY SURFACES WERE IMPROVED IN 1987. AS-BUILT !

DIMENSIONS ARE AFTER SURFACE IMPROVEMENT. j a

LENGTH AT DESIGN THICKNESS = 3.1 inch FOR WELD 12-12 AND 3.3 INCHES FOR WELD 12-64.

4 AS-BUILT THICKNESS DOES NOT TAKE CREDIT FOR THE FIRST PT CLEAR WELD IAYER.

l l

l 2-7 STIHJN I INTEGRITY ASSOCIATESDC

l l

\

s l

.. i l

Table 2-2 Summary of Recirculation System Pipir.g Stresses **

at Weld Overlay Repair Locations i

Weld No. Joint No.* Pressure Dead Weight Seismic (Psi) (psi) (psi) 12-12 194 4921 1426 4732 12-23 215 4778 263 952 12-64 24 4528 360 3288 ;

12-69 64 5210 1486 3750 '

12-70 65 4726 210 1185 22-22 NA 6480 0 0 1

Nodal numbers from Reference (7) l

- Based upon stress from Reference (7); normalized to measured wall thickness l

l l

l 2-8 STRtJN INTEGRITY AssocunEsac

TABLE 2-3(a)

INSPECTION RESULTS IN CORE SPRAY WELDS I

WELD INSPECTION RESULTS 10-14-493 CIRCUMTERENTIAL: 2.9 inches Long X 29%

Deep 10-14-495 AXIALS: 0.5 inch Long X 78% Deep 10-14-496 CIRCUMFERENTIAL: 3.9 inches Long X 38%

Deep l

l l

l 2-9 gg INTEwurf ASSOCIATES;NC

TABLE 2-3(b)

Weld Overlay Repair Dimensional Data for Core Spray System Repairs YEAR DESIGN DESIGN AS-BUILT WELD # APPLIED LENGTH THICKNESS LENGTH THICKNESS ,2,4 (in.) (in.) (in.) (in.)

10-14-493 1987 3.00 0.200 3.11 0.27 3

10-14-495 1987 3.00 0.125 3.80 0.162 10-14-496 1987 3.00 0.200 3.44 0.293 Note:

1. SURFACE FINISHING HAE NOT BEEN PERFORIiED. l

2. THESE WELDS ARE ON THE CORE SPRAY "11" PIPING LOOP. THIS PIPING IS SCHEDULED TO BE REPLACED.

3. LEAKAGE BARRIER ONLY.

I

4. AS-BUILT THICKNESS DOES NOT TAKE CREDIT FOR THE FIRST PT CLEAR LAYER 2-10 STRUCTURAL INTEvaurlfE ASSOCIATES

TABLE 2-4

SUMMARY

OF CohE SPRAY SYSTEM PIPING STRESSES AT WELD OVERLAY REPAIR LOCATIONS l

l STRESS COMPONENT (psi) !

HELD PRESSURE DEAD WEIGHT SEISMIC (OBE) TOTAL l l

10-14-493 4746 39 1232 6017 l

\

10-14-495 4746 96 922 5764 10-14-496 4746 109 1356 6211 I i

1 l

2-11 STRUCTUlmL

%V lb

I

.. l Table 2-5 l Reinforcement Sizing Calculation for Core Spray Weld 10-493

. tm pc-CRACf.

(C) CCFYRIGHT 1954, 1996 STRUCTURAL INTEGRITY AEECCIATEE, INC.

SAN JOSE, CA (408)978-8200 VEREION 1.1 WELD OVERLAY SIZING EVALUATION WEL1; OVERLAY SIZING FOR CIRCUMF. CRACK, WROUGHT / CAST STAINLESS STANDARD WELD DVERLAY FOR WELD 10-14-493 ,

WALL THICKNESS = 0.5930 ,

MEMERANE STREd5= 4746.0000 SENDING STREES= 1271.0000 STREES RATIO = 0.3784 ALLOWAELE STRESS =15900.0000 FLOW STRESS =47700.0000 L/ CIRCUM O.00 0.10 0.20 0.30 0.40 0.50 FINAL A/T O.7500 0.7500 0.7500 0.7500 0.7500 0.7500 OVERLAY THICKNESS 0.1977 0.1977 0.1977 0.1977 0.1977 0.1977 1

EM 2-12

Table 2-6 Reinforcement Sizing Calculation for Core Spray Weld 10-496

. +m p c-CR AC) . !

(C) CCFYRIGH1 1954, 1966 STRUCTURAL INTEGRITY ASSOCIATES, INC.

SAN JOSS, CA (408)978-S000 VERSION 1.1 WELD OVERLAY SI2ING EVALUATION WELD OVERLAY SIZING FOR CIRCOMF. CRACK, WROUGHT / CAST STAINLNES .

STANDARD WELD OVERLAY FOR WELD 10-14-496 NALL THICKNESS = 0.5930

.MEM&RANE STRESS = 4746.0000 .

BENDING STRESS = 1465.0000 STRESS RATIO = 0.3906 ALLOWABLE STRESS =15900.0000 ,

FLOW STRESS =47700.0000

, L/CIRCUP.

80.00 0.10 0.20 0.30 0.40 0.50 FINAL A/T 0.7500 0.7500 0.7500 0.7500 0.7500 0.7500 OVERLAY THICKNESS 0.1977 0.1977 0.1977 0.1977 0.1977 0.1977 END OF pc-CRACK M

2-13 WTEGRTTY -

ASSOCIATESINC

Table 2-7 1987 Flaw and Stress Data for Seven Recirculation System Welds (Ref. Design Stress Report 22A2622, Rev. 1) [7]

P B

Flaw Flcw a P+DW*** DW -

Weld Node Pipe Pipe Depth Length P** TE +TE OBE No. No.__ ODfin) IDfin) fin /% Wall) fin /t Circ.*) (ksil iksil (ksil (ksil 12-4 2f8 12.662 11.442 7.5% 2"/5.3% 5.676 8.123 14.030 3.835 12-61 14 12.662 11.442 0.06*/10% 0.5"/1.3% 5.676 14.286 19.632 3.252 28-48 324 28.363 25.867 0.25"/20% 1.5"/1.8% 5.685 1.270 6.772 4.257 f

28-53 331 28.363 25.867 0.22"/17% 12"/14.1% 5.685 0.847 6.985 1.850 28-56 334 28.363 25.867 0.26"/20% 2.5"/2.9% 5.685 0.693 7.150 2.315 28-112 175 28.363 25.867 0.20"/17% 4.75"/5.6% 5.685 0.686 6.899 - 1.736 '28-113 176 28.363 25.867 0.23"/18% 13"/15.3% 5.685 0.587 6.876 2.199

% circ. based on average of OD and ID

( '2 , where p = 1150 psi for suction and (OD)2 -

(ID)2 I**computedfromP=

i 1275 psi for discharge

- - combined loading taken from design stress report si 4, 4

Table 2-8 FitzPatrick Flaw Evaluation Results Predicted Allowable Flaw Flaw Flaw Depth Flaw Depth Weld Depth Length in 40,000 hr. for L/Cire. - 0.3 No. Condition fin /% Wall) fin /% Circ.) it Walll* ft Wall)**

12-4 Post-IHSI 7.5% 2"/5.3% 7.5 36.86 12-61 Post-IHSI J.06"/10% 0.5"/1.3% 10.0 17.33***

28-48 Post-IHSI 0.25"/20% 1.5"/1.8% 20.0 54.86 2C-53 Post-IHSI 0.22"/17% 12"/14.1% 17.0 60.00 As-Welded 0.22"/17% 12"/14.1% 42.8 60.00 i' 28-56 Post-IHSI 0.26"/20% 25"/2.9% 20.0 60.00 0

28-112 Post-IHSI 0.20"/17% 4.75"/5.6% 17.0 60.00 28-113 Post-IHSI 0.23"/18% 13"/15.3% 18.0 60.00 A=-Walded 0.23"/18% 23"/15.3% 42.6 60.00

Assumed as 360* Flaw for Crack Growth Analysis ASME Section XI, IWB-364C Evaluation for SAW

- - - - Allowable Flaw Depth for L/Cire. = 0.10 is 44.03% Wall I

l t._, L '

L ._ !

l=(2)1.(2)5' i = 1./5VELO 3

i " lTRANSITION ANGLE (3) n l l

l f)p///gv;gp;?M ~ ~ ~ ~ ~ ~ ~ T= 0.2' MIN (1) ,,

v PIPE VALL PIPE i EL90V (WITH INSTRLHENT LINE) 1 I

wild cantarline VELO OVERLAY DESIGN DESIGN FOR VELO NUMEER 10-14-453 i

N0ies:

TH SLGN Oyn

1. giEijN TH.g gE" {S 0.2 Ib*THSgi 16 ENTFhi:

A i H 11 El Ir! O 10kLENT.!'1 D

LE GiH A A! AE55kRY kXh N n-50lRED hfk T

L Y .A DA E hkY hhkhh! bit I SPECil0N

3. MAXIMUM VE!.0 TRANSli10N ANGLE IS 45 CEGREES.

)

DESIGN NUNSER : NYFA-12-5-19 REVISION : 0 DATE 2-16-37 PRE?ARED BY/ DATE M I O/ 2 '6 1 7 REVIEVED BY/ DATE [h b k W / Z -I E~f 7

Blend of Overlay'to Instrument Line Fitting is Shown in Drawing NYPA-12-5-1A.

ri ure 2-1.

,,aa y ggj7ggpr Desir. sxeten ror core 2-16 i

lv t__. L 'La VELO TRANSITION ANGLE (3) l=(2)1.

i l(2)5' i = 1./5' l i

I I g

jzwiyxzwAJ ~ ~ ~ ~ ~ ~ ~ ~ T = 0. 2" (l) ___

/ V PIPE VALL Pl?E ! ELBOY l

i I

veld centerline VELD DVERLAY DESIGN DESIGN FOR VELD NUMBER 10-14-496 NOTES:

h! Y h

eke 'Ukb REV khi

! 'F A H NLM M Fi) i TH CKNE NGTH THIS Sg t

2. Lg? g E ,il ASED S N CE5s YT ALL Y A EQUAT

3. HAX HUM VELD TRANSITION ANGLE IS 45 DEGREES.

DESIGN NUMBER : NYP 5-3 REVIS!0N: 0 DATE 2-16-07 PREPARED BY/ OATE YN / d'6 87 REVIEVED BY/ DATEM*-h N'012-4-f 7 ,

Tigure 2-2.

Weld Overlay Repair Design Sketc). for Core Spray Weld 10-496 gyg 2-17 ASSOCIATEEINC

3.0 DISCUSSION OF MAJOR TECHNICAL ISSUES 3.1 Weld Metal IGSCC Resistance operating experience with Type 308 and 308L weld metal in BWR service indicates that these materials possess inherently high resistance to IGSCC. Despite the fact that residual stresses are generally higher in the weld itself than in the heat-affected zone (HAZ) of the pipe wall, no leakage has ever been observed to result from cracks propagating through weld metal.

Recently, however, the intended use of weld overlays for extended plant service has prompted a more comprehensive examination of weld metal resistance to IGSCC. The results of industry-sponsored laboratory investigations have added considerable confidence in the behavior of 308 and 308L veld metal as a crack arrest barrier in the BWR service environment.

Additionally, these recent test results have provided a more quantitative understanding of the relationship between weld metal microstructure and the observed cracking behavior in both field and laboratory examples.

The recent data confirm that Type 308L weld metals (less than 0.02 wtt carbon) typically used in weld overlay repairs are !

immune to IGSCC when they have minimum ferrite contents of I approximately 5 or 6 FN. Type 308 weld metal, on the other hand, would require approximately twice this ferrite content for a similar level of resistance to cracking, based upon limited j Jaboratory test data. Field experience as well as laboratory data show that Type 308L weld metal with appropriate ferrite i content will consistently arrest propagating IGSCC, even under severe load and environmental conditions. The low carbon weld metal possesses far greater resistance to cracking than the weld metal chemistries typically used in original plant construction. l 3-1 gg i INTEGRITY ASSOCIATESINC l

Wolds at FitzPatrick were weld overlay repaired by the automatic gas tungsten arc welding technique using bare ER308L stainless steel wire containing 0.02 wt% carbon maximum and 8FN ferrite minimum. In addition, the first overlay layer was not included in the design as an IGSCC resistant layer because of the possibility of weld metal dilution and compositional changes in this layer. This approach very conservatively provides that a full structural weld overlay consisting of Type 308L stainless steel containing 0.02 wt% carbon maximum and 8FN ferrite minimum is available to arrest a growing IGSCC. All laboratory and field data developed to date support the engineering judgement that this material is able to arrest growing IGSCC which may have propagated to the overlay / base metal interface.

3.1.1 Field Ltperience (A) Weld Metal Cracking in Recirculation Piping at Nine Mile Point Unit 1 Following the removal of the recirculation system piping at Nine Mile Point Unit 1 in late 1982, metallurgical analyses were performed to characterize the depth and mode of cracking in the Type 316 stainless steel base metal. These analyses revealed that in two of the 28 inch diameter girth weld samples, cracking had penetrated into the weld metal. Figures 3-1 and 3-2 (12) illustrate cracking which initiated in the pipe material and propagated into the weld metal.

Also shown in Figures 3-1 and 3-2 are the respective ferrite measurements in the welds measured in both the horizontal and vertical orientations using a ferritescope. It is seen that the weld metal regions through which the crack propagated in Figure 3-1 were of relatively low ferrite (3.8% to 4.2%). Figure 3-2 presents photomicrographs from the second NMP-1 specimen. Again, in this specimen, ID-initiated IGSCC in the parent metal appears to have propagated into weld metal with measured ferrite levels 3-2 STRUCTURAL INTEGRITY ASSOCIATESINC

between 3% and 6%. No data on the carbon content of these welds is available at this time.

Figure 3-1 shows that the crack has propagated through the approximate mid-plane of a repair weld volume, thus posing questions about the possible contributory role of hot cracking in this weld defect. Since weld metal microfissuring or hot tearing tendencies are usually increased in such repair geometries, the extent and location of the cracking are definitely suggestive of a preferential crack path. Nonetheless, the crack appears to have propagated in an interdendritic manner from ID-initiated IGSCC through a substantial amount of veld metal. It, therefore, has the main characteristics of an environmentally-assisted crack.

(B) Weld Metal Cracking in Quad Cities Core Spray Line Metallurgical analysis of a cracked core spray line from Quad Cities Unit 2 (13) revealed axially-oriented IGSCC that had propagated transversely into weld metal. Figure 3-3 shows the interdendritic morphol;gy of this weld metal cra~ king.

Analysis of the weld indicated that the material was Type 308 stainless steel with about 5% ferrite. The analysis further revealed that the carbon content of this material was 0.064 wt%.

This observation provides additional evidence that carbon content is also an important factor in the IGSCC resistance of Type 308 weld metals with ferrite contents of up to 6% or 7%.

As will be discussed in the following sections, these examples of field experience are fully consistent with the results of laboratory cracking tests. With the exception of cracking in low ferrite, high carbon weld metal such as the cases above, destructive metallurgical examinations and field experience fully support the premise of the IGSCC resistance of 308L weld metal.

3-3 STRUCITTRAL INTEGRITY ASSOCIATESINC

3.1.2 Laboratory Experience (A) General Electric Weld Metal Tests As part of a test study to evaluate the structural stability of large diameter pipes containing IGSCC (14), fracture mechanics (IT-WOL) specimens were fabricated from Type 304 stainless steel plates welded with Type 308 and Type 308L electrodes of varying ferrite levels. The specimens were load cycled in high temperature water ccntaining 6 ppm 02 with an initial AK of 26 ksi (in)1/2 at an R of 0.05, where R is the ratio of minimum to maximum cyclic load. The specimens were on test for 5448 hours0.0631 days 1.513 hours 0.00901 weeks 0.00207 months .

Failure analyses performed at the conclusion of the tests revealed that IGSCC, which had initiated in the base metal, penetrated the weld metal in six of the seven specimens. In all but one case, the crack had arrested in the weld metal following some penetration. For the Type 308L specimens containing from 5.5 to 11.5% ferrite and 0.025 wt% carbon, the penetration into the weld was a maximum of 0.031 inches before crack arrest.

Branches of the primary crack continued to propagate in the wrought Type 304 along the weld HAZ, parallel to the weld / base metal interface.

For the Type 308 welds, the low (1.9 -

3.3%) ferrite and high (9.5 -

11.5%) ferrite welds exhibited an average penetration of 0.104 inch and 0.045 inch respectively, followed by crack arrest.

The crack in the medium ferrite content Type 308 specimen l

(containing 7.0 to 8.5% ferrite) penetrated 0.101 inch into the )

weld metal but showed no evidence of arresting. The carbon level for the Type 308 SS weld metal was 0.053 wtt. i l

l These test results are in agreement with the field experience I summarized above. Carbon content is seen to be a very significant factor in weld metal cracking resistance, in addition l

3-4 STIRJN l INTEGRITY ASSOCIATESINC i

v to ferrite level. Type 308L weld metal exhibits markedly better

. IGSCC resistance than the higher-carbon Type 30e.

In addition to the General Electric crack propagation work for weld metal described above, the Alternative Materials Program (15) provides striking evidence of the ability of Type 308 stainless steel weld metal to resist IGSCC propagation even in creviced BWR-like environments.

In the Alternative Materials program, plate welded (IT-WOL) fracture mechanics specimens of the candidate alternative materials (including nuclear grades Type 304 and Type 316 stainless steels) were fatigued and bolt loaded in an autoclave and tested for more than 10,000 hours0 days 0 hours 0 weeks 0 months at 5500 F in high purity oxygenated water. The alternative materials all exhibited extensive IGSCC extension in the test. Several photomicrographs illustrating the extensive crevice corrosion crack growth in the alternative alloys are presented in Figures 3-4 through 3-6.

11ote in Figure 3-4 that although the original fatigue terminated in weld metal, no significant crack extension was observed in the weld metal, Yhereas substantial IGSCC crack extension occurred in the Type 316L SS sample 'containing 0.026 wt% carbon). Figure 3-5 also shows that crack penetration into wold metal was minor, whereas substantial IGSCC growth occurred in the Type 316!1G SS material. In Figure 3-7, a crack which inadvertently was grown -

into weld metal was observed to arrest with no measurable crack extension. Although the initial stress intensity on this specimen was only about one-half of that for the alternative material specimens, 25 kai (in)1/2 versus 45 ksi (in)1/2 , the fact that no crack growth was observed provides striking evidence of the excellent resiotance of weld metal to IGSCC growth. It is believed that several of the weld filler samples were Type 308L SS with 8% ferrite minimum, as that was the weld filler specified by General Electric at that time for plant piping. This has been confirmed by General Electric Ccmpany (16).

3-5 STRUN INTEGRITY ASSOCIATEINC

(B) Inverse IllSI Pipe Teste As part of recent EPRI efforts to detect and size IGSCC in austenitic stainless steel pipe welds, a group of 12 inch pipe samples of Type 304 material were fabricated by Ishikawajima liarima ficavy Industries (17). These specimens contained girth welds and were inverse-IllSI treated to produce deep IGSCC when exposed to high purity, oxygenated, 550 0F water. One of these samples developed an IGSCC which penetrated the pipe wall and extended several millimeters into the weld. The pipe specimen was metallurgically examined for level of sensitization and for ferrite content. The examination revealed that the weld metal was highly sensitized (probably due to a 5000 C/24 hour Low Temperature Sensitization (LTS) treatment). Further, the weld metal was determined to be Type 308. The weld metal cracking was observed to terminate when the direction of the dendrites made an abrupt change. The initial weld metal crack propagation occurred in approximately 5% ferrite material and appearad to terminate in approximately 9% ferrite material.

(C) Weld Overlay Repair Large Diameter Pipe IGSCC Crack Growth Test The BWR Owners Group (BWROG-II) and EPRI (EPRI Project T303-2)

(18) are sponsoring an IGSCC pipe test program examining the effectiveness of residual stress remedies in retarding or arresting IGSCC crack growth in large diameter Type 304 stainless steel pipe welds. Two 24 inch diameter 1.2 inch wall thickness, Type 304 stainless steel pipes each containing two test welds were tested. One of the pipes was IGSC cracked by loading to an axial load of approximately 18 kni in 5500 F high purity water containing 6 ppm 02 The IGSCC pre-cracking required cpproxi-mately 4000 hours0.0463 days 1.111 hours 0.00661 weeks 0.00152 months under test at load.

Following the 4000 hour pre-crack exposure, this pipe was returned to test, and crack growth occurred in both joints over 3-6 STRIJC111T E INTEGRITY ASSOCIATESINC

an additional approximately 6000 hours0.0694 days 1.667 hours 0.00992 weeks 0.00228 months on test. The pipe was removed from test, the crack locations were documented by UT and PT, and a full structural weld overlay was applied to one of the joints. The weld overlay was designed to be approximately 0.29 inch thick.

At the present time, the weld overlay testsd joint has been on test for 3000 hours0.0347 days 0.833 hours 0.00496 weeks 0.00114 months since the wold overlay application. No additional IGSCC initiation has occurred in this wold since the application of the weld overlay, as observed by UT and PT.

Furthermore, no apparent change in crack depth has occurred in the existing IGSCC since the weld overlay was applied.

The companion as-welded reference joint has accumulated approximately 5000 hours0.0579 days 1.389 hours 0.00827 weeks 0.0019 months on test since the IGSCC was f.1rst observed. During that time, the deepest cracks have grown to approximately 250 to 300 nila in dept't. The crack growth rate is slowing measurably as determined by bT and acoustic emission, and the deepest cracks appear to be arresting. Additional ID crack initiation and lengthening of previously initiated cracks is taking place in this reference weld c. s determined by UT and liquid penetrant measurement.

(D) EPRI/ General Electric Pipe Tests Another part of the BWROG-II remedies and repairs program (T302-1) (19) is being conducted at the GE pipe teot facility.

Pipes of 4 and 12 inch diameters are being pre-cracked under exposure to high stress in simulated BWR conditions. The resultant pre-remedy IGSCC defects range from 10% to through-wall penetration. Various specimens are then troated with weld overlay, IHSI or LPHSW remedies. TI e tests are designed to measure the effectiveness of these remedies in arresting the 1 growth of pre-exir. ting IGSCC.

l

)

l 3-7 STRUCTURAL INTEGRITY ASSOCUGEINC !

Two of the 4 inch Schedulo 80 pipes have roccived weld overlay repairs to several joints following pre-cracking by IGSCC in a simulated BWR ensironment containing 0.2 ppm 02 at 550 0F. The pre-cracks were sized by UT , and weld overlay repairs were performed in both pipes as presented in Table 3-1. The pipes wera then returned to test in 9 ppm 02, 1.3 pS/cm water at 550 0F, and loaded to 1.3 S, following the weld overlay application. The two pipes have accumulated test exposures of 11,112 and 8,406 hours0.0047 days 0.113 hours 6.712963e-4 weeks 1.54483e-4 months on test respectively with no failures having been obnerved in any specimen in either pipe. (A failure is defined as a leak at a specimen location).

It is noteworthy that during application of the weld overlay repair to IGSCC pre-cracked joints in both pipes, through-wall cracks were observed at two joints. One joint containing 0 through-wall crack and a weld overlay repair (pipe RSP-14, 0.5T overlay in Table 3-1), was remover from test following 1000 additional hours on test with the weld overlay repair in place.

Optical metallography performed on this specir.en revealed that the weld overlay ef fectively arrested the chrough-wall IGSCC at the overlay / weld metal interface as is observed in Figure 3-8 (19).

In addition, two 12 f r.ch pipe specimens have been IGSCC pre-cracked and have raceived wold overlay repairs. A total of nine wold overlays have been applied to the two pipes. The pipes have accumulated 1,321 and 1,057 hours6.597222e-4 days 0.0158 hours 9.424603e-5 weeks 2.16885e-5 months on test since the weld overlay repair applications. No evidence of crack growth has been observed as of the publication of [20). Although these tests have been performed primarily to address the issue of residual stress benefit of v91d overlays, they are included here i for completeness.

l l

3-8 STRUCTURAL INTEGRITY '

ASSOCIAmilNC I i

3.1.3 Modelling Studies Based upon the preceding in-reactor and laboratory IGSCC studies, it is clear that Type 308 and 308L stainless steel wold motel exhibit superior IGSCC resistance compared to wtought Type 304 or Type 316 stainless steels. However, the field and laboratory data aJso illustrate that Type 308 stainless steel weld metal is not immune to IGSCC. The data from NMP-1 and Quad Cities 2 and the data at GE, IHI and Battelle Northwest suggest that ferrite levels of 5-9 FN alone may not be sufficient to clininate IGSCC propagation into wold metal. however, the crack arrest data on Type 308L SS weld metal suggest that combinations of carbon and ferrite level (and probably ferrite distribution) do exist where IGSCC crack propagation in austeno-ferritic weld metal is either extremely slow or nonexistent.

Devine (21) performed a laboratory study investigating the interaction effects among carbon lovel, ferrite level and :.errito distribution on the IGSCC susceptibility and sent zation immunity of Type 308 SS weld metal. This work involved not only the SCC testing and micrastructural characterization of Type 308 welds, but also included such studies on wrought Type 308 compositions. In this context, it is helpful to review these studies and the mechanism by which increasing ferrite mitigates IGSCC in austenitic stainless steel.

In (21), the beneficial ef fec".s of ferrite content in Types 308 and 308L wrought and weld-deposited compositions are discussed I with regard to IGSCC susceptibility and sensitization immunity.

As is generally believed, zones depleted of chromium due to the precipitation of chromium carbides during welding or furnace sensitization act as sites for potential IGSCC. Whereas chromium carbide precipitation occurs intergranularly during aging of I austenitic Type 308 stainless steel, no such precipitation occurs along austenite-austenite grain boundaries in duplex Type 308 I containing suitable amounts dnd distributions of ferrite.

3-9 STRUCTUllA1, '

INTEGRITY l ASSOCUGUINC

4 Instead, the precipitation occurs exclusively along austenite-ferrite phase boundaries. Since chromium diffusivity is approximately 1000 times greater in ferrite than in austenite at 1100 0 F, the chromium for this precipitation is supplied principally from the chromium-rich ferrito phase. A small zone of chromium depletion in the austenite is subsequently replenished by chromium diffusing from the interior .of the austenite. After this "healing", the material is immune to intergranular corrosion in ASTM A2G2 Practice E and IGSCC in air-saturated water at 550 0 F.

Models developed (21] based on the above mechanism describo IGSCC as a function of carbon content and the amount of ferrito-austenite (a-7) boundary area. The critical distribution of boundary area for rapid healing is that amount which is sufficient to tie-up all of the available carbon as chromium carbide exclusively along ferrite-austenite boundaries. Both the amount and distribution of ferrite-austenite boundary area can be expressed as a function of the metallographic parameter, li g '7 This is a measure of the number of intercepts a random test line makes with o-7 boundaries per unit length of test line.

Figure 3-9 shows the model predictions of lig ~7, as functions of

%C to maintain a critical amount of o-7 boundary area (line l Sy ~7) and a critical distribution of o-7 boundary area (curve 7

A). The value of li g ~7 for rapid healing is the higher of the l two curves; however, the straight line model for S y "~7 has been used (21] to describe IGSCC resistance over the complete range of carbon content for Type 308 compositions. ASTM A262 Practice E results shown in Figure 3-9 verify the model predictions. At

-1 g, 0.03%C, the maximum for Type 308L, li g ~7 of 100 to 200 cm required for rapid healing and immunity to intergranular corrosion. This translates to a ferrite level of about 3 wtt as shown in Figure 3-10. At 0.015% carbon, or less, essentially no 3-10 STRU(',I' URAL

- INTEGRITY a ASEMINC

ferrite is requiied to confer immunity to intergranular corrosion.

3.1.4 Model Results The Devine model, in conbination with field and laboratory data on the IGSCC behavior of Type 308 stainless steel weld metal, has been used as a guide to specify the maximum carbon level and minimum ferrite level necessary in Type 308L stainless steel weld overlay material to resist IGSCC growth into the weld metal. The model indicates that 0.03 wt% carbon and 3% ferrite should be sufficient. The laboratory test data confirms the model result and the field IGSCC data in Type 308 stainless steel veld metal are not in conflict with tho model estimates. However, to provide additional conservatism and to allow for some weld metal dilution or compositional estimating error, the BWR industry has generally specified that the weld overlay material Type 308L stainless steel contain no more than 0.02 wt% carbon and 8FN ferrite (approximately 8%).

3.2 Residual Stress Benefits Since their initial use on BWR pipe welds, weld overlays have been analytically shown to produce beneficial residual stresses in a variety of pipe sizes and joint configurations. Such analyses typically employ finite element thermal / stress modeling techniques to predict the behavior of the pipe material undergoing repair. Analytically, the application of a weld overlay repair is shown to produce highly compressive residual stresses through a major portion of the original pipe wall, thus i effectively arresting the growth of pre-existing IGSCC in the j pipe material. ,

i l

More recently, a number of laboratory programs have been undertaken in order to verify experimentally the effectiveness of weld overlays in arresting the growth of pre-existing cracks l l

l 3-11 EN INTEGRITY ASSOCIATESINC

und0r BWR c;nditicn3. Furth0rmora, C vCrol wold-0VCricy rcpnir:d pipes have been removed from plants and destructively analyzed after operational plant service with the overlays. The results of these new programs, coupled with previously reported data, provide overwhelming evidence that veld overlay repairs, in addition to being resistant to IGSCC crack propagation, Will also arrest further crack propagation in the original pipe weld, both in the through-wall depth direction, cud in the crack length direction.

The following subsections summarize some of the recent developments on the topic of weld overlay residual stress / crack arrest capability in the original piping material.

3.2.1 Georgia Power Company / Structural Integrity Associates (ST.)/ Welding Services Incorporated (WSI) 28-Inch Notched Pipe Test The objective of this project (22) was to verify the analyticilly-predicted residual stress benefits of an overlay repair on a large-diameter pipe weld joint with pre-existing defects. The test piece included a number of crack-like defects i of axial and circumferential orientation, in order to examine the l post-romedy residual stress state at the extremities of .

1 pre-existing flaws. Two sections of a 28 inch diameter, 1.5 inch j Type 316 stainless steel pipe were welded together using a joint configuration and welding procedures typical of those used in the original recirculation system piping fabrication at Hatch Unit 1. I Following the butt weld, a bottom plate of stainless steel was fillet welded to the pipe, so that the pipe could be used as a l self-contained boiling magnesium chloride (MgCl2 ) residual stress test (Figure 3-11). A stainless steel baffle plate was fillet l welded to the bottom plate and to the inside surface of the test pipe, so as to divide the test pipe into two equal halves. Axial and circumferential notches of varying depth were ground into the ID of the pipe at various locations ncar the girth weld. The 3-12 STRUCTURAI.

INTEGRITY ASSOCUGT. SINC

notches were introduced symmetrically in both halven of the pipe (Figure 3-12).

One half of the pipe was exposed to the boiling MgCl2 following the introduction of the notches. A structural weld overlay was then deposited over the outside surface of the entire girth weld and the entire pipe was re-exposed to the MgC12 solution. The

pipe was liquid penetrant inspected and sections were removed for metallurgical analysis following the liquid penetrant examination.

Figure 3-13 illustrates a typical result of this testing. Figure 3-13a shows a metallographic section of the tip of a moderate depth circumferential notch which was exposed to MgCl2 testing prior to weld overlay. The extensive cracking indicates the high level of tensile residual stresses present at this location.

Figure 3-13b shows a similar metallograph of the corresponding notch in the section of the pipe tested f'ollowing weld overlay.

11o MgCl2 cracking is apparent at the second notch tip, indicating that the weld overlay process reduced the notch tip residual stress to near-zero or compression. Essentially identical !

results were observed at every notch illustrated in Figure 3-12, both axial and circumferential, deep and shallow (i.e., extensive j cracking in the notches tested prior to weld overlay and no l cracking in the notches tested after weld overlay). These results and the entire test program are described in detail in (22). The tests thus confirmed that tensile residual stresses I were present in the vicinity of the axial and circumferential notches in the as-welded pipe. The tents also provided striking evidence of the effectiveness of weld overlays in producing compressive ID surface and through-wall residual stresses. The wold overlay produced compressive residual stresses at the tip of both .".xlal and circumferential defects; this was true in the case of both shallow and deep notches. In addition, the overlay was shown to produce ID-surface compressive residual stresses that would prevent any length extension of pre-existing IGSCC.

3-13 STRUCTURAL INTEGRITY ASSOCIATESINC

3.2.2 EPRI/GE Residual Stress Results The EPRI/GE Degraded Pipe Program, examining the effect of residual stress remedies on the crack propagation behavior and residual stress distribution of IGSCC pre-cracked 4 inch and 12 inch Schedule 80 pipe, has been underway for approximately two years (19, 20). The program has consisted of pipe tests, residual stress measurements by boiling MgC12 and finite element analysis examining the effect of a weld overlay repair on the IGSCC crack growth in these pipes. The pipe test results were discussed in Section 3.1.2 #D of this report. The residual stress results are described below.

Four 4 inch pre-cracked specimens with girth welds and containing IGSCC pre-cracks which were estimated to have depths as great as 60% of the wall Ehickness were weld overlay repaired using the parameters presented in Table 3-1. The IGSCC pre-cracks were produced by exposure of the welded pipe specimens to 550 0F, 200 ppb 0 2 simulated BWR water. Following the introduction of the pre-crack and depth measurement by ultrasonic techniques, the pipe samples were weld overlay repaired and exposed to boiling MgC12 to determine the residual stress state. F,llowing the MgC12 tests, liquid penetrant measurements were performed on all j pipe samples exposed, including those which had not received a weld overlay repair. The unrepaired welds exhibited extensive MgC12 cracking, while no liquid penetrant indications whatsoever were observed on the ID surface of the weld overlay repaired l

joints. Not even the IGSCC pre-cracks were observed by penetrant j examination following the weld overlay application. ;

3.2.3 Nutech/ Georgia Power Company 12-Inch Weld overlay Mockups Georgia Power Company, in conjunction with Nutech Engineers (23),

fabricated two weld overlay test specimens in conjunction with 3-14 STRUCTURAL INTEGRITY ASSOCIATEINC

1983 repair activities at plant Hatch. A total of three specimens were fabricated, one cach for a 0.20 inch overlay, a 0.23 inch overlay and a last pass heat sink weld (LPHSW). The weld overlay lengths were 4 inches. The weld overlays were applied to butt welds in short sections of 12 inch, Schedule 100, Type 304 stainless steel pipo using the same procedures, operators and e,quipment as were used for the in-plant repair work. Analytical predictions of residual stress based upon finite element studies were compared with measurements on the actual samples. The calculated and measured axial residual stresses are presented in Figures 3-14 and 3-15 for both weld overlay repaired pipes. Both the calculated and measured results indicate that the inner half of the repaired sections are in axial compression. The calculated residual stress results, however, are less compressive in general than the measured results.

3.2.4 EPRI/J. A. Jones 24-Inch Weld Overlay Mock-up A 24 inch Type 304 stainless steel pipe having a wall thickness of 1.48 inches receised a weld overlay repair at the J. A. Jones Applied Research Center as part of an EPRI/BWROG II sponsored effort to examine the effectiveness of the weld cverlay in providing favorable residual stresses in large diameter pipe.

The overlay consisted of a total of five weld layers constituting a total thickness of 0.35 inch. The overlay process was modelled by Nutech Engineers using the WELDS-II elastic-plastic finite element program (23). The experimental ID residual stressa measurements performed on this pipe following the weld overlay repair are presented in Figure 3-16. The through thickness analytical results are presented in Figures 3-17 and 3-18. The results of this residual stress analysis and measurement project illustrate that both axial and circumferential residual stresses are compressive at the pipe inside surface following a weld overlay repair of this thickness to this pipe. Further, the analytical results show that the residual stresses are expected 3-15 NCTURAL INTEGRITY Asscx:lAIESINC

4 to remain compressive to a depth of 50% to 70% of the composite wall thickness.

3.2.5 EPRI/BWROG II Pipe Tests The EPRI-funded projects RP T302-1 and T302-2 were discussed in the previous section (18-20) in regard to the evidence they produced in support of weld metal cracking resistance. These two laboratory programs are also mentioned here, beenuse of the significance of some of their results in terms of residual stress benefits:

T302-1 In general, weld overlays have been shown to be very effective in arresting the growth of pre-existing IGSCC in 4 inch and 12 inch specimens. In one case, a through-wall crack was ef fectively arrested during a 1000 hour0.0116 days 0.278 hours 0.00165 weeks 3.805e-4 months test; no increase in crack length or depth was observed during the test. These tests, including 12 inch specimens, are continuing.

T302-2 The 24 inch weld overlay specinens with pre-existing IGSCC has shown no detectable crack growth after more than 3000 hours0.0347 days 0.833 hours 0.00496 weeks 0.00114 months under test.

These tests are important in that they provide some of the most realistic weld overlay residual stress test data available, l outside of actual BWR in-plant repairs. The data indicate that weld overlays are very effective crack-arrest remedies, even under the severe stress and environmental conditions of these j l

tests.

3.2.6 Destructive Assay of Hatch Unit 2 Overlay Specimens at Argonne 11ational Laboratory (AllL)

Two weld overlay-repaired pipe-to-elbow welds were destructively examined at AllL (24). The welds had been overlay-repaired as a 3-16 STRUCITTRAL INTEGRITY ASSOCUtTSSINC

result of UT ind cat' ions during ISI at the !!atch Unit 2 facility,

. and were then returned to service for approximately one fuel cycle before removal from the plant. As will be discussed in detail in the next section, the ANL work was largely concerned with the hDE aspects of the wolo overlays. Ilowever, soveral observations that relate to this section were made during the ANL examinations.

Motallographic sectioning of the wolds showed that the application of the wold overlay had "blunted" deep cracks. There was no evidence of tearing or extension of the crack beyond the blunted region, which marks the crack depth at the time of the application of the overlay. The ANL report further states that finite element annlyses predict that crack growth will be inhibited by the overlay application.

This example of crack arrest (including the case of a very deep crack) was established by destructive assay of an operational pressure boundary repair. As such, both the reliability of this data and its importance in the technical discussion is great.

3.3 Non-Destructive Examination ha noced in the foregoing sections, the preponderance of both f!ald and laboratory data with stainless steel pipe welds has shown that weld overlays are very effective in establishing favorable material and residual stress conditions that arrest further growth of IGSCC in the BWR service environment. The material properties and configuration of the weld overlay, however, pose additional challenges for effectivo volumetric inspection of the original pipe wold joint.

I Recent developments in inspection technology have yielded significant improvements in through-overlay detection and sizing I capabilities. In addition to repeatable through-overlay detection of deep cracks, these recent developments appear to 3-17 STRUCTURAL INTEGRITY mWESINC l

offer the capacity to examine reliably the integrity of the

, overlay volume itself. These inspection developments have recently been successfully applied to inspection of wold overlays in several BWRs.

The following subsections summarize some of the more significant new developments.

3.3.1 Recent Developments at the EPRI NDE Center Workshop on Weld Overlay Inspections (RP1570-2 (25))

A number of 12 inch, Schedules 80 and 100 pipes containing IGSCC as well as machined notches were repaired with weld overlays and then used for UT procedure development. In addition to standard calibration notches, several types of deliberato defects were induced in the weld overlays, including lack of fusion, porosity, and copper /Inconel contamination-induced cracking. Automatic (Intraspect and UDRPS) as well as manual scanning techniques were included in the tests.

It is clear that significant enhancements in UT weld overlay inspection capabilities were achieved during the development testing. Among other things, the tests demonstrated that defects in the outer pipe wall (i.e., outer 1/4 T) as well as the overlay volume itself were reliably detectable. Longitudinal-wave UT demonstrated the ability to overcome much of the ultrasound attenuation and scattering characteristics seen in veld metal microstructures.

The tests showed that' deep cracks (in the outer 2./4 T) cculd be l manually or automatically detected and sized through overlays with excellent repeatability. Further, contamination-induced cracking and lack of fusion defects in the overlay itself produced indications with high signal-to-noise ratio and were detected. The test recults indicated that ASME Section XI Code-rejectable defects could routinely be detected in the 3-18 STRUCTUIULL l INTEGRITY ASSOCUGEINC

overlay itself. Conversely, the tests indicated that detection and length sizing of shallow cracks or the crack mouth-ID/ surface interface or deep flaws do not appear to be reliable at present.

The compressive strains induced by the overlay are such that even 0.015 inch width machined slots are closed after weld overlay repair application. Such powerful crack closure forces appear to change the UT response of defects in areas with high levels of compressive residual stress.

3.3.2 Argonne National Laboratory ( ANL) UT Inspection Workshops Two informal NDE workshops were conducted at ANL during May 1984 and January 1985, using weld overlay repaired pipe samples removed from the Hatch Unit 2 recirculation piping system (24 &

26). The samples included two 12 inch diameter pipe-to-elbow weldments and two 22 inch diameter pipe-to-end cap weldments.

All four of those weldments had been weld overlay repaired and then returned to service for approximately one fuel cycle before removal from the plant.

The samples were subjected to a wide variety of tests including RT, UT, PT, and destructive metallurgical examination. RT and UT proved difficult to apply, but the PT and metallurgical examinations indicated only a limited amount of cracking in two of the four weldrents (one of each type identified above). As a result of the limited cracking, the emphasis of the NDE workshops was on trying to understand the nature of overcalling cracks and the distortion of ultrasonic waves due to the presence of wold overlays.

Various inspection teams were involved in the workshops, and the tests included a wide variety of UT techniques. The results of the tests led to a number of observations / conclusions by the workshop participants, the most salient of which are summarized below.

3-19 STRUCTURAL INTEGRrrY ASSCLMINC

It was shown that cracks present before overlaying the pipes

. could be detected by UT after the overlay application. The tests confirmed the advantages, discussed above, of longitudinal over shear waves for inspection of pipes with overlays, and also yielded recommendations on transducer frequencies in order to improve signal to noise ration. Finally, the destructive examinations yicided the conclusions, noted in section 3.2.6 above, regarding crack tip blunting and crack arrest following weld overlay application.

All in all, the AtiL program is not in serious technical disagreement with the EPRI flDE Center tests summarized above, particularly in the case of cracks that have significant depth.

The latest longitudinal-wave techniques can penetrate the dendritic overlay microstructure into the outer pipe wall without unacceptable attenuation or scatter.

1 1

l i

I l

l 3-20 STRUCITIRAL I

. INTEGRITY ASSOCIATESINC

TAELE 3-1 FOUR-INCH PlPE WELD CVERLAY PARAbETERS PIFE RSP-14 AND RESIOUAL STRESS FCCXUPS PIPE RSP-14 Feur-Inc5 Pree Ps s-eters Beed Bend Overlay Overl ay Weld 12-inch Thickness Width Thickness Length Weld Pesttien ove-fav Threkness M M (In.)(e) (in.)(51 0.37t = 0.254 0.03 0.37 0.125 2.0 A 5G 8 5G 0.37t = 0.254 0.03 0.37 0.125 1.0 0.37t = 0.254 0.03 0.37 0.125 2.0 C 50 0.5t = 0.343 0.03 0.37 0.169 2.0 0 5G 0.5t = 0.343 0.03 0.18 0.169 2.0 E 2G 0.37t = 0.254 0.03 0.18 0.125 2.0 F 2G 0.37t = 0.254 0.03 0.18 0.125 1.0 G 2G H 2G 0.37 t = 0.254 0.03 0.18 0.125 2 .0 MCCXUPS Feua-Inch Pfee Pere-eters 12-inch Pipe Seed Eeed Overley Overley HAZ Pre- Weld Overley Thickness Wicth Thickness Length PTL (In.)(b)

Srect-en Egid creeks Pesi+ ten Thickress 1Ja 1 (ta.) fin.)(e)

H H1,H2 5G 0.37t=0.25 0.03 0.37 0.125 2.0 AWC-3 K K1 5G 0.37t=0.25 0.03 0.37 0.125 2.0 AWC-3 F F1,F2 5G 0.5 t =0.34 0.03 0.37 0.125 2.0 CE-8 A2 5G 0.37t=0.25 0.03 0.37 0.125 1.0 OE-8 A (a) After grindir; final overley surface smcoth ,

(b) Length not including 3 to 1 taper et each end

(

3-21 Assoc 1Aresuc i

.;, _ . _ _ ;, , , ._7_ , ,,

. f 2 '3 4 5 0 7' O 'O I 2 3 4_ ,0,~

iI- hfhfINjl!.h!l$iI i f!kbb!!l.k!!!!!Elkh.IIh' l

. A .4+ v. I' 4 T*~~

u .. . c, g.vcn, .

.. ? ; G ;

?. *>,.

ty.

- Q)%-

l

h. .

0-e ',c

v..: ,

c@ ;.), . ;.;

~

@ .4u. ),

=

ykd. . .

3

., Lj

@.)-

.W & .e'

%s j

,( #

' G, ,, h' 1

Nes. Hor. Vert.

! 1 0.7 0.85 2 2.1 3.0 l 3.6 4.1 3

l 4 4.8 5.2 5 8.3 8.4 l 6 9.0 7.3 1 7 3.8 3.4

! 8 4.2 4.0 9 5.9 6.1 a

I Figure 3 1. Cracking in Weld Metil of NMP 1 Recirculation j

Line, ferriteLevelsAreasFresentedinFigure.[12]

i l

3-22 INTEGRITY l ASSOCIATEINC

Y.%.n

.'C @, 2 :- :-

4.4. ] M . 7 $ ,S .. . .

l l --

Y, '

47 .

l

. ,~?

c.. .

s

.., .ch xW .. 4 i -

.. ' ::.p,.+,;v ..... vq s, s.,1.

, .. . . . . n. .

.i a.

% '%. ,5 >t . . .: ,

, .,4..g

- .y.

. . .r.,p I

y:..,..e.1. u .

. . c.

.+. ..

.'....;.. ..> c ..+ =

9 sy ,2@. .,. "q

... ,2 .

g

i

.,1

@ ./

rn 1

4 3 nes. ser. ve.:.

1 1.9 3.2 2 5.4 6.3

) 3 5.5 6.0 1 4 5.5 5.s j 5 5.0 5.5

! 6 7.3 6.9 i 7 6.5 7.0 1 8 9,2 8.S l 8.6 I 9 7.2

)

i i

I j Figure 3 2. Weld Metal Cracking .'n NMP.I. Ferrite 1

Levels Are as Presented in Figure. [12]

l l

) INTEGRITY 4

ASSOC 1/GEINC l

i 3-23

1 l

. . . 4 I

\

I l

l

\

. .. -,,.7..: n. .?.. ..q... :.Q::i..->:p. :. T_.y,,

N. ...s; . ;

. . , . . ., a. o. . ....s.... .:, .,.. <. .. ;.,. ,

. ......s,.....

. l

. +

, ... .. p ... .

..a

.~..

t.. ... r ..> n. d j. ..s.. j'

. x] . ., a . . . . .m. - ,t s .1 . ,

. . . .s,..,

. .. e s.. . ... . . . . . . ,.. . a,. .. .,.. . ,, ,. . . :

...... 4

.s. . ...

.. .,n. . , ... . .,, .. . . .. ... ... .... ..,._, u.... .. \. .. .

. . . \

.. ;. .. . . .u- .

. . . . ...:. . . c .. :. o :

. . . .e... . ...:. .~..; . . . . .. . .

n.,., .

.... :.........~...., ...

a ..,....

.s.

c. . a.

. .v. i ...... ..

. ' . +;. .'.;~.100 p m....

.,....,v.

., ;: h . ; y.

s. .

,.,.), .. _+. . . ..

.m ..

Figure 3-3. Subsurface Crack Present in Weld Metal in Quad Cities Core Spray 1.ine [13]

i 3-24 MEGRITY ASSOCIATESINC

' ,< ; ,\Il1,1;1:lI:i' l ,1l l s

s

?' .

l e

9. k3 . y-h' 7 :

i n

a

?'. Q.{h .

. {, t

^ S

' c_ ,

f.

1

? ' :. b k

p(

- 6 1

N;' -

/ . .

g*

3 h ., j.

,s .

f o

l O ,* ,:r1 l A

/ , s -

E

.l. . .

' i .

n y

j, ,.\. s4 ,<

e

. m vi . .

._ 3 i y ,

c e

.' s n

' 'l_ .s % % S

~ ' a

_se, .

r L

. r O a W w

1-o l i

c

. ;- n le i t n a p% s m, . . n o.

o

. l o -

n l]

- g ,

e lS c oI

> v HL r

~

- n

> o f2 ys -

o r

o6 6

v y9

- t g ns

~.

s ot

, l a m oe

- hll p

r.i.

- r ,

t .

e. o)

L)

MX

. i c 6

'e s

g2

^

, 2 i n(

. ~

kl

'os ce ae

.. s'Uh ,

s rt

.he:.p CS

- r u

S. .

t u .

w 4

- ' ^ o -

_ ,' . . . . a 3

, ~.

i v

}& . ,.A

> r=.

?

u r

e r

%i2 ~ , . ,. t s u

,.'.- :. . 1 s. : e r i F

g

@hR wsuv' n

E !

, ; 1:!!:4l1 :$\ll)! ;,.!Ii3ii!j

t l

p* 8.ar t

.' a o'I.**e, f .~ ,,, ? n -

l f *4*$ ,.-l .g. . ', . .*. 4A f.e ,w .s;. % A

.' . Q. -... p

'f = 's.}

-~

w- ) 4. b ? * %*

. ~

ei? '.,y:

'- c-

.:, .3. , ' . + *3f, ,((*g ;';- 4 ~' v~':..g.. s . ' ..-

l l k..,9 -

c. *

- Wi' l .. ,

.a

. , . . . 4& Q y .- 9 -p , 1

' e,.s. .,

'**r,- . s,, .. , y

.#c ,. ,

e' 4 ~,. #

g ,M

. . Q, % .,

e f . '$ . , ' ' ..

.,. , \ A - s. - * .,

g t, t ., er , ,,g gg 3 ,,

. *- ,q .

y,. -

w.. _ ...

.w,. . u , ' . .y '.K p . ';,,'

., 3. -n . . j w%TN

b./- : .2,.-

' l

. s .. NJ . .S 5.- ~. L , 'SQ.

C '? , .un * **

, .'. %~

i. ' . .-M. M: M 7ts? (Nvim0NutNT $5c's ess' ) 8 ocr s OtS30Lvt: Omv0tN et 0%i213 W ATim Figure 3-5. Crac'<ing Morphology of Eol: '.caded i JL Specimen EB1 of Type 316:iG Stainless Steel, Heat TV0076 (26X)

[15]

u j m .i Wr&. ,.

l

. .. - 4.c.;25 :d WA e..

. . . .. .- ? t-

,. 9 .

-)

~ . , . - .

O; ;- ,

3 ,. .+. <

,s T

,1;O

f. . .e*

,P.,......,L, .

\

~

ef. qs *& f,i '. ,*': , +^ -.) l

.,n,,-

~ ,

R -

~ -

- gg ,-

.~e. _

.a~. ,

t.'

.?

(

} a

. l

]

" 4. L. *

=

3

I o.

, 1 i 6 .

r . .

1tstENvim0NutNT I40'A 138' ). 8 pom Dt550Lv t 3 CITGE N 0ti:NIZID nAfte Figure 3-6. Cracking Morphology of Bolt-Loaded WOL Specimen ES2 of Type 316iG Stainless Steel, Heat TV0076 (26X)

[15] .

STRUCTURAL t

3-26 INTEGRITY mg l

i

- ..- - .-,w._,--,-._,

t I

l r

,I ( e,

t .

pp.

\, . .. , .

j R~..

k'Q ' '!r

, e . .

.~ ...

. ' , , i' .

/s

(

-7__ -

.. .V' i

> 1

.I",'T*'s g'. ***

,h ,".** y ,. s',' 3 ,

g{p.,

y

,' gt-

'. ,4 1

1

.,...- , ,, T ',. '

)

' ' y. .~.e , ' '/ . '

I , . k,,

g .s. g

r-).v w,

y ,.

. .1 :,..

.N. . . , . m M. .', ;. .v ' -

7t si (NviRONutNT. $50'8 Ct8'C1. 8 oce. DissoLvt Cxv0t% (4a1713 WAfta Figure 3-7. Cracking Morphology of Bolt-Loaded WOL Specimen EJ1 of Type 304 Stainless Steel (26X), Heat 46436 [15]

3-27 INTEGRITY g

(*.T. ,.: * *W

%.

r.r ' ' fs $.

t , , .. i ..

> K'4.* ** t- *

. s- y:p

= -

. * ,* \ ,

.. .-. ,;. * .. ,* % '*. . . g ., ..

. 7. ,g",. ( . , .,.- , .; ., lt t

I y ,e,

,a.

3

~,. . , ,, ,

( ., .

j . ,.

i

\ 3. ,i,.

= . g ...

. -. p 7 '.~. .

p . .o ., . , *g - .

9 '" .

1 .#

/ ' . y.. .,.'

g (.

l j'l e , ,, c - ,

'm ;,

. . .s .. .. .

a'

l \. .. ,,s ;A e %.,*' . ,,,.' . v N

d. -t,

.t.

.. / , .."

9 s a

%q...../ ...,; . .

. . ' , .a ,4 ,-

, , =...

. .r. .. . *,

2.

s t

+' .y .; s.

" ; w g . &%.'.' )

. ; *.t. : \

e N....,.,

'=r' a K;,,.y: ) i

.. ./ ]

.n .. $. ' i ' >'. .QQ' -}. t-

. ,) .Y.,

5*x.Q.(. . . g

\# g

' aj ~A %x@., . . '?, ~n%.. ., , ,y Lr

,W, t

. %. *~. .

7 s,

-. M.' 4.

. , ' u.., > ;'. . .9 4 ,.% s. s [:.,' >, /g?".-* ,

s e?

"%. . I 1

. ~

.\,,'* h .

V hU ),

. , f,.', .

. . . .r.% ) . .. t i w .-

~< v %. -,f. .,, N .: . C.y .r-

--: :. . .c

. ~~ws.4s

. y r, .*

.5%.s .

\

.[. 1 'I.'. .

1 i

l I

I l

1

'f.

,.. .%, ~

. ~ .: ..-g -s

, 1', "i...,):. w - .$*W.*i,' *. . ' .g [ *j. '.Q. . .~, *. O

'f.. _[ .',. -' ,.v Sig ' y. m. p.- .'- .--.,'

c. , g.-

. ; a. . .. - - -( f* . .. .

j.. ~ . - - :. p..- .

a. ,t

- -/ .* .

_* . . ' *.- - .. '-=,= ,", - ;,...

L,,

7 s- e . ..:^*M*,'.. : 8 r . >

. ...g\ .

. - , .,.y9- . t.

.)$. .: - f g. , 3'.p :. ~

"'-; q *e., j.-

? - e

. . . .e %r g ,. - - -1r- . .

je. . . - . . .6 ,

..2.r.. .,v % x .. .

c. . , . ; . '. ', ,s ;.: . .. g i*- ;.

s } : y - .i h .- s 8L .

<*p....... .

t

.s.c

' 3.. .

. .,t.:

.-.y.. . ,.: . : c. ..

f. '

,e.

. r .. .

~ - .

....t'.

.a.

g.'-... . .

,% K....:.*<.., : ' . . : ..

. .. .. ...r _* sr *q ,

l., . *..t,. ~i K..,.,'.*..-.,***;*-4. ' ...;1 _

. ?. ,,

.3

.4 ., ,

- . ...,.g .W

4. ..

g 3

.. ;.s v. _ ; ;

4 ...* c .L.s,f . ,. =? .* . . .m ? ;. .

a. . , - }.. .s .

<...,,..p,.gd5 s. . . u:, . . .*-,p,,... ,sex.. y.- ...; gr.-s. .,=. * . .. . % . , .

. - . . .. . = .;. ....

a - '

.g .- ,o r , , - . .

p,r. , . , g . . ..,,;,.., 4.

J .p*. *

,a.,._*Y ;r .g .-

... . _ . .. . < . ~ . , .. . . .... ,.

,.,4 4- s .

F i g .r.. 2 '. . '.41d O'eer l ay Ar rw. o f 1 G;'.'. Se..c im F. J 14 [19] .

STRUCTURAL INTEGRITY 3-26 mm

l

.n -

f4 hO s, * - r 0 A

- e

.x -

e i

a - ,o f *"

t

a 3*

2 n -

O O ice k O ** c" T O WE'.D I I I I C o 04 0 c6 0 08 0 10 o c.0 2 CAABON'Y .

Figure 3-9. The Influence of Nt a-/ on the Intergranular Corrosion Behavior of Aged Samples of Wrought and Weld-De;0 sited Type 308 Stainless Steel. Open Symbols Indicate IG5CC per ASTM A262 Practice E Testing; Closed Symbols Indicate ho IGSCC [213 l

t l

1 LTEGRITY 3-29 MMINC l

. I l

1.3 0

1.2 -

c - As-De;;osited 1.1 - Type 308 Weld 1.0- o - Solution Heat Treated Wrought 0.9- Heats of Type 305 Composition y 0.8 - l OD N g 0.7 -

On g 5 0.6 - ;

kE * '

N 0.5- ,

0.4- T 0.3 -

W ~* '

l a '

o ;

0.2 -

l o o O.1 - !

l i

0.0 , i . . . i,e i e i i i i . . ,

0 4 8 12 16 20 24 25 32 FERR!TE (VOLWE %)

Figure 3-10 Number of Intercepts of a Random Test Line with Austenite- l Ferrite Boundaries per Unit length of Test Line, N L, Versus l Volume % Ferrite for Type 308 Compositions j 1

l

' YMM 3-30 ASSOCIATESINC l l

. i Sealed 5.5. Lines For Cold Baffle Sheet to / City Water To Separate Halves of Pipe Against M gCl2 / Condence !!gC.12 Fumes Fumes Stainless Steel (5.5)

Condenser Plate (Leave l Hole For Pressure Relief) f Being ested %

s- M

., Molten Mc.Cl2 Heaters I!

)n Around

Outside l 'i I -

-Pipe Butt Weld il C

% l d [O si o

5.5. Fillet-Welded O g' . , -[ , - = ,

f, Ecttom Plate to Support i,* z si'.'. .:*j Mg Cl2 Molten Salt

'V, j

i .8 i!

Hot Plate At 150 0C l

i l

Figure 3-11. M gCl2 Test Set-Up Using 2S" Pipe As Vessel. One ,

Side of Baffle (Half of Pipe) Tested Before Weld l Overlay, Other Side After Weld Overlay l l

l l

3-3., INTEGRITY

, egg

. a Cirt. Asial Ant (het .51

[

notch Cirt. Notch L .Ilt deep a 21

.6L tips 0.25* .

long l(enter on Aaial Notch + 0.1- from Side @ "

weld fusion line \_

- w

_ eld p d '2 1 9 j

Circ. Notch Circ.

\

8////l

j. N .J51 g_

l Pipe Butt Weld Notch .151

.39

.15t -- I

\.

g g

\

g

\

Asial Notch

/

/ 'N - 30o "., s /

O s / \"t

.'st deep W -*

N # \. ' / ..' t 2t leg sea l- rrrrrrarnuna

-scal 'N' } - - - -- . nannww.

l lwnwwmnima unrr rngrgwmk Baffle o separate top &

naffle

\ N. '. Sheet . tettom flalves of pipe from j

w 1 ,

/ \ MgCl2 fumes (Case stainless I

W 1

\ ; ,-

[! N ,,

'g' /

1 Corners Can steel sheet)

M \ \ // \g J' be Rounded 7

\/ / /

\

'/ ,.- 'k s j \

wy-s,-.,a t-Nq%9,p .,

s. ,

i Side 6)

Side view (s) l

[nd View of 28* of Pipe !

Dia. Pipe (5(hemat it. )

1- Figure 3-12. Cl><wferential and Antal Notch Stres and locations (Bottom llalf is Minor Image of Top Stalf of Drawing) - Showing Stainless Steel Saf fle to Permit 5eparate Testing With N gCl2 Of IOP,and Bottom Italves of Pipe (Seal Against M C12 g Fumes) 1

i II g MNC 5 1 s

%- 9- O. '

^ 1

_, ' l.f. .sW.ip * ;;

vl A >t.~- ..

t, 'f .'p s - )'y * ,f f ~

1

.- flo f4,(.17 Crack ing 4:-fjf .=

M_i 5 %-A 'j -

l

'l;l,$OY$,,5 .

~! .

v

= m .

v ., . .

I

" .i t / ..-

y l

z.

T . . w. . ,

e l*.

. h. \ .

.J . q ~ ,, \ .

t

. 4'. ,

w - . ,

A ,

e

t' .

l-

. 4 .1 '

8. I .

s A. . . _ .

flotch Tested Befora Weld Overlay h) flotch Testeel Af ter Welci Overlay a) f igure 3-13. Metallographic Sect ions (100X) of t4oilerate Dept h, Circumf erent tal riotch rips from GPC/SI/WSI 28-inch Df flotched Pipe Test [22]

C

. I l

WELD OVERLAY TESTS OUTSIDE DIAMETER

==:: l o

~~

e ee u_ _ .

o i c.7 - -

b e # I

$ 84 8 g J

.. e*9e 9 Y a d

e .

't *

E E4- -

C

, e [ Measured DataI

From Different

,u- -

( Axial Positions)-

e .es , u. _

%e o.1 - -

Jo 40 40 40 A 'do .N do o 1'o S lio A s yo' afo m STRESS (Ksi) l INSIDE DIAMETER 20" OVERLAY ll ATCil-1 (LONG) WELD PREP l

l l

CALCULATED AXIAL RESIDUAL STRESS I TLROUGH-W ALL OF 12" SCH.100 PIPE Figure 3-14. Through-Wall Residual Stresses [23]

STRUCTURAL 3-34 IN'1TGRITY mE

s- AXI AL STRESS Q-h -$ -

m 3

m *l0 -

h als -

i

.g .

,3 : E.D WLUY :

-w. o -e.o -i.o -i.o -i.o 6.0 i.o i.a i.s s.0 l Ar/AL POS. IN. t l

l 8- ICCP STRESS Q-g -s -

5 m -w-m W

u Is -

n

.x .

s- : YED WLUY :

J0.0 -e.0 -4.0 'k.0 *0

. 6.0 $.0 5.0 4.0 5.0 AllAL POS. IN.

Figure 3-16. 10 Stress for 24 Inch Overlay [23]

STRUCTURAL

' INTEGRITY 3-36 ASSOCIATESINC

STRESS TliROUCll TillCKNESS AFTER FIRST LAYER STRESS TilROUCil TillCKi ESS ATTER SECOtn I_ AvfR av At statss - -- enoe statss Ausa s w ss -- - t w s W ss

-. 92 3F .

03# *

(HIf R

p g A u s At. D85IANCE AI Aul AL l'IsTANC( ,

,g ,. $33gggg{

)300 BDO(s f (( P,gy Of PIP (

8

/

l .

gy . ,/ 88- *

,.~

g ,. 8 n y .~,

[, t) z z .

,-. . - : a us e s .

g siss- m ,

w .a -

e o

e ;,

Z

0 6.e

z = o.5 "

N j , 'r ,

. l it24- ; tl 24 l 5

arean: ewsm SandeCf I $ag4pA([

. I fW I* t PC 3 Of PIST ons . . . . . . . . . . .

~ n eo . . .-i . . . . . . .

- e*t - S3 30 n O n 20 30 40 50 +0 30 - ee ~30 n o n 20 3.B 40 50 so stitEss (xsi) stor.SS (usi) ii figure 3-17. Calculated Through Wall Stresses af ter the First and Second Weld Overlay Laye: s y for a 24 Inch Pipe with 1.4tl Inch Wall. (0verlay contains five weld layers for O a total tiiickness of 0.35 inch) [23]

9 STRESS THROUGH THICKNESS ArtER FIFTH LMER AstAt 51Rt15 -

Hoop STRESS I2 Jf .

At Ast At Ol51AW '

E8 0 SCO IW $ .

Cf PIPt it - ,.~

- (*

G .-

2

- s

, nn- :

o :

5 :

x = 0. 5 '

un- :

I e

1

}

ma

star,et

a or P,Pt

-so-k 'o .h -io 4 'c o e 2'o .io e'o io so STRESS (KSI)

Figure 3-18. Calculated Through Wall Stresses after the Fifth and Final Weld Overlay layer for a 24 inch Pipe with 1.48 inch Wall. (Overlay contains five weld layers for a totalthicknessof0.35 inch.)(23]

i I

3-38 INTEGRITY gg 1 - - - - - - - - - - - - -

4.0 WELD METAL FRACTURE TOUGHNESS The flaw evaluations and weld overlay repairs at FitzPatrick were conducted in accordance with ASME, Section XI rules for evaluation of flaws in austenitic piping, IWB-3640 (Winter, 1983 Addendum). These rules provide allowable flaw depths for axial and circumferential flaws based on the net section collapse criterion (NSCC), which assumes that the material has sufficient toughness that the only effect of the cracking is to reduce the load carrying cross-sectional area of the pipe. This method is well supported by test data and analysis for materials exhibiting toughness properties typical of the wrought stainless steels used in nuclear reactor piping systems. Recent fracture toughness data for stainless steel weld scial, however, have suggested that some flux-shielded weldments (SAW/SMAW) may have significantly lower toughness than wrought stainless steel. This has led to revision of Section XI, IWB-3640 (Winter, 1985 Addendum), to provide more restrictive allowable flaw size limits for flux-shielded weldments, based on elastic-plastic tearing instability analysis of the lower toughness materials.

This issue has relatively little impact on the current consideration of extended service of the FitzPatrick weld overlay repairs, since they were applied using a gas-shielded (GTAW) welding process, which has demonstrated sufficient toughness in all tests to justify the use of net section collapse methodology.

The 1985 Code revisions discussed above explicitly state that the earlier net section collapse based criteria are still applicable to GT5W weldments. As detailed in Section 2.0, the weld overlay repairs at FitzPatrick were designed with a thickness which requires no credit for the original pipe wall in maintaining design basis safety margins. Thus, the design basis of the overlays is maintained regardless of potential low toughness of any original, flux-shielded weld joints. Recent proof testing of weld overlay repaired pipe, described below, further confirms this point.

4-1 S'fRUCTURJE INTEGRTFY AssoCIATESINC

4.1 Battelle/NRC Degraded Pipe Tests 4.1.1 Test Objectives An experimental program to confirm the effectiveness of the weld overlay repair method for repairing cracked pipe is currently being conducted by Battelle Columbus Laboratories on behalf of the U.S. Nuclear Regulatory Commission [27, 28]. The purpose of the program is to evaluate the accuracy of the assumed safety margins of the Section XI net section collapse methodology which I has been used as the basis for weld overlay design in the U.S.

and elsewhere. In this program, weld overlays were applied to pipes containing deep flaws, the pipes were leaded to failure, ,

and the actual failure stresses were compared to the Section XI predicted values. An assessmerit of the actual margins of safety I of the Code approach compared to the predicted margins can thus I 1

be obtained from the test results. '

4.1.1.2 Experimental Approach Three experiments were performed. The test pipe specimens were 6-inch Schedule 120 Type 304 stainless steel pipe. Each pipe had a flaw introduced which was through-wall and which extended circumf erentially approximately 50% (Figure 4-1). Flaws 50% of wall depth, extending approximately 17% of circumference were introduced by electric discharge machining. These flawed specimens were cycled in three-point bending to grow fatigue cracks through-wall, extending 50% of circumference. The flawed pipes were then weld overlay-repaired (weld overlays were 0.31) inches thick on the average) using techniques typical of field practice. Each pipe was then pressurized at a temperature of 550*F to different levels of internal pressure. The internal pressure was kept constant, and each sample was loaded in bending under displacement control to failure (Figure 4-2).

4-2 STRUCTURAL INTEGRITY ASSOCIATESINC

4.1.1.3 Test Results Results presented in References [27) and [28] suggest that the experimental failure data are in good agreement with the theoretical NSCC failure predictions which serve as the basis for weld overlay design (see Figure 4-3). Differences between the Battelle test data and the FitzPatrick weld overlays are summarized in Table 4-1.

4.2 Application of Test Data to FitzPatrick Weld Overlays The FitzPatrick weld overlays have been plotted directly on a load margin diagram (Figure 4-4) in which equivalent theoretical failure predictions and design curves have been developed for the 12 inch riser overlays, using both the source equations and IWB-3641 tables, with safety factor. of 3 and 2.773, respectively, as well as the no safety fact r cases.

The points shown on Figure 4-4 represent the as-built weld overlays for each of the 12 inch risers, neglecting the thickness of the first weld layer. The data demonstrate a factor of safety to failure in excess of 2.773 by the IWB-3641 tables and 3.0 by !

use of the source equations. ;

l 4.3 Summary The weld overlays applied to six recirculation system welds at FitzPatrick were re-evaluated, considering the potential impact of recent concerns regarding weld metal toughness on ASME Section X1, IWB-3641 flaw evaluations. The factors of safety to failure for the FitzPatrick weld overlays were evaluated by comparison with Code Table and source equation values. Since the weld overlay metal at FitzPatrick was applied using the gas tungsten arc welding process (GTAW), the low weld metal toughness data available for flux shielded processes (SAW, SMAW) does not apply to the FitzPatrick situation. The not section collapse approach 4-3 STRUC11TilAL INTEGRITY ASSOCIATESINC

applied in weld overlay design for FitzPatrick is sufficient to guarantee adequate margin to failure.

The above conclusion is supported by recent degraded pipe failure data developed by Battelle on behalf of,the Nuclear Regulatory commission.

i

\

i i

l I

l 4

4-4 @g INTEGRITY ASSOCUMEINC

l TABLE 4-1 I Summary of Differences Between Battelle/NRC Weld overlay Test Pipt.s and FitzPatrick Weld Overlays Battelle/NRC FitzPatrick Tests Risers (As-Built)

Pipe Diameter, in. 6.625 12.75 Pipe Thickness, in. (avg.) 0.56 0.717 Overlay Thickness, in. 0.314 .385 - .672(1,2)

Crack Length / Circumference 0.5 .126 - 1.0(3)

Crack Depth / Thickness 0.65 53 - 66%

Design Allowable Load .239 I4) 0.120 - 0.233(6)

Ratio (P,+ Pb )/8f

1. Average As-Built Thickness at Crack Location

2. Beyond 1st Weld Overlay Layer

3. Assumed for Design. Actual // Circumference Ranges .126 to 1.0.

4. Average Design Load for 4 Tests by Source Equations l

S. Average Design Load for 4 Tests by IWB-3641 Tables

6. Does Not Include Thermal Expansion Stress l

l l

l 4-5 STRUCTUIEL INTEGRITY ASSOCIATESINC

~ flb m'm)

A Internal 6$ inch 0.0 Surface (168 mm)

Crock

)

/ .

/

Weld Overley Pipe Thickness Repcir M ~ O.562 inch (14.3 mm)

Thickness of Weld Overley ~ 0.314 inch (8.0 mm) x.

- Internal Surface Crack s : Chp gage locotion I

g i * = d-c EP locations

\ /

\

N /

s /

% /

SECTION A- A Figure 4 1. Illustration of Cracked Pipe and Weld Overlay Configuration Used in Battelle/USNRC Experirnents

[28) 4-6 STRUCTURAL g

ASSOCIATESINC camaamwan .

~ 37 inches : = 4 8 inches : 37 inches ~

(939 mm) (!,220 mm) (939 mm)

Wald Overley3 Instrumentation Line Return Int ernal Pressure Pipe for To + Pressure Lines Surf ace Crcck Line Moment Arme accumAto em N~ __

V4 s s el Co p s (t Q_g,,,,i End f { _}

, j 1, , , _i _,

N N End

./ Suppect iI II Olsptocement Centrolled e Actuators \

Strengback Figure 4-2. Schematic illustration of Test Setup Used in Battelle/USNRCWeldOverlayExperiments(28]

STRUCTURAL 4-7 INTEGRITY AssoCIATEINC

.' l i

I l

0.7 1

Failure Predictions (S.F.=1) l 0.5 - ,

xy NSC Source Equations l IWB-3641 Tables l 0 I

$ 0.5 -

t 3 x- i o l g 0.4 -

x2 l

\ '

n O *3b g 0.3 -

m Design Limits 5 0.2- (5.F.=2.773)

NSCC Source Equations IWB-3641 Tables 0.1 - l l

0 -

0 0.2 0.4 0.5 WEWERANE STRESS /T1.0W STRESS THEORY x BATTn1E DATA 1

l Figure 4-3. Comparison of Recent Battelle/USNRC Degraded Piping Program Weld Overlay Tests With Overlay Design Basis '

Calculations 1 i

4-s INTEGRrrY Assoc 1ATESINC

'~

Based upon 12" weld overlay repaired pipe with a/t = 55%

0.8 NSCC (Safety Factor = 1.0) 0.7 -

y IWB-3641 (Safety Factor g 0.5 - = 1.0) g 0.5 -

d N

g 0.4-E H NSC (Safety Factor = 3.0) 0.3-Z Design Basis

~ IWB-3641 (Safety Factor = 2.773)

@ 0.2- s

$ f 12-12 12-69 0.1 -

12 ,12-70

o 23 0 . . . . . . . . . . . . . . . . .

0 0.02 0.04 0.06 0.08 0.1 0.12 0.14 0.16 0.18 WCW9RANE STRESS / FLOW STRESS Figure 4-4. Comparison of Fitzpatrick Design and As-Built Weld Overlay Data to ASME Design Limits and Recent Pipe Failure Data STRUCTURAL 4-9 Assoc 1ATESINC I

5.0 IGSCC MITIGATION ACTIVITIES AT FITZPATRICK In addition to performing repairs to locations containing significant flaws in the recirculation and core spray systems, NYPA has performed other activities designed to minimize the potential for IGSCC in the stainless steel portions of several systems. These activities include residual stress improvement of susceptible welds using the induction heating stress improvement (IHSI) and resistance heating stress improvement (RHSI) processes. Piping modifications were performed on some susceptible subsystems to eliminate susceptible welds or to replace the susceptible material with carbon steel material, which is inherently resistant to IGSCC.

l In order to further mitigate the potential for IGSCC, NYPA is installing a hydrogen addition system, to be operational in 1988.

This system will shift the coolant chemistry to a regime where 1 IGSCC is inhibited.

In this section a brief discussion of the IGSCC mitigation l activities at FitzPatrick is presented, and the present status of l the IGSCC susceptible piping is summarized.

5.1 Induction Heating Stress Improvement (IHSI) !

1 Induction heating stress improvement (IHSI) has been shorn to be an ef fective method for minimizing the potential for initiation ;

of new IGSCC flaws and growth of existing shallow flaws it. BWR stainless steel systems. The process modifies the residual stress distribution in the vicinity of treated welds, such that the residual stresses are strongly compressive in the innermost portion of the treated pipe wall. NUREG-0313 Revision 2 (Draft) endorses IHSI as an acceptable method for reducing susceptibility to IGSCC. Welds which have ben successfully treated with this process may require less frequent inspection than untreated welds. NYPA has performed IHSI treatments on 89 welds (both 5-1 STRUCTURAL

. INTEGRITY ASSOCIATESINC

l flawed and unflawed) in the recirculation and related systems at FitzPatrick since 1984 (NYPA Modifications F1-83-059 and F1-84-067). These welds are considered to be in NUREG-0313 Category c for the purposes of defining inspection intervals.

5.2 Resistance Heating Stress Improvement (RHSI)

Although IHSI was applied to the majority of the IGSCC susceptible welds on the recirculation system, it was not possible to employ this process on two 28 inch pipe welds due to the geometric constraints imposed by piping supports in the vicinity of these welds. In order to provide some form of stress mitigation at these locations, NYPA developed a resistance heating stress improvement process concept, and demonstrated the effectiveness of this process as discussed below.

To demonstrate the effectiveness of the proposed RHSI process, NYPA performed a test RHSI treatment on a 28 inch diameter welded pipe using the process parameters and resistance heating coils which were to be used on the two actual plant welds. Following the treatment, the specimen was sent to Southwest Research Institute (SWRI) for destructive measurement of the resulting residual stresses. These measurements confirmed that the residual stress distributions which resulted from the RHSI treatment were highly compressive on the inside surface of the specimen, and that the residual stresses remained compressive well into the pipe wall. The observed residual stress distributions compare well with the distributions observed to result from the IHSI process (29) for the same pipe size.

Elastic-plastic finite element analyses of the test specimen were performed, using the parameters used in the pipe test. The results of the analytical effort agreed well with the residual stress measurement results, thus validating the analytical model.

Further analyses demonstrated that the RHSI process was able to produce compressive axial and circumferential residual stress 5-2 gg

) DiTEGRITY ASSOCIATESINC

distributions through a portion of the inner pipe wall. In addition, it was shown that the RHSI process is tolerant to deviations from the optimal temperature distribution, as long as the deviations are local.

The RHSI process as qualified in the test program was successfully applied to two 28 inch welds in the FitzPatrick recirculation system in April, 1987 (NYPA Modification F1-87-034). These welds were numbers28-108 and 28-50. The test program and supporting analyses demonstrate that the residual stress distributions produced by the process in these welds is expected to compressive at the inside surface and through a portion of the pipe wall of the treated pipes. The predicted residual stress distributions are comparable to those which would be expected from IHSI. Because of the demonstrated ;

effectiveness of RHSI in producing favorable residual stress distributions, these welds may be considered to be fully mitigated with respect to IGSCC, and are therefore considered to be Category C welds as defined in Reference [2]. l I

5.3 Piping Modifications i

Two major piping modifications were completed during the Spring 1987 refueling outage. These modifications were to remove

)

portions of lines containing IGSCC susceptible welds, and in some cases to replace these lines with material which is not j susceptible to IGSCC. l l

The reactor recirculation system bypass lines (4 inch diameter) I were removed and the stubs were capped (NYPA Modification F1-78-034). This activity eliminated 20 IGSCC susceptible welds from the system. The cap material is type 304L stainless steel.

The original Type 304 weld-o-lets, which were left in place, were internally clad with Type 308L weld metal with ferrite content greater than 8 FN. The weld-o-let to 28 inch pipe welds were also internally clad with two layers of 308L weld metal. Both 5-3 STRUCTURA1.

INTEGRITY ASSOCIAEINC

the Type 304L and the high ferrite Type 308L clad are considered to be IGSCC resistant materials (2]. A total of 8 welds remain in the bypass lines. These welds are considered to be in NUREG-0313 Category A.

The residual heat removal suction piping and a portion of the reactor water clean up suction piping were replaced (NYPA Modification F1-84-053). The stainless steel piping was replaced with high toughness carbon steel material. The remaining ends of the stainless steel material were clad with 308L weld metal with ferrite content greater than 8 FN prior to welding to the carbon steel spool piece. This modification eliminated 7 Category D welds from the system. The welds in the replacement piping are classified as Category A, since the replacement material is not susceptible to IGSCC.

5.4 RHR Dissimilar Metal Welds Three dissimilar metal welds are present on each RHR loop. These welds connect the stainless steel components to the carbon steel ;

components by way of Inconel 82/182 butter on the carbon steel components. The Inconel material is potentially susceptible to !

1 IGSCC. Because of the geometry of the weld joints, conventional '

inspection of these joints is not feasible, and mitigation of these locations by a stress improvement process has not Meen performed. NYPA has begun development of special ultrasonic inspection techniques for use on these welds during the 1988 outage. Contingency weld overlay repair designs have also been prepared for use during the 1988 outage in the event that inspection is not possible or flaws in the Inconel butter are detected. In the interim, no significant threat to the integrity of the system is posed by these wolds, since the welds are in 34 inch piping, and long circumferential IGSCC flaws have not been observed in piping of this size.

5-4 gg INTEGRITY ASSOCIATESINC

2.5 Jet Purp Instrumentation Nozzles The Authority is considering the feasibility of injecting recirculation system fluid protected by hydrogen water chemistry into the drain assembly of the jet pump instrument assembly to protect the welds in the assembly from IGSCC. (The JPI assembly is presently exposed to stagnant water conditions) . This fluid injection would potentially protect ten welds from IGSCC (4 Assembly welCs, plus 1 safe end-to-nozzle weld for each loop).

The conceptual engineering for this modification has been completed.

5.6 Hydrogen Water Chemistry NYPA has conducted tests to assess the potential benefits which would result from use of a hydrogen water chemistry system at FitzPatrick. NYPA intends (as of the date of this report) to implement such a system in 1988.

Addition of hydrogen to the reactor coolant will reduce the amount of free oxygen in the coolant to levels where the potential for initiation of new IGSCC flaws and the propagation of existing flaws is strongly inhibited. Consequently, the joint use of a hydrogen water chemistry system with the stress remedies (IHSI and RHSI) which have been applied to the welds in the recirculation system will effectively prevent initiation and propagation of IGSCC in this system, thus supporting long term operation of the system with the existing piping materials, including the Inconel 182 butter on the safe end-to-nozzle welds.

In addition, the GE crack arrest verification (CAV) system will be used to monitor crack growth rates on'line, to verify the beneficial effects of HWC.

JAF is in the process of committing to the EPRI BWR Chemistry guioelines. These guidelines, together with the effects of the 5-5 NO INTEGRITY ASSOCIATESINC ytrswe~ -

l hydrogen addition, will produce water chemistry which strongly inhibits IGscc.

New chemisiry sampling panels and on-line instrumentation, coupled with in-line data acquisition systems, are being installed. These systems will lead to more accurate and more frequent chemistry monitoring, will identify transient i

conditions, and will enable JAF to minimize the time that the plant coolant chemistry is outside of the EPRI guidelines.

t i

i 5-6 AssIDCIATd

~.

6.0

SUMMARY

AllD CollCLUSIO11S l liew York Power Authority has detected intergranular stress l corrosion cracking at locations in the stainless steel portions of the recirculation system at J. A. FitzPatrick since 1984.

During the 1987 refueling outage, flaws were identified for the first time in the core spray B loop. During the period since IGSCC was first identified at FitzPatrick in the spring of 1984, liYPA has conducted several activities designed to repair the existing flaws and to minimize the occurrence of new flaws in IGSCC susceptible systems in the plant.

Weld overlay repairs were applied to six recirculation system locations containing flaws in 1984-85. These rephirs were designed in accordance with the requirements of Generic Letter 84-11. The six weld overlay repairs were re-evaluated in 1986, using the repair as-built dimensions and the design criteria of 11UREG-0313 Revision 2 (draft). Those criteria remain unchanged in the recent, issued version of the liUREG [2]. The as-built repairs exceeded the required thickness to qualify as standard weld overlay repairs as defined in that document in all cases.

In 1987, the outside surfaces of these repairs were smoothed by grinding to enhance the ultrasonic inspectability of the repairs.

Following grinding, the dimensions of the repairs still exceeded the liUREG requirements, thus qualifying the repairs for long term operation in accordance with the liUREG requirements.

During the 1987 refueling outage, three locations which contained IGSCC indications were identified in the core spray B loop.

These locations were repaired with weld overlays designed in accordance with the liUREG. Two of the three repairs were designed as standard weld overlay repairs, while the third (at a <

location which contained only axially-oriented flaws) wcs designed as a "designed weld overlay". lione of these three repairs was surface ground to improve the finish for inspect Sility, since these repairs are tentatively being 6-1 STRUCTURAL INTEGRITY ASSOCIATESINC

considered as temporary. NYPA is considering replacement of the affected piping in the core spray system during the next refueling outage.

As a result of the inspections conducted in 1987, small flaws were identified' in seven locations in the recirculation system, in addition to those locations with weld overlays in place. All of these locations had previously (1984, 1985) been identified as containing flaws, and no appreciable growth of these :' laws was observed. All of the flaw locations had been treated with the IHSI process, which effectively arrests small IGSCC flaws.

A total of 89 welds in the recirculation system have been treated with the IHSI process to mitigate the potential for IGSCC mitigation at these locations. In addition, two welds in the 28" portion of the recirculation system were treated with the RHSI process developed by NYPA. All treated welds are considered to be fully mitigated with respect to IGSCC, as defined in NUREG-0313.

l Twenty-seven IGSCC-suscGpi.ible welds in the recirculation system bypass, RHR suction and Reactor Water Cleanup system were removed. The piping in the RHR and RWCU lines was replaced with high toughness carbon steel material. This material is considered to be immune to IGSCC. The reci? culation bypass lines )

were not replaced, but were cut and capped.

Six welds in the RHR system are welds connecting carbon steel components to stainless steel components by buttering the carbon steel with Inconel 182 and completing an Inconel 82/182 butt weld. These have not been inspected to date due to the constraints of geometry. NYPA is attempting to develop UT procedures to allow inspection of these locations. The new inspection techniques are expected to be ready in time for the 1988 outage. As a contingency measure, weld overlay designs have been prepared for these welds.

6-2 gg INTEGRTTY ASSOCIATrsINC

l s .

All of the IGSCC susceptible welds in the recirculation system have received some form of mitigation treatment (weld overlay repair, IHSI, or RHSI). In addition, NYPA is planning to implement a hydrogen water chemistry system, which will modify the coolant chemistry suf ficiently to inhibit IGSCC initiation, thus producing a second mitigation for each susceptible weld.

i The combination of the above conservative activities provides adequate assurance of continued piping integrity. The continued operation of FitzPatrick with the mitigated piping systems is therefore justified for the long term.

l l

I l

l I

I l

l 6-3 gg Ob

g

7.0 REFERENCES

! . 1. U.S. Nuclear Regulatory Commission Generic Letter 84-11, "Inspection of BWR Stainless Steel Piping," April 19, 1984.

2. NUREG-0313, Revision 2, "Technical Report on Material Selection and Processing Guidelines for BWR Coolant Pressure Boundary Piping," issued for Public comment July 11, 1986, l and Finally Issued with Generic Letter 88-01 on January 25, i 1988.

3. "Fracture Mechanics Evaluation and Weld Overlay Design for Recirculation System Piping in the James A. FitzPatrick Nuclear Power Plant," Structural Integrity Associates, SIR-85-015, May 7, 1985.

4. Letter from John C. Brons (NYPA) to U. S. Nuclear Regulatory

. Commission, "Docket No. 50-333, Integranular Stress Corrosion j Cracking Inspection Results for the Roload 7/ Cycle 8 Refuel l Outage", JPN-87-018, April 9, 1987.

5. U.S. Nuclear Regulatory Commission, NUREG-1061, "Report of the U.S. Nuclear Regulatory Commission Piping Review Committee,"

a. Vol. 1, "Investigation and Evaluation of Stress Corrosion Cracking in Piping of Boiler Water Reactor Plants," Second i Draft, April 1984, i

b. Vol. 3, "Evaluat).on of Potential for Pipe Breaks,"

i November 1984.

6. EPRI NDE Center, "Examination of Weld Ove . iaid Pipe Joints",

Final Report, August 1986, EPRI RP-1570-2.

7. GE Report 22A2622, Rev. 1, "Design Report, Recirculation System for James A. FitzPatrick Nuclear Power Station, ANSI B31.1 Calculations," December 6, 1976.

8. ASME Boiler and Pressure Vessel Code, Section XI 1986 l Edition, Winter 1985 Addenda.

9. Letter from Leon Guaquil (New York Power Authority) to Hal Gustin (Structural Integrity Associates), "James A.

FitzPatrick Nuclear Power Plant Core Spray System Lead "B",

Summary of Stress Analysis for Weld Overlay Piping Calculations", with Attachments, dated February 6, 1987, PEL-87-010.

10. USAS B31.1, "Power Piping" 1967 Edition With Addenda Through 1969 (Original Code of Construction), and ANSI B31.1, 1977 Edition (used for material allowrble stresses).

7-1 STRUCTURAL INTEGRITY ASEWESINC uwwwmr~rar Esekr:M ~ @ u M&tp%Mid?h&G$55Y'YI$0Y

11. Structural Integrity Associates, "Fracture Mechanics Evaluation and Weld Overlay Design for Recirculation System

. Piping in the James A. FitzPatrick Nuclear Power Plant",

SIR-84-038, Rev 0, February 4, 1985.

12. "Weld Metal Cracking in Nine Mile Point Unit 1 Recirculation Pipe Joints," Letter, R. E. Smith to D. Norris (EPRI),

February 23, 1984,

13. Diercks, D. R. and Gaitonde, S. M., "Analysis of Cracked Core Spray from Quad Cities Unit 2 Boiling Water Reactor,"

Materials in Nuclear Enerov, 1983.

14. Horn, R. M., et al., "The Growth and Stability of Stress Corrosion Cracks in Large Diameter BWR Piping," Final Report, EPRI NP-2472, July 1982.

15. "Alternative Alloys for BWR Pipe Applications," EPRI NP-2671-LD, October 1082.

16. General Electric Company, "Third Party Review of the Technical Justification for Continued Operation of James A.

FitzPatrick, Nuclear Power Plant with Existing Recirculation System Piping", Transmitted by letter from J. Silva (GE) to T. Dougherty (NYPA) dated April 21, 1986: JS-86-0421-1.

17. "Assessment of the Feasibility of Producing Pipe Samples with Tight Through-Wall IGSCC, EPRI NP-2241-LD, February 1982.

18. "Verification of Intergranular Stress Corrosion Crack Resistance in Boiling Water Reactor Large-Diameter Pipe,"

Final Report, EPRI NP-3650"LD, July 1984.

19. Pickett, A. E., "Assessment of Remedies for Degraded Piping -

First Semi-Annual Progress Report," NEDC-30712-1, September 1984.

20. Pickett, A. E., "Assessment of Remedies for Degraded Piping -

Second Semi-Annual Progress Report," NEDC-30712-2, August 1984 - August 1985.

21. N. R. Hughes and A. J. Giannuzzi, "Evaluation of Near-Term BWR Piping Remedies, Vol. 1& 2", EPRI NP-1222, Nov. 1979.

22. "Extended Lifetime Test Program for Weld Overlays at Hatch, Unit 1", Structural Integrity Associates, SIR-84-030, September 1984.

23. "Continued Service Justification for Weld Overlay Pipe Repairs," EPRI, BWROG Ad Hoc Committee, May 25, 1984.

24. J. Park, D. Kupperman, W. Shack, "Examination of Overlay Pipe Weldments Removed from Hatch-2 Reactor," Argonne National Laboratory, September 1984.

I 7-2 STRUCTURAL i

INTEGRITY l

ASSOCIATESINC o

o 25- D. Becker, et al., "Examination of Weld Overlayed Pipe Joints," EPRI NDE Center Report RP-1570-2, April 1985.

26. J. Park and D. Kupperman, "Ultrasonic and Metallurgical Examinetion of a Cracked Type 304 Stainless Steel BWR Pipe Weldment," ANL-84-1, January 1984.

27. G. M. Wilkowski, et al., "Degraded Piping Program - Phase II," NUREG/CR-4082, BMI-2120, Semi-Annual Report, 10-84 to 3-85.

28. G. M. Wilkowski, et al., "Degraded Piping Program -

Phase II," NUREG/CR-4082, BMI-2120, Semi-Annual Report, 3-85 to 10-83 (Draft).

29. " n.tuction Heating Stress Improvement", EPRI NP-3375, November, 1983.

l l

STRUCTURAL INTEGRITY l ASSOCIATESINC l l

- -- -- . , - - ---a e a b

o s',

e 1

APPENDIX A TLAW EVALUATION CALCULATIONS

)

i l

r i

i i

4

. < - -..n-,..- . . ,-.., - - - . . . , . . . , _ - . . . - - . - , - - , - - , . . . -,.-.,.,..,..,,,,,,--_,,n., . ,,,, - --w.,--.--- -,n., ..--,n,.,,.

JPN-88-041, Responds to Generic Ltr 88-01 Re NRC Position on IGSCC in BWR Austenitic Stainless Steel Piping.Includes Insp Plans & Mitigation Plans.Separate Submittals Will Address Resistance Heat Stress Improvement & Change to Tech Specs

Contents

Text

Subject:

Reference:

Dear Sir:

SUMMARY

SUMMARY

1.0 INTRODUCTION

SUMMARY

7.0 REFERENCES

1.0 INTRODUCTION

1.1 Background

SUMMARY

SUMMARY

7.0 REFERENCES

Navigation menu

JPN-88-041, Responds to Generic Ltr 88-01 Re NRC Position on IGSCC in BWR Austenitic Stainless Steel Piping.Includes Insp Plans & Mitigation Plans.Separate Submittals Will Address Resistance Heat Stress Improvement & Change to Tech Specs

Text

Subject:

Reference:

Dear Sir:

SUMMARY

SUMMARY

1.0 INTRODUCTION

SUMMARY

7.0 REFERENCES

1.0 INTRODUCTION

1.1 Background

SUMMARY

SUMMARY

7.0 REFERENCES

Navigation menu

Search