ML20045E003

Summary of 930303 Meeting W/Numarc & PWR Owners Groups Re PWSCC of CRD Pentrations at Reactor Vessel Head.List of Attendees & Presentation Matls Encl

ML20045E003
Person / Time
Issue date:	03/31/1993
From:	Hermann R Office of Nuclear Reactor Regulation
To:	Richardson J Office of Nuclear Reactor Regulation
References
NUDOCS 9306300311
Download: ML20045E003 (57)

Text

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UNITED STATES NUCLEAR REGULATORY COMMISSION o

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NAR 31 1993

• • • a MEMORANDUM FOR:

James E. Richardson, Director Division of Engineering FROM:

Robert A. Hermann, Acting Chief Materials and Chemical Engineering Branch Division of Engineering

SUMMARY

0F MEETING WITH NUMARC AND PWR OWNERS GROUPS CONCERNING PRIMARY WATER STRESS CORROSION CRACKING (PWSCC) 0F CONTROL ROD DRIVE (CRD) PENETRATIONS AT REACTOR VESSEL HEAD On March 3,1993, the staff met with representatives of NUMARC and PWR Owners Groups for an update of the status and the progress todate of the PWR Owners Groups's Inconel 600 (Alloy 600) program regarding the safety evaluation and the inspection of control rod drive (CRD) penetrations in reactor vessel heads.

NUMARC coordinated the owners groups' presentation at the meeting.

A previous meeting discussing the same issue was held on November 20, 1992 A list of meeting attendees and a copy of the presentation materials are attached.

The presentation coordinated by NUMARC is summarized below:

(1)

PWR Owners Groups Sponsored Activities on CRD Penetrations The major on-going activities sponsored by PWR Owners Groups pertaining to the cracking of CRD penetrations are:

(a) Safety Evaluation All owners groups are in general agreement with WOG's conclusions presented to NRC in the November 1992 meeting that the reported axial cracking in the reactor vessel CRD penetrations is not an immediate safety issue.

The safety evaluation of Alloy 600 CRD penetration cracking performed by Westinghouse Owners Groups (WOG) justifying contin d operation of Westinghouse nuclear power plants was submitted to C for information via WCAP 13565 dated December 1992.

The subj t report was subsequently updated through a revisiondatedfebruary1993toincorporatetheresultsof additional stress analysis.

The CE and B&W Owners Groups stated that they will separately submit their own safety evaluation for continued operation of their plants since there are sufficient differences in their reactor vessel configuration and fabrication from the Westinghouse plants.

(b) Flaw Size Acceptance Criteria h

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Materials testing is on-going to generate more Alloy 600 crack

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i growth data and to verify the P.' Scott crack growth'model.

l Testing' is to. be performed on different heats of materials provided' by Huntington Alloys, the Swedish and CE. Additional heats:of.

materials will be'prov_ided by the French,:B&W andLCE.

Nearly all heats of Alloy. 600 materials used in' domestic;.PWR plants are expected to be covered in the testing program.

The NUMARC-

. representative stated that the flaw acceptance criteria will be l-submitted to NRC for review by July 1993~.

(c) Non-Destructive Examination (NDE) Demonstration EPRI~is coordinating the effort to develop'a1 demonstration prog' ram-for the' inspection of' Alloy.600 CRD penetrations using:. eddy.: current and ultrasonic. testing..(ECT and UT)-techniques..All the PWR owners groups'and NRC will particitate in+the. development of-this program.

EPRI will also manage the program forfqualifying:the examiners.

Examiners successfully demonstrated their inspection capabilities in

- flaw detection and sizing-on mock-ups equipment iwillL be-allowed to perform the CRD: penetration. inspection.)?The. preliminary..

demonstration program.is scheduled to'be' completed by February.1994.

The staff requested that a meeting with EPRI and PWR Owners Groups should be held asLsoon as po'ssible to discuss how the demonstration i

program should be handled since:a similart program _has;already beent l

established for IGSCC inspection.

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(2)

.Summarv'of CRD Penetration Crackina Exoerience

.NUMARC reported that CRD penetration inspections.'have been performed.on a total of 35 plants in' France, Sweden, Switzerland, Japari and Belgium.-

Out of 1,174 penetrations' inspected, 46 were:found to be cracked.

Except for the Bugey plants, all' cracks,found were short and' shallow.

(3)

Plant' Insoection Schedule The following three plants are scheduled to perform CRD. penetration -

inspection in 1994:

(a) Point Beach Unit 1 in Spring of 1994 (b) D.C. Cook Unit 2 in third quarter of.1994 (c) Oconee Unit 2 tin September 1994 h

.The owners of these units stated 'the scheduled inspection could.be.

postponed.if:the tooling including the mock-up-blocks' for inspection are not ready or if agreement on flaw acceptance criteria is not reached between the industry and the NRC'.

(4)

Evaluation of CRD Penetration Crackina Initiated From Outside Surface i

WOG reported:that, in~ addition to the axial flaw that leaked, a flaw -

about'3 mm long and 2.25 mm deep' initiated from the o'utside: surface was-

~ f ound in Bugey 3 penetration No. 54. The flaw 'was located above the !

weld oriented about130' from the. horizonal: pointing to: the' weld near' the.

hillside location. WOG ' performed a 3-D elastic plastic analysis:of.the.

flaw.. The results of the. analysis showed that there fis a very low' y_

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probability for this flaw to propagate since the stresses are very low in this region. WOG will continue to follow-up on this issue with French. WOG stated that their safety evaluation report will be revised within 60 days to incorporate the analysis of the outside surface cracking.

(5)

Activities on PWSCC Mitiaation for the CRD Penetrations EPRI reported that three methods to mitigate PWSCC in Alloy 600 penetrations are, currently under evaluation:

(a) Shot peening (b) Nickel-plating (c) Zinc injection The evaluation of the effectiveness of shot peening and nickel-plating in mitigating PWSCC is scheduled to be completed by December 1993.

Shot l

peening and nickel-plating have been used to mitigate cracking in steam i

generator tubes. The effect of zine injection on fuel corrosion, radiation fields, and PWSCC will be evaluated in a host PWR and a test reactor.

The preliminary testing is expected to be completed by December 1995. The staff stated that zine injection was used in several domestic BWRs to mitigate IGSCC and an unusually high radiation field buildup was reported in one plant from a natural zinc isotopic transofmration.

During the meeting the staff expressed a concern regarding the industry's inspection schedule.

Based on PWR owners groups proposed schedule the i

inspection of the CRD penetrations in domestic PWRs will not. start until'1994.

The staff stated that the. industry's reliance on a 6-year window for inspection scheduling may not be conservative for plants more susceptible to PWSCC. The concern comes from the inability to determine when leakage begins and, thereby, evaluai.; the wastage accurately since the starting point for leakage may not be accurately identified.

Although the staff agreed with the owners groups's conclusion that the subject CRD penetration cracking-is not a significant safety issue at this time, information and future events' could cause a reassessment of the safety significance of the cracking.

The staff requested that within the next two months the owners groups submit an assessment that would provide ~a rational.for the proposed inspection schedule.

The assessment should also address the available leak detection systems or additional systems needed to ensure there is no pressure boundary leakage occurring in the operating plants. The discussion should also address the ramifications of 1 gpm unidentified technical specification leakage limit in terms of detectability and consequences should pressure boundary leakage not be detected.

P I

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l Robert A.-Hermann, Acting Chief Materials and Chemical Engineering Branch Division of-Engineering i

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Enclosures:

(1) A List of Meeting Attendees j

(2) A Copy of Presentation Materials cc:

T. Murley W. T. Russell J. Partlow F. Miraglia B. D. Liaw C. Hinson C. Serpan _

W. Rosin /NUMARC S. Burns /WOG J. Taylor /B&WOG L. A. Walsh/WOG J. Hutchinson/CEOG 1

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Enclosures:

(1) A List of. Meeting Attendees--

(2) A Copy of Presentation' Materials cc:

T. Murley W. T. Russell

'J. Partlow F.I M'i raglia?

B.-D. Liaw C. Hinson.

.C..Serpan

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l S. Burns /WOG J. Taylor /B&WOG L. A.; Walsh/WOG J. Hutchinson/CE0G DISTRIBUTION l.

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ATTENDANCE LIST MARCH 3, 1993 MEETING WITH NUMARC AND PWR OWNER GROUPS CONCERNING PWSCC 0F INCONEL 600 l

NAME POSITION / AFFILIATION TELEPHONE N0; T. E. Murley 9/NRR/NRC-(301) 504-1270 i

W. T. Russell ADT/NRR/NRC (301) 504-1274 W. H. Koo Sr. Mtis. Engr., NRC/NRR/DE/EMCB (301) 504-2706 B. D. Liaw Dep. Dir. NRC/NRR/DE (301) 504-3298 l

R. A. Hermann Act. Chief /NRR/DE/EMCB g(301) 504-2768 j

Morris Schrum NUMARC (202) 872-1280 l

Alex Marion NUMARC (202) 872-1280 Sid Burns Sr. Proj. Eng/ Southern Nuclear'/W0G (205) 868-5061 Tom Spry Welding & Matls. Eng/CW Edison (708) 663-7268 Mike Melton APS/CE0G Alloy 600 WG Chair (602) 340-4623 Keith Reeser SCE/CE0G Alloy 600 WG'Vice Chair (714) 587-5422 John J. Hutchinson FPL (407) 694-4211 Rich Lauman Director Nuclear Main /NYPA (914) 681-6281 David Boyle Westinghouse ~

(412) 374--6690 Michael G.- Ball Westinghouse.

(412) 374-6597 Sydney W. Spencer TVA (615) 751-4778 Melvin Arey Duke Power Company (704) 382-8619:

l Charles - Lashkari PSEIG (609) 339-2754 Noman Cole MPR (703) 519-0200 l

L. Zerr STS 1(301) 652-2500 l

Steve Brewer AEP (614) 223-2020' Steve Hodge AEP (614) 223-1970 Kevin Graney Search Lic./Bechtel Power (301) 417-3299 Roy N. Brown NDE Manager /ABB Combustion Eng.

(615) 752-2304 Phil. Revel person's writing is unclear (703) 527-0039 David Lay AEA.0'Donnell (412) 655-1200 David Howell Westinghouse Nuclear Serv'. Div.

(412).374-5412 Rick Ri.;hel Westinghouse

-(412) 374-6365 A. W. Robinson B&W Nuclear Technologies (804) 385-3290 S. Fyfitch B&W Technologie~s (804) 385-3273 David Miskiewcz Florida Power Corp \\BWOG

-(813) 866-4414 David Whitaker Duke Power Co.

(704) 382-7246 Gary Engels-BW Nuclear Technologies (804) 385-2714 Jim Cirilli Northeast Utilities

-(203) 665-4675 Dick Cyboron ABB-CE (203) 285-9343 Don Wright BG&E (410) 787-5519 Frank Ammirato EPRI NDE Center (704) 547-6100 Raj Pathania EP.RI (415)'855-2998 i

Warren Bamford Westinghouse (412) 374-6515-

.Hal Gustin Structural Integrity (408) 978-8200 J. Davis NRC/DE/EMCB (301) 504-2713 Steve Hunt.

Dominion Engineering (703) 790-5544 Charles A. Tomes Wisconsin Public Service Corp.

(414) 433-1729 John Galembush Westingyhouse (412) 374-5036 Greg Calhoun Westinghouse (412) 374-4244 Al Butcavage RG&E (716) 771-2246 Albert E. Curtis.III APTECH Engrs (615) 499-3777

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ALLOY 600 CRDM PENETRATIONS l

INDUSTRY /NRC MEETING AGENDA l

MARCH 3,1993 j

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INDUSTRY STRATEGY i

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PLANT DATA

SUMMARY

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OWNERS GROUP ACTIVITY l

MATRIX e

NDE DEMONSTRATION e

STRUCTURAL INTEGRITY e

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Planning Schedule for Industry Actions on CRDM Penetrations 1994 1993 C3 Stject Nov l Dec Jan l Feb l Mar l Apr l May l Jun l Jul l Aug l Sep l Oct l Nw/[Dec/Jan l Feb l Mar l Apr l May l Jun l Jul l Aug l Sep SafetyEvaluabonErwelope

• Umetesww emw! 4 ~ We ' 4we ' *ws - M*nme W&m +*i " ' o w w u w w xrweere ak Flaw Size AcceptatAty Anahsis Analysis Criteria ( Goals / Obgechwes )

Crack Growth Testing (Irdal Result:)

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Venficahon of P. Scott Modsi 853 2..

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Analyas RnalResults

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I NDE D T,a.in i. ors configurabon Study

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• Note: Safety Evaluation Envelope extends for a minimum of 6 years.

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PLANT DATA

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SUMMARY

Head Penetrations Plants Total Penetrations inspected -

- K Hours Temperature With

. Country Plant Type Penetrations inspected g

Indications -

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'6 80-90 596-599 390.

304 19 I

CPY 3

.80 552-195 134 8

.1300MW-9 30 589-597 693 392 9

19K 190 8

Sweden 3 Loop 3

75-115 580-606 Switzerland 2 Loop 2

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Japan Various 11 -

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Belgium 3 Loop 1

-120 596 65 65-0.

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RE OTOR VESSEL ALLO 300 l

O.D. INITIATED CRACKING-O Cracking Found on Bugey 3 Penetration j

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Secondary Circumferential Crack Oriented 30 From~ Horizontal and Propagated Downward i

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> 0.12 inch (3 mm) long-0.09 inch (2.25mm) deep'

> Stress Corrosion Crack 3

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SUMMARY

e INFORMATION ON FOREIGN PLANTS IS BEING' GATHERED j

THROUGH VISITS AND MEETINGS

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THERE WAS STRONG PARTICIPATION BY'EdF AND OTHER FOREIGN UTILITIES AT THE DECEMBER,1992 EPRI WORKSHOP ON ALLOY 600 4

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e THE EXTENT AND SEVERITY OF CRACKING IN THE.

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SWEDISH, BELGIAN, SWISS, AND JAPANESE PLANTS APPEARS TO BE LESS THAN IN EdF PLANTS i

e THE REASONS ARE NOT' ENTIRELY CLEAR BUT COULD BE i

RELATED TO MICROSTRUCTURE OF THE ALLOY 600 j

MATERIAL AND FABRICATION HISTORY l

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ALLOY 600 VESSEL HEAD PENETRATION CRACKING CURRENT OG/EPRI EFFORTS

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TASK ELEMENT WOG CEOG B&WOG EPRI Root Cause of Cracking X

X X

X Key Material & Operation Parameters X

X X

X Elastic Finite Element Analysis:

X X

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Residual / Operational Elastic / Plastic Finite Element Analysis:

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Residual / Operational: 3 Locations (ICI vs CEDM)

Crack Propagation / Acceptable Flaw Size X

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Analysis Penetration Leakage & Vessel Head X

X X

Wastage Assessment Safety Evaluation X

X X

X Plant Screening / Susceptibility. Criteria

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Material Microstructure Characteristics X

(Prov Mat'l)

(Prov Mat'll X

Leakage Detection Methods Survey X

X X

Grinding Effect on Residual Stresses X

'4 Penetration Material Crack Growth Data X

(Prov Mat'l).

(Prov Mat'l)

(Lit Search)

NDE Industry Standards Specification X

X X

X NDE Performance Demonstration Standard (Mock-Up)

X-X industry Concurrence of NDE Standards X

X X

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Eva!uation of' Repaired Configurations X

X X

.OD Initiated Crack Assessment X

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Extended Microstructure Assessment

-X Extended Crack Growth Testing X

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Alloy 600 CRDM

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Penetration Inspection i

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F. Ammirato EPRINDE Center Chairman, AHACInspection Subgroup l

Presented at l

AHAC/NRCInformation Meeting

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Outline

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Background===

. Objective 1

s Organization Approach i

Technical Considerations

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Several Organizations Have Developed, Qualified' & Applied

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Inspection Procedures in Europe i

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e Typical Procedures involve:.

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ECT for Crack Detection &

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i UT for Crack. Depth Sizing.

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e Qualification.of These Techniques l

Must:Be Performed for U.S. Plant i

Configurations L

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Inspection Program l

Objective i

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Develop a Capability to Enable

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Inspection of CRDM Penetrations i

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Organization l

Inspection issues Are Addressed in 1

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NSSS Vendors, NSSS Owners Group j

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Utilities, EPRI, & NDE Center Are.

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Approach l

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Demonstrate Procedures on l

Realistic Mock-ups l

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Proposed Mock-up; Matrix Includes-l CRDM (W, CE, B&W) & ICl.(CE) i Inspection Capabilities to Be l

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j Detection l1

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Length Sizing

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Depth Sizing i

L Location w.r.t Weld i

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• Mock-ups Will Include Essential.

Geometric & Material Conditions i

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- Weld (Outermost Penetration j

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- Clearances I

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• Demonstrations Will Be Blind l

- Each. Organization Will Be Given j

Their Results

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- Utilities:Can Verify Results at the NDE Center

- EPRILWill Publish:Results without 4

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NDE Responses of Intentional Flaws j

Will Be Benchmarked against

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European Experiences-l (EdF &.Ringhals) i Essential Variables-of Procedures

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L Will Be Recorded Mock-ups Will include a Range of Flaw Lengths (from < 3 mm to > 10 mm) &

l Depths (from < 0.5 mm to > 4 mm) to i

Enable Evaluation of Capability ofl y

i Various Candidate Techniques l

Removable Thermal Sleeves Will l-Be included

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Schedule

• Complete Configuration Study Feb.1,1993

• Complete Draft Mock-up March 15,1993 Specification & Distribute for Comment s

• Complete Final Mock-up April 15,1993 Specification -

• Complete Draft Demonstration May 15,1993 Protocol & Distribute for Comment

• Complete First Full-scale Dec.15,1993 l

Mock-up Set

• Complete initial Jan.30,1994 ISI Demonstrations I

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• Follow-On ISI Demonstrations As Required m,

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N& ARC ALLOY 600 A$

STRUCTURAL INTEGRITY SUBGROUP f

9 PURPOSE:

TO FACILITATE U.S. INDUSTRY COOPERATION IN THE RESOLUTION OF THE CRDM PWSCC ISSUE E

G PARTICIPANTS:

NUMARC j

EPRI' UTILITY OWNERS GROUPS j

B&WOG CEOG WOG VENDORS

i ABB-COMBUSTION ENGINEERING e

l B&WNT WESTINGHOUSE _

j SEVERAL' INDIVIDUAL UTILITIES i

DOMIMlON' ENGINEERING, INC.

9 MEETINGS HELD:

OCTOBER,1992 WASHINGTON D.C.

NOVEMBER,1992 CHARLOTTE,NC DECEMBER,1992-ORLANDO; FL.

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JANUARY,1993' JUNO BEACH, FL-9 lSSUES COVERED:-

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STATUS OF REPORTED CRACKING c

STRESS ANALYSIS CRACK GROWTH RATE DATA'

CRACK GROWTH CALCULATIONS SAFETY ANALYSIS-

NbARC ALLOY 600 AMC l

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STRUCTURAL INTEGRITY SUBGROUP l.

STATUS OF REPORTED CRACKING i

O ACTIVITIES s

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SHARED REPORTS OF INSPECTIONS PERFORMED IN-EUROPE TO THE EXTENT THAT THEY COULD BE SHARED WITH OTHERS SHARED RESULTS OF FAILURE ANALYSES PERFORMED ON CRACKED CRDM NOZZLES IN EUROPE j

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SHARED RESULTS OF CRACK ACCEPTANCE CRITERIA i

AND REPAIR METHODS TO THE EXTENT THAT THE i

INFORMATION COULD BE SHARED WITH OTHERS' i

o CONCLUSIONS PARTIES INVOLVED WITH THIS ISSUE HAVE BEEN BETTER' INFORMED REGARDING THE EXTENT OF THE-CRACKING' PROBLEM IN EUROPE SHARED INFORMATION HAS BEEN USEFUL IN CAllBRATING ANALYSIS MODELS' i

SHARED INFORMATION-HAS BEEN USEFUL IN COMPLETING THE SAFETY -ANALYSES I

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NOARC ALLOY 600 AO c'

4 STRUCTURAL INTEGRITY SUBGROUP STRESS ANALYSIS 4

4 ACTIVITIES i

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e DISCUSSED METHODS USED TO PERFORM ELASTIC-4 PLASTIC FINITE ELEMENT ANALYSES.OF CRDM NOZZLES. AREAS COVERED INCLUDE:

GEOMETRY DIFFERENCES AMONG DESIGNS MATERIAL PROPERTIES WELDING SIMULATION METHODS 1

MODELING OF NOZZLE INTERFERENCE FIT REQUIRED MESH DENSITY STRAIN HARDENING MODEL e

REVIEWED RESULTS OF FINITE ELEMENT ANALYSES AS THEY WERE COMPLETED BY VARIOUS i

ORGANIZATIONS e

DISCUSSED HOW TO APPLY ANALYSIS RESULTS TO PREDICTING CRACK LOCATIONS AND CRACK GROWTH ' RATES 9

CONCLUSIONS e

STRESS ANALYSES CLEARLY IDENTIFY THE SOURCE OF HIGH STRESS CONTRIBUTING TO CRDM NOZZLE PWSCC e

ANALYSIS RESULTS ARE CONSISTENT WITH THE FIELD REPORTS OF AXIAL CRACKS ON THE UPHILL AND DOWNHILL SIDES OF PERIPHERAL ROW-NOZZLES e

STRESS ANALYSIS RESULTS CAN BE USED FOR CRACK PROPAGATION -ANALYSES STRESS ANALYSIS RESULTS ARE USEFUL FOR DEVELOPING INSPECTION. STRATEGY.

MARC ALLOY 600 AOC g-STRUCTURAL INTEGRITY SUBGROUP CRACK GROWTH DATA O

ACTIVITIF,3 REVIEWED EXISTING CRACK GROWTH RATE DATA' FOR ALLOY 600 MATERIALS 4

REVIEWED CRACK GROWTH RATE DATA GENERATED l

FROM FIELD CRACKING OF ALLOY 600 PARTS i

i REVIEWED TEST PROGRAM TO OBTAIN ADDITIONAL CRACK GROWTH DATA ON FORGED MATERIALS TYPICAL OF CRDM NOZZLES OWNERS GROUPS CONTRIBUTED MATERIALS TO CRACK GROWTH RATE DATA TEST PROGRAM i

I e

CONCLUSIONS _

THERE IS GENERAL AGREEMENT REGARDING THE CRACK GROWTH RATE DATA WHICH SHOULD BE USED FOR PRESENT CALCULATIONS i

GROWTH CALCULATIONS PERFORMED USING THIS DATA ARE IN REASONABLE AGREEMENT WITH EUROPEAN FINDINGS INDUSTRY lS COOPERATING TO OBTAIN ACDITIONAL GROWTH RATE DATA FROM TESTS AND CRACKS LEFT IN SERVICE IN EUROPE 4

4 i

NAARC ALLOY 600 AMC STRUCTURAL INTEGRITY SUBGROUP CRACK GROWTH CALCULATIONS.

4 8

ACTIVITIES l

e REVIEWED MODELS FOR CRACK PROPAGATION IN THREE AREAS:

RADIAL GROWTH OF PART DEPTH CRACKS GROWTH OF THROUGH WALL AXIAL CRACKS BELOW WELD GROWTH OF THROUGH WALL AXIAL CRACKS i

ABOVE WELD COMPARED RESULTS OF CRACK GROWTH ANALYSES i

i

^

9 CONCLUSIONS i

e CALCULATED RADIAL GROWTH OF PART DEPTH l

CRACKS IS IN REASONABLE AGREEMENT WITH FIELD l

EXPERIENCE 4

GROWTH OF THROUGH WALL AXIAL CRACKS BELOW

~

THE WELD IS SLOW THROUGH WALL AXlAL CRACKS WILL GROW VERY SLOWLY ABOVE WELD'DUE TO LOW APPLIED STRESSES AND LIMITED CRACK OPENING i

DISPLACEMENT AS A RESULT OF INTERFERENCE FIT OF NOZZLE IN VESSEL HEAD 1

I

N& ARC ALLOY 600 AMC i

STRUCTURAL INTEGRITY SUBGROUP i

SAFETY ANALYSES 9

ACTIVITIES REVIEWED CALCULATIONS FOR THE MAXIMUM ACCEPTABLE CRACK LENGTH i

j SHARED RESULTS OF BORIC ACID CORROSION TESTS WHICH WAS USED TO PREDICT THE AMOUNT OF--

LEAKAGE WHICH CAN BE ACCOMMODATED WITHOUT EXCEEDING ASME CODE STRUCTURAL 4

LIMITS-IN THE HEAD REVIEWED SAFETY ANALYSIS-PRESENTED BY-WESTINGHOUSE OWNERS GROUP TOTHE NRC ON NOVEMBER,1992 i

G CONCLUSIONS 4

e ALL PARTIES ARE IN GENERAL AGREEMENT WITH THE CONCLUSIONS IN THE WESTINGHOUSE OWNERS GROUP PRESENTATION TO THE NRC

~

~

NOARC ALLOY 300 AIOC i

i STRUCTURAL INTEGRITY SUBGROUP i

OVERALL CONCLUSION

~

j e

THE STRUCTURAL INTEGRITY SUBGROUP HAS BEEN i

EFFECTIVE IN SEVERAL AREAS:

MINIMlZING THE TIME TO DEVELOP AN INDUSTRY RESPONSE TO THE CRDM PWSCC ISSUE l

MINIMlZING THE AMOUNT OF UNNECESSARY j

DUPLICATION OF EFFORT' ENSURING THAT ANALYSIS RESULTS AND l

CONCLUSIONS ARE SUBJECTED TO PEER REVIEW l

BEFORE REPORTING RESULTS ENSURING THAT THERE IS SUBSTANTIAL AGREEMENT AMONG' INDUSTRY PARTICIPANTS

{

BEFORE REPORTING RESULTS 9

THE OVERALL CONCLUSIONS OF THE SUBGROUP ARE AS l

FOLLOWS:

THERE IS AGREEMENT REGARDING THE CAUSE OF THE CRDM NOZZLE PWSCC ANALYTICAL RESULTS ARE CONSISTENT WITH THE FIELD REPORTS OF AXIAL CRACKS ON THE UPHILL AND DOWNHILL SIDES OF PtiRIPHERAL ROW-NOZZLES CRACK GROWTH CALCULATIONS -ARE BELIEVED TO BE IN REASONABLE AGREEMENT WITH KNOWN FIELD-EXPERIENCE AND. EUROPEAN FINDINGS ALL PARTIES ARE lN GENERAL AGRFEMENT WITH THE CONCLUSIONS WHICH THE WESTINGHOUSE OWNERS GROUP PRESENTED TO THE NRC IN-NOVEMBER,1992:

A

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i 4

l 1

1 J

k I

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4 I

e i

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J d

i, d

4 4

W 1

J 4

'l 4

+

4 MITIGATION 4

4 i

1 J

J e

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k l

k 4

4 i

l 4

a 1

4 k

4 4

?

l o

o i

i l

l EPRI Activities on PWSCC Mitigation l

of Alloy 600 Penetrations i

j

- i i.

-s i

Raj 'Pathania i

EPRI

)

NRC-NUMARC-PWR. Owners Group-Meeting on eac or Vessel Head Penetration Issue R

t March 3,1993

-Rockville, Maryland 4

,..4

..,.4 yyeg4 ye

.r44, y

,s u--

+

,-m..a

..,E EPRl/NP t

Mitigation Methods for PWSCC of Alloy 600 L

9 EPRI is evaluating three methods to mitigate PWSCC in Alloy 600 penetrations.

i

1. Shot peening i

a

[

2. Nickel-plating

3. Zinc injection

].

i 1

j

- CORROSION i

R. Pathania NRC-NUMARC 3/3/93-1 i

i i

,,m

1 EPRl/NP Shot Peening L

Shot peening has been used to mitigate e.

L PWSCC of Alloy 600 steam generator tubes.

i Welded mockups of Alloy 600 will be peened

[

using field procedures and exposed to test l

environments along with unpeened control ll specimens.

i l

[

The effectiveness.of peening will be evaluated g-

[

by comparing test and control specimens.

[:

Evaluation to be completed by 12/93.

CORROSION f

. R. Pathania NRC-NUMARC 3/3/93-2 i

f

L

~.

EPRl/NP Nickel-Plating i

Nickel-plating of steam generator tubes has ej L

been used in several PWRs in Europe to stop the progression of PWSCC cracks.

r Welded mockups of Alloy 600 will be nickel plated and exposed to test environments along with control specimens.

r

[

The effectiveness of nickel plating will be evaluated by comparing test and control specimens.

Evaluation to be completedLby 12/93.

l

(

i CORROSION R. PWiwh NRC-NUMARC EM 3 i

4

'e

~

EPRl/NP-Zinc Injection i

Previous studies by Westinghouse, WOG and EPRI i

have shown that small amounts of zinc in the primary i

j coolant can reduce the build-up of radiation fields-gl and delay PWSCC.

L EPRI and WOG propose to evaluate zinc injection in a cooperative program.

i The.effect of zinc injection on fuel corrosion will be L

[

evaluated in a test reactor.

l The effect of zinc injection on fuel corrosion, l

radiation fields and.PWSCC will be evaluated in a g

i host PWR.

The benefits of zinc injection will be quantified.

[

First cycle of operation to be completed by 12/95.

[

. CORROSION 4

b b -----

4 O

O 1

I i

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3 e

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CRACK GROWTH 4

i POTENTIAL EVALUATION i

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..._,,....m.',

,,,,.,.y.

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l CRACK GROWTH P0TENTIAL i

1 FOR l

OUTSIDE SURFACE FLAWS b

IN I

1 HEAD PENETRATIONS H

i l

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l

i i

l WARREN BAMFORD L

l WESTINGHOUSE ENERGY SYSTEMS j

p l'

1 M

i-

_ ~., _

e l

O o

l o

BACKGROUND i

i l

o GE0 METRY 1

l l-i-

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STRESS ANALYSIS 5

i t

o a

o DRIVING FORCE (K)

CALCULATIONS

)

i 1

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o CRACK GROWTH LAWS' 4

l o

RESULTS i

u 1

i-L I

O O

BACKGROUND O

ALL CRACK GROWTH CALCULATIONS TO DATE HAVE TREATED INSIDE SURFACE FLAWS O

ONE OUTSIDE SURFACE FLAW HAS BEEN FOUND -

BUGEY 3 PENETRATION NUMBER 54 O

SIZE:

3 MM LONG 2.25 MM DEEP 1

O LOCATION:

300 FROM HORIZONTAL, ABOVE THE WELD AND POINTING TOWARD THE WELD O-EXACT-CIRCUMFERENTIAL LOCATION IS'NOT AVAILABLE, BUT.IT IS NEAR THE ZERO DEGREE (HILLSIDE)

POSITION.

O GE0 METRY 0

FLAW ORIENTATION MAKES PROPAGATION TO FULL CIRCUMFERENCE VERY UNLIKELY O

PLANE-OF'THE FLAW INCLUDES APPROXIMATELY 1800 UNDER THE WELD, AND 1800 ABOVE THE WELD O

LOCATION CHOSEN FOR ANALYSIS:-

OUTER MOST PENETRATION FOR A FOUR LOOP PLANT l

0 POSSIBLE PATHS OF PROPAGATION

)

L 1

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

.,_______m__-,,__-_,,__

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g to Q) c) ->c m

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STRESS ANALYS E l

i 4.

!.O RESULTS OF 3-D ELASTIC PLASTIC. ANALYSIS USED i

i

(

I 1

i O

LOADING SEQUENCE:

- WELDING (2 PASSES) j

- HYDROTEST. (-'.4 ICE) i

- STEADYSTATE OPERATION l

- COOL DOWN l

- STEADYSTATE OPERATION

)

4 l

l l0 h'RESS TRANSVERSE TO PLANE OF CRACK USED L

i l-!O THROUGH-WALL STRESSES AROUND. ENTIRE j

i.

PENETRATION CONSIDERED i

1 i

IO RESULTS 1.

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700006-

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MIN =276 37 649 %n 3 8.2 6000gyens AVO 61:27.6 Imi4 9 10100 8 soor.gyerie AVG a595.49 1r 38M. -113 M.3 del.4W M 26.M 221 W DEL 42745.7 2914M 7 23951 9 g '-

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p y4 481 6

If AVO 196343 -816.84

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+

e e

-1

-gy 94-d6 'ds' '1'D' d l'4' I!6 I'N' b 'f2' 8-16 % 33 3tz 3%-M8 - @

- g7g-g - *gy _ -g_ - g3_ _ gy zyg-- g - gy-- ggg -

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= - -

= - -

O o

j i

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1 i

1 AVERAGE THROUGH WALL STRESSES J

r AROUND CIRCUMFERENCE.OF TUBE-15' i

e..

.. e.

10

~~ - o; 4

l.

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o CD CUT 1: PLANE OF FLAW O

i CUT 2: PLANE OF FLAW

-5

.. - -A..

ALONG WELD

. e..-

' 0 45 90 135 180 ANGLE (DEGREES)

HILLSIDE -

CENTERSIDE

~!

l l

..,,.a,

i O

O

j i

DRIVING FORCE (K)

CALCULATIONS

i i O SEMI-ELLIPTIC SURFACE FLAW -

i 1

RAJU-NEWMAN EXPRESSION 1

1 I

1 j

. I fO THROUGH-WALL STRESS DISTRIBUTIONS USED AT 1

j EACH LOCATION AROUND CIRCUMFERENCE I

t ij-

!O APPLIED K VALUES ARE VERY LOW i

i f

i i

4

}

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l 1

1 I

k

. ~, -

-,.,...,,n w

,,_,.r.

,e.

.. ~..... -,. -.,,,.

.-,-w

,,.n,,,

-,,e,,

,..,.-.a,y e,.n,v,..,,e.,.,enn.,--

,... ~,.,mn,.

FDRIVINGFORCf(K1RESULTS f'

SUMMARY

i i

ANGLE CUT No.

K=9 DEPTH (A T)KMAx--

KMAX FR (DEGREES)

(A/T).

i l

0 1

N/A; 22.5 2

0'.29

.0.90 19.5 45 3

0.65 0.90 21.0 67 5

.4 0.78

.0.90 14.4--

90 5

N/A 0.04 7.1-i 124 7 N/A.

N/A N/A 146 7-8 0'.72 0.90 14.8 169 8-9 N/A 0.78

.5.1 B

i

... -. -. -. _... - ~,... -....... -.....

O O

1 CRACK GROWTH LAWS Io ORIGINAL FORMULATION USED FOR INSIDE. FLAWS I

i i

l i

4

!o GE/EPRI WORK:

OXYGENATED WATER. ENVIRONMENT a

i L

i i

s

,,y r.

w.e----,,,vr'

,,r-

.4

..--..ea.-,

.,,.w.

__,+Eew-e.,

.-.,,w%,me.

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v e m.--e w i

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1 j

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5 5

k f

1 i '

a l

T l

4 10 4

f 4

4

~

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4 l

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10 r 1

~

& = 2.8 x 10 2(K-9)1.14 I

+1

~

f.

s,-

/,,,

p *

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tl E

.i O

10 f

C,

./

/

l 1

t 1

i 1

I' i

i i

i

-11 s

10 i

i i

i.

..i o

10 20' 30 40 L50.

60 1

i i:

Stress intensity, K(MPav'iii) i f

I

[

i i

o MODEL FOR SCC GROWTH RATES IN ALLOY'600 IN 4

-PRIMARY. WATER ENVIRONMENTS o

.mase 4

e.

,W 4

--'h""

F M

1, t4"T

1. '--m' E

w9'

• My1 W

Wiy P D-Ep TyT g-W*g'W

sd O

o MPa fm 20 30 40 1 '

10

- sms won is2/soo

~3

- DA AT/%DJt CONST. LOAO (

g m y 132' 10 0.94/m @4 f

-ga p1/cm 03 01.0 ps/cm

~

1.0

~

PftEDIClO culM3 (ib) y SASED ON 304SS iSC/cm2 j

)

-7 j

j

( 10 g

g 10 0.s

_4 E

P o

uf a'

.E

~

0.3 N

g-G r

a

- \\

4\\

]

-s N

3 10 E

a

..o

-5 3 o 3 10 ai

[

O g

0

~

O

.a' g

o z

_g u 10

-6 (10 e

r 1

-1 g 1

i 10 0

20 30 40 YI STRESS INTENSITY, ksidIR -

MODEL FOR SCC GROWTH RATES IN ALLOY 600 IN-

' OXYGENATED PRIMARY-WATER ENVIRONMENTS

\\_

o 9

1 RESULTS i

p i

1 i

L i

!:0 LOW PROPENSITY FOR.THROUGH-WALL PENETRATION l

1

- ALONG THE PLANE 0F THE: EXISTING CRACK i

- THROUGH THE WALL AT ANY LOCATION AB0VE 4

i THE WELD

.e i

i l

o

~ COULD THE CRACK TURN AND PROPAGATE 1ALONG:THE WELD?

STRESSES SHOW THIS UNLIKELY l

i.

o CALCULATIONS SHOW A VERY LOW PROBABILITY OF CRACK EXTENSION IN THIS REGION e

5 i

}

l:

_ ~. ~., _,

O O.

CONCLUSION (PRELIMINARY?

i.

i-Results of Our Evaluation Show No Reason to.. Change theLConclusions of the Safety Evaluation i

I l

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