ML020510559

02/08/02 Meeting Summary Regarding Control Element Drive Mechanism Cracking Issues

ML020510559
Person / Time
Site:	Fort Calhoun
Issue date:	02/14/2002
From:	Marschall C NRC Region 1
To:	Ridenoure R Omaha Public Power District
References
Download: ML020510559 (48)

Text

February 14, R. T. Ridenoure Division Manager - Nuclear Operations Omaha Public Power District Fort Calhoun Station FC-2-4 Adm.

P.O. Box 550 Fort Calhoun, Nebraska 68023-0550

SUBJECT:

FORT CALHOUN STATION - MEETING TO DISCUSS CONTROL ELEMENT DRIVE MECHANISM (CEDM) CRACKING ISSUES

Dear Mr. Gambhir:

This refers to the meeting conducted at Arlington, Texas, on February 8, 2002, between your staff and the NRC. The participants discussed the similarities and differences between Fort Calhoun Station and Palisades Station CEDMs.

The discussions included the actions you have taken and plan to take to ensure early detection and corrective action for potential cracks in the CEDM upper housing welds. Your staff agreed to provide the results of the examinations performed on drive housings during your next refueling outage.

The attendance list and presentation slides are enclosed with this summary (Enclosures 1 and 2, respectively).

In accordance with 10 CFR 2.790 of the NRC's "Rules of Practice," a copy of this letter and its enclosures will be available electronically for public inspection in the NRC Public Document Room or from the Publicly Available Records (PARS) component of NRCs document system (ADAMS). ADAMS is accessible from the NRC Web site at http://www.nrc.gov/reading-rm/adams.html (the Public Electronic Reading Room).

Sincerely,

/RA/

Charles S. Marschall, Chief Engineering Branch Division of Reactor Safety Docket: 50-285 License: DPR-40

Omaha Public Power District Omaha Public Power District

Enclosures:

1. Attendance List

2. NRC Presentation cc w/enclosures:

Mark T. Frans, Manager Nuclear Licensing Omaha Public Power District Fort Calhoun Station FC-2-4 Adm.

P.O. Box 550 Fort Calhoun, Nebraska 68023-0550 James W. Chase, Division Manager Nuclear Assessments Fort Calhoun Station P.O. Box 550 Fort Calhoun, Nebraska 68023-0550 David J. Bannister, Manager - Fort Calhoun Station Omaha Public Power District Fort Calhoun Station FC-1-1 Plant P.O. Box 550 Fort Calhoun, Nebraska 68023-0550 James R. Curtiss Winston & Strawn 1400 L. Street, N.W.

Washington, D.C. 20005-3502 Chairman Washington County Board of Supervisors Washington County Courthouse P.O. Box 466 Blair, Nebraska 68008 Sue Semerena, Section Administrator Nebraska Health and Human Services System Division of Public Health Assurance Consumer Services Section 301 Centennial Mall, South P.O. Box 95007 Lincoln, Nebraska 68509-5007

Omaha Public Power District Electronic distribution from ADAMS by RIV:

Regional Administrator (EWM)

DRP Director (KEB)

DRS Director (ATH)

Senior Resident Inspector (WCW)

Branch Chief, DRP/C (KMK)

Senior Project Engineer, DRP/C (vacant)

Staff Chief, DRP/TSS (PHH)

RITS Coordinator (NBH)

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/RA/ T /RA/

02/11/02 02/14/02 OFFICIAL RECORD COPY T=Telephone E=E-mail F=Fax

ENCLOSURE 1 ATTENDANCE LIST Licensee:

D. Bannister, Plant Manager M. Frans, Manager, Nuclear Licensing W. Gates, Vice President, Nuclear R. Lisowyj, Senior Nuclear Design Engineer J. McManis, Manager, Design Engineering R. Phelps, Division Manager, Nuclear Engineering R. Ridenoure, Division Manager, Nuclear Operations K. Woods, Senior Nuclear Design Engineer NRC:

L. Berger, Branch Secretary K. Brockman, Director, Division of Reactor Projects (DRP)

A. Howell, Director, Division of Reactor Safety (DRS)

K. Kennedy, Chief, Projects Branch C, DRP C. Marschall, Chief, Engineering and Maintenance Branch, DRS E. Merschoff, Regional Administrator, Region IV C. Paulk, Senior Reactor Inspector, DRS W. Walker, Senior Resident Inspector A. Wang, Project Manager, Office of Nuclear Reactor Regulation L. Willoughby, Resident Inspector

ENCLOSURE 2 Licensee Presentation

Control Element Drive Mechanism Housing Reliability A presentation to the NRC by the Fort Calhoun Station Staff February 8, 2002, Arlington, Texas

Agenda

• Introductions - Gary Gates

• Agenda Review - Ralph Phelps

• Summary of Fort Calhoun Station Initiatives - Joe McManis

• CEDM Housing Mechanics Discussion -

Kirby Woods

Agenda

• CEDM Housing Materials Characterization Discussion - Bob Lisowyj

• Conclusions - Ralph Phelps

• Closing - Ross Ridenoure

Joe McManis, P.E. - Manager, Design Engineering Summary of Fort Calhoun Station Initiatives Regarding CEDM Reliability

Operating Experience

• CEDM Housing Assemblies

- Seal Housing

• J-groove weld

- Palisades 1986-1990 &

1999-2001

- Upper Housing

• Overlay weld

- FCS 1990

• V-groove weld

- Palisades 2001

- VHP Nozzles

• J-groove weld

• -INSIGHT-

FCS CEDM Inspections

• Performed

- Seal Housing

- Upper Housing

• Planned

- Seal Housing

• Program plan

- Upper Housing

• 10 yr ISI

• Commitments(1991)

- Perform HJTC housings UT (10 yr ISI)

- Clean/Visually Inspect RV Head

VHP Nozzle

• Oconee 3 Event

- Circumferential Cracking

- Bulletin 2001-01

• Effective Full Power Year

- Time-at-Temperature Model

- FCS 17.9 EFPY

• Low Probability of Rupture and/or Excessive Leakage

• Effective Visual Inspection during May

FCS Susceptibility Assessment

• Environment Susceptibility Assessment

- Chlorides Description Environment Tensile Residual Stresses Temp.

- Oxygen Location Type Chlorides Oxygen Axial Hoop

- Stagnancy Seal Housing j-groove High High Low High Moderate 1034'-7"

• Residual Stress Upper Housing Autoclave Flange double v-groove High Moderate Moderate1 N/A Moderate 1033'-9"

- Longitudinal Upper Housing overlay Low Low Moderate1 Low Moderate Pipe

- Circumferential 1022'-4" Modified Eccentric double Low Low Moderate1 N/A Moderate

• Temperature Reducer Large Diameter v-groove 1021'-8"

• Conclusion Modified Eccentric double Low Low Moderate1 N/A Moderate Reducer v-groove

- Seal Housing Small Diameter 1021'-3" Highest Risk Note: 1 - This moderate stress peaks at the weld root and dissipates within the weld area.

Key Differences

• Fort Calhoun Station has:

- Time

• CEDM through-wall cracks

- Operation

• Maintenance outage

- Thermal Sleeve

• Palisades extends to their reactor vessel flange

- Program Plan

Material Reliability Focus

• Operating Experience

- Seal Housing

- Upper Housing

• Program Plan

- Predictive and Environmental Model

- Inspection, Remediation and/or Repair Plan

• Overview of Issues

- Responses

- Actions

Introduction of Program Managers

• Two Individuals Providing Oversight of the Issue

• Kirby Woods - PE, MS, Worked on Issue since early 1998

• Bob Lisowyj - PhD, Worked on Issue since 1990

Kirby D. Woods - Senior Nuclear Design Engineer CEDM Housing Mechanics Discussion

CEDM - Seal Housing Assembly

• Longest Stagnant Area

- Oxygen

- Leachable Chloride

• Flexitallic gasket, o-rings and graphitar (~50 ppm)

• Residual Stress

- Fabrication Records

• Residual Stress (33 to 75 mils shrinkage)

• Temperature

• Operating Experience

• -PRECURSOR-

CEDM - Seal Housing Assembly

• Interpretation

- Residual Stress

• J-groove weld

• Transverse shrinkage

- Axial stress

- Hoop stress

- Temperature

• ~250º F/121 º C

- Palisades experience

• Inverted Bath Tub Curve

CEDM - Seal Housing Assembly

• Weld Induced Shrinkage

CEDM - Seal Housing Assembly

• Longitudinal Driver

CEDM - Seal Housing Assembly

• Circumferential Driver

CEDM - Seal Housing Assembly

• Temperature Relationship

CEDM - Seal Housing Assembly

• Interpretation

- Residual Stress

• J-groove weld

• Transverse shrinkage

- Axial stress

- Hoop stress

- Temperature

• ~250º F/121 º C

- Palisades experience

• Inverted Bath Tub Curve

• High Susceptibility

CEDM - Upper Housing Assembly

• Through-wall Crack 1990

- non-vented housing

• RC-10-9 & 13 Spare

• 100% stagnant

• Line B showing maximum level of stagnancy

- Source of Tensile Stress

• Overlay Weld

• -WORST CASE-

CEDM - Upper Housing Assembly

• Interpretation

- Residual Stress

• Overlay weld

• Double v-groove weld

- Weld pass

>> jacketed

- Temperature

• ~505ºF/263ºC

- FCS experience

- ~50 ºF delta

CEDM - Upper Housing Assembly

• Circumferential Driver

CEDM - Upper Housing Assembly

• Longitudinal Driver

CEDM - Upper Housing Assembly

• Through-Wall Affect

CEDM - Upper Housing Assembly

• Longitudinal Driver

CEDM - Upper Housing Assembly

• Circumferential Driver

CEDM - Upper Housing Assembly

• Temperature Relationship

CEDM - Upper Housing Assembly

• Interpretation

- Residual Stress

• Overlay weld

• Double v-groove weld

- Weld pass

>> jacketed

- Temperature

• ~505ºF/263ºC

- FCS experience

- ~50 ºF delta

• Medium/Low Susceptibility

Bob Lisowyj - Senior Nuclear Design Engineer CEDM Housing Materials Characterization Discussion

Program Plan

• Predictive

- Crack Model

- Environmental Model

• Plan

- Inspection Criteria

- Remediation

- Repair INNOVATIVE-

Predictive Crack Model

• Palisades and FCS Weibull Curves

- Material difference Type 304 versus Type 347

• FCS Upper Housing Beachmarks

- 10 yrs incubation & 7 yrs cracking FCS TGSCC Projections

• -ANALYTICAL ASSESSMENT-Crack Depth (inches) 0.80 0.60 0.40 0.20 0.00 0 5 10 15 20 25 30 35 Years of Operation (yrs.)

FCS1990 Upper Housing (Actual)

Palisades 1999 Seal Housing (Actual)

Palisades Seal Housing (Positive Indications Projected)

FCS Weld Overlay Failure

FCS 1999 RFO Signature

• CEDM Seal Housing RC-10-27 ECT Signature ECT Reported 160 140

- Six of Eight Inspected 120 100

- Permeability Change 80 Vert (ECU) 60

• FCS and Palisades 40 20

- Similar 0 1

26

• Geometry 51 76 101

• Signatures 126 151

• Assessment Circumferential (degrees) 176 201 Depth

- Possible SCC History

• -INSPECTION DATA-

ECT Inspection Results

• Palisades ECT sample

- Positive Signatures

• Cracks

• Permeability Areas

• FCS 1999 ECT examination

- Positive Signatures

• Permeability Areas

ECT Inspection Results

• -Palisades-

ECT Inspection Results

• -FCSs Difference-

ECT Inspection Results

• Palisades ECT sample

- Positive Signatures

• Cracks

• Permeability Areas

• FCS 1999 ECT examination

- Positive Signatures

• Permeability Areas

• -QUESTIONING-

Sample

• EPRI assistance

• Validation of ECT technique

• Drive Housing Sleeve preparation for ATEM work

• - CONFIRMATION-Palisades Drive Housing Sleeve

Pacific Northwest Division (Battelle)

• Palisades Sample

- Seal housing

• SA312 F304

- Scanning Electron Microscope

• Transgranular

- Small Branching

• 0.095 deep

- Energy Dispersive Spectroscope

• Cl & S contaminants

• Fe,Cr & Ni oxides

Pacific Northwest Division (Battelle) n Palisades active housing 2/08/02 OPPD Presentation 1

Pacific Northwest Division (Battelle) n Palisades active housing 2/08/02 OPPD Presentation 2

Pacific Northwest Division (Battelle) n SEM/EDS Analyses u Impurities F Na, Al, Si, Ca, K and Cl in spots u Oxides F Si, S and Cl near crack tip n Palisades active housing 2/08/02 OPPD Presentation 3

Pacific Northwest Division (Battelle) n TEM/EDS Analyses u 3 to 5 µm particles identified u Delta ferrite pattern F Observation EDS Analyses: wt.%

Si Cr Mn Fe Ni matrix: 0.6 20.2 2 bal. 9.2 ferrite: 0.5 28.4 1.6 bal. 4.8 n Palisades active housing 011 Plane 2/08/02 OPPD Presentation 4