ML17180B006

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Summary of 941014 Meeting W/Util Re Response to GL-94-03, Intergranular Stress Corrosion Cracking of Core Shrouds in BWR, for Plants.List of Attendees Encl
ML17180B006
Person / Time
Site: Dresden, Quad Cities  Constellation icon.png
Issue date: 11/07/1994
From: Stang J
Office of Nuclear Reactor Regulation
To:
Office of Nuclear Reactor Regulation
References
GL-94-03, GL-94-3, NUDOCS 9411100244
Download: ML17180B006 (38)
v • d • e


Text

UNITED STATES NUCLEAR REGULATORY COMMISSION Docket Nos. 50-237, 50-249 and 50-254, 50-265 WASHINGTON, D.C. 20555-0001 November 7, 1994 LICENSEE:

Commonwealth Edison Company (ComEd)

FACILITIES:

Dresden, Units 2 and 3, and Quad Cities, Units 1 and 2

SUBJECT:

MEETING

SUMMARY

OF OCTOBER 14, 1994 On October 14, 1994, in a public meeting, the NRC staff met with representatives from ComEd to discuss their response to Generic Letter (GL) 94-03, "Intergranular Stress Corrosion Cracking of Core Shrouds in Boiling Water Reactors" for Dresden, Unit 2, and Quad Cities, Unit 2.

ComEd also updated the NRC staff on the status of the additional information they were preparing in response to the NRC staff safety evaluation issued on July 21, 1994, concerning the degraded core shrouds in Dresden, Unit 3, and Quad Cities, Unit 1. A list of attendees is enclosed (Enclosure 1).

ComEd made a presentation to the staff providing their basis for believing that there will be no existing through-wall cracks in the core shrouds at Dresden, Unit 2, and Quad Cities, Unit 2 for the remainder of their current operating cycles. These units have not had their core shrouds inspected for cracking and have approximately 6 months of operation each left on their existing fuel cycles until the units shut down for a refueling outage and inspection of the core shrouds.

ComEd also presented their safety assessment of the consequences of through-wall cracking of the core shrouds following design basis and beyond design basis events. is a copy of ComEd's handout.

During the meeting the NRC staff raised a number of questions that ComEd could not fully answer.

In the meeting, the NRC staff indicated that all the requests for additional information would be formalized and forwarded to the licensee.

ComEd also briefed the staff on the progress they have made on the responses for addition information requested by the NRC staff contained in the NRC safety evaluation dated July 21, 1994.

The July 21, 1994, safety evaluation requested that all information be provided by December 15, 1994.

ComEd indicated that they were making good progress in the resolution of issues and may be able to provide the staff with all the required information prior to December 15, 1994.

  • In the meeting, ComEd also presented the preliminary design modification to fix the core shrouds at Dresden and Quad Cities. Enclosure 3 is a picture of the proposed design.

ComEd indicated in the meeting that an evaluation concerning the repair modification would be provided to the staff for review.

Enclosures:

1.

List of Attendees

2.

Licensee's Handout

3. Proposed Design cc w/encls:

see next page DISTRIBUTION (w/all encl):

Docket File PUBLIC PDII 1-2 R/F (2)

Original signed by John F. Stang, Project Manager Project Directorate 111-2 Division of Reactor Projects III/IV Office of Nuclear Reactor Regulation J~ Strasma J. Stang P. Hiland, Riii DISTRIBUTION (w/encl.

R. Pulsifer 1 only) M. Mi tche 11 Wessman Hermann Cubbage Kavanagh Patnaik Strosnider Hackett Lainas W. Russell/F. Miraglia R. Zimmerman J. Roe R. Capra G. Holahan C. Moore B. Grfmes, D:LORS A. Chaffee, OEAB OGC E. Jordan, D:AEOD R. Spessard, D:DRIL ACRS (4)

OPA B. McCabe E. Greenman R.

R.

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P.

J.

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B.

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Mi 11 er Rubin Thadani Sheron Jones McNeil Staudenmeier DOCUMENT NAME: DRESDEN\\COMED.M1 b

"C" = Copy without enclosures-,,E" = Copy with enclosures "N" = No copy OFFICE PD:PDIIl-2

==;::1=:::;i NAME DATE 10/ /94 10/ /94

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Commonwealth Edison Company cc:

Michael I. Miller, Esquire Sidley and Austin One First National Plaza Chicago, Illinois 60690 Mr. J. Stephen Perry Site Vice President Dresden Nuclear Power Station 6500 North Dresden Road Morris, Illinois 60450-9765 Mr. J. Eenigenburg Station Manager, Unit 2 Dresden Nuclear Power Station 6500 North Dresden Road Morris, Illinois 60450-9765 Mr. D. Bax Station Manager, Unit 3

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Dresden Nuclear Power Station 6500 North Dresden Road Morris, Illinois 60450-9765 U.S. Nuclear Regulatory Commission Resident Inspectors Office Dresden Station 6500 North Dresden Road Morris, Illinois 60450-9766 Regional Administrator U.S. NRC, Region III 801 Warrenville Road Lisle, Illinois 60532-4351 Illinois Department of Nuclear Safety Office of Nuclear Facility Safety 1035 Outer Park Drive Springfield, Illinois 62704 Chairman Grundy County Board Administration Building 1320 Union Street Morris, Illinois 60450 Dresden Nuclear Power Station Unit Nos. 2 and 3 Mr. D. L. Farrar Manager, Nuclear Regulatory Services Commonwealth Edison Company Executive Towers West III, Suite 500 1400 OPUS Place Downers Grove, Illinois 60515 John Wil 1 is Coordinator, Nuclear Campaign Greenpeace International 1436 U Street, N.W.

Washington, D.C.

20009

Commonwealth Edison Company cc:

Mr. Stephen E. Shelton Vice President Iowa-Illinois Gas and Electric Company P. 0. Box 4350 Davenport, Iowa 52808 Michael I. Miller, Esquire Sidley and Austin One First National Plaza Chicago, Illinois 60690 Mr. Guy Campbell Station Manager Quad Cities Nuclear Power Station 22710 206th Avenue North Cordova, Illinois 61242 Quad Cities Resident Inspectors Office U.S. Nuclear Regulatory Commission 22712 206th Avenue North Cordova, Illinois 61242 Chairman Rock Island County Board of Supervisors 1504 3rd Avenue Rock Island County Office Bldg.

Rock Island, Illinois 61201 Illinois Department of Nuclear Safety Office of Nuclear Facility Safety 1035 Outer Park Drive Springfield, Illinois 62704 Regional Administrator U.S. NRC, Region III 801 Warrenville Road Lisle, Illinois 60532-4351 Quad Cities Nuclear Power Station Unit Nos. 1 and 2

LIST OF ATTENDEES for October 14. 1994 Meeting NRC Mark Rubin Gary Holahan Jack Roe Ashok Thadani Brian Sheron Robert Jones Robert Capra Michael McNeil Jack Strosnider Robert Pulsifer R. H. Wessman John Stang Matthew Mitchell Robert Hermann Amy Cubbage Kerri Kavanagh P. Patnaik Joeseph Staudenmeier Mary Miller Ed Hackett Gus Lainas Com Ed John Purkis Joe Wil 1 i ams Tom Spry John Hosmer Tom Behringer Mark Uhrich Gerald Whitman Pete Piet Dennis Farrar Niagara Mohawk W. David Baker GE Hwang Choe

Dresden/Quad Cities Unit 2 I

Core Shroud Meeting October 14, 1994 rn

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Agenda Background/History John Hosmer Plant Status John Hosmer Basis for No Existing Tom Spry Through-Wall Cracking Safety Assessment of Assumed Joe Williams Through-Wall Cracking Status of Open Issues Jack Purkis Conclusion/Discussion John Hosmer ComEd

CornEd Representation Jerry Whitman Vessel Internals Program Engineer Plant Support Mark Uhrich Lead Mechanical Engineer Dennis Farrar Regulatory Services Manager Nuclear Pete Piet Licensing Administrator Hwang Choe GE Principal Engineer Tom Behringer ComEd Structural Consultant ComEd

Background/History

  • 7 /21 - N RC Safety Evaluation Report
  • Permits 1 5 months operation for Dresden 3 & Quad Cities 1
  • ComEd Additional Work
  • UT Accuracy
  • Asymetric & other load validation (TRACG)
  • Support BWR-VIP Initiative
  • Dresden/Quad Cities (D/QC) Unit 2 response-relative to H2/H3
  • 10/4 - NRC Conference call on Dresden/Quad Cities Unit 2
  • 10/7 - Com Ed response to 9/27 RAI
  • 10/1.3 - Supplement to Com Ed RAI Response ComEd

. Unit

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Dresden Unit 2 Dresden Unit 3 Quad Unit 2 Quad Unit 1 ComEd Plant Status Sch~ S/U NeXt Scheduled..

Refueling Ot.ibig~.

10/31 /94 3/95 10/15/94 3/96 November 1994 1 /95 November 1994 9/95

. Inspection Status

'95 Outage, Vertical Welds Needed for Shroud Repair Baseline Done, Planning Shroud Repair

'95 Outage, Vertical Welds Needed for Shroud Repair Baseline Done, Planning Shroud Repair

.... I i

Basis for No Through-Wall Cracking Tom Spry ComEd

Basis for Postulating No Existing Through-Wall Cracks S.ummary of Crack Size Estimation

  • Uninspected units (02, Q2) bounded by inspected units (03,01)
  • Crack depth estimates for 02 and 02 show large structural margins ComEd

Dresden 2 and Quad Cities 2 **

I Crack Growth Considerations *

  • Operating time and early conductivity I -
  • Hydrogen Water Chemistry (HWC)
  • PLEDGE model crack growth rates ComEd

Dresden 2 Operating Time and Conductivity

  • Correlation between (early conductivity x operating time) and extent of shroud cracking

- 02 has 2 more years than 03

- 02 early conductivity better than 03

  • Good early conductivity at 02 offsets higher operating time ComEd

Worst Plant Cracking vs. Conductivity x On Line Years

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High (100" - 200")

Dresden 2 =

5.1 2 -----------------... --------------------------------------- -- -----------------------------* ------*

Med ( 30 'to 100")

1 ----------------------------------*- -* --------------------- ----------------------------------

Low ( < 30")

Dresden 3/ Quad 1 0

r-1 LO L-L o 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 5.5 6 _6.5 7 7.5 8 Conductivity x On Line years o Welded Plate A Forged Rings

  • Plate Material Unknown
  • Dresden 2
  • Ouad 2
  • Quad 1 on line years were incorrectly reflected in "BWR Shroud Cracking Generic Safety Assessment", Rev. 1. The correct value of on line years is15.4.

ComEd

Dresden 2 HWC

  • 02 operating with HWC since 1983
  • Resulting crack growth rate lower in 02
  • Other RPV internals reflect less agressive 02 environment ComEd

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RPV Internals IGSCC Event Comparison Dresden Unit 2 & 3 lnsjjeotlon Uh it 2 j

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Jet Pump Beams 2

12 3

Jet Pump Riser Braces 0 (Note 1 )

3 In Shroud Head Bolts 1

30 Shroud Access Hole 0

0 Covers Core Spray 0 (Note 1 )

2 Sparger/Piping Core SRM/IRM Tubes 1

1 Top Guide Bolts 0 (Note 1 )

3

  • Total 4

51 Note 1 - Previous inspections may not have been performed at the sensitivity used to detect the cracking at Unit 3.

ComEd

Dresden 2 PLEDGE Model Crack Growth Rates

  • 02 crack, growth rate 1 /30 of 03

- H3/H5 ECP differential taken into account

  • Current D2 bounding crack depth 0.64"

-Assume initiation at 3 EFPY and 1.25 ppm HWC beginning in 1 983

-Compare with 1.30" crack depth for D3 using SER methodology

  • 02 margin factor currently > 65 based on MS LOCA +

DBE, no credit for fillet ComEd

Quad Cities 2 Operating Time and ConQuctivity

  • Q~ (early conductivity x operating time) < Q 1

- 02 operating years 0.6 less than 01

- Q 1 and 02 early conductivity nearly equal

  • 02 cracking no worse than 01 ComEd

Quad Cities 2 HWC

  • Q 1 and 02 HWC history nearly equal -

ComEd

Quad Cities 2 PLEDGE Model Crack Growth Rates

  • Crack growth rate based on non-HWC ECP
  • 02 crack depth bounded by 1.30" of 01 based on SER methodology
  • 02 m~rgin factor currently > 21 based on MS LOCA +

DBE, no credit for fillet weld ComEd

Basis for Postulating No Existing Through-Wall Cracks I

S.ummary of Crack Size Estimation

  • Uninspected units (02, 02) bounded by inspected units (03,01)

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  • Crack depth estimates *for 02 and Q2 show large e

structural margins ComEd

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Safety Assessment of Assumed

  • Through-Wall Cracking Joe Williams ComEd

Safety Assessment Postulated Through-wall Failures of Shroud Ring Welds H2, H3, I

or H 5 at Dresden 2/0uad 2

  • Design Basis Events Considered

- Normal Operation

- Operation Transients

- Design Basis Earthquake (DBE)

- Design Basis Main Steam Line Break (MSLB)

- Design Basis Recirculation Line Break (RLB)

ComEd

Safety Assessment (Cont.)

  • Event Load Definition

- Seismic Events

- Quad Plant-Specific Seismic Model (Dresden Model in progress)

- Housner Synthetic Time History Produced and used for input to both Dresden/Quad ComEd

- Housner displacements bound Golden Gate and El Centro Displacements for Through-wall failure

Safety Assessment (Cont.)

  • Main Steam Line Break
9

- Previous Load Definition 12 psid @ Dresden & 20 psid @

Quad (LAMB Code)

- TRACG model results for 6 units correlated to MSL ID vs.

RPV ID. Results indicate 14 psid value for Dresden/Quad

- Plant-specific Dresden/Quad TRACG model is in progress ComEd I

Shroud Head dP due to MSLB dP (Psid) 20--~~~~~~~~~~~~~~~~~~~~__,

1 g. -------------___________ Quad_ Citi_es ___________________________________________________ *--*--~

18. ------------------------~~~-~~-~~ -----------------------------------------*- -----

17 ----------------------------------------------------------------------

~ :. : : : : : : : : : : : : : : : : : : : : : : : : : : : : i::::::::::::: _ --------: : : : _ ---------=- ---------....:.Ii--~~...............-

14 13 11 ---------------------------------

10'--~~~~~~~~~~~~~~~~~~~~~_.

0.05 0.06 0.07 0.08 0.09 0.1 0.11 0.12 Ratio MSL l.D./RPV l.D.

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  • Data Points -upper Bound *Lower Bound
  • Dresden/Quad I ComEd

Safety Assessment (Cont.)

  • Recirculation Line Break

- Previous UFSAR generic loads - 17 kips max. blowdown load above HS and 225 kips peak acoustic load applied uniformly (WHAM Code).

- Plant specific TRACG Model developed and validated: 15 axial levels, 14 azimuthal sectors and 2 rings: validated by sensitivity studies, experimental results, and by BWR-VIP

Safety Assessment (Cont.)

Recirculation Line Break, (Cont.}

  • Peak Acoustic load converted into static equivalent load per BWR-VIP
  • Revised plant-specific peak blowdown load - 67 kips above H5
  • Results

- H2 and H3 results finalized in RAI response, preliminary H5 results ComEd

MAINTAINED Normal 2 611 AT QC Ha NO LATERAL NO LATERAL BY INTACT MAINTAINED 511 AT QC H2 Operation DISPLACEMENT DISPLACEMENT RCPB AND SHROUD RODS INSERT MAINTAINED INAN LESS THAN 0.05 11 INJECTION INSIDE DBE 3.6"ATQCH3 OSCILLATORY FORD/QC BY INTACT MAINTAINED RPVANNULUS RCPB PATTERN 10.1 11 AT D/QC NO LATERAL ZERO MAINTAINED INJECTION INSIDE MSLB BY INTACT MAINTAINED H3 DISPLACEMENT DISPLACEMENT RCPB RPVANNULUS FORD/QCH5, e

MAXIMUM 1/4 11 NOT RRLB 2.6"atQC H3 LESS THAN 1 11 NO LATERAL OPENING ALL DESIGNED TO FOR QC H21 5 11 FORD/QCH5 DISPLACEMENT

AROUND, FUNCTION IN SHROUD LIFT ACCEPTABLE RRLB BYPASS FLOW ComEd

Safety Assessment Conclusion

  • Summary

- Defined Specific Sucess Criteria for the D/QC Safety Functions

- Analyzed Shroud Behavior

- Compared Results with Criteria

  • Conclusion

- With postulated through-wall failure at H2, H3, or H5 safe shutdown will still be. achieved for all design basis events.

Status of Open Issues Jack Purkis ComEd

~

Status of Open Issues

  • Inspection Capabilities
  • Current Modification Status ComEd

Inspection Capabilities

  • GE UT and vr Equipment committed through mid-November
  • ComEd visual Capabilities (no UT available)

- 3 IWI Inspectors Qualified per BWR-VIP

- IWI Equipment available

- Refuel bridges being replaced at Dresden - not available until 12/94 ComEd

Current Modification Status

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Quad 2 Completed 1 0/1 7/94 1 0/6 1 2/31 /94 Complete Dresden 2 In Progress 1 1 17194 1 0127 1 /23/95 ComEd I

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i Conclusion John Hosmer ComEd

Conclusion

  • Uninspected Units Bounded: No Through-Wall Cracking for Q2/D2
  • Safety Assessment

- Acceptance Criteria Established

- Weld Specific Analysis Complete

- All Safety Functions Met

  • Remaining ComEd Actions

- MSLB TRACG

- Finalize HS Displacements

- Dresden Seismic Model ComEd 11/15/94 12/15/94 10/30/94 n.*,

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10/11194 e

QUAD CITIES 2

  • _____ GE Nuclear Energy CORE SHROUD MODIFICATION PRELIMINARY DESIGN
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