ML17180A724

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Forwards RAI Concerning Core Shroud Cracking at Plant
ML17180A724
Person / Time
Site: Dresden, Quad Cities  
Issue date: 05/06/1994
From: Stang J
Office of Nuclear Reactor Regulation
To: Farrar D
COMMONWEALTH EDISON CO.
References
NUDOCS 9405120096
Download: ML17180A724 (5)
v • d • e


Text

May 6, 1994 Docket Nos. 50-237, 50-249, and 50-254, 50-265 DISTRIBUTION Docket File PDIII-2 r/f JZwolinski JStang NRG & Local PDRs JRoe OFC NAME DATE COPY Mr. D. L. Farrar Manager, Nuclear Regulatory Services Commonwealth Edison Company Executive Towers West III, Suite 500 1400 OPUS Place Downers Grove, Illinois 60515

Dear Mr. Farrar:

CH awes ACRS{lO)

JDyer CPatel OGG BCl.ayton, RIII

SUBJECT:

REQUEST FOR ADDITIONAL INFORMATION CONCERNING CORE SHROUD CRACKING AT DRESDEN, UNITS 2 AND 3, AND QUAD CITIES, UNITS 1 AND 2 As a followup to the telephone conversation on May 5, 1994, between the NRG staff and Commonwealth Edison staff concerning the cracking of the core shrouds at the Dresden and Quad Cities Station, please provide answers to the enclosed questions concerning core shroud cracking.

You should be prepared to address the.plant-specific questions by May 23, 1994.

This schedule is based on a meeting to discuss resolution of the shroud cracking, tentatively scheduled for the week of May 23, 1994.

Please provide a response in writing to all questions within 30 days following receipt of this letter. Additional generic questions concerning core shroud cracking will be sent to you under a separate cover.

If you have any questions concerning this action, please contact me at {301) 504-1345.

Enclosure:

As stated cc w/enclosure:

See next age 9405120096~40506-- -~~,

PDR ADOCK 05000237 P.

PDR 100052 Sincerely, Original Signed BY. J. Dyer for John F. Stang, Project ~anager Project Directorate III-2 Division of Reactor Projects III/IV Office of Nuclear Reactor Regulation YES/NO 110\\11

Mr. D. L. Farrar Commonwealth Edison Company cc:

Michael I. Miller, Esquire Sidley and Austin One First National Plaza Chicago, Illinois 60690 Mr. G. Spedl Plant Manager 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 Chairman Board of Supervisors of Grundy County Grundy County Courthouse Morris, Illinois 60450 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 Dresden Nuclear Power Station Unit Nos. 2 and 3

Mr. D. L. Farrar 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, Jlilinois 60690 Mr. Richard Sax Station Manager Quad Cities Nuclear Power Station 22710 206th Avenue North Cordova, Illinois 61242 Resident Inspector U. S. Nuclear Regulatory Commission 22712 206th Avenue North

.Cordova~ Illinois 61242 C!t:raiinnan Rock Island County Board of Supervisors 1504 3rd Avenue Rock Island: County Office Bldg.

Roc'k Islandi, Illinois 61201

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Quad Cities Nuclear Power Station Unit Nos. 1 and 2

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REQUEST FOR ADDITIONAL INFORMATION CONCERNING CORE SHROUD CRACKING AT DRESDEN. UNITS 2 AND 3, AND QUAD CITIES. UNITS l AND 2 DOCKET NOS. 50-237, 50-249, 50-254, AND 50-265 ENCLOSURE Plant-Specific Questions Regarding Dresden Unit 3 and Quad Cities Unit 1 I.

Describe the methods, scope, and results of the inspections that have been performed at Dresden 3 and Quad Cities I. Include in this discussion the types of inspections performed {e.g. visual, ultrasonic) and the lengths and depths {where characterized) of the detected indications.

2.

Provide information on the qualification and expected reliability of the testing methods used {e.g. visual, ultrasonic). Describe qualifications that have been performed on mock-ups including the configurations of the mock-ups and their applicability to the crack locations in the Dresden and Quad Cities core shrouds. Describe any limitations in the locations that can be inspected and for the ultrasonic testing technique describe any limitations in quantifying crack depths.

3.

Provide results of the fracture mechanics evaluations of the detected cracks including calculated margins to failure and the sensitivity of these margins to nondestructive testing uncertainty and assumed crack growth rates.

4.

Discuss how bypass leakage through the shroud at various elevations can be detected and responded to during normal operating conditions.

Discuss the adequacy of plant operating procedures and operator training with regard to the above.

5.

Evaluate the safety significance of a 360° through wall failure at the HS weld location in the core shroud during:

{a) normal operation; {b) anticipated transients; and {c) postulated accident conditions.

Include evaluation of the design basis loss-of-coolant accident combined with safe-shutdown earthquake loa~s {LOCA +SSE). This evaluation should address question~ such as:

(a) estimated potential shroud movement vertically or laterally; (b) control rod scram capability; (c) boron injection capability; (d) short & long term core cooling capability, including core spray capability; and {e) ability to maintain 2/3 core coverage with bypass leakage at various elevations.

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I* 6.

Describe the methods, scope, and results of inspections conducted on reactor vessel internal components other than the core shroud. Discuss the safety significance of any indications found in these components and how these indications were dispositioned.

7.

Identify reactor vessel internal components or portions of those components that were not or cannot be inspected and have potential safety significance. Discuss the potential consequences of cracking in these locations. Discuss plans for developing inspection methods and repairs for these components.

8.

Describe repair options for cracks at various locations in the core shroud.

Include discussion of actions to achieve ALARA personnel exposure and provide estimates of exposure levels associated with each repair option.

Plant-Specific Questions Regarding Dresden Unit 2 and Quad Cities Unit 2

1.

Discuss the scope and results of any prior core shroud or other vessel internals inspections conducted at these units.

2.

Identify any differences between these units and Dresden Unit 3 and Quad Cities Unit 1 with regard to core shroud geometry, materials, fabrication methods, operating times, water chemistry or other factors affecting susceptibility to cracking.

3.

Discuss existing procedures and operator training for monitoring for core shroud bypass flow or other indications of vessel internals failures.

4.

Provide an evaluation of the safety significance of a 360° through wall failure at each weld location in the core shroud during normal operation, anticipated transient, and postulated accident conditions.

Include evaluation of the design basis loss-of-coolant accident combined with safe-shutdown earthquake loads (LOCA +SSE}.

This evaluation should address questions such as:

(a} estimated potential shroud movement vertically or laterally; (b) control rod scram capability; (c) boron injection capability; (d) short & long term core cooling capability, including core spray capability; and (e) ability to maintain 2/3 core coverage with bypass leakage at various elevations.

5.

Discuss the adequacy of emergency procedures an.c! _operator training wjth regard to design basis accident conditions wit~*~ostulated core shroud failure and by-pass :':l~~*

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