ML20072P836

Interim Deficiency Rept 82-13 Re Fabrication & Detailing of Structural Steel Connections.Initially Reported on 821115. Undersized Welds Caused by Connection Detailing Errors by Bristol Steel.Ae Investigating/Evaluating Problem

ML20072P836
Person / Time
Site:	Clinton
Issue date:	03/28/1983
From:	Hall D ILLINOIS POWER CO.
To:	James Keppler NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III)
References
10CFR-050.55E, 10CFR-50.55E, 82-13, U-10044, NUDOCS 8304040389
Download: ML20072P836 (6)

Text

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i, 1605-L

.lLLIN0/8 POWER COMPANY U-10044 CLINTON POWER STATION, P.O. BOX 678, CLINTON, ILLINOIS 61727 March 28, 1983 Docket Number 50-461 Mr. James G. Keppler Regional Administrator Region III U.S. Nuclear Regulatory Commission 799 Roosevelt Road Glen Ellyn, Illinois 60137

Subject:

Potential Deficiency 82-13 s

10CFR50.55(e)

Fabrication and Detailing of Structural Steel Connections

Dear Mr. Keppler:

On November 15, 1982, Illinois Power Company notified Mr. F.

Jablonski, NRC Region III, (Ref: IP memorandum Y-12935, 1605-L, dated November 16, 1982) of a potentially reportable deficiency per 10CFR50.55(e) concerning drawing details and fabrication of structural steel connections provided by Bristol Steel and Iron (Structural Steel Fabricator) for use at CPS. This initial notification was followed by one (1) interim report (Ref: IP letter U-10013, D. P. Hall to J. G. Keppler, dated December 20, 1982, 1605-L). Our investigation into this matter continues, and this letter represents an interim report in accordance with j 10CFR50.55(e)(3).

Statement of Potentially Reportable Deficiency As a result of structural steel reinspection efforts con-ducted as part of an Illinois Power Structural Steel Recovery Plan, the adequacy of certain structural steel connections in meeting engineering requirements is questioned. These concerns result from the following conditions:

1. Shop-fabricated fillet welds on the horizontal leg of connection angles (welds between connection angles and beam webs) for certain structural steel beams were found to be undersized. The resulting weld may not be r adequate to support design service loads designated by the Architect / Engineer.

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8304040389 830328 PDR ADDCK 05000461 MAR 3 b30h S PDR

Mr. James G. Kcppler Page 2 March 28, 1983 l

2. Installation and inspection criteria was not provided for minimum length of thread engagement in " drill and tap" structural steel connections detailed by Bristol Steel. Inspection criteria utilized during the inspec-tion of field erected drill and tap connections may not have been adequate to verify adequacy of connections in meeting engineering requirements.

Background / investigation Results CONCERN 1 As part of an Illinois Power Structural Steel Recovery Plan, an overinspection of installed and accepted structural steel was performed by Illinois Power Quality Assurance to assure and demonstrate that previously assembled structural steel met regulatory requirements. As a result of the overinspection effort, two (2) nonconformances were generated (NCR 50,002 and 50,004) which addressed inadequacies in welding performed by Bristol Steel. Of primary concern were certain undersized shop fillet welds on the top horizontal leg of connection angles which attach the angles to the beam webs. In investigating this matter, it was determined that the undersized welds were caused by connection detailing errors by Bristol Steel. Certain connec-tion drawings show coped beam details which have insufficient clearance allowed between the top of the connection angles and the bottom of the cope, to provide the required size fillet weld.

Also, there was a lack of fabrication tolerances for coping beams, which would prevent a cope from being cut excessively deep during fabrication. This lack of tolerance could result in inadequate clearance to provide the required size fillet weld.

Illinois Power's investigation of this concern is continuing in order to determine the scope and significance of the potential l deficiency, and its impact on installed plant structural steel.

A review of shop connection detail drawings was performed by Bristol Steel to tabulate all coped beams, including beams with top and/or bottom copes, calculate the clearance available for performing the top and/or bottom fillet welds, and calculate the capacity of the connection without the top and/or bottom fillet weld for those cases where insufficient clearance existed.

l This review has identified 1957 potentially deficient connections.

Sargent & Lundy (CPS Architect / Engineer) is reviewing and evaluating the tabulation of connections and calculated capacity of the 1957 potentially deficient connections. This review involves a comparison of resultant connection capacities (conservatively assuming no horizontal welds) to the actual service loads imposed on the connections. Of the 1957 total f

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Mr. Jcmes G. Kcppler Page 3 March 28, 1983 connections to be evaluated, 1547 have been evaluated at this time, with 1514 found adequate. Thirty-three (33) connections were found to be of questionable adequacy; however, actual service load calculations are being further refined to determine connection adequacy. The connections may require a field verification to determine the adequacy of the horizontal weld in meeting the requirements of AWS Dl.l. Four-hundred-ten (410) connections remain to be assessed. Upon completion of this assessment, including a field verification of any connections found to be of questionable adequacy, an evaluation can then be made to determine remedial actions necessary for identified hardware / drawing inadequacies, and to determine the safety implications of the potentially reportable deficiency.

CONCERN 2 As part of of an Illinois Power Structural Steel Stop Work 019 Recovery Plan (Phase 2A-1), a reinspection of installed structural steel in five (5) areas of the containment building was performed by Baldwin Associates (IP contractor) Quality Control in order to replace lost documentation in those areas.

During the inspection of certain beam-to-box girder connections utilizing " drill and tap" connections (i.e. structural bolts installed directly into side plates of girders which have been drilled and tapped to receive the bolts) the inspector questioned the applicability of the inspection for thread engagement. This question was raised, as inspection criteria for thread engagement was not provided. Past inspection practices were to "N/A the thread engagement inspection point, to assure that no threads were in the shear plane, and assure that installation torque (as required by the AISC Manual) was met. A review of approved shop drawings for the drill and tap connections was performed, which specify grade, diameter, and number cf bolts required, but did not specify bolt length or installation / inspection criteria for thread engagement. Bolt lists were provided as erection aids by Bristol Steel which specified bolt length, but were found to contain discrepancies; and, as unapproved documents, could not be used by Quality Control for inspection. The facts that the bolt lists were in error and that thread engagement and bolt length were not originally inspected or recorded, indicate that insufficient information exists to assess the adequacy of the installed connections for sufficient thread engagement.

Bristol Steel has subsequently provided, with supporting calculations, the minimum theoretical thread engagement, by bolt grade and diameter, necessary to assure adequate bolt strength.

The calculations have been reviewed by the Architect / Engineer and found to be acceptable. This criteria has been added to Bristol Steel drawing GN-1 for use at CPS.

Mr. Jam 2s G. Keppler Page 4 March 28, 1983 Illinois Power's investigation into this matter has deter-mined that thirty-seven (37) drill and tap connections are potentially affected by this potential deficiency (this number was revised downward from 44 due to connection detail changes from bolted to welded for other reasons). Of these connections, twelve (12) are listed as not complete to current drawings, and conformance will be assured by future installation and inspection to the requirements of drawing GN-1. Completion of these twelve connections cannot proceed at this time due to limitations imposed by Stop Work Order 019.

Of the remaining twenty-five (25) connections, an effort was made to reinspect and determine the as-installed condition of the connections for bolt length, thread engagement, and torque of bolts prior to disassembly and reworking of the connections under partial releases Phase 2A-1 and 2A-2 of Stop Work Order 019.

Although a 100% reinspection of the as-built condition of all bolts and attributes could not be performed due to the con-straints of partial releases Phase 2A-1 and 2A-2, fifteen (15) of the twenty-five (25) connections were inspected for the above attributes prior to reworking, with the remaining ten (10) connections being inspected to some lesser degree. This reinspection effort found bolts on two (2) connections that did not meet the requirements of drawing GN-1. An evaluation of the results of this reinspection effort is presently being performed to determine the significance and reportability of the concerns.

In addition to the drill and tap connections detailed by Bristol Steel, a review was performed to determine if other drill and tap connections exist. The Architect-n.s_.eer, and safety related steel vendors supplying material to CPS were directed to review their drawings to determine if non-standard connections exist that require special installation and inspection criteria.

One (1) expansion connection detail was found that did not quantitatively specify expansion clearance for the bolts in the slotted holes. This situation was corrected by a Field Engineering Change Notice (FECN) 3209. No additional connections, other than the one (1) case above, were identified.

Corrective Action (Interim)

Illinois Power is presently investigating corrective action necessary to prevent recurrences of the problems identified in this investigation. As the receipt of materials from Bristol Steel is complete, and future orders for material have not been placed, nor will future orders be placed with this vendor, future occurrences of an identical nature have been prevented. There-fore, corrective action to prevent recurrence has focused on preventing occurrences of a similar nature as follows:

Mr. Jam:s G. K ppler Page 5 March 28, 1983

1. The scope of Illinois Power Quality Assurance audits will be increased to specifically include Sargent &

Lundy's process of reviewing vendor design drawings to assure that effective reviews are being performed, to minimize vendor design drawing errors.

2. Notification to structural steel vendors performing work or supplying material for Clinton (past and present) was made, advising and stressing that they have responsibility for their work, and review of their design drawings by Sargent & Lundy does not relieve, or minimize that responsibility. This includes correctness of design, execution of work, implementation of QA/QC programs, and reportability in accordance with the Code of Federal Regulations.

3. Enhancements have been made to the Baldwin Associates vendor surveillance program. These enhancements include, but are not limited to, the following:

a. intensified in-shop vendor surveillances in both scope and number.

b. a reevaluation of Baldwin Associates vendor surveillance inspection points was performed, with more hold points established.

c. a reorganization of the vendor surveillance department from the Quality Control to the Quality Assurance Department was made, to increase overall program effectiveness.

Safety Implications / Significance The investigation of this potentially repor'.able deficiency continues, to determine the adequacy of affected structural steel in meeting engineering requirements. Although a positive trend has been identified in the results of investigation thus far, l further engineering assessment and reinspection of the as-built hardware is required, including an evaluation of the impact of any identified deficiencies on plant performance. It is anticipated that approximately ninety (90) days will be necessary to complete the investigation, determine reportability, and to file a final report on this potentially reportable deficiency.

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Mr. Jam:s G. Koppler Page 6 March 28, 1983 We trust that this interim letter provides you sufficient background information to perform a general assessment of this potential reportable deficiency and overall approach to resolu-tion of the problem, cere y yours,

. . Hall Vice President REC /ph cc: H. H. Livermore, NRC Resident Inspector Director, Office of I&E, Washing, D.C. 20555 i Illinois Department of Nuclear Safety Manager-Quality. Assurance INPO Records Center, j

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