ML20079S137
| ML20079S137 | |
| Person / Time | |
|---|---|
| Site: | Clinton  |
| Issue date: | 07/05/1983 |
| 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 8307110322 | |
| Download: ML20079S137 (5) | |
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/LLINDIS POWER 00MPANY fp y.3nggg CLINTON POWER STATION. P.O. Dolt 678. CLINTON, ILLINOIS 61727 l
July 5, 1983 Docket Number 50-461 Mr. James G. Keppler Regional Ad,ministrator Region III U.S. Nuclear Regulatory Commission 799 Roosevelt Road Glen Ellyn, Illinois 60137
Subject:
10CFR50.55(e) Deficiency 82-13 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 two (2) interim reports (Ref:
IP letter U-10013, D. P. Hall to J. G. Keppler, dated December 20, 1982, 1605-L, and IP letter U-10044, D. P. Hall to J. G. Keppler, dated March 28, 1983, 1605-L).
Our investigation is complete, and this letter represents a final report in accordance with 10CFR50.55(e)(3) on this reportable deficiency.
Statement af Reportable Deficiency 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 on certain of these beams is not adequate to support design service loads designated by the Architect / Engineer.
1 2.
Installation and inspection criteria was not provided for minimum length of thread engagement in " drill and h 7
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Mr. James G. Keppler Page 2 tap" structural steel connections detailed by Bristol Steel.
Inspection criteria utilized during the inspection of field erected drill and tap connections was not sufficient to assure the adequacy of con-nections 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, two (2) nonconformances were generated (NCR 50,002 and 50,004) which addressed inad-equacies in welding performed by Bristol Steel.
Of concern were certain undersized shop fillet welds on the top horizontal leg of connection angles which attach the angles to the beam webs.
Investigation of this matter found that the undersized welds were caused by connection detailing errors by Bristol Steel.
Certain connection drawings show coped beam details which have insuffi-cient cicarance 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 exccc-sively deep during f_ rication.
This lack of tolerance coulit result in inadequate clearance to provide the required size fillet weld.
A review of shop connection detail drawings was performed by Bristol Steel and a tabulation of coped beams was prepared.
This tabulation included the calculated clearance available for performing the horizontal fillet welds and the calculated capacity of the connections without the horizontal fillet welds for those cases where insufficient clearance existed.
This review identified 2016 potentially deficient connections.
Sargent & Lundy reviewed the calculated capacity of the potentially deficient connections.
This review involved a comparison of resultant connection capacity (conservatively assuming no horizontal welds) to the actual service loads imposed on the connections.
It was determined that 1996 connections were adequate discounting the horizontal welds, but found that twenty (20) connections required the subject welds.
A field verification of the twenty (20) connections found that two (2) connections are of questionable adequacy due to the use of a weld detail considered inappropriate for the application.
Further review of these two questionable connections found that extensive engineering evaluation and load testing would be necessary to determine the acceptability of the beams in the as-welded condition.
t Mr. James G. Keppler Page 3 CONCERN 2 As part of an Illinois Power Structural Steel Recovery Plan (Phase 2A-1), a reinspection of installed structural steel in five (5) areas of the containment building was performed by Baldwin Associates Quality Control.
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 an inspection for thread engagement, as inspection criteria for thread engagement in this configuation was not provided.
Past inspection practices were to "N/A" the thread engagement inspection point, 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 of 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 fact that the bolt lists were in error and that thread engagement -and bolt length were not originally inspected or recorded, indicated that insufficient information existed 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.
Illinois Power's investigation into this matter has deter-mined that thirty-seven (37) drill and tap connections could be affected by this problem.
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.
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 Phase 2A-2 of the Recovery Plan.
Although a 100% reinspection of the ab-built condition of all bolts and attributes could not be performed (due to previous work on nine (9) connections as part of Phase 2A-1), sixteen'(16) connections were reinspected for the above attributes. prior to rewo'rking, with the nine (9) connections being reinspected to some lesser degree.
This rein-spection found bolts on two (2) connections that did not meet the requirements of drawing GN-1 for thread engagement.
An engineering, assessment of the situation was performed, but could
h Mr. Jcmes G. Keppler -
Page-4 not conclusively determine that the connections would not have failed.
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-Engineer and structural steel vendors supplying safety related 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 were identified, i
Corrective Action The following actions have been, or will be taken to correct identified problems and to prevent recurrence:
Concern 1 1.
The two questionable connections (5-10B4 (marked end) and 5-15B7 (unmarked end)) will-be repaired.
S&L design drawings have been issued to provide the field with design information to perform this' work.
7 2.
Bristol Steel is revising their shop drawing Gh-1 to clarify the requirements for the horizontal welds on coped structural steel members.
Concern 2 3.
Bristol Steel shop drawing GN-1 has been' revised to provide criteria for thread engagement necessary to assure adequate bolt strength, i
4.
The twenty-five connections affected by this problem and completed to-date have been reworked in accordance -
with the new criteria provided in drawing GN-1.
Generic Action 5.
Receipt of materials-from Bristol.Steellis complete.
Orders for additional ~ materials-have not been placed, H,,
nor will future orders be'placed with this vendor.-
i 6.
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.
7..
Notification to structural steel vendors performing work or supplying _ material for'Clinton (past and i
p.,
- r. Jcmss G. Keppler-Page 5 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 correct-ness of design, execution of work, implementation of QA/QC programs, and reportability in accordance with the Code of Federal Regulations.
8.
' Enhancements have been made to the Baldwin Associates vendortsurveillance program.'
These enhancements include, but are not ifmited 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-Investigation of this reportable deficiency determined tEiE"
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the adequacy of certain structural steel connections supporting safety related structural members could'not conclusively be determined without extensive engineering evaluation and testing.
It may be postulated that (without further evaluation) the questionable beams may have failed at the connections and resulted.in degradation of structural support of; safety-related buildings and components at CPS, which could adversely affect the safe operation of the facility.
On this basis,'this condition is considered significant, and reportable as a deficiency in con-i.
struction in accordance with 10CFR50.55(e).
S We trust that this-final letter provides you sufficient information to perform an assessment of this reportable deficiency and adeqtfately describes ~our. overall approacte
- o resolve the problen.
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S rel
- yours, f
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y D.
. Hall 3p [3 s.
Vice President.
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~cc:
-H. H. Livermore,.NRC Resident-Inspector-
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, Director, Office-of I&E, Washing, D.C.'20555 i
' Illinois Department of' Nuclear Safety.
' Manager-Quality. Assurance
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