ML20126K347
| ML20126K347 | |
| Person / Time | |
|---|---|
| Site: | Harris  |
| Issue date: | 03/29/1985 |
| From: | Parsons R CAROLINA POWER & LIGHT CO. |
| To: | Grace J NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II) |
| References | |
| CON-NRC-345 92, NUDOCS 8506100879 | |
| Download: ML20126K347 (4) | |
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ce Cp&L Carohna Power & L6ght Company 35 f#o.4 ?ili;, del Hill, N.C. 27562 ao March 29,1985 Dr. J. Nelson Grace NRC-345 United States Nuclear Regulatory Commission Region 11 101 Marietta Street, Northwest (Suite 2900)
Atlanta, Georgia 30323 CAROLINA POWER & LIGHT COMPANY SHEARON HARRIS NUCLEAR POWER PLANT 1986 - 900,000 KW - UNIT 1 BOLTED STRUCTURAL CONNECTIONS WITH EXCESSIVE GAPS AND ASTM A325 NUTS ON ASTM A490 BOLTS, ITEM 92
Dear Dr. Grace:
Attached is our fifth interim report on the subject item which was deemed reportable per the provisions of 10CFR50.55(e), on April 26,1983. CP&L is pursuing this matter, and it is currently projected that corrective action and submission of the final report will be accomplished by May 10,1985.
Thank you for your consideration in this matter.
Yours very truly, 999 kr: ;;*
R. M. Parsons Project General Manager Completion Assurance Shearon liarris Nuclear Power Plant RMP/bs Attachment cca Messrs. G. Maxwell /R. Prevatte (NRC-SilNPP)
Mr. R. C. DeYoung (NRC)
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CAROLINA POWER & LIGHT COMPANY SHEARON HARRIS NUCLEAR POWER PLANT UNIT NO.1 FIFTH INTERIM REPORT BOLTED STRUCTURAL CONNECTIONS WITH EXCESSIVE GAPS AND ASTM A325 NUTS ON ASTM A490 BOLTS ITEM 92 March 29,1985 REPORTABLE UNDER 10CFR50.55(e)
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SUBJECT:
Shearon Harris Nuclear Power Plant / Unit No.1,10CFR50.55(e),
reportable deficiency, Bolted Connections with Excessive Gaps and ASTM A325 Nuts on ASTM A490 Bolts.
ITEM:
Bolted structural steel connections in the Unit No.1 Turbine and Containment Buildings have gaps, or areas with 0% contact between mating surfaces in friction connections. The part of this problem concerning the use of A325 nuts on A490 bolts was previously found to be non-reportable and so reported on November 30,1982 (CP&L letter NRC-26).
SUPPLIED BY:
Not a supplier-related deficier :y. Structural connections concerned were field assembled.
NATURE OF DEFICIENCY:
The Turbine Building is seismically designed per Regulatory Guide 1.29, and the Containment Building is a Seismic Class I structure.
These structural connections were designed as friction type connections requiring solid seating of the mating surfaces.
These connections were previously inspected and accepted.
DATE PROBLEM OCCURRED:
June 22,1982 DATE PROBLEM REPORTED:
On July 2,1982, CP&L (L. E. Jones) notified the NRC (Mr. A.
Hardin) that the item was potentially reportable. On April 26, 1983, CP&L (N. 3. Chiangi) notified the NRC (Mr. A.
Hardin) that this item was reportable per the provisions of 10CFR50.55(e).
SCOPE OF PROBLEM:
A reinspection of the Turbine and Containment Buildings, including structural connections where there was a potential for these gaps occurring, has been completed.
An engineering evaluation had determined that the gaps would not occur in connections with beam end clips or plates less than 5/8" thick.
In standard design, these clips deflect slightly under bolt tension to make contact with the adjacent mating surface.
Main support girder end clips were generally fabricated from 1" thick angle, and end plate thicknesses in some members exceeded 2".
A total of approximately 878 connections were reinspected in the Turbine Building and approximately 500 in the Containment, with gaps being found in approximately 154 and approximately 36, respectively. Additional connections in the Turbine Building with gaps have been identified in inspections since the reinspection addressed by this reportable item was completed.
These connections were found to lack documentation, indicating they had not been inspected previously.
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o SAFETY IMPLICATION:
The inability of the end clips and end plates to deflect under bolt tension, to close the mating surface gaps resulting from fabrication tolerances (allowing the girders to be fabricated slightly short for erection purposes) has two implications. The lack of contact area may affect the slip resistance in the friction connection. But more importantly, where the surfaces are not in contact, the bolt tension load is transferred to the weld attaching the clip or plate to the girder, potentially overstressing the weld.
REASON DEFICIENCY IS REPORTABLE:
Reportable due to the magnitude of the problem plus the extensive evaluation and/or rework required.
CORRECTIVE ACTION:
Appropriate site technical procedures have been revised to specifically require inspection for mating surface gap during erection.
Inspection and craft personnel have received additional training in in pection and erection of structural steel through formal classes and on-the-job training.
Permanent Waivers (PW's) were written, requiring engineering evaluation,for each deficient connection. Each connection not accepted "as-is", as not being significantly deficient, has been repaired to make it acceptable, based on this engineering evaluation, in addition to the deficiency documented in this report, structural connections in the Turbine and Containment Buildings also exhibited evidence of grease between mating surfaces and, in the Turbine Building, torch cut bolt holes.
These conditions were reported as NRC Reportable items 102 and 112, respectively. Connections in the Containment Building have been accepted or repaired based on engineering evaluations.
In the course of the reinspections, the welded parts of the connections were inspected as well, and any deficiencies documented.
Ebasco Services has completed a reanalysis of the Turbine Building structure taking into consideration the identified defects in combination. Actions required to close this item have now been completed.
FINAL REPORT:
We are currently in the documentation review / verification process which is required prior to close out of our site nonconformance report. It is projected that the final report will be issued by May 10, 1985.
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