ML20138L629

Forwards Safety Evaluation of 850829 Info on Implementation of Rev 2 to NCIG-01, Visual Weld Acceptance Criteria for Structural Welding at Nuclear Power Plants & Proposed Changes to Fsar.Proposed Changes Acceptable.W/O Encl

ML20138L629
Person / Time
Site:	South Texas
Issue date:	10/23/1985
From:	Knighton G Office of Nuclear Reactor Regulation
To:	Goldberg J HOUSTON LIGHTING & POWER CO.
References
NUDOCS 8510310362
Download: ML20138L629 (6)

Text

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D CT 2 3 1985 a

Docket Nos.: 50-498 i,

and 50-499 Mr. H. Goldberg Grou; Vice President - Nuclear Houston Lighting and Power Company Post Office Box 1700 Houston, Texas 77001

SUBJECT:

IMPLEMENTATION OF NCIG-01, REV. 2 " VISUAL WELD ACCEPTANCE CRITERIA FOR STRUCTURAL WELDING AT NUCLEAR POWER PLANTS" FOR THE SOUTH TEXAS PROJECT UNITS 1 AND 2.

Your letter of August 29, 1985 provided information on implementation of the subject acceptance criteria, including the proposed changes to the FSAR.

The NRC staff has reviewed the submittal and found the proposed changes to be '

acceptable. The results of this review are contained in the enclosed Safety Evaluation Report. We expect that the FSAR changes will be formally incorporated in a future amendment.

3 Sincerely, j Original s 6ned sy.

i sense w.xaaehtee George W. Knighton, Chief Licensing Branch No. 3 Division of Licensing i

Enclosure:

As stated t

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Mr. J. H. Goldberg Houston Lighting and Power Company South Texas Project cc:

Brian Berwick, Esq. Resident Inspector / South Texas Assistant Attorney General Project Environmental Protection Division c/o U.S. Nuclear Regulatory Commission P. O. Box 12548 P. O. Box 910 Capitol Station Bay City, Texas 77414 Austin, Texas 78711 Mr. Jonathan Davis Mr. J. T. Westermeir Assistant City Attorney Manager, South Texas Project City of Austin Houston Lighting and Power Company P. O. Box 1088 P. O. Box 1700 Austin, Texas 78767 Houston, Texas 77001 Ms. Pat Coy Mr. H. L. Peterson Citizens Concerned About Nuclear Mr. G. Pokorny Power City of Austin 5106 Casa Oro P. O. Box 1088 San Antonio, Texas 78233 Austin, Texas 78767 Mr. Mark R. Wisenberg Mr. J. B. Poston Manager,' Nuclear Licensing Mr. A. Von Rosenberg Houston Lighting and Power Company City Public Service Boad P. O. Box 1700 P. O. Box 1771 Houston, Texas 77001 San Antonio, Texas 78296 Mr. Charles Halligan Jack R. Newman, Esq. Mr. Burton L. Lex Newman & Holtzinger, P.C. Bechtel Corporation 1615 L Street, NW P. O. Box 2166 Washington, D.C. 20036 Houston, Texas 77001 Melbert Schwartz, Jr., Esq. Mr. E. R. Brooks Baker & Botts Mr. R. L. Range One Shell Plaza Central Power and Light Company Houston, Texas 77002 P. O. Box 2122 Corpus Christi, Texas 78403 Mrs. Peggy Buchorn Executive Director Citizens for Equitable Utilities, Inc.

Reute 1, Box 1684 Brazoria, Texas 77422 i

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1 Houston Lighting & Power Company South Texas Project '

cc:

Regional Administrator, Region IV U.S. Nuclear Regulatory Commission Office of Executive Director for Operations 611 Ryan Plaza Drive, Suite 1000 -

Arlington, Texas 76011 Mr. Lanny Sinkin Citizens Concerned About Nuclear Power 3022 Porter Street, NW #304 Washington, D.C. 20008 Mr. S. Head, Representative Houston Lighting and Power Company Suite 1309 7910 Woodmont Avenue Bethesda, Maryland 20814 1

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Lnclosure Houston Lighting & Power South Texas Project Units 1 and 2 Docket Nos. 498/499 Visual Inspection Acceptance Criteria for Structural Steel and Miscellaneous Steel Welding to Meet Design Requirements The staff concludes that the use of Nuclear Construction Iss,ues Group (NCIG)-01, Rev. 2, 05/07/85, " Visual Weld Acceptance Criteria for Structural Welding at Nuclear Power Plants" (VWAC) will provide adequate quality of non-ASME Code structural steel welds. These criteria are limited to non-ASME class welded steel structures where fatigue is not the governing design consideration. Typical examples of structures to which these criteria may be applied are main building framing members and connecting members, supports for equipment and piping (non-ASME Code), cable trays and conduit, HVAC ducts and duct supports, and miscellaneous steel including bracing and stiffeners, embedments, stairways and handrails, doors and door frames, windows and win-dow frames, gratings, covers, etc. -

There are eleven criteria addressed in VWAC. For cracks, the same criteria as exists in AWS D 1.1 is specified; the welds shall have no cracks. For under-filled craters, if proper weld size is achieved and cracks are absent, there is no reason for rejecting them and, therefore, they are acceptable.

For arc strikes, surface slag and weld spatter, the VWAC criteria are based more on the effects on structural strength rather than workmanship. Arc strikes are acceptable provided cracks are not visually detectable. Weld spatter remaining after cleaning is acceptable. For surface slag, the criteria are designed to prevent the acceptance of a weld which shows a gross lack of con-trol by the welder. Isolated surface slag which remains after weld cleaning has no structural significance.

l Criteria for the following types of defects / faults are also provided in VWAC:

a) fillet weld size b) incomplete fusion c) weld overlap d) weld profiles e) undercut f) surface porosity ,

g) weld length and location s

The basis for the acceptance criteria in VWAC is the amount of reduction in cross sectional area caused by the defect or fault. In such calculations, the conservative approach used is to consider the length of weld in which a defect occurs as being non-existent, i.e., does not support any of the load.

! Such cross section reductions are usually less than 12.5 percent.

There are some exceptions to this, particularly in thinner section members.

This occurs because measurements of defects / faults are rounded off up to the smallest measurement unit specified. For instance, a 1/32 inch maximum under-cut for the entire length on one side for 3/16 inch thickness material results Ir. a 16.7 percent reduction in area. Because the 1/32 inch undercut will not i

be uniform along the entire length, most of the undercut will be less than

, 1/32 inch in depth. Although the 16.7 percent maximum reduction is a theoreti-cal possibility, it is not likely to occur.

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The 12.5 percent " benchmark" was chosen based upon the presently allowed percent reduction in area affected by the undercut criteria in AWS D 1.1-85 for the most limiting case in the thinnest member. The reasoning behind 2

this is that if undercut is allowed to reduce the load carr,ying capability i by a given number, other defects / faults that would result in a reduction of similar or less magnitude should also be acceptable.

The acceptance by engineering evaluation of thousands of field weldments with similar defects / faults not meeting the criteria of AWS D 1.1 has resulted in the decision to use the weldments "as is" without repair. This is possible because common engineering design practices result in significant margins

above design requirements, such that a small reduction of 10 to 12 percent l can be easily accommodated. The present undercut criteria in AWS D 1.1-85 is a practical demonstration of this. .

The deviations from AWS D 1.1 as proposed in VWAC are relatively insignifi-cant in that the redundancy of these structures and their individual welds, and the conservative design practices used, allow non-ASME Code structural steel weldments (which are not designed for fatigue) to use alternative cri-teria as provided in Criterion II of 10 CFR, Part 50, Appendix B. We find these criteria are appropriate and provide adequate integrity of the affected structures and, accordingly, General Design Criterion 1 of Appendix A to 10 CFR Part 50 has been met.

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