United States Nuclear Regulatory Commission - Protecting People and the Environment


ACCESSION #: 9805080042







Elgar                        FAX COVER SHEET           Sorensen

(800) 733-5427                                         Division of ELGAR

(619) 450-0085                                         (800) 525-2024

                                                       (619) 450-0085

     9250 Brown Deer Road, San Diego, CA 92121, U.S.A



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                 Elgar Administration Fax: 619/458-0257

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March 27, 1998



File: TB12



Mr. <<(FirstName>> <<(LastName>>

<<(Utility_Name>>

<>

<
> <>, <> <> <> Reference: (1) Licensee Event Report, Clinton Power Station, Docket 05000461, Division 2 Nuclear Protection System Inverter Not in Accordance with the Plant's Design Basis Due to Various Deficiencies, dated 2/26/98. Subject: Technical Bulletin # 12: Installation of Power Semiconductor Clamps Dear Mr. <> Technical Bulletin # 12 addresses a problem found at Illinois Power with the power semiconductor clamps used in the Elgar inverters. The procedure for tightening the clamps at Illinois Power was incorrect. The technique used a torque wrench for applying and verifying the compressive force on the clamps, which is incorrect. The correct method for tightening the clamps involves the use of a force gauge to indicate a proper compressive force on the clamp. Note: The semiconductor clamps must be tightened using the approved force gauge; the use of a torque wrench is prohibited. Elgar recommends that, if the torque wrench method has been used, the power semiconductor clamps be removed and new clamps be installed as soon as practical using the procedure called out in the technical bulletin. In addition, the power semiconductors, secured by clamps that have been tightened using a torque wrench, be replaced, since internal damage may have resulted from the excessive force. After reviewing this technical bulletin, please send back a signed copy of this memo to Elgar indicating that the technical bulletin has been received and acknowledged by the plant. If you have any questions regarding this bulletin, please contact me by phone at 619-458-0245, by FAX at 619-678-4441, or by e-mail at tomm@elgar.com. Sincerely, Thomas A. Moshenrose Acknowledged: Manager, Nuclear Customer Service Date: ELGAR TECHNICAL BULLETIN #12 Sheet 1 of 1 Date: March 27, 1998 Subject: Technical Bulletin # 12: Installation of Power Semiconductor Clamps Reference: (1) Licensee Event Report, Clinton Power Station, Docket 05000461, Division 2 Nuclear Protection System Inverter Not in Accordance with the Plant's Design Basis Due to Various Deficiencies, dated 2/26/98. Description: Per the Licensee Event Report (Reference 1), the compressive force applied to the heatsink clamp hardware for the SCRs and power diodes in the Elgar inverter had been applied and verified incorrectly causing loose connections. A torque wrench at a value of 90-100 inch- pounds was used to apply and verify the compressive force on the heatsink clamp. The compressive force resulting from the use of the torque wrench was excessive. The application of the excessive force caused the spring bars in the clamp to flex beyond their yield point resulting in inadequate force applied to the installed SCRs and diodes. Note: The semiconductor clamps must be tightened using the approved force gauge; the use of a Torque wrench is prohibited. Action: Elgar recommends that the SCR and diode clamps be tightened using a force gauge (Elgar P/N 846-SCR-MB) and the following procedure: 1. Check each heatsink surface for nicks, scratches, and flatness. 2. Apply a thin film of thermal compound. (Note: A thick will adversely affect the electrical and thermal resistances.) 3. Refer to the device preparation sheet for further surface preparation instructions. 4. With the semiconductor positively in place on the heatsink (i.e., the power semiconductor centered on the alignment pin), place the clamp in position with the bolts through the holes in the heatsink. 5. Tightened the nuts evenly until finger-tight. Tighten each bolt 1/4 turn at a time, alternating between bolts, using a 9/16 inch socket wrench. After each 1/4 turn of the bolts, place the force gauge firmly against the spring. When the proper flat edges line up on the upper portion of the force gauge, the clamp is properly tightened. Note: If the bolts have been tightened beyond the proper flat edges on the gauge, the bolts must be loosened to finger-tight and the process of tightening repeated. If the clamps have been tightened using a torque wrench, they should be replaced at the earliest convenient time using the above procedure to install the new clamp. In addition, if the clamp has been installed using a torque wrench at a value of 90-100 inch-pounds, it is probable that the power semiconductor has been damaged by the excessive force applied. Therefore, it is further recommended that, if a torque wrench has been used to tighten the clamps, the power semiconductors be replaced also. Products Affected: All Elgar inverters and uninterruptible power supplies. APPROVALS CUSTOMER SERVICE DATE ENGINEERING DATE QUALITY DATE Mr. Walter Adams Mr. David Bazinet Niagara Mohawk Power Corporation Northeast Nuclear Energy Company Nine Mile Point Unit 2 Connecticut Yankee P. O. Box 63, Lake Road P. O. Box 127E, Lycoming, NY 13093 East Hampton, CT 064243099 Mr. Richard DeBernardo Mr. Therman Carter Northeast Nuclear Energy Company North Atlantic Energy Services Millstone Nuclear Station 3 Seabrook Station Rope Ferry Road (Route 156) P. O. Box 300 Waterford, CT 06385 Seabrook, NH 03874 Mr. John Hill Mr. Jack Nystrom New York Power Authority Northern States Power Indian Point 3 Monticello Nuclear Station P. O. Box 215 2807 W. Highway 75 Buchanan, NY 10511 Monticello, MN 55362 Mr. Donald Flegle Mr. Innan Lee Omaha Public Power District Portland General Fort Calhoun Station Trojan Nuclear Power Plant P. O. Box 399 71760 Columbia River Highway Fort Calhoun, NE 68023 Rainier, OR 97048 Mr. Tar Singh Mr. Charles Johnson Sacramento Municipal Utility District Southern California Edsion Company Rancho Seco Power Plant San Onofre Nuclear Generating Station 14440 Twin Cities Road P. O. Box 128 Herald, CA 95638 San Clemente, CA 92674 Mr. Alan Bryan Mr. Steve Kerstiens Southern Nuclear Operating Company Southern Nuclear Operating Company Plant E. I. Hatch Nuclear Plant Vogtle Electric Generating Plant Highway # 1 P. O. Box 1600 P. O. Box 439 Waynesboro, GA 30830 Baxley, GA 31513 Mr. Jeff LaMarca Mr. Rick Herman TU Electric Company Washington Public Power Comanche Peak Steam Electric Station WNP 2 P. O. Box 1002 P. O. Box 968 Glen Rose, TX 76043 Richland, WA 993520968 Mr. John Slinkard Consumers Energy Company Palisades Nuclear Plant 27780 Bluestar Memorial Hwy. Covert, MI 49043 Mr. Frank Modlin Carolina Power & Light Robinson Nuclear Plant 3581 West Entrance Road Hartsville, SC 29550 Mr. Rick Brock Duke Power Company Oconee Nuclear Station Hwy. 130 Seneca, SC 29679 Mr. Thomas Carpenter Entergy Operations River Bend Station P. O. Box 4220 St. Francisville, LA 70775 Mr. Joseph Tringali Florida Power & Light St. Lucie Nuclear Plant P. O. Box 128 Ft. Pierce, FL 33454 Mr. Burt Schoonover South Texas Project Nuclear Operating Company South Texas Project Electric Generating Station P. O. Box 289 Wadsworth, TX 77483 Mr. Donald Lukach Illinois Power Company Clinton Power Station P. O. Box 678 Clinton, IL 61727 Mr. Steven Barbera Arizona Public Service Company Palo Verde 5401 S. Wintersburg Tonopah, AZ 853547529 Mr. William Slack Cleveland Electric Illuminating Company Perry Nuclear Station 10 Center Road Perry, OH 44081 Mr. Thomas Tremel Duquesne Light Company Beaver Valley Station P. O. Box 4 Shippingport, PA 15077 Mr. John Meibaum Entergy Operations Waterford 3 Power Plant P. O. Box B Killona, LA 700660751 Mr. Douglas Dayton South Texas Project Nuclear Operating Company South Texas Project Electric Generating Station P. O. Box 289 Wadsworth, TX 77483 Mr. Mark Wagner Illinois Power Company Clinton Power Station P. O. Box 678 Clinton, IL 61727 Mr. Harold Ingels IES Utilities Company Duane Arnold Energy Center 3277 DAEC Road Palo, IA 52324 Mr. Jonathan Malloy Wisconsin Electric Company Point Beach Nuclear Plant 6610 Nuclear Road Two Rivers, WI 54241 *** END OF DOCUMENT ***
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