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Information Notice No. 81-35: Check Valve Failures
SSINS No.: 6835 Accession No.: 8107230041 IN 81-35 UNITED STATES NUCLEAR REGULATORY COMMISSION OFFICE OF INSPECTION AND ENFORCEMENT WASHINGTON, D.C. 20555 December 2, 1981 Information Notice No. 81-35: CHECK VALVE FAILURES Description of Circumstances: After undertaking a program at Three Mile Island Nuclear Station Unit 1 (TMI-1) to follow the recommendations in IE Circular 78-15, "Tilting Disk Check Valves Fail to Close With Gravity in Vertical Position," Metropolitan Edison Company (Met-Ed) reported (LER 80-003/01T and supplement) loose valve internals in the high-pressure injection pump discharge check valves. The valves are Crane three-inch 1500# tilting disk check valves. The initial cause of the loose valve internals was traced to the corrosion of the seat hold-down devices of the valves. As a result of these findings, Met-Ed developed and implemented a continuing inspection program for TMI-1. A design study of the tilting disk check valves was also conducted. Further inspection led to the discovery that some valves could not prevent back flow due to the failure of the hinge pin and seat ring retention devices. A hinge pin was found to have fallen off, and tack welds on the hinge pin retaining screws were either cracked, weak, or nonexistent. In the seat ring retention device, one lock plate assembly was missing and the seat ring retention device became loose because washers were not installed. Met-Ed also found many fabrication inconsistencies that may have initiated and/or contributed to these, failures. These inconsistencies ranged from the use of materials, other than those specified in procurement documents, to poor workmanship, particularly in the case of welds. For instance, where tack welds were called for on the hinge pin retaining screws, the screws were peened. There were also instances where flat washers were installed in the valves instead of spring washers, and nickel-plated carbon steel washers were used when precipitation hardened stainless steel washers were specified. Additional problems with disk retaining pins in Crane check valves were reported by Florida Power Company (LERs 80-017/03L-O and 80-021/03L-O) at Crystal River Unit 3 and by Virginia Electric and Power Company (LER 80-023/01T-O) at Surry Unit 1. . IN 81-35 December 2, 1981 Page 2 of 2 The failure of the hinge lugs on a Mission Manufacturing Company check valve at Fort Calhoun Station was reported by Omaha Public Power District (LER 78-036/ 03L-O). The failure of the hinge lugs allowed the disk plate to migrate to the steam generator. No damage was observed in the steam generator when the disk plate was removed. The valve is a Mission Type 3"-C308, Style "B" Duo Check, Series 900 check valve. The discovery of internal damage to two Anchor Darling check valves at Arkansas Nuclear One Unit 2 was reported by Arkansas Power and Light Company (LER 81-034/ 99X-0). When the first valve was opened to repair a leak, it was discovered that the disk pin was broken from the disk and the disk pin, pin nut, and washer were missing. The equivalent valve in the redundant train was then opened and a disk pin nut and Washer were found missing. Both failures were attributed to the valve being manufactured with wire used as the locking device rather than the pin shown on the design drawing. Both valves are Anchor Darling four-inch swing check valves, drawing number 3102-3. Thus, the check valve failures can be attributed to two main causes: (1) poor retaining device design, and (2) poor quality control on the assembly of the valve internals. Similar problems with check valves from another manufacturer are described in IE Information Notices No. 80-41, "Failure of Swing Check Valve in the Decay Heat Removal System at Davis-Besse Unit No. 1," and 81-30, "Velan Swing Check Valves. This information is provided as notification of a potentially significant matter. It, is expected that recipients will review the information for possible applicability to their facilities, No specific action or response is requested at this time. If you have questions regarding this matter, please contact the Regional Administrator of the appropriate NRC Regional Office. Attachment: Recently issued IE Information Notices
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