United States Nuclear Regulatory Commission - Protecting People and the Environment

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. 

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