United States Nuclear Regulatory Commission - Protecting People and the Environment

Information Notice No. 83-70: Vibration-Induced Valve Failures

                                                            SSINS No.: 6835 
                                                            IN 83-70       

                                UNITED STATES
                        NUCLEAR REGULATORY COMMISSION
                    OFFICE OF INSPECTION AND ENFORCEMENT
                           WASHINGTON, D.C. 20555
                                     
                              October 25, 1983

Information Notice No. 83-70: VIBRATION-INDUCED VALVE FAILURES 

Addressees: 

All nuclear reactor facilities holding an operating license (OL) or 
construction permit (CP). 

Purpose: 

This information notice is provided as a notification of events that 
resulted in valve failures and system inoperability as a result of normal 
operational vibration. It is expected that recipients will review the 
information for applicability to their facilities. No specific action or 
response is required at this time. 

Description of Circumstances: 

A review of recent Construction Deficiency Reports and License Event Reports
indicates that there have been a number of vibration-induced valve failures.
Discussions with General Electric indicate that some of these failures may 
be generic to a specific valve type. The following is a brief account of 
some of these events. 

On October 22, 1982, at Quad Cities Station Unit 2, it was decided to cycle 
the 2A recirculation pump discharge valve during the current maintenance 
outage. The valve had exhibited problems in opening and closing in the past 
and the licensee wanted to verify proper operation while the reactor was 
shut down. When the valve was given a close signal, it would not fully 
close. An inspection of the valve in the Unit 2 drywell revealed that two of 
the four valve yoke-to-bonnet holddown studs and nuts were missing and the 
valve motor operator had pulled the yoke away from the valve. Further 
investigation revealed that the valve stem was bent and would have to be 
replaced. Apparently the valve studs and nuts had loosened and fallen out 
from normal system vibration. 

On June 21, 1983, at Quad Cities Station Unit 1, the maintenance department 
was investigating a position indication problem on a suppression pool return
valve in the B loop of the residual heat removal (RHR) system. An inspection
of the valve revealed that two of the four bolts that hold the valve yoke to
the bonnet had vibrated loose. This allowed the yoke to separate from the 
bonnet causing the valve stem to bind excessively and finally bend. The B 
loop of the RHR containment cooling system was declared inoperable until the
valve could be manually opened. 


8308310030 
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                                                           IN 83-70        
                                                           October 25, 1983 
                                                           Page 2 of 3     


On January 14, 1983, at Browns Ferry Station Unit 3, during routine testing 
of the RHR valves, a low pressure coolant injection (LPCI) valve failed to 
operate properly. An inspection of the valve revealed that the stud and nut 
combination that retains the yoke collar device had loosened. This allowed 
the motor operator to turn (with the yoke) around the valve stem causing 
motor and valve damage. An inspection of other RHR and LPCI valves 
indicated, that 50% of these valves had loose collar devices. The loosened 
devices were attributed to vibrational loading of the yoke-to-bonnet 
interface. The affected valves are gate valves manufactured by the Walworth 
Company. Locking devices were installed on the studs and nuts of the collar 
device to prevent future instances of vibrational loosening. 

At Shoreham Station Unit 1, during valve testing, it was discovered that a 
stem clamp was missing on an RHR globe valve. Although this was considered 
an isolated event, the appropriate startup procedure was revised to include 
a check to ensure that each stem clamp was properly oriented on the stem, 
with the clamp key and setscrew properly tightened. Following this event, 
another globe valve failed to stroke while being tested. The valve stem 
clamp setscrew loosened, allowing the clamp to slide along the stem and the 
clamp key to fall from its keyway. This allowed the motor operator to rotate 
the stem without moving the valve disc. It is believed that the setscrew in 
the stem clamp loosened because of normal system vibration. Stone & Webster 
performed a review of the safety-related valves at Shoreham and has 
determined that only globe valves manufactured by the Anchor Darling Co. are
susceptible to vibrational failures of this type. 

Following these events at Shoreham Station, General Electric notified the 
NRC that similar failures of this type were experienced in the high pressure
core spray (HPCS) system at Zimmer Station. The valves were Anchor Darling 
globe valves specified by General Electric for HPCS systems in the test 
return line of all BWR/5s and BWR/6s. To preclude the possibility of future 
failures, both Anchor Darling and General Electric have provided 
recommendations on how to secure the stem clamp setscrews. 

The valve failure at Shoreham Station was especially significant because the
remote valve position indication was from limit switches on the motor 
operator, so the valve appeared to be opening and closing normally when in 
fact the valve had not moved. Station personnel should be aware of the 
potential for vibrational loosening of valve components and may want to 
emphasize this aspect in valve preventive maintenance. 

Other recently issued IE generic communications addressing valve locking 
devices include, Information Notice No. 81-33, "Locking Devices 
Inadequately Installed on Main Steam Isolation Valves," IE Circular No. 
80-04, "Securing of Threaded Locking Devices on Safety-Related Equipment," 
and IE Circular No. 79-04 "Loose Locking Nut on Limitorque Valve Operators."
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                                                           IN 83-70        
                                                           October 25, 1983 
                                                           Page 3 of 3     

No written response to this notice is required. If you have any questions 
regarding this matter, please contact the Regional Administrator of the 
appropriate NRC Regional Office, or this office. 


                                   Edward L. Jordan Director 
                                   Division of Emergency Preparedness 
                                     and Engineering Response 
                                   Office of Inspection and Enforcement 

Technical Contact:  Paul R. Farron
                    (301) 492-4766

Attachment:
List of Recently Issued IE Information Notices
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