United States Nuclear Regulatory Commission - Protecting People and the Environment

Information Notice No. 83-22: Boiling Water Reactor Safety/Relief Valve Failures

                                                             SSINS No. 6835 
                                                             IN 83-22      

                               UNITED STATES 
                       NUCLEAR REGULATORY COMMISSION 
                    OFFICE OF INSPECTION AND ENFORCEMENT 
                          WASHINGTON, D.C.  20555 
                                     
                               April 22, 1983 

Information Notice No. 83-22:   BOILING WATER REACTOR SAFETY/RELIEF VALVE 
                                   FAILURES 

Addressees: 

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

Purpose: 

This information notice is provided as a notification of a potentially 
significant problem pertaining to Target Rock two-stage safety/relief 
valves. 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: 

On February 5, 1983, TVA Browns Ferry Unit 1 was operating at 100% power. 
While conducting turbine overspeed tests, the reactor scrammed and isolated.
Three safety/relief valves (SRVs) were opened at 1105 psig and two reseated 
but one remained opened, blowing the reactor down to 120 psig, after which 
the valve appeared to reseat. The unidentified leak that remained was 
attributed to a vacuum breaker on the SRV tail pipe and the failure to seat 
was initially blamed on a faulty air solenoid. On restart, the reactor was 
again depressurized (from 178 psig) by the SRV that had previously failed to
reseat. The subsequent licensee investigation showed that the pilot inlet 
tube mounting bracket had broken, permitting the inlet tube to lodge between
the main disc and seat. 

Browns Ferry Units 1, 2, and 3 have two-stage Target Rock model 7567F 
safety/ relief valves. See Figure 1 for details. (Ref. LER 50-259/83-006). 

A similar event occurred in March 1982 at Georgia Power's Hatch Unit 2. Wyle
Laboratory personnel reported to Georgia Power that one of the top works of 
the SRVs that they were testing had a missing inlet sensing tube. This tube 
had been held in place by welds which had failed. These were also two-stage 
Target Rock SRVs model number 7567F (Ref. LER 50-366/82-023). 

General Electric Service Information Letter (SIL) No. 196, Supplement 12, 
dated November 1982 discusses problems that have occurred with two-stage and
three-stage Target Rock SRVs and makes recommendations for corrective 
actions. One of the areas covered was failures of the pilot inlet tube 
attachments. 


8303040023 
.

                                                             IN 83-22      
                                                             April 22, 1983 
                                                             Page 2 of 2   

Information Notice No. 82-41, "Failure of Safety Relief Valves to Open at a 
BWR," issued on October 22, 1982, and INPO Significant Event Report 50-82, 
issued on August 13, 1982 dealt with problems of setpoint drift of Target 
Rock two-stage safety/relief valves. 

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 

Attachments: 
1.   Figure 1 of Two-Stage Target Rock Model 7567F 
     Safety/Relief Valves 

2.   List of Recently Issued IE Information Notices 


Technical Contact:  Mary S. Wegner, IE 
                    (301) 492-4511

Page Last Reviewed/Updated Tuesday, November 12, 2013