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, March 09, 2021
Page Last Reviewed/Updated Tuesday, March 09, 2021