Protecting People and the EnvironmentUNITED STATES NUCLEAR REGULATORY COMMISSION
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
