Selected safety-related occurrences reported in March and April 1975

Five occurrences reported during March and April 1975 are summarized because of their uniqueness and/or general interest to reactor operations. Relief valves failing to close at two boiling-water reactors (BWRs) in Europe caused suppression-pool damage, and a single tube failure in a steam generator at Point Beach caused a leak rate of 125 gal/min from the primary to the secondary systems. In an event that attracted some publicity, the plant heating system at the Millstone nuclear power station became contaminated. Monticello appears to have solved its problem of explosions in off-gas systems through a number of system-design modifications. The cable fire that occurred at the Browns Ferry nuclear power station will inactivate the plant for several months. (U.S.)