IE Bulletin No. 86-02: Static ''O'' Ring differential pressure switches

The purpose of this bulletin is to request that boiling water reactor (BWR) and pressurized water reactor (PWR) licensees determine whether or not they have Series 102 or 103 differential pressure switches supplied by SOR, Incorporated (formerly Static ''O'' Ring Pressure Switch Company), installed as electrical equipment important to safety. Those licensees that have SOR Series 102 or 103 differential pressure switches installed in systems subject to Technical Specifications are requested to take certain actions to assure that system operation is reliable. On June 1, 1986, LaSalle 2 experienced a feedwater transient that resulted in low water level in the reactor vessel. One of four low level trip channels actuated, resulting in a half scram. The operator recovered level and power operation was continued. However, subsequent reviews by the Licensee's personnel raised concerns that the level apparently had gone below the scram setpoint and that a malfunction of the reactor scram system may have occurred. Based on this concern, the Licensee declared an ''Alert,'' shut the plant down, notified the NRC, and subsequently informed SOR of possible switch malfunctions. NRC dispatched an augmented inspection team to the site on june 2 to investigate the root cause and significance of the feedwater transient, the performance of the differential pressure switches in the low level trip channels, the response of the reactor protections system, and related matters