This is to report the Salem Unit 1, 1B
Emergency Diesel Generator (
EDG) actuation due to an invalid signal.
This report is being made per paragraphs 10CFR50.73 (a)(1) and 10CFR50.73(a)(2)(iv)(A) to address the invalid actuation of the 1B EDG on April 17, 2016, during replacement of an indicating bulb.
Plant conditions; Salem Unit 1 was in mode 6 at the time of the invalid actuation.
On April 17, 2016, at approximately 2055 [EDT] while performing Solid State Protection System (SSPS) testing of the 1B Safeguards Equipment Cabinet (SEC), operators identified that an input test light was not lit as expected.
At approximately 2104 [EDT] while attempting to replace the light bulb, the 1B EDG unexpectedly automatically started.
The 1B EDG responded properly to the auto start signal and started in SEC Mode 1, accident only, and did not load.
The cause of the inadvertent start was determined to be a loss of the block circuit which allowed an output to the logic module which then caused the EDG to auto start. Subsequent testing of the input block switches demonstrated that, due to switch degradation, slight pressure applied to the switch was enough to allow the block signal to be momentarily interrupted, even without repositioning of the switch. It was determined that the loss of the block was most likely due to the operators finger coming in contact with the switch during the bulb replacement.
The licensee has notified the NRC Resident Inspector. The licensee will notify the State of
New Jersey and Delaware.
