PEACH BOTTOM 3 0% 08/07/00 Hot Shutdown
REACTOR SCRAM FROM 100% POWER DUE
TO FALSE LOW REACTOR WATER LEVEL
INDICATIONS. - SEE EVENT #37212

-- spider (spider0@usa.net), August 08, 2000

Answers

Here is a related story from the TB2000 archives.

Peach Bottom Unit 2: Loss of Plant Monitoring System Computers During Y2K Testing On February 8, 1999, while performing testing for a Y2K remediation modification to the Unit 2 rod worth minimizer (RWM) system, operators experienced a lock-up of both the primary and backup plant monitoring system (PMS) computers. As a result, operators also lost the following PMS-supported systems for about seven hours: safety parameter display system (SPDS), emergency response data system (ERDS), and 3D Monicore thermal limit monitoring system. Engineers had taken the backup PMS computer off-line and had advanced the PMS clock to a year 2000 Date. This led to a lockup of the backup PMS, and the system transferred to the primary, on-line PMS computer. The engineers did not recognize that the system had transferred and, believing that the original command was not accepted, again advanced the system clock, causing the primary PMS to lock up also. Several initial attempts to restore the PMS computers were unsuccessful, and operators determined that this constituted a major loss of emergency assessment capability. The PMS computers are not Y2K compliant, but the engineers believed that this would not impact the testing. Operators did not expect the testing would affect the on-line PMS computer. However, before the testing began, operators took contingency actions to lower Unit 2 power slightly to ensure shift average power levels were not exceeded. The licensee plans to perform a full root cause analysis of this event.

-- spider (spider0@usa.net), August 08, 2000.