Turbine Trip Due to Inadvertent Operation of ECI Injection Valves During Routine Testing at Pickering NGS-B

Abstract

During routine emergency coolant injection system (ECIS) testing a control panel operating error resulted in a partial reactor core bypass flow of the primary heat transport coolant, through the odd-numbered D20 injection valves. A reactor trip was averted by prompt operator action, but a turbine generator trip on high boiler level did occur. The unit was successfully recovered from this upset and returned to high power operation. The event was reviewed in some detail, as similar upsets have previously occurred. It was determined that a number of factors contributed to the event, principally in the areas of control panel ergonomics, the test procedure that was used, control room staffing, and the scheduling of safety system testing. A number of corrective measures which have been put in place are discussed, and it is anticipated that these will minimize the risk of re-occurrence of this event in the future. The findings from this investigation are generally applicable to all main control room routine panel testing operations, and merit review for their applicability at other facilities.