Semantic search
| Report date | Site | Event description | |
|---|---|---|---|
| 05000334/LER-2001-003 | 21 December 2001 | Beaver Valley | At 1416 hours on November 6, 2001, Beaver Valley Power Station Unit No. 1 reactor automatically tripped from 100% power due to low-low level in the C Steam Generator. The Feedwater Level Control Valve on the C Steam Generator unexpectedly failed closed causing the C Steam Generator water level to rapidly drop and reach the low-low water level reactor trip setpoint. Prior to the reactor trip, the Control Board Operator attempted to open the Feedwater Level Control Valve in manual control and observed no increase in the demand signal indicator or feedwater flow. After the reactor trip, Emergency Operating Procedure E-0 for Reactor Trip was performed and the plant was stabilized in Mode 3. The automatic initiation of a reactor trip from 100% power via the Reactor Protection System on November 6, 2001, was a valid reactor trip and was not part of a pre-planned sequence during testing or reactor operation. Therefore this event is reportable pursuant to 10 CFR 50.72(b)(2)(iv)(B) and 50.73(a)(2)(iv)(A). The cause of the unexpected closure of the C Main Feedwater Regulating Valve was a random failure of a diode in the 7100 process rack module that controls the valve actuator. The safety significance of the automatic reactor trip on November 6, 2001 was small. |
| 05000334/LER-2001-002 | 29 November 2001 | Beaver Valley | On October 6, 2001, Beaver Valley Power Station Unit No. 1 testing personnel and the Control Room operators were performing a Control Rod Drop Testing surveillance in preparation for reactor startup following Unit l's fourteenth refueling outage. The plant was in a sub-critical condition in Mode 3 with Shutdown Bank B control rods withdrawn. At 1959 hours, the Control Room operators observed indications of two dropped control rods (via rod position indication reading zero steps and rod bottom lights on), and entered Unit 1 Abnormal Operating Procedure (AOP) 1.1.8 for Rod Inoperability. The Reactor Operator opened the reactor trip breakers in accordance with the AOP and the Reactivity Management Plan. Emergency Operating Procedure E-0 for Reactor Trip was performed and the plant remained in Mode 3. The manual initiation of a reactor trip via the Reactor Protection System by the BVPS Unit 1 control room operator on October 6, 2001, was a valid manual reactor trip signal and was not part of a pre-planned sequence during testing or reactor operation. Therefore this event is reportable pursuant to 10 CFR 50.73(a)(2)(iv)(A). It was subsequently discovered that the two dropped control rod indications were caused by the testing personnel repositioning knife switches to place the rod drop computer in service. There were no dropped control rods. This action by the testing personnel and resulting expected indications were not communicated to the Control Room operators prior to their occurrence. The opening of the reactor trip breakers was caused by a lack of good communication practices and a lack of procedure adherence by an inexperienced test engineer. This engineer failed to read a step in the test procedure which required the engineer to inform the Reactor Operator that the control room would be losing indication on control rod Shutdown Bank B. The safety significance of the manual reactor trip on October 6, 2001 was small. |