Event Notification Report for December 22, 2012

MINOR INCIDENTAL URANIUM HEXAFLUORIDE RELEASE

"Note this is a late report (1/17/2013).

"During December 2012, the C-360 Toll Transfer and Sample building experienced three incidents where the Laboratory Process Gas Leak Detection (PGLD) system was actuated. No visible smoke was ever seen. Subsequent bioassay samples of personnel in the area confirmed that minor exposures did occur, although no work restrictions were required. The exposures confirm that the PGLD actuations were due to actual minor incidental uranium hexafluoride releases. Investigation and testing found that the first two incidents were caused by a small pinhole leak in instrument tubing and the third incident was caused by slight leakage around the stem of a small instrument valve. These three events were evaluated for reportability at the time they occurred, but it was determined they did not meet our reporting criteria. However, after further evaluation and discussion with NRC staff, USEC is conservatively reporting the incidents.

"The actuations occurred on December 22, 23, and 29, 2012. Upon each actuation, the system automatically closed the appropriate valves as designed. Response to each leak consisted of atmospheric sampling for HF and radiological swipes per procedure along with precautionary bioassay samples. The atmospheric sampling and radiological swipes on the first release were negative and the system was returned to service. The second incident the next day was similar to the first and again the immediate samples were negative. Bioassay results were then obtained from the previous night and showed a detectable exposure. With confirmation of a small leak, helium leak detection was utilized to find the small pinhole leak. The third incident was due to slight leakage around a valve stem that was discovered by soap testing the valve and evidence of some visible oxides on the valve stem.

"These types of releases are incidental and do not have the potential for impact on the health and safety of personnel or the public.

"These incidents are being conservatively reported as a 24-hour event based on SAR 6.9 Table 1, J.2 as an Unplanned Actuation of a Q Safety System." An automatic or manual actuation of a Q safety system that results from an event or condition that has the potential for significant impact on the health or safety of personnel. Events having the potential for significant Impact are those events where actual plant conditions existed that the system was designed to protect against."

"The NRC Senior Resident Inspector has been notified of this event."

AUTOMATIC REACTOR SCRAM DUE TO LOSS OF POWER TO THE REACTOR PROTECTION SYSTEM

"On 12/22/2012 at 1152 CST, the Unit 2 reactor automatically scrammed due to actuation of the Reactor Protection System (RPS) from loss of power to RPS. At 1134 CST, the D 4kV Shutdown Board unexpectedly de-energized during performance of post-maintenance testing for the 3D Diesel Generator paralleling circuitry, resulting in loss of power to the 2B RPS subsystem. Primary Containment Isolation System (PCIS) groups 2, 3, 6, and 8 isolations were received along with automatic initiation of A, B, and C Standby Gas Treatment subsystems and A Control Room Emergency Ventilation subsystem due to loss of power to the 2B RPS subsystem. While attempting to reenergize the 2B RPS subsystem, the 2A RPS subsystem was inadvertently de-energized resulting in Unit 2 reactor automatic scram.

"All affected safety systems responded as expected for the loss of RPS and reactor scram. Due to the loss of RPS, the Main Steam Isolation Valves (MSIVs) closed. Reactor pressure did not rise to the automatic initiation set point for Safety Relief Valve (SRV) actuation. Reactor Core Isolation Cooling System (RCIC) and High Pressure Coolant Injection System (HPCI) reactor water level initiation set point of -45" was reached and RCIC and HPCI automatically initiated as designed to restore water level above the initiation set point. Both Recirculation Pumps also tripped on reactor water level of -45". Reactor pressure control was established by manually operating one SRV and water level control established with RCIC. HPCI was returned to standby readiness. The scram was reset, MSIVs were opened, and the Main Condenser was established as a heat sink.

"The scram event from critical is reportable within 4 hours per 10 CFR 50.72(b)(2)(iv)(B). It is also reportable within 8 hours per 10 CFR 50.72(b)(3)(iv)(A) and requires an LER within 60 days per 10 CFR 50.73(a)(2)(iv)(A).

"The NRC Resident Inspector was notified."

The 2A and 2B RPS subsystems were returned to service. The electrical grid is stable and supplying shutdown loads on Unit 2. Unit 1 and Unit 3 were unaffected and continue to operate at 100% power.

OFFSITE NOTIFICATION DUE TO LOSS OF AMERTAP BALLS

"At 1740 CST, Xcel Energy notified the Minnesota State Duty Officer that up to 1500 Amertap Balls had been lost from the Prairie Island Nuclear Generating Plant Unit 2 Condenser Tube Cleaning System. Since the Minnesota State Duty Officer for the Division of Emergency Management was notified, this constitutes a 4 hour non-emergency notification per 10CFR50.72(b)(2)(xi)."

The licensee has notified the NRC Resident Inspector.

60 DAY REPORT - INVALID ACTUATION OF THE AFW SYSTEM

"This 60-day optional report as allowed by 10 CFR 50.73(a)(1), is being made under the reporting requirement in 10 CFR 50.73(a)(2)(iv)(A) to describe an invalid actuation of a specified system, specifically the Auxiliary Feedwater (AFW) system. On December 22, 2012 at 0142, with Unit 1 in Mode 4, the 1A AFW pump automatically started due to failure to reset the signal created when the 1B Feedwater Pump was tripped for testing. The 1A feedwater pump was already in the 'tripped' condition when the 1B feedwater pump was tripped, resulting in an auto start signal being generated for the AFW system. Both trains of the AFW had the auto start defeat instated at the time of the testing of the 1B Feedwater pump, blocking the start signal. During subsequent alignment of the AFW for standby readiness, the auto start defeat was removed from the 1A AFW system without resetting the system to remove the signal generated during the 1B Feedwater pump testing, resulting in the actuation of the system. The 1B Feedwater Pump had been reset and was in service therefore the signal associated with the trip of both feedwater pumps was not consistent with the actual plant conditions at the time that the auto start defeat was removed from the 1A AFW system. Following the auto start of the 1A motor driven AFW pump, operators confirmed the 1A AFW train experienced a complete actuation and that the 1A AFW Pump and its associated valves functioned as designed. The pump was subsequently secured and the AFW system was returned to standby readiness. This event was entered into the site specific correction action program for resolution."

The NRC Resident Inspector has been informed. The licensee will notify the states of North Carolina and South Carolina. Additionally the licensee will notify York, Gaston, and Mecklenburg County.