Continuous Rod Withdrawal Arkansas Nuclear One Continuous Rod Withdrawal (SOER 10-2) 2011 Power Plant Simulation Conference

ANO1 Rod Withdrawal SOER 10-2, Engaged, Thinking Organizations “In the past 18 months, a number of significant operational events revealed unacceptable weaknesses in important barriers to sustained high levels of nuclear safety.” “Most of these events occurred at stations that are, by many measures, good performers.” 2011 Power Plant Simulation Conference

2011 Power Plant Simulation Conference ANO1 Rod Withdrawal April 25, 2010 Arkansas Nuclear One (ANO) – In April 2010, during post-outage startup activities, the Unit 1 reactor automatically scrammed when control rods withdrew for 38 seconds while nuclear instruments were being calibrated. Miscommunications between the control board operator and instrument and control technicians led to the rod control station not being configured correctly for the calibration. 2011 Power Plant Simulation Conference

ANO1 Rod Withdrawal Arkansas Nuclear One (Entergy) Unit 1 – B&W Two Loop PWR Once Through Steam Generators Power: 2568 MWt / 883 MWe Heat Sink – Lake Dardanelle Commercial Operation: 12/19/74 Integrated Control System (ICS) provides fully automatic control of reactor power, steam generation rate, and generated load by the processing of selected signals of measured plant parameters. 2010 Power Plant Simulation Conference

ICS Reactor Demand / Control Rod Drive ANO1 Rod Withdrawal ICS Reactor Demand / Control Rod Drive Demanded Power 2011 Power Plant Simulation Conference

2011 Power Plant Simulation Conference ANO1 Rod Withdrawal 2011 Power Plant Simulation Conference

2011 Power Plant Simulation Conference ANO1 Rod Withdrawal 2011 Power Plant Simulation Conference

ANO1 Rod Withdrawal The Setting The Unit 1 reactor was stabilized at ~19.5% heat balance power during a power ascension following refueling outage (1R22). Excore Nuclear Instrument (NI) gains had been conservatively set high for low power physics testing. The high neutron flux trip setpoints had been conservatively established at 50% excore power for low power reactor physics testing. NI‑5 (RPS Channel ‘A’) ‑ 29.3% NI‑6 (RPS Channel ‘B’) ‑ 30.1% NI‑7 (RPS Channel ‘C’) ‑ 33.4% NI‑8 (RPS Channel ‘D’) ‑ 32.4% 2011 Power Plant Simulation Conference

2011 Power Plant Simulation Conference ANO1 Rod Withdrawal Distractions Crew was in transition from the outage crew that had been together during the entire outage. The main generator input to ICS was not functioning properly. This is where the AOM was spending effort ICS in manual EXCEPT rod control Rod control in automatic for stable plant ops (boron/xenon). Generator H2 temperature control valve troubleshooting in progress. This is where the SM was spending effort Voltage regulator testing in progress. The ATC Operator was performing RCS delithiation activities. NI calibration needed prior to 20% to continue power ascension. 2011 Power Plant Simulation Conference

2011 Power Plant Simulation Conference ANO1 Rod Withdrawal What Happened I&C technician asked “is ICS is manual” The ICS was in manual EXCEPT rod control The turbine operator missed this aspect The I&C procedure step specifically required the DIAMOND rod control to be in manual. The Swiss cheese holes are now aligned for the event. 2011 Power Plant Simulation Conference

RPS Auctioneered Linear Power ANO1 Rod Withdrawal RPS Auctioneered Linear Power 19.5% ------- 33.4% 32.4% 19.5% 30.1% 33.4% 32.4% 29.3% 30.1% 33.4% 32.4% 19.5% 30.1% 2011 Power Plant Simulation Conference

2011 Power Plant Simulation Conference ANO1 Rod Withdrawal 2011 Power Plant Simulation Conference

2011 Power Plant Simulation Conference ANO1 Rod Withdrawal Plant Results: NI‑5 20% to 29% NI‑6 remained in bypass NI‑7 33% to 50% NI‑8 32% to 48% 2011 Power Plant Simulation Conference

2011 Power Plant Simulation Conference ANO1 Rod Withdrawal 2011 Power Plant Simulation Conference

How did we get to this point? ANO1 Rod Withdrawal How did we get to this point? The control room was off-normal Distractions were numerous Crew composition was off-normal Something important was not working properly. Informal communications were allowed. Fundamental knowledge and questioning was not used effectively. Supervision working outside of oversight role. 2011 Power Plant Simulation Conference

What is different in training now? ANO1 Rod Withdrawal What is different in training now? Conducted high intensity training over three training cycles with focus on knowledge and fundamentals. Case studies OE Off-normal simulator initial conditions Combined NLOR and LOR Focus on SM Oversight Use of Industrial Operator Handbook Simulator critiques establish clear priority on knowledge and fundamentals. 2011 Power Plant Simulation Conference