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

2. 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

3. 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

4. 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

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

6. 2011 Power Plant Simulation Conference
ANO1 Rod Withdrawal
2011 Power Plant Simulation Conference

7. 2011 Power Plant Simulation Conference
ANO1 Rod Withdrawal
2011 Power Plant Simulation Conference

8. 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

9. 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

10. 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

11. 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

12. 2011 Power Plant Simulation Conference
ANO1 Rod Withdrawal
2011 Power Plant Simulation Conference

13. 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

14. 2011 Power Plant Simulation Conference
ANO1 Rod Withdrawal
2011 Power Plant Simulation Conference

15. 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

16. 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