arkansas nuclear one continuous rod withdrawal (soer 10-2) 2011 power plant simulation conference
TRANSCRIPT
Arkansas Nuclear One
Continuous Rod Withdrawal (SOER 10-2)
2011 Power Plant Simulation Conference
2011 Power Plant Simulation Conference
“In the past 18 months, a number of significant operational events revealed unacceptable weaknesses in important barriers to sustained high levels of nuclear safety.”
SOER 10-2, Engaged, Thinking Organizations
ANO1 Rod Withdrawal
“Most of these events occurred at stations that are, by many measures, good performers.”
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 PWROnce Through Steam Generators
Power: 2568 MWt / 883 MWeHeat 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
ANO1 Rod Withdrawal
2011 Power Plant Simulation Conference
ANO1 Rod Withdrawal
ICS Reactor Demand / Control Rod Drive
Demanded Power
2011 Power Plant Simulation Conference
ANO1 Rod Withdrawal
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
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
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
ANO1 Rod Withdrawal
RPS Auctioneered Linear Power
29.3%30.1%
33.4%32.4%
30.1%
19.5%30.1%
33.4%32.4%
19.5%-------
33.4%32.4%
19.5%
2011 Power Plant Simulation Conference
ANO1 Rod Withdrawal
ANO1 Simulator/Plant Data ComparisonRod Withdrawal and Reactor Trip 4/25/10
-12.00
-10.00
-8.00
-6.00
-4.00
-2.00
0.00
2.00
4.00
0.00 3.00 6.00 9.00 12.00 15.00
Minutes
RX
08
- S
CA
LE
D N
EU
TR
ON
ER
RO
R (
PP
AS
)
Simulator Plant 4/25/2010
2011 Power Plant Simulation Conference
ANO1 Rod Withdrawal
ANO1 Simulator/Plant Data ComparisonRod Withdrawal and Reactor Trip 4/25/10
0.00
10.00
20.00
30.00
40.00
50.00
60.00
0.00 3.00 6.00 9.00 12.00 15.00
Minutes
N1
I5 -
RP
S-A
NI-
5 P
OW
ER
Simulator - NI5 Simulator - NI7 Simulator - NI8
Plant Results:NI‑5 20% to 29%NI‑6 remained in bypassNI‑7 33% to 50%NI‑8 32% to 48%
2011 Power Plant Simulation Conference
ANO1 Rod Withdrawal
ANO1 Simulator/Plant Data ComparisonRod Withdrawal and Reactor Trip 4/25/10
1600.00
1800.00
2000.00
2200.00
2400.00
0.00 3.00 6.00 9.00 12.00 15.00
Minutes
P1
04
1 -
RC
S P
RE
SS
UR
E {
ICC
B}
Simulator Plant 4/25/2010
2011 Power Plant Simulation Conference
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
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.