A lightning strike near the Prairie Island nuclear power plant switchyard caused a generator/turbine trip on Unit 2. The MAAP4.0.6 code was used to simulate and benchmark the plant's predicted post-trip response against actual plant data recorded by the plant computer. While the simulation did not include some operator interventions, it showed good agreement with trends in steam generator pressure and level compared to the recorded plant computer data in the first 20 minutes following the trip.

1. MAAP4.0.6 Benchmark of Unit Trip at
Prairie Island 2 – May 9, 2011
Dr. John H. Bickel

2. On May 9, 2011 a lightning strike near the Prairie Island
switchyard caused a Generator/Turbine Trip on Unit 2
The momentary power disturbance did not
result in a loss of offsite power and the
ERCS plant computer recorded data
throughout the event.

3. Purpose of this Benchmark:
• Compare MAAP4.0.6 predicted post-trip response to the
actual Unit 2 trip that occurred on May 9, 2011
Background:
• MAAP4.0.6 simulation set to replicate unit trip with
minimal operator interventions during the first 20 minutes
• Actual plant parameter response was recorded via plant
computer
• Operators actually took manual control of charging and
letdown which was not reflected in MAAP simulation

4. MathCAD15 used to read and plot
MAAP4.0.6 d31-d48 plot files

5. Example Data from Plant Computer

6. MathCAD15 also used to read and plot
Plant Computer Data Arrays

7. Steam Generator A Pressure vs. Level
Steam Generator A Pressure vs WR Steam Generator Level
Steam Generator Pressure (psia) vs Steam Generator Level (ft) 1.110
3
70
3
1.110 44
42
3
110
3 110
Steam Generator Pressure (psia)
NR Steam Generator Level
Steam Generator Level (ft)
Steam Generator Pressure
60
40
PUS 900 ZWUS SGAPress 900 SGAWRLevel
38
50
800
800
36
700 34
0 0.1 0.2
700 40
time 0 0.1 0.2
timeE
Time in Hours
time in Hours
MAAP4.0.6 Simulation Data Recorded by Plant Computer

8. SG A Feedwater/Steam Flow vs. Level
Steam Generator A: Feed/Steam Flow vs WR Steam Generator Level
Steam Generator Feed/Steam Flow vs Steam Generator Level (ft) 70
6
410 44
42 6
6 310
310
Steam Generator Feed/Steam Flow
NR Steam Generator Level
Steam Generator Level (ft)
60
Feed/Steam Flow
40
FWAflow
WFWU 6
6 210 SGAWRLevel
210 ZWUS STAflow
WGUST
38
50
6
6
110 110
36
0 34 0 40
0 0.1 0.2 0 0.1 0.2
time timeE
time in Hours time in Seconds
MAAP4.0.6 Simulation Data Recorded by Plant Computer

9. Steam Generator B Pressure vs. Level
Steam Generator Pressure (psia) vs Steam Generator Level (ft) Steam Generator B Pressure vs WR Steam Generator Level
3
3 1.110 70
1.110 44
42
3
110
3 110
Steam Generator Pressure (psia)
Steam Generator Level (ft)
NR Steam Generator Level
Steam Generator Pressure
60
40
PBS 900 ZWBS SGBPress 900 SGBWRLevel
38
50
800 800
36
700 34
0 0.1 0.2 700 40
0 0.1 0.2
Time
timeE
Time in Hours
time in Seconds
MAAP4.0.6 Simulation Data Recorded by Plant Computer

10. SG B Feedwater/Steam Flow vs. Level
Steam Generator Feed/Steam Flow vs Steam Generator Level (ft) Steam Generator B: Feed/Steam Flow vs WR Steam Generator Level
6 70
410 44
42
6
310
6 310
Steam Generator Feed/Steam Flow
NR Steam Generator Level
Steam Generator Level (ft)
60
Feed/Steam Flow
40
WFWB FWBflow
6 6
210 ZWBS 210 SGBWRLevel
WGBST STBflow
38
50
6
110 6
110
36
0 34
0 0.1 0.2 0 40
0 0.1 0.2
time
timeE
time in Hours
time in Seconds
MAAP4.0.6 Simulation Data Recorded by Plant Computer

11. A,B Auxiliary Feedwater Flow
SG A/ B: Auxiliary Feedwater Flow vs NR Steam Generator Level
5
AFW Mass Flow (lb/hr) vs CST Inventory (lbs) 210
5 6
210 310
5
5 1.510
1.510
Auxiliary Feedwater Flow
6
210
AFW Mass Flow (lb/hr)
CST Inventory (lbs)
WAFWU SGAAFWMFlow
5 5
110 MWCST 110
WAFWB SGBAFWMFlow
6
110
4
510 4
510
0 0
0 0.1 0.2
0
Time 0 0.1 0.2
Time in Hours timeE
time in Seconds
MAAP4.0.6 Simulation Data Recorded by Plant Computer

12. Reactor Coolant Temperature vs. Flow
RCS Temperatures (F) vs time
600 RCS A Loop Temperatures vs Loop Flow
600
580
580
7
310 7
310
Core Mass Flow Rate (lbs/hr)
Loop Mass Flow Rate (lbs/hr)
RCS A Loop Temperatures
RCS Temperatures (F)
560 560
TWHPS RCAHotLegTemp
Tavg 7 RCATavgTemp 210
7
210 WCORE RCAMFlow
TWLPS RCAColdLegTemp
540 540
7
7 110
110
520
520
500 0
0 0.1 0.2
500 0
0 0.1 0.2 timeE
Time
time in Seconds
Time in Hours
MAAP4.0.6 Simulation Data Recorded by Plant Computer

13. Pressurizer Pressure vs. Level
Pressurizer Pressure vs Pressurizer Level
Pressurizer Pressure (psia) vs. Level (ft) 3
2.310 30
3
2.310 30
Pressurizer Pressure (psia)
3
2.210
3
20 2.210 20
Pressurizer Level (ft)
Pressurizer Pressure
Pressurizer Pressure
Pressurizer Level
PPZ ZWPZ PZRPress PZRNRLevel
3
2.110 10 3
2.110 10
3
210 0
0 0.1 0.2 3
210 0
time 0 0.1 0.2
Time in Hours timeE
time in Seconds
MAAP4.0.6 Simulation Data Recorded by Plant Computer

14. Charging/Letdown Flow vs. PZR Level
ESF and Charging Makeup Flow (lbs/hr) vs. RWST Level (ft) RCS Letdown/Charging Flow vs Pressurizer Level
69 60 30
4
610
ESF and Charging Makeup Flows (lbs/hr)
68.95
RCS Letdown/Charging Flow
40 20
RWST Level (ft)
Pressurizer Level
4
410
WESFDC RCSLetdownFlow
68.9 ZWRWST PZRNRLevel
WESFCL RCSChargFlow
20 10
4
210
68.85
0 68.8 0 0
0 0.1 0.2 0 0.1 0.2
time timeE
Time in Hours time in Seconds
MAAP4.0.6 Simulation Data Recorded by Plant Computer