Modeling of Phenix EOL experiments
with Serpent-DYN3D
E. Nikitin and E. Fridman
Serpent UGM 2016, Milan
Text optional: Institutsname  Prof. Dr. Hans Mustermann  www.fzd.de  Mitglied der Leibniz-Gemeinschaft
Outline
• Motivation
• Phenix End-of-Life core
• Serpent-DYN3D codes sequence
• Experiments and selected results
– Control rod S-curves
– Control rod shift tests
• Conclusions
Page 2
Motivation
• Reactor dynamics code DYN3D
–
–
–
–
3D multi-group nodal diffusion
Internal thermal hydraulic model
Multi-physics coupling (e.g., ATHLET, CFX, TRANSURANUS, etc.)
Originally developed for LWRs
• Currently under extension for SFR applications
• Verification and validation is needed
– Phenix EOL control rod withdrawal experiments
Page 3
Phenix EOL core
Radial layout
Axial layout
Power, MWth
Inner and outer core
Blanket
Primary and secondary control
Reflectors
Sodium plenum
Page 4
Inlet/Outlet temp, C
560
400/560
Fissile core diameter, m
1.50
Fissile core height, m
0.85
Fissile core volume, m3
1.51
Serpent-DYN3D codes sequence
Page 5
Calculation methodology
• Full core nodal diffusion solution with DYN3D
• Homogenized few-group cross sections (XS) for DYN3D
– Using Serpent
– 24 energy groups (subset of ECCO-33)
– 2D and 3D lattice based models (next slides)
• Additional XS correction
– To improve nodal diffusion solution
– Superhomogenization (SPH) factors
• CRs, first row of blankets, inside reflectors
• Reference
– Full core Serpent solution
– Measurements
Page 6
Serpent models for XS generation
• Fuel material – 3D sub-assembly model
Page 7
Serpent models for XS generation
• Non-multiplying regions – 2D super-cell model
• Blankets and Control rods
• Homogenized assemblies, Inside reflectors and Diluent
Page 8
Experiments and selected results:
Control rod S-curves
Page 9
CR withdrawal – Off-power tests
CR #4
Measurements
• Control rod worth
• Low power (~50 kW)
• Balancing method
CR #1
Page 10
Balancing method for Serpent and DYN3D
kcrit  klow zcrit  zlow

ktop  klow ztop  zlow
• Matlab script for automatization
k-eff
ktop
• Criticality search with CR movement
kcrit
klow
zlow
zcrit ztop
• S-curve calculation
Level (mm)
– Start with two k-eff calculations: rodded and unrodded
– Linear approximation for the next CR position
– Several full core calculations
– Starting with poor statistics for acceleration
– Improve statistics when 3σ confidence intervals overlap
• Calculation time (AMD 64x2300 MHz): ~1 day for 10-point S-curve
Page 11
Control rod #1 S-curve
Serpent
DYN3D
Measured
(pcm)
CR worth
Diff. (pcm)
CR worth
Diff. (pcm)
1257
1331
74
1376
119
1400
Measured
Serpent
DYN3D w/ SPH
1200
CR worth (pcm)
1000
800
600
400
200
0
0
100
200
300
400
500
600
700
SCP1 position (mm)
Page 12
800
900
1000
Control rod #4 S-curve
Serpent
DYN3D
Measured
(pcm)
CR worth
Diff. (pcm)
CR worth
Diff. (pcm)
1238
1315
77
1309
70
1400
1200
Measured
Serpent
DYN3D w/ SPH
CR worth (pcm)
1000
800
600
400
200
0
0
100
200
300
400
500
600
700
SCP4 position (mm)
Page 13
800
900
1000
Experiments and selected results:
Control rod shift tests
Page 14
CR withdrawal – On-power tests
CR #4
*
CR #1
* Fig. 13 was extracted from the final benchmark report
Page 15
CR withdrawal – On-power tests
Measurements
•
Sodium outlet temperature
•
Thermocouples at outlet (120 S/As)
•
Flow rate remained constant
•
Power shape perturbations from:
𝑃𝑖 = 𝑚𝑖 ∙ 𝐶𝑝 𝑁𝑎 ∙ 𝑇𝑜𝑢𝑡 − 𝑇𝑖𝑛
Page 16
Core description deficiencies
•
Average core description
– Materials
– Burnup
– Temperatures
• 𝑃𝑖 = 𝑚𝑖 ∙ 𝐶𝑝 𝑁𝑎 ∙ 𝑇𝑜𝑢𝑡 − 𝑇𝑖𝑛
* Fig. 12 and 30 were extracted from the final benchmark report
Page 17
Core reactivity during all steps
Reference
1200
1000
Serpent,
pcm
DYN3D,
pcm
Difference,
pcm
800
Reference
state
843
790
-53
Step 1
874
771
-103
Step 2
894
815
-79
400
Step 3
886
822
-64
200
600
0
Page 18
Step 1
Step 2
Step 3
Radial power distribution: DYN3D vs. Serpent
Core
Page 19
Average relative difference, %
Maximal relative difference, %
DYN3D vs. Serpent
DYN3D vs. Serpent
Reference state
0.33
1.15
Step 1
0.29
1.03
Step 2
0.34
1.15
Step 3
0.35
1.19
Blanket
Average relative difference, %
Maximal relative difference, %
DYN3D vs. Serpent
DYN3D vs. Serpent
Reference state
1.56
4.45
Step 1
1.48
4.32
Step 2
1.57
4.73
Step 3
1.57
4.63
Radial power distribution: DYN3D vs. Serpent
4
Serpent
DYN3D
3.5
Power, MW
3
2.5
2
1.5
1
Inner core
Outer core
Blanket
0.5
0
0
20
40
60
80
100
120
SA number
140
160
180
200
1.08
DYN3D/Serpent power
1.06
1.04
1.02
1
0.98
0.96
Inner core
0.94
Page 20
0
20
40
Outer core
60
80
100
120
SA number
Blanket
140
160
180
200
Radial power distribution: Step 2
Note: The detailed core description was only available for CEA.
Page 21
Power deviation distribution
+14.8
0.9
1.8
2.6
3.2
3.8
4.2
4.6
4.5
4.8
5.0
4.6
5.1
5.4
5.4
5.4
5.5
5.6
6.2
5.5
5.7
5.4
5.4
5.3
5.9
5.6
5.3
5.2
5.2
1.4
3.9
5.3
0.5
3.0
1.9
5.2
4.9
4.9
5.1
3.6
4.5
4.5
4.6
5.0
-1.6
5.3
5.2
5.1
-2.7
2.7
2.0
3.1
3.7
4.6
4.1
4.4
3.9
4.7
2.1
2.9
3.5
4.1
2.2
2.8
3.3
3.7
2.2
2.7
3.2
6.1
7.1
-6.2
-6.4
-6.3
-7.0
+5.9
-7.5
-8.0
9.5
+3.0
-8.0
10.2
-7.6
0.0
10.7
-8.1
-8.4
-6.4
-6.1
-4.2
-5.2
11.6
10.5
10.1
-4.2
-5.9
9.7
-2.9
-1.9
13.0
8.9
-0.7
2.2
0.3
6.3
7.2
2.5
4.2
5.4
0.8
2.4
3.8
6.9
4.8
6.3
4.5
7.3
1.1
2.4
3.5
-11.8
5.2
2.3
1.3
2.4
3.4
4.2
1.4
2.4
3.2
-14.8
Page 22
5.1
6.2
8.2
1.7
7.9
7.7
9.0
-8.9
-2.2
8.8
8.9
9.0
-3.2
-3.3
5.0
10.8
11.0
10.0
4.0
10.4
14.8
10.6
10.3
12.4
-3.2
1.8
+8.9
-7.2
-7.0
-6.1
-4.7
0.2
-6.2
-6.8
-8.1
2.7
3.6
-8.0
-8.2
-8.1
-7.7
3.0
6.8
0.9
-5.8
-5.2
-2.3
-0.0
7.8
14.5
-4.4
-4.0
-0.2
0.1
-5.1
-3.6
2.1
12.3
-3.0 11.1
-5.3
1.4
3.7
7.9
11.4
-2.1
-0.5
-0.7
+11.8
-3.9
-3.1
-2.3
5.9
11.1
-2.8
-0.8
2.8
10.3
11.1
10.9
0.6
4.6
9.4
11.3
-6.9
-5.6
9.0
10.1
-1.3
-2.0
-0.8
2.2
6.4
7.9
10.7
-7.4
-7.1
6.6
9.8
-0.8
3.8
5.3
7.9
8.8
-8.2
-8.9
7.9
8.6
-7.7
3.1
+14.8
-1.8
0.4
1.7
4.5
5.9
6.9
-7.2
-7.8
-8.5
-10.2
-9.2
-12.1
-9.7
-7.4
-11.4
-8.9
-8.1
-3.0
-6.9
-3.5
-6.0
-4.0
-1.1
-4.1
0.9
-2.2
-0.4
1.0
-1.1
0.2
-1.5
1.3
0.7
-0.8
0.2
1.0
1.7
-7.9
2.4
5.0
-6.3
-4.3
-1.9
0.3
5.0
+8.9
-5.4
-5.3
-4.3
-5.9
4.6
5.8
-4.5
-5.0
-2.5
1.1
3.8
-4.0
-3.4
-0.3
2.9
4.5
6.2
-2.7
-2.2
1.3
2.7
-3.4
-1.8
3.0
5.3
5.4
5.6
5.4
2.3
4.1
5.0
5.1
5.6
5.5
-0.6
0.8
1.4
+11.8
-2.3
-1.5
-0.6
4.0
5.2
5.4
-1.3
0.5
3.0
4.6
4.9
5.2
5.3
1.4
2.5
0.2
-0.6
0.4
3.4
4.1
4.8
5.0
5.2
2.9
3.6
4.2
0.3
1.2
2.1
+14.8
-0.5
3.4
-8.7
-8.9
-9.5
+5.9
-9.2
-10.1
-11.7
-10.9
-9.9
-13.6
-10.6
-11.3
-9.8
-8.5
-13.0
-10.1
-10.5
-9.9
-9.1
-4.7
-8.7
-8.9
-5.7
-7.9
-8.2
-6.0
-7.5
-3.5
-6.1
-7.1
-1.1
-4.2
-6.0
-2.2
-6.0
-0.5
-2.9
-4.7
-1.4
-3.2
-4.9
0.1
-3.6
-0.6
-2.4
-1.3
-0.2
0.7
4.3
4.9
-9.4
-6.2
-9.7
-9.1
-9.8
5.8
6.5
-9.4
0.07.0
+3.0
5.3
6.1
-7.9
-7.1
7.2
-3.0
7.4
7.5
7.9
6.8
6.4
-5.9
8.9
6.3
5.9
-8.9
5.1
-11.8
1.6
0.2
1.9
3.3
0.1
3.2
1.2
2.6
1.1
-3.6
-2.8
0.3
-3.6
-5.9
-3.2
-3.3
-3.0
-2.0
-3.0
-3.8
-2.6
-8.9
-2.3
-1.0
-0.4
0.2
-3.8
-3.8
-2.9
-1.8
-0.4
0.9
-3.9
-3.6
-2.9
-2.4
0.0
-4.0
-3.9
-3.6
-2.9
-1.1
-4.1
-4.0
-3.9
-3.3
-2.1
-1.3
-0.5
-4.1
-4.0
-3.7
-1.6
0.3
1.7
-3.8
-2.1
+3.0
-4.1
-4.2
-4.1
-4.0
-1.9
-0.7
0.3
3.6
-4.3
-0.7
1.6
2.5
-4.1
-4.1
-4.2
-4.4
-4.0
+5.9
-4.0
-4.0
-4.2
-4.5
-3.1
-1.0
-3.9
-4.0
-4.0
-4.1
-3.2
2.0
3.9
4.5
-1.5
4.9
5.1
5.3
-1.7
2.9
3.8
-3.9
-4.2
-3.4
2.0
7.5
9.3
5.3
-3.7
-2.5
-0.5
-3.8
-3.8
-3.9
-3.8
7.4
7.2
-3.6
+8.9
-3.6
-3.7
-3.7
-3.7
-1.6
11.1
7.0
-3.1
0.3
8.6
-3.5
-3.5
-3.4
-3.2
-2.2
3.4
10.8
-3.1
-0.9
3.8
6.6
7.7
6.6
-1.0
-0.0
1.7
-3.3
-3.0
-2.0
4.1
7.4
-2.5
-1.9
-0.1
+11.8
-3.0
-2.7
-2.6
1.2
5.7
6.4
7.5
-1.2
-0.3
2.7
4.2
-2.6
-2.3
-1.8
0.7
3.1
7.0
-8.7
0.4
1.9
4.3
5.1
-1.8
-1.2
-0.4
1.4
2.5
-2.2
-1.8
-1.3
-11.8
-0.9
-14.8
-14.8
Step 1
Serpent / DYN3D
Step 2
Serpent / DYN3D
Step 3
Serpent / DYN3D
Max. positive dev.
+6.23 / 6.22%
+14.78 / 15.23%
+11.07 / 11.35%
Max. negative dev.
-12.08 / 12.19%
-13.61 / 13.90%
-4.52 / 4.66%
Radial power deviation profile: Step 2
Page 23
Conclusions
• The Phenix EOL CR withdrawal benchmark was calculated
• DYN3D nodal diffusion solution
– XS generated with Serpent
– SPH factors were used for first neighbor nodes facing fuel assemblies
– Full core Serpent solution as reference
• Very good agreement between DYN3D and Serpent in general
• Good agreement for CR S-curves between DYN3D and experiment
• CR shift tests
– Good agreement: Serpent-DYN3D vs. other benchmark participants (CEA)
– High discrepancies compared to experiment due to averaged core model
Page 24
Thank you
(registration number 150 1462)
Page 25