1. Overview of Serpent related activities at HZDR E. Fridman

2. Outline
“Typical” applications
Generation of few-group constants

3. EU/FP7 FREYA FREYA - Fast Reactor Experiments for hYbrid Applications
Support for design and licensing of MYRRHA/FASTEF
Modeling of MYRRHA and ALFRED critical mock-ups
VENUS-F facility at SCK•CEN, Mol

4. Very detailed VENUS-F facility data and model
V&V of Serpent against MCNP and experimental data
k-eff, β-eff, control rod worth
Radial and axial traverses
Detector responses and spectral indices (e.g. F8/F5)

5. Serpent vs. MCNP: Integral parameters
Difference
value
error
k-eff
13 (pcm)
Gen. time, sec
4.018E-07
0.2%
4.010E-07
0.1%
-0.2%
Beta-eff, pcm
728 2
731 1
3 (pcm)
Performance
Executed using 4 MPI tasks with 16 OpenMP threads
Serpent runs 9.3 times faster than MCNP

6. Serpent vs. MCNP: difference in flux spectra

7. EU/FP7 ESNII+ Modeling of ASTRID SFR
Evaluation of neutronic parameters and safety coefficients
Code-to-code benchmarks
Radial layout
Axial layout

8. OECD/NEA: SFR Benchmark Task Force
Analysis of feedback behavior of next gen. of SFRs
Code-to-code benchmarks
Large oxide SFR core

9. Common issues Nuclear data uncertainties
Δρ 500 – 600 pcm between JEFF-3.1 and ENDF/B-VII
For both ASTRID and large oxide SFR
Uncertainties propagation to low-worth reactivity coefficients

10. Common issues Nuclear data uncertainties
Δρ 500 – 600 pcm between JEFF-3.1 and ENDF/B-VII
For both ASTRID and large oxide SFR
Uncertainties propagation to low-worth reactivity coefficients
Example of Serpent setup for ASTRID analysis:
200 skipped + 1k active cycles + 500k neutrons= 0.5×109 histories
σk-eff = ±3 pcm (0.003%)
Q: Is it enough to get “good” reactivity coefficients?

11. Uncertainty in reactivity coeff.: ASTRID core

12. Proposal for follow-up benchmark
Benchmark for uncertainty analysis in modelling (UAM)
Within OECD/NEA WPRS
Evaluation of uncertainties on reactivity feedback coefficients
Analyses of principal unprotected transients
Using the results from the previous step
First SFR-UAM meeting is planned for (UPM, Madrid)
In conjunction with other OECD/NEA workshops

13. Generation of SFR few-group constants

14. Generation of SFR few-group constants
MC is too expensive for full-scale reactor calculations
Neutronics + TH + BU + kinetics
Two-step procedure still dominates reactor analysis
Deterministic 2D lattice codes  homogenized constants
Deterministic 3D coarse mesh core simulators
Increasing interest in using MC for homogenization
Improved computer performance
Flexibility - not limited to any particular technology
Especially useful for the modeling of innovative reactor concepts

15. Application example: large oxide SFR core
OECD/NEA SFR Benchmark
Fuel: 225 inner and 228 outer subassemblies
Control: 18 primary and 9 secondary subassemblies

16. Verification of XS generation methodology
3D full core calculations
At BOL
DYN3D
Multi-group diffusion solution
Serpent:
Reference solution
Few-group XS for DYN3D
Compared parameters:
k-eff
Doppler constant
Coolant void reactivity
Control rod worth
Radial power distribution

17. 3D single-assembly model for fuel assemblies
Reflective radial and black axial boundary conditions

18. 2D super-cell models for non-multiplying regions
Control rods, control rod channels, reflectors, etc

19. Results: integral core parameters
Serpent,
pcm
DYN3D vs. Serpent, pcm
Reactivity - CR out
1059
-128
Reactivity - CR in
-4988
-255
Total CR worth
-6046
-127
Doppler constant
-852
-15
Na void reactivity
1864 87

20. Results: integral core parameters
Serpent,
pcm
DYN3D vs. Serpent, pcm
Reactivity - CR out
1059
-128
Reactivity - CR in
-4988
-255
Total CR worth
-6046
-127
Doppler constant
-852
-15
Na void reactivity
1864 87

21. SPH factors for CRs and CR channels
SPH = Super-homogenization
Typically used for pin-wise homogenization in LWRs
Requires equivalent transport/diffusion model
SPH = μ = ϕSerpent ϕDYN3D and Σ* = μ*·Σ
For every homogenized region and energy group
Q: How to make equivalent model for hexagonal supercell?

22. SPH factors for CRs and CR channels
SPH = Super-homogenization
Typically used for pin-wise homogenization in LWRs
Requires equivalent transport/diffusion model
SPH = μ = ϕSerpent ϕDYN3D and Σ* = μ*·Σ
For every homogenized region and energy group
Q: How to make equivalent model for hexagonal supercell?

23. SPH factors for CRs and CR channels
DYN3D has a trigonal diffusion solver
SPH were generated as follows: → →
Serpent model
Homogenized regions
Σ and ϕSerpent
DYN3D Δ diffusion
ϕDYN3D

24. Results: integral core parameters
Serpent,
pcm
DYN3D vs. Serpent, pcm
Reactivity - CR out
1059
-128
Reactivity - CR in
-4988
-255
Total CR worth
-6046
-127

25. Results: integral core parameters
Serpent,
pcm
DYN3D vs. Serpent, pcm
DYN3D + SPH vs. Serpent, pcm
Reactivity - CR out
1059
-128
-64
Reactivity - CR in
-4988
-255
-107
Total CR worth
-6046
-127
-43

26. Ring-wise power distribution
CR out
CR in
w/o SPH: max. diff. 0.6%
w/o SPH: max. diff. 4.8%

27. Ring-wise power distribution
CR out
CR in
w/o SPH: max. diff. 0.6% w/ SPH: max. diff. 0.4%
w/o SPH: max. diff. 4.8% w/ SPH: max. diff. 2.1%

28. Assembly-wise power distribution

29. Re-homogenization with Serpent

30. Thank you!