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Activation Analysis
A comparison between FLUKA and FISPACT
results
Pavia, 16 - 12 - 2014
Gabriele FirpoReactor and Safety Dept. Phone: [email protected]
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• Background – The Activation Analysis approach in:
• FLUKA • FISPACT
• Comparison between FLUKA and FISPACT calculations:
• Methodology• Results
• Summary and Conclusions
CONTENT
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DEFINITION
Activation Analysis
In the framework of this presentation, it is intended as, and limited to:
The evaluation of the total activity concentration of a material slab being irradiated by monoenergetic projectile particles.
The evaluation of other physical quantities, related to the «activation analysis» as typically intended, like:• Nuclide inventories at different cooling times;• Corresponding radiation fields following the material activationare actually foreseen as a FLUKA/FISPACT comparison issue, but they are out of scope of the present analysis.
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The Bateman Equations
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THE ACTIVATION ANALYSIS APPROACH IN
FLUKA AND FISPACT
Item FISPACT FLUKA
Method Numerical Solution of Bateman Equations
• Full Monte Carlo approach;
• «Mixed» Monte Carlo/Analytical
solution of Bateman Equations.
Geometry 0-D approach* Full 3-D approach*
Parameters of Bateman Equations
Evaluated Data (EAF libraries)
Evaluated Data / Models**
Limitations No build-upNo self-shielding
No build-up
* = See next slide**= Depending on the projectile type/energy
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• Homogeneous and isotropic irradiating flux;
• No flux attenuation: The effective
volume/mass is just a normalization factor.
• «Real» irradiating flux profile;
• Flux attenuation: The effective
volume/mass and dimensions do impact on the activation results.
Φ
x
0-D approach (FISPACT) 3-D approach (FLUKA)
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PR
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LEM
In order to compare FLUKA and FISPACT approaches, the problem is:
How to make a 0-D (FISPACT) geometrical approach equivalent to a 3-D (FLUKA) one?
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SOLUTION
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Noting that:• The 0-D (FISPACT) approach is rigid: no «degrees of
freedom» to reproduce any kind of irradiating scenario;• The 3-D (FLUKA) approach lets the user to define any kind
of irradiating scenario; many «degrees of freedom» to define it also «whatever the user likes».
It is then envisaged to:1. Define an irradiating scenario—in principle, as simple as
possible—suitable for the 0-D (FISPACT) approach;2. Define, consequently, the corresponding and equivalent
irradiation scenario in FLUKA.
HOW?
Let’s see a practical example…
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1. Fill the list of parameters to completely define a 0-D irradiation scenario in the FISPACT input files:
• Particle type t and energy E;• Homogeneous and isotropic flux Φ;• Material Mat with Volume V (or Mass M);• Irradiation time(s) Ti;• Cooling time(s) Ci.
2. Fill the equivalent FLUKA/FLAIR «decay» input file as follow:• Define an extended isotropic source of particle t with energy E; the
source region must correspond to the detector region;
• Define the material Mat with volume V in the detector region;• Define the IRRPROFI and DCYTIMES cards with the irradiation
parameters Ti and Ci. In particular, the beam intensity—WHAT(2),(4),(6) of the IRRPROFI card—must be equal to the number of particle/s causing an average total flux equal to Φ. This value can be evaluated by another dedicated FLUKA run with USRTRACK card.
OPERATIVE EXAMPLE
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CONSIDERED SCENARIOS
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Case ID Particle type
Energy Flux Target geom.
Material Irrad. Time
Cooling times
1 Proton 50 MeV 1E8 p/cm2/s
Cylinder (r=1 cm, h=1 µm)
SS316LN 90 days 0 s
2 Proton 20 MeV 1E8 p/cm2/s
Cube (1x1x1 cm3) SS316LN 15 years From 0 s
up to 20y
3 Neutron 50 MeV 1E8 n/cm2/s
Cylinder (r=1 cm, h=1 µm)
SS316LN 90 days 0 s
4 Neutron 50 MeV 1E8 n/cm2/s
Cylinder (r=1 cm, h=50 cm)
SS316LN 90 days 0 s
5 Neutron Thermal 1E8 n/cm2/s
Cube (1x1x1 cm3) Cobalt 90 days 0 s
6 Neutron Thermal 1E8 n/cm2/s
Cube (1x1x1 cm3) SS316LN 15 years From 0 s
up to 20y
Note 2: Only neutrons, protons and deuterons projectiles with energies from 0 up to ~55 MeV can be defined with FIPACT 2010 (many other particle types and higher energies, up to ~1 GeV, are available in FISPACT II by CCFE).
Note 1: Available code versions: FISPACT 2010, FLUKA 2011.2b trial.
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Case ID Total activity concentration [Bq/cm3]
Ratio FLUKA/FISPACT
FLUKA FISPACT
1 3.35E6 1.86E6 1.80
2 See graph in the next slide 0.46 (average)
3 1.55E6 1.22E6 1.27
4 9.92E5 1.22E6 0.81
5 3.47E8 4.72E8 0.74
6 See graph in the next slide 1.83 (average)
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LTS 1.00E+01 1.00E+02 1.00E+03 1.00E+04 1.00E+05 1.00E+06 1.00E+07 1.00E+08 1.00E+09
1.00E+02
1.00E+03
1.00E+04
1.00E+05
1.00E+06
1.00E+07
SS316LN Total Specific Activity following 15 years of 20 MeV proton irradiation - proton flux 1e8 p/cm2/s
FISPACTFLUKA
Cooling time [s]
Tota
l Spe
cific A
ctivi
ty [B
q/cm
3]
1.00E+01 1.00E+02 1.00E+03 1.00E+04 1.00E+05 1.00E+06 1.00E+07 1.00E+08 1.00E+091.00E+04
1.00E+05
1.00E+06
1.00E+07
SS316LN Total Specific Activity following 15 years of thermal neutron (2.5e-8 MeV) irradiation - neutron flux 1e8 n/cm2/s
FISPACTFLUKA
Cooling time [s]
Tota
l Spe
cific A
ctivi
ty [B
q/cm
3]
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• A methodology to make FISPACT and FLUKA activation calculations comparable has been setup;
• Several test runs have been perfomed, showing compatible results within a factor of a few.
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• The phase space of the irradiation scenario parameters has many dimensions: sensitivity analyses are envisaged to understand/find correlations (if any);
• For example, it is expected that, as the linear dimensions of the material slab increase becoming larger than the mean free path of the projectile particle, the effect of flux attenuation in energy becomes not negligible.
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QUESTIONS? COMMENTS?
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MANY THANKS
FOR YOUR ATTENTION
Pavia, 16 - 12 - 2014
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