1 Activation Analysis A comparison between FLUKA and FISPACT results Pavia, Gabriele Firpo Reactor and Safety Dept. Phone:

2 Background – The Activation Analysis approach in: FLUKA FISPACT Comparison between FLUKA and FISPACT calculations: Methodology Results Summary and Conclusions CONTENT Pavia,

3 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 activation are actually foreseen as a FLUKA/FISPACT comparison issue, but they are out of scope of the present analysis. BACKGROUND The Bateman Equations Pavia,

4 BACKGROUND THE ACTIVATION ANALYSIS APPROACH IN FLUKA AND FISPACT ItemFISPACTFLUKA MethodNumerical Solution of Bateman Equations Full Monte Carlo approach; «Mixed» Monte Carlo/Analytical solution of Bateman Equations. Geometry0-D approach*Full 3-D approach* Parameters of Bateman Equations Evaluated Data (EAF libraries) Evaluated Data / Models** LimitationsNo build-up No self-shielding No build-up * = See next slide **= Depending on the projectile type/energy Pavia,

5 BACKGROUND 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) Pavia,

6 PROBLEM 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? Pavia,

7 SOLUTION METHODOLOGY 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… Pavia,

8 METHODOLOGY 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) T i ; Cooling time(s) C i. 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 T i and C i. 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 Pavia,

9 CONSIDERED SCENARIOS METHODOLOGY Case IDParticle type EnergyFluxTarget geom. MaterialIrrad. Time Cooling times 1Proton50 MeV 1E8 p/cm 2 /s Cylinder (r=1 cm, h=1 µm) SS316LN90 days0 s 2Proton20 MeV 1E8 p/cm 2 /s Cube (1x1x1 cm 3 ) SS316LN15 years From 0 s up to 20y 3Neutron50 MeV 1E8 n/cm 2 /s Cylinder (r=1 cm, h=1 µm) SS316LN90 days0 s 4Neutron50 MeV 1E8 n/cm 2 /s Cylinder (r=1 cm, h=50 cm) SS316LN90 days0 s 5NeutronThermal 1E8 n/cm 2 /s Cube (1x1x1 cm 3 ) Cobalt90 days0 s 6NeutronThermal 1E8 n/cm 2 /s Cube (1x1x1 cm 3 ) SS316LN15 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 b trial. Pavia,

10 Case IDTotal activity concentration [Bq/cm 3 ] Ratio FLUKA/ FISPACT FLUKAFISPACT 13.35E61.86E See graph in the next slide 0.46 (average) 31.55E61.22E E51.22E E84.72E See graph in the next slide 1.83 (average) RESULTS Pavia,

11 RESULTS Pavia,

12 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. SUMMARY And CONCLUSIONS Pavia,

13 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. HINTS QUESTIONS? COMMENTS? Pavia,

14 MANY THANKS FOR YOUR ATTENTION Pavia,