Localized Asymmetry in FLUKA Activation Results

Scoring
1

Versions

Please provide the used software versions.

FLUKA:4-5.1
Flair:3.4-5.2

Description

Hello,

I am comparing FLUKA and MCNP activation results for several Au regions placed symmetrically around a central axis.

Since the source is expected to produce a mostly symmetric neutron field, I would also expect similar activation values at the corresponding symmetric positions. Interestingly, 5 out of the 6 positions give results reasonably consistent with MCNP, but the region at ΔY = −2.5 cm consistently gives a noticeably lower value.

I am wondering what could cause such a localized asymmetry. Could there be something specific in the FLUKA geometry, source definition, or scoring that I should check?

I attach the plot showing the different positions and results.

Thank you for your feedback.

image
image1647×1002 196 KB

Input files

Simple.flair (9.1 KB)

Dist1_22_tab.lis (61.2 KB)

source.f (80.0 KB)

3

Dear Carlos Eduardo Vítor,

The error bars for your comparison with MCNP are not very small. Perhaps you do not have an agreement within 1-sigma, but within 2-sigma it seems you have. Perhaps when doing another simulation or running more primaries you would get closer to the MCNP results.

Also, I suggest you use this routine for generating a random isotropic direction:
call sample_isotropic_direction( direction_cosx, direction_cosy, direction_cosz )

It would perhaps simplify your routine. Also, it would exclude an error in the generation of the direction vector.

Let me know if it solves your problem.