# Problem in the understanding of the activation results

From: Julie Barbier <Julie.Barbier_at_iba-group.com>
Date: Thu, 25 Oct 2012 10:21:48 +0200

Dear fluka experts,

I'm actually working on the activation of a tungsten target.
My model consists in a cylindrical target of tungsten (182-W; 183-W; 184-W; 186-W) bombard with a beam of 230MeV protons.
Here are the CARDS used in my input files:
* IRRPROFI 6.24E+9 protons/sec during 1 year
* DCYTIMES from -1year to 1year
* RESNUCLEi to score residual nuclei produced
* RESNUCLEi card coupled with the times of DCYTIMES to perform radioa=
ctive decay of the residual nuclei

My results don't seem consistent to me. Indeed, in the output files, RESNUCLEi card give me the yield
(nuclei/cm^3/pr) of all the radionuclides in presence and RESNUCLEi+DCYTIMES give me the activity
(Bq/cm^3) from these isotopes.
If I focus on one nuclide : tungsten 181, for example :
The yield done by Fluka is 2.72E5 nuclei/cm=B3/pr. If I use this yield with the radioactive growth equation, the saturation activity
(time tends to in=
finite) equals to 1.70E5 Bq/cm^3 and the activity after 1year of irradiation equals to 1.49E5 Bq/cm^3.
After1 year of irradiation the activity provided by Fluka is 1.91E5 Bq/cm^3.
I tought that normaly A(1year fluka) = A(1year calculated) and A(saturation calculated) > A(1year)
I cannot figure out why does my calculations differ from the Fluka results.

In a second time I changed the irradiation interval of IRRPROFILe from 1 year to 10 minutes. The results for tungsten 173 are :
Calculations via the yield done by fluka : A(saturation) = 2.06E4 Bq/cm^3 and A(10 minutes) = 1.23E4 Bq/cm^3
Fluka result for the activity at 10 minutes : 8.47E6 Bq/cm^3
In this case, A(saturation calculated) > A(1year) but A(1year fluka) still not equals to A(1year calculated)!

That would be great to have you help on this issue !

Julie
Received on Sat Oct 27 2012 - 00:25:27 CEST

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