Archive for September, 2019

Some questions concerning Shielding calculations in Nucleonica using Cm244 and W

September 16th, 2019

(Qu.) LH JRC, Karlsurhe, Germany
Dear Nucleonica Team,
May I ask you some question about shielding calculation using Nucleonica?
I want to shield a Cm244 source using Tungsten. Unfortunately I get some strange results, using both the older Dosimetry & Shielding calculation and the newer Dosimetry & Shielding H*(10) apps. The Tenth value shield thickness of these 2 methods do not match: They are a factor 10 different, which I consider far too much.

(Ans. Nucleonica Team)
Please note that the newer D&S H(10) includes the high energy prompt gammas.
The older D&S does not. You can see this in the graph at the bottom of the page. The D&S H(10) contains groups of gammas in the range 1-10 MeV. You can also see this is more detail in the datasheets.
Cm244Although the BR for SF is low (1e-6), the emission probabilities for the low energy gammas is also low. Hence these high energy gammas need to be accounted for in the calculations.

Note also that the high energy gammas are included only in the JEFF3.1 database. Other databases (e.g. ENDF/B) do not have these high energy gammas. The database can be changed in the D&S H(10) Options menu.
The contribution of individual gamma energies can be investigated using the “photons/s” in the source strength drop-down menu. There one can see that it is the higher energy gammas which make the difference.

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