[fluka-discuss]: Scoring ambient dose​ rate; deviation fro​m MCNP-results

From: Alexander Götzelmann (alexander.goetzelmann_at_hs-furtwangen.de) <(alexander.goetzelmann_at_hs-furtwangen.de)>
Date: Thu, 2 Jul 2015 13:07:00 +0200 (CEST)

Thank you a lot for your help. Sorry for my late reply, yesterday I was out of

The results should be deemed correct, because the TÜV* simulated the same model
with the same input-data. The results of MCNP and the TÜV-results are identical.

I find some mistake in my input: I accidently used a wrong material-mixture for
the the filling of the barrel (the Region "BORSAE" in the Input I sent you in
the previous mail is now changed to Region "SCHROTTC" with a new
material-mixture). Now the ambient dose rate is a bit lower because of the
higher self-shielding. But the FLUKA results are still higher by a factor of
approximately 3 to 4.

In MCNP I used the ICRP116 dose conversion coefficients for photons. FLUKA uses
the ICRP74. The dose conversion coefficient of ICRP74 for the energy of Co-60 is
higher by a factor of 1,3. So the difference of this two data bases can't
explain the huge deviation.

If you look in the MCNP-Input-File you will see that I used a source, which
consists of the two radioisotopes Co-60 and Cs-137 with the ratio 75:25. In
FLUKA I make two runs (one with Co-60 and the other one with Cs-137) and
calculate the total ambient dose rate by hand. Because of the lower energy ,
Cs-137 doesn't contribute to the ambient dose rate outside the barrel (My runs
approve this). So a run in FLUKA with just Co-60 should be match with the

The source (mixture of Co-60 and Cs-137) has an activiy of 1E11 Bq.

In the attachment you find the MCNP-Input-File and my new FLUKA-Input-File.
And yes, I used the f4-tally in MCNP.

thank you,

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Received on Thu Jul 02 2015 - 14:49:46 CEST

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