Dose from activated material

Scoring
1

Dear Fluka experts,
I’m currently trying to run a simulation about the activation of SiC. I’m interested in scoring the equivalent of dose after some time from the end of the irradiation (made by neutrons along a period of 30 days, coming from 4 different directions). In the attached file, there is a picture i made taking result from the RESCNUCLEi detector for different cooling times. As it can be noted, after about 5 days there are basically no more radioactive elements. The same cannot be said about the dose rate, for which I’ve posted in the attached file what I obtained for cooling times of 5 and 10 days, and even 1 year. The dose rate seems to decrease linearly, but what is really confusing me is that I’m getting very high values even at 10 days, when i should have not any radioactive material (even at 1 year from irradiation the values are still pretty high). Is fluka evaluating something that I’m not aware of, or have i put something wrong in my input file? Thank you for your attention. Best regards,
Leonardo
neutron_spectrum.txt (2.9 KB)
numerical_exercise.flair (6.0 KB)
source_newgen.f (10.4 KB)

Picture1
Picture12507×1330 125 KB

1year.jpeg
5days.jpeg
10days.jpeg

2

Dear Leonardo,

many thanks for your question. Based on the simulation files that you have sent, the high dose rates at long cooling times are due to the production of Cr-51 by neutron capture on Cr-50 (~ 4.3% isotopic abundance) in the chromium coating layer. To estimate this contribution, you can add a residual nuclei scoring (which, contrary to USRBIN, is a region-based estimator) in the coating layer as well.

I hope this helps.
Let me know in case you have further questions.

Best,
Davide

3

Dear Davide,
I didn’t think that such a thin layer of Cr could produce this effect. Thank you very much for your reply!
Best regards,
Leonardo

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