Dose Rate Calculation for a isotope point source

Dear FLUKA experts,
I have created a Iodine-131 point source 0.5 m away from a NaI detector. I need to find the dose rate by Gamma emmision at NaI detector after certain time intervals. (1h and 24h ) I used DETECT card and got count vs Energy plots. Then I tried USRBIN, AUXSCORE and DCYSCORE. I got 0.000E0 values when I used RADDECAY in semianalogous mode. But with activation study mode and IRRADIATION card
I131Activity.flair (3.9 KB)
I131Activity.inp (4.5 KB)
Im getting some values at the output file I created with OPEN card. I would like to know whether Im on the right path with correct cards. INP file and FLAIR file attached.

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Hello! Welcome and many thanks for posting your question on the forum. I will start to have a look at it as soon as possible. Please, stay tuned.

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Hello! I had the chance to check your files. I suggest a gradual approach. Please find below some resources to help you address your problem gradually.

  • Approach to activation modes:

    • Activation in FLUKA: this lecture presents the set up of semi-analogue runs
    • Discussion on raddecay modes: this post and the FLUKA manual
  • Other topics on the forum

    • Other useful post: link
    • This discussion - which includes also the mentioning of TIME-CUT card
  • Scoring:

    1. DCYSCORE settings: the already mentioned activation lecture; in case of semi-analogue mode, DCYSCORE set to -1 is needed
    2. Post involving DETECT card, if needed
  • General comments:

    • I would place a simple USRBIN scoring mesh, even in AIR, and test the RADDECAY options/radioactive source simulations
    • Then, I suggest to increase the detail of the simulation bringing back the detector. What to score, then, will depend on your specific needs (is a USRBIN sufficient, or you want to collect info about the detector response).
    • I should also suggest to run with a sufficient number of cycles (“Recommendations”, page 29 of this lecture)

I hope to have provided you with sufficient resources to guide your solution. I will be away for work in the next to weeks, so further answers might be delayed.
Good luck with your simulation.
Best regards,


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thank you Im getting results (dose rates) closer to the theoretical results I have.