The problem in "Geometry"

Dear experts,
I’m doing the radiation shielding simulation of a treatment room, and there are some problems in “Geometry”.
The concrete I built on the second floor(r2)is blank in “Geometry”. I want to know the reasons for this situation and how to solve this problem?
And “Errors found” is displayed in “Geometry”, but I didn’t find any errors in the geometric model after checking the input file. How should I solve them?

2021.5.6.flair (3.4 KB)
2021.5.6.inp (3.4 KB)

Dear Junjie,

we only can provide support for FLUKA and Flair released by CERN at .

Please install these versions and if the problem still present, please let us know.


Your geometry is incomplete. You are missing the external black hole region enclosing your geometry to kill particles when the exit.
I presume you automatically generated your input by importing an mcnp file,
I would recommend to download the new flair v3 which has better conversion from mcnp, and if the problem persists there are additional automatic tools inside the new flair to help you correct the problem.

Dear expert,
I put the treatment room within the black hole according to your suggestion, but the spliced concrete area (r1) still shows errors. Is there something wrong with my geometry input?
Could you look at my input file again and tell me how to solve this problem?

2021.5.7.flair (3.4 KB)
2021.5.7.inp (3.4 KB)

Dear Junjie,

Your region r1 is not well defined.
Instead of defining it like this:
r1: +b1 +b2 … +b14

You should define them in different zones and do the union of them, like this:

r1: +b1 | + b2 | … | +b14

This should solve your problem



A bit of info to complement the answer:

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Dear expert,
Thank you very much for your answer.
I revised it according to your suggestion, and my problem was solved. But I still have some doubts, why do I only need to modify r1, and do not need to modify R2 and R3 without affecting the geometric model?
And I found that my simulation can’t work normally in “RUN”. Can you help me find out why?
2021.5.10.flair (2.7 KB)
2021.5.10.inp (3.2 KB)

Your input needed a few small corrections and it runs normally.
Please find attached the modified project file with your input
2021.5.10.flair (4.6 KB)
I’ve added a GLOBAL card and some PHYSICS cards.
Also note that your input name contains “.” in the filename and the previous fluka versions cannot handle it.

and a couple of plots of the results

Dear @Junjie_Zhang,

Related to your questions:

“why do I only need to modify r1, and do not need to modify R2 and R3 without affecting the geometric model?”

The slides 4 and 12 give you the answer.

Basically, when you were trying to define your region r1 you had this:

r1: +b1 +b2 + … +b14

What does it mean? You can see it like being doing the intersection of these bodies in order to define the region r1. But, considering that these bodies do not have any space in common r1 is empty

Finally, in the second case:

r1: +b1 | +b2 | … | +b14

Here you are define 14 different zones, using the inside of each bodies, and finally with the operator ‘|’ you do the union of all these zones. Getting finally the desired region

Finally, let’s see why you do not need to do something similar in r2.

r2: +b16 -b1 -b2 - … - b18

Here you are extracting to b16 the bodies b1, b2, and so on. This is well defined and there is nothing to change there.

I let you think why r3 is also well defined :slight_smile:

Does it have sense to you?


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Thank you very much for your answer.
I found my mistake. I confused the concepts of BODY and ZONE. :sweat_smile:

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