MCNP Input of Voxel Arrays and Their Universes

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Discussion Overview

The discussion revolves around issues encountered while inputting voxel arrays and their universes in MCNP (Monte Carlo N-Particle Transport Code). Participants share specific error messages and seek assistance with geometry errors, cell definitions, and surface types.

Discussion Character

  • Technical explanation
  • Debate/contested
  • Homework-related

Main Points Raised

  • One participant reports an error related to an unrecognized surface type when defining a voxel universe, suggesting a potential formatting issue.
  • Another participant indicates that a "zero lattice element hit" error typically signifies geometry errors, overlapping cells, or mis-defined surfaces.
  • A participant expresses a similar issue with a "bad trouble in subroutine newcel" error, suspecting it relates to repeated surface definitions in the geometry chain.
  • One user encounters a "cell 2 have no fill" error while attempting to run their code, indicating a possible issue with cell definitions or fills.

Areas of Agreement / Disagreement

Participants express various problems and potential solutions, but no consensus is reached on the specific causes or resolutions for the errors discussed. Multiple competing views on the nature of the errors and their solutions remain present.

Contextual Notes

Participants reference external resources, such as a primer on common MCNP problems, but some links provided are reported as non-functional. The discussion includes unresolved technical details and assumptions about the geometry definitions.

Who May Find This Useful

This discussion may be useful for users of MCNP who are facing similar issues with voxel arrays, geometry definitions, or error troubleshooting in their simulations.

njm
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Hi
I have problems in mcnp input of voxels. I define a voxel arrays and their universes,for example universe1 is defined as:
2001 43 -1.030 -70 u=1 vol=6.795352
but in runing I have below error:
fatal error.the surface type is not recognized: -1.03
While 1.03 is the density of material43!

Can anyone help me?
 
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njm said:
Hi
I have problems in mcnp input of voxels. I define a voxel arrays and their universes,for example universe1 is defined as:
2001 43 -1.030 -70 u=1 vol=6.795352
but in runing I have below error:
fatal error.the surface type is not recognized: -1.03
While 1.03 is the density of material43!

Can anyone help me?

It sounds like you are trying to define a cell card in the surfaces section. Do you have an extra line break somewhere?
 
oh yes!
thank you very much
 
Now I have this error:
zero lattice element hit.
what is it?!
How can I solved it?!
 
Last edited:
Thanks you so much for your help.
 
Yrrepy said:
if you have a zero lattice element hit: it usually means you have a geometry error, overlapping cells, mis-defined cell surfaces etc

check out this primer

at the end is an excellent summary of common problems and their solutions

http://www.google.com/url?sa=t&rct=...W1oaVs&usg=AFQjCNHBUq22eV7EEAikLl32QV2VWK3LnQ

I am having the similar problems while running my script. I get this error

bad trouble in subroutine newcel of mcrun
source particle no. 2804404
starting random number = 132729341823053
zero lattice element hit.
run terminated because of bad trouble.

I suspect it has to do with something the code says before it starts that surface 42 appears more than once in a chain.
Does anyone have an idea of what it could be? And also the link to that primer doesn't work does anyone have a new link to it?
 
Hi,
I am trying to do similar , but first I must learn basic stuff...
When I try to run code (down below) i get fatal error cell 2 have no fill?

1 1 -1 -1 fill=1 imp:n=1
2 1 -1 -2 lat=1 u=1 imp:n=1
3 0 1 imp:n=0

1 box -5 -5 -10 10 0 0 0 10 0 0 0 20
c 1 REC 0 0 0 0 0 70 20 0 0 0 10 0
2 box -5 -5 -10 1 0 0 0 1 0 0 0 1
c box -1 -1 -1 1 0 0 0 1 0 0 0 1

m1 94239.66c 1.0
c tally
f4:n 1 (2<2[0:9 0:9 0:19])
sdef pos .1 .1 .1
print

Any tips?

Cheers..
 

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