MCNP Geometry Error

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SUMMARY

The forum discussion centers on resolving a geometry error in MCNP while modeling a 300x300x300 cm room with a doorway. The user faced issues with cell definitions in the Z plane, specifically regarding the intersection and union of blocks. A key solution provided was to adjust the input deck by adding extra brackets to correctly apply intersections to all union blocks. The corrected input line is: 5 0 -1 6 -7 ((2 -10 -5 4) :(10 -3 4 -8) :(10 -3 9 -5)) imp:p 1.

PREREQUISITES
  • Familiarity with MCNP (Monte Carlo N-Particle Transport Code)
  • Understanding of geometric modeling concepts, particularly in 3D space
  • Knowledge of cell definitions and their syntax in MCNP
  • Experience with debugging geometric configurations in simulation software
NEXT STEPS
  • Review MCNP documentation on cell definitions and geometry modeling
  • Practice creating complex geometries in MCNP with varying intersections and unions
  • Explore debugging techniques specific to MCNP geometry errors
  • Learn about best practices for structuring input decks in MCNP
USEFUL FOR

MCNP users, computational physicists, and engineers involved in modeling complex geometries for simulations will benefit from this discussion.

MadGander
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TL;DR
MCNP cell definition help
Hello,

I'm attempting to model a 300x300x300 cm room in MCNP with a doorway and walk-in section, but I'm struggling with some of the cell definitions, particularly in the Z plane. I've attached the input deck below. It is fairly short, so it's probably going to be a relatively quick fix. Any help is appreciated.
 

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Hello again!

More objects but simpler is often easier to debug.

Code:
5 0 -1 6 -7 (2 -10 -5 4) :(10 -3 4 -8) :(10 -3 9 -5) imp:p 1  $ room
I think you were expecting the intersections on the left to apply to all of the union blocks, but this needs extra brackets.
Code:
5 0 -1 6 -7 ((2 -10 -5 4) :(10 -3 4 -8) :(10 -3 9 -5)) imp:p 1  $ room

I think this fixes it.
 

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