Can MCNP solve the geometric coincidence issue with a semi-cylinder and cuboid?

In summary, the conversation discusses how to solve a geometric coincidence problem in MCNP, where shapes need to intersect and be defined in a specific way. The conversation also addresses a specific issue with cell definitions and the use of positive and negative surfaces. The issue is eventually resolved by correcting an error in the x-axis, but there is still a problem with cell card 1. There is also mention of a discrepancy between MCNP and VisEd in terms of displaying the model.
  • #1
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How do we solve the geometric coincidence problem? I need a semi-cylinder that fits into the cuboid but if I use the cuboid and the cylinder directly it's geometrically problematic
 
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  • #2
I'm not quite following the question. MCNP does Constructive Solid Geometry. Shapes are supposed to intersect and then you tell it which volumes are what part of the problem.
 
  • #3
I set up four cubes but only two are displayed. In my setting, there should be cuboids in the middle and under the ring. Why?

QQ图片20230426151847.png
 

Attachments

  • A1++.txt
    322 bytes · Views: 86
  • #4
In a cell definition a positive surface typically means above or outside. A negative surface means below or inside. If you take a look at cell 3, you have -3 4, meaning below x=4 and at the same time above x=6. The space between x=4 and 6 is "3 -4". Now have a look at cell 4 and see if you can find something similar.
 
  • #5
Thank you very much Alex A, I got the X-axis wrong. The sign of 1, 2,3, and 4 surfaces in the surface card is wrong
 
  • #6
However, after I corrected the error of x axis, the modeling problem still occurred in cell card 1. Why is cell card 2 and cell card 1 written in the same way? cell1 caused the problem, but cell2 did not
 

Attachments

  • QQ图片20230427163840.png
    QQ图片20230427163840.png
    85.9 KB · Views: 67
  • QQ图片20230427163848.png
    QQ图片20230427163848.png
    135.9 KB · Views: 63
  • A1++.txt
    328 bytes · Views: 75
  • #7
MCNP seems happy. When I try the interactive plotter I see the full D. VisEd does not seem happy from your picture. Maybe VisEd does not like the comment. I do not see an error.
 

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