Solving the 10 Particle Loss Problem After MCNP5 Run

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SUMMARY

The discussion addresses the issue of particle loss in MCNP5 simulations, specifically when 10 particles are lost during a run. The primary cause is often an improperly defined geometry, where volumes are not correctly assigned to cells. Users are advised to consult the output file for track information and the user manual for guidance on geometry definitions. Key troubleshooting steps include ensuring every volume is part of a defined cell, checking for irregular shapes, and utilizing the vised editor to identify geometry issues.

PREREQUISITES
  • Understanding of MCNP5 simulation software
  • Familiarity with geometry definitions in particle transport simulations
  • Knowledge of cell and volume relationships in MCNP5
  • Experience with the vised editor for geometry visualization
NEXT STEPS
  • Review the MCNP5 user manual for geometry troubleshooting techniques
  • Learn how to interpret output files for particle tracking in MCNP5
  • Explore advanced geometry definitions and common pitfalls in MCNP5
  • Practice using the vised editor to identify and correct geometry errors
USEFUL FOR

Researchers, physicists, and engineers working with MCNP5 simulations, particularly those troubleshooting geometry-related issues in particle transport models.

Rowayda
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After running MCNP5, the output run terminated because 10 particles got lost
how i can fix this problem ?
 
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The most likely thing is you have a problem in your geometry. Someplace you have a volume that is not part of a cell. Read your output file. Also, look in the user manual to see how to get it to output the track information for particles. What you want to find out is where a particle was when it got lost. That should give you a clue as to where there is a problem in your geometry. Every volume must be in a defined cell. You must not have any volume that is undefined. Also, every volume must be in exactly one cell. You can't have any volumes that are in two or more cells.

A frequent place to get into trouble is in arrays. You may not have defined the unit cell the way you thought. So it may not fill the volume you thought.

Another place to get in trouble is when you are doing a cell and the complement. You may have defined the outside of a cell differently from how you thought.

Look for places where you have unusual or irregular shapes, especially where they bound other irregular shapes.

Use the vised editor to help you figure out what cells are not properly defined. One of the tell-tales that vised shows is a dotted line at the boundary of a cell. That usually indicates a problem in the geometry.
 
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