Fixing Error: 10 Particles Got Lost in Fast Reactor Model

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SUMMARY

The forum discussion addresses the error "run terminated because 10 particles got lost" encountered while running a fast reactor model using MCNP. The user is attempting to obtain axial flux and power distributions by dividing the model into zones and employing F7 and F4 tallies. The discussion emphasizes the importance of checking the geometry setup, as lost particles often indicate a geometry error that can be traced through the output file, which details the last known location and transport vector of each lost particle.

PREREQUISITES
  • Understanding of MCNP (Monte Carlo N-Particle Transport Code) version used
  • Familiarity with the sdef card and its parameters
  • Knowledge of F7 and F4 tally methods in reactor modeling
  • Basic principles of particle transport and geometry in nuclear simulations
NEXT STEPS
  • Investigate MCNP output file analysis techniques for lost particles
  • Learn about common geometry errors in MCNP simulations
  • Explore advanced usage of the sdef card in MCNP
  • Study the implementation of F7 and F4 tallies for accurate reactor modeling
USEFUL FOR

Nuclear engineers, reactor physicists, and simulation specialists seeking to troubleshoot particle loss in MCNP fast reactor models.

Juan Ar
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Hi

I am trying to run a fast reactor model but I cannot figure out what is happening because I get the error: run terminated because 10 particles got lost. I am using the sdef card (with and without parameters) and the model is not running. Hope you can help me to fix any mistake I did. The goal in this model is to obtain the axial flux distribution as well as the axial power distribution so I divided the model in different zones to use a F7 and a F4 tally in each one of this zone. I attach the file.

Thanks
 

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Perhaps by describing it in more detail and questioning how you setup your model you will find your missing particles.

Is it possible that this can happen in a normal simulation without it being wrong?

Could the particles have trajectories that just escape out into space that is outside of your simulation just like real particles in a real reactor?
 
This happens usually only if there is a geometry error. Perhaps the region where there is an error is so small, it might not be visible in the plot. If you carefully go through the output file, MCNP prints out details of every single lost particle, it's last known location, cell and transport vector. That should lead you right to the location of the geometry error.
 

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