MCNP output file interpretation

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Discussion Overview

The discussion revolves around the interpretation of output data from MCNP simulations related to a proposed LIFE concept reactor. Participants are exploring how to accurately assess fission energy gain from a fissile blanket that interacts with fusion neutrons generated by a D-T pellet. The focus is on understanding specific parameters in the output file, particularly the 'loss to fission' metric.

Discussion Character

  • Exploratory, Technical explanation, Debate/contested

Main Points Raised

  • One participant questions whether the 'loss to fission' can be used as an accurate indicator of the number of fissions occurring in the system and whether it should be used to calculate total fission energy gain.
  • Another participant suggests consulting the MCNP manual for clarification on the 'loss to fission' parameter and mentions a specific tally for power or power density that may be relevant.
  • A third participant expresses interest in the original poster's findings, indicating a desire for shared knowledge on the topic.
  • A later reply emphasizes the importance of normalization when interpreting the 'loss to fission weight' and advises ensuring the correct average energy per fission is used, noting potential complexities.

Areas of Agreement / Disagreement

Participants do not appear to reach a consensus on the interpretation of the 'loss to fission' parameter, with multiple viewpoints and uncertainties expressed regarding its application and implications for energy calculations.

Contextual Notes

There are limitations noted regarding the normalization of the 'loss to fission' metric and the need for careful selection of average energy values, which may vary based on specific system conditions.

kir
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I am running (a very basic) simulation of the proposed LIFE concept reactor at LLNL as part of my MSc thesis. What I hope to achieve is to calculate the fission energy gain from a fissile blanket surrounding a source of fusion neutrons (ie D-T pellet blasted by lasers)

The problem summary table in the output lists the neutron creation and neutron losses due to various interactions. My question is whether it is correct to take the 'loss to fission' as an indicator of how many fissions occur in the system, and if so would the loss to fission weight per source particle be the correct value to use in calculating the total fission energy gain?
 
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I'm not sure what that loss to fission parameter is. Check your MCNP manual under the section for tallys. I believe there is a specific tally for power or power density (f or fm or something).
 
Dear Kir
If you solved your problem please enlighten me also.
Best wishes
 
"Loss to fission weight" gives the number of fissions, however one should be careful with normalization. Also, be sure that you use the correct value of average energy per fission for your system - it can be tricky in some cases.

kir said:
I am running (a very basic) simulation of the proposed LIFE concept reactor at LLNL as part of my MSc thesis. What I hope to achieve is to calculate the fission energy gain from a fissile blanket surrounding a source of fusion neutrons (ie D-T pellet blasted by lasers)

The problem summary table in the output lists the neutron creation and neutron losses due to various interactions. My question is whether it is correct to take the 'loss to fission' as an indicator of how many fissions occur in the system, and if so would the loss to fission weight per source particle be the correct value to use in calculating the total fission energy gain?
 
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