- #1
damyoro
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Greetings to all
I had some problems using MCNP5 for gamma shielding calculation. The original input file is from a document by George E. Chabot, Jr., PhD, CHP Shielding of Gamma Radiation. The description of the problems are following:
1) Three different shielding materials, namely concrete, iron and lead are used to shield plane mono-energetic source particles of energy 0.511 MeV.
2) The said shielding materials are sub-divided into 10 cylindrical cells with equal radius (50 cm) but with different thickness from one material to another: i.e. 5 cm thick (concrete), 2 cm thick (iron) and 1 cm (lead).
3) The doses or kermas are tallied for different thicknesses of a given shielding material and also one tally in the absence of any shielding is used as reference.
4) For each case we wrote 11 input files and tried to run them at least to obtain doses for different geometrical configurations. Had it been successful we could have determined corresponding transmission factors.
5) Unfortunately, despite of several run trials, the input files did not work well as expected.
Comment on results
A: Concrete
• The input file for the concrete shield did not work satisfactorily. The messages generated are kindly reported but not limited to : -
o inp = cc4.txt outp = run runtpe = runtal
o starting mcnp execution
o comment. 22 surfaces were deleted for being the same as others.
o warning. surface 85 is not used for anything.
o imcn is done
o xact is done
The message ‘surface 85 is not used for anything’ is reported. This surface is where the source particles are generated
B: Iron
The input files for iron seemed to work, based on the message generated in the output file
‘run terminated when 10000000 particle histories were done’. Yet, all the 2 tallies are zero. Other messages are issued such as: ‘2 of the tallies did not pass all the statistic checks’, ’the importance may be poor’.
C: Lead
• The typical messages after the run are : -
o inp = pb3.txt outp = pb3o runtpe = run mctal = runtal
o starting mcnp execution
o comment. 22 surfaces were deleted for being the same as others.
o warning. surface 85 is not used for anything.
o imcn is done
o warning. material 1 has been set to a conductor.
o xact is done
o warning. importance function may be poor. see print table 120.
o warning. 2 of 2 tallies did not pass all 10 statistical checks.
o warning. 2 of 2 tallies were all zeros.
o mcrun is done
I attached 2 input and 1 outpout files for reference
Thank in advance for your help
I had some problems using MCNP5 for gamma shielding calculation. The original input file is from a document by George E. Chabot, Jr., PhD, CHP Shielding of Gamma Radiation. The description of the problems are following:
1) Three different shielding materials, namely concrete, iron and lead are used to shield plane mono-energetic source particles of energy 0.511 MeV.
2) The said shielding materials are sub-divided into 10 cylindrical cells with equal radius (50 cm) but with different thickness from one material to another: i.e. 5 cm thick (concrete), 2 cm thick (iron) and 1 cm (lead).
3) The doses or kermas are tallied for different thicknesses of a given shielding material and also one tally in the absence of any shielding is used as reference.
4) For each case we wrote 11 input files and tried to run them at least to obtain doses for different geometrical configurations. Had it been successful we could have determined corresponding transmission factors.
5) Unfortunately, despite of several run trials, the input files did not work well as expected.
Comment on results
A: Concrete
• The input file for the concrete shield did not work satisfactorily. The messages generated are kindly reported but not limited to : -
o inp = cc4.txt outp = run runtpe = runtal
o starting mcnp execution
o comment. 22 surfaces were deleted for being the same as others.
o warning. surface 85 is not used for anything.
o imcn is done
o xact is done
The message ‘surface 85 is not used for anything’ is reported. This surface is where the source particles are generated
B: Iron
The input files for iron seemed to work, based on the message generated in the output file
‘run terminated when 10000000 particle histories were done’. Yet, all the 2 tallies are zero. Other messages are issued such as: ‘2 of the tallies did not pass all the statistic checks’, ’the importance may be poor’.
C: Lead
• The typical messages after the run are : -
o inp = pb3.txt outp = pb3o runtpe = run mctal = runtal
o starting mcnp execution
o comment. 22 surfaces were deleted for being the same as others.
o warning. surface 85 is not used for anything.
o imcn is done
o warning. material 1 has been set to a conductor.
o xact is done
o warning. importance function may be poor. see print table 120.
o warning. 2 of 2 tallies did not pass all 10 statistical checks.
o warning. 2 of 2 tallies were all zeros.
o mcrun is done
I attached 2 input and 1 outpout files for reference
Thank in advance for your help
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