Improving Efficiency in MCNP Neutron Simulations: Tips and Tricks for Beginners

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SUMMARY

The discussion focuses on improving efficiency in MCNPX 2.7 neutron simulations, specifically regarding a semi-open detector setup using 16 He3 tubes. The user reports an efficiency of only 6-7%, which is significantly lower than the 11% efficiency achieved with a different configuration of 12 He3 tubes. Key factors affecting efficiency include the positioning of the detectors and the materials used in the simulation, particularly the matrix composed of Pu240. The conversation highlights the importance of optimizing detector arrangement and material selection to enhance simulation outcomes.

PREREQUISITES
  • Understanding of MCNPX 2.7 simulation software
  • Knowledge of neutron detection principles and efficiency metrics
  • Familiarity with material composition and its impact on neutron interactions
  • Basic skills in manipulating simulation input files and interpreting output data
NEXT STEPS
  • Research optimal configurations for He3 tube arrangements in neutron detectors
  • Learn about the effects of different materials on neutron detection efficiency
  • Explore advanced MCNPX features for improving simulation accuracy
  • Study the MCNP Primer for foundational knowledge and best practices
USEFUL FOR

This discussion is beneficial for nuclear engineering students, researchers in neutron detection, and professionals seeking to optimize MCNPX simulations for enhanced efficiency and accuracy.

Estelassar
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Hi, i am looking for some help on MCNP, more precisely mcnpx 2.7 for neutron simulation.

I created a model of semi opened detector with a various number of 1 inch He3 (here 16)
and i only obtain 6-7% efficiency.
the fact is, I've others technicals notes about same "types" of detector, for example 12 He3 1" disposed in square (wich is not the best positionning) where it's mentionned 11% of efficiency for approximatively the same sort of matrix.

In my case the matrix is composed of Pu240, below you will find my physicals parameters for the simulation.

Do you have some feedback about that ? can someone tell me if i am wrong somewhere to obtain an so low efficiency ?

I am in the blur...
Thx by advance
Qgd3Tsp.png


Code: 
mode n
c
Sdef cel=d1 X=d2 Y=d3 z=d4 erg=d5   
SI1 L 11
SP1 D  1
c
Si2 -14 14
SP2   0  1
c
SI3 -14 14
SP3   0  1
c
SI4   0  34.2
SP4   0   1
c
SP5 -3   0.79493   4.68927       $ 240Pu spectre de watt
c
c ----------------- Materiaux ----------------
c ACIER INOX
C --> Acier inoxydable 18-10 *************************************************
M1      6000.70c -0.001200  24050.70c -0.007513  24052.70c -0.150659
        24053.70c -0.017412  24054.70c -0.004416  26054.70c -0.040580
        26056.70c -0.660588  26057.70c -0.015529  26058.70c -0.002103
        28058.70c -0.067198  28060.70c -0.026776  28061.70c -0.001183
        28062.70c -0.003835  28064.70c -0.001008
c
c AIR ************************************************************************
M3   007014.70c   -0.80
     008016.70c   -0.20
c Helium 3 ****************************************************
M4   002003.70c   -1.0
c
M10   032073.70c -1.
c
c
C ------------------------------- polyethylene  high density (-0.95) -------------------------------
M25       1001.70c -0.143685   1002.70c -0.000033   6000.70c -0.856282
MT25      poly.01t  $ poly.70t
c
c ************************** Cadmium ******************************************
M27   48112.70c  -1.0
c
c --- Matrice source ---
c
c --- Hydrogénée 100% vinyle (densite = 0.4) ---
m50 &
   01001.70c 0.5 & $ H-Hydrogene
    06000.70c 0.33 & $ C-Carbone
    17035.70c 0.17  $ Cl-Chlore
c
c --- Mixte(densite = 0.8) ---
c m50 &
c 1001.70c -0.516    & $ H-Hydrogene
c   8016.70c -0.0645   & $ O-Oxygene
c   17035.70c -0.3655  & $ Cl-Chlore
c   25055.70c -0.00076 & $ Mn-Manganese
c   26056.70c -0.053   & $ Fe-Fer
c   29063.70c -0.0003    $ Cu-Cuivre
c --- Métallique (densite = 0.8 - 7.8) ---
c m50 &
c 06000.70c -0.00170 & $ C-Carbone
c 07014.70c -0.00012 & $ N-Azote
c 15031.70c -0.00035 & $ P-Phosphore
c 16032.70c -0.00035 & $ S-Soufre
c 25055.70c -0.01399 & $ Mn-Manganese
c 26056.70c -0.97801 & $ Fe-Fer
c 29063.70c -0.00548   $ Cu-Cuivre
c
c ******** TALLY neutron  ******
F4:N (340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355)
c
FM4   -1 4 103          $   -1 X 103  /// x= numéro mat hélium
SD4 1                   $ calcul volume tubes
c
ctme 5              $ TALLY Neutron
PRINT
 
Last edited:
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Sorry i can't help you but I am a student in nuclear engineering. I want to use this program. I must learn about C or C++ or Mathlap? Thanks
 
To use this program it's not necessary to know an programing language, it can help for sure (to automatize some tasks or grab data from the result files) but you can easily manipulate input and output files with some Excel.

If you begin, i recommend you this pdf http://www.nucleonica.net/wiki/images/6/6b/MCNPprimer.pdf
Good luck !
 
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