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NEA-1733 MCNP4B-GN.

MCNP4B-GN, Monte Carlo Code System for (gamma,n) production and transport in high-Z materials

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1. NAME OR DESIGNATION OF PROGRAM:  MCNP4B-GN.
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2. COMPUTERS
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Program name Package id Status Status date
MCNP4B-GN NEA-1733/01 Tested 23-NOV-2004

Machines used:

Package ID Orig. computer Test computer
NEA-1733/01 UNIX W.S. UNIX W.S.
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3. DESCRIPTION OF PROGRAM OR FUNCTION

MCNP4B-GN is used to treat (gamma,n) production and transport in medical accelerator heads, to study the undesired neutron dose to patients, employing a single code for both the electromagnetic and the neutron transport.
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4. METHODS

The code simulates the production of giant dipole resonance (GDR) photoneutrons in thick layers of high-Z elements.  Neutrons are generated through evaporation of the compound nucleus or through direct channel; the photoneutron origin coordinates, evaluated as the electromagnetic shower develops are taken into account as well as the energy spectrum of the generated photoneutron.
  
Photoneutron production routines have been inserted into MCNP4B, thus allowing a handling of complicated geometries with a single input definition, a fundamental requirement for this kind of application.
  
The modifications to the standard MCNP4B were made as a "patch" (i.e. a series of instructions on how to modify the basic code) which is distributed together with a preprocessor. The preprocessor reads the patch, reads MCNP4B and writes MCNP4B-GN.  A new subroutine "GAMMN" has been written, analogous to the subroutine "ACEGAM" for (n,gamma). GAMMN is called from subroutine "COLIDP" at a photon collision with one of the 6 elements in question when the energy of the photon is such that there is a non-zero probability of producing a neutron. In analogy with the (n,gamma) capability, the production or not of a neutron is not correlated with the subsequent history of the photon and in particular the choice of the type of photon collision at that spatial point.
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5. RESTRICTIONS ON THE COMPLEXITY OF THE PROBLEM

The upper energy limit, imposed by theoretical considerations, is 30 MeV for photons and 20 MeV for photoneutrons. The physical model breaks down at higher photon energies, whilst the neutron transport performed with MCNP cannot be simulated for neutron energies greater than 20 MeV (the neutron energy regime in MCNP is from 10-11 MeV to 20 MeV. The photoneutron  cross sections for the following elements: Al, Fe, Ta, W, Au and Pb, were inserted into the patch.
Utilization REQUIRES the installation of MCNP Version 4B and the associated cross section libraries.
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6. TYPICAL RUNNING TIME
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7. UNUSUAL FEATURES
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8. RELATED OR AUXILIARY PROGRAMS:  PRPR: This patch should be used with MCNP-4B version.
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9. STATUS
Package ID Status date Status
NEA-1733/01 23-NOV-2004 Screened
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10. REFERENCES

Monte Carlo simulation of the photoneutron field in LINAC radiotherapy treatments with different collimation systems:
- A Zanini, E Durisi, F Fasolo, C Ongaro, L Visca, U Nastasi, K W Burn, G Scielzo, J O Adler, J R M Annand and G Rosner - Physics in Medicine and Biology Vol 49 No 4 (February 21 st, 2004) 571-582.
  
Neutron Spectra in Tissue-Equivalent Phantom during Photon Radiotherapy Treatment by linacs:
- A. Zanini, E. Durisi, F. Fasolo C. Ongaro, U. Nastasi, K.W. Burn and J.R.M. Annand -  Proceeding of the 9th Neutron dosimetry Symposium: Advances in Nuclear Particle Dosimetry for Radiation protection and Medicine, condotto alla Delft University of Technology, Nederland, September 28th- October 3rd, 2003. - Radiation Protection Dosimetry (2004), Vol. 110, Nos 1-4, pp. 157-160.
  
A dosimetric system for the evaluation of undesired neutron dose in radiotherapy treatments with photons: experimental method and MC simulation:
- A. Zanini, F. Fasolo, C. Ongaro, E. Durisi, U. Nastasi, G. Scielzo, M. Fabris, K. W. Burn -  Proceedings of the "workshop on radiation dosimetry: basic technologies, medical applications, environmental application", February 5th - 6th, 2002, Frascati Physics Series Vol XXIX, ISBN 88-86409-36-2, Roma.
  
Photoneutron yields from tungsten in the energy range of the giant dipole resonance:
- I Akkurt, J-O Adler, J R M Annand, F Fasolo, K Hansen, L Isaksson, M Karlsson, P Lilja, M Lundin, B Nilsson, C Ongaro, A Reiter, G Rosner, A Sandell, B Schroeder and A Zanini
2003 Phys. Med. Biol. 48 3345-3352
  
Analysis of photoneutron spectra produced in medical accelerators:
Ongaro C, Zanini A, Nastasi U, Rodenas J, Ottaviano G, Manfredotti C, Burn KW.
Phys Med Biol. 2000 Dec;45(12):L55-61.
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11. HARDWARE REQUIREMENTS:  As MCNP4B, MCNP4B-GN ran on UNIX workstation.
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12. PROGRAMMING LANGUAGE(S) USED
Package ID Computer language
NEA-1733/01 FORTRAN
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13. SOFTWARE REQUIREMENTS
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14. OTHER PROGRAMMING OR OPERATING INFORMATION OR RESTRICTIONS
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15. NAME AND ESTABLISHMENT OF AUTHORS

Kenneth William Burn
FIS-NUC
ENEA
via Martiri di Montesole 4
Bologna, Italy
  
Carla Ongaro
Dipartimento Fisica Sperimentale
Universita di Torino
Via P. Giuria 1
10125 Torino, Italy
  
Alba Zanini
INFN, Sez. Torino
Via P. Giuria 1
10125 Torino, Italy
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16. MATERIAL AVAILABLE
NEA-1733/01
gn1.patch.for.mcnp4b MCNP4 source patch for (gamma,n)
prprkwb.f     Fortran source file
sample.input     Sample input file
sample.output    Sample output file
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17. CATEGORIES
  • C. Static Design Studies
  • J. Gamma Heating and Shield Design

Keywords: LINAC, Monte Carlo method, neutron, neutron dosimetry, photoneutron, photons.