title: Confirmation of a realistic reactor model for BNCT dosimetry at the TRIGA Mainz.
abstract: OBJECTIVE
  In order to build up a reliable dose monitoring system for boron neutron capture therapy (BNCT) applications at the TRIGA reactor in Mainz, a computer model for the entire reactor was established, simulating the radiation field by means of the Monte Carlo method. The impact of different source definition techniques was compared and the model was validated by experimental fluence and dose determinations.
  
  
  METHODS
  The depletion calculation code origen2 was used to compute the burn-up and relevant material composition of each burned fuel element from the day of first reactor operation to its current core. The material composition of the current core was used in a mcnp5 model of the initial core developed earlier. To perform calculations for the region outside the reactor core, the model was expanded to include the thermal column and compared with the previously established attila model. Subsequently, the computational model is simplified in order to reduce the calculation time. Both simulation models are validated by experiments with different setups using alanine dosimetry and gold activation measurements with two different types of phantoms.
  
  
  RESULTS
  The mcnp5 simulated neutron spectrum and source strength are found to be in good agreement with the previous attila model whereas the photon production is much lower. Both mcnp5 simulation models predict all experimental dose values with an accuracy of about 5%. The simulations reveal that a Teflon environment favorably reduces the gamma dose component as compared to a polymethyl methacrylate phantom.
  
  
  CONCLUSIONS
  A computer model for BNCT dosimetry was established, allowing the prediction of dosimetric quantities without further calibration and within a reasonable computation time for clinical applications. The good agreement between the mcnp5 simulations and experiments demonstrates that the attila model overestimates the gamma dose contribution. The detailed model can be used for the planning of structural modifications in the thermal column irradiation channel or the use of different irradiation sites than the thermal column, e.g., the beam tubes.
authors.affiliation: AIT Austrian Institute of Technology GmbH, Vienna A-1220, Austria and Institute of Atomic and Subatomic Physics, Vienna University of Technology, Vienna A-1020, Austria.
authors.forename: Markus
authors.initials: M
authors.lastname: Ziegner
authors.affiliation: Institut für Kernchemie, Johannes Gutenberg-Universität, Mainz DE-55128, Germany.
authors.forename: Tobias
authors.initials: T
authors.lastname: Schmitz
authors.affiliation: Pakistan Institute of Engineering and Applied Sciences (PIEAS), Islamabad PK-44000, Pakistan.
authors.forename: Rustam
authors.initials: R
authors.lastname: Khan
authors.affiliation: AIT Austrian Institute of Technology GmbH, Vienna A-1220, Austria.
authors.forename: Matthias
authors.initials: M
authors.lastname: Blaickner
authors.affiliation: Acoustics and Ionising Radiation Division, National Physical Laboratory, Teddington TW11 0LW, United Kingdom and Medical Physics Group, EBG MedAustron GmbH, Wiener Neustadt A-2700, Austria.
authors.forename: Hugo
authors.initials: H
authors.lastname: Palmans
authors.affiliation: Acoustics and Ionising Radiation Division, National Physical Laboratory, Teddington TW11 0LW, United Kingdom.
authors.forename: Peter
authors.initials: P
authors.lastname: Sharpe
authors.affiliation: Institut für Kernchemie, Johannes Gutenberg-Universität, Mainz DE-55128, Germany.
authors.forename: Gabriele
authors.initials: G
authors.lastname: Hampel
authors.affiliation: Institute of Atomic and Subatomic Physics, Vienna University of Technology, Vienna A-1020, Austria.
authors.forename: Helmuth
authors.initials: H
authors.lastname: Böck
mesh_terms: D000409:Alanine / Q000737:chemistry; D000465:Algorithms; D016754:Boron Neutron Capture Therapy / Q000295:instrumentation; D003198:Computer Simulation; D005858:Germany; D006801:Humans; D009010:Monte Carlo Method; D009502:Neutrons / Q000627:therapeutic use; D009688:Nuclear Reactors; D019047:Phantoms, Imaging; D017785:Photons; D011874:Radiometry / Q000379:methods*; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods; D015203:Reproducibility of Results
chemical_list: D000409:Alanine