title: Use of the MCNPX to calculate the neutron spectra around the GE-PETtrace 8 cyclotron of the CDTN/CNEN, Brazil.
abstract: The Monte Carlo code MCNPX was used to calculate the neutron spectra in 4 points around the targets of the CDTN/CNEN cyclotron, Belo Horizonte, Brazil, during the production of the (18)FDG. Simulated data were compared with experimental data obtained with a Bonner multisphere spectrometry system (BSS) using TLD-600 and TLD-700 and the unfolding codes BUNKIUT, BUMS and NSDUAZ. In general, simulated spectra disagreed with those obtained by experimental means by a factor as high as 14. Measurements performed with a doserate meter in other 3 more shielded points, showed also an overestimation of the ambient dose equivalent rate by a factor as high as 20 in comparison with simulated results. Results are not conclusive and a more refined study is necessary. However, neutron emission rate of the source-term of radiation must be investigated and an special caution must be taken in the experimental measurements, by discriminating of the target selected for the irradiations and utilizing a matrix response suitable for the passive detectors (e.g. TLD) utilized in the experiments, instead of a matrix response (e.g. UTA4) developed for scintillation detectors.
authors: Postgraduation Course in Science and Technology of Radiations, Minerals and Materials-CDTN/CNEN, Belo Horizonte, MG, Brazil; Development Center of Nuclear Technology-CDTN/CNEN, Belo Horizonte, MG, Brazil. Electronic address: masl@cdtn.br.
authors: M A S
authors: MA
authors: Lacerda
authors: D A M
authors: DA
authors: Campolina
authors: A M
authors: AM
authors: Guimarães
authors: J A
authors: JA
authors: Benavente
authors: T A
authors: TA
authors: da Silva
keywords: Cyclotron; Neutron spectrometry; Thermoluminescent dosimetry