No abstract

No abstract

The aim of this work was to develop some X-ray qualities recommended by the International Standardization Organization (ISO) in its standard ISO 4037-1. X-ray qualities corresponding to narrow-spectrum series were established, determined their characteristics and found good agreement with those of reference X-ray beam qualities [difference between first half-value layer (HVL1) < 5% for all qualities]. Acceptable results have also been obtained for second half-value layer (HVL2). The production of X-ray spectra corresponding to developed X-ray qualities with Monte Carlo code PENELOPE (PENetration and Energy Loss Of Positrons and Electrons) was simulated. The characteristics [HVL1, HVL2, homogeneity coefficient (HC) and mean energy (Emean)] of simulated spectra have been calculated and compared to those of measured spectra at Physikalisch-Technische Bundesanstalt taken as reference spectra. The obtained results showed a good agreement between simulated and measured spectra (differences in HVL1, HVL2, HC and Emean were 1.7, 1.44, 0.44 and 1.3%, respectively). The comparison between simulated and measured spectra by calculating the conversion coefficients from air kerma to the personal dose equivalent, hpk(10), and to the ambient dose equivalent, hk*(10), was supplemented. The comparison between the calculated quantities (hpk(10) and hk*(10)) for the two X-ray spectra series showed a good agreement (the maximum difference was <0.4% for hpk(10) and <0.3% for hk*(10)). Furthermore, the percentage depth dose produced in water by simulated and measured spectra was investigated and a good agreement was found between the obtained curves. The established X-ray qualities have been fully characterised (measurement and Monte Carlo simulation). These X-ray beams can be used for calibration of radiation protection instruments and for reference irradiations.

The main goal of the present work is to characterise the neutron field of an OB26 irradiation system acquired by the Nuclear Research Center of Algiers for radiation protection purposes. Extensive Monte-Carlo (MC) calculations and measurements using BF(3)- and (3)He-based neutron area dosemeters were performed to estimate the contribution, on the energy neutron spectrum, of each component present in the bunker facility of the Algerian Secondary Standard Dosimetry Laboratory (SSDL) where the irradiator has been installed. For this purpose, new irradiation configurations based on the (241)Am-Be source placed in the OB 26/2 biological shielding inside its environment have been investigated by MC simulations, and comparison with the ISO spectrum has been performed. During MC simulations, sensitivity analysis has been considered to estimate the effect of several physical parameters on the neutron fluence and dose equivalent rates. In addition, the contribution of the gamma dose equivalent rates to the total neutron dose equivalent rates was estimated for both selected source-detector distances (SDDs) 150 and 200 cm. Finally, a theoretical approach has been adopted, using MCNP5 fluence rates, to estimate the readings of the instruments taking into account their response functions. A low mean difference (12 %) between measured and predicted dose equivalent rates for two selected SDDs has been observed. Overall, the obtained MCNP5 results regarding the actual SSDL irradiation facility are particularly encouraging, but need to be supported by further experimental data.

No abstract