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Mediterranean fly pest (Ceratitis) is one of the most destructive pests of fruit species in Morocco. The sterile insect technique (SIT) is an environmentally friendly strategy that uses ionizing radiation to sterilize adult insects. Morocco has a panoramic gamma irradiator used to irradiate agri-food products. This irradiator is not dedicated to SIT programs due to its geometry that does not allow to obtain a dose uniformity ratio (DUR) recommended for such applications. This article presents a Monte Carlo study to investigate the feasibility of using the panoramic gamma irradiator at the National Institute for Agronomic Research (NIAR) of Tangier, Morocco, to setting up SIT methods and contributing to Ceratitis control programs. The Monte Carlo method was used to simulate the concrete bunker in which the panoramic gamma irradiator is installed. To obtain a recommended DUR required for SIT programs, two cells similar of the Gammacell-220 irradiator, which is mainly used in the SIT programs around the world, were simulated inside the concrete bunker. The simulation and calculations were performed using the MCNPX-2.7e Monte Carlo simulation code. It is demonstrated that at both investigated positions, the spatial distribution of dose rates in the two modeled irradiation cells, which were similar to a gammacell-220 irradiator cell, are uniform enough that the cells can be used for SIT programs. It is concluded that the panoramic irradiator at NIAR can be used to contribute to the control of Mediterranean fly pest and other insect pests in Morocco. [ABSTRACT FROM AUTHOR]

Irradiated star apples at the minimum absorbed dose of 400 Gy for phytosanitary purpose in Vietnam have been already approved to import to US. In this study, the fresh star apples were treated with electron beams at doses of 0.4, 0.6, 0.8 and 1.0 kGy to evaluate its effect on quality of fruits. The results showed that electron beam radiation doses of 0.4 kGy and 0.6 kGy did not affect to the surface color and percentage of weight loss of fruits. There was significant difference in overall acceptability score with the values of 3.95, 3.92 and 2.45 between irradiated fruits at 0.4, 0.6 kGy and the control (0 kGy) respectively after 6 days in storage at the ambient conditions (temperature of 26±1oC and humidity of 85-90%). Thus, dose range between 0.4 and 0.6 kGy should be used to extend the shelf life of star apple fruits. Because of the low penetration depth of electron beams onto products, dose uniformity ratio (DUR) in the standard carton box for packaging the star apple fruits as well as absorbed doses outside and inside of fruits were calculated.

A treatment of dose nonuniformity inside Lo Ren and purple star apples irradiated by 10 MeV electron beam accelerator has been proposed by using medium density fiberboards (MDF). The dose uniformity ratios (DURs) inside the Lo Ren and purple star apples were estimated as 2.47–2.48 and 2.18–2.22, respectively. To reduce the DURs, the arrangement and the thickness of the MDF boards were determined by Monte Carlo simulations. Measurements of the absorbed doses have been conducted to compare with the simulations. The DURs were reduced to 1.36–1.39 and 1.44–1.46 for the Lo Ren and purple star apples, respectively. [ABSTRACT FROM AUTHOR]

The complexity of the geometrical configuration of a product box and source rack demands an efficient and straightforward methodology for positioning dosimeters in desired planes of the product box to optimise its dose profile. The gamma dose profile generated in the Y-set of commissioning dosimetry depends on the geometry of the selected planes of the product box. The present work attempts to model a product box using a Voronoi diagram-based algorithm for optimising the number of dosimeters in the desired planes of the product box. Discrete dosimeter positions in vertical planes of the product box were used to construct the Voronoi diagram and Delaunay triangulation to model the product box. The Voronoi vertices were computed using a perpendicular bisector algorithm from the discrete coordinates of positions of dosimeters. The Voronoi vertices of the plane of the product box were chosen to optimise the position of dosimeters. The ceric-cerous dosimeters were used to measure the absorbed doses in the product box to validate the algorithm. The overdose ratio calculated was estimated as the average maximum dose and the average minimum dose from the vertices of the Voronoi diagram, and the position of dosimeters put as per conventional strategy in the plane of the product box. The results estimated from the proposed methodology are very close to the conventional dosimetry with a better dose uniformity ratio. The overdose ratio calculated from the Voronoi approach (DUR = 1.06) was found to be improved compared to the estimated overdose ratio (1.07) of the conventional Z-set dosimetry. The present work established the advantages of using the Voronoi Diagram in commissioning dosimetry to ease the dosimetry process. • The present work attempts to model a product box using a Voronoi diagram algorithm. • A Voronoi diagram algorithm has been used for gamma irradiator's dosimetry. • Operating parameters of gamma irradiator better optimised using Voronoi diagram. • Y-set commissioning dosimetry is optimised using Voronoi vertices. • The use of the Voronoi diagram in dosimetry eases the dosimetry process. [ABSTRACT FROM AUTHOR]

It is important to achieve dose uniformity in product box irradiated by gamma irradiators. To minimize lateral non-uniformity of absorbed dose, quantified as Dose Uniformity Ratio in a particular plane (DUR p), activities of source pencils need to be optimized. In present study, Simulated Annealing technique is used for this purpose and the same is described for a Low-Dose 60Co Blood Irradiator. An in-house computer program is developed that calculates DUR p and optimizes the activities of source pencils. The study demonstrates that only the primary component of dose is sufficient to determine DUR p. In the Simulated Annealing technique, several cooling parameters are tested and the most effective cooling schedule is selected to obtain optimized activity distribution. An improvement of 22% in DUR p value is observed after optimization as compared to each source pencil having the same activity. The methodology described in the paper is efficient as optimization of source activities using a trial-and-error approach will be tedious and time consuming. The optimization methodology described in the study is applicable to any irradiator geometry. However, geometry-specific dose calculation approach should be adapted. • Simulated Annealing capable of optimizing source activities to achieve uniform product dose in gamma irradiators. • Primary component of dose sufficient to determine lateral DUR. • Simulated Annealing algorithm more efficient than trial and error approach. [ABSTRACT FROM AUTHOR]

The arrangement pattern of source pencils on the source rack determines the quality of the dose field in a gamma irradiation facility. An optimum source loading plan can achieve a uniform dose distribution and utilize the radiation energy with high efficiency. This study proposed a methodology to optimize source loading plans using genetic algorithms. In a case study of a planar source rack which is typically used in most gamma irradiation facilities, the single objective optimization of source loading plans for minimizing dose uniformity ratio was accomplished with simple genetic algorithm, while the multi-objective one for minimizing dose uniformity ratio and maximizing average dose simultaneously was performed with NSGA-II. The loading plans gained by the genetic algorithms resulted in a 16.0% reduction in dose uniformity ratio and an increase of 5.4% in average absorbed dose compared to the probable random plan. The improvement allows the products to absorb the gamma dose more uniformly and utilizing cobalt-60's energy with higher efficiency. • A method for optimizing the loading plan with genetic algorithm is proposed for the first time. • Accomplish the process of single objective and multi-objective optimization for a planar source rack as a study case. • The results show a 16.0% reduction in dose uniformity ratio and an increase of 5.4% in average dose to the probable random plan. [ABSTRACT FROM AUTHOR]

The four-layer converter consisting of Ta+H 2 O(2 mm)+Fe(2 mm)+Pb is considered. The influence of the Ta and Pb layers thicknesses on the penetration power of bremsstrahlung (BR) produced by 7.5 MeV electrons in the converter has been studied. The average BR energy increases with increase of Ta and Pb layers thickness due to the absorption of low-energy photons in Ta and Pb. Absorbed doses in an object caused by a single element of a small size converter (SEC) are calculated by the Monte Carlo method. The total absorbed doses in the object are determined by summing the doses from the SEC placed along the extended converter. The densities of the electron beam along the converter are determined for two- and four-sided irradiation of objects of given sizes, which provide the minimum Dose Uniformity Ratio (DUR) magnitudes. The polyethylene thickness is shown to be by the factor 1.6 larger in the case of four-sided irradiation by electron beam with optimal density and DUR < 1.5 than in the case of two-sided irradiation. • Pb layer in the Ta converter increases the average energy of the Ta converter. • A modeling BR from extended converter using a small single element proposed. • A single converter element of small size calculated by the Monte Carlo method. • The beam are determined for 2- and 4-sided irradiation for minimum values of DUR. [ABSTRACT FROM AUTHOR]

This study assessed the application of an antibrowning solution using vacuum impregnation (VI) and then electron-beam irradiation as a means to extend the shelf life of sliced white button mushrooms (Agaricus bisporus). A preliminary study helped to determine the best antibrowning solution and VI process parameters. Mushroom slices were impregnated with 2 g/100 g ascorbic acid + 1 g/100 g calcium lactate; 2 g/100 g citric acid + 1 g/100 g calcium lactate; 1 g/100 g chitosan + 1 g/100 g calcium lactate; and 1 g/100 g calcium lactate at different vacuum pressures and times and atmospheric restoration times. Selection of the antibrowning solution and VI parameters was based on texture and color of the mushroom slices. Next, the slices were irradiated at 1 kGy using a 1.35-MeV e-beam accelerator. Physicochemical, sensory, and microbial quality of mushrooms was monitored for 15 d at 4 °C. The best impregnation process in this study was 2 g/100 g ascorbic acid and 1 g/100 g calcium lactate at 50 mm Hg for 5 min and an atmospheric restoration time of 5 min. The control (untreated) samples suffered structural losses throughout storage. Only the vacuum impregnated-irradiated samples had acceptable color by the end of storage. Sensory panelists consistently preferred the samples produced with VI and irradiation because exposure to ionizing radiation inhibited growth of spoilage microorganisms. [ABSTRACT FROM AUTHOR]

Abstract: By using MCNP code and ethanol–chlorobenzene (ECB) dosimeters the simulations and measurements of absorbed dose distribution in a tote-box of the Cobalt-60 irradiator, SVST-Co60/B at VINAGAMMA have been done. Based on the results Dose Uniformity Ratios (DUR), positions and values of minimum and maximum dose extremes in a tote-box, and efficiency of the irradiator for the different dummy densities have been gained. There is a good agreement between simulation and experimental results in comparison and they have valuable meanings for operation of the irradiator. [Copyright &y& Elsevier]

Abstract: This paper discusses the application of the developed analytical method (Reji George, Jain, Pradhan, A.S., 2008. Theoretical evaluation of dose distribution in product in radiation processing plants. Radiat. Phys. Chem. 77, 186–191), for determining the activity loading pattern in a radiation processing plant to get the desired dose uniformity ratio (DUR) for processing mangoes and how the method was used to evaluate the expected source utilization efficiency for the redesigned source–product configuration. [Copyright &y& Elsevier]