It is possible to extend the shelf life and reduce the waste of agricultural products due to removing bacteria, viruses, insects and pests by means of gamma irradiation with the absorbed dose amount determined by microbiology and food laboratories. For this purpose, the design and construction of a self-shielded gamma irradiation system for irradiation of grains and legumes with radioactive sources of cobalt-60 with activity of 50 kilocuries was performed. In this system, agricultural products are fed in bulk into the input funnel with a conveyor belt. The products move from the inlet funnel to the spiral due to gravitational force and after passing through it, they enter the cask (irradiation chamber) to be irradiated. The absorbed dose amount of agricultural products depends on the time duration that they stay in the irradiation cask, their density, and their type of products, etc. Irradiation time can be adjusted by changing the rotational speed of the screw conveyor considering the last amount of activity remained in the cask at the time of irradiation by means of a software product. The design and construction of type 1 radiation system is based on ANSI/HPSN43.7-2018 standard designed using Solidworks software and basic biological shielding standard ISIRI7751 modeled and calculated by MCNPX software. Other designs and constructions, including industrial and facility drawings, electrical drawings, structural analysis, welding and electrical and control systems were also carried out based on their respective standards. The built mechanical structure can withstand 140kN of loading. The unique design of the entrance chamber in a form of a step instead of a spiral reduces the volume of lead material required for shielding by 2 tons compared to a similar irradiation system made in Hungary. The output mass flow rate of irradiated products in this system is about 1 ton/hour for wheat with dose of 200 grays. The dose uniformity ratio of 2 was obtained, which is acceptable for industrial radiation works.

In this research using the MCNPX code, calculations were done for nuclear designing of portable two-chamber gamma irradiator facility for irradiation of grains and legumes according to international standards. Calculations were made in two parts of dose uniformity ratio and mass flow rate of the irradiated product, as well as gamma-ray shielding using 100 kCi Cobalt-60 line sources, model GIK-A6m of Mayak Co., Russia. The dose uniformity ratios of internal and external irradiation chambers were found to be about 1.77 and 2.18, respectively. Also, the mass flow rate of an irradiated typical grain with a bulk density of 800 kg m-3 was calculated to be about 3.2 ton h-1. A typical grain will receive a dose between 300-656 Gy, which is less than the maximum recommended limit of absorbed dose for grains and legumes (1 kGy) in purpose of shelf-life extension and insect disinfestation by the IAEA. According to ANSI/HPS N43.7, the leakage dose rate at a distance of 5 cm far from the surface of the irradiator in the irradiate mode and for restricted areas, was calculated to be less than 200 µSv/h (maximum permissible radiation level). The results showed that the lead shield of irradiator facility with maximum thickness of 29 cm, easily blocks the emitted gamma rays and working with such a facility would not pose any radiation risk to the employees. Finally, the energy efficiency of the facility was estimated to be about 25% with an increase of about 10.5% due to the addition of external chamber.

Nowadays, the irradiation of blood and blood products, as well as sterilization of pharmaceuticals and biological materials used in the medical industry, are being carried out in developed countries and some developing countries. Usually for this purpose, self-contained dry source storage irradiators containing cesium-137 or cobalt-60 gamma ray sources with activity up to 3 kCi are used as blood irradiator facilities. In this research, an attempt was made to use the MCNPX code to perform the calculations related to the nuclear design of a blood irradiator facility using cobalt-60 line sources in two parts of iso-dose curves and shielding according to internationally accepted standards. The dose uniformity ratio inside the irradiation chamber was about 2 and the external dose rate at a distance of 5 cm from the surface of the gamma cell device was about 36 μ, Sv/h and below the allowable limit. The results showed that the iso-dose curves were completely symmetric and the delivered dose increased near the cobalt-60line sources while decreasing as the distance away from the line sources and closer to the cylindrical axis of the irradiation chamber. In addition, the results showed that the designed lead shield with an average thickness of 30 cm easily blocks the gamma rays and in terms of health physics, working with such a blood irradiator will not pose any risk of radiation to employees.

Study of separation zone is so important in right-angled three-branch or four-branch open channel junctions. Some effective parameters in this case are inlet discharge ratio and flow depth which in this research the effect of inlet discharge ratio and weir height ratios (flow depth) on flow pattern and dimensions of separation zone has been simulated numerically. Investigation of numerical results showed that k-ω model well validated with experimental results and had good agreement, so that simulation error was less than 20%. Dimensions of separation zone in main and side channels were directly proportional with the inlet discharge ratio. Also as increases of height ratio of outlet weirs, flow depth increases and separation zone dimensions decreased. According to the analysis of numerical results, dimensions of separation zone in vertical direction, of the channel bed to water surface increased, so that for discharge ratio 0.6 and height ratio of outlet weirs 0.377, length of separation zone at the channel bed, 0.1 m up the bed and water surface was about 60 cm, 75 cm and 85 cm, respectively. So of the water surface towards the channel bed, length of separation zone decreased about %29.

Introduction: Meat is a rich nutrient matrix that provides a suitable environment for proliferation of meat spoilage microorganisms and common food-borne pathogens. In this study, the effect of irradiation on the meat microbiological quality and half life of minced beef during chilled storage were investigated.Materials and Methods: Samples of minced meat (n=20) were irradiated with doses of 2, 5, 7 and 10 KGy (cobalt-60, gamma cell 220) and evaluated for their microbiological quality up to 10 days.Results: The results showed that gamma irradiation reduced the number of microorganisms in all the irradiated minced meat samples, with 2, 5, 7 and 10 KGy and the half life of samples were increased considerably (p<0.01). In addition, the results indicated that there was a significant difference in the number of coliformes between untreated and irradiated samples (p<0.05). Staphylococcus aureus could not be detected in the irradiated samples with doses of 7 and 10 KGy.Conclusion: These results indicate that irradiation might be employed as an effective mean to inactivate common food-borne pathogens namely S. aureus and increases the half life of meat.

In this study, the neutron and gamma doses in the dry channel and in the internal irradiation site of the Miniature Neutron Source research reactor (MNSR) has been calculated and measured. The MNSR reactor is a light water reactor with a maximum power of 30 kW and equipped with various irradiation facilities, including five irradiated sites, five irradiation sites and a dry channel. The internal irradiation sites have the closest gap to the core of the reactor, with the highest flux and doses available in these locations. Dose calculations have been performed using simulation of the reactor by MCNP computational code and dose measurement using TLD600 and TLD700 thermo-luminescence dosimeters. The experiments have been carried out at both the shutdown and operational status of reactor. In order to validate the computational code, the neutron flux in the internal irradiation site and at the end of the dry channel has been measured by foil activation method and validated by the calculation results. The results of the calculation and measurement of the neutron and gamma doses were in good agreement. The determination of neutron and gamma doses at these sites makes possible such experiments and researches that need to receive a precise amount of neutron and gamma doses.

In this study, cobalt 60 with a mean energy of (1. 25 Mev) was used as a photonic source to investigate the effect of decreasing gamma-ray intensity by materials and polymer composite using MCNPX code. First, we investigated the effect of thickness and density on the reduction of gamma ray intensity, and then the comparison between the lead protector, tungsten and polymer composite in several thicknesses was simulated by MCNPX code and recorded.

Saffron samples collected 16 regions of Khorasan province were investigated For existence of contaminating microbes. Staphylococci, Gram- negative bacilli, fungi and yeast were observed to exist on collected samples .The levels of contamination were counted, over 105, 103, 8x103 for bacteria, fungi and yeasts respectively. To reduce the contamination levels affron samples were irradiated with 2, 4, 6, and 7 KGy the higest decrease in contamination level was obtained with 6KGy, however at 7KGy contamination reached zero. Spectrophotometric analysis showed no change in colour quality of saffron samples. Aroma differentiation by saffron experts indicated no change in treated samples compared with the check.