نشریه سنجش و ایمنی پرتو
سال سیزدهم شماره 1 (پیاپی 49، بهار 1403)

The necessity for fabrication detectors with large dimensions, optimal efficiency, high resolution and low price has led to extensive research in the manufacturing of plastic scintillators in the last two decades. The optimization of this type of scintillator is one of the current research topics in the world. In this study, styrene monomer, diphenyloxazole (PPO) as the primary fluorophore and phenyl oxazole benzene (POPOP) as the secondary fluorophore and naphthalene were used to fabricate the plastic scintillators. The samples were fabricated through thermal polymerization without an initiator. The results of gamma spectroscopy using 137Cs and 60Co sources have been shown the increase of the light yield by 5.7% and 2.7% respectively by adding naphthalene in construction of the plastic scintillator. The neutron-gamma discrimination was determined with an analogous discrimination circuit based on the zero-crossing method with a 252Cf source. The results showed that for the sample containing 15 wt% PPO without naphthalene, the FOM and peak-to-valley ratio at a bias of 1000 keVee were 0.91 and 4.18, respectively, while for the sample with 15 wt% PPO and 4 wt% naphthalene, 1.05 and 8.71 were obtained, respectively.

Calculation of the dose spatial distribution during radiation therapy can help doctors to better treat the cancerous organ and reduce the dose of sensitive organs around it. Tissue equivalent polymer gel dosimeters consist of radiation-sensitive chemicals that are polymerized under irradiation as a function of absorbed dose, and the spatial information of dose distribution can be extracted by imaging the irradiated gel. In this study, using MCNPX Monte Carlo code and ORNL phantom, the received dose of lungs, liver, breast, stomach, spleen, and kidneys were simulated during targeted radionuclide therapy of lung cancer tissue with iodine-131. Then MAGICA and PAGATA gel dosimeters were placed in the target tissues and their received dose were checked again. The results of these simulations show that the received tissue dose of lungs, liver, breast, stomach, spleen, and kidneys are comparable with the results of MAGICA and PAGATA gel dosimeters; therefore, these gel dosimeters can be used in dosimetry studies of treatment with iodine-131 in physical phantoms.

The aim of this paper is to determine the fast neutrons flux incident upon the HPGe detector during the BN thick target gamma-ray yield measurements. These measurements were conducted using the deuteron beam of 0.6, 0.8, 1 and 1.2 MeV. In this work, we measured the fast neutrons flux using the 596 keV gamma peak originating from the 74Ge(n,nγ)74Ge and 73Ge(n,γ)74Ge reactions. The contributions of the capture and inelastic scattering reaction over the 596 keV gamma peak yield were measured. The advantage of the method is that no additional equipment is required and the flux of fast neutrons is measured online using the collected gamma spectrum.

The thermal quenching can be identified from diminishing of maximum temperature and peak intensity of thermoluminescence glow peaks by increase in heating rate. CaF2:Mn(TLD-400) is amongst the thermoluminescence phosphors that is affected by thermal quenching. thermoluminescence glow curve of this phosphor is contained 5 component glow peaks which obey first order kinetics. Using the given thermal quenching parameters of this phosphor, the kinetic parameters of all component glow peaks were evaluated with and without considering thermal quenching effect based on first order kinetics. This was carried out by fitting the experimental glow curve with theoretical models for different heating rates. Considering that the function describing the thermoluminescence intensity in presence of thermal quenching differs from that in absence of thermal quenching, fitting procedure results different kinetic parameters for two above cases.

Fast estimation of dose distribution in victims of industrial radiography accidents is important. Thus having a data library from effective dose and absorbed dose data for use in crucial situations can be effective. In this study, the whole body effective dose for two commonly used industrial radiography sources, 192Ir and 60Co, was evaluated using the MCNPX2.6 Monte Carlo code and the adult male voxel phantom ICRP. Simulations were performed in 4 radiation geometries (AP, PA, RLAT, LLAT) and 5 different source heights including ground, middle thigh, lower torso, middle torso, and upper torso. The results of this study show that the effective dose at all heights at distance greater than 100 cm, except for ground level, is independent of source height and relatively consistent. The highest and lowest values of effective dose are associated with the AP and RLAT radiation geometries, respectively. The effective dose at the middle torso in the AP geometry and at a distance of 0.5 cm is 5 and 200 times higher compared to the middle thigh and ground heights, respectively, for both 192Ir and 60Co sources. Using the data obtained in this study, the effective dose for a victim of a 1996 accident in Gilan was estimated to be 200 mSv. The results of this study were compared with the data reported in ICRP145, and the reasons for the differences were investigated.

In this research, Squid bone wastes were collected from the coast of the Persian Gulf. After washing and purification, pure calcium carbonate nanoparticles and calcium oxide nanoparticles were synthesized by mechanical grinding and calcination. The structure, shape, and size of the nanoparticles have been investigated by X-ray diffraction pattern and scanning electron microscope, and using the Williamson-Hall method, an approximate size of 68 nm has been obtained for them, which is consistent with the scanning electron microscope images. Gamma rays irradiated to nanoparticles from a 60Co source and their thermoluminescence properties were investigated. The obtained results illustrate that nanoparticles show sensitivity to gamma rays in high doses and have a linear behavior in a range of 1 kg Gy to 5 kg Gy. The fading curve of the samples showed a 12% decrease in 30 days.