The rising use of radioactive elements is increasing radioactive pollution and calling for advanced materials to protect individuals. For instance, polymers are promising due to their mechanical, electrical, thermal, and multifunctional properties. Moreover, composites made of polymers and high atomic number fillers should allow to obtain material with low-weight, good flexibility, and good processability. Here we review the synthesis of polymer materials for radiation protection, with focus on the role of the nanofillers. We discuss the effectivness of polymeric materials for the absorption of fast neutrons. We also present the recycling of polymers into composites.

/pdf/polymeric-composite-materials-for-radiation-shielding-a-453m0621xx.pdf

Polymeric composite materials for radiation shielding: a review

J. DAnwl B8NrL.nd, Ph.D., isIlssU14nt professor Andhed, Physic Section, Dep.:ntm ent ofR.4dUaion Oncology, Wa e Forest Unit/miry School of Medicine in Winston-Salem, N.G. He ischairman ofthe AAPM Electronic Media Coordinating Committee, chairman ofthe new AAPM Subcommitteeon MoieCHlaTImaging in Clinical Radiation Oncology, and aformer member ofthe AAPM RildiAtion Therllpy Committee. The AAPM is headqNllTtered in College PIlTk, Md. WHO WE ARE The America n Assoc iation of Physicists in Medicine (AAPM) h J S ap proximately 4.62S mcmbers who practice or arc associn ed with medical physics.

American Association of Physicists in Medicine

The world is naturally radioactive and approximately 82% of human-absorbed radiation doses, which are out of control, arise from natural sources such as cosmic, terrestrial, and exposure from inhalation or intake radiation sources. In recent years, several international studies have been carried out, which have reported different values regarding the effect of background radiation on human health. Gamma radiation emitted from natural sources (background radiation) is largely due to primordial radionuclides, mainly 232Th and 238U series, and their decay products, as well as 40K, which exist at trace levels in the earth's crust. Their concentrations in soil, sands, and rocks depend on the local geology of each region in the world. Naturally occurring radioactive materials generally contain terrestrial-origin radionuclides, left over since the creation of the earth. In addition, the existence of some springs and quarries increases the dose rate of background radiation in some regions that are known as high level background radiation regions. The type of building materials used in houses can also affect the dose rate of background radiations. The present review article was carried out to consider all of the natural radiations, including cosmic, terrestrial, and food radiation.

A review on natural background radiation

Shielding properties of the ordinary concrete loaded with micro- and nano-particles against neutron and gamma radiations.

Photon mass attenuation coefficients of a silicon resin loaded with WO 3 , PbO, and Bi 2 O 3 Micro and Nano-particles for radiation shielding

Background : It has recently been shown that the parcle size of materials used for radiaon shielding can affect the magnitude of radiaon aenuaon. Over the past years, applicaon of nano-structured materials in radiaon shielding has aracted aenon world-wide. The purpose of this study was to invesgate the shielding properes of the lead-free shields containing micro and nano-sized WO3 against low energy x-rays. Materials and Methods : The radiaon shields were constructed using nano and micro WO3 parcles incorporated into an EPVC polymer matrix. The aenu aon coefficients of the designed shields were evaluated for low energy x-rays (diagnosc radiology energy range). Results : The results indicate that nano-structured WO3/PVC shields have higher photon aenuaon properes comp ared to those of the micro-sized samples. Conclusion: Our experiment clearly shows that the smaller size of nano-structured WO3 parcles can guarantee a beer radiaon shielding property. However, it is too early to draw any conclusion on the possible mechanisms of enhanced aenuaon of nano-sized WO3 parcles.

/pdf/radiation-attenuation-properties-of-shields-containing-micro-473h4vng9r.pdf

Radiation attenuation properties of shields containing micro and Nano WO3 in diagnostic X-ray energy range

https://www.researchgate.net/profile/Kamal_Hadad/publication/274252773_INDOOR_RADON_MONITORING_IN_NORTHERN_IRAN_USING_PASSIVE_AND_ACTIVE_MEASUREMENTS/links/5519b1f70cf26cbb81a2b05e.pdf?inViewer=true&disableCoverPage=true&origin=publication_detail

Indoor radon monitoring in Northern Iran using passive and active measurements

This work presents a comprehensive study of natural radioactivity in building materials used in Iran. For this purpose, 177 samples of five types of building material, i.e. cement, gypsum, cement blocks, gravel and brick, were gath- ered from different regions of the country and analyzed by gamma spectroscopy to quantify radioactivity concentrations using a high purity germanium (HPGe) detector and a spectroscopy system. According to the results of this investigation, cement samples had maximum values of the mean Ra-226 and Th-232 concentrations, 39.6 and 28.9 Bq/kg, respectively, while the lowest value for mean concentration of these two radionuclides were found in gypsum samples 8.1 and 2.2 Bq/kg, respectively. The highest (851.4 Bq/kg) and lowest (116.2 Bq/kg) value of K-40 mean concentration were found in brick and gypsum samples, respectively. The absorbed dose rate and the annual effective dose were also calculated from the radioactivity content of the radionuclides. The results show that the maximum values of dose rate and annual effective dose equivalent were 53.72 nGy/h and 0.37 mSv/y in brick samples. The radium equivalent activities Req calculated were below the permissible level of 370 Bq/kg for all building materials. The values of hazard indexes were below the recom- mended levels, therefore, it is concluded that the buildings constructed from such materials are safe for the inhabitants. The results of this study are consistent with the results of other investigations in different parts of the world.

/pdf/natural-radioactivity-in-building-materials-in-iran-1tgebrxtwu.pdf

Natural radioactivity in building materials in Iran

Radiographic imaging has a significant role in the timely diagnosis of the diseases of neonates in intensive care units. The estimation of the dose received by the infants undergoing radiographic examination is of great importance, due to greater more radiosensitivity and longer life expectancy of the neonates and premature babies. In this study, the values of entrance skin dose (ESD), dose area products (DAPs), energy imparted (EI), whole-body dose, effective dose and risk of childhood cancer were estimated using three methods including direct method [using thermoluminescence dosimetry (TLD) chips], indirect method (using tube output) and Monte Carlo (MC) method (using MCNP4C code). In the first step, the ESD of the neonates was directly measured using TLD-100 chips. Fifty neonates, mostly premature, with different weights and gestational ages in five hospitals mostly suffering from respiratory distress syndrome and pneumonia were involved in this study. In the second step, the values of ESD to neonates were indirectly obtained from the tube output in different imaging techniques. The imaging room, incubator, neonates and other components were then simulated in order to obtain the ESD values using the MCNP4C code. Finally, the values of ESD assessed by the three methods were used for calculation of DAP, EI, whole-body dose, effective dose and risk of childhood cancer. The results indicate that the mean ESD per radiograph estimated by the direct, indirect and MC methods are 56.6±4.1, 50.1±3.1 and 54.5±3.3 μGy, respectively. The mean risk of childhood cancer estimated in this study varied between 4.21×10 −7 and 2.72×10 −6 .

Radiation dose to neonates undergoing X-ray imaging in special care baby units in Iran.

In this study, dose rate distribution around a spherical 137Cs pellet source, from a low-dose-rate (LDR) Selectron remote afterloading system used in gynecological brachytherapy, has been determined using experimental and Monte Carlo simulation techniques. Monte Carlo simulations were performed using MCNP4C code, for a single pellet source in water medium and Plexiglas, and measurements were performed in Plexiglas phantom material using LiF TLD chips. Absolute dose rate distribution and the dosimetric parameters, such as dose rate constant, radial dose functions, and anisotropy functions, were obtained for a single pellet source. In order to investigate the effect of the applicator and surrounding pellets on dosimetric parameters of the source, the simulations were repeated for six different arrangements with a single active source and five non-active pellets inside central metallic tubing of a vaginal cylindrical applicator. In commercial treatment planning systems (TPS), the attenuation effects of the applicator and inactive spacers on total dose are neglected. The results indicate that this effect could lead to overestimation of the calculated F(r,θ), by up to 7% along the longitudinal axis of the applicator, especially beyond the applicator tip. According to the results obtained in this study, in a real situation in treatment of patients using cylindrical vaginal applicator and using several active pellets, there will be a large discrepancy between the result of superposition and Monte Carlo simulations.

https://aapm.onlinelibrary.wiley.com/doi/pdf/10.1120/jacmp.v12i3.3480

S. Mehdizadeh

Papers

Radiation attenuation properties of shields containing micro and Nano WO3 in diagnostic X-ray energy range

Indoor radon monitoring in Northern Iran using passive and active measurements

Natural radioactivity in building materials in Iran

Radiation dose to neonates undergoing X-ray imaging in special care baby units in Iran.

Impact of the vaginal applicator and dummy pellets on the dosimetry parameters of Cs-137 brachytherapy source.