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Neutron shielding materials were fabricated based on natural rubber (NR) and boron carbide (B4C) as their main components. Natural rubber, which is abundant in hydrogen, can lower the energy of a neutron. Boron carbide could be utilized as a neutron shielding material due to its high boron content. The shielding materials were fabricated with boron carbide concentrations of 0, 20, 40, 60 parts per hundred rubber (phr), and 50 wt%. Each sample has been fabricated with thicknesses of 5, 10, 15, 20, and 24 mm. The fabricated materials were examined for mechanical and neutron attenuation tests. The Am/Be at the Radiation Measurement Laboratory at the Nuclear Engineering Department, Faculty of Engineering, Chulalongkorn University, was used as a neutron source. The results show that boron carbide has the effect of reducing the toughness while increasing the hardness of NR composites. The NR sample of 50 wt% in boron carbide allows only 14.1% of neutron transmission according to fast neutron attenuation tests, which is similar to that of a sample of the commercial product obtained from a Japanese company. Our findings will later be compared to those of a Monte Carlo N-Particle (MCNP) transport code.

The borosilicate glass was recycled from high pressure sodium lamp glass (HPSg) and investigated as a starting material for radiation shielding glass. Bi2O3 was expected to improve radiation shielding properties of the glass samples. Mass attenuation coefficients, effective atomic number (Zeff) and effective electron density (Ne) of the glass samples ((80 – x)HPSg – (20)Na2O – (x)Bi2O3 (x = 0, 1, 2, 3, 4 and 5 mol%) were determined at different photon energies. The energy absorption buildup factor (EABF) and fast neutron removal cross sections were also calculated for the given materials. The results clearly revealed that mass attenuation coefficient and other parameters depends on concentration of Bi2O3 and addition of Bi2O3 significantly increased shielding capability of glass samples against gamma rays as well as fast neutrons. The results of Zeff and Ne confirmed the ability of shielding of the glass samples with Bi2O3 as well. Physical properties of glass samples were also investigated in the present work. The obtained ultrasonic velocities and Young's modulus of the glass samples led us to a conclusion that the network structures of the glass are loss of compact structures due to creation of NBOs when adding the Bi2O3. The FTIR measurements confirmed NBOs forming in the network structures of the glass samples with increase of Bi2O3 contents. The reported structural and radiation attenuation properties of recycled glass with Bi2O3 should be important in radiation shielding applications which requires high strength of structures at the same time.

Recycled glass derived from discarded cathode ray tubes (CRT) was used as a component for (70-x)CRT–30K2O–xBaO glass systems (where x = 0–20 mol%). Temperature dependence of ultrasonic wave velocities was carried out at 4 MHz frequency using pressure-controlled ultrasonic technique. It was found that the velocities decreased gradually as BaO content increased. However, sound velocities increased with increasing temperature. Then, both velocities were applied to estimate their elastic properties. Based on the obtained results, the elastic moduli and micro hardness of studied glasses increased with the amount of BaO and temperature, while their Poisson's ratio remained almost constant. Radiation shielding properties were investigated in terms of μm and HVL at photon energies of 74.23, 97.14, 122, 662, 1173, and 1332 keV by using narrow beam x-ray attenuation and transmission methods. Their theoretical values were also calculated by WinXCom program and compared with ferrite concrete. The results showed better radiation shielding properties for recycled CRT glass in comparison to ferrite concrete. Furthermore, the values obtained from the experiment in this study are in good agreement with the theoretical data.

Cesium iodide doped with thallium (CsI:Tl) crystals was grown to develop the gamma-ray detectors by using low-cost raw materials. Effect of impurities on optical properties and radiation detection performance was investigated. By a modified homemade Bridgman–Stockbarger technique, CsI:Tl samples were grown in two levels of CsI and TlI reactant materials, i.e., having as a very high purity of 99.999 % and a high purity of 99.9 %. XRD measurements indicate CsI:Tl crystals having a good quality with a dominant (110) plane. Having a cubic structure, a lattice constant of CsI crystals of 0.4574 nm and a crystallite size of 43.539 nm were obtained. From the lower-purity raw materials, calcite was found in an orange crystal with a lattice constant of 0.4560 nm and a crystallite size of 43.089 nm. By PL measurements, the optical properties of the CsI:Tl crystals were analyzed. ~540-nm-wavelength PL peak was observed from the colorless high-purity crystal, and ~600-nm-wavelength PL peak was observed from the orange crystal. The brighter PL emission was obtained from the orange crystals suggesting impurities. CsI:Tl surface morphology by SEM exhibited a smooth surface with some parallel crystal facets. For electrical properties of high-quality CsI:Tl crystals, the electrical resistances were 230 ± 16 MΩ in cross-sectional direction and 714 ± 136 MΩ in vertical direction with respect to more homogeneous crystal quality in cross-sectional direction than that in vertical direction. TEM measurement was applied to evaluate the microstructure of colorless CsI:Tl crystal with different patterns of a cubic structure. Both CsI:Tl crystals show good efficiencies and good resolutions. Maintaining the same electronic conditions and amplifications, the colorless CsI:Tl scintillators represented a higher detection efficiency at 122 keV of Co-57 of 78.4 % and the energy resolution of 23.3 % compared to the detection efficiency of 75.9 % and the energy resolution of 34.6 % of the orange scintillators. In summary, the unintended impurity as calcite in low-cost CsI:Tl scintillators was found to enhance PL emission but shift the PL wavelength. However, efficiency of radiation detection is slightly lower. By coupling with a suitable PMT, the radiation detection efficiency of low-cost CsI:Tl scintillators can be improved. From these valuable results, growing new ternary materials as CsCaI2 or CsI:Ca or Ca-codoped CsI:Tl scintillators could be one of the promising approaches to achieve highly efficient and low-cost radiation detectors with the optimization of the crystal growth conditions in the future.

The attenuation coefficients of barium–bismuth–borosilicate glasses have been measured for gammaray photon energies of 662, 1173 and 1332 keV using a narrow beam transmission geometry. These coefficients were then used to obtain the values of mass attenuation coefficients, effective atomic number, effective electron density and mean free path. Good agreement has been observed between experimental and theoretical values of these parameters. From the obtained results it is reported here that from the barium–bismuth–borosilicate glasses are better shields to gamma-radiations in comparison to the standard radiation shielding concretes from the shielding point of view. The molar volume, FTIR and acoustic investigations have been used to study the structural properties of the prepared glass system. The obtained results reveal that the formation of non-bridging oxygens occurs at