• Applied Chemistry for Engineering
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• v.28 no.2
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• pp.133-140
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• 2017

Increasing concerns on radioactive wastes have drawn much attention on the development of remediation technologies. Massive amounts of radioactive wastes generated from hospital and nuclear power plants were exposed to our environment. Although physicochemical removal methods were developed, an eco-friendly remediation method has not yet been demonstrated. Recently, an extremophilic bacterium has received much attention due to their extraordinary characteristics. Among them, Deinococcus radiodurans (D. radiodurans) strain was regarded as the best host organism for the removal of radioactive heavy metals and radionuclides, because of their superb characteristics like tolerance against the high level of radioactivity. In this article, we briefly introduced the extraordinary nature of D. radiodurans and also discussed the potential use of D. radiodurans strain for the removal of radioactive wastes.

• Nuclear Engineering and Technology
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• v.56 no.1
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• pp.207-215
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• 2024

This study focuses on measuring the levels of naturally occurring radioactivity in the soil of Swabi, Khyber Pakhtunkhwa, Pakistan, as well as the associated health hazard. Thirty (30) soil samples were collected from various locations and analyzed for ²²⁶Ra, ²³²Th, and ⁴⁰K radioactivity levels using a High Purity Germanium detector (HPGe) gamma-ray spectrometer with a photo-peak efficiency of approximately 52.3%. The average values obtained for these radionuclides are 35.6 ± 5.7 Bqkg^-1, 47 ± 12.5 Bqkg^-1, and 877 ± 153 Bqkg^-1, respectively. The level of ²³²Th is slightly higher and ⁴⁰K is 2.2 times higher than the internationally recommended limit of 30 Bqkg^-1 and 400 Bqkg^-1, respectively. Various parameters were calculated based on the results obtained, including Radium Equivalent (Ra_eq), External Hazard (H_ex), Absorbed Dose Rate (D), Annual Gonadal Equivalent Dose (AGDE), Annual Effective Dose Rate, and Excess Lifetime Cancer Risk (ELCR), which are 170.3 ± 24 Bqkg^-1, 0.46 ± 0.06 Bqkg^-1, 81.4 ± 2.04 nGy h^-1, 582 ± 78.08 µSvy^-1, 99.8 ± 13.5 µSv Gy^-1, and 0.349 ± 0.04, respectively. These values are below the limits recommended by the United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR) in 2002. This study highlights the potential radiation threats associated with natural radioactivity levels in the soil of Swabi and provides valuable information for public health and safety.

• Nuclear Engineering and Technology
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• v.56 no.6
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• pp.2174-2181
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• 2024

In this work, Sr_0.5Zr₂(PO₄)₃-SmPO₄ dual-phase ceramics were prepared via in-situ synthesis process, which is a potential novel nuclear waste form for immobilizing the fission product ⁹⁰Sr and the trivalent actinide radionuclides in high-level waste (HLW). And the preparation technology, microstructure and chemical durability of Sr_0.5Zr₂(PO₄)₃-SmPO₄ dual-phase ceramics were systematically investigated. It was confirmed that the optimum microwave-sintering temperature (1050 ℃) and heat preservation time (1.5 h) is estimated by Archimedes method. Besides, the as-prepared samples that were consisted of strontium zirconium phosphate (SrZP) and monazite showed the remarkable densification, in which the two crystalline phases were intermixed well with each other. Meanwhile, the formation and evolution of microstructure was also consistent with the variational rule of Sr_0.5Zr₂(PO₄)₃/SmPO₄, indicating that there was not mutual reaction during the in-situ synthesis process. The PCT and MCC-1 experimental results demonstrated that the elemental normalized leaching rates of tested samples are all at a low level (LR_Sr ~10^-4 g·m^-2·d^-1, LR_Zr ~10^-8-10^-6 g·m^-2·d^-1, LR_Sm ~10^-7-10^-5 g·m^-2·d^-1 and LR_P ~10^-4 g·m^-2·d^-1). It is indicated that Sr_0.5Zr₂(PO₄)₃-SmPO₄ dual-phase ceramics possesses excellent chemical durability for HLW disposal.

• The Korean Journal of Nuclear Medicine
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• v.37 no.6
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• pp.393-401
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• 2003

Objective: Pullulan derivatives (PD) can be used to make self-assembled hydrogel nanoparticles which are responsive to ionic strength. The aim of this study is to evaluate the potential of PD as a retaining carrier of radioisotope inside tumors. Materials and Methods: Four types of PD were evaluated which included pullulan acetate (PA), succinylated PA (SPA), PA-DTPA and SPA-DTPA conjugates. They were radiolabeled with Tc-99m. Labelling efficiencies were determined at 30 min, 1, 2, 4 and 12 hours after radiolabeling. CT-25 colon cancer cells were subcutaneously injected into Balb/c mice. After 2 weeks of subcutaneous injection, Tc-99m-labelled PD (Tc-99m-PD) were injected into the tumors. Whole body images of mice were obtained at 30 min, 1, 2, and 12 hr after intratumoral injection. All twenty mice were grouped into four groups by largest diameter; control A (largest diameter = 5 mm, n = 5), control B (largest diameter = 10 mm, n = 5), pullulan A (largest diameter = 5 mm, n = 5), pllulan B (largest diameter = 10 mm, n = 5). Dynamic images were obtained for 1 hour after intratumoral injection. Static images were obtained at 1 hr, 2 hr, 3 hr and 4 hr after intratumoral injection with Tc-99m pertechnetate and Tc-99m-PA. Target-to-background ratios and retention rates were calculated. Results: Labeling efficiencies of PA, SPA, PA-DTPA and SPA-DTPA were $94.5{\pm}5.9%,\;97.8{\pm}3.5%\;94.2{\pm}3.8%,\;and\;92.5{\pm}6.2%$, respectively (p>0.05). Percent retention rates (%RR) of PA and PA-DTPA were significantly higher than those of control, however, those of SP-DTPA and SPA became similar to control at 4 and 12 hr, respectively. %RR of pullulan A and pullulan B at 1, 4 and 8 hr is significantly higher than that of control (p < 0.05). However, %RR between pullulan A and pullulan B were similar. Conclusion: The lonic strength dependent PD-nanoparticles are retained in the tumor. No difference of %RR according to tumor size was noted. Therapeutic application of PD labelled with beta- or alpha- emitting radionuclides can be expected.