Coal-based graphite has become the main material of emerging industries. The microstructure of coal-based graphite plays an important role in its applications in many fields. In this paper, the effect of carbon disulfide/N-methyl-2-pyrrolidone solvent mixture extraction on the microstructure of bituminous coal-based graphite was systematically studied through preliminary extraction coupled with high-temperature graphitization. The graphitization degree g (75.65%) of the coal residue-based graphite was significantly higher than that of the raw coal-based graphite. The crystallite size La of the coal residue-based graphite was reduced by 47.06% compared with the raw coal-based graphite. The ID/ IG value of the coal residue-based graphite is smaller than that of the raw coal-based graphite. The specific surface area (16.72 m2/ g) and total pore volume (0.0567 m3/ g) of the coal residue-based graphite are increased in varying degrees compared with the raw coal-based graphite. This study found a carbon source that can be used to prepare coal-based graphite with high graphitization degree. The results are expected to provide a theoretical basis for further clean and efficient utilization of the coal residue resources.

Considering the characteristics of nuclear power plants in order to decommission nuclear power plants safely and economically, this thesis provides a methodology for optimizing the technology for developing decommissioning characteristic evaluation system using simulation technology for core facilities of the plants based on 3D that reflects various factors. The results of pollution assessment and radiation assessment for the Kori Unit 1 reactor building, auxiliary building, and each major device are displayed in 3D drawings and viewer, and the radiation dose rate and radiation assessment results are displayed separately for each major location. Furthermore, this D/B development method which includes inserting result values of characteristic evaluation and the quantity of waste is one of the main technology to optimize the system which enables users to select decommissioning processes and predict the quantity of waste. (Refer to the presented 3D models of the containment building, D/B, tag search module, the scale calculation result of models after visualizing the result value of 3D based decommissioning characteristic evaluation) The methodology for optimizing decommissioning characteristic evaluation result value DB development system using 3D models of the first major nuclear power plant allows the display of decommissioning characteristic values in virtual reality, the selection of decommissioning process, the establishment of the decommissioning procedure. Hence, this study is expected to provide reliable guidelines for managing a decommission business efficiently in the near future and can be used in the related field if needed.

Decontamination of spent nuclear fuel from decommissioned nuclear reactors is crucial to reduce the volume of intermediate-level waste. Fuel cladding hulls are one of the important parts due to high radioactivity. Their decontamination could possibly enable reclassification as low-level waste. Fuel cladding hulls used in research reactors and being developed for conventional light water reactors are Al-Mg and Fe-Cr-Al alloys, respectively. Therefore, the recovery of these component metals after decontamination is necessary to reduce the volume of highly radioactive waste. Electrochemical approach is often chosen due to its simplicity and effectiveness. Non-aqueous solvents, such as molten salts (MSs) and ionic liquids (ILs), are preferred to aqueous solvents due to the absence of hydrogen evolution. However, MSs and ILs are limited by high temperature and high synthesis cost, along with toxicity issues. Deep eutectic solvents (DESs) are synthesized from a hydrogen bond acceptor (HBA) and donor (HBD) and exhibit outstanding metal salt solubility, wide electrochemical window, good biocompatibility, and economic production process. These characteristics make DES an attractive candidate solvent for economic, green, and efficient electrodeposition compared with aqueous solvents such acids or nonaqueous solvents such as MSs or ILs. In this research, the feasibility of electrodeposition of Al-Mg and Fe-Cr-Al alloys in ChCl:EG, the most common DES synthesized from choline chloride (ChCl) and ethylene glycol (EG), will be tested. A standard three-electrode electrochemical cell with an Au plated working electrode and Al wires for counter and reference electrodes is utilized. Two electrolyte solutions (Al-Mg and Fe-Cr-Al) are prepared by dissolving 100 mM of each anhydrous metal chloride salts (AlCl3, MgCl2, CrCl3, and FeCl2) in ChCl:EG. Cyclic voltammogram (CV) is measured at 5, 10, 15, and 20 mV·s−1 to observe the redox reactions occurring in the solutions. Electrodeposition of each alloy is performed via chronoamperometry at observed reduction potentials from CV measurements. The deposited surfaces and cross-sections are examined by scanning electron microscopy and energy dispersive spectroscopy (SEM-EDS) to analyze the surface morphology, cross-section composition, and thickness. Authors anticipate that the presence of different metals will greatly affect the possibility of electrodeposition. It is expected that although all metals are distributed throughout the surface, the morphology, in terms of particle size and shape, would differ depending on metals. Different metals will be deposited by layers of an approximate thickness of a few μm each. This research will illustrate a potential for recovery and electrodeposition of other precious radioactive metals from DES.

As the number of aging nuclear power plants increases, the market for dismantling nuclear power plants is growing rapidly. About 40% of the cost of dismantling nuclear power plants is the waste treatment cost incurred during the dismantling process, of which concrete waste accounts for a significant portion of the total waste. Securing technology for reducing and recycling concrete waste is very important not only in terms of economy but also in terms of environment. The objective is to synthesize geopolymer using inorganic materials from cement fine powder in concrete waste. Cement fine powder in concrete waste has a large amount of inorganic elements necessary for filing materials for radioactive waste treatment such as CaO and SiO2. In particular, Ca(OH)2 is synthesized by extracting Ca2+ from concrete waste. It can be used as an alkali activator to synthesize geopolymer. The mortar from crushed concrete was used as a source of calcium. The first step is to react with concrete waste and hydrochloric acid to extract ions. The second step is to react with NaOH and synthesize Ca(OH)2. The product was divided into two stages according to the reaction method and order. The first and second products were washed and dried, and then XRD and XRF were performed. The second product was matched only Ca(OH)2 and CaCO3 at the XRD peak. In the case of XRF, it was analyzed to have a purity of 67.80–78.73%. Synthesis of geopolymer by recycling materials extracted from concrete waste can reduce disposal costs and improve the utilization rate of disposal sites.

Immobilization of radioactive borate waste containing a high boron concentration using cement waste form has been challenged because the soluble borate phase such as boric acid reacts with calcium compounds, hindering the hydration reaction in cement waste form. Metakaolin-based geopolymer waste form which has a pure aluminosilicate system without calcium can be a promising alternative for the cement; however, secondary B-O-Si networks are formed by a reaction between borate and silicate, resulting in poor mechanical characteristics such as low compressive strength and final setting retardation. Thus, it is important to optimize the Si/Al molar ratio and curing temperature which are critical parameters of geopolymer waste form to increase borate waste loading and enhance the durability of geopolymer. Here, metakaolin-based geopolymer waste form to immobilize simulant radioactive borate waste was fabricated by varying the Si/Al molar ratio and curing temperature. The 7 days-compressive strength results reveals that the Si/Al molar ratio of 1.4 and curing at 60°C is advantageous to achieving high waste loading (30wt%). In addition, geopolymer waste forms with the highest borate waste loading exceeded the 3.445 MPa after the waste form acceptance criteria such as thermal cycling, gamma irradiation, and water immersion tests. The leachability index of boron was 7.56 and the controlling leaching mechanism was diffusion. The thermal cycling and gamma irradiation did not significantly change the geopolymer structure. The physically incorporated borate waste was leached out from geopolymer waste form during leaching and water immersion tests. Considering these results, metakaolin-based geopolymer waste form with a low Si/Al ratio is a promising candidate for borate waste immobilization, which has been difficult using cement.

Nuclear security event involving nuclear and other radioactive materials outside of regulatory control (MORC) has the potential to cause severe consequences for public health, the environment, the economy and society. Each state has a responsibility to develop national nuclear security measures including nuclear forensics to respond to such events. In Japan, national nuclear forensics capability building efforts mainly based on research and development (R&D) have been conducted since 2010, in accordance with national statement of Japan at the Nuclear Security Summit in Washington DC. Most of that work is undertaken at the Integrated Support Center for Nuclear Non-proliferation and Nuclear Security (ISCN) of the Japan Atmic Energy Agency (JAEA) in close cooperation with other competent authorities. The ISCN has made increased contributions to the enhancement of international nuclear security by establishing technical capabilities in nuclear forensics and sharing the achievements with the international community. The ISCN has mainly engaged in R&Ds for establishing and enhancing nuclear forensics technical capability. As for the laboratory capability, several new pieces of analytical equipment have been introduced for nuclear forensics R&D purposes. High-precise measurement techniques validated in the past nuclear forensics incidents have been established, and novel techniques that can contribute to the more timely and confident nuclear forensics signature analysis have been developed. The ISCN has been also developed a proto-type nuclear forensics library based on the data of nuclear materials possessed for past nuclear fuel cycle research in JAEA. These technical capability developments have been conducted based on the cooperation with international partners such as the U.S. Department of Energy and EC Joint Research Center, as well as participation in exercises organized by Nuclear Forensics International Technical Working Group (NF-ITWG). Recent R&D works have been mainly based on the needs of domestic competent authorities, such as first responders and investigators, and aim to develop technologies covering the entire spectrum of nuclear forensics processes from crime scene investigation to laboratory analysis and interpretation. One important key issue is the enhancement of technical capability for post-dispersion nuclear forensics. For instance, the ISCN has carried out the development of radiation measurement equipment coupled with the low-cost and mobile radiation detectors that uses machine-learning algorithms for quick and autonomous radioisotope identification to support first responders during crime scene investigations. Laboratory measurement techniques for samples collected at a post-dispersion crime scene are also among the important technical issues studied at the ISCN. The application of emerging technologies to nuclear forensics has also been studied. This includes the application of deep leaning models to nuclear forensics signature interpretation that could provide more confident results, as well as the development of contamination imaging technology that could contribute to the analytical planning on the samples in collaboration with conventional forensics. Many analytical techniques have been developed and the capability to analyze nuclear and other radioactive materials for nuclear forensics purposes has been considerably matured over the past decade. The challenges of post-dispersion samples, collaboration with conventional forensics and the development of novel signatures will be more important in the near future. Therefore, the ISCN will promote the R&Ds to further enhance the technical capabilities solving these issues. In addition, the ISCN is also promoting to expand the nuclear forensics research into universities and other research institutes in Japan. This is expected to contribute to the establishment of a domestic nuclear forensics network that enables to respond timely and flexibly to the MORC incidents, and to the maturation of nuclear forensics as a new academic field.

The bacterial soft-rot disease is one of the most critical diseases in vegetables such as Chinese cabbage. The researchers isolated two bacteria (Pseudomonas kribbensis and Pantoea vagans) from diseased tissue samples of Chinese cabbages and confirmed them as being the strains that cause soft-rot disease. Lactic-acid bacteria (LAB), were screened and used to control soft-rot disease bacteria. The researchers tested the treatments with hypochlorous acid water (HAW) and LAB supernatant to control soft-rot disease bacteria. The tests confirmed that treatments with the HAW (over 120 ppm) or LAB (Lactobacillus plantarum PL203) culture supernatants (0.5 mL) completely controlled both P. kribbensis and P. vagans.