Radioactive mixed waste (RMW) is containing radioactive materials and hazardous materials. Radioactive wastes containing asbestos are include in RMW. These wastes thus must be treated considering both radioactive and hazardous aspects. In this study, a high temperature melt oxidation system consisting of an electric arc furnace and a molten salt oxidation furnace has been developed for the treatment of of radioactive waste containing asbestos. A surrogate waste of the radioactive waste containing asbestos (content of asbestos: 13wt%) was treated in this system. It was melted and fabricated into a glass waste form in the system. Asbestos was not detected in this glass waste form. This means that the asbestos was converted to a glass component in the glass waste form. The waste form was homogeneous glass, and it had a high value of compressive strength (475.13 MPa). It was also confirmed through a leaching test (ANS 16.1) that the waste form had a high chemical durability (Leaching Index > 6). Based on these results, it is considered that the high temperature melt oxidation system will be utilized for the treatment of a significant amount of radioactive waste containing asbestos generated from decommissioning a nuclear power plant.

In the pilot scale test, the two scale-up factors (Electric energy per order EEO, Electric energy per mass EEM) were conducted to design the Chemical Waste Decomposition & Treatment System (CWDS). The CWDS consist of two kind UV lamp reactors to improve the decomposition rate of oxalic acid, which are low pressure amalgam UV lamp and medium pressure UV lamp. The two reactors were connected in series, and the hydrogen peroxide is mixed through a line mixer at the front of the reactor and injected into the reactors. The CWDS was connected with the full system decontamination equipment to purify the residual oxalic acid after chemical decontamination process. The full system decontamination equipment were included Oxidizing Agent Manufacturing System (OAMS), Chemical Injection System (CIS), RadWaste Treatment System (RWTS) to operate the Oxidation/Reduction decontamination process and purify the process water. After decontamination process, the waste water will be cooled down into the 40°C and passed through the UV reactor at 110 gpm with hydrogen peroxide injection. The concentration of waste water is expected oxalic acid 1,700 ~ 2,000 ppm, Iron 5 ~ 20 ppm. As a result of the CBD test in the laboratory with simulated waste liquid, the amount of Low pressure amalgam lamp UV dose required to decompose 95% of oxalic acid in 2 m2 waste water was up to 1,800 mJ/cm2. The amount of medium pressure lamp UV dose was up to 450 mJ/cm2 at the same condition. We conducted demonstration test using 2 m2 waste water after the oxidation/reduction decontamination process, the decomposition rate 95% was obtained by low pressure amalgam UV lamp and medium pressure UV lamp reactor each.

Boric acid-containing B-10 is used in a nuclear reactor as a coolant and absorbs thermal neutrons generated during nuclear fission in the primary circuit. Boron-containing coolant water waste is generated from maintenance, floor drain, decontamination, and reactor letdown flows. There are two options for aqueous solution waste of boric acid. One is recycling and discharge through filtration, ion exchange, and reverse osmosis. The other is immobilization after evaporation and crystallization processes. The dry powder of boric acid waste liquid can be immobilized by cement, polymer, etc. Before the mid-1990s, concentrated boric acid waste was solidified with a cement matrix. To overcome the disadvantage of low waste loading of cement waste form, a method of solidifying with paraffin was adopted. However, paraffin solids were insufficient to be disposed of as final waste. Paraffin is a kind of soft solidified material and has low compressive strength and poor leaching resistance. As a result, it was decided as an unsuitable form for disposal. In KOREA, paraffin waste form was adopted for boric acid waste treatment in the 1990s. A large amount of paraffin waste forms about 20,000 drums (200 l drum) were generated to treat boric acid waste and were stored in nuclear power sites without disposal. In this study, we want to obtain high-purity boric acid waste by oxidizing and decomposing solid paraffin waste form through a boric acid catalytic reaction. In this reaction, paraffin is separated in the form of various by-products, which can then be treated through a liquid waste treatment device or an exhaust gas treatment device. The proper temperature for sample decomposition during the catalytic reaction was set through TGA analysis. Compositions of by-products and residues generated at each stage of the reaction could be analyzed to determine the state during the reaction. Finally, the boric acid waste powder was perfectly separated from paraffin waste form with disposable products through this pyrolysis process.

The facile production of high-purity mesophase pitch has been a long-standing desire in various carbon industries. Recently, polymer additives for mesophase production have attracted much attention because of their convenience and efficiency. We propose polyvinylidene fluoride (PVDF) as a strong candidate as an effective additive for mesophase production. The mesophase content and structural, chemical, and thermal properties of pitches obtained with different amounts of added PVDF are discussed. The influence of PVDF decomposition on mesophase formation is also discussed. We believe that this work provides an effective option for mesophase pitch production.

Domain decomposition method (DDM) has been widely employed for the numerical analysis of large-scale problems due to its applicability to parallel computing. DDM divides the modeling domain into a set of subdomains and obtains the entire solution iteratively until the values of each subdomain which are shared with other subdomains, such as boundary values, are converged. Therefore, in general, DDM is a memory-efficient iterative algorithm with inherent parallelism on the geometric level. APro, the process-based total system performance assessment model, aims for simulating the radionuclide transport considering coupled multi-physics phenomena occurring in large-scale geological disposal system, which are inevitably accompanied by huge memory burden. Therefore, DDM is applicable for the large-scale problem of APro and its performance in parallel computing needs to be examined. The DDM solvers provided by COMSOL which constitute APro can be classified into two methods. One is the overlapping Schwarz method that each subdomain overlaps its neighboring domains and the other is the Schur complement method that subdomains are non-overlapping and separated by boundary domains. For the Schwarz method, the additive, hybrid, multiplicative and symmetric methods can be selected according to the solution update scheme. And for the Schur method, the additive and multiplicative ordering options can be chosen for solving Schur complement system. In this study, the calculation efficiency of the DDM solvers in COMSOL and the applicability to the cluster environment were examined. In aspect of efficiency, the memory requirements with different number of subdomains and calculation schemes were compared in a single node. Then, the memory requirements with increasing number of disposal tunnels and deposition holes were investigated in multiple nodes. As a result, on the cluster environment, with the help of distributed memory architecture which enables efficient memory usage, the applicability of DDM solvers to the large-scale problem of APro was confirmed.

공주지역에 조림된 리기다소나무 군락에서 국내 대표 수종인 소나무와 방풍림으로 주로 조림되는 곰솔 낙엽의 분해율 및 분해과정에 따른 영양염류의 함량 변화를 파악하였다. 분해 60개월 경과 후 소나무 낙엽과 곰솔 낙엽의 잔존율은 각각 42.12±5.30과 24.79±1.98%로 소나무와 곰솔의 낙엽 분해율은 곰솔 낙엽의 분해가 소나무 낙엽의 분해에 비해 빠르게 일어났다. 60개월 경과 후 소나무 낙엽과 곰솔 낙엽의 분해상수 (k)는 각각 3.02과 3.59로 곰솔 낙엽의 분해상수가 다소 높게 나타났다. 소나무 낙엽의 분해과정에 따른 C/N, C/P 비율은 초기에 각각 14.4, 144.1 이었으나 60개월 경과 후에는 각각 2.26와 40.1로 점차 감소하였으며, 곰솔 낙엽의 경우 초기 C/N, C/P 비율은 각각 14.4와 111.3로 나타났고, 60개월 경과 후에는 각각 3.06와 45.8로 나타났다. 낙엽의 초기 N, P, K, Ca, Mg 함량은 소나무 낙엽에서 각각 3.07, 0.31, 1.51, 16.56, 2.03 mg g-1, 곰솔 낙엽에서 각각 3.02, 0.39, 0.99, 19.55, 1.48 mg g-1로 소나무 낙엽과 곰솔 낙엽의 질소와 인의 함량은 유사하였다. 60 개월 경과 후 N, P, K, Ca, Mg의 잔존율은 소나무 낙엽에서 각각 231.08, 130.13, 35.68, 48.58, 36.03%이었고, 곰솔 낙엽에서 각각 143.91, 74.02, 28.59, 45.08, 44.99%로 나타났다.

The estimation of the postmortem interval (PMI, the time that has elapsed since the death) is a critical issue for the biosecurity enforcement officers who implement to the timely establishment of biosecurity zone for preventing susceptible animals from disease transmission given the rapid occurrence of an infectious disease. Increasing attention has been paid to PMI of wild boar (Sus scrofa) carcasses associated with African swine fever epidemics in Korea since October 2019 to explain the geographical transmission of the disease, as well as to provide potential target animals for prevention measures in terms of farm biosecurity. This study is, to the best of our knowledge, the first to describe the decomposition process of wild boars in different microhabitats in the country. In the present comparative study, we obtained field data from the decomposition process of the wild boar and domestic pig carcasses continuously exposed aboveground in natural environment settings allowing animal scavenging. This study compared the pattern of decomposition in 16 wild boar carrion and 10 domestic pig carcasses placed between August and November 2019. Quite differences in decomposition rate measured by total body score and tissue's gross morphology over time were observed between wild boars and domestic pigs. Overall, the wild boar decomposed much more slowly than the domestic pig throughout the end of the experimental period. In addition, color changes to the skin were easily seen in domestic pigs, whereas there is much variation in the wild boar, especially carcasses placed in late autumn. Moreover, some wild boar carcasses did not show any sign of bloating. These results indicate that decomposition rates derived from forensic taphonomic studies on domestic pigs may be not directly applicable to the wild boar, hence there is a need to develop regional decomposition models to be employed in different geographical situations to increase the accuracy of PMI of wild boar carcasses.

The sunspot area is a critical physical quantity for assessing the solar activity level; forecasts of the sunspot area are of great importance for studies of the solar activity and space weather. We developed an innovative hybrid model prediction method by integrating the complementary ensemble empirical mode decomposition (CEEMD) and extreme learning machine (ELM). The time series is first decomposed into intrinsic mode functions (IMFs) with different frequencies by CEEMD; these IMFs can be divided into three groups, a high-frequency group, a low-frequency group, and a trend group. The ELM forecasting models are established to forecast the three groups separately. The final forecast results are obtained by summing up the forecast values of each group. The proposed hybrid model is applied to the smoothed monthly mean sunspot area archived at NASA's Marshall Space Flight Center (MSFC). We find a mean absolute percentage error (MAPE) and a root mean square error (RMSE) of 1.80% and 9.75, respectively, which indicates that: (1) for the CEEMD-ELM model, the predicted sunspot area is in good agreement with the observed one; (2) the proposed model outperforms previous approaches in terms of prediction accuracy and operational efficiency.

초해상도 기법은 영상 획득장치의 물리적인 한계를 극복하기 위해 저해상도 영상으로부터 고해상도 영상을 생성하는 기술이다. 초해상도 기법들 중 TV 기반 초해상도 기법은 에지보존과 artifact가 없다는 점에서 성공적인 방법으로 평가되어 왔다. 본 논문에서는 저해상도 번호판 영상의 해상도 개선을 위해 새로운 TV 분해 기반 초해상도 기법을 제안하였다. 제안된 방법에서 번호판 영상은 TV 분해에 의해 영상의 주된 객체들에 해당하는 구조적 성분과 텍스쳐 성분으로 분해된다. 여기서, 영상의 주된 객체들과 같은 기하학적인 정보를 포함하는 구조적 성분은 번호판 영상의 번호판 글자와 유사하다. 따라서, 번호판 글자와 같은 구조적 성분의 해상도를 개선하기 위해 NNE 기반 SVR 방법을 제안하였다. 또한, 후처리 과정으로서 윤곽선을 효과적으로 보존하고, 잡음을 제거하기 위해 TV 디노이징 필터를 이용하였다. 실험을 통하여 본 논문에서 제안된 방법이 기존의 바이큐빅 보간법, ScSR, NNE 및 SRCNN 기법들에 비해 양호한 영상 및 PSNR, SSIM 척도 관점에서 향상된 좋은 결과들을 보였다.

For solving phase separation of nanoparticles and graphene oxide (GO) in the application process, MgWO4– GO nanocomposites were successfully synthesized using three different dispersants via a facile solvothermal-assisted in situ synthesis method. The structure and morphology of the prepared samples were characterized by X-ray diffraction, Scanning electron microscopy, Transmission electron microscopy, Fourier transform infrared and Raman techniques. The experimental results show that MgWO4 nanoparticles are tightly anchored on the surfaces of GO sheets and the agglomeration of MgWO4 nanoparticles is significantly weakened. Additionally, MgWO4– GO nanocomposites are more stable than self-assembly MgWO4/ GO, which there is no separation of MgWO4 nanoparticles and GO sheets by ultrasound after 10 min. The catalytic results show that, compared with bare MgWO4, MgWO4– GO nanocomposites present better catalytic activities on the thermal decomposition of cyclotetramethylenete tranitramine (HMX), cyclotrimethylene trinitramine (RDX) and ammonium perchlorate (AP). The enhanced catalytic activity is mainly attributed to the synergistic effect of MgWO4 nanoparticles and GO. MgWO4– GO prepared using urea as the dispersant has the smallest diameter and possesses the best catalytic action among the three MgWO4– GO nanocomposites, which make the decomposition temperature of HMX, RDX and AP reduce by 10.71, 11.09 and 66.6 °C, respectively, and the apparent activation energy of RDX decrease by 68.6 kJ mol−1.