The dismantling nuclear power plant is expected to continue to change the radiation working environment compared to the operating nuclear power plant. Contamination monitors and survey meters currently in use have limitations in accurate analysis source term and dose rates for continuous changes in radiation fields at dismantling sites. Due to these limitations, the use of semiconductor detectors such as HPGe and CZT detectors with excellent energy resolution and portability is increasing. The CZT detector performs as well as the HPGe detector, but there is no proven calibration procedure yet. Therefore, in this study, the HPGe calibration method was reviewed to derive implications for the CZT detector calibration method. The operating principle of a semiconductor detector that measures gamma emission energy converts them into electrical signals is the same. Two calibrations of HPGe detectors are performed according to the standard calibration procedure for semiconductor detectors for gamma-ray measurement issued by the Korea Association of Standards & Testing Organizations. The first is an energy calibration that calculates gamma-ray peak position measurements and relational expressions using standard source term that emit gamma-rays. The channel values for energy are measured using certified reference source term to determine radionuclides by identifying channels corresponding to the measured peak energy values. The second is the measurement efficiency of measuring the coefficient calibration device, which measures gamma rays emitted from the standard source term. The detector efficiency by sample or distance is measured in consideration of the shape, size, volume, and density of the calibration device. The HPGe detector performs calibration once every six months through a verified calibration method and is being used as a source term analyzer at the power plant. The CZT detector may also establish a procedure for identifying peak positions through energy calibration and calculating radioactivity through efficiency calibration. This will be a way to expand the usability of semiconductor detectors and further monitor radiation in a more effective way.

In order to start decommissioning domestic nuclear facilities, the Final Decommissioning Plan (FDP) must be prepared and approved by the regulatory agency. The contents of domestic FDP consist of 12 chapters, and there is the decommissioning feasibility design that should be described in Chapter 5 as contents to be considered from the construction stage of nuclear facilities. The design of decommissioning feasibility for nuclear facilities seems to be largely divided into three items. In summary, there ae minimization of contaminations to facilities and the environment, easy of dismantling, and minimization of the radioactive waste generation. In addition, the design characteristics to which the ALARA principle is applied in terms of optimizing the exposure dose of workers and residents may also correspond to the decommissioning feasibility design. The design characteristics for decommissioning feasibility during the period leading up to the design, operation, and decommissioning of nuclear facilities can be listed as the main points as follows. Minimization of facility contamination will include contents related to the leakage of systems and components, minimization of effluents to the environment will involve gaseous and liquid effluents from systems and components to the environment, easy of dismantling will involves history and inspection records during operation, and minimization of radioactive waste generation can be the contents related to the radioactive waste management plans. The design characteristics of facilities and equipment to meet the ALARA principles can be listed as follows. It means taking into account the benefits and costs of the design improvement plan, and the elimination of unnecessary radiation exposure can be maintained at the exposure dose ALARA, which is in line with the decommissioning feasibility design. Among the requirements of licensing documents for decommissioning domestic nuclear facilities is the decommissioning feasibility design. This item relates to the design characteristics for decommissioning considered in the construction stage of the facility and should present the effectiveness of measures for them until operation and decommissioning. In this study, the regulatory requirements presented in the construction and operation stage and the contents presented in the U.S. case were reviewed, and it is hoped that it will be used as reference for the preparation of FDP.

In nuclear decommissioning projects, past and present projects in the world, an important area to be managed is waste management. The management of waste should be done with various aspects of consideration in mind from the moment it occurs from the cutting and dismantling of Systems, Structures, and Components (SSCs). Therefore, this study aims to discuss the disposition considerations for the efficient management of low and very low level waste that is expected to be generated in large quantities and to examine its applicability to domestic nuclear facilities. As for waste management, radioactive wastes begin to be generated when SSCs are dismantled, so waste management should be carried out as a result of dismantling activities. In addition, the waste is stored in the final disposal container and transferred to the storage or disposable facilities. In order to store in the final disposal container or transfer container, it will have to be classified by radioactive level. From the perspective of waste classification, wastes below the low level can be divided into low levels, very low levels, and clearance in Korea. Therefore, as an important point of waste management, when SSCs are dismantled, the work process must be carried out until the final disposal in accordance with the disposition strategy based on the waste classification. As a disposition strategy, the process presented by the IAEA can be referred. The materials to be dismantled for the first time are largely divided into radioactive and suspected radioactive materials. After going through the dismantling process, three criteria are considered to satisfy the disposition option: unconditional release criterion, conditional criterion, and radioactive waste. The types of waste below the final low level are classified into two types as unconditional, two types as conditional, and low and very low levels. In this study, six disposition options are reviewed, including unconditioned reuse and disposal, conditional reuse and disposal, and disposal of VLLW and VLW. Options for radioactive waste may be subject to operational criteria and may need to be supplemented in terms of the acceptance criteria in the repository. In the case of the conditional option, the clearance criterion can be applied, but considering the decommissioning characteristics, it is an option that can be used for nuclear industry, and specific reuse scenarios should be supplemented through discussions with the regulatory agency. In addition, it seems that the unconditional option needs to establish a corresponding criterion.

We studied the basic properties and fabrication of reduced graphene oxide (rGO) prepared using eco-friendly reduction agents in the graphene solution process. Hydrazine is generally used to reduce graphene oxide (GO), which results in polluting emissions as well as fixed nitrogen functional groups on different defects in the graphene sheets. To replace hydrazine, we developed eco-friendly reduction agents with similar or better reducing properties, and selected of them for further analysis. In this study, GO layers were produced from graphite flakes using a modified Hummer’s method, and rGO layers were reduced using hydrazine hydrate, L-ascorbic acid, and gluconic acid. We measured the particle sizes and the dispersion stabilities in the rGO dispersed solvents for the three agents and analyzed the structural, electrical, and optical properties of the rGO films. The results showed that the degree of reduction was in the order L-ascorbic acid ≥ hydrazine > glucose. GO reduced using L-ascorbic acid had a sheet resistance of 121 kΩ/sq, while that reduced using gluconic acid showed worse electrical properties than the other two reduction agents. Therefore, L-ascorbic acid is the most suitable eco-friendly reduction agent that can be substituted for hydrazine.

Clubroot, caused by a soil borne fungus Plasmodiophora brassicae Woronin, is a common disease of cabbages and other plants belonging to the genus Brassica, which is the most extensively cultivated vegetable crops worldwide. This present study was to evaluate the utilization possibility of SNP primers, which we designated as molecular markers linked to disease resistance based on B. rapa genome, it may be possible to apply them to B. oleracea, and to survey SNP marker related to clubroot resistance of cabbages. In total, 425 SNP markers can be applied to B. oleracea were selected from 8,000 SNP markers based on B. rapa genome linked to disease resistance. New 123 SNP markers of them were designed to be analysed to High Resolution Melt (HRM), and tested for clubroot resistance using 6 cabbage varieties, including 3 clubroot resistances (YR Chunrok, YR Dongjanggun, and Grandmart Cabbage) and 3 susceptibilities (Chungam-45, Bogam-1, and Junggam-21). Of them, 118 SNP primers amplified cabbage genomic DNA using HRM analysis, suggesting that it is possible to apply SNP markers based on B. rapa genome to B. oleracea. A total of 4 candidate SNP markers related to clubroot resistance were detected at 80.2℃ of melt temperature in BRS6, 79.2℃ in BRS18, 82.2℃ in BRS79, and at 84.4℃ in BRS114, respectively. These results provide valuable information that can be used for the utilization of the genus Brassica genome study and breeding for clubroot resistance in cabbages.