The nuclear power plant decommissioning project inevitably considers time, cost, safety, document, etc. as major management areas according to the PMBOK technique. Among them, document management, like all projects, will be an area that must be systematically managed for the purpose of information delivery and record maintenance. In Korea, where there is no experience in the decommissioning project yet, data management is systematically managed and maintained during construction and operation. However, if the decommissioning project is to be launched soon, it is necessary to prepare in consideration of the system in operation, what difference will occur from it in terms of data management, and how it should be managed. As a document that can occur in the decommissioning project, this study was considered from the perspective of the licensee. Therefore, the types of documents that can be considered at Level 1 can be divided into (1) corresponding documents, (2) project documents, (3) internal documents, and (4) reference materials. Four document types are recommended based on Level 1 for the classification of documents to be managed in the decommissioning of nuclear facilities. In this study, documents to be managed in the decommissioning project of nuclear facilities were reviewed and the type was to be derived. Although it was preliminary, it was largely classified into major categories 1, middle categories 2, and 3 levels, and documents that could occur in each field were proposed. As a result, it could be largely classified into corresponding documents, project documents, internal documents, and reference materials, and subsequent classifications could be derived. Documents that may occur in the decommissioning project must be managed by distinguishing between types to reduce the time for duplication or search, and the capacity of the storage can be efficiently managed. Therefore, it is hoped that the document types considered in this study will be used as reference materials for the decommissioning project and develop into a more systematic structure.

In the case of decommissioning nuclear facilities in Korea, the dismantling activities will be initiated after obtaining approval from the regulatory agency for the Final Decommissioning Plan (FDP). The contents to be described in the FDP are presented in the notice of the Nuclear Safety and Security Commission, and among them, it is suggested to estimate and provide the basis for the decommissioning cost. The Work Breakdown Structure (WBS) is used for schedule management for the project, and the performance activities can be used as a cost management structure as well as schedule management. In order to easily manage the process and cost, the WBS structure can be normally used, and at this time, there might be a connection with ISDC if necessary. Therefore, this study aims to examine the link between activities from the WBS structure to ISDC in the decommissioning project. In general, the activities assumed as a WBS structure in this study in carrying out the decommissioning project were derived at the Level 1 and Level 2. Activities at Level 1 can be classified into project management costs, controlled area dismantling, conventional area dismantling, site remediation, waste treatment facility, construction/service, R&D, waste treatment and disposal, and characterization. For Level 2 activities, a cost activities embodied in Level 1 was derived. ISDC was developed by the OECD Nuclear Energy Agency (NEA) decommissioning cost estimation group, which improves ambiguous cost systems and presents common cost items for direct comparison between international decommissioning projects. The ISDC consists of Level 1, Level 2, and Level 3, where Level 1 represents the principal activity, Level 2 represents the activity group, and Level 3 represents the typical activity. The cost categories for typical activity at Level 3 consist of labour, investment, expenses, and contingency. In this study, the connection between WBS and ISDC was shown, and a comparison was made at Level 2. Directly, one-on-one matches have difficulties, and as much as possible, they were organized into similar items. We arranged the Level 2 linked to ISDC based on WBS. If there is a difficulty in one-on-one matches, it seems that the accurate cost calculation of ISDC items should consider the impact of additional cost distribution. Therefore, in order to calculate ISDC costs, it seems necessary to organize cost items of WBS in consideration of the ISDC.

The domestic Nuclear Power Plant (NPP) decommissioning project is expected to be carried out sequentially, starting with Kori Unit 1. As a license holder, in order to smoothly operate a new decommissioning project, a process in terms of project management must be well established. Therefore, this study will discuss what factors should be considered in establishing the process of decommissioning NPPs. Various standards have been proposed as project management tools on how to express the business process in writing and in what aspects to describe it. Representatively, PMBOK, ISO 21500, and PRICE 2 may be considered. It will be necessary to consider IAEA safety standards in the nuclear decommissioning project. GSR part 6 and part 2 can be considered as two major requirements. GSR part 6 presents a total of 15 requirements, including decommissioning plans, general safety requirements until execution and termination. GSR part 2 presents basic principles for securing the safety of nuclear facilities, and there are a total of 14 requirements. Domestic regulatory guidelines should be considered, and there will be largely laws and regulations related to the decommissioning of nuclear facilities, guidelines for regulatory agencies, and guidelines and regulations related to HSE. The Nuclear Safety Act, Enforcement Decree, Enforcement Rules, and NSSC should be considered in the applicable law for nuclear facilities. Since the construction and operation process has been established for domestic decommissioning project, there will be parts where existing procedures must be applied in terms of life cycle management of facilities and the same performance entity. As a management areas classification in the construction and operation stage, it seems that a classification similar to Level 1 and Level 2 should be applied to the decommissioning project. This study analyzed the factors to be considered in the management system in preparing for the first decommissioning project in Korea. Since it is project management, it is necessary to establish a system by referring to international standards, and it is suggested that domestic regulatory reflection, existing business procedures, and domestic business conditions should be considered.

The decommissioning of Korea’s nuclear power facilities is expected to take place starting with the Kori Unit 1 followed by the Wolsong Unit 1. In Korea, since there is no experience of decommissioning, considerations of site selection for the waste treatment facilities and reasonable selection methods will be needed. Only when factors to be considered for construction are properly selected and their effects are properly analyzed, it will be possible to operate a treatment facility suitable for future decommissioning projects. Therefore, this study aims to derive factors to be considered for the site selection of treatment facilities and present a reasonable selection methodology through evaluation of these factors. In order to select a site for waste treatment facilities, three virtual locations were applied in this study: warehouse 1 to warehouse 3. Such a virtual warehouse could be regarded as a site for construction warehouses, material warehouses, annexed building sites, and parking lots in nuclear facilities. If the selection of preliminary sites was made in the draft, then it is necessary to select the influencing factors for these sites. The site of the treatment facility shall be suitable for the transfer of the waste from the place where the dismantling waste is generated to the treatment facility. In addition, in order for construction to take place, interference with existing facilities and safety should not be affected, and it should not be complicated or narrow during construction. Considering the foundation and accessibility, the construction of the facility should be economical, and the final dismantling of the facility should also be easy. In order to determine one final preferred plan with three hypothetical locations and five influencing factors, there will be complex aspects and it will be difficult to maintain consistency as the evaluation between each factor progresses. Therefore, we introduce the Analytic Hierarchical Process (AHP) methodology to perform pairwise comparison between factors to derive an optimal plan. One optimal plan was selected by evaluating the three virtual places and five factors of consideration presented in this study. Given the complexity and consistency of multiple influencing factors present and prioritizing them, AHP tools help users make decisions easier by providing simple and useful features. Above all, it will be most important to secure sufficient grounds for pairwise comparison between influencing factors and conduct an evaluation based on this.

Among the twenty six nuclear power plants in Korea, twenty four plants are currently in operation excluding the two permanently shut-down Kori #1 and Wolsung #1 plants. The decommissioning process includes many tasks such as cutting, decontamination, disposal and treatment. Among the tasks, because cutting is one of the tasks performed close to the target structure, there is a possibility for the workers to be exposed excessively to the radiation. There are representative large structures such as steam generators, nuclear reactors, reactor coolant pump, and pressurizer, made of metals, and radioactive concrete, made of concrete. Especially, compared to the trend of research to manage the radiation exposure of steam generators that are directly connected to pressurizers, the trend of research to manage the radiation exposure of pressurizers to workers is not satisfactory. Moreover, although there have been many studies on radioactive concrete, the studies to manage the radiation exposure to workers with a systematic cutting scenario are insufficient. In this study, radioactive concrete, a representative large structure made of concrete, was selected as the target for evaluation. The conditions for evaluation were cutting speed (1~10 m2/hr) and the time for cutting (permanent shutdown~30 years after the shutdown). A cutting scenario was developed by applying the situation for abrasive decontamination beforehand and Hot-to-Cold and Cold-to-Hot, and effort was made to derive a reasonable plan. The evaluation result derived were hourly radiation dose distribution of 1.19~0.103 mSv/hour and 1.29~0.0113 mSv/hour for a scenario without abrasive decontamination (in the order of Hot to Cold, Cold to Hot), and hourly radiation dose distribution of 0.547~0.0479 mSv/hour and 0.608~0.0522 mSv/hour for a scenario with abrasive decontamination. The maximum value of collective dose derived was 1.54E+04 mSv at the cutting time of permanent shutdown with cutting speed of 1 m2/hour in the Cold to Hot scenario before abrasive decontamination, and the minimum value derived was 5.15E+01 mSv at the cutting time of 30-year after the permanent shutdown with cutting speed of 10 m2/hour in the Hot to Cold scenario after abrasive decontamination.

On March 11 2011, Fukushima Daiichi nuclear power plant site was attacked by a huge tsunami caused by Tohoku Pacific Ocean earthquake. Nuclear fuels of unit 1, 2, and 3 of Fukushima Daiichi nuclear power plant was melted down by the disaster. After the accident, Japan’s government has announced “Mid-and-Long-Term Roadmap towards the decommissioning of TEPCO’s Fukushima Daiichi Nuclear Power Station Units 1-4”. The topics of roadmap is made of measures to deal with contaminated water, removal of fuel rod assemblies from spent fuel pools, retrieval of fuel debris, measures to deal with waste materials, and other operations. To support the activity of the roadmap, various facilities about decommissioning have been established and operated on inside or outside of Fukushima Daiichi nuclear power plant site. Representatively, Collaborative Laboratories for Advanced Decommissioning Science which conducts R&D decommissioning, Naraha Remote Technology Development Center which develops remotes robots and VR (Virtual reality), Okuma Analysis and Research Center which performs radiochemical analyses for radioactive waste, and Fukushima Environmental Safety Center which conducts environmental dynamics and radiation monitoring.

Metal waste generated during the dismantling of a nuclear power plant can be contaminated with radionuclides. In general, the internal structure is very complex. Thus, metal waste requires various cutting processes. When metal waste is cut, aerosols are generated. Aerosols are generally various particles of very small size suspended in the working area and remain for a considerable period. This may cause internal exposure of workers due to inhalation of radioactive aerosols generated when cutting radioactive metal waste. This study investigated various cutting processes and the size distribution of aerosols generated during the cutting process. The cutting process is normally classified into thermal cutting, mechanical cutting, and laser cutting. Thermal cutting includes plasma, flame, and oxygen cutting. Mechanical cutting includes mechanical saws, cutters, nibblers, and abrasive water jets. Stainless steel, carbon steel, aluminum, and copper are commonly used as cutting materials in nuclear power plants. The size of the aerosol generated from cutting showed a very diverse distribution depending on the cutting methods and cutting materials. In general, aerosol size is distributed within 0.1-1 μm. This size distribution is different from the 5 μm aerosol size suggested by the ICRP Publication 66 Lung model. These results show that it is necessary to conduct further studies on the size of aerosols generated when decommissioning nuclear power plants.

Wolsong Unit 1 is about 679 MW Pressurized Heavy Water Reactor (PHWR). Canada AECL was responsible for Nuclear Steam Supply System (NSSS) design and supply. Wolsong Unit 1 was operated from 1983 to 2019. Currently, Wolsong Unit 1 is under safety management after permanent shutdown. Wolsong unit 1, a heavy water reactor, has the following characteristics. • Unlike Light Water Reactor, vertical reactors, Heavy Water Reactor is installed horizontally. • The internal structure of the reactor is more complex than that of a light water reactor (380 pressure tubes in reactor as called Calandria) • The Calandria Vault, a large concrete structure filled with light water, is located outside of Calandria In the case of the decommissioning plan of PHWR in Canada, they have adopted a deferred decommissioning strategy that decommissioning begins after permanent shutdown and long-term safety management (30 to 40 years). So, Decommissioning of PHWR in Canada is expected to start in the 2050s. Nuclear Safety Act stipulates that if a commercial nuclear power plant is permanently suspended, the utility must submit a Final Decommissioning Plan (FDP) within 5 years. So, KHNP, the utility, is developing the FDP for Wolsong Unit 1 and have a plan to submit it to the government by the end of 2024. And then licensing review is expected to take at least two years. The key milestone for decommissioning project has a plan to start decommissioning in 2027 and complete it by 2034, but this is flexible depending of the government’s approval for decommissioning and the completion of prerequisites such as spent fuel transfer, etc. KHNP has prepared a strategy and system consisting of three areas such as R&D, Engineering and licensing document development to prepare the final decommissioning plan for Wolsong Unit 1. The promotion system for the preparation of the FDP for Wolsong Unit 1 is consisted of Engineering (HAS Characterization, Process/Work Package/Cost Estimation, Dismantling Safety Evaluation, Radiological Environmental Report, Radioactive Waste Treatment and Facility Construction), R&D (COG cooperation, KHNP R&D Results), Kori unit 1 lessons learned, etc. KHNP have the plan that the FDP Draft development by the end of 2023, reflecting engineering services results, R&D results, COG technical cooperation results and lessoned learned on Kori Unit 1. After collecting opinions from residents through a public hearing, the FDP will be submitted to the government by the end of 2024. It is expected that there will be many difficulties in the development process as it is the world’s first FDP development for the commercial Pressurized Heavy Water Reactors.

Kori Unit 1 is about 600MW Pressurized Light Water Reactor as WH type. KHNP got an approval for construction and operation of Kori unit 1 on May 31, 1972 and started commercial operation from Apr. 29, 1987. And then, it was decided to permanently suspend it on Jun. 18, 2017 after 40 years of commercial operation. The Nuclear Safety Act stipulates that if a commercial nuclear power plant is permanently suspended, the utility must submit a Final Decommissioning Plan (FDP) within 5 years. So, KHNP, the utility, developed a FDP for Kori Unit 1 and submitted it to the government in May 2021. In South Korea, the FDP is to be prepared in accordance with the relevant notices and consists of 11 major chapters such as (1) Decommissioning Plan Overview, (2) Project management, (3) Status of Site and Environmental, (4) Decommissioning Strategies and Method, (5) Ease of Decom. Design characteristic, (6) Safety Analysis, (7) Radiation Protection, (8) Decontamination and Dismantling, (9) Radioactive Waste Management, (10) Environmental Impact Analysis, (11) Fire Protection and (12, 13) Etc., References and Glossary. KHNP has prepared a strategy and system consisting of three areas such as R&D, Engineering and licensing document development to prepare the final decommissioning plan for Kori Unit 1. The promotion system for the preparation of the FDP for Kori Unit 1 is composed of Engineering (HAS Characterization, Dismantling Safety Evaluation, Radiological Environmental Report, Radioactive Waste Treatment and Facility Construction), R&D(KHNP R&D Results such as Process/Work Package /Cost Estimation, Safety Analysis, Contamination and Exposure, Guide for Detailed Characteristic, Site Safety Analysis, RV & RVI Dismantling Process, etc.), Overseas case lessons learned(Taiwan unit 1 NPP FDP and Spain Zorita NPP FDP analysis) and Development of Licensing Document. KHNP completed the initial completion of the Final Decommissioning Plan for Kori Unit 1 in March 2020 and carried out collecting residents’ opinions through public hearings. And then, KHNP supplemented the results of the residents’ opinions and applied for license to the Nuclear Safety and Security Commission in May, 2021. Now, KHNP are responding to the FDP licensing review.

The type of radioactive waste that may occur in the process of nuclear power plant dismantling can be classified into solid, liquid, gas, and mixed waste. In addition, according to the level of radioactivity, it can be divided into high level, intermediate level, low level, and clearance level waste. In the case of solid radioactive waste, it is necessary to secure disposal suitability in order to deliver it to a disposal facility, so safe and efficient treatment of a large amount of radioactive waste generated during decommissioning is one of the most important issues. For the treatment of radioactive waste generated during decommissioning, technologies in various fields such as cutting, decontamination, melting, measurement, and packaging are required. Therefore, this study intends to present and application plan for decommissioning domestic nuclear power plants through overseas case studies for the treatment of radioactive waste expected to occur during nuclear power plant decommissioning.

The concept of clearance is to manage radioactive waste by incineration, reclamation, or recycling as non-radioactive waste, excluding those found to have a concentration of less than the allowable concentration of clearance. Among the types of waste subject to clearance, concrete is managed by recycling and landfill, metal by recycling and reuse, combustible materials by incineration, and soil by landfill. In Korea, clearance has been implemented in earnest since 2000, and the types and quantity of waste subject to clearance are increasing. For clearance, the nuclear-related operator submits its clearance plan to the regulatory body, and the regulatory body reviews the clearance plan and notifies the operator of its suitability. Since a significant amount of radioactive waste generated when decommissioning nuclear power plants is expected to be classified as clearance waste, this study will present clearance waste disposal measures for nuclear power plant through a review of overseas cases related to clearance.

Working during decommissioning of nuclear facilities can subject workers to a number of industrial health and safety risks. Such facilities can contain hazardous processes and materials such as hot steam, harsh chemicals, electricity, pressurized fluids and mechanical hazards. Workers can be exposed to these and other hazards during normal duties (including slips, trips and falls, driving accidents and drowning). Industrial safety accidents, along with their direct impacts on the individuals involved, can negatively affect the image of nuclear facilities and their general acceptance by the public. Industrial safety is the condition of being protected from physical danger as a result of workplace conditions. Industrial safety program in a nuclear context are the policies and protections put in place to ensure nuclear facility workers are protected from hazards that could cause injury or illness. Preventive actions are those that detect, preclude or mitigate the degradation of a situation. They can be conducted regularly or periodically, one time in a planned manner, or in a predictive manner based on an observed condition. Corrective actions are those that restore a failed or degraded condition to its desired state based on observation of the failure or degradation. In industrial safety, the situations or conditions of interest are those observed via the performance monitoring, investigations, audits and management reviews. Preventive and corrective actions are those designed to place or return the system to its desired state. Preventive actions where possible are preferred as they eliminate the adverse condition prior to it occurring. When an accident or incident occurs, the primary focus is on obtaining appropriate treatment for injured people and securing the scene to prevent additional hazards or injuries. Once the injured personnel have been cared for and the scene has been secured, it is necessary to initiate a formal investigation to determine the extent of the damage, causal factors and corrective actions to be implemented. Certain tools may be needed to investigate such incidents and accidents. Initial identification of evidence immediately following the incident includes a list of people, equipment and materials involved and a recording of environmental factors such as weather, illumination, temperature, noise, ventilation and physical factors such as fatigue and age of the workers. The five Ws (what, who, when, where and why) are useful to remember in investigation of incidents and accidents.

The operation and decommissioning of nuclear power plants (NPPs) creates waste in the process of handling radioactively contaminated material, which must be disposed of in a repository or can be recovered of in the same way as conventional waste in the course of handling radioactively contaminated materials. For buildings or sites of NPPs it also has to be decided under what conditions they can continue to be used for other, conventional purposes or demolished. This decision is referred to as “release from supervision under nuclear and radiation protection law” or “clearance” in short. The clearance levels applicable in Germany according to the Radiation Protection Ordinance have been defined such that a radiation dose (hereinafter referred to as “dose”) of 10 μSv per year is not exceeded. The vast majority of the materials resulting from the dismantling of a nuclear power plant (e.g. most of the massive concrete structures) are neither contaminated nor activated. Thus, there is no need to treat these materials as radioactive waste. Emplacement of uncontaminated masses which in Germany is essentially several million tonnes of building rubble in a repository would require additional construction of such facilities, which, in view of the negligible hazard potential, from the point of view of the Nuclear Waste Management Commission (ESK) is clearly to be rejected both economically and, in particular, ecologically. Alternative ways are increasingly discussed in public, such as the abandonment of buildings after gutting, i.e. refraining from demolition of the controlled area buildings of NPPs. Also, another proposal discussed in public, the landfilling or the long-term storage of cleared material at the site, does not offer any safety-related advantages either in the view of the ESK. If, after completion of all dismantling work, the building has been decontaminated such that the clearance levels for buildings are complied with further use of the building rubble resulting from demolition is harmless from a radiological point of view. For these reasons, Germany has deliberately decided to use clearance as an essential measure in the dismantling of NPPs. If it is intended to conventionally reuse or depose of virtually contaminant-free material from controlled areas, it must first undergo a clearance procedure. The prerequisites that must be fulfilled for clearance are regulated in the Radiation Protection Ordinance, which includes two basic clearance pathways: unrestricted and specific clearance. In the following, the basic process of clearance is briefly presented and illustrated for a better understanding. It comprises five steps. Step 1-Radiological characterization by sampling, Step 2-Dismantling of plant components in the controlled area, Step 3- Decontamination, Step 4-Decission measurements, Step 5-Clearacnce and further management. The entire clearance process is governed by a clearance notice and is carried out under the supervision of the competent authority under nuclear and radiation protection law or the independent authorized expert commissioned by it. The clearance pathways contained in the Radiation Protection Ordinance have proven themselves in practice. They permit safe and proper management of material from dismantling and release of the site from supervision under nuclear and radiation protection law. These German regulatory procedures should be taken into account and deregulation and removal should be used as appropriate and necessary tools in the process of decommissioning NPPs in order to return non-hazardous materials to the material cycle or for conventional disposal.

Despite of careful planning of decommissioning projects, there are often surprises when facilities are opened for dismantling purposes, or when material is removed from hot cells, etc. Unexpected incidents and findings during the decommissioning of nuclear facilities have been referred to in the past as unknowns. However, many of the problems encountered during implementation of decommissioning are well known, it is simply that they were not expected to arise. In some other cases, the problem may not have been encountered in the decommissioning team’s experience, forcing the development of new techniques, tools and procedures to address the unexpected problem, with the attendant delays and cost overruns that this often involves. Unknowns in decommissioning cannot be eliminated, regardless of the efforts applied. This is especially the case in old facilities where documentation may have been lost or where modifications were carried out without updates to reports. As a result, when planning for decommissioning, it is prudent to assume that such problems will occur, and ensure that arrangements are in place to deal with them when they arise. This approach will not only improve the efficiency of the decommissioning project, but will also improve the safety of the operations. One of the most common root causes of unexpected events in decommissioning is the lack of detailed design information or missing records of modifications, maintenance issues and incidents during operation. It is therefore necessary to check the completeness of design information in existing plants and to ensure that configuration management techniques are applied at all stages of the lifetime of a plant. In the case of a new plant, archiving samples of materials can be a valuable source of information to support decommissioning planning. During the lifetime of plants, it is likely that modifications will be carried out involving the construction of new buildings. The opportunity should be taken in these circumstances to consider the layout, the physical size and other attributes of the plant to ensure that they do not make decommissioning of existing facilities more difficult and also to optimize the potential for reuse in support of the decommissioning of the whole site, later in the life of the facility. Characterization of all aspects of a plant is essential to reduce the number of unknowns and the likelihood of unexpected events. This characterization should be extensive, but there is a limit to the level of detail that should be sought as the cost versus benefit gain may reduce. Reducing unknowns by retrospectively obtaining physical data associated with a facility is a useful means of characterization, and there are many tools in existence that can be used to carry this out accurately and effectively. Regardless of the efforts that are employed in decommissioning planning, unexpected events should be anticipated and contingency plans prepared. Although the details of the event itself may not be anticipated, its impact may affect safety and environmental discharge, and may or may not involve radiological impacts. Regardless of more serious impacts, unexpected events are likely to result in modifications to the decommissioning plan, incur delays and cost money. Finally, regardless of the status of a facility, whether at the concept stage or at the decommissioning stage of its life cycle, it is never too early to begin thinking and planning for decommissioning.

Laser cutting has many advantages, including high-speed cutting potential, no reaction forces, narrow kerf widths, ease of remote control, and more. This makes it the next generation cutting technology for nuclear decommissioning. For this reason, various groups in countries with nuclear power plants have been working on applying laser cutting to nuclear decommissioning. Our group has also been developing in-air and underwater laser cutting technologies. Previous research has focused on efficiently cutting thicker steels. To accomplish this, a cutting head with a long focusing element with a focal length of 600 mm was utilized. A long focusing head is advantageous for cutting thick objects at high speeds because it can maintain a high power density over a long distance. However, with such a long focused beam, the residual laser power that remains after passing through the target object can cut or damage other unwanted objects located behind the target. Utilizing a short focused element can solve this problem, but if the focal length is too short, the cutting capability will be reduced. In this work, we developed and applied a cutting head that utilizes a focused element with a short focal length of 300 mm. Cutting tests with this head allowed us to cut 10-60 mm thick stainless steel plates at a laser power of 6 kW. We also obtained the maximum cutting speed and kerf width for each thickness while increasing the laser power by 1 kW from 1 to 6 kW. The results obtained in this work are expected to be utilized for safe cutting in future nuclear decommissioning applications.

A large amount of small and medium-sized metal waste is generated during the decommissioning of nuclear power plants (NPPs). Metal waste is mostly contaminated with low-level radioactive, so it needs decontamination for self-disposal and recycling. A large amount of Organic Decontamination Liquid Waste during decontamination will be generated. The generated organic liquid waste is low in concentration, so the decomposition efficiency is low in the decomposition process. A conditioning process is necessary to concentrate at a high concentration. For effective treatment for Organic Decontamination Liquid Waste, the composition of organic liquid waste and conditioning process were analyzed. Organic acids, metal ions, radioactive nuclides, surfactants, etc. are present in the Organic Decontamination Liquid Waste, and suspended solids are sometimes generated by various reactions. According to previous studies, the concentration of organic acids including surfactants obtained results from several tens of ppm to a maximum of 1,000 ppm, so the maximum value of 1,000 ppm was assumed. For the composition and total amount of metal ions, the average value (52.7wt% Fe, 16.3wt% Ni, 15.1wt% Cr, 15.9wt% Mn) of the distribution of metal species removed by the actual decontamination process is applied, and the total amount is 1,000 ppm was assumed. As for the radionuclides, only 60Co and 137Cs, which are expected to be mainly present, were considered, and 60Co was assumed to be 2,000 Bq/g and 137Cs to be 360 Bq/g by referring to the literature. The amounts of suspended solids were assumed to be 500 ppm by referring to the characteristics of the liquid waste generated in the decontamination process of the NPPs. Based on the estimated value, a reaction formula was established and a simulated Organic Decontamination Liquid Waste was prepared. As a result of measurement using an analysis device, the composition of the estimated and simulated Organic Decontamination Liquid Waste had similar values. The conditioning and treatment process largely consists of pretreatment, conditioning, decomposition processes. Organic Decontamination Liquid Waste goes through a pretreatment process to remove impurities with large particles. In the conditioning process, treated water that has passed through the UF/RO membrane system is discharged into the environment. At this time, Concentrated water goes through a decomposition process for processing the Organic Decontamination Liquid Waste, and is discharged to the environment through a secondary RO membrane system. The conditioning process is the low-concentration Organic Decontamination Liquid Waste in the UF membrane system is forming a micelles in an RO membrane system, concentrating it to a high concentration and then go through a recirculation process in the UF membrane system. An experiment was conducted to confirm whether the concentration of surfactants occurred during the conditioning process. As a result of the experiment confirmed that the highly concentrated surfactant formed micelles and was filtered out in the UF membrane system.

Domestic nuclear power plants developed the scaling factors for the radioactive waste generated from 2004 to 2008 for the first time. Afterwards, the effectiveness of continuous application of the scaling factors have been evaluated for newly generated radioactive waste over the past two years. It was confirmed that most of the initially developed scale factors were effective within a factor of 10 principle, which is an acceptable range. The scaling factors were updated using the analysis data base from 2004 to 2016. A scaling factor refers to the calculated abundance ratio between Key (Easy-to- Measure) and DTM (Difficult-to-Measure) nuclide at the time of generation of radioactive waste based on the source term in the reactor of an operating nuclear power plant. The effectiveness of continuous application of scaling factors can be evaluated at regular intervals regardless of operation status or when there are events that change scaling factors during nuclear power plant operation, such as zinc injection, large-scale facility replacement, and long-term shutdown etc. Even in the case of a permanently shut down nuclear power plant in which fuel is withdrawn from the reactor and generation of new nuclides by nuclear fission and radiation has stopped, periodic verification is conducted to confirm whether the scaling factor developed before permanent shutdown can be effectively applied to the radioactive waste generated after permanent shutdown. However, depending on the nuclear power plant decommissioning strategy or conditions, the period of permanent shutdown prior to decommissioning can be very long, so preparations are needed to ensure the appropriateness of scaling factor operation. In the case of domestic nuclear power plants, Kori Unit 1, a light water reactor, was permanently shut down in June 2017, and as a heavy water reactor nuclear power plant, the permanent shutdown of Wolseong Unit 1 was finally decided in December 2019 after twists and turns including large-scale facility replacement and long-term shutdown. In this paper, we have predicted when the scaling factors will change significantly due to radioactive decay and the difference in halflife between the Key and DTM nuclides over time after permanent shutdown. We also have tried to find appropriate countermeasures for the operation of scaling factors during permanent shutdown period, such as updating scaling factors or applying correction factors.

In Korea, many characteristic component facilities and technologies in general experimental areas for non-radiative materials are owned by industry-academia research. Still, no characteristic analysis test technology has been developed for large, intermediate-level decommissioning waste emitted by neutron irradiation. Since Korea plans to decommission nuclear power plants in 2027, securing analysis technology for intermediate-level decommissioning waste is essential. Accordingly, the Korea Research Institute of Decommissioning (KRID) plans to secure an infrastructure (hot cell) to analyze the characteristics of intermediate-level dismantled waste. Afterward, we intend to stably dispose of the waste generated while decommissioning the current Gori Unit 1/Wolseong Unit 1 using the intermediatelevel dedicated hot cell. It aims to secure high-dose/high-radiation decommissioning waste handling technology through intermediate-level hot cells for the first time in Korea, supports domestic nucleardecommissioning projects, and secure and validate procedures related to material characteristics and nuclide analysis of intermediate-level waste. Furthermore, research on intermediate-level radioactive materials is expected to be carried out in cooperation with schools and research institutes.

In the Kori-1 radioactive waste storage, the concentrated waste and spent resin drums generated in the past are repacked and stored in large concrete drums. In order to dispose of radioactive waste generated before the establishment of the waste acceptance criteria, it is necessary to develop a large concrete drum treatment and waste treatment process to evaluate disposal suitability and secure technology that meets the latest technical standards. In addition, for worker safety and waste reduction, it is important to develop secondary waste treatment technology generated during waste treatment. In this study, the types and characteristics of secondary wastes that can be generated when large concrete drums are decommissioned were investigated. In addition, considering the characteristics of possible secondary wastes, suitable treatment methods and characteristic evaluations were analyzed. We plan to develop an optimal process for secondary waste treatment in consideration of on-site work space, economic feasibility, and safety.

Korea currently has two permanent shutdown Nuclear Power Plants (NPPs), and the decommissioning project is expected to begin soon, starting with the first commercial NPP. The decommissioning project will eventually be the disposal of radioactive waste in the final stage of the work, and in that respect, proper tracking and history management should be well established in the management of waste. This is in line with the guidelines that regulatory agencies should also properly manage radioactive waste. Therefore, this study intends to examine the factors that should be considered in terms of tracking and management of radioactive waste in decommissioning nuclear facilities. The starting and final point of tracking radioactive waste generated during decommissioning is the physical inventory of the current as-is state and the final container. In this respect, the tracking of waste starts from the beginning of the dismantling operation. Thus, at the stage of approval of the decommissioning work, it may begin with an ID scheme, such as the functional location in operation for the target System, Structure, and Components (SSCs). As the dismantling work progresses, SSCs will be classified by nature and radiological level, which will be placed in containers in small packaging units. At this time, the small package should be given an ID. After that, the dismantling work leads to the treatment of waste, which involves a series of operations such as cutting, decomposition, melting, and decontamination. Each step in which these tasks are performed will be placed in a container, and ID assignment is also required. Until now, the small packaging container is for transfer after each treatment, and it is placed in the storage container in the final stage, at which time the storage container also gives a unique ID. Considerations for follow-up management were reviewed assuming solid waste, which is the majority of dismantled radioactive waste considered in this study. The ID system should be prepared from the start of the dismantling work, ID generation of the small transporting container and ID generation of the final disposal container during the intermediate waste treatment process, and each ID generation of the previous stage should be linked to each generation stage. In addition, each ID must be generated, and the definition of the grant scheme and attributes is required.