The decommissioning of nuclear power plant (NPP) generates large amount of waste. Since the most of the concretes are slightly surface contaminated, the accurate characterization and regionspecific surface decontamination are important for the efficient waste management. After the effective surface decontamination and separation, most of the concrete waste from decommissioning of NPP can be classified as a clearance waste. Various surface characterization and decontamination technologies are suggested. The mechanical technologies are simple and offers direct application. The laser-based technologies offer efficient separation and surface contamination. The high price, however, hesitates the application of the process. The nitro-jet technology, which is based on the evaporation of liquid nitrogen, allows the effective decontamination. However, the high price and uncertainty of large are application hinders the practical application in NPP decommissioning. In this paper, various technologies for characterization, handling, treatment, etc., will be discussed. The advantages and disadvantages of the technologies will be discussed, in terms of practical applications.

During the decommissioning of nuclear power plant (NPP), massive amount of concrete wastes is generated, which are non-radioactive and radioactive. The concrete is a representative construction material which affords reliable structural stability, good formability, and trustful integrity. Also, its reasonable neutron absorbing property allows the various application for many components, including building construction material, bio-shield concrete, etc. Due to the noted aspects of concrete, the radiological concrete characterization is classified as an important process for development of effective strategy for concrete management, in terms of process management and financial control during the decommissioning. The characterization of bio-shield concrete is important in waste management. The understanding and characterization of activation depth is essential for the determination of waste management strategy, classification of bio-shield concrete, and process development of decommissioning. On the other hand, concrete for construction application requires the evaluation of surface contamination of them. The concrete for containment building and its structure is rarely activated, but surface contaminated. In this paper, the reactor data from representative PWR reactors in the US is studied. The experience on Yankee Rowe, Maine Yankee, and Connecticut Yankee NPPs are systematically studied. The Yankee Rowe was a 4-loop PWR of Westinghouse design with 185 MWe. The Main Yankee was a 3- loop PWR of Combustion Engineering design with 864 MWe. The Connecticut Yankee was a 4-loop Westinghouse type with 560 MWe. The characterization studies on bio-shield concrete will be discussed in this paper, including activation depth, primary nuclides, etc.

The Fukushima nuclear power plant accident, which was caused by the Great East Japan Earthquake on March 11, 2011, is of great concern to the Korean people. The scope of interest is wide and diverse, from the nuclear accident itself and the damage situation, to the current situation in Fukushima Prefecture and Japan, and to the safety of Japanese agricultural and fishery products. Concerns about nuclear safety following the Fukushima nuclear accident have a significant impact on neighboring nation’s energy policy. It has been 11 years since the Fukushima nuclear accident. In neighboring nation society, the nature and extent of damage caused by the Fukushima nuclear accident, the feasibility of follow-up measures at home and abroad, the impact on neighboring nations, and the direction of nuclear policy reflecting the lessons of the accident are hotly debated topics. Recently, the controversy has grown further as it is intertwined with Japan’s concerns about the safety and discharge of the contaminated water into the sea, and conflicts over domestic nuclear power policies. About 1.29 million tons, as of March 24, 2022, of the contaminated water are generated, which is close to the 1.37 million tons of water storage capacity. In response, the Japanese government announced on April 13, 2021, that it plans to discharge the contaminated water into the sea from 2023. This study evaluates the amount of the contaminated water that has passed through the ALPS and reviews the preparations and related facilities for ocean discharge after diluting the contaminated water. In addition, it is intended to forecast the various impacts of ocean discharge.

Numerous nuclear power plants that had been built in the late 20th century have entered the aging phase and are scheduled to be decommissioned. The decommissioning project of a commercial nuclear power plant is an array of complex processes involving the activities of site characterization, decontamination, dismantling, and site restoration. Hence, a number of essential factors, such as scheduling, work progress, and staffing, should be taken into account while the decommissioning plan is drafted and modified. Guidances on managerial and social aspects of decommissioning have been rare as compared to those of technical viewpoints. Nonetheless, the nuclear industry in the US has presented no little amount of experience on their decommissioning projects dealing with those perspectives. Thus, three sets of the case study were conducted to obtain useful lessons learned. The Maine Yankee nuclear power plant initially acquired 40 years of the operating license, it was in operation for only 25 years from 1972 until 1996. The owner group decided to shut down because of the deterioration of the profitability in 1997. The case of the Maine Yankee project enlightened the importance of the contract management and stakeholder relations. The Rancho Seco nuclear power plant is a single-unit nuclear power reactor site with 913 MWe output that commenced commercial operation in 1975. The Rancho Seco that had become the first-ever reactor shut down by a public voting introduced several innovative approaches for the decommissioning, some of which turned out to be very successful. The SONGS 1 commenced the commercial operation in 1968 and had been decided to cease its operation permanently due to a steep decline in profitability in 1992. The SONGS 1 presented worthwhile lessons in terms of project management. In this study, several lessons learned related on managerial, engineering, and regulatory/social aspects considered during the NPP decommissioning will be reviewed and discussed.

During the normal operation boron concentrates and spent resins are generated. The boron concentrates are treated by concentrated waste drying system (CWDS) and results in fine powder form. The solidification or application of high integrity container (HIC) is required for the disposal of the dried boron concentrates. The spent resin is stored in storage tank after the water treatment. The spent resin also requires solidification or application of HIC to satisfy the waste acceptance criteria (WAC) in Korea. The solidification process requires periodic validation. The repeated validation and complicated process hesitates the practical application. The application of HIC offers various advantages, including flexible free standing water requirement, higher waste loading compared to solidification, and simple process. The polymer concrete (PC), which is a primary component for PC-HIC exhibits good material stability. The expected transportation mechanism of nuclide in the PC-HIC are 1) diffusion by concentration, 2) permeation by pressure, and 3) capillary suction when considering the disposal condition. Since the PC-HIC effectively prevents the intrusion of neighboring water and volume of free standing water is lower than 1%, it seems that diffusion by concentration is the primary transportation mechanism. In this study, the property of PC is investigated based on Cl ion diffusion test to evaluate the material reliability. The results indicate that PC exhibits superior stability compared to ordinary portland cement. In addition, the reliable life time of PC is estimated base on the element transportation phenomena.

The permanent shut-down of Kori unit 1, the first nuclear power plant (NPP) in Korea, generates various radioactive waste. They are dry active waste (DAW), spent resin, concentrated waste, activated metals, etc. During normal operation of NPP, activated metals are rarely generated. The decommissioning of NPP, however, generates massive amount of metallic waste including activated metals and contaminated metals, while normal operation generates small amount of metallic waste. The reactor vessel and internals are relatively highly activated components in NPP. Since they are exposed to the high concentration of neutrons during the operation, their contains relatively high radioactive nuclides. They activation analysis is usually performed to understand the radiological inventory of the activated reactor vessel and internal. The results offer various important information including, radiological inventory, waste classification, etc. The impurities in the carbon steel and stainless steel have a great impact on the radiological inventory of the activated metals. The cobalt, nickel, niobium are primary elements that affects the activation analysis and waste classification. Especially, the cobalt, which transforms to 60Co, plays an important role. The 60Co, strong gamma emitter, affects the waste classification, safety analysis of decommissioning workers, and determination of segmentation and package plans. In this paper, effects of impurity concentration on activation analysis is studied. The expected impurity from various sources, including NUREG/CR-3474, commercial NPP data, etc, and effects will be demonstrated. Also, the comparison between results and international experiences will be followed.

HIC refers to a radwaste packaging container that can maintain integrity for more than 300 years in the general underground environment and disposal conditions in Korea. For HIC, the integrity of containers is verified according to the HIC regulation guideline for LLW and ILW disposal. Existing material tests include mechanical stability, permeability resistance, corrosion properties, chemical durability and biological resistance. In this study, a chemical durability test was conducted to prove the suitability of the HIC material by measuring the degree of chemical influence other than corrosion from the disposal environment. The chemical resistance evaluation method was used to simulate the disposal environment in the underground repository, and the amount of change in the physical properties of the degraded polymer concrete specimens according to the test time was confirmed. The technical standards considered leaching of material components, sulfation attack, acid attack, alkali, carbonate, and salt crystallization. The compressive strength and weight change of the specimens with time were checked by immersing them in a chemical solution that could leak major hazardous substances and wastes in the groundwater of the repository for several months. In addition, in order to evaluate the integrity in condition severe than the disposal environment, a flow was applied to a chemical solution having a concentration twice that of the basic chemical resistance test conditions, and the test period was extended twice to accelerate the deterioration of the specimen.

The Korea Nuclear Safety Act defines a high integrity container (HIC) as “a radioactive waste packaging container that can maintain its integrity for more than 300 years under the general underground environment and disposal conditions in Korea”, and detailed technical standards are not described. The US Nuclear Safety Commission’s “Low-Level Waste Licensing Branch Technical Position on Waste Form” describes the detailed requirements for solidification and HIC. The main contents of the US NRC technical position include limiting the free standing water, minimum design life, demonstrating mechanical, thermal and radiation stability, etc. In this study, the stability evaluation was performed to understand the mechanical strength with respect to horizontal and vertical loads. The basic property of polymer concrete was carefully evaluated, including compressive strength, structural fatigue resistance, etc. The long term creep test, loading of 40% of compressive strength, indicates that the polymer concrete exhibits good long term mechanical integrity.