In 2005, groundwater contamination due to unplanned releases of radioactive materials from the US. Nuclear Power Plants (NPPs) such as Braidwood and Indian Point was confirmed. The following year, in 2006, The Nuclear Regulatory Commission (NRC) established a task force team to investigate the history of unplanned release of all NPP in the US. As a results 217 events of unplanned release including leaks and spills were identified in the US NPPs. The NRC regulates the radioactivity concentration of off-site groundwater by setting a reporting levels (RLs), and if exceeds the RLs, the licensee must report within 30 days. When the off-site groundwater is used as drinking water or non-drinking water, the RLs for tritium in groundwater are 740 Bq·L−1 or 1,110 Bq·L−1, respectively. Whereas the NRC does not set the RLs for on-site groundwater. The Nuclear Energy Institute (NEI) issued the guidance document “Industry groundwater protection initiative” NEI 07-07 in 2007. And the members of the NEI promised with regulatory body and local governments to implement groundwater monitoring/protection program according to the NEI 07-07. The document states that when the on-site groundwater is used as drinking water, the RL (740 Bq·L−1) for off-site groundwater will be applied and the licensee voluntarily reported to the NRC. And also, NPPs are setting the Investigation Level (IL) below the RP and the IL is various among the NPPs. The IL is the standard by which detailed investigations are implemented when the level (radioactivity concentration) is exceeded.

There are many Systems, Structures, and Components (SSCs) in Nuclear Power Plants (NPPs). The systems include radiological waste treatment system, spent fuel pool cooling, emergency core cooling systems, etc. The structures include reactor building, piping vaults, radioactive waste storage facilities, etc. The components include valves, pumps, piping segments, etc. Radionuclides exist in some of these SSCs and unplanned release may occur when leaks or spills from them. And also Work Practice (WP) is another reason of unplanned release in NPPs. The WP is defined as an action taken by individuals during maintenance, operational or support activities, which could result in or prevent a spill or leak of a radioactive solid, liquid or gas that has a credible mechanism for contamination of groundwater. According to the results of the Electric Power Research Institute (EPRI) survey, a total of 323 unplanned release event occurred at US NPPs from 1970 to 2014. Among them, 219 events were counted to have occurred at pressurized water reactors (PWRs). In addition, it was confirmed that 41 of the 44 PWR sites (about 93%) in the US, operated at the time of the survey period, had experienced at least one unplanned release events of licensed material which impacted groundwater. This means that the US PWR sites have experienced an average of approximately 5 unplanned release event per site. The source with the most unplanned releases, including SSCs and WP, was miscellaneous systems with a percentage of about 33% (72 events). Miscellaneous systems include pipes, and it was confirmed that unplanned releases mainly occurred in pipes such as the main steam system, condensate and feedwater system, and emergency core cooling system. And the percentage was high in the order of WPs (21%, 45 events), radioactive effluents (20%, 43 events), refueling water storage (8%, 17 events), radioactive waste/material operations (7%, 16 events), spent fuel storage (5%, 12 events), unknown (4%, 9 events), and structures (2%, 5 events). The history of the unplanned release of the US NPPs will be considered when revising major SSCs in the domestic NPP groundwater monitoring program.

In order to monitor the contamination of groundwater due to unplanned release of radioactive materials and the spread to off-site environments, the nuclear power plants (NPPs) conduct groundwater monitoring program (GWMP) in Korea. The GWMP should be established based on the groundwater flow model reflecting the conceptual site model (CSM) of the NPP’s site. In this study, in order to optimize the GWMP, the existing CSM and the groundwater flow model of the domestic NPPs site was updated by reflecting the latest groundwater level. As part of the CSM improvement, the hydrogeological units were subdivided more detailed from three to six through the review of hydrogeological characteristics of the NPPs site. In addition, major variables that affect groundwater flow, such as water conductivity, have been updated. The groundwater flow model was revised overall as the CSM was improved. In particular, the excavation depth of the structure and backfill area generated during the construction stage of the NPP structures was accurately reflected, and the drainage boundary conditions were realistically reflected. To verify the revised groundwater flow model, steady-state correction was performed using the groundwater level measured in April, 2021. As a results of the steady-state correction, the standard error of estimate, root mean square (RMS), normalized RMS, and the correlation coefficient were 0.32 m, 1.692 m, 5.608%, and 0.964, respectively. This means that the groundwater flow model is reasonably constructed. The CSM and groundwater flow model improved in this study will be used to optimize the monitoring location of groundwater in NPPs.

The Kori Unit 1 and Wolsong Units 1, commercial reactors in South Korea, were permanently shut down due to the expiration of their design lifetime. Therefore, nuclear power plants that have been permanently shut down must be dismantled, and the site must be finally released after removing the remaining radionuclides. Domestic regulatory standards for site remediation should not exceed 0.1 mSv per year based on effective dose. In addition, it is necessary to calculate the preliminary Derived Concentration Guideline Levels (DCGL) to prove that the conditions are met. Therefore, in this study, the input factor considering the geological characteristics of the site of Kori Unit 1 was investigated, and the preliminary Derived Concentration Guideline Levels were calculated and compared with the results of previous studies. As a result of comparative analysis, 60Co, 134Cs, and 137Cs, which are gamma-ray emitting radionuclides, had similar values to DCGL of previous studies A and B. However, 63Ni, a beta-rayemitting nuclide, was 5.94×104 Bq·g−1 in this study and 8.47×101 Bq·g−1in previous study B, resulting in a difference of about 700 times. In addition, in the case of 90Sr, this study and previous study A were derived similarly, but this study was 5.34×101 Bq·g−1 and previous study B was 1.18×10−1 Bq·g−1, resulting in a difference of about 450 times. This difference is judged to be because, unlike this study using only the industrial worker scenario, in the case of previous study B, the resident farmer scenario was mixed and used, which considers the internal exposure caused by ingestion of food produced in the contaminated area. In this study, it was confirmed that DCGL according to the change of geological factors of the site did not have a significant effect on gamma-ray-emitting nuclides. However, it was confirmed that considering the intake of food affects the DCGL of beta-ray-emitting nuclides. Therefore, there is a need to conduct future studies applying intake input factors that meet domestic conditions.

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.

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.

For transport containers for radioactive wastes, a drop test should be performed at a height of 0.3– 1.2 m on a rigid target depending on the weight as a normal condition in the regulation. In the drop test, a strain gauge is commonly used to measure the local strain, and the position of the strain gauges is determined by the experiences of the engineer in advance of the test. For this reason, the strains can be measured at only predetermined points. The DIC (Digital Image Correlation) method using highspeed cameras can be used to measure the change in strain over the region of interest. In addition, it is possible to measure effectively even in areas with high strain gradients that are difficult to measure with strain gauges. Therefore, the DIC method can measure the strain change according to time over the entire load path. When the drop test of the transport container is performed, the impact load is delivered through the lower corner fittings-corner posts-upper corner fittings-lids. In this study, white spray was sprayed on these main load path, and black speckles were created on the spayed surface to trace the rigid motion of speckles. The images taken during the drop test can be used to create a strain field over region of interest.

In this study, a drop analysis of metallic disposal containers for radioactive wastes is performed according to accident scenarios at the disposal site. The weight of the disposal container is about 8 tons, and the ingot-type wastes are loaded in the disposal container. To simulate the floor of the disposal site as the impact target, the reinforced concrete pad is modeled. High impact energy of the disposal container due to their heavy weight and high drop height causes excessive deformation and failure of the concrete target having relatively weak strength. Dynamic growth of cracks due to such failures causes penetration and delamination of concrete. Since the impact force delivered to the container strongly depends on the failure of the concrete pad, it is important to properly simulate the failure of the concrete in the drop analysis. A material erosion method can be used to simulate the concrete failure. In the case of applying erosion based on the finite element method (FEM), the element is deleted when the element exceeds a certain criterion, which causes material and energy loss problem. To solve this problem, mesh-free methods such as smoothed particle hydrodynamics (SPH) can be commonly used, but the mesh-free method has the disadvantage of incurring high numerical cost. Therefore, an adaptive method combining SPH and FEM-based SOLID elements is used for concrete target modeling to simulate excessive deformation and failure of the concrete target. In the adaptive coupling method of SPH and SOLID, the concrete target is first modeled as a solid element. When the damage of concrete exceeds the failure criterion, the solid element is eroded and the SPH element replacing the solid element is activated. Since the activated SPH element continues to participate in the impact, the problem of loss of materials and energy can be effectively solved. In this way, analysis results consistent with actual physical phenomena can be obtained.

This paper presents a strategic adoption model for blockchain technology in nuclear nonproliferation by analysing the implementation of legally binding agreements and leveraging results from governmentleading sectors. Blockchain has been emerging as not only a single promising technology but a foundational one which can be combined with diverse sectors. From the national point of view, it is imperative that the government formulates policy for fostering blockchain-related industries, thereby, gaining a competitive advantage at the national level. Accordingly, the Korean government has established the Blockchain Technology Development and Diffusion Strategies in 2018 and 2020, respectively, to verify the technology by supporting pilot projects for apposite industries, such as customs clearance, transhipment of containers, record-keeping of meat processing, and smart contracts. In addition, the strategies announce to support liaison with regulatory sandbox and cooperation between the projects. Internationally, on the other hand, nuclear nonproliferation imposes the duties of verifying that member states under the NPT and the Safeguards Agreement obey the IAEA mandate, “Atoms for Peace and Development”. Similarly, bilateral nuclear cooperation agreements and administrative arrangements specify reporting obligations for the origin and history records of the Trigger List items. Meanwhile, commercial and industrial secrets and other confidential information of any entities involved have to be securely protected. Provided accompanying activities accomplish the integrity of records and mutual transparency, it brings more credibility, and further, the competitiveness of the state’s nuclear industry. In conclusion, the tasks that the Republic of Korea implements as an exemplary country complying with the nuclear nonproliferation regime have many similarities with the pilot projects that have been or are being carried out under national strategies for fostering blockchain technology elsewhere. This implies that the leveraging of the subsets can derive a new competitive model in blockchain adoption that contributes to the competitiveness of the national nuclear industry due to the advanced nuclear regulations.

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.