The development of separation method of radioactive tritium is imperative for treating tritiumcontaminated water originating from nuclear facilities. Polymer electrolyte membrane electrolysis technology represents a promising alternative to conventional alkaline electrolysis for tritium enrichment. Nevertheless, there has been limited research conducted thus far on the composition of membrane electrode assemblies (MEAs) specifically optimized for tritium separation, as well as the methods used for their fabrication. In this study, we conducted an investigation aimed at optimizing MEAs specifically tailored for tritium separation. Our approach involved the systematic variation of MEA components, including the anode, cathode, porous transport layer, and electrode formation method. The water electrolysis efficiency and the H/D separation factor in deuterated water (1%) were evaluated with respect to both the preparation method and the composition of the MEA. To assess the long-term stability of the MEAs, changes in cell voltage, resistance, and the active electrode area were analyzed using impedance analysis and cyclic voltammetry. Furthermore, we examined H/D separation factor both before and after degradation. The results showed that MEAs with different anode/cathode configurations and electrode formation methods improved the electrolysis efficiency compared to commercial MEAs. In addition, the degree of change in the resistance value was also different depending on the electrode formation method, indicating that the electrode formation method has a significant impact on the stability of the electrolysis system. Therefore, the study showed that the efficiency and long-term stability of the water electrolzer can be improved by optimizing the MEA fabrication method.

Hydrogen isotope separation involves the separation of hydrogen, deuterium, tritium, and their isotopologues. It is an essential technology for removing radioactive tritium contamination and for obtaining valuable hydrogen isotope resources. Among various hydrogen isotope separation technologies, water electrolysis technology exhibits a high separation factor. Consequently, the electrolysis of tritiated water is of paramount importance as a tritium enrichment method for treating tritium-contaminated water and for analyzing tritium in environmental samples. More recently, hydroelectrolysis technology, which utilizes proton exchange membranes (PEM) to reduce water inventory, has gained favor over traditional alkaline hydroelectrolysis. Nevertheless, it is crucial to decrease the hydrogen permeability of the PEM in order to mitigate the explosion risk associated with tritium hydrogen electrolysis devices. Additionally, efforts are needed to enhance the hydrogen isotope selectivity of the PEM and optimize the manufacturing process of the membrane-electrode assembly (MEA), thereby improving both hydrogen isotope separation performance and water electrolysis efficiency. In this presentation, we will delve into two key aspects. Firstly, we’ll explore the reduction of hydrogen permeability and the enhancement of the hydrogen isotope separation factor in PEM through the incorporation of 2D nanomaterial additives. Secondly, we’ll examine the influence of various MEAs preparation methods on electrolysis and isotope separation performances. Lastly, we will discuss the effectiveness of the developed system in separating deuterium and tritium.

Some consumer goods containing radioactive substances are in circulation and used in everyday life. In accordance with the Nuclear Safety Act, consumer goods with radioactivity are regulated. However, since most consumer goods distributed in Korea have no information that can confirm the amount of radiation, it is necessary to analyze the radiation for safety regulation. Among these consumer goods, GTLS (Gaseous Tritium Light Source) contains gaseous tritium (tritium, written as 3H or T), which is a radioactive material. The gaseous composition ratio in GTLS was analyzed using a precision gas mass spectrometer (Thermo Fisher, model MAT 271). As a result of GTLS analysis, the H2, HD or H3 +(T) or 3He, HT or D2 or He, DT, and T2, which correspond to the mass-to-charge ratio (m/z) 2 to 6 and the air components were detected. In addition, substances corresponding to m/z=24 and m/z=21 were also detected. These were compared with pure CH4 and those fragmentation patterns. The ratios of CT4 (m/z = 24) to CT3 (m/z = 21) and CH4 (m/z = 16) to CH3 (m/z = 15) were compared and they agree within the measurement uncertainty. We also performed additional experiments to separate the water component in the GTLS samples, considering the possibility that the m/z = 21 to m/z = 24 region is tritium compounds based on H2O. Despite the removal of the water components, peaks were detected at m/z=21 and m/z=24. Therefore, we confirmed that the component of m/z = 24 in the GTLS sample was CT4.

Tritium is a radioactive isotope of hydrogen with a half-life of about 12.3 years, and it is commonly found in the environment as a result of the production of Nuclear Power Plants. The World Health Organization (WHO) has established guidelines for the permissible levels of tritium in drinking water. The guideline value for tritium in drinking water is 10,000 Bq/L. It is important to note that the guideline value for tritium is not a legal limit, but rather a recommendation. National and local authorities may establish legal limits that are more restrictive than the WHO guideline value based on local conditions and risk assessments. The Australia and Finland have set a limit for tritium in drinking water at 76,103 Bq/L and 30,000 Bq/L respectively, which is more than three to seven times higher compare to guideline value of WHO. The United States Environmental Protection Agency (EPA) has set a maximum contaminant level (MCL) for tritium in drinking water at 20,000 picocuries per liter (pCi/L), which is equivalent to 740 Bq/L. The Health Canada has set a guideline value for tritium in drinking water at 7,000 Bq/L. Assuming drinking water corresponding to each tritium limit (or guideline value) for one year, the expected exposure dose is 0.01 mSv to 1 mSv. It means that the tritium in drinking water below the limits or guideline value does not pose a significant risk to human health.

In this study, four technologies were selected to treat river water, lake water, and groundwater that may be contaminated by tritium contaminated water and tritium outflow from nuclear power plants, performance evaluation was performed with a lab-scale device, and then a pilot-scale hybrid removal facility was designed. In the case of hybrid removal facilities, it consists of a pretreatment unit, a main treatment unit, and a post-treatment unit. After removing some ionic, particulate pollutants and tritium from the pretreatment unit consisting of UF, RO, EDI, and CDI, pure water (2 μS/cm) tritium contaminated water is sent to the main treatment process. In this treatment process, which is operated by combining four single process technologies using an inorganic adsorbent, a zeolite membrane, an electrochemical module and aluminumsupported ion exchange resin, the concentration of tritium can be reduced. At this time, the tritium treatment efficiency of this treatment process can be increased by improving the operation order of four single processes and the performance of inorganic adsorbents, zeolite membrane, electrochemical modules, and aluminum- supported ion exchange resins used in a single process. Therefore, in this study, as part of a study to increase the processing efficiency of the main treatment facility, the tritium removal efficiency according to the type of inorganic adsorbent was compared, and considerations were considered when operating the complex process.

Nuclear fusion energy is considered as a future energy source due to its higher power density and no emission of greenhouse gas. Therefore, various researches on nuclear fusion is being conducted. One of the key materials for the nuclear fusion research is tritium because the D-T reaction is the main reaction in the nuclear fusion system. However, that tritium can also be used for non-peaceful purposes such as hydrogen bombs. Therefore, it is necessary to establish the safeguards system for tritium. In that regards, this study analyzed the possibility of applying safeguards to tritium. To achieve this objective, the tritium production capacity through the light water reactor was analyzed. Tritium Production Burnable Absorber Rod (TPBAR) was modeled through the MCNP code, and tritium production was analyzed. The TPBAR is composed of a cylindrical tube with a double coating of aluminum and zirconium, filled with a sintered lithium aluminate (LiAlO2) pellet to prevent the release of tritium. Tritium is produced by the reaction of Li-6 in the TPBAR with neutrons, and it is extracted and stored at the Tritium Extraction Facility (TEF). As a result, the tritium production increased as the burnup and Li-6 mass increased. In addition, when the tritium produced in this way was transferred to TEF and extracted through the process, the application of safeguards measures was analyzed. To this end, various safeguards measures were devised, such as setting an Material Balance Area (MBA) for TEF and analyzing Material Balance Period (MBP). As there is no designated Significant Quantity (SQ) for tritium, cases were classified based on the type and form of nuclear weapons to estimate the Sigma MUF (Material Unaccounted For) of the TEF. Finally, the comprehensive application of safeguards to tritium was discussed. This research is expected to contribute to the establishment of IAEA safeguards standards related to tritium by applying the findings to actual facilities.

The separation of hydrogen isotopes is a critical issue in various fields, such as deuterium or tritium production and the treatment of radioactively contaminated water. In this presentation, we describe the pervaporative separation of hydrogen isotopes using proton conductive membranes and underlying separation mechanism. We investigated the H/D separation factors of perfluorosulfonic acid (Nafion) and polybenzimidazole membranes using pervaporation, and found that both membranes exhibited similar separation factors of approximately 1.026. Water permeation flux through the membranes was highly dependent on their thickness and type, and increased with operation temperature. However, the effect of temperature on H/D separation factor was negligible. We also demonstrated the cascade separation of H/D, indicating the potential application of multi-stage operation. We found that surface transport mechanisms such as hydron hopping contributed the most to H/D separation during the pervaporation process of proton conductive membranes.

In case of Korea, unlike overseas nuclear power plants, adjacent units are located in permanently stopped nuclear power plants. Radioactive substances from airborne and liquid effluents are released into the environment from the NPP, and the radioactivity of the released substances must be reported to the regulatory authorities. Radioactive effluents are released into the environment not only in operation but also after permanent shutdown. Due to domestic conditions in which multiple units exist on the same site, it is necessary to consider radioactive effluents generated after permanent shutdown of NPPs. In particular, liquid effluent may have an increased tritium concentration due to draining the spent fuel pool. This paper summarizes the annual liquid emissions of PWR power plants that have been permanently shut down. The data was obtained from the Nuclear Regulatory Commission’s (NRC) annual radioactive effluent release report, which provides information on the annual emissions power plants into the environment. The liquid emissions of each plant were organized into an annual table, providing an overview of the amount of liquid released by each plant. This study aims to raise awareness about the potential environmental impact of permanently shut down nuclear power plants and the need for proper management of their liquid emissions. The findings of this study can used by operator, policymakers, and other stakeholders to make informed decisions regarding the decommissioning and management of nuclear power plants.

Though many treatment technologies of contaminated water have been developed for a long time, it is still difficult to find a suitable method for large volumes of low radioactivity tritium-contaminated water. For this reason, most of the tritium-contaminated water been discharged to the biosphere or been stored in a special control area as radioactive waste. Activated carbon is a common material, but since there are few data on the treatment of tritium-contaminated water, its adsorption behavior to HTO is worth studied. In our study, for the tritium-contaminated water having a low radioactivity concentration (350-480 Bq/g), adsorption experiments were performed with activated carbon. The effects on the selective adsorption of HTO were investigated for temperature (5-55°C), hydrogen peroxide (1-10wt%) and activated carbon reuse (1-6 times) under non-equilibrium conditions. The treatment of activated carbon significantly reduced the radioactivity of tritium-contaminated water around 60 minutes of adsorption time. In order to clearly analyze the experimental results, positive factors and negative factors on the HTO selectivity were separately evaluated according to the adsorption time. Temperature and the reuse of activated carbon were evaluated as negative factors for HTO selectivity of activated carbon, whereas hydrogen peroxide (> 5wt%) was evaluated as a positive factor. By the evaluation method of separating the influencing factors into two types, the adsorption experimental results of HTO could be understood more clearly.

HANARO, a multi-purpose research reactor, uses a reflector as heavy water to obtain high neutron flux. Therefore, two ion exchangers were installed to manage the heavy water quality of the reflector system. The operator of HANARO manages it according to the limit value (Conductivity: less than 0.5 mS/m, pH: 5.5~6.5), and if the limit value is not satisfied, the resin must be replaced. The reflector system is in the enclosed structure and it is designed to delay the release of tritium to the outside. Tritium is produced by a nuclear reaction between neutrons and deuterium. Tritium is inhaled into the body in the form of water or vapor, which is likely to cause internal exposure problem. In addition, since tritium spreads to other regions, thorough management is required. Therefore, HANARO measures and manages tritium in Rx and RCI using the bubbler collection method. In this paper, the change in the behavior of tritium due to the replacement of the reflector ion exchanger resin was analyzed. Due to the increase in conductivity of the reflector, the ion exchanger resin was replaced on March 3, 2022. Therefore, the concentration of tritium was measured to be about 5 times higher than usual. It did not exceed the emission limit, and the concentration values of tritium is stably managed by constant monitoring and analysis.

Water electrolysis is an efficient method to enrich heavy hydrogen isotopes (tritium and deuterium) in the aqueous phase. Although an alkaline water electrolyzer has been commercialized for mass production of hydrogen, such a method requires additional purification steps to remove electrolytes from the final concentrates. On the other hand, proton exchange membrane water electrolysis (PEMWE) does not require additional electrolyte treatment steps, and PEMWE is operated at higher current density compared to the alkaline water electrolysis. In this study, we investigated deuterium and tritium separation from light water by PEMWE. Separation behaviors at the anode and cathode were analyzed, and H/D and H/T separation factors were compared.

Hydrogen isotopes (H, D, T) separation technologies have received great interest for treatments of tritiated liquid waste produced in Fukushima. In addition, the separated deuterium and tritium can be utilized in various industries such as semiconductors and nuclear fusion as expensive and rare resources. However, separating hydrogen isotopes in gas and liquid forms still requires energyintensive processes. To improve efficiency and performance of hydrogen isotope separation, we are developing water electrolysis, cryosorption, distillation, isotope exchange, and hydrophobic catalyst technologies. Furthermore, an analytical method is studied to evaluate the separation of hydrogen isotopes. This presentation introduces the current status of hydrogen isotope research in this research group.

Water electrolysis is a representative technology for tritium enrichment in water. Proton exchange membrane (PEM) water electrolysis has received great attention to replace traditional alkaline water electrolysis which generates concentrated tritiated water containing a large amount of salts. Nafion has been widely used as a polymeric electrolyte for the PEM electrolyzer. However, its low gas barrier property causes explosion, corrosion or degradation of electrolyzer. Furthermore, the traditional polymeric electrolytes have negligible differences in conductivity between hydrogen isotopes. To enhance the tritium separation by water electrolysis, we designed a composite membrane (Nafion/ hexagonal boron nitride (hBN)). The monolayer hBN has a high proton conductivity and gas barrier property, and the hBN can enhance conductivity differences between hydrogen isotopes. We prepared Nafion/hBN composite membranes, and water electrolysis performances and proton/deuterium separation behaviors were investigated.

North Korea claimed to have tested a hydrogen bomb in its fourth nuclear test in 2016, and declared that the hydrogen bomb was completed after the sixth nuclear test in 2017. North Korea’s operation of Yongbyon Graphite-moderated reactor has been thought to be aimed at producing plutonium, but it has been strongly argued that the restart of the Graphite-moderated reactor is, indeed, aimed at supplying tritium recently. Tritium can be used not only to manufacture hydrogen bombs, but also to miniaturize nuclear weapons, making it as a key material for nuclear weapon capability. Since upgrading nuclear weapons and developing hydrogen bombs through the use of tritium by North Korea could pose a major threat to the security of the Korean Peninsula, it is important to accurately evaluate North Korea’s nuclear weapon capabilities through the analysis of nuclear material production scenarios based on its nuclear facilities. However, researches on North Korea’s nuclear materials such as HEU (Highly Enriched Uranium) and Pu production has been actively conducted, while no research has been shown on tritium production yet. Therefore, this study aims to evaluate the tritium productivity based on the analysis of hypothetical nuclear material production facilities and possible tritium production scenarios. Basic research was conducted about the existing theoretical methodology for tritium production, the analysis of the global tritium production history, and the analysis of nuclear facilities. Based on this basic investigation, feasible tritium production scenarios were constructed. Subsequently, based on design criteria of an hypothetical Graphite-moderated reactor, possible tritium production scenario was modeled by applying the TPBAR (Tritium Production Burnable Absorber Rod). In addition, the factors such as 6Li concentration, design parameters, material compositions, and the number of TPBARs, which may affect tritium throughput were analyzed in terms of sensitivity study such that the maximum and minimum throughput can be predicted.

Detritiation of low-level tritiated water has become global issue after Fukushima accident. Several attempts have been made to reduce the radioactivity of Fukushima tritiated water below legal limit of nuclear plant effluents (~104 Bq·L−1). Various technologies such as water distillation, electrolysis, and catalytic exchange were tested to treat the tritiated water, however, those demand enormous expense to achieve the goal due to low process efficiency. It highlights that the performance enhancement of current technologies is necessary to improve economic feasibility. We have quantitatively evaluated the separation performance of various polymers toward low-level tritium (~105 Bq·L−1) through batch experiments. The polystyrene with grafted by 20 types of functional groups (Tris (2-aminoethyl) amine, dimethylaminomethyl, isocyanate, mercaptomethyl, aminomethyl, hydroxymethyl, triphenylphosphine, morpholine, 2-chlorotrityl amine, 4-(dimethylamino) pyridine, poly (vinyl chloride) carboxylated, poly (4-vinyl pyridine), p-toluenesulfonic acid, p-toluenesulfonyl hydrazide, piperidine, acetyl polystyrene, 2-chlorotrityl chloride, piperazine, diethylene triamine, poly (vinyl chloride)) were suspended in HTO solution (initial activity = 4.7 × 105 Bq·L−1). After the equilibration, the suspension was filtered using 3 kDa membrane filter and the activity in filtrates were quantified by LSC (HIDEX-300 SL). The results demonstrate the detritiation efficiency and separation factors of functional groups toward tritium. Carboxylic group (COOH) showed the most reactive performance as detritiation efficiency of ~4%. Compared to other functional groups, styrene sulfonyl groups including sulfonyl amide (SNH2) and sulfonyl hydrazide (SNHNH2) revealed promising performance for tritium separation as separation factor of 10.97 and 3.85, respectively. However, sulfonyl hydroxide (SOH) which is known as reactive functional group to tritium exchange showed the poor performance (detritiation efficiency: 0.68%; separation factor: 3.02). This study could suggest the promising functional groups for detritiation of low-level tritiated water which can be utilized to enhance the performance of current technologies. For example, reactive functional groups can be grafted on the surface of packing material within distillation tower resulting in the increasing detritiation efficiency.