During the dismantling of nuclear facilities, a large quantity of radioactive concrete is generated and chelating agents are required for the decontamination process. However, disposing of environmentally persistent chelated wastes without eliminating the chelating agents might increase the rate of radionuclide migration. This paper reports a rapid and straightforward ion chromatography method for the quantification of citric acid (CA), a commonly used chelating agent. The findings demonstrate acceptable recovery yields, linearities, and reproducibilities of the simulated samples, confirming the validity of the proposed method. The selectivity of the proposed method was confirmed by effectively separating CA from gluconic acid, a common constituent in concretes. The limits of detection and quantification of the method were 0.679 and 2.059 mg·L−1, respectively, while the recovery yield, indicative of the consistency between theoretical and experimental concentrations, was 85%. The method was also employed for the quantification of CA in a real concrete sample. These results highlight the potential of this approach for CA detection in radioactive concrete waste, as well as in other types of nuclear wastes.

The homogeneity of radioactive spent ion exchange resins (IERs) distribution inside waste form is one of the important characteristics for acceptance of waste forms in long-term storage because heterogenous immobilization can lead to the poor structural stability of waste form. In this study, the homogeneity of metakaolin-based geopolymer waste form containing simulant IERs was evaluated using a laser-induced breakdown spectroscopy (LIBS) and statistical approach. The cation-anion mixed IERs (IRN150) were used to prepare the simulant spent IERs contaminated by non-radioactive Cs, Fe, Cr, Mn, Ni, Co, and Sr (0.44, 8.03, 6.22, 4.21, 4.66, 0.48, and 0.90 mg/g-dried IER, respectively). The K2SiO3 solution to metakaolin ratio was kept constant at 1.2 and spent IERs loading was 5wt%. For the synthesis of homogeneous geopolymer waste form, spent IERs were mixed with K2SiO3 solution and metakaolin first, and then the fresh mixture slurry was poured into plastic molds (diameter: 2.9 cm and height: 6.0 cm). The heterogeneous geopolymer waste form was also fabricated by stacking two kinds of mixtures (8wt% IERs loading in bottom and 2wt% in top) in one mold. Geopolymers were cured for 7d (1d at room temperature and 6d at 60°C). The hardened geopolymers were cut into top, middle, and bottom parts. The LIBS spectra and intensities for Cs were obtained from the top and bottom of each part. Cs was selected for target nuclide because of its good sensitivity for measurement. Shapiro-Wilk test was performed to determine the normality of LIBS data, and it revealed that data from the homogeneous sample is normal distribution (p-value = 0.9246, if p-value is higher than 0.05, it is considered as normal distribution). However, data from the heterogeneous sample showed abnormal distribution (p-value = 7.765×10-8). The coefficient of variation (CoV) was also calculated to examine the dispersion of data. It was 31.3% and 51.8% from homogeneous and heterogeneous samples, respectively. These results suggest that LIBS analysis and statistical approaches can be used to evaluate the homogeneity of waste forms for the acceptance criterion in repositories.

Complexing agents used at various nuclear facilities exist in low- and intermediate level radioactive wastes deposited in the repository site. In addition these will be generated through the degradation of the wastes such as cellulose materials. The presence of chelating agents may possibly affect the safety of the wastes repository by promoting the migration of radionuclides into geosphere. Thus, under Nuclear Safety and Security Commission’s Notice No. 2021-16, the contents of chelating agents in radioactive wastes are required to be determined for the secured disposal. UV-Vis method based on an enzymatic reaction was proved to be in adequate to analyze citric acid in radioactive wastes with complex matrix, especially for concrete. A rapid automated method using ion chromatography (IC) for analysis of citric aicd in concrete samples is developed. This automated method enables a sample solution to measure without pretreatment and a target substance to separate from other concrete admixtures. Also, the developed method here, for radioactive concrete wastes was successfully applied to real samples with lowering a limit of quantification value.

Cardiovascular disease remains as one of the most common causes of high morbidity and mortality worldwide, despite remarkable medical advances in recent decades. Non-invasive techniques play a preeminent role in prevention of cardiovascular disease by diagnosing it at an early stage and guiding optimal patient management. Nuclear imaging is one of the most powerful means available for noninvasive diagnosis and management of poorly perfused myocardial region resulting from the cardiovascular disease. Several radionuclides are available for monitoring blood flow to cardiac tissue. The most validated radionuclides for these measurements are 13N, 15O, 99mTc, 201Tl and 82Rb. Each of 13N, 15O and 201Tl require the presence of an on-site cyclotron, whereas, 82Rb and 99mTc require only a generator. Rubidium (Rb) is an alkali metal ion that acts biologically like potassium and accumulates in cardiac muscle tissue. Rb has a rapid blood clearance profile which allows the use of 82Rb. It also has an ultra-short physical half-life of 75 sec for non-invasive evaluation of regional cardiac blood flow. There are several advantages of 82Rb over other radionuclides. Having a short half-life significantly reduces the radiation dose to the patient. In addition, 82Rb is a positron emitter, which gives the full advantages of PET such as image quantification with superior sensitivity. Several reports have shown superior diagnostic performances of 82Rb-PET over conventional 99mTc-SPECT. 82Rb can be produced from a generator system by the decay of its 25.6-day half-life parent 82Sr. However, the 82Sr parent is difficult to prepare. In routine generator production, certain purity is required to meet the specification of the product. Since there has been no the use of 82Rb radionuclide for research or medical purpose in Korea, we have plans to produce 82Sr with certain purity and develop a 82Sr/82Rb generator system. These studies can also be applied to remove radioactive Sr from radioactive waste waters. Because ion exchange resin, used for purification of 82Sr from impurities, is also utilized to trap radioactive Sr2+ ions from radioactive waste water. After Fukushima Daiichi nuclear accident, interest in the treatment of radioactive waste water has surged. As one of main fission products of nuclear reactor, 90Sr has been regarded as a hazardous radionuclide with half-life of about 29 years. Therefore, the investigation on ion exchange resin is important for removal of 90Sr from radioactive waste water. Here, we optimized 82Sr purification method using ion exchange resin to establish the most suitable procedure.

본 연구에서는 RO(Reverse osmosis) membrane과 이온교환수지를 이용하여 방사성 이온을 제거하였다. RO필터 2개회사, 3종(1종은 세정한 폐필터)으로 요오드와 세슘을 포함하는 공급수에 대해 2bar, 4bar의 압력, 10, 50, 100ppm의 공급수 농도로 실험을 하였다. 대체적으로 고압에서 높은 제거율을 얻을 수 있었으며, 고농도에서 높은 제거율을 얻을 수 있었다. 세정한 폐필터에 대한 결과 값으로 미루어 보았을 때, 세정효과가 큰 것을 확인할 수 있었다. 이온교환수지 도 3개회사의 제품을 사용하였으며, 같은 농도하에서 수지의 양을 달리하여 제거율을 비교하였다. 비교적으로 요오드보다 세슘에 대한 제거율이 높았으며, 혼합수지에 비해 단일수지의 제거율이 높은 것을 확인 할 수 있었다.