Derivation of Weighting Factor for Dose Coefficient Based on ICRP 107 Radionuclide Data

Min Woo Kwak,Seong Yeon Lee,Hyeok Jae Kim,Kwang Pyo Kim 한국방사성폐기물학회 2023 한국방사성폐기물학회 학술논문요약집 Vol.21 No.2

When the parent radionuclide decays, the progeny radionuclide is produced. Accordingly, the dose contribution of the progeny radionuclide should be considered when assessing dose. For this purpose, European Commission (EC) and International Atomic Energy Agency (IAEA) provide weighting factors for dose coefficient. However, these weighting factors have a limitation that does not reflect the latest nuclide data. Therefore, in this study, we analyzed the EC and IAEA methodology for derivation of weighting factor and used the latest nuclide data from ICRP 107 to derive weighting factors for dose coefficient. Weighting factor calculation is carried out through 1) selection of nuclide, 2) setting of evaluation period, and 3) derivation based on ICRP 107 radionuclide data. Firstly, in order to derive the weighting factor, we need to select the radionuclides whose dose contribution should be considered. If the half-life of progeny radionuclides sufficiently short compared to the parent radionuclide to achieve radioactive equilibrium, or if the dose coefficient is greater of similar to that of the parent radionuclide and cannot be ignored, the dose contribution of the progeny radionuclide should be considered. In order not to underestimate the dose contribution of progeny radionuclides, the weighting factors for the progeny nuclides are taken as the maximum activity ratio that the respective progeny radionuclides will reach during a time span of 100 years. Finally, the weighting factor can be derived by considering the radioactivity ratio and branch fraction. In order to calculate the weighting factor, decay data such as the half-life of the radionuclide, decay chain, and branch fraction are required. In this study, radionuclide data from ICRP 107 was used. As a result of the evaluation, for most radionuclides, the weighting factors were derived similarly to the existing EC and IAEA weighting factors. However, for some nuclides, the weighting factors were significantly different from EC and IAEA. This is judged to be a difference in the half-life and branch fraction of the radionuclide. For example, in the case of 95Zr, the weighting factor for 95mNb showed a 35.8% difference between this study and previous study. For ICRP 38, when 95Zr decays, the branch fraction for 95mNb is 6.98×10-3. In contrast, for ICRP 107, the branch fraction is 1.08×10-2, a difference of 54.7%. Therefore, the weighting factor for the dose coefficient based on ICRP 107 data may differ from existing studies depending on the half-life and decay information of the nuclide. This suggests the need for a weighting factor based on the latest nuclide data. The results of this study can be used as a basis for the consideration of dose contributions for progeny radionuclides in various dose assessments.

An Investigation on the Dose Distribution of Typical Alpha-Emitting Radionuclides in Nuclear Medicine Therapy

Woo Jong-Kwan,Liu Dong,Kim Ki-Hwan,Park SoHyun 한국물리학회 2023 새물리 Vol.73 No.2

Radionuclide therapy is a targeted inner radiotherapy method that uses α-particles or other particles emitted from radionuclides to destroy target cells. In radionuclide therapy, α-emitting radionuclides can destroy target cells because of the shorter range and higher energy of emitted alpha particles compared with gamma particles of beta-emitting radionuclides. Here, in evaluating the therapeutic effects of several typical α-emitting radionuclides that might be used in radionuclide therapy, the Monte Carlo method was used. However a common cell model was designed, and then the dose distribution of α-particles emitted from selected radionuclides was calculated on the basis of various positions of radionuclides in the target cell. Calculation results show that Ac-225 can efficiently destroy the target cell when the selected radionuclides have the same position distribution and account.

A Feasibility Study on Application of Surrogate DCGL to Kori Unit 1 Decommissioning

Dong-Gyun Lee,Soon-Hwan Son,Seokyoung Ahn 한국방사성폐기물학회 2023 한국방사성폐기물학회 학술논문요약집 Vol.21 No.2

Derived Concentration Guideline Levels (DCGLs), which represent the residual radioactivity concentration limits, serve as the pivotal criteria for decontamination during decommissioning of nuclear power plants and are essential for license termination. The analysis of radionuclides in various media to check site-specific and radionuclide-specific DCGLs is a resource-intensive and time-consuming processes, and there are some radionuclides that are hard to analyze. In the decommissioning of the Rancho Seco nuclear power plant in the United States, a conservative approach was adopted. Potentially highly contaminated areas on the site were identified by collecting and analyzing soil samples, and radionuclides exceeding the Minimum Detectable Concentration (MDC) were selected as the potential Radionuclide of Concern (ROC), and surrogate DCGLs for hard-to-detect radionuclides were applied to soil samples. For soil samples in the Rancho Seco nuclear power plant, Cs-137 contributed more than 90% of the total radioactivity. DCGLs of the ROC were obtained using the scaling factors through analysis of Cs- 137 for a large amount of soil samples. In Korea, the scaling factor methodology has not been applied to the decommissioning of commercial nuclear power plants. An initial investigation was undertaken to assess the viability of implementing Surrogate Derived Concentration Guideline Levels (DCGLs) in the dismantling of Kori Unit 1, drawing insights from the U.S. nuclear power plant decommissioning experiences. To do this approach, the concentration ratio of radionuclides of interest to key radionuclide in contaminated soil should be known and consistent. But related information is not available at this time. So Surrogate DCGL for representative C-14, Fe-55, Ni-59, Ni-63, and Sr-90 was obtained using the scaling factors applied to radioactive waste data, specifically Decontaminated Aqueous Waste (DAW) and Spent Resin. In order to develop a reliable surrogate DCGLs the Kori Unit 1 site, it is important to analyze the radionuclides in the soil for the Kori Unit 1 decommissioning site to obtain consistent concentration ratio of the radionuclides of concern to the key radionuclides. When a the suitable DCGL is developed, it can be used for FSS planning and prior decision-making ensuring the safe and effective decommissioning of Kori Unit 1 and similar nuclear power plants.

Solubility of Radionuclides Under Near and Far Field Conditions: Effect of Organic Complexing Agents

Bolam Kim,Ahsan Abdul Ghani,Youngsu Lim,Dae Sung Lee 한국방사성폐기물학회 2022 한국방사성폐기물학회 학술논문요약집 Vol.20 No.2

Organic complexing agents which are contained in the radioactive waste can form the complex with radionuclides and enhance the solubility of radionuclides. The mobility of radionuclides to the far-field from the repository will be increased by radionuclide-ligand complex formation. Therefore, the assessment of the radionuclides’ solubility should be performed in the presence of organic complexing agents. In this study, five radionuclides (cobalt, strontium, iodine, cesium, and uranium) and three organic complexing agents (ethylenediaminetetraacetic acid (EDTA), nitrilotriacetic acid (NTA), and isosaccharinic acid (ISA)) were selected as model radionuclides and organic complexing agents, respectively. For simulating the in-situ condition, the groundwater near the repository was collected and applied in solubility experiments and the solubility was measured in various environmental conditions such as different pHs (7, 9, 11, and 13), temperatures (10°C, 20°C, and 40°C), and a range of organic complexing agent concentrations (10-5, 10-4, 10-3, and 10-2 M). In cases of cesium and iodine, they were very soluble in all conditions, and the effect on their solubilities was not observed. However, at high pHs, cobalt and strontium showed lower solubilities than at neutral pH and the solubility enhancement by the organic complexing agents was significant. Moreover, the effects of each organic ligand showed obvious differences and were in the order of EDTA > NTA > ISA. The solubility of uranium was increased with increasing the organic ligand concentration at lower pHs, but the organic complexing agents did not cause a remarkable difference at high pHs. According to these results, the presence of complexing agents could enhance the radionuclides’ solubility and increase the potential to release the radionuclides to the far-field from the repository. Solubility experiments of other major radionuclides in the repository are in progress.

Review of Scaling Factors and Average Radioactivity Concentration Application Methods

Jieun Park,Jungi Yeom,Hang-rae Cho,Seongjin Maeng,Wook Sohn 한국방사성폐기물학회 2023 한국방사성폐기물학회 학술논문요약집 Vol.21 No.2

To evaluate the inventory of radionuclides for the disposal of waste generated from nuclear power plants, indirect assessment methods such as the scaling factor method or average radioactivity concentration method can be applied. A scaling factor represents the average concentration ratio between key radionuclides and difficult-to-measure (DTM) radionuclides, while the average radioactivity concentration refers to the average concentration of DTM radionuclides, regardless of the concentration of key radionuclides or within specific ranges of key radionuclide concentrations. These indirect assessment methods can be statistically derived through the analysis of representative drums. This study will address how to apply these scaling factors and average radioactivity concentrations. Firstly, the concentration of gamma-emitting radionuclides will be analyzed using a drum radionuclide analyzer, and the concentration of DTM radionuclides will be determined by applying scaling factors specific to each DTM radionuclide. In the case of using the average radioactivity concentration method, the average concentration of DTM radionuclides will be applied independently of the concentration of gamma-emitting radionuclides. It is crucial to perform radioactive decay correction based on the date of generation or disposal when applying scaling factors or average radioactivity concentration. Additionally, for repackaged 320 L drums, determining which drum among the two 200 L drums inside should serve as the reference is of utmost importance

방사성폐기물 핵종분석 검증용 이상 탐지를 위한 인공지능 기반알고리즘 개발

장승수,이장희,김영수,김지석,권진형,김송현 (사)한국방사선산업학회 2023 방사선산업학회지 Vol.17 No.1

The amount of radioactive waste is expected to dramatically increase with decommissioningof nuclear power plants such as Kori-1, the first nuclear power plant in South Korea. Accuratenuclide analysis is necessary to manage the radioactive wastes safely, but research on verification ofradionuclide analysis has yet to be well established. This study aimed to develop the technology thatcan verify the results of radionuclide analysis based on artificial intelligence. In this study, we proposean anomaly detection algorithm for inspecting the analysis error of radionuclide. We used the datafrom ‘Updated Scaling Factors in Low-Level Radwaste’ (NP-5077) published by EPRI (Electric PowerResearch Institute), and resampling was performed using SMOTE (Synthetic Minority OversamplingTechnique) algorithm to augment data. 149,676 augmented data with SMOTE algorithm was used totrain the artificial neural networks (classification and anomaly detection networks). 324 NP-5077 reportdata verified the performance of networks. The anomaly detection algorithm of radionuclide analysiswas divided into two modules that detect a case where radioactive waste was incorrectly classified ordiscriminate an abnormal data such as loss of data or incorrectly written data. The classification networkwas constructed using the fully connected layer, and the anomaly detection network was composedof the encoder and decoder. The latter was operated by loading the latent vector from the end layer ofthe classification network. This study conducted exploratory data analysis (i.e., statistics, histogram, correlation, covariance, PCA, k-mean clustering, DBSCAN). As a result of analyzing the data, it iscomplicated to distinguish the type of radioactive waste because data distribution overlapped each other. In spite of these complexities, our algorithm based on deep learning can distinguish abnormal data fromnormal data. Radionuclide analysis was verified using our anomaly detection algorithm, and meaningfulresults were obtained.

Experimental Analysis and Mathematical Prediction of Radionuclides’ Solubility Using Support Vector Machine Model: Effect of Organic Complexing Agents on Radionuclides’ Solubility

Bolam Kim,Gi-Taek Oh,Youngsu Lim,Jinseob Kim,Juhui Park,Seongju Lee,Jiseon Jang,Seho Choi,Myunggoo Kang,Jaechul Ha,Chun-Hyung Cho,Min-Woo Lee,Dae Sung Lee 한국방사성폐기물학회 2023 한국방사성폐기물학회 학술논문요약집 Vol.21 No.1

The organic complexing agents such as ethylenediaminetetraacetic acid (EDTA), nitrilotriacetic acid (NTA), and isosaccharinic acid (ISA) can enhance the radionuclides’ solubility and have the potential to induce the acceleration of radionuclides’ mobility to a far-field from the radioactive waste repository. Hence, it is essential to evaluate the effect of organic complexing agents on radionuclide solubility through experimental analysis under similar conditions to those at the radioactive waste disposal site. In this study, five radionuclides (cesium, cobalt, strontium, iodine, and uranium) and three organic complexing agents (EDTA, NTA, and ISA) were selected as model substances. To simulate environmental conditions, the groundwater was collected near the repository and applied for solubility experiments. The solubility experiments were carried out under various ranges of pHs (7, 9, 11, and 13), temperatures (10°C, 20°C, and 40°C), and concentrations of organic complexing agents (0, 10-5, 10-4, 10-3, and 10-2 M). Experimental results showed that the presence of organic complexing agents significantly increased the solubility of the radionuclides. Cobalt and strontium had high solubility enhancement factors, even at low concentrations of organic complexing agents. We also developed a support vector machine (SVM) model using some of the experimental data and validated it using the rest of the solubility data. The root mean square error (RMSE) in the training and validation sets was 0.012 and 0.016, respectively. The SVM model allowed us to estimate the solubility value under untested conditions (e.g., pH 12, temperature 30°C, ISA 5×10-4 M). Therefore, our experimental solubility data and the SVM model can be used to predict radionuclide solubility and solubility enhancement by organic complexing agents under various conditions.

A Source-Related Approach for Discussion on Using Radionuclide-Contaminated Materials in Post-accident Rehabilitation

Miwa Kazuji,Iimoto Takeshi 대한방사선방어학회 2023 방사선방어학회지 Vol.48 No.2

Background : In the process of discussion on the possibility of using radionuclide-contaminated soil and debris generated by radiation disasters , a strategy for the proper management of radia- tion exposure protection while considering the source of the contaminated materials is neces- sary. JRPR Materials and Methods : The radiological protection criteria that are likely to be applied to the source-related approach based on the International Commission on Radiological Protection recommendations and the International Atomic Energy Agency safety standards are summa- rized . We proposed five interpretations of radiation protection to contribute to the promotion of discussion on the possibility of using a part of low-level-radionuclide-contaminated soil and de- bris in the post-accident rehabilitation . Interpretations I to III are based on the idea of “using a reference level to protect the public in post-accident rehabilitation ,” whereas IV and V are based on the idea of “using the dose constraint to protect the public in the post-accident rehabilitation when the sources are handled in a planned activity.” The former idea is subdivided into three based on the definition of the source , which is managed by the reference level , and the latter idea is divided into two depending on whether or not additional dose from using contaminated materials is deemed acceptable . Results and Discussion : To confirm the applicability of the five interpretations presented , we suggested the concrete values of protection criteria via two feasible cases . In this case study, we proposed radiation protection by the dose constraint based on the Interpretation IV and chose 1 mSv/yr for the public and 20 mSv/yr for workers dealing with radionuclide-contaminated ma- terials . Conclusion : We concretely and systematically demonstrated how the concept of radiation pro- tection can be applied to the process of discussion on the possibility of using radionuclide-con- taminated materials within the framework of an international system of protection . This study’s findings can provide necessary information to discuss the possibility of using radionuclide-con- taminated materials as an alternative option for recovery and reconstruction after a radiation di- saster from the viewpoint of radiation protection .

A Theoretical Approach on the Migration of a Chelating Radionuclide in Porous Medium

Baik,Min-Hoon,Lee,Kun-Jai 대한방사선 방어학회 1992 방사선방어학회지 Vol.17 No.2

이온 또는 착화된 상태의 방사성핵종의 이동에 대한 착화제의 영향을 조사하기 위하여 새로운 모델이 제시되었다. 착화된 방사성핵종의 이동거동은 착화제와 착화된 방사성핵종의 열화를 포함하는 대류-확산 이동방정식에 의해 해석되었다. 이 수학적 모델은 해석적인 방법에 의해 구해졌으며 지연요소를 조사함으로써 분석되었다. 계산결과들은 감소된 지연요소에 의해 착화된 방사성핵종의 이동속도가 이온형태의 방사성핵종보다 매우 빠름을 보여주었다. 따라서 원자력발전소로부터의 착화제의 발생과 환경으로의 유출을 감소시킬 수 있는 새로운 구제책이 필요하다고 하겠다. A new model was developed in order to investigate the effects of chelating agents on the migration of a radionuclide in the from of ion or chelate. The migration behavior of the chelated radionuclide was analyzed by formulating a convective-dispersion transport equation which included a degradation of chelating agent and chelated radionuclide. The mathematical model was analytically solved and checked with the existing retardation factor. The results show that the migration velocity of the chelated radionuclide was much faster than the ionic one due to the decreased retardation. Therefore, it was concluded that a new remedial action should be developed to reduce the generation and release of chelating agents from the nuclear power plant into the environment.

복합 핵종 방사선량률 평가 프로그램의 개발

윤선영,정운관,박병목,여화연 (사)한국방사선산업학회 2019 방사선산업학회지 Vol.13 No.4

In some cases, it may be necessary to calculate the shielding rate by predicting theradiation dose rate after the shielding due to the maintenance and modification of the shieldingarea designed for the initial license. Complex radionuclide required complex calculations in thecalculation of radiation dose rates compared to single radionuclide. In this study, we can developa radiation dose rate calculation program that is simple to operate and accessible to users insteadof expensive programs or complex calculations, and suggests appropriate radiation managementtechniques according to the results.