In the nuclear fuel cycle (NFC) facilities, the failure of Heating Ventilation and Air Conditioning (HVAC) system starts with minor component failures and can escalate to affecting the entire system, ultimately resulting in radiological consequences to workers. In the field of air-conditioning and refrigerating engineering, the fault detection and diagnosis (FDD) of HVAC systems have been studied since faults occurring in improper routine operations and poor preventive maintenance of HVAC systems result in excessive energy consumption. This paper aims to provide a systematic review of existing FDD methods for HVAC systems therefore explore its potential application in nuclear field. For this goal, typical faults and FDD methods are investigated. The commonly occurring faults of HVAC are identified through various literature including publications from International Energy Agency (IEA) and American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE). However, most literature does not explicitly addresses anomalies related to pressure, even though in nuclear facilities, abnormal pressure condition need to be carefully managed, particularly for maintaining radiological contamination differently within each zone. To build simulation model for FDD, the whole-building energy system modeling is needed because HVAC systems are major contributors to the whole building’s energy and thermal comfort, keeping the desired environment for occupants and other purposes. The whole-building energy modeling can be grouped into three categories: physics-based modeling (i.e., white-box models), hybrid modeling (i.e., grey-box models), and data-driven modeling (i.e., black-box models). To create a white-box FDD model, specialized tools such as EnergyPlus for modeling can be used. The EnergyPlus is open source program developed by US-DOE, and features heat balance calculation, enabling the dynamic simulation in transient state by heat balance calculation. The physics based modeling has the advantage of explaining clear cause-and-effect relationships between inputs and outputs based on heat and mass transfer equations, while creating accurate models requires time and effort. Creating a black-box FDD model requires a sufficient quantity and diverse types of operational data for machine learning. Since operation data for HVAC systems in existing nuclear cycle facilities are not fully available, so efforts to establish a monitoring system enabling the collection, storage, and management of sensor data indicating the status of HVAC systems and buildings should be prioritized. Once operational data are available, well-known machine learning methods such as linear regression, support vector machines, random forests, artificial neural networks, and recurrent neural networks (RNNs) can be used to classify and diagnose failures. The challenge with black-box models is the lack of access to failure data from operating facilities. To address this, one can consider developing black-box models using reference failure data provided by IEA or ASHRAE. Given the unavailability of operation data from the operating NFC facilities, there is a need for a short to medium-term plan for the development of a physics-based FDD model. Additionally, the development of a monitoring system to gather useful operation data is essential, which could serve both as a means to validate the physics-based model and as a potential foundation for building data-driven model in the long term.

This study investigated ethopabate (EPB) residues in edible tissues of broiler chickens given in drinking water and established the withdrawal time (WT) of EPB in poultry tissues. Twenty-four healthy Ross broiler chickens were orally administered with EPB at the concentration of 3.8 mg/L for 14 days (EPB-1, n=24) and 15.2 mg/L for 7 days (EPB-2, n=24) through drinking water, respectively. After the drug treatment, tissue samples were collected from six broiler chickens at 0, 1, 3, and 5 days, respectively. EPB residue concentrations in poultry tissues were determined using LC-MS/MS. Correlation coefficient values ranged from 0.9980 to 0.9998, and the limits of detection and quantification (LOQ) were 0.03~0.09 and 0.1~0.3 μg/kg, respectively. Mean recoveries in muscle, liver, kidney and skin/fat tissues were 95.9~109.8, 108.7~115.3, 89.9~96.6 and 86.7~96.8%, respectively, and coefficient of variations were less than 17.11%. At the end of the drug-administration period (0 day), EPB was detected at levels under the LOQ in all tissues from both the EPB-1 and EPB-2 groups. According to the results of EPB residue in Ross broiler tissues, withdrawal periods of both EPB-1 and EPB-2 in poultry tissues were established to 0 day. In conclusion, the developed analytical method is suitable for the detection of EPB in poultry tissues, and the estimated WT of EPB in poultry tissues will contribute to ensuring the safety of Ross broiler chickens.

From 2020, Korean Animal and Plant Quarantine Agency has reset the withdrawal time (WT) for veterinary drugs typically used in livestock in preparation for the introduction of positive list system (PLS) program in 2024. This study was conducted to reset the MRL for amprolium (APL) in broiler chickens as a part of PLS program introduction. Forty-eight healthy Ross broiler chickens were orally administered with APL at the concentration of 60 mg/L (APL-1, n=24) for 14 days and 240 mg/L (APL-2, n=24) for 7 days through drinking water, respectively. After the drug treatment, tissue samples were collected from six broiler chickens at 0, 1, 3 and 5 days, respectively. Residual APL concentrations in poultry tissues were determined using LC-MS/MS. Correlation coefficient (0.99 >), the limits quantification (LOQ, 0.3~5.0 μg/kg), recoveries (81.5~112.4%), and coefficient of variations (<15.5%) were satisfied the validation criteria of Korean Ministry of Food and Drug Safety. In APL-1, APL in all tissues except for kidney was detected less than LOQ at 3 days after drug treatment. In APL-2, APL in liver and kidney was detected more than LOQ at 5 days after treatment. According to the European Medicines Agency’s guideline on determination of withdrawal periods, withdrawal periods of APL-1 and APL-2 in poultry tissues were established to 3 and 2 days, respectively. In conclusion, the developed analytical method is sensitive and reliable for detecting APL in poultry tissues. The estimated WT of APL in poultry tissues is longer than the current WT recommendation of 2 days for APL in broiler chickens.

The 2007 Recommendation of the International Commission on Radiological Protection recommended the application of dose constraints to optimize radiation protection to resolve the inequity of exposure among radiation workers. The average annual occupational doses in Korean nuclear power plants (NPPs) are 0.3-0.8 mSv. These doses are much lower than the annual effective dose limit of 50 mSv for radiation workers stipulated by the Nuclear Safety Act. In addition, most NPP workers received less than 0.1 mSv per year. These doses are lower than the average annual occupational doses of 0.3- 0.8 mSv. Korean regulatory body conducted the study to legislate the dose constraints in the Korean regulatory system and determine dose constraints (draft) for radiation workers. The legislation of dose constraints would not greatly affect the radiation protection programs in Korean NPPs because most workers received very low doses. However, some workers received relatively higher doses than others. This study analyzed the occupational exposure conditions, such as exposure type and situation, in Korean NPPs. This study investigated the internal and external radiation doses and the radiation doses depending on the NPP operating conditions, including normal operation, planned maintenance, and intermediate maintenance, for the last ten years (2012-2021). As a result, most NPP workers received external exposure rather than internal exposure. Furthermore, most radiation exposures occurred during the planned maintenance period. The results of this study can be used for optimizing occupational doses in Korean NPPs.

The site used for a nuclear facility can be released after decommissioning if the results of dose estimation meet the regulatory requirements and the site release is approved by the regulatory body. RESRAD-ONSITE, developed by the Argonne National Laboratory, is a computer code used to estimate the dose to the residents on radiologically contaminated sites. The dose estimation for site release should consider various exposure pathways, including inhalation, ingestion, and external exposure. This study used RESRAD-ONSITE to evaluate the internal exposure dose and identify radionuclides due to the intake of food produced on radiologically contaminated sites. The upper limit of the clearance level of radionuclides expected to remain at the site was used as the source terms for the dose evaluation. In addition, the amount of food intake per capita was obtained from eight countries using nuclear power generation as of 2020. The default values of RESRAD were used for other parameters except for intake by type of food and source terms. As a result of the dose evaluation, the contaminated water and vegetables showed a great contribution to the exposure dose. The dose due to tritium in drinking water was highest in the third year. In addition, regarding the intake of vegetables, the internal exposure due to 90Sr was the highest in the first year.

As of 2023, there are a total of 24 nuclear power plants (NPPs) in operation in Korea, with 21 pressurized water reactors (PWRs) and three pressurized heavy water reactors (PHWRs). Korean NPPs discharge radioactive effluents into the environment every year. Radioactive effluents from NPPs contain various radionuclides and materials, including 3H, 14C, Noble gas, particulates, and iodine Among the radioactive effluents discharged from Korean NPPs, 14C is a pure beta emitter with a half-life of 5,730 years. The human body can inhale and ingest 14C to cause internal exposure. In addition, the amount of 14C present in the environment is decreasing, but the amount of 14C discharged from NPPs is increasing. 14C discharged to the environment can be inhaled and ingested by the public around NPPs through various pathways. For this reason, it is very important to monitor and manage 14C because it affects the dose of the public around NPPs. Therefore, this study compared and analyzed the average emissions of 14C discharged from PWRs and PHWRs during the recent 10 years (2012-2021). An average of the public dose due to 14C released from NPPs depending on the reactor types from 2012 to 2021 was also compared. It is inevitable to discharge radioactive effluents while operating NPPs. Korea Hydro & Nuclear Power (KHNP) manages and monitors radioactive effluents released into the environment. According to a survey and analysis of 14C discharged from PWRs and PHWRs and the average dose of the public over the recent 10-year (2012-2021) around Korean NPPs, 14C released from PWR accounted for 3.1% of the total discharge but accounted for more than 93.67% of the total public dose. In addition, 14C discharged from PHWRs accounted for 1.12% of the total discharge, but its resulting dose to the public accounted for more than 83.87% of the total public dose. As a result of analyzing the public dose due to 14C from 2012 to 2021, it was gradually increasing every year. Based on these results, monitoring and managing 14C discharge and its resulting doses to the public are important in the future.

After the Fukushima nuclear accident in Japan in March 2011, many Koreans were concerned that products exposed to radioactive materials released from the nuclear power plant would be imported into Korea. Systematic radiation monitoring was required for food and daily necessities imported from the nuclear accident area. The need for a legal system to support systematic radiation monitoring was also demanded. The Act on Protective Action Guidelines against Radiation in the Natural Environment was enacted to resolve concerns regarding environmental radiation in Korea in July 2011. According to this law, radiation monitoring equipment has been installed and operated at major airports and ports nationwide. This paper aims to review the radiation monitoring system of the Korean government comprehensively. The legal system and the legal basis for radiation monitoring of imported cargo conducted by each department were investigated by analyzing the laws and regulations of radiation monitoring for the relevant cargo items. In addition, the current status of radiation monitoring by the government departments was examined to determine how radiation monitoring for imported cargo is performed within the legal system. The investigation of the current radiation monitoring system for imported cargo in Korea confirmed that radiation monitoring is conducted by classifying cargo items under the jurisdiction of each government department for all imported cargo. However, the reduction in efficiency of radiation monitoring of imported cargoes, unclear legal grounds for radiation monitoring of imported cargo by some departments, the occurrence of overlapping inspections by departments, and the difficult process of issuing the radiation test certificate required for customs clearance by the Korea Customs Service were also identified. As a result of the analysis, it was found that the current radiation monitoring system for imported cargo in Korea ought to be improved, taking into account efficiency, overlapping inspection, legal background, and the difficult process of issuing the certificates.

Metal waste generated during the dismantling of a nuclear power plant can be contaminated with radionuclides. In general, the internal structure is very complex. Thus, metal waste requires various cutting processes. When metal waste is cut, aerosols are generated. Aerosols are generally various particles of very small size suspended in the working area and remain for a considerable period. This may cause internal exposure of workers due to inhalation of radioactive aerosols generated when cutting radioactive metal waste. This study investigated various cutting processes and the size distribution of aerosols generated during the cutting process. The cutting process is normally classified into thermal cutting, mechanical cutting, and laser cutting. Thermal cutting includes plasma, flame, and oxygen cutting. Mechanical cutting includes mechanical saws, cutters, nibblers, and abrasive water jets. Stainless steel, carbon steel, aluminum, and copper are commonly used as cutting materials in nuclear power plants. The size of the aerosol generated from cutting showed a very diverse distribution depending on the cutting methods and cutting materials. In general, aerosol size is distributed within 0.1-1 μm. This size distribution is different from the 5 μm aerosol size suggested by the ICRP Publication 66 Lung model. These results show that it is necessary to conduct further studies on the size of aerosols generated when decommissioning nuclear power plants.

Currently, there are 25 nuclear power plants (NPPs) in operation in Korea, including 22 pressurized water reactors (PWRs) and three pressurized heavy water reactors (PHWRs). Two NPPs, including Kori Unit 1 and Wolsong Unit 1, are permanently shut down and awaiting decommissioning. If Kori Unit 2, which is expected to be permanently shut down soon, is included, the number of decommissioning NPPs will be increased to three. Spent fuels (SFs) are continuously generated during the NPP operation, which are stored in an SF storage pool in NPPs to cool down the decay heat emitted from SFs. For safe NPP operation, SFs must be regarded as waste, and a disposal site must be selected to isolate SFs. However, an appropriate site has yet to be selected in Korea. SFs contain long-lived nuclides with a high specific activity. For disposal, it is important to characterize the nuclides in the fuels and delay the migration of the nuclides to the environment when SFs are placed in a future disposal facility. If the disposal container is broken, the nuclides in the fuels escape from the filling material, such as bentonite. These escaped nuclides are dissolved in groundwater and migrate to the surface of the earth. Thus, it is possible to assess the radiological impact, such as the exposure dose during and after the disposal, if the types and characteristics of nuclides in SFs are known. This study investigated the nuclides in SFs and identified exposure scenarios that may occur in the disposal process of SFs and migration characteristics when the nuclides leak into groundwater to propose a dose assessment methodology for workers and the public.

The domestic representative nuclear fuel cycle facilities are post-irradiation examination facility (PIEF) and Irradiated Examination Facility (IMEF) at KAERI. They have regularly operated since 1991 and 1993, respectively. Due to the long period of use, the facilities are ageing, and maintenance costs are increasing every year. The maintenance methods have mainly been breakdown maintenance (BM) and partially preventive maintenance (PM). They involve replacing components that have problems through periodic inspections by on-site inspectors. However, these methods are not only uncertain in terms of replacement cycles due to worker’s deviation on the inspection results, but also make it difficult to respond accidents developed through failures on the critical equipment that confines radioactive material. Therefore, an advanced operation and maintenance studied in 2022 through all of nuclear facilities operated at KAERI. Advancement strategy in four categories (safety, sustainability, performance, innovativeness) was analyzed and their priorities according to a facility environment were determined so a roadmap for advanced operation and maintenance could be developed. The safety and sustainability are higher importance than the performance and innovativeness because facilities at KAERI has an emphasis on research and development rather than industrial production. Thus, strategy for advancement has focused even more on strengthening the safety and sustainability. To enhance safety, it has been identified that immediate improvement of aged structures, systems, and components (SSCs) through large-scale replacement is necessary, while consideration of implementing an ageing management program (AMP) in the medium to long term is also required. Facility sustainability requires strengthening operation expertise through training, education, and cultivation of specialized personnel for each system, and addressing outstanding regulatory issues such as approval of radiation environment report on the nuclear fuel processing facilities and improvement work according to fire hazard analysis. One of the safety enhancement methods, AMP, is a new maintenance approach that has not been previously applied, so it had to be thoroughly examined. In this study, an analysis was conducted on the procedure and method for introducing an AMP. An AMP for nuclear fuel cycle facilities was developed by analyzing the AMP applied to the BR2 research reactor in Belgium and modifying it for application to nuclear fuel cycle facilities. The ageing management for BR2 has the objective to maintain safety, availability and cost efficiency and three-step process. The first step is the classification of SSCs into four classes to apply graded approach. Secondly, ageing risk is assessed to identify critical failure modes, their frequency and precursors. Final step involves defining measures to reduce the ageing risk to an acceptable level in order to integrate the physical and economic aspects of ageing into a strategy for inspection, repair, and replacement. Similar approach was applied to the nuclear fuel cycle facility. Firstly, the SSCs of nuclear fuel cycle facilities have been classified according to their safety and quality classifications, as well as whether they are part of the confinement boundary. The SSCs involved in the confinement boundary were given more weight in the classification process, even if they are not classified as safety-class. A risk index for ageing was introduced to determine which prevention and mitigation measure should be chosen. By multiplying the health index and the impact index, the ageing risk matrix provides a numerical score that represents guidance on the prevention and mitigation of ageing effect. The health index is determined by combining the likelihood of failure and engineering evaluation of the current condition of SSCs, whereas the impact index is calculated by taking into account the severity of consequences and the duration of downtime resulting from a failure. This ageing management has to be thoroughly reviewed and modified to suit each facility before being applied to nuclear fuel cycle facilities.

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.

Colorectal cancer causes the most cancer-associated death worldwide, having a high cancer incidence. Pectin is a complex polysaccharide present in various fruits, emerging as an anti-carcinogenic candidate. Although pectin has a suppressive capacity for colon carcinogenesis, the effect of reactive oxygen species (ROS) generation and colonic aberrant foci formation in the colon carcinogenesis mouse model remains unclear. Therefore, this study investigates the regulatory effect of pectin supplementation on colon carcinogenesis induced by azoxymethane (AOM) and dextran sodium sulfate (DSS) in mice. In an animal experiment, thirty male institute for cancer research (ICR) mice were divided into two experimental groups; AOM/DSS (control group) and AOM/DSS + pectin (5% in drinking water). Furthermore, the number of aberrant crypt foci (ACF) and aberrant crypt (AC) on colonic mucosa were counted, and thiobarbituric acid-reactive substances (TBARS) assay was performed to estimate lipid peroxidation in feces. Pectin treatment significantly decreased the number of ACF and AC per colon compared with the control. Additionally, fecal TBARS level in the pectin group was significantly lower than those in the control group. Conclusively, these findings indicate that pectin-inhibited hyperplastic alteration and oxidative stress suppress colitis-associated colon carcinogenesis.

Colon cancer has been considered a leading cause of cancer-associated death. Folic acid is a vitamin necessary for cellular physiological functions and cell viability. However, the association between folic acid intake and colon cancer has been examined in several prospective cohort studies are controversial. This study investigated the effects of folate intake on colon carcinogenesis and oxidative stress in an azoxymethane (AOM)/dextran sodium sulfate (DSS) institute for cancer research (ICR) mouse model. Thirty male ICR mice (5 weeks old) were divided into the control group and the experimental group supplied 0.03% folic acid via drinking water (50 mL/week/mouse) for 6 weeks. To induce colonic pre-neoplastic lesions, the animals were subcutaneously injected three times weekly with AOM (10 mg/kg body weight), followed by 2% DSS in drinking water for a week. Folic acid supplementation significantly suppressed the total number of aberrant crypt foci and aberrant crypts. Histological image data showed that folic acid supplementation attenuated neoplastic change. In addition, we measured the thiobarbituric acid reactive substances concentration of dry feces samples to identify the effect of folic acid on reactive oxygen accumulation. The folic acid supplementation group had reduced reactive oxygen species levels in dry feces compared to the control group. In conclusion, these findings indicate that folic acid suppresses colon carcinogenesis and oxidative stress in an AOM/DSS mouse model.

Colon cancer is known as the third most widespread cancer in the world. The interaction of heme-iron and ascorbic acid (AA) in colon carcinogenesis is not evident. Hemin (ferric chloride heme) is an iron-containing porphyrin with chlorine that can be formed from a heme group. The purpose of this study was to investigate the protective effect of AA on the formation of pre-neoplastic lesions induced by azoxymethane (AOM)/dextran sodium sulfate (DSS) plus hemin in mice. Forty-five ICR male mice were divided into three experimental groups; AOM/ DSS treatment (control group), hemin (2 g hemin/kg of b.w.), hemin + AA (1.0% in drinking water). The mice had three s.c. injections (0–2nd weeks of the experiment) of AOM (10 mg/kg b.w.) weekly and 2% DSS as drinking water for the next one week and the animals fed on AIN-76A purified rodent diet for 6 weeks. The numbers of aberrant crypt foci (ACF) and aberrant crypts (ACs) in colonic mucosa were counted after methylene blue staining. Lipid peroxidation in feces was measured by the thiobarbituric acid-reactive substances (TBARS) assay. The numbers of ACF and ACs per colon significantly increased in Hemin group compared to the control group. However, the numbers of ACF and ACs per colon notably decreased in hemin + AA group compared to the control group or hemin group (p<0.05). In feces, the TBARS value of hemin group was higher than the control group (p<0.01). The TBARS value of hemin + AA group was slightly decreased compared to Hemin group. These results indicate that hemin can promote the experimental colon carcinogenesis in ICR mice. On the other hand, additional supplement of AA via drinking water has a protective effect against the colon carcinogenesis. The related mechanisms need to be illustrated by further studies in future.

Globally, colon cancer is increased gradually and known as one of the major causes of cancer death. Stevia, a substitute of sugar, is known to have many components including alpha-tocopherol and anthocyanin etc, as antioxidants. This study's purpose is to investigate whether stevia plant extract can have a protective effect against colon carcinogenesis induced by azoxymethane (AOM) and dextran sodium sulfate (DSS) in mice. Total 30 male ICR mice were divided into 2 groups; AOM/DSS treatment (control group), AOM/DSS + stevia extract (0.5%, in drinking water). After acclimation for 1 week, five weeks old mice received three intraperitoneal AOM (10 mg/kg b.w.) injections weekly for 3 weeks (0–2nd weeks of the experiment) and 2% DSS as drinking water for the next one week. AIN-76A purified rodent diet and 0.5% stevia extract water were supplied to the animals for 6 weeks. The colons of mice were collected and the number of aberrant crypt foci (ACF) and aberrant crypts (ACs) in colonic mucosa were counted after staining with methylene blue. Malondialdehyde (MDA) concentration in feces were determined. The numbers of ACF and ACs were significantly (p<0.01) decreased in stevia-treated group compared with the control group. The MDA concentration in feces was also significantly (p<0.01) decreased in stevia-treated group compared with the control group. In histopathology of colonic epithelium, hyperplasia of colonic epithelium was less observed in steviatreated group. These results indicate that stevia has a protective effect against colon carcinogenesis induced by AOM/DSS in mice and further study needs to illustrate the protective mechanisms.