Since the level 2 PSA of OPR-1000 was the requirement for regulatory purposes, Cs-137 release estimation was contained as the Nuclear Safety Act of ROK in which the Cs-137 release frequency exceeding ...100 TBq was determined to happen less than 1.0E-6 per year after the Fukushima Daiichi Accident. However, Cs-137 release estimation from the conventional level 2 PSA of OPR-1000 provided uncertainty due to dominant accident sequence consideration. Thus, this study aimed to develop systematic methods through the overall framework to quantify realistic uncertainty concerns of radioactive material release using sensitivity and uncertainty analysis methods and apply them to OPR-1000. This framework helped to quantify confidential value for the Cs-137 release under the BEPU approach using both parametric and non-parametric methods to cover both realistic and conservative points. Uncertainty propagation analysis showed the unexpected uncertainty increase of Cs-137 release exceeding 100 TBq. The non-parametric uncertainty analysis provided higher conservative concerns for safety than the realistic concerns in terms of economics when compared with the parametric uncertainty analysis. Wilks’ uncertainty analysis showed the importance to consider conservative Cs-137 release in order to reach the higher safety need. Sensitivity analysis showed reasonable relationships between engineering safety parameters with the Cs-137 release.
•Uncertainty framework affects more Cs-137 releases than 10 times of 100 TBq•Realistic Cs-137 release is dominant in uncertainty parametric schemes•Conservative Cs-137 release in high Wilks' orders matches the safety need•Engineering safety parameters in sensitivity analysis highly affect Cs-137 release
Due to Thailand's nuclear energy public acceptance problem, the understanding of nuclear energy public perception was the key factor affecting to re-consideration of the nuclear energy program. ...Thailand Institute of Nuclear Technology and its alliances together developed the classification model for the nuclear energy public perception from the big data comments on social media using Facebook using deep transfer learning. The objective was to insight into the Thailand nuclear energy public perception on Facebook social media platform using sentiment analysis. The supervised learning was used to generate up-to-date classification model with more than 80% accuracy to classify the public perception on nuclear power plant news on Facebook from 2009 to 2022. The majority of neutral sentiments (80%) represented the opportunity for Thailand to convince people to receive a better nuclear perception. Negative sentiments (14%) showed support for other alternative energies due to nuclear accident concerns while positive sentiments (6%) expressed support for innovative nuclear technologies.
Evaluation of aerosol deposition in the containment vessel is an important step for the assessment of radioactive material release to the environment. ART Mod 2 is a calculation code that is used for ...evaluation of aerosol deposition in the containment vessel. The authors modified aerosol deposition models of ART Mod 2, namely, gravitational settling model, Brownian diffusion model, diffusiophoresis model, and thermophoresis model in order to increase potential of capturing the deposition phenomena. This study aims to compare the simulated results of modified ART Mod 2 with aerosol deposition of cesium compounds in the containment vessel of Phébus FPT3 experiment, in order to validate modified ART Mod 2 code. It is found that aerosol deposition using modified ART Mod 2 agrees with Phébus FPT3. Prediction of Brownian diffusion is significantly improved due to the consideration of turbulent damping process. Cesium mass flow rate and aerosol size are factors that can significantly influence the uncertainty of the results. When conditions of single volumes are carefully selected to match those of the Phébus FPT3 experiment, modified ART Mod 2 can predict aerosol deposition in Phébus FPT3 with relative accuracy.
•A framework to consider long-term evolution of nuclear accident consequences is proposed.•Monetization is a good way to capture various consequences to people & environment.•Decontamination ...dominates the overall accident consequence in the initial stage.•Radiation effects dominate the overall accident consequence in the late stage.
Recent studies on nuclear accident consequence assessments that can cover consequences to both people and the environment, cannot capture the change of consequences over time, and vice versa. This study aims to design a framework of nuclear accident consequence assessment that can cover major consequences to people and the environment, and capture the long-term evolution of those consequences. Major long-term accident consequences are quantified using the cost per severe accident. Annual changes of key parameters are monitored to capture the change of each consequence over time. A case study with a hypothetical long-term loss of all AC power in a virtual BWR near Bangkok is conducted. Monitoring of the change of consequences over time leads to a different picture of overall accident consequences. Though decontamination takes up a large share of the cost per severe accident, its effects significantly decrease in several years. Radiation effects then dominate the overall accident consequences from the second decade onward. Parameter survey reveals the effectiveness of limiting and delaying decontamination in reducing the overall accident consequences in initial stage (first two years) and later stage (up to a decade), respectively. This time-dependent nuclear accident consequence assessment framework will be useful for long-term nuclear accident aftermath management planning.
Global radionuclide dispersion from Fukushima nuclear accident urged several countries to begin evaluating the radiation effects from neighboring countries. The representative data selection ...simulation is one of the evaluation methods providing practical results with reasonable computational resources. However, it is mostly used in the domestic radiation effect evaluation. This study investigated and modified this simulation method for transboundary radiation effect evaluation. The effects of selected area boundaries, optional weather parameters, and sampling rate, critical parameters in the representative data selection scheme, are sequentially investigated on the calculated results. The evaluation is performed by Nuclear Accident Consequence Analysis Code (NACAC) with hypothetical accidents at Fangchenggang NPP in China. It is revealed that area boundary and optional weather parameter selection insignificantly impact the predicted results, but the sampling rate condition affects the predicted results. Good agreements comprising dispersion characteristics and total effective dose equivalent by simulation using representative and sequential data selections are shown with absolute mean bias error lower than 2.4 × 10
−3
mSv, root mean square error lower than 5.7 × 10
−4
mSv, and correlation coefficient value higher than 9.1 × 10
−1
.
Due to Thailand's nuclear energy public acceptance problem, the understanding of nuclear energy public perception was the key factor affecting to re-consideration of the nuclear energy program. ...Thailand Institute of Nuclear Technology and its alliances together developed the classification model for the nuclear energy public perception from the big data comments on social media using Facebook using deep transfer learning. The objective was to insight into the Thailand nuclear energy public perception on Facebook social media platform using sentiment analysis. The supervised learning was used to generate up-to-date classification model with more than 80% accuracy to classify the public perception on nuclear power plant news on Facebook from 2009 to 2022. The majority of neutral sentiments (80%) represented the opportunity for Thailand to convince people to receive a better nuclear perception. Negative sentiments (14%) showed support for other alternative energies due to nuclear accident concerns while positive sentiments (6%) expressed support for innovative nuclear technologies.
Human reliability analysis (HRA) of nuclear research reactors often encounters a lack of human performance data, a challenge that is also faced by the TRIGA reactor of Thailand having no specific ...full method or human error database for HRA. To overcome this challenge, in 2023, HRA teams from the Korea Atomic Energy Research Institute (KAERI) and the Thailand Institute of Nuclear Technology (TINT) jointly developed an HRA framework for the TRIGA reactor. In the HRA framework development, the HRA practitioners applied KAERI's three main HRA tools, namely 1) the EMpirical data-Based crew Reliability Assessment and Cognitive Error analysis (EMBRACE) method, 2) the Human Reliability data EXtraction (HuREX) database, and 3) the TAsk COMplexity (TACOM) method. The HRA framework covers the overall process including the classification of documents and human error types as well as nominal human error extraction for estimating nominal human error probabilities. According to the results of the first use of the HRA framework on the TRIGA reactor in Thailand, the HRA framework provided an effective way to improve the procedures and systematically identify nominal human errors of actions in the emergency procedures.
•HRA framework is developed for TRIGA reactor having limited HRA data and experience.•NPP HRA tools help enhance the standard of the TRIGA HRA framework as in NPPs.•HRA framework suggests how to extract nominal human errors from emergency procedures.•HRA of TRIGA reactor supports systematic procedure improvement in NHEP estimation.
The pilot Probabilistic Safety Assessment (PSA) of Thai Research Reactor-1/Modification 1 (TRR-1/M1) was implemented to fulfill the new Thai Ministrial Regulation on Periodic Safety Review (PSR). The ...paper's objective is to conduct the level 1 PSA of TRR-1/M1 for internal events and human errors. Considering the graded approach, Hazard and Operability (HAZOP) and Human-Hazard and Operability (Human-HAZOP) analyses which require moderate details were selected to assess hazardous events and eventually determine Initiating Events (IEs). Fault Tree Analysis (FTA), Event Tree Analysis (ETA), and Bayesian updating were used to calculate Core Damage Frequencies (CDFs). The assessment showed that HAZOP analysis is suitable for an uncomplicated research reactor like TRR-1/M1 since it does not require lengthy calculation time and detailed failure data. Human-HAZOP analysis revealed inherent-operational errors that were ignored in TRR-1/M1, especially the situation that valves V-3 and V-4 were kept open in order to quicken reactor startup operation. IE1: Loss of Coolant Accident (LOCA), IE2: Insertion of excess reactivity, and IE3: Failure of equipment in fuel handling process were identified as the main IEs. The largest CDF of IE3 (4.36E-02 1/yr) implies that it is the main risk issue of TRR-1/M1 to which operators should pay more attention during the operation.
•A simple HAZOP analysis can sufficiently assess the risks in a research reactor.•The human-HAZOP analysis reveals inherent-operational errors previously ignored.•Failure of equipment in fuel handling process gives largest core damage frequency.•Bayesian updating justifies the usage of generic data in a pilot PSA of a TRIGA reactor.
Calculating atmospheric dispersion in a hypothetical nuclear accident plays an essential role as a predictive tool in nuclear emergency planning. The Nuclear Accident Consequence Analysis Code ...(NACAC) has been developed as an in-house code by the Thailand Institute of Nuclear Technology to develop its capability for understanding the transboundary radiological effect of a hypothetical nuclear accident. To verify the performance of the NACAC, a comparison between the calculated results using the NACAC with those from the well-developed Java-based Real-time On-line Decision Support (JRODOS) code is performed with representative cases of all seasons in a year. Two hypothetical severe accidents at the Fangchenggang pressurized water reactor, namely, (i) a loss of off-site power and (ii) a large-break loss of coolant, are utilized as the initial boundary conditions. The air concentration characteristic maps obtained from both codes are analyzed, revealing that the dominant radionuclide dispersion pathways are similar in all study cases. The air concentration, ground concentration, and total effective dose rate at several locations up to 500 km away from the release point are directly compared. Typically, the calculated results from the two codes are in reasonable agreement. However, for specific locations and directions, the NACAC predictions of the concentrations and total effective dose rate are lower than those from the JRODOS. These differences may be influenced by the different trajectory calculations between the two codes, which resulted in varying plume densities in certain areas. However, it does not significantly affect the radiation effect assessment. The NACAC still provides a total effective dose rate corresponding to the JRODOS, lower than one mSv throughout the main dispersion direction.
•Differences in the calculation process of NACAC and JRODOS codes were investigated.•Influences of the data preparation system on simulated results were examined.•The effects of different advection calculations on simulated results were clarified.•An agreement of calculated results by NACAC and JRODOS codes was found.
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