Nghiên cứu và ứng dụng chương trình FLEXPART trong đánh giá phát tán phóng xạ tầm xa tt tiếng anh

MINISTRY OF EDUCATION AND TRAINING MINISTRY OF SCIENCE AND TECHNOLOGY VIETNAM ATOMIC ENERGY INSTITUTE PHAM KIM LONG RESEARCH AND APPLICATION OF FLEXPART IN THE LONG-RANGE ATMOSPHERIC DISPERSION OF RADIONUCLIDES Major: Nuclear and Atomic Physics Code: 9.44.01.06 SUMMARY OF DOCTORAL DISSERTATION OF PHYSICS Hanoi - 2019 The thesis has been completed at: Nuclear Training Center, Vietnam Atomic Energy Institute 140 Nguyen Tuan, Thanh Xuan, Hanoi Supervisors: Prof Dr PHAM Duy Hien Vietnam Atomic Energy Institute Dr NGUYEN Hao Quang Vietnam Atomic Energy Institute Referee 1: Prof Dr LE Hong Khiem Institute of Physics, Vietnam Academy of Science and Technology Referee 2: Assoc Prof Dr NGUYEN Tuan Khai Vietnam Agency for Radiation and Nuclear Safety The dissertation has been defended against the Institute-level Doctoral Dissertation Defense of Nuclear Training Center, Vietnam Atomic Energy Institute At 14:00 on March 4, 2019 The thesis can be found at: - National Library of Vietnam - Library of Nuclear Training Center OVERVIEW The reason for choosing the thesis topic Lessons learnt from the Chernobyl disaster in 1986 or the Fukushima nuclear accident in 2011 show the importance of environmental radioactivity monitoring, simulation, calculation and evaluation of atmospheric dispersion of radionuclides from nuclear power plants (NPP) in supporting the emergency preparedness in response to nuclear reactor accidents Among the NPPs near our country, the Fangchenggang NPP is located near the border of our country less than 50 km, about 250 km away from Hanoi capital We need to build an Environmental Radiation Warning and Monitoring Network to continuously monitor artificial and natural radiation levels, combined with simulation of atmospheric dispersion of radionuclides in supporting the emergency preparedness Due to these urgent requirements, I chose the thesis topic “Research and application of FLEXPART in the long-range atmospheric dispersion of radionuclides” with my desire to contribute a small part in the field of monitoring, warning and responding to environmental radiation incidents The aim of this thesis is to provide a suitable model for evaluation of the long-range atmospheric dispersion of radionuclides in supporting the emergency preparedness Purpose of this study To learn mathematical models and simulation programs suitable for long-range dispersion of radioactivity To learn meteorological models that meet the requirements of simulation programs and meteorological data analysis tools To validate of the atmospheric dispersion model through the Fukushima nuclear power plant accident To apply of the model for assessing the impart of atmospheric transport of radioactivity from China's nuclear power plants Research scope, research objective and research methods The Lagrangian particle dispersion model FLEXPART FLEXPART meteorological input data: Climate Forecast System version (CFSv2), Global Forecast System (GFS) Panoply software for meteorological data analysis High Performance Computing (PARAM-HUST) to run the simulation using FLEXPART Statistical evaluation methods to verify compatibility between simulation and observation Atmospheric transport of 131I and 137Cs from Fukushima accident to tropical western Pacific (TWP) and Southeast Asia (SEA) Application of FLEXPART for assessing the impart of atmospheric transport of radioactivity from Fangchenggang nuclear power plant Significance of the Study The thesis has studied the possibility of applying the dispersion model used in FLEXPART to simulate the transport of radioactivity into the atmosphere Activity concentrations of radionuclides measured at ten monitoring stations in TWP and SEA from Fukushima accident were used to validate the particle dispersion model Good agreement between the FLEXPART model and observations yields confidence regarding its application to assess radiation impacts and support emergency planning in response to a possible future nuclear accident in the region The layout of the thesis The thesis consists of 100 pages of content, 18 tables, 57 figures, 03 published works (02 articles and 01 national nuclear conference), 79 references, annexes, to be allocated as follows: Overview: Introducing the reasons for choosing the thesis topic, purpose, objective, scope and methods of research, significance of the thesis (4 pages); Chapter 1: Overview of nuclear power plants in East Asia, atmospheric dispersion model and meteorological characteristics (30 pages); Chapter 2: Evaluation methods in atmospheric dispersion of radionuclides using FLEXPART (37 pages); Chapter 3: Results and Discussion (25 pages); Conclusion and recommendations for future research (3 pages); Finally, the list of publications related to the thesis, references, and annexes CHAPTER INTRODUCTION Vietnam is located in Southeast Asia adjacent to East Asia, There are currently countries and territories with commercially operating nuclear power plants, including: China, Taiwan, Japan and South Korea (Fig 1.1) A total of 48 commercially operating nuclear power plants with 157 nuclear reactors [1], of which 116 units are in operation, 20 units are under construction, 21 units have been deactivated, and many units are in construction plans Fig 1.1 Map of the nuclear power plants in East Asia 157 units of NPPs in East Asia connected the first time to the grid by year as shown in Fig 1.2 The technology and age of the reactors are calculated at the end of 2018 in this area as shown in Fig 1.3 and 1.4 [1] Fig 1.2 Number of units connected to the grid by year in East Asia Fig 1.3 Nuclear power technology in East Asia Fig 1.4 The age of reactor types of operating NPPs in East Asia Within a distance of 1000 km from our country border, 18 units are operating and units are under construction belong to China [1] The units include generations of II, II +, III and III + reactors In particular, the Fangchenggang NPP is located in Quangxi, China With a distance less than 50 km from our country border, about 250 km away from Hanoi capital (Fig 1.5) A total of six reactors are planned to operate at Fangchenggang NPP (2 units are in operation, units are under construction, and units are in the construction plan) [2] Fig 1.5 Satellite image of Fangchenggang NPP (Source: Google Earth, updated on May 10, 2016) In fact in East Asia, the accident happened at Fukushima NPP in March 2011 [4] A huge amount of radioactive material was released into the atmosphere and dispersed across the northern hemisphere Japan raised the disaster at Fukushima Daiichi to Level on the INES scale [10] As we all know when the nuclear accident occurs, an inevitable byproduct of nuclear fission is the production of fission products which are highly radioactive released into the environment, especially the atmosphere Radioactive isotopes are very useful in environmental research to assess the extent of accidents affecting the environment and people In such an urgent situation, we need to build an Environmental Radiation Warning and Monitoring Network to continuously monitor artificial and natural radiation levels, combined with simulation of atmospheric dispersion of radionuclides in supporting the emergency preparedness in response to nuclear reactor accidents We use the Lagrangian particle dispersion model FLEXPART (Stohl et al., 1998, 2005) to simulate atmospheric transport of radionuclides from nuclear power plants FLEXPART can be used for calculating the long-range and mesoscale dispersion of air pollutants including dry deposition, wet deposition, radioactive decay from a point source, line source, or area sources FLEXPART is a Lagrangian transport and dispersion model, compared with Gaussian and Eulerian models, this is a model that is widely used in simulation to evaluate the dispersion of pollutants into the atmosphere In addition, large-scale atmospheric circulation features of atmospheric circulation are also being studied in order to better explain the atmospheric dispersion of radioactivity CHAPTER RESULTS AND DISCUSSION 3.1 Atmospheric transport of radionuclides from Fukushima to Southeast Asia 3.1.2 Design in simulation of radionuclides dispersed from Fukushima to TWP and SEA In this work, we use the Lagrangian particle dispersion model FLEXPART (Stohl et al., 1998, 2005) combined with the meteorological data provided by NCEP (with a spatial resolution of 0.5°) (Saha et al., 2014), to simulate atmospheric transport of 131 I 137 Cs from FNPP to TWP and SEA The results are evaluated with observational data from the region We assess the contribution of the northeast monsoon and its associated meteorological conditions to regional transport of Fukushima-derived radionuclides because this could inform the potential impacts of radiological emissions from other NPPs in northeast Asia (NEA) For the emission scenarios of 131I and 137Cs, source terms from Katata et al (2015) were adapted for this simulation (Fig 3.2) There were two sets of particle median diameter (d p) and particle density (ρp), namely, dp = 0.6 μm, ρp = 2500 kg/m3 (Arnold et al., 2015; Geng et al., 2017) in the simulation I, and d p = 0.4 μm, ρp = 2500 kg/m3 in the simulation II The simulations were designed to run on the PARAM-HUST supercomputer 11 Fig 3.1 The locations of radiation monitoring stations operating during the FNPP accident in TWP and SEA (red points) The FNPP is marked with a star in yellow Fig 3.2 The emission rates of 131I and 137Cs during the FNPP accident according to Katata et al (2015) 12 Table 3.1 FNPP-derived 131I observed at monitoring stations in TWP and SEA Station Fukuoka Okinawa Nankang Guam Hong Kong Manila Hanoi Dalat HCMC KL 3.1.2 Atmospheric transport of radioactive material from Fukushima to TWP and SEA The meteorological conditions during the FNPP accident (e.g., mean sea level pressure, wind speed and wind direction) in East Asia are shown in Fig 3.4 The modeled FNPP radioactive plumes are shown in Fig 3.6a–d and 3.10a-d in terms of mean activity 13 concentrations in the atmospheric columns from to km and 2–10 km These represent the planetary boundary and troposphere layers, respectively Fig 3.4 The meteorological conditions (mean sea level pressure (Pa), wind speed (m/s) and wind direction) driven the first regional plumes on March 18 and the second regional plume on April 3.1.2.1 Hermispherical transport After the first release of radioactivity at FNPP on March 12, the radioactive cloud was transported towards the Pacific Ocean, where it was captured by the extra-tropical low-pressure system located over the Bering Sea (the Aleutian Low) The plume was lifted up to the troposphere and then rapidly transported northeastward via the jet stream (Fig 3.9 and 3.10) Cyclonic and frontal systems following the jet stream led to vertical mixing resulting in surface detection of radionuclides across the northern hemisphere (Mészáros et al., 2016) The hemispherical plume progressively arrived from North America (16–18/3) to the north Atlantic (19/3), Scandinavia (22/3), western Russia (23/3), NEA and then the western Pacific (30–31/3) (Fig 3.9) 14 Fig 3.9 Mean airborne concentration (in Bq/m3) of 131I in the 0–20 km layer 3.1.2.2 Regional transport The first FNPP regional plume was transported towards TWP and SEA on March 18th when the south-eastward moving Siberian anticyclone appeared over southern Japan (Fig 3.9a), forcing the radioactive cloud in a clockwise direction, then traveled southwestward by the northeast monsoon (Fig 3.4a) The modeled plume arrived in Guam, Philippines, Okinawa, Taiwan, and northern Vietnam on March 20, 22, 24, 25, and 27, respectively (Fig 3.9b) The strong release of radioactivity on March 23 (Fig 3.9) and the anticyclone coming back over southern Japan on March 26 (Fig 3.4) transported this plume further into the equatorial western Pacific (Fig 3.9c), landing on southern Vietnam and Malaysia from March 28–29 15 The second regional plume departed from Japan on approximately April 4, when two eastward moving anticyclones occurred over the western Pacific with one approaching Japan and the other further east (Fig 3.4b) The FNPP radioactive plume was blocked from tropospheric transport for several days by the eastern anticyclone, while the anticyclone approaching Japan forced the plume to move in a southwest direction and subsequently traveled under the influence of the northeast monsoon The radioactive air mass traveled almost entirely within the marine boundary layer (Fig 3.9d) and was not observed at higher altitudes (Fig 3.10d) Fig 3.11 131I and 137Cs peak activity concentrations as a function of distance from Fukushima (km) during the second regional plume The peak activity concentration associated with the arrival of the second regional plume decreased exponentially with distance from FNPP and had decreased by half after a distance of 577 km for 131 I and 433 km for of 137 137 Cs, as shown in Fig 3.11 The faster decrease Cs peak activity concentrations with distance indicates greater deposition loss of 137Cs relative to due to its greater particle size 131 16 I during atmospheric transport 3.1.3 Comparison between modeled and observed surface activity concentrations 131I Figs 3.12 and 3.13 compare the measured and modeled and 137Cs activity concentrations, respectively, at nine monitoring stations located in TWP and SEA The Hong Kong station is removed due to lack of 137Cs measurement data (Lee et al., 2012) The arrival times of the plumes and the dates of peak activity concentrations were predicted rather well, within an error of ± days The correlation coefficients were statistically significant for most monitoring stations (Table 3.1) The results show good agreement between the observed andmodeled concentrations in the simulation I for 137 Cs (dp = 0.6 μm) and in the simulation II for 131 (dp = 0.4 μm) Fig 3.12 Time series of observed (blue column) and simulated 131I surface activity concentration in the simulation I (red line) and simulation II (green line) 17 I 3.1.5 New findings of this study Our research was published in December 2018 as “Atmospheric transport of 131I and 137Cs from Fukushima by the East Asian northeast monsoon” [79] We found that in addition to the hemispherical plume, there were also regional plumes The regional transport was more important in contributing Fukushimaderived radioactivity to the regions The radioactivity of the hemispherical plume became depleted after a 20-day journey circumnavigating the northern hemisphere before reaching TWP The FNPP radioactive level recorded in TWP and SEA would have been much greater if the accident occurred at the same time as those meteorological conditions that generate regional southwestward plumes (i.e on March 18 or April instead of March 12) 3.2 Application of FLEXPART to assess the imparts of atmospheric transport of radioactivity from China‘s Fangchenggang nulear power plant to Vietnam The northeast monsoon (NEAM) dominates the weather and climate of Vietnam in winter, it also brings to our country air pollutants, including radioactive plumes on the windy road when a nuclear power accident occurs There are 3-5 monsoon winds due to disputes and conflicts between continental cold air (Siberian high pressure) and Pacific hot air (low pressure) Therefore, the southeast monsoon winds blows not only in the northeast direction but also in the southeast at the end of the phase and intermediate directions This makes it difficult to guess the direction of the radiation plumes The thesis only initially mentioned some typical scenarios in January 18 2018 when the Siberian was most active high pressure is the highest level pressure The atmospheric dispersion of radionuclides released from China’s Fangchenggang NPP to Vietnam was simulated by using the Lagrangian particle dispersion model FLEXPART with the meteorological data CFSv2 [5] The input parameters for particle size, dry deposition, wet deposition through the Fukushima study (Long et al., 2019) were used for this simulation with level of the INES scale Atmospheric dispersion of radionuclides was simulated from January 01 to 31, 2018 At this time, there are two main northeast monsoon winds coming to Vietnam The cold front began to appear above Fangchenggang NPP on January and 28 and then moved through it The simulation results of the concentration of in the atmosphere are shown in Fig 3.18 The concentration of 131 131 I I at monitoring stations in Hai Phong, Vinh and Da Nang is shown in Figures 3.21 and 3.22 Fig 3.15 The first cold front appears in January 2018 (a) and moves to Fangchenggang NPP (b) 19 Fig 3.17 Concentration of 131I (µBq/m3) in the boundary layer when the first cold front moved through Fangchenggang The simulation results show the impact assessment of atmospheric transport of radioactivity from Fangchenggang NPP via the East Asian NE monsoon entering our country in winter Before cold front moved to Fangchenggang, the plume were mostly travel towards the mainland of China due to low pressure in this area 20 CONCLUSION In this work, we used the particle dispersion model FLEXPART to simulate long-range transport of 131 I and 137 Cs derived from the Fukushima Daiichi nuclear power plant (FNPP) accident to the tropical western Pacific (TWP) and southeast Asia (SEA) Measurement data at ten monitoring stations located in this region were used for validation of the model results There was good agreement between the model and observations, and the following conclusion can be drawn The airborne radioactivity observed in this region came from both the hemispherical transport following the jet stream and the regional transport in the boundary layer by the East Asian northeast monsoon Due to the late arrivals of both hemispherical and regional plumes, the TWP and SEA region had recorded much lower airborne radioactivity than other regions in the northern hemisphere, which were affected earlier by the FNPP radioactivity The regional transport, however, was more important in contributing Fukushimaderived radioactivity to the regions The 131 I and 137 Cs activity concentrations in the regional plume decreased exponentially with distance from Fukushima and had decreased by half after a distance of 577 km and 433 km, respectively The faster decrease of 137 Cs peak activity concentrations with distance indicates greater deposition loss of 137Cs relative to 131I during atmospheric transport that may be due to its greater particle size Results of analysis of the four statistical indicators also shows better agreement between 21 observations and simulations using greater particle size of 137 Cs and smaller particle size of 131I The agreement between FLEXPART model and observations can be regarded as satisfactory The arrival times of the plumes and the dates of peak concentrations at monitoring stations were predicted very well The correlations between modeled and observed concentrations were statistically significant for most monitoring stations However, differences between predicted and observed concentration values are not insignificant indicating the adequacy of input parameters used in the FLEXPART model that should be addressed in further studies The radiation impact from the Fukushima accident would have been much greater if the accident occurred at the same time as those meteorological conditions that generate regional plumes This finding has significant implications for the radiation impact of emissions from nuclear power plants in the region There are a great number of NPP located in northeast Asia (NEA), and northerlynortheasterly monsoon winds prevailing in East Asia in winter The FLEXPART simulation model validated with the FNPP radiation accident yields confidence regarding its application to model radiation impacts and support emergency planning in response to a possible future nuclear accident in the region For the application of FLEXPART to assess the imparts for nulear power plants near Vietnam’s border, namely Fangchenggang nuclear power plant in western China The results of qualitative analysis in the northeast monsoon scenario show that once again the important role of the monsoon in this region Therefore, it is 22 necessary to build an optimal design of the environmental radioactivity monitoring network, to grasp some containing rules for judging of meteorological changes, especially in winter And mastering simulation skills to be proactive in supporting the emergency preparedness in response to nuclear reactor accidents 23 LIST OF PUBLICATIONS RELATED TO THE THESIS [1] Pham Kim Long, Pham Duy Hien, Nguyen Hao Quang, Do Xuan Anh, Duong Duc Thang, Doan Quang Tuyen (2016), “The ability to use FLEXPART in simulation of the long-range radioactive materials dispersed from nuclear power plants near Vietnam border ”, Nuclear Science and Technology, Vietnam Atomic Energy Society and Vietnam Atomic Energy Institute, Vol.6, No.4, pp 40-48 [2] Phạm Kim Long, Phạm Duy Hiển, Nguyễn Hào Quang (2017), “So sánh kết quan trắc mơ phóng xạ phát tán từ thảm họa hạt nhân Fukushima Daiichi đến Đông Nam Á”, Hội nghị Khoa học cơng nghệ hạt nhân tồn quốc lần thứ 12, Nha Trang, 02-04/8/2017 [3] P K Long, P D Hien, N H Quang (2019), Atmospheric Transport of 131 I and 137 Cs from Fukushima by the East Asian Northeast Monsoon, Journal of Environmental Radioactivity, ISI, IF = 2.263,197, pp 74-80 24 ... 40-48 [2] Phạm Kim Long, Phạm Duy Hiển, Nguyễn Hào Quang (2017), “So sánh kết quan trắc mơ phóng xạ phát tán từ thảm họa hạt nhân Fukushima Daiichi đến Đông Nam Á”, Hội nghị Khoa học công nghệ hạt... studied in order to better explain the atmospheric dispersion of radioactivity CHAPTER EVALUATION METHODS IN ATMOSPHERIC DISPERSION OF RADIONUCLIDES USING FLEXPART 2.1 FLEXPART transport and... Research scope, research objective and research methods The Lagrangian particle dispersion model FLEXPART FLEXPART meteorological input data: Climate Forecast System version (CFSv2), Global Forecast