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Tóm tắt các kết quả mới của luận án: - Góp phần hoàn thiện cơ sở dữ liệu phóng xạ môi trường tại các mỏ khoáng sản chứa NORM. - Bổ sung sự đóng góp liều chiếu trong do hít phải khí phóng xạ thoron (220Rn). - Đã minh chứng sự đóng góp của các nhân phóng xạ trong lương thực được trồng tại các tụ khoáng chứa NORM không làm tăng mức liều hiệu dụng chiếu trong qua đường tiêu hóa. - Đã làm rõ được cơ chế phát tán các nhân phóng xạ trong môi trường nước và đất. 12. Khả năng ứng dụng thực tiễn: - Các kết quả nghiên cứu có thể sử dụng trong việc đánh giá mức độ an toàn phóng xạ cho các cư dân sinh sống và làm việc tại các cơ sở khai khoáng, và là cơ sở để đưa ra các khuyến cáo về mức độ ảnh hưởng của phóng xạ đối với việc thăm dò, khai thác và chế biến các quặng đất hiếm và mỏ sa khoáng, hỗ trợ cho công tác quản lý nhà nước về bảo vệ môi trường và phát triển bền vững. - Kết quả nghiên cứu bên cạnh ý nghĩa khoa học và giá trị sử dụng thực tiễn, việc thực hiện luận án còn góp phần đào tạo nhân lực trong lĩnh vực khai khoáng, môi trường và kỹ thuật hạt nhân 13. Các hướng nghiên cứu tiếp theo: Để có được các đánh giá một cách đầy đủ về mức độ ảnh hưởng của phóng xạ đối với sức khỏe dân chúng sinh sống và làm việc tại các mỏ khoáng sản chứa NORM, cần có những nghiên cứu toàn diện, đầy đủ hơn, về phạm vi, tần suất khảo sát, kỹ thuật quan trắc môi trường phóng xạ, nghiên cứu các mô hình mô phỏng sự phát tán phóng xạ trong môi trường không khí, nước, đất, điều tra dịch tễ học bài bản, khoa học… nhằm rút ra được các kết luận tin cậy và thuyết phục về mức độ ảnh hưởng của phóng xạ đến môi trường tại các mỏ khoáng sản chứa NORM. 14. Các công trình công bố liên quan đến luận án: [1]. Nguyen Van Dung, Dao Dinh Thuan, Dang Duc Nhan, Fernando P. Carvalho, Duong Van Thang, Nguyen Hao Quang (2022). Radiation exposure in a region with natural high background radiation originated from REE deposits at Bat Xat district, Vietnam. Radiation and Environmental Biophysics (ISI). Mẫu 14-NCS [2]. Dung Nguyen Van, Huan Trinh Dinh (2021). Natural radioactivity and radiological hazard evaluation in surface soils at the residential area within Ban Gie monazite placer, Nghe An. Journal of Radioanalytical and Nuclear Chemistry (ISI). [3]. Van Dung N., (2020). Studying the Process of Dispersing Gamma Radiation, Radioactive Gas (Radon, Thoron) in Rare Earth Mines. Modern Environmental Science and Engineering (ISSN 2333-2581), February 2020, Volume 6, No.2, pp.294-301 (Scopus). [4]. Van Dung N., Anh V.T.L. (2021). Radon, Thoron Gas Concentration and Level Living in Ban Gie Monazite Mineral Sand Mine Area, Quy Hop District, Nghe An Province, Vietnam. Proceedings of the 2nd Annual International Conference on Material, Machines and Methods for Sustainable Development (MMMS2020). MMMS 2020. Lecture Notes in Mechanical Engineering. Springer, Cham (Scopus). [5]. Van Dung N., Anh V.T.L. (2021). Natural Radioactivity and Environmental Impact Assessment at Dong Pao Rare Earth Mine, Lai Chau, Vietnam. Proceedings of the 2nd Annual International Conference on Material, Machines and Methods for Sustainable Development (MMMS2020). MMMS 2020. Lecture Notes in Mechanical Engineering. Springer, Cham (Scopus). [6]. Nguyễn Văn Dũng, Trịnh Đình Huấn và Phan Văn Tường (2021). Đánh giá liều chiếu xạ tự nhiên khu vực mỏ đất hiếm Mường Hum, huyện Bát Xát, tỉnh Lào Cai (in Vietnamese), Tạp chí Khoa học kỹ thuật Mỏ - Địa chất, số 62, kỳ 5, tr.106-115. [7]. Nguyễn Văn Dũng (2020). Điều tra dịch tễ học dân cư sống trong khu vực mỏ đất hiếm Mường Hum, huyện Bát Xát, tỉnh Lào Cai. Tạp chí Y dược học Cần Thơ, số 28/2020, trang 134-143. [8]. Nguyễn Văn Dũng, Trịnh Đình Huấn (2020). Nghiên cứu xây dựng cơ sở dữ liệu môi trường phóng xạ tại các mỏ khoáng sản chứa phóng xạ (sa khoáng và đất hiếm). Tuyển tập báo cáo tại Hội nghị toàn quốc Khoa học trái đất và tài nguyên với phát triển bền vững (ERSD2020). [9]. Nguyen Van Dung, Vu Thi Lan Anh, Trinh Dinh Huan (2021). Radon concentrations and forecasting exposure risks to residents and workers in rare earth and copper mines containing radioactivity in Northwest Vietnam. Vietnam Journal of Science, Technology and Engineering, [S.l.], v. 64, n.1, p.78-84, 2022. ISSN 2615-9937. [10]. Nguyen, V. D., Dao, D. T., & Nguyen, H. Q. (2018). Estimation of effective radiation dose for households living in rare earth mines in Nam Xe, Lai Chau province. Journal of Nuclear Science and Technology, 8(2), 27-35. [11]. Nguyen, V. D. (2018). Estimation of radiological parameters associated with mining and processing of coastal sand in Binh Dinh province, Vietnam. Journal of Nuclear Science and Technology, 8(3), 20-28. [12]. Nguyen Van Dung, Vu Thi Lan Anh, Vu Ha Phuong, Dang Thi Ha Thu (2021). Study on the dispersion of radon (222Rn) in geological objects in Bat Xat district, Lao Cai province, North Vietnam. Vietnam Journal of Science, Technology and Engineering. [13]. Nguyễn Văn Dũng, Vũ Thị Lan Anh, Đào Đình Thuần (2020). Phóng xạ tự nhiên và mức liều chiếu xạ khu vực mỏ đất hiếm Yên Phú, huyện Văn Yên, tỉnh Yên Bái. Tuyển Mẫu 14-NCS tập báo cáo tại Hội nghị toàn quốc Khoa học trái đất và tài nguyên với phát triển bền vững (ERSD2020). [14]. Nguyễn Văn Dũng, Đào Đình Thuần, (2019). Hoạt độ alpha và bêta trong mẫu thực phẩm khu vực xã Mường Hum, huyện Bát Xát, tỉnh Lào Cai. Hội nghị Nghiên cứu cơ bản trong “Khoa học trái đất và môi trường”. Nhà Xuất Bản Khoa học Tự nhiên và Công nghệ. [15]. Nguyễn Văn Dũng, (2018). Nghiên cứu đặc điểm phát tán phóng xạ đến môi trường do hoạt động khai thác và chế biến quặng titan ven biển tỉnh Bình Định. Hội nghị khoa học Trái đất và Tài nguyên với Phát triển bền vững (ERSD 2018).
MINISTRY OF EDUCATION AND TRAINING MINISTRY OF SCIENCE AND TECHNOLOGY VIETNAM ATOMIC ENERGY INSTITUTE NGUYEN VAN DUNG STUDY ON BUILDING DATABASE AND EVALUATION MODEL OF IRRADIATION DOSE IN SOME RARE EARTH MINES AND PLACER MINES Major: Atomic and nuclear physics Code: 9.44.01.06 SUMMARY OF THE Ph.D THESIS HANOI – 2022 The thesis is completed at: Vietnam Atomic Energy Institute Supervision: Dr Nguyen Hao Quang Dr Dao Dinh Thuan Referee 1: Referee 2: Referee 3: The thesis wil be defended against the Institute-level Council of the doctoral dissertation, meeting at the 3rd floor Hall, Nuclear Training Center - Vietnam Atomic Energy Institute at hours date month 2022 Finding the thesis at: - The National Library of Vietnam - Library Nuclear Training Center Introduction In the living environment, humans are always under the impact of ionizing radiation caused by natural and artificial radionuclides with an average effective dose of about 2.96 mSv/year; of which about 82% are due to natural radionuclides Natural radionuclides that have been present in the Earth's crust since the Earth's formation are called primordial radionuclides Primordial radionuclides, especially 238U, 232Th and 40K present in the topsoil contribute mainly to the naturally occurring terrestrial gamma radiation dose In addition, the decay products of the 238U and 232Th chains are isotopes of radon (222Rn; 220 Rn), which is a radioactive inert gas that is easily dispersed into the air, causing a clear dose through inhalation The dose caused by radon is estimated to account for about 59% of the total effective dose from the natural radioactive background Therefore, the assessment of the activity concentration of natural radionuclides in the environment as a basis for assessing the risks of public health effects due to natural ionizing radiation has been of particular interest in physics health, especially around areas with radioactive anomalies such as radioactive mineral deposits or naturally occurring radionuclides and so-called naturally occurring radioactive materials: Naturally Occuring Radioactive Materials (NORM) Our country is on the way of strong socio-economicdevelopment, so it needs a lot of natural resources and minerals to serve the process of industrialization and modernization Along with the development process, many environmental problems have arisen, including environmental radiation due to the investigation, exploration and exploitation of minerals containing NORM The thesis with the topic "Study on building database and evaluation model of irradiation dose in some rare earth mines and placer mines" focuses on the following objectives: 1)Study the mechanism of radioactive release into the environment and develop a process to evaluate the effects of radiation on the environment in the exploration, exploitation and processing of NORMcontaining minerals; 2) Study and building a database of environmental radiation monitoring at mineral mines; 3) Study and evaluate the effects of natural radiation in some areas with radioactive anomalies on the environment and local community health during the process of exploration, mining and processing of minerals containing NORM The research method of the thesis includes conducting field surveys, taking samples of soil, water, food and measuring radiation dose levels during mineral activities in the study area by method and modern equipment such as: RAD-7 meter and CR-39 nuclear trace detector for instantaneous measurement and cumulative measurement of radioactive gas concentrations (222Rn; 220Rn) in the air; external gamma dosimeter DKS-96; equipment gamma spectrometer to determine the concentration of radionuclides activity 40 K, 226Ra, 232Th in samples of soil, food, water; Estimating the hazard index (Hazard index), to determine the probability of causing cancer in the population around the mine area; using models to study the mechanism of releasing natural radionuclides into the environment during mining activities and to establish the relationship between the geological environment and related environmental factors are naturally occurring radionuclides The content of the thesis includes: beside the introduction, conclusion and references, the thesis presents the main content in chapters as follows: Chapter An overview of environmental radiation and the situation of mineral exploitation and processing in rare earth and placer mines; Chapter Research methods, conducting experiments and building a database of environmental radiation; Chapter Results and discussion Chapter An overview of environmental radiation and the situation of mineral exploitation and processing in rare earth and placer mines 1.1 Natural radioactive background The dose of ionizing radiation that humans receive is derived from radionuclides found in the earth's crust, radiation from space, medicine, food, and radionuclides found in the human body collectively referred to as the natural radioactive background In Figure 1.1, radiation sources and average contributions to the effective annual dose received by humans Figure 1.1 Sources of average annual radiation dose for humans The total dose level is from 2.4 to 2.9 mSv/year Mineral exploration, extraction and processing activities (containing NORM) must be conducted to excavate, transport, store and process ores with a concentration of radionuclides in the ore tens or hundreds of times higher than that of the ore radiation safety standards allow These are activities that cause radionuclides to disperse into the surrounding environment, especially in water, air, soil, dust In the content of the thesis, the author focuses on studying natural radioactive characteristics, evaluating radiation dose levels at two locations with two types of NORM-containing ores, rare earth (Muong Hum, Lao Cai) and placer monazite (Ban Gie, Nghe An) 1.2 Geological features – rare earth minerals and placer deposits 1.2.1 Muong Hum rare earth mine Muong Hum rare earth mine in Nam Pung and Muong Hum communes, Bat Xat district, Lao Cai province, is limited by coordinates 22 05122055 North latitude and 103068103074 East longitude The geological features of the area include the formations: Sin Quyen (PP-MPsq), Ban Nguon (D1bn), Cha Pa (NPcp), Ban Pap (D1-2bp), Nam Xe - Tam Duong (aG-aSy/Ent), Muong Hum (aG/PZ2mh), Quaternary (dpQ) According to the results of investigation and assessment, this is a rare earth mine with large reserves, rare earth resources in place of 175,000 tons of TR2O3, rare earth resources weighing 37,500 tons ThO2 content = 0.12%; U3O8=0.02% 1.2.2 Ban Gie monazite mine Ban Gié monazite placer mine has geographical coordinates 19o4630 north latitude, 105o29'50 east longitude in Yen Hop commune, Quy Hop district, in the west of Nghe An province The geological features include the following formations: Bu Khang Formation (PR3-ε1bk); Song Ca Formation (O3-S1sc); Dong Do Formation (T3n-rdd) Monazite ore bodies are distributed in valleys with an area of ~1,100,000 m2, with reserves of 190,356 tons of monazite; ilmenite 826,990 tons; 332,670 tons of zircon, results of analysis of mineral composition include: monazite, ilmenite, xenotin, zircon… uranium and thorium Chemical composition: monazite =150÷4,800g/m3; ilmenite=200÷2.734g/m3; zircon= 29 ÷143 g/m3; Ag=167g/m3; U3O8=0.055÷0.087%;ThO2=4.62÷6.61% 1.3 Existing problems in environmental radiation research at mineral mines of our country In the study and investigation of environmental radiation at mineral mines in Vietnam, the following main shortcomings were found: 1) In the investigation and assessment of environmental radiation, only methods of measuring environmental radiation were applied parameters of the radioactive field, there are no associated geological - geochemical surveys Therefore, it is not possible to determine the dispersion characteristics that change the radiation dose content due to the mining and processing activities of minerals containing NORM; 2) The environmental radiation database at mineral deposits containing NORM has just calculated the external irradiance due to gamma radiation and internal irradiation due to radon gas inhalation, excluding the radiation dose caused by thoron (222Rn) results, and determine whether caused by radionuclides in the soil, water, etc.; 3) The system of methods of assessing the effects of natural irradiation on “Radiation work” is human activities that change the dose of irradiation such as exploration, mining and processing of minerals containing NORM highly misleading in research results; 4) The process and method of overall assessment of the influence of environmental radiation not have sufficient data on radiation dose components, radionuclides activity concentrations in the exploration and mining activities mining and processing of minerals containing radionuclides for the public living in the mine and its vicinity Chapter Research methods, conducting experiments and building a database of environmental radiation 2.1 Research methodology system In this study, the following combination of methods was selected by the author 1) Collecting and synthesizing documents on natural conditions, geologyminerals, environmental geology, current state of environmental radioactivity at rare earth mines and placer mines in the study area; 2) Building a geoenvironment model as a basis for studying the mechanism of radionuclides release into the environment due to mineral activities in rare earth mines and placer containing NORM; 3) Building a database of environmental radiation; 4) Field survey, sampling, measurement and determination of radiation dose levels during mineral activities in the study area by modern methods and equipment such as: CR39 nuclear trace detector, radon meter instantaneous RAD-7, gamma spectrometer with ultrapure semiconductor germanium (HPGe) detector, gamma dose rate meter DKS-96; 5) Sociological investigation of public health status in different age groups and sexes, determining the correlation between disease rate and radiation dose in the survey area; 6) Determination of radiation dose variation due to mineral activities in the study area 2.2 Phương pháp phân tích tài liệu Document analysis method 2.2.1 Calculate the absorbed gamma dose rate at a distance of m from the ground The absorbed gamma dose rate D at a distance of m above the deposition area is given by the following formula: D(nGy/h) = 0,46ARa + 0,62ATh + 0,042AK (2.1) In which: ARa, ATh and AK are the active concentrations of 226Ra, 232Th and 40 K in the soil sample (Bq/kg) 2.2.2.Calculate the annual mean effective gamma exposure dose (AGED) The annual average gamma effective dose (AGED) over the deposition area is calculated by the formula: AGED = OAGED + IAGED (2.2) Where: OAGED is the annual average gamma effective dose outside the home; IAGED is the annual average gamma effective dose in the home OAGED calculated according to the formula: OAGED(Sv/year) = D(Gy/h)×DCF(Sv/Gy)×OF×T (2.3) Where DCF is the conversion factor from absorbed dose to effective dose and equals 0.7 (Sv/Gy); OF is the coefficient that people work outdoors (occupation coefficient OF = 0.2); T is the number of hours in the year (T=8.760 h/year) IAGED calculated according to the formula: IAGED(Sv/year) = D(Gy/h)×DCF(Sv/Gy)×OF×T (2.4) For IAGED the occupancy factor (OF) is recommended by UNSCEAR to be taken as 0.8 The annual effective gamma radiation dose for the general public of the mineral deposit area can be calculated according to the following formula: AGED (Sv/year) = D(Gy/h)×DCF(Sv/Gy)×T (h/year) (2.5) 2.2.3 Calculation of the gastrointestinal effect (Ein) The effective dose administered through the gastrointestinal tract is calculated by the formula: 𝐸𝑖𝑛 = ∑𝑖(𝑄𝑖 × 𝐶𝑖,𝑟 ) × 𝑓𝑟 × 𝑔𝑟 (2.6) In which: i is the symbol indicating the food-food group (cereals, vegetables, meat, fish ) or drinking water; Qi and Ci,r are the annual consumption of food-food/drinking water (kg/year) and the activity concentration of radionuclides r in the sample, respectively; f r is the radioactive fraction r that can be absorbed in the gastrointestinal tract; gr is the dose-to-activity conversion factor of the radionuclide r(Sv/Bq) 2.2.4 Calculate the annual mean effective dose from inhalation of radon through inhalation The effective dose (internal projection) due to inhalation of radon (222Rn) is calculated by the formula: ERn = CRn × FRn × KRn × T (2.5) In which: ERn (nSv/year) is the average effective dose per year caused by respiratory Rn; CRn is the indoor Rn activity concentration (Bq/m3); FRn is the mean radioequilibrium coefficient between 222Rn and its descendants and is calculated as 0.46; KRn is the conversion factor from unit of activity to unit of effective dose and is equal to nSv Bq-1h-1 m3 multiplied by 222Rn; T is the time of year (8,760 h/year) Similarly, the mean annual effective dose of thoron ( 220Rn) is calculated by the formula: ETn = CTn × FTn × KTn × T (2.6) Where ETn is the effective dose (internal exposure) caused by thoron (mSv/year); CTn is the indoor thoron activity concentration (Bq/m3); FTn is the mean equilibrium coefficient between thoron and progeny and is equal to 0.09; KTn is the conversion factor from activity unit to effective dose unit and is equal to 40 nSv/Bq h/m3 ; T is the time of year 8760 2.2.5 Equivalent Radial Activity Equivalent Radi activity is calculated according to the formula: Raeq = 0,07AK +ARa + 1,43ATh (2.7) 40 226 where AK, ARA and ATh are the activity concentrations of K, Ra and 232Th in soil, respectively, in Bq/kg The upper limit of equivalent Radi activity is 370 Bq/kg 2.2.6 Outside and inside hazard index To assist in the assessment of radiation risk, the hazard indexes of external exposure (Hex) and internal exposure (Hin) are also determined by the formula: AK ARa ATh Hex = 4810 + 370 + 259 (2.8) A A A K Ra Th Hin = 4810 + 185 + 259 (2.9) 40 226 where, AK, ARA and ATh are the activity concentrations of K, Ra and 232Th nuclei in soil, respectively To ensure radiation safety, Hex, Hin < 2.2.7 Cancer risk over the life span of the community The risk of cancer in the lifetime of the population in the mining area is an estimate of the probability of cancer in the population in the study area in the lifetime due to exposure to ionizing radiation from the environment The ELCR index is calculated using the following formula: ELCR = AEDE×DL×RF (2.10) In which DL is the average life time of residents and according to ICRP recommendation, DL is taken as 70 years; RF is a specific indicator of cancer risk when exposed to a radiation dose of mSv/year For random effects of radiation, ICRP recommends using an RF value of 0.05 for members of the public 2.2.8 Method of determining radiation dose variation after mineral activity in the study area The determination of the current radiation dose around the area of mineral deposits containing NORM must be based on a network of survey points evenly distributed over the area, and each measurement point value must be a characteristic value of a homogeneous object on each small area it represents Furthermore, the measurement points must be linear, so to determine the most common radiation dose values, the author uses the following two methods: Method 1: Determine the characteristic radiation dose value of the geological units of the mine area because different geological units contain different types of rock and characterize the activity concentration of radionuclides Method 2: Divide the entire study area into plots, each plot ensures geological homogeneity and has a minimum number of measurement points of 30 points for gamma dose rate and radon gas concentration to determine frequency charts capacity On the basis of analysis and synthesis of documents, the author has participated in implementing topics and projects before and during the thesis implementation in mines where exploration and exploitation of NORMcontaining minerals are active, the author has: Developed and completed the process of determining the effects of radiation on the environment due to the exploration and exploitation of radioactive minerals and minerals containing natural radionuclides The process of assessing the effects of environmental radiation at mineral deposits is carried out according to the following diagram (Figure 2.1) 2.3 Building a database of environmental radiation In order to establish a database to manage and access environmental radiological documents, it is necessary to develop a common standard system of environmental radiological databases (PXMT) in areas (KV) according to the following criteria: standard document format, database structure, system structure of archived documents and format of archived documents The program aims to manage the database, to allow updating and exploiting the database to serve the State management requirements on environmental radiation for each locality and region On the basis of documentary sources on environmental radiation at mineral deposits containing NORM, the author has built a database of environmental radiation according to the following diagram (Figure 2.2) Dispersion of radionuclides from exploration and exploitation to the environment Figure 2.1 The process of assessing the effects of environmental radiation in mineral activities containing NORM 12,80 16,00 16 5,6.10-2 12,51 15,64 15 14 5,5.10-2 7,90 9,87 10 3,6 3,4.10-2 4,68 5,85 5,8 4,5 2,0.10-2 1,80 2,24 2,2 1,2 0,8.10-2 3,18 3,98 3,9 1,9 1,4.10-2 Average 10,69 Stdev 6,36 Table 3.2 Annual effective dose of intranasal irradiation the foods (S-03) (S-04) (S-05) (S-06) (S-07) (S-08) 2,61 2,55 1,61 0,96 0,37 0,65 3,20 3,13 1,97 1,17 0,45 0,80 Food Consumption rate kg/person/year Rice Corn Cassave Vegetable Water 147,75 5,37 1,28 76,14 730 Effective dose per year through ingestion mSv/year/person 1,67.10-4 1,06.10-3 4,12.10-4 1,04.10-2 2,04.10-1 2,20.10-1 Total Contribution of each food to the total effective dose, % 0,7 0,5 0,2 5,9 92,7 100 Table 3.3 Active concentrations of radon (222Rn) and thoron (220Rn) in indoor air; effective annual dose (ERn and ETn) and total effective annual dose (ERn+Tn) due to inhalation of radon and thoron for residents in Hanoi and the Muong Hum rare earth ore mine area 222 Tọa độ STT 10 11 12 13 14 X 105o83'13'' 105o77'68'' 105o79'08'' 103o71'47'' 103o71'43'' 103o71'48'' 103o71'27'' 103o70'13'' 103o70'26'' 103o70'14'' 103o71'02'' 103o71'24'' 103o70'85'' 103o70'74'' Y 20o97'86'' 21o07'09'' 21o06'75'' 22o50'85'' 22o50'45'' 22o50'47'' 22o51'05'' 22o51'10'' 22o51'22'' 22o51'32'' 22o51'06'' 22o51'17'' 22o52'25'' 22o52'30'' Rn (Rn) Bq m-3 41±7 74±7 58±6 130±11 97±10 85±11 91±12 68±8 66±6 72±8 64±7 111±10 73±9 87±11 11 Rn(Tn) Bq m-3 ERn, mSv a-1 ETn, mSv a-1 ERn+Tn, mSv a-1 60±5 22±8 Bkg 17±7 104±9 32±6 63±6 31±5 13±5 67±6 48±5 111±8 50±6 15±3 1,37 2,45 1,92 4,31 3,24 2,83 3,02 2,26 2,20 2,39 2,13 3,67 2,43 2,89 0,69 0,25 0,00 0,20 1,20 0,37 0,73 0,36 0,15 0,78 0,56 1,28 0,58 0,18 2,06 2,70 1,92 4,51 4,44 3,20 3,76 2,62 2,35 3,18 2,68 4,95 3,01 3,07 220 15 16 17 18 19 20 103o70'78'' 103o71'21'' 103o71'33'' 103o71'34'' 103o71'39'' 103o71'31'' 22o52'42'' 22o51'27'' 22o50'91'' 22o50'73'' 22o50'86'' 22o50'85'' 77±9 123±12 507±26 896±22 304±14 310±15 439±10 186±8 350±15 73±13 2352±22 586±14 2,54 4,09 16,77 29,62 10,05 10,24 5,05 2,14 4,03 0,85 27,06 6,74 7,60 6,23 20,80 30,47 37,10 16,98 a The annual average external effective dose due to gamma radiation from the soil over the deposition area : From Table 3.1, it can be seen that the average value of dose rate D caused by radionuclides in the soil is 3.92 Gy/h The results show that the dose rate D in the region is 54 times higher than the national average (0.07±0.03) Gy/h With such a high gamma dose rate, the area of Muong Hum rare earth ore mine can be considered as an area with a high radiation background From the results of measurement and calculation of gamma dose rate on the Muong Hum area, it is found that rare-earth mineral deposits also create high gamma dose levels for the public and this area can be considered as "The area with high radiation background" With the above gamma dose rate, the total effective annual external radiation dose (AEED) for the public living far from the rare earth mineral deposit Muong Hum is from 300 to 500 m with an average height of 10.69 mSv/year (Table 3.1 ), 22 times higher than the world average of 0.48 mSv/year b The annual average effective dose of radiation for the population around the deposition area From Table 3.2, it shows that the level of internal radiation dose due to food and drink of the people in this area is 0.22 mSv/year and domestic radiation, specifically 40K, contributes up to 92.7% to the total internal radiation dose 5.9% of the total dose was from broccoli (Brassica juncea), the contribution of radionuclides of the 238U and 232Th radionuclides in food was very small ( 250 Bq/m3) 3.3.2 Bản Gié Evaluation of radiation dose levels at Ban Gié monazite mine site a Composition of radioisotopes in the soil environment The results of analysis of radionuclide activity concentrations in surface soil samples in the area had an average price of (1265,2); (715,6); (1557.5) and (37122) Bq/kg for 226Ra, 238U, 232Th and 40K respectively In general, the mean activity concentrations of radionuclides 226Ra, 238U and 232 Th were higher than the world average (32, 33 and 45 Bq/kg) For 40K is lower than the world average value (420 Bq/kg) The asymmetric distribution curve of natural radionuclides is shown in Figure 3.5 Figure 3.4 Map of radioactive zoning of rare earth mine Muong Hum a) b) 15 d) c) Figure 3.5 Distribution curves of 226Ra, 238U, 232Th and 40K The correlation between different natural radionuclides in the study area is shown in Figure 3.6 Compared with some other regions in Vietnam, the natural radionuclides content in the soil of the study area is higher than that in Ho Chi Minh City and the average value of soil in 63 provinces and cities in Vietnam Compared with monazite placer, the concentration of natural radionuclides in the study area is lower than that reported in some monazite placer deposits in the world such as Kerala coast (India), Ullal coast (India), South Madagascar a) b) d) c) Figure 3.6 Correlation between natural radionuclides b Radiation hazard indicators 16 Calculation results of radiological hazard indicators (Raeq,D,AEDE, ELCR) for soil in the study area and world average values of these indicators are listed in Table 3.5 Table 3.5 Calculation results of radiation hazard indicators Location Indicators average Max Min On the background of the ore body Raeq (Bq/kg) 470 833 D (nGy/h) AEDE (Sv/y) ELCR(10-3) Raeq (Bq/kg) D (nGy/h) AEDE (Sv/y) ELCR (10-3) 212 260 1,12 294 133 163 0,70 375 460 1,99 586 270 331 1,43 The area near the ore body 146 Standar d error 207 World average 370 65,9 80,9 0,35 68,7 30,8 37,8 0,16 92,8 114 0,49 150 67,5 82,7 0,36 57 70 0,29 370 57 70 0,29 The correlation between Raeq and the concentration of natural radionuclides activity inside and outside the ore body is shown in Figure 3.7 and Figure 3.8 Figure 3.7 Correlation between Raeq and concentration of natural radionuclides in the ore body Figure 3.8 Correlation between Raeq and concentration of natural radionuclides outside the ore body Table 3.5 also shows that the average value of absorbed dose (D) is 294 nGy/h inside the ore body and 133 nGy/h outside the ore body The average annual effective dose (AEDE) value in the ore body is 260 Sv/year, outside the ore 17 body is 163 Sv/year The average risk of cancer (ELCR) when living in the ore body is 1.12.10-3 and outside the ore body is 0.7.10-3 on average It can be seen that the radiation hazard indexes (D, AEDE, ELCR) in the ore body are about 1.6 times higher than those outside the ore body In the ore body, these stats are about 3.7 times higher than the world average while near the ore body these stats are about 2.3 times higher than the world average c Natural radiation dose levels at Ban Gie monazite mine The total equivalent dose in the detailed investigation area varied from 1.07 to 15.66 mSv/year, with an average of 4.65 mSv/year The author has built a map of radioactive zoning of the Ban Gie monazite placer mine (Figure 3.9) Legend Contuor and value Areas with total radiation dose > 3mSv/year River Traffic Areas with total radiation dose > 5mSv/year Areas with total radiation dose > 7mSv/year Residential Monazite ore body Figure 3.9 Map of environmental radioactive zoning in Ban Gie d Evaluation of the increased irradiation dose due to mineral activities at Ban Gié monazite placer mine The results of radiation dose calculation before and after the exploration of Ban Gie monazite ore are shown in Table 3.8 18 Table 3.8 Calculation results of increased radiation dose due to mineral activities of Ban Gié monazite mine TT Mine Ban Gie Pre-exploration radiation dose (mSv/year) Hn Hp Heff 4,43 1,95 Post-exploration radiation dose (mSv/year) Hn Hp Heff 6,38 5,76 2,75 8,51 Incremental dose level (mSv/year) 2,13 From the above table, it can be determined that the value of increased radiation dose due to monazite ore exploration is 2.13 mSv/year, times larger than the limit dose for the population 3.4 Sociological investigation, health situation of people living in and around radioactive mineral mines The comparison of health situation and disease characteristics of people living in mines with high radioactive activity and living outside mines with normal radioactivity is based on the study of the correlation between radiation levels, irradiation dose level with the health situation and disease characteristics of the people in the mine area (Table 3.9) Table 3.9 Correlation between radiation content, radiation dose level with health situation, disease characteristics of people in mining areas Radiation concentration in living environment Area Sample Type Soil Bq/kg Rare earth mines contain radioacti ve material Water Bq/l Food Bq/kg Soil Bq/kg Water Bq/l Food Bq/kg Total radiation dose H(mSv/năm) Health status and disease characteristics concentra tion Rn (Bq/m3) 238U 232Th 56,3÷576,5 234,5 0,208÷0,564 0,330 456,5÷7.653,3 3.431,5 0,009÷0,025 0,019 0,287÷4,662 1,510 0,182÷19,040 3,280 34,76÷234,2 145,67 102÷3.213 1.359 0,211÷0,409 0,286 0,099÷0,020 0,015 0,272÷2,520 0,939 0,099÷6,634 1,827 19 Nậm Pung 71÷876 334 Mường Hum 30÷675 133 Nậm Pung 16,62 Mường Hum 10,34 According to medical examination results: People suffering from respiratory and digestive diseases are equivalent to people living in the vicinity of mines The incidence of ENT diseases for people aged > 45 years is twice as high as in the Radiation concentration in living environment Area Sample Type Soil Bq/kg water Bq/l Total radiation dose H(mSv/năm) Health status and disease characteristics 2,1÷4,5 vicinity of the mines According to the results of retrospective medical examination and treatment records: The highest group of diseases is respiratory (53%, digestive disease 15%) The prevalence of the disease is higher in women than in men (respiratory disease in men 68.6%; women 43.3%) Digestive (male 11.4%; female 16.7%) Other diseases (male 14.3%; female 33.3%) The prevalence of the disease according to the agricultural occupation group accounted for the highest rate (male 59.4% female 87.1%) concentra tion Rn (Bq/m3) 238U 232Th 3,5÷27,4 13,4 16,8÷76,3 25,3 0,021÷0,49 0,123 0,049÷0,499 0,258 Food Bq/kg Area outside the mining area (Sang Ma Sao commun e area) 22÷35 0,039÷0,680 0,190 0,081÷0,445 0,271 3.5 Environmental radiation database During the implementation of the thesis, the author participated in building an environmental radiological database based on VBF software, which is integrated with Mapinfor The program is designed to be simple, the user works with data through the menu system or on graphical windows in an intuitive way The 20 program has a unified interface and terminology for users to easily exploit according to the same principle, that is, if you have mastered the operations from one window, the operation on other windows is very easy because the way it works is exactly the same The structure of the program includes the following main directory: - The SYSTEM folder contains system parameters and weight variables of the natural gamma program - The DATA letter contains the measured data (generate, gamma dose rate, radon, thoron ) and the calculation results of the program In addition to the function of data management, searching and looking up data, using the gta program will help us to determine the effective annual dose of natural gamma radiation, radiation dose through inhalation, ingestion, draw graphs, charts, maps at each survey area Conclusions and recommendations Research results of the thesis The thesis has accomplished the research objectives and content set out The main results of the thesis are as follows: - Built a geo-environmental model to clarify the mechanism of radionuclides dispersion due to exploration and exploitation of rare earth minerals and placer minerals to the environment: + Muong Hum rare earth mine: Water environment: average pH 7.1 is typical for neutral environment The average Eh redox potential is 126.2 mV, which is characterized by a weak redox potential Thus, the water in the Muong Hum mine area is favorable for the dissolution of +6 valence uranium compounds; Soil environment: The average pH of 7.6 is typical for a neutral environment Eh ranges from 187÷324 mV, which is typical for a strong oxidizing environment, which is a favorable condition for dissolving and transporting uranium and U6+ compounds + Ban Gié monazite mine: Water environment: The average pH value is 8.1±0.1, typical for a weak alkaline environment The average Eh value of 118.0±6.7 mV is typical for the oxidizing environment With such characteristics, it is very convenient for uranium to dissolve and spread in the aquatic environment; Soil environment: The pH value is in the range of 5.2÷8.8 and the average is 8.2±0.2, typical for the environment from weak acid to weak alkali The average Eh value is 130±47.7 mV With such characteristics, it is very convenient to dissolve and transport compounds of uranium and radium in the soil environment 21 Building a emission model of gamma radiation and radioactive gas according to the model of ore bodies containing radionuclides: with the ore body having a U3O8 content at 0.01%, the gamma dose rate influence in the atmosphere is due to they cause at a minimum distance of up to 30 m, that is, the influence level of soil and rock containing ore from trench works is about 50 R/h (equivalent to an external radiation dose of about mSv/year), far away from the area of soil and rock mass containing ore 30m, the dose rate is not significantly affected (0.1mSv/year); The concentration of radioactive gas radon declines slowly with altitude - Additional database of environmental radiation at mineral mines has been developed, the program allows to calculate effective dose, internal dose (through inhalation and digestion), external radiation dose, update results and check research in the survey area - The environmental radioactivity characteristics in the survey area have been identified: + Muong Hum rare earth mine: The rare earth mine area causes an effective dose of gamma radiation up to 13.84±3.44 mSv/year, 29 times higher than the world average value of 0.48 mSv /five Radionuclides activity concentrations in food and drinking water comparable to those found in other regions without rare earth ore deposits result in an effective annual gastrointestinal dose of 0.22 mSv/year is equivalent to the global average annual dose value of 0.29 mSv/year The mean annual effective dose due to inhalation of radon and thoron for local people living at a distance of to km from the ore body was 3.97±1.55 mSv/year and for people living at a distance from the body 300-500 m ore is 26.34 ± 9.15 mSv/year, nearly 21 times higher than the global average dose due to inhalation of radon and thoron gas of 1.26 mS/year The total effective annual dose for the population living near the rare earth ore body is 40.66±9.78 mSv/year, 17 times higher than the corresponding value of 2.4 mSv/year At the rare earth mine, the pre-exploration radiation dose value was 9.22 mSv/year and the post-exploration radiation dose value was 13.87 mSv/year From that, it is determined that the value of increased radiation dose due to rare earth ore exploration is 4.65 mSv/year, times larger than the limit dose for the population + Ban Gie monazite placer mine: It has been determined that the gamma (D) absorption dose varies from 65.9÷375.0 nGy/h (average 212 nGy/h) in the ore body and from 30.8÷270.0 nGy/h (average 133 nGy/h) outside the ore body The equivalent effective annual dose (AEDE) in the ore body ranges from 80.9÷460.0 Sv/year (average 260 Sv/year), outside the ore body varies from 37.8÷331.0 Sv/year (average 163 Sv/year) Cancer risk (ELCR) for living near ore bodies 22 varied from (0.35÷1.99).10-3 (mean 1.12.10-3) and outside of ore bodies was from (0.16÷1,43).10-3 (average 0.70.10-3) It can be seen that the radiation hazard indexes (D, AEDE, ELCR) in the area near the ore body are about 1.6 times higher than the corresponding indicators in the area near the ore body In the area on the ore body, these indicators are about 3.7 times higher than the world average while in the area near the ore body, these indicators are about 2.3 times higher than the average value world average - A method has been developed to evaluate the radioactive equilibrium between 226Ra and 238U in soil samples in the study area; - A map of environmental radioactive zoning has been established for the study areas; - Developed a process, a system of methods to assess the effects of radiation on the environment in exploration, mining and processing of NORM-containing minerals New points of the thesis - Contributing to completing the environmental radiological database at mineral deposits containing NORM - Addition of the contribution of internal dose due to inhalation of radioactive thoron (220Rn) - It has been demonstrated that the contribution of radionuclides in food grown at NORM-containing mineral deposits does not increase the effective dose level of gastrointestinal irradiation - The mechanism of dispersal of radionuclides in water and soil environment has been clarified Suggestions for further research In order to have a complete assessment of the impact of radiation on the health of the population living and working at mineral deposits containing NORMs, more comprehensive studies are needed scope, frequency of survey, techniques for monitoring the radioactive environment, research on simulation models of radioactive dispersion in the air, water, and soil environment, methodical and scientific epidemiological investigation in order to draw reliable and convincing conclusions about the impact of radiation on the environment at mineral deposits containing NORM List of published works of the author Publications directly related to the thesis 1.1 International publication Nguyen Van Dung, Dao Dinh Thuan, Dang Duc Nhan, Fernando P Carvalho, Duong Van Thang, Nguyen Hao Quang (2022) Radiation exposure in a region with 23 natural high background radiation originated from REE deposits at Bat Xat district, Vietnam Radiation and Environmental Biophysics (Published online) DOI: https://doi.org/10.1007/s00411-022-00971-9 Dung Nguyen Van, Huan Trinh Dinh (2021) Natural radioactivity and radiological hazard evaluation in surface soils at the residential area within Ban Gie monazite placer, Nghe An Journal of Radioanalytical and Nuclear Chemistry (Published online) https://doi.org/10.1007/s10967-021-08171-3 Van Dung N., (2020) Studying the Process of Dispersing Gamma Radiation, Radioactive Gas (Radon, Thoron) in Rare Earth Mines Modern Environmental Science and Engineering (ISSN 2333-2581), February 2020, Volume 6, No.2, pp.294-301, DOI:10.15341/mese(2333-2581)/02.06.2020/014 Van Dung N., Anh V.T.L (2021) Radon, Thoron Gas Concentration and Level Living in Ban Gie Monazite Mineral Sand Mine Area, Quy Hop District, Nghe An Province, Vietnam Proceedings of the 2nd Annual International Conference on Material, Machines and Methods for Sustainable Development (MMMS2020) MMMS 2020 Lecture Notes in Mechanical Engineering Springer, Cham https://doi.org/10.1007/978-3-030-69610-8_83 (Scopus) 1.2 Publication in the country Nguyen Van Dung, Trinh Dinh Huan and Phan Van Tuong (2021) Evaluation of natural irradiation dose in the area of rare earth mine Muong Hum, Bat Xat district, Lao Cai province (in Vietnamese), Journal of Science and Technology Mining Geology, No 62, period 5, pp.106-115 DOI:10.46326/JMES.2021.62(5).10 Nguyen Van Dung (2020) Epidemiological investigation of the population living in the rare earth mine Muong Hum, Bat Xat district, Lao Cai province Can Tho Journal of Medicine and Pharmacy, No 28/2020, pages 134-143 Nguyen Van Dung, Trinh Dinh Huan (2020) Research on building a database of radioactive environment in radioactive mineral deposits (placer and rare earth) National Conference of Earth and Resource Sciences with Sustainable Development (ERSD2020) Nguyen Van Dung, Vu Thi Lan Anh, Trinh Dinh Huan (2021) Radon concentrations and forecasting exposure risks to residents and workers in rare earth and copper mines containing radioactivity in Northwest Vietnam Vietnam Journal of Science, Technology and Engineering, [S.l.], v 64, n 1, p 78-84, 2022 ISSN 2615-9937 DOI: https://doi.org/10.31276/VJSTE.64(1).78-84 Nguyen, V D., Dao, D T., & Nguyen, H Q (2018) Estimation of effective radiation dose for households living in rare earth mines in Nam Xe, Lai Chau province Journal of Nuclear Science and Technology, 8(2), 27-35 https://doi.org/10.53747/jnst.v8i2.88 10 Nguyen, V D (2018) Estimation of radiological parameters associated with mining and processing of coastal sand in Binh Dinh province, Vietnam Journal of Nuclear Science and Technology, 8(3), 20-28 https://doi.org/10.53747/jnst.v8i3.70 Other Publications 24 11 Van Dung N., Anh V.T.L (2021) Natural Radioactivity and Environmental Impact Assessment at Dong Pao Rare Earth Mine, Lai Chau, Vietnam Proceedings of the 2nd Annual International Conference on Material, Machines and Methods for Sustainable Development (MMMS2020) MMMS 2020 Lecture Notes in Mechanical Engineering Springer, Cham https://doi.org/10.1007/978-3-030-69610-8_77 (Scopus) 12 Nguyen Van Dung, Vu Thi Lan Anh (2020) Survey on the concentration of Radon (222Rn) and Radi (226Ra) in domestic water in Bac Tu Liem district, Hanoi City Vietnam Journal of Science and Technology 58(5A) (2020)5463 Doi:10.15625/2525-2518/58/5a/15191 13 Nguyen Van Dung, Trinh Dinh Huan, Dao Dinh Thuan (2020) Evaluation of changes in environmental radioactive composition in copper ore mining and processing activities in Sin Quyen mine, Lao Cai province Vietnam Journal of Science and Technology, Vol 62, No 8, 2020, pages 8-12 14 Nguyen Van Dung, Vu Thi Lan Anh, Vu Ha Phuong, Dang Thi Ha Thu (2021) Study on the dispersion of radon (222Rn) in geological objects in Bat Xat district, Lao Cai province, North Vietnam Vietnam Journal of Science, Technology and Engineering 15 Nguyen Van Dung, Vu Thi Lan Anh, Dao Dinh Thuan (2020) Natural radiation and radiation dose levels at Yen Phu rare earth mine, Van Yen district, Yen Bai province National Conference of Earth and Resource Sciences with Sustainable Development (ERSD2020) 16 Nguyen Van Dung, Dao Dinh Thuan, (2019) Alpha and beta activities in food samples from Muong Hum commune, Bat Xat district, Lao Cai province Basic Research Conference in “Earth and Environmental Sciences” Science and Technology Publishing House, 2019 http://dx.doi.org/10.15625/vap.2019,000220 17 Nguyen Van Dung (2018) Research on radioactive emission characteristics to the environment due to mining and processing of titanium ore along the coast of Binh Dinh province National Conference of Earth and Resource Sciences with Sustainable Development (ERSD 2018) 25 ... February 2020, Volume 6, No.2, pp.294-301, DOI:10.15341/mese(2333-2581)/02.06.2020/014 Van Dung N., Anh V.T.L (2021) Radon, Thoron Gas Concentration and Level Living in Ban Gie Monazite Mineral Sand... Earth and Resource Sciences with Sustainable Development (ERSD2020) Nguyen Van Dung, Vu Thi Lan Anh, Trinh Dinh Huan (2021) Radon concentrations and forecasting exposure risks to residents and... Technology, 8(3), 20-28 https://doi.org/10.53747/jnst.v8i3.70 Other Publications 24 11 Van Dung N., Anh V.T.L (2021) Natural Radioactivity and Environmental Impact Assessment at Dong Pao Rare Earth