Properties of the soil in rice fields and transfer of cesium to rice plants = 水田土壌の性質とセシウムの米への移行

広島大学学位論文 NGUYEN THANH HAI 広島大学学位論文 Properties of the Soil in Rice Fields and Transfer of Cesium to Rice Plants (水田土壌の性質とセシウムの米への移行) 令和 年度 広島大学大学院理学研究科 化学専攻 NGUYEN THANH HAI Table of contents Chapter General Introduction 1.1 Overview about Fukushima Daiichi Nuclear Power Plant accident 1.2 Soil property in Fukushima 1.3 Purpose of the research 1.4 Literature review References Chapter Sampling and Method 2.1 Sampling 11 2.2 Sample preparation 14 2.3 Radioactivity calculation 19 2.3.1 Choosing gamma energy 19 2.3.2 Law of radioactive decay 21 2.3.3 Calculation of radioactivity 22 2.3.4 Background elimination 26 2.3.5 Detection Limit 27 2.3.6 Transfer factor calculation 28 References 28 Chapter Depth Distribution of Radioactive Cesium in Soil after Cultivation and the Difference by the Year of the Uptake of Radioactive Cesium in Rice in Fukushima Prefecture after the Nuclear Accident 3.1 Introduction 29 3.2 Materials and methods 30 3.3 Results and discussion 31 3.3.1 Radioactivity in soils 31 3.3.2 Radioactivity in rice plants 34 3.4 Conclusion 36 References 37 Chapter Study on paddy soil in Fukushima using Mӧssbauer spectroscopy 4.1 Introduction 39 4.2 Experimental 40 4.3 Results and discussion 40 4.4 Conclusion 48 i References 48 Chapter The changing in radioactivity by year 5.1 Introduction 50 5.2 Vertical distribution of radioactivity in paddy field 51 5.3 Changing in ratio 134Cs /137Cs by year 55 5.4 Changing in radioactivity by size of grain soil 57 5.5 Mӧssbauer spectra for the samples obtained in 2018 61 References 62 Chapter General Conclusion Acknowledgements 65 Figures Figure 1-1 The epicenter of Great East Japan Earthquake and position of nearby nuclear power plants Figure 1-2 Air dose rates map of 80km area from the FDNPP by time Figure 1-3 Air dose rates at 1m above ground surface in Fukushima on April 29, 2011 Figure 2-1 Sampling site 12 Figure 2-2 Paddy field before and after harvest 13 Figure 2-3 Soil auger and 30cm5cm PVC liner tube 13 Figure 2-4 Sampling in paddy field 14 Figure 2-5 Drying and weighing soil samples 14 Figure 2-6 Rice sample 15 Figure 2-7 Rice sample in U8 container as rice grain (a), rice stem (b), and root (c) 15 Figure 2-8 Grinding soil sample and taking out trash 16 Figure 2-9 Removing roots from soil sample 17 Figure 2-10 Stainless steel sieving meshes 17 Figure 2-11 Weighing soil sample for sieving 18 Figure 2-12 Shaking the sieves 18 Figure 2-13 Categorized grain soils 18 Figure 2-14 Decay scheme of Cesium 134 isotope 20 Figure 2-15 Decay scheme of Cesium 137 isotope 20 Figure 2-16 Decay scheme of Potasium 40 isotope 21 ii Figure 2-17 Spectrum of a sample which was measured in Ge-detector 21 Figure 2-18 Efficiency of MX033U8PP source set in Germanium detector 23 Figure 2-19 Logarithmic scale of Count Efficiency versus Energy 24 Figure 2-20 Relationship between Count Efficiency versus Thickness of standard samples 25 Figure 2-21 Background spectrum in Ge-detector 27 Figure 3-1 Depth dependence of Cesium 137 concentration for the soil obtained on April 26th, 2014 The average value for the five points is compared 31 Figure 3-2 Depth dependence of 40K concentration for the soil obtained on April 26th, 2014 The average value for the five points is compared 33 Figure 4-1 Typical 57Fe Mӧssbauer spectrum at room temperature 41 Figure 4-2 Ratio of Fe(II) to the sum of divalent and trivalent iron A-1 to D-3 show the sampling point 43 Figure 4-3 Change of 57Fe Mӧssbauer absorption depending on the soil size in 2014 44 Figure 4-4 The change in the least relative transmission depending on soil size 48 Figure 5-1 Processes that affect the amount of radioactivity in the soil 50 Figure 5-2 Vertical distribution of 134Cs in paddy fields in 2014 52 Figure 5-3 Vertical distribution of 137Cs in paddy fields in 2014 52 Figure 5-4 Vertical distribution of 40K in paddy fields in 2014 53 Figure 5-5 Vertical distribution of 134Cs in paddy fields in 2018 54 Figure 5-6 Vertical distribution of 137Cs in paddy fields in 2018 54 Figure 5-7 Vertical distribution of 40K in paddy fields in 2018 55 Figure 5-8 Changing of ratio 134Cs /137Cs from 2014 to 2018 56 Figure 5-9 Percentage grain size in Field A and Field B in 2014 58 Figure 5-10 Percentage grain size in Field C and Field D in 2014 58 Figure 5-11 Percentage grain size in Field A and Field B in 2018 59 Figure 5-12 Percentage grain size in Field C and Field D in 2018 59 Figure 5-13 Radiocesium by grain size in 2014 60 Figure 5-14 Radiocesium by grain size in 2018 61 Figure 5-15 Mӧssbauer spectra for sampling sites in fields A, B, C, and D obtained in 2018 62 iii Tables Table 2-1 Background measurement of 40K 27 Table 3-1 Radioactivity concentration with standard deviation in soil (0–5 cm depth) obtained on September 25th, 2014 34 Table 3-2 Radioactivity concentration with standard deviation in soil (0–5 cm depth) obtained on August 21st, 2015 34 Table 3-3 Radioactivity concentration with standard deviation in soil (0–5 cm depth) obtained on October 30th, 2015 34 Table 3-4 Radioactivity concentration with standard deviation in rice ear obtained on August 21st, 2015 36 Table 4-1 Mӧssbauer parameters for the soil samples without sieving measured from April to July, 2015 41 Table 4-2 Mӧssbauer parameters for the soil samples based on soil size measured from April to August, 2019 45 Table 5-1 Ratio of 134Cs / 137Cs from 2014 to 2018 56 Appendices Appendix Measurement of MX033U8PP source set (Japan Radioisotope Association) .66 Appendix Count Efficiency (CE) of MX033U8PP source set (Japan Radioisotope Association) 66 Appendix Logarithmic of Count Efficiency and Energy MX033U8PP source set (Japan Radioisotope Association) 66 Appendix Count Efficiency and Thickness of MX033U8PP source set (Japan Radioisotope Association) 66 iv Chapter General Introduction 1.1 Overview about Fukushima Daiichi Nuclear Power Plant accident Fukushima Daiichi Nuclear Power Plant (hereinafter referred to as the FDNPP) is located in Okuma Town and Futaba Town, Futaba County, Fukushima Prefecture – which is in the northeast of Honshu Island, Japan FDNPP is run by the Tokyo Electric Power Company (TEPCO) FDNPP has units with BWR *-type reactors in an area approximate 3.5 million square meters near the coastline of Pacific Ocean The total power generating capacity of the facilities is 4,696 million kilowatts1) There are about 1,100 employees of TEPCO who work at FDNPP In addition, about 2,000 employees of TEPCO-associate companies or plant manufactures work at the power station2) At 14:46 on 11 March 2011, a 9.0 magnitude earthquake with the epicenter in the depth of 24km below the Sanriku region, Japan which called as Great East Japan Earthquake occurred It was the strongest ever recorded earthquake in Japan 50 minutes later, a massive tsunami struck northeastern Japan (called as the Tohoku region) as shown in Figure 1-1 On the day of disaster occurred, about 750 employees of TEPCO were working in the plant The terrible earthquake destroyed all off-line power supply of FDNPP At this time the reactor's emergency safety system has been activated and the standby power supply system was working to power the reactor cooling system However, the 15m tsunami triggered by seismic activity struck and damaged emergency power supplies, including backup batteries As a result, the reactor cooling system could not work, causing the water in the reactor to evaporate and lower the water level in the * BWR - Boiling Water Reactor reactor High temperature steam reacted with the exposed fuel rods in the furnace to produce hydrogen gas Hydrogen gas accumulated in the furnaces leading to explosions in units 1, 3, and releasing radioactive materials to the environment1) Figure 1-1 The epicenter of Great East Japan Earthquake and position of nearby nuclear power plants1) Due to weather factors (such as wind, terrain, rain, snow, etc.), radioactive materials released from the FDNPP after the explosion dispersed to the Northwest as described in Figure 1-2 Radioactive materials mainly contain Cesium 137, Cesium 134, and Iodine 131 According to The Nuclear and Industrial Safety Agency (NISA) within the Ministry of Economy, Trade and Industry of Japan, the total discharge amounts to the air from the reactors of FDNPP were approximate 1.6105TBq for Iodine 131 and approximate 1.5104TBq for Cesium 1371) Meanwhile TEPCO estimated that it was 5105TBq for Iodine 131 and 1104TBq for Cesium 1372) Figure 1-2 Air dose rates map of 80km area from the FDNPP by time3) 1.2 Soil property in Fukushima According to T M Nakanishi4) soil in Japan is 36% Gray Lowland, 30% Gley, and 10% Andosol In Fukushima prefecture’s paddy fields the soil profile is 51% Gray Lowland soil, 17% Gley soil, and 10% Andosol There is a difference between the soil in mountain area in Fukushima and average value in Japan In upland fields of Concerning to the concentration of 40 K in paddy fields in 2018, caused by fallowing and water erosion, in the 5cm top soil concentration of 40 K was lower than 2014 but the undisturbed deeper layer of soil had not changed Figure 5-5 Vertical distribution of 134Cs in paddy fields in 2018 Figure 5-6 Vertical distribution of 137Cs in paddy fields in 2018 54 Figure 5-7 Vertical distribution of 40K in paddy fields in 2018 5.3 Changing in ratio 134Cs /137Cs by year An article of Y Nishizawa et al.1) (2015) indicated that the ratio of airbone 134Cs and 137Cs on March 15, 2011 near the study area of this study was 1.05 This ratio was also investigated in paddy soil in the study area Over time, because short half-life (about years), the amount of 134Cs decreases rapidly than 137Cs This led to a decrease in the ratio of 134 Cs / 137 Cs with time Table 5-1describes the value of this ratio when surveyed from 2014 to 2018 in the study area Figure 5-8 depicts the relationship of 134Cs / 137Cs ratio and time In years, this ratio became to less than one halved 55 Table 5-1 Ratio of 134Cs / 137Cs from 2014 to 2018 Year 134Cs (Bq/kg) 137Cs (Bq/kg) 134Cs /137Cs 2014 1025.40217.596 2728.9627.720 0.3760.007 2015 720.7895.520 2883.56310.516 0.2500.002 2016 432.1697.474 2276.98815.251 0.1900.004 2017 386.3836.178 2902.44815.233 0.1330.002 2018 232.9465.507 2066.91413.055 0.1130.003 Figure 5-8 Changing of ratio 134Cs /137Cs from 2014 to 2018 56 5.4 Changing in radioactivity by size of grain soil In order to understand the characteristics of radioactivity in soil of the paddy field of the study, the size distribution of surface soil was investigated Particle size analysis of the soil was conducted on the topsoil layer of paddy fields in the study area Figure 5-9, Figure 5-10, Figure 5-11 and Figure 5-12 describe the grain size composition of A and B rice fields (upstream fields) and C and D rice fields (downstream fields) in 2014 and 2018 Until 2014, all rice fields were cultivated Silt and clay particles, due to their small size, light weight, float in water and are easily washed away in the stream Therefore, the amount of silt and clay in the soil sample is not much Occupation in the field samples are mainly fine sand (35% in fields A and B, 46.4% - fields C and D) and medium sand (37.8% - Fields A and B, 32.7% - Fields C and D) In the measured results in 2018, because the upstream field was abandoned since 2015, the soil in this area is not disturbed by the plowing activity Therefore, the silt and clay content in Fields A and B increased (19.3%) 57 Figure 5-9 Percentage grain size in Field A and Field B in 2014 Figure 5-10 Percentage grain size in Field C and Field D in 2014 58 Figure 5-11 Percentage grain size in Field A and Field B in 2018 Figure 5-12 Percentage grain size in Field C and Field D in 2018 In terms of radioactivity content, it can be observed that most of the radioactive cesium accumulates in small soil particles (Fine sand, Silt and Clay) In 2014, the amount of cesium radioactivity was concentrated in these particle sizes (Figure 5-13) 59 Figure 5-13 Radiocesium by grain size in 2014 Looking at Figure 5-14, it can be seen that the radiocesium content in the downstream fields which are cultivated has a relatively high amount of radiation accumulated in small particle sizes This can be explained by the fact that the amount of dissolved cesium ions present in the paddy water makes the radioactive cesium content higher, easily to form soil colloidal particles containing Cesium ions Yoshimura et al.2)(2016) also explained that because the paddy fields were kept flooded for several days after puddling, the fine soil particles which settle slowly were discharged preferentially These fine soil particles which absorpted radiocesium therefore accumulated in the downstream paddy fields 60 Figure 5-14 Radiocesium by grain size in 2018 5.5 Mӧssbauer spectra for the samples obtained in 2018 The Figure 5-15 shows the change of 57 Fe Mӧssbauer absorption depending on the surface soil’s size of samples which were taken in 2018 The intensity changes are similar to the change obtained in the soil of 2014 (Figure 4-3) But if we look at the intensity of the soil larger than 850 micrometer (red line), while the intensity of fields C, D in 2018 was similar with this in 2014 but the intensity of fields A, B was much higher in comparison to 2014 In other hand, the intensity difference between Fields A, B and Fields C, D (which were fallowing since 2015) become large by years It could be concluded that the fallowing made iron much accumulated in the soil larger than 850 micrometer 61 Figure 5-15 Mӧssbauer spectra for sampling sites in fields A, B, C, and D obtained in 2018 References Nishizawa, Y., Yoshida, M., Sanada, Y.,Torii, T., Distribution of the 134Cs/137Cs ratio around the Fukushima Daiichi nuclear power plant using an unmanned helicopter radiation monitoring system, Journal of Nuclear Science and Technology Volume 53, Issue 4, 468-474 (2016) Yoshimura, K., Onda, Y., Wakahara, T., Time Dependence of the 137Cs Concentration in Particles Discharged from Rice Paddies to Freshwater Bodies after the Fukushima Daiichi NPP Accident, Environmental Science & Technology, 50, 8, 4186-4193 (2016) https://doi.org/10.1021/acs.est.5b05513 62 Chapter General Conclusion It has been nearly years since the earthquake, tsunami and radiation disaster from FDNPP Along with a lot of scientific research on this incident so far, this study has contributed a small part to the understanding of radioactive cesium pollution and its spread in soil as well as into rice Results of continuous research from 2014 to 2018 for this study showed that there was accumulation of radioactive pollution in rice fields in the study area from the FDNPP 2011 accident Soil and rice samples were collected in paddy fields cultivated many years before and after the FDNPP disaster The amount of radioactivity in the soil is found to be highest in the surface soil and decreases with depth The average value of radioactive cesium in the surface soil in 2014 was 37547Bq/kg and in 2018 was 23003Bq/kg However, there are also some survey sites with unusually high radioactive cesium content (depending on the year) The radioactive cesium content of the measured rice was low (compared to provisional regulation of The Ministry of Health, Labor, and Welfare was 100 Bq/kg§) These are the sites that receive water from the field from nearby pond and the Abukuma River This acknowledges the efforts to prevent incidents of radioactive emissions from FDNPP 2011 and efforts to decontaminate soil environment in the study area With respect to the amount of radioactivity in the soil, there has been a decrease in the annual content of the surface soil and a migration of radioactivity to the deeper soil layer The impact of fallow land on the amount of radioactive cesium accumulated § Notice No 0315 Article of the Department of Food Safety March 15, 2012 63 was also studied The radioactive content of the shift in soil is mainly accumulated in small particle sizes and depends on the oxidative/reductive atmosphere of the soil environment It is clear that this oxidative/reductive atmosphere is closely related to the dissolution of cesium ions accumulated in soil colloidal particles The oxidative atmosphere affects the features of the field and induces the uptake of radioactive cesium by rice plants The amount of iron embedded in larger soil particles may also affect the transfer of radioactive cesium from soil to the rice body There is a possibility that the iron works as catalyst to dissolve radioactive cesium from soil 137Cs penetrated more in fallowed fields compared with the cultivated fields The fallowing effect was observed in the amount of iron of soils larger than 850 micrometer 64 Acknowledgements I would like to express the deepest appreciation to my supervisor, Professor Satoru Nakashima of Hiroshima University, for the patient guidance, supporting me during these years I would also like to thank Assistant Professor Sunao Miyashita, Professor Tsutomu Mizuta, Professor Shinya Matsuura, and Professor Kiriko Sakata whose comments made enormous contribution to my work I would like to thank my friend and colleague Mr Masaya Tsujimoto who helped me much in studying and living in Japan, thanks to you I gratefully appreciate the financial support to my study from The Phoenix Leader Education Program (Hiroshima Initiative) for Renaissance from Radiation Disaster, which funded by The Ministry of Education, Culture, Sports, Science and Technology of Japan 65 5mm Standard Source, Radioactivity Eɣ (KeV) T1/2 (Days) Bq Error Error(%) 418.20 23.84 5.7 464.00 27.82 1.50 5.4 271.00 27.82 1.50 5.4 271.00 27.97 1.43 5.1 137.70 697.00 36.94 5.3 27.70 34.78 1.84 5.3 64.84 34.66 1.80 5.2 10950.00 38.34 1.99 5.2 312.50 42.00 2.14 5.1 106.60 45.49 2.37 5.2 1923.92 45.49 2.37 5.2 1923.92 42.00 2.14 5.1 106.60 88 122 136 166 320 514 662 835 898 1173 1333 1836 10 mm Standard Source, Radioactivity Eɣ (KeV) T1/2 (Days) Bq Error Error(%) 836.00 44.31 5.3 464.00 55.63 2.73 4.9 271.00 55.63 2.73 4.9 271.00 55.94 2.63 4.7 137.70 1394.00 68.31 4.9 27.70 69.60 3.34 4.8 64.84 69.30 3.33 4.8 10950.00 76.70 3.68 4.8 312.50 84.00 3.86 4.6 106.60 91.00 4.37 4.8 1923.92 91.00 4.37 4.8 1923.92 84.00 3.86 4.6 106.60 88 122 136 166 320 514 662 835 898 1173 1333 1836 20 mm Standard Source, Radioactivity Eɣ (KeV) T1/2 (Days) Bq Error Error(%) 1673.00 87.00 5.2 464.00 111.30 5.34 4.8 271.00 111.30 5.34 4.8 271.00 111.90 5.15 4.6 137.70 2787.00 133.78 4.8 27.70 139.10 6.54 4.7 64.84 138.60 6.51 4.7 10950.00 153.30 7.21 4.7 312.50 168.00 7.56 4.5 106.60 181.90 8.55 4.7 1923.92 181.90 8.55 4.7 1923.92 168.00 7.56 4.5 106.60 88 122 136 166 320 514 662 835 898 1173 1333 1836 30 mm Standard Source, Radioactivity Eɣ (KeV) T1/2 (Days) Bq Error Error(%) 2509.00 130.47 5.2 464.00 166.90 8.01 4.8 271.00 166.90 8.01 4.8 271.00 167.80 7.72 4.6 137.70 4181.00 200.69 4.8 27.70 208.70 9.81 4.7 64.84 208.00 9.78 4.7 10950.00 230.00 10.81 4.7 312.50 252.00 11.34 4.5 106.60 272.90 12.55 4.6 1923.92 272.90 12.55 4.6 1923.92 252.00 11.34 4.5 106.60 88 122 136 166 320 514 662 835 898 1173 1333 1836 50 mm Standard Source, Radioactivity Eɣ (KeV) T1/2 (Days) Bq Error Error(%) 4182.00 213.28 5.1 464.00 278.20 13.35 4.8 271.00 278.20 13.35 4.8 271.00 279.70 12.59 4.5 137.70 6970.00 334.56 4.8 27.70 347.80 16.35 4.7 64.84 346.60 16.29 4.7 10950.00 383.40 17.64 4.6 312.50 420.00 18.90 4.5 106.60 454.90 20.93 4.6 1923.92 454.90 20.93 4.6 1923.92 420.00 18.90 4.5 106.60 88 122 136 166 320 514 662 835 898 1173 1333 1836 λ t (lapsed time) 15.9785 15.9785 15.9785 15.9785 15.9785 15.9785 15.9785 15.9785 15.9785 15.9785 15.9785 15.9785 t (lapsed time) 0.0015 2016/08/01 12:00 0.0026 2016/08/17 11:29 0.0026 0.0050 0.0250 0.0107 0.0001 0.0022 0.0065 0.0004 0.0004 0.0065 λ 16.0132 16.0132 16.0132 16.0132 16.0132 16.0132 16.0132 16.0132 16.0132 16.0132 16.0132 16.0132 t (lapsed time) 0.0015 2016/08/01 12:00 0.0026 2016/08/17 12:19 0.0026 0.0050 0.0250 0.0107 0.0001 0.0022 0.0065 0.0004 0.0004 0.0065 λ 16.1125 16.1125 16.1125 16.1125 16.1125 16.1125 16.1125 16.1125 16.1125 16.1125 16.1125 16.1125 t (lapsed time) 0.0015 2016/08/01 12:00 0.0026 2016/08/17 14:42 0.0026 0.0050 0.0250 0.0107 0.0001 0.0022 0.0065 0.0004 0.0004 0.0065 λ 16.1799 16.1799 16.1799 16.1799 16.1799 16.1799 16.1799 16.1799 16.1799 16.1799 16.1799 16.1799 16.2424 16.2424 16.2424 16.2424 16.2424 16.2424 16.2424 16.2424 16.2424 16.2424 16.2424 16.2424 t (lapsed time) 0.0015 2016/08/01 12:00 0.0026 2016/08/17 16:19 0.0026 0.0050 0.0250 0.0107 0.0001 0.0022 0.0065 0.0004 0.0004 0.0065 λ 0.0015 2016/08/01 12:00 0.0026 2016/08/17 17:49 0.0026 0.0050 0.0250 0.0107 0.0001 0.0022 0.0065 0.0004 0.0004 0.0065 Exp (-λ*t) 0.9764 0.9600 0.9600 0.9227 0.6704 0.8430 0.9990 0.9652 0.9013 0.9943 0.9943 0.9013 Exp (-λ*t) 0.9764 0.9599 0.9599 0.9226 0.6698 0.8427 0.9990 0.9651 0.9011 0.9942 0.9942 0.9011 Exp (-λ*t) 0.9762 0.9596 0.9596 0.9221 0.6682 0.8418 0.9990 0.9649 0.9005 0.9942 0.9942 0.9005 Exp (-λ*t) 0.9761 0.9595 0.9595 0.9218 0.6671 0.8412 0.9990 0.9647 0.9001 0.9942 0.9942 0.9001 Exp (-λ*t) 0.9760 0.9593 0.9593 0.9215 0.6660 0.8406 0.9990 0.9646 0.8998 0.9942 0.9942 0.8998 Standard Source, on Measurement Bq Error Error(%) 408.34 23.28 5.70 26.71 1.44 5.40 26.71 1.44 5.40 25.81 1.32 5.10 467.29 24.77 5.30 29.32 1.55 5.30 34.62 1.80 5.20 37.00 1.92 5.20 37.86 1.93 5.10 45.23 2.35 5.20 45.23 2.35 5.20 37.86 1.93 5.10 Standard Source, on Measurement Bq Error Error(%) 816.24 43.26 5.30 53.40 2.62 4.90 53.40 2.62 4.90 51.61 2.43 4.70 933.77 45.75 4.90 58.65 2.82 4.80 69.23 3.32 4.80 74.02 3.55 4.80 75.69 3.48 4.60 90.48 4.34 4.80 90.48 4.34 4.80 75.69 3.48 4.60 Standard Source, on Measurement Bq Error Error(%) 1633.21 84.93 5.20 106.81 5.13 4.80 106.81 5.13 4.80 103.18 4.75 4.60 89.39 4.80 5.50 4.70 6.51 4.70 6.95 4.70 6.81 4.50 8.50 4.70 8.50 4.70 6.81 4.50 117.09 138.46 147.92 151.29 180.85 180.85 151.29 Standard Source, on Measurement Bq Error Error(%) 2449.08 127.35 5.20 160.13 7.69 4.80 160.13 7.69 4.80 154.68 7.12 4.60 2788.98 133.87 4.80 175.55 8.25 4.70 207.79 9.77 4.70 221.89 10.43 4.70 226.83 10.21 4.50 271.31 12.48 4.60 271.31 12.48 4.60 226.83 10.21 4.50 Standard Source, on Measurement Bq Error Error(%) 4081.75 208.17 5.10 266.88 12.81 4.80 266.88 12.81 4.80 257.74 11.60 4.50 4642.15 222.82 4.80 292.36 13.74 4.70 346.24 16.27 4.70 369.83 17.01 4.60 377.90 17.01 4.50 452.25 20.80 4.60 452.25 20.80 4.60 377.90 17.01 4.50 Emission Rate (Ir) 3.73% 85.60% 10.60% 79.90% 9.83% 98% 85% 99.98% 94.00% 99.90% 99.98% 99.37% Emission Rate (Ir) 3.73% 85.60% 10.60% 79.90% 9.83% 98% 85% 99.98% 94.00% 99.90% 99.98% 99.37% Emission Rate (Ir) 3.73% 85.60% 10.60% 79.90% 9.83% 98% 85% 99.98% 94.00% 99.90% 99.98% 99.37% Emission Rate (Ir) 3.73% 85.60% 10.60% 79.90% 9.83% 98% 85% 99.98% 94.00% 99.90% 99.98% 99.37% Emission Rate (Ir) 3.73% 85.60% 10.60% 79.90% 9.83% 98% 85% 99.98% 94.00% 99.90% 99.98% 99.37% Net Count Net Count Error_net Error_net(%) Error_count 16758.50 188.45 1.12 129.45 31817.00 217.04 0.68 178.37 3900.50 139.2 3.57 62.45 27714.00 209.45 0.76 166.48 40048.33 222.08 0.55 200.12 16495.00 145.38 0.88 128.43 14368.17 139.3 0.97 119.87 15355.00 136.47 0.89 123.92 12913.00 128.25 0.99 113.64 13589.67 122.95 0.90 116.57 12161.17 114.24 0.94 110.28 8067.00 90.88 1.13 89.82 Net Count Net Count Error_net Error_net(%) Error_count 20994.00 200.06 0.95 144.89 40408.00 249.48 0.62 201.02 5047.00 152 3.01 71.04 34631.67 226.16 0.65 186.10 48649.00 244.74 0.50 220.57 20677.50 164.51 0.80 143.80 17390.00 150.5 0.87 131.87 18772.67 150.73 0.80 137.01 15582.83 138.7 0.89 124.83 15918.00 133.63 0.84 126.17 14475.00 125.33 0.87 120.31 9193.00 97.62 1.06 95.88 Net Count Net Count Error_net Error_net(%) Error_count 19774.33 191.93 0.97 140.62 37789.00 228.42 0.60 194.39 4648.00 142.56 3.07 68.18 32228.67 216.65 0.67 179.52 45135.67 232.29 0.51 212.45 18931.00 153.16 0.81 137.59 15782.67 140.88 0.89 125.63 16885.00 143.61 0.85 129.94 13996.83 129.55 0.93 118.31 14419.50 127.57 0.88 120.08 12995.00 117.93 0.91 114.00 8097.67 92.47 1.14 89.99 Net Count Net Count Error_net Error_net(%) Error_count 19817.33 187.24 0.94 140.77 38771.00 232.98 0.60 196.90 4693.00 137.74 2.94 68.51 32394.17 214.1 0.66 179.98 44595.33 230.17 0.52 211.18 18378.00 151.49 0.82 135.57 15577.00 143.88 0.92 124.81 16414.00 139.61 0.85 128.12 13229.83 127.34 0.96 115.02 13369.00 123.32 0.92 115.62 12265.00 115.23 0.94 110.75 7767.50 89.59 1.15 88.13 Net Count Net Count Error_net Error_net(%) Error_count 2239.00 63.27 2.83 47.32 4190.00 76.13 1.82 64.73 573.00 44.51 7.77 23.94 3626.00 72.37 2.00 60.22 4788.67 76.42 1.60 69.20 1965.00 51.43 2.62 44.33 1649.67 45.26 2.74 40.62 1685.00 44.69 2.65 41.05 1383.00 41.46 3.00 37.19 1362.50 39.34 2.89 36.91 1234.67 36.87 2.99 35.14 801.00 28.65 3.58 28.30 Error_count(%) 0.77 0.56 1.60 0.60 0.50 0.78 0.83 0.81 0.88 0.86 0.91 1.11 Error_count(%) 0.69 0.50 1.41 0.54 0.45 0.70 0.76 0.73 0.80 0.79 0.83 1.04 Error_count(%) 0.71 0.51 1.47 0.56 0.47 0.73 0.80 0.77 0.85 0.83 0.88 1.11 Error_count(%) 0.71 0.51 1.46 0.56 0.47 0.74 0.80 0.78 0.87 0.86 0.90 1.13 Error_count(%) 2.11 1.54 4.18 1.66 1.45 2.26 2.46 2.44 2.69 2.71 2.85 3.53 Live Time (s) 1689.30 1689.30 1689.30 1689.30 1689.30 1689.30 1689.30 1689.30 1689.30 1689.30 1689.30 1689.30 Live Time (s) 9035.30 9035.30 9035.30 9035.30 9035.30 9035.30 9035.30 9035.30 9035.30 9035.30 9035.30 9035.30 Live Time (s) 5875.10 5875.10 5875.10 5875.10 5875.10 5875.10 5875.10 5875.10 5875.10 5875.10 5875.10 5875.10 Live Time (s) 5216.40 5216.40 5216.40 5216.40 5216.40 5216.40 5216.40 5216.40 5216.40 5216.40 5216.40 5216.40 Live Time (s) 3564.90 3564.90 3564.90 3564.90 3564.90 3564.90 3564.90 3564.90 3564.90 3564.90 3564.90 3564.90 CPS 4.70 8.93 1.09 7.77 11.23 4.63 4.03 4.31 3.62 3.81 3.41 2.26 CPS 4.02 7.75 0.97 6.64 9.33 3.96 3.33 3.60 2.99 3.05 2.77 1.76 CPS 3.37 6.43 0.79 5.49 7.68 3.22 2.69 2.87 2.38 2.45 2.21 1.38 CPS 2.19 4.29 0.52 3.59 4.94 2.03 1.72 1.82 1.46 1.48 1.36 0.86 CPS 1.33 2.48 0.34 2.15 2.83 1.16 0.98 1.00 0.82 0.81 0.73 0.47 CPS - Real Count Effeciency (CE) Error Error(%) CE Error Error(%) 0.05 1.12 0.03 0.00 5.22 0.06 0.68 0.04 0.00 4.85 0.04 3.57 0.04 0.00 5.98 0.06 0.76 0.04 0.00 4.56 0.06 0.55 0.02 0.00 4.83 0.04 0.88 0.02 0.00 4.78 0.04 0.97 0.01 0.00 4.80 0.04 0.89 0.01 0.00 4.69 0.04 0.99 0.01 0.00 4.61 0.03 0.90 0.01 0.00 4.69 0.03 0.94 0.01 0.00 4.69 0.03 1.13 0.01 0.00 4.64 CPS - Real Count Effeciency (CE) Error Error(%) CE Error Error(%) 0.04 0.95 0.04 0.00 5.29 0.05 0.62 0.06 0.00 4.84 0.03 3.01 0.06 0.00 5.67 0.04 0.65 0.05 0.00 4.65 0.05 0.50 0.03 0.00 4.83 0.03 0.80 0.02 0.00 4.77 0.03 0.87 0.02 0.00 4.78 0.03 0.80 0.02 0.00 4.77 0.03 0.89 0.01 0.00 4.59 0.03 0.84 0.01 0.00 4.68 0.02 0.87 0.01 0.00 4.68 0.02 1.06 0.01 0.00 4.62 CPS - Real Count Effeciency (CE) Error Error(%) CE Error Error(%) 0.03 0.97 0.06 0.00 5.29 0.04 0.60 0.07 0.00 4.84 0.02 3.07 0.07 0.00 5.70 0.04 0.67 0.07 0.00 4.65 0.04 0.51 0.04 0.00 4.83 0.03 0.81 0.03 0.00 4.77 0.02 0.89 0.02 0.00 4.78 0.02 0.85 0.02 0.00 4.78 0.02 0.93 0.02 0.00 4.59 0.02 0.88 0.01 0.00 4.78 0.02 0.91 0.01 0.00 4.79 0.02 1.14 0.01 0.00 4.64 CPS - Real Count Effeciency (CE) Error Error(%) CE Error Error(%) 0.02 0.94 0.07 0.00 5.38 0.03 0.60 0.09 0.00 4.94 0.02 2.94 0.09 0.01 5.71 0.02 0.66 0.09 0.00 4.75 0.03 0.52 0.05 0.00 4.93 0.02 0.82 0.04 0.00 4.87 0.02 0.92 0.03 0.00 4.89 0.02 0.85 0.02 0.00 4.87 0.01 0.96 0.02 0.00 4.70 0.01 0.92 0.02 0.00 4.89 0.01 0.94 0.02 0.00 4.89 0.01 1.15 0.01 0.00 4.74 CPS - Real Count Effeciency (CE) Error Error(%) CE Error Error(%) 0.04 2.83 0.09 0.01 6.36 0.05 1.82 0.11 0.01 5.70 0.03 7.77 0.12 0.01 9.46 0.04 2.00 0.10 0.01 5.48 0.05 1.60 0.06 0.00 5.54 0.03 2.62 0.04 0.00 5.91 0.03 2.74 0.03 0.00 5.88 0.03 2.65 0.03 0.00 5.84 0.02 3.00 0.02 0.00 5.92 0.02 2.89 0.02 0.00 5.95 0.02 2.99 0.02 0.00 6.00 0.02 3.58 0.01 0.00 6.23 Appendix Measurement of MX033U8PP source set (Japan Radioisotope Association) Radioisotope Standard Source 4024 Cd-109 Co-57 Ce-139 Cr-51 Sr-85 Cs-137 Mn-54 Y-88 Co-60 Y-88 Radioisotope Standard Source 4025 Cd-109 Co-57 Ce-139 Cr-51 Sr-85 Cs-137 Mn-54 Y-88 Co-60 Y-88 Radioisotope Standard Source 4026 Cd-109 Co-57 Ce-139 Cr-51 Sr-85 Cs-137 Mn-54 Y-88 Co-60 Y-88 Radioisotope Standard Source 4027 Cd-109 Co-57 Ce-139 Cr-51 Sr-85 Cs-137 Mn-54 Y-88 Co-60 Y-88 Radioisotope Standard Source 4028 Cd-109 Co-57 Ce-139 Cr-51 Sr-85 Cs-137 Mn-54 Y-88 Co-60 Y-88 66 Energy (keV) CE 0.0870 0.1085 0.1198 0.1041 0.0617 0.0405 0.0332 0.0270 0.0230 0.0179 0.0162 0.0126 mm Error 0.0055 0.0062 0.0113 0.0057 0.0034 0.0024 0.0020 0.0016 0.0014 0.0011 0.0010 0.0008 Error(%) 6.3620 5.6975 9.4604 5.4766 5.5350 5.9110 5.8794 5.8373 5.9158 5.9478 5.9965 6.2292 CE 0.0720 0.0939 0.0918 0.0869 0.0538 0.0354 0.0293 0.0245 0.0206 0.0164 0.0150 0.0114 10 mm Error 0.0039 0.0046 0.0052 0.0041 0.0026 0.0017 0.0014 0.0012 0.0010 0.0008 0.0007 0.0005 Error(%) 5.3836 4.9367 5.7118 4.7462 4.9271 4.8703 4.8881 4.8748 4.6996 4.8878 4.8911 4.7424 CE 0.0553 0.0704 0.0699 0.0665 0.0420 0.0281 0.0228 0.0194 0.0168 0.0136 0.0122 0.0092 20 mm Error 0.0029 0.0034 0.0040 0.0031 0.0020 0.0013 0.0011 0.0009 0.0008 0.0006 0.0006 0.0004 Error(%) 5.2898 4.8379 5.6962 4.6489 4.8275 4.7691 4.7840 4.7763 4.5942 4.7825 4.7868 4.6426 CE 0.0441 0.0565 0.0570 0.0537 0.0340 0.0230 0.0189 0.0162 0.0140 0.0113 0.0102 0.0078 30 mm Error 0.0023 0.0027 0.0032 0.0025 0.0016 0.0011 0.0009 0.0008 0.0006 0.0005 0.0005 0.0004 Error(%) 5.2866 4.8395 5.6666 4.6461 4.8263 4.7669 4.7790 4.7681 4.5872 4.6760 4.6808 4.6236 Appendix Count Efficiency (CE) of MX033U8PP source set (Japan Radioisotope Association) Radioisotope Ce-139 Cr-51 Sr-85 Cs-137 Mn-54 Y-88 Co-57 Cd-109 88 122 136 166 320 514 662 835 898 1173 1333 1836 Y-88 Co-60 Energy (keV) 320 514 662 835 898 1173 1333 1836 logE 2.5053 2.7110 2.8206 2.9216 2.9533 3.0694 3.1247 3.2639 err 0.0268 0.0261 0.0182 0.0193 0.0184 ax+b mm -1.2096 -1.3927 -1.4791 -1.5693 -1.6381 -1.7484 -1.7915 -1.8995 b 1.1427 0.9937 0.8184 0.6651 0.4137 err 0.0240 0.0257 0.0255 0.0254 0.0257 0.0258 0.0260 0.0271 err 0.0785 0.0765 0.0533 0.0565 0.0540 10 mm -1.2694 -1.4511 -1.5332 -1.6100 -1.6866 -1.7859 -1.8237 -1.9420 605 keV -1.4605 -1.5121 -1.6125 -1.6965 -1.8378 err 0.0214 0.0212 0.0212 0.0212 0.0204 0.0212 0.0212 0.0206 err 0.0829 0.0808 0.0563 0.0597 0.0571 logCE 20 mm -1.3771 -1.5516 -1.6416 -1.7114 -1.7759 -1.8669 -1.9125 -2.0377 logCE_cal 662 keV -1.4971 -1.5474 -1.6467 -1.7297 -1.8695 err 0.0829 0.0829 0.0829 0.0829 0.0829 err 0.0210 0.0207 0.0208 0.0207 0.0200 0.0208 0.0208 0.0202 1460 keV -1.8186 -1.8568 -1.9468 -2.0213 -2.1475 30 mm -1.4683 -1.6375 -1.7241 -1.7899 -1.8536 -1.9485 -1.9901 -2.1069 err 0.0829 0.0808 0.0563 0.0597 0.0571 err 0.0210 0.0207 0.0208 0.0207 0.0199 0.0203 0.0203 0.0201 605 keV 0.0346 0.0308 0.0244 0.0201 0.0145 50 mm -1.6087 -1.7918 -1.8634 -1.9337 -1.9915 -2.0738 -2.1224 -2.2200 err 0.0029 0.0025 0.0014 0.0012 0.0008 CE 0.0309 0.0391 0.0387 0.0378 0.0246 0.0161 0.0137 0.0116 0.0102 0.0084 0.0075 0.0060 err 0.0210 0.0208 0.0208 0.0203 0.0200 0.0204 0.0204 0.0201 50 mm Error 0.0016 0.0019 0.0023 0.0017 0.0012 0.0008 0.0007 0.0005 0.0005 0.0004 0.0004 0.0003 CEcal 662 keV err 0.0318 0.0026 0.0284 0.0024 0.0226 0.0019 0.0186 0.0015 0.0135 0.0011 Error(%) 5.2225 4.8482 5.9813 4.5630 4.8319 4.7819 4.7990 4.6851 4.6083 4.6881 4.6949 4.6389 1460 keV 0.0152 0.0139 0.0113 0.0095 0.0071 Appendix Logarithmic of Count Efficiency and Energy MX033U8PP source set (Japan Radioisotope Association) Radioisotope Cr-51 Sr-85 Cs-137 Mn-54 Y-88 Co-60 Y-88 a -0.9358 -0.9008 -0.8739 -0.8489 -0.8094 Appendix Count Efficiency and Thickness of MX033U8PP source set (Japan Radioisotope Association) Thickness (mm) 10 20 30 50 err 0.0013 0.0011 0.0006 0.0006 0.0004 67 ... soil to ears of rice in the paddy fields of the Fukushima after the FDNPP accident has been carried out, the mechanism of the up-taking of cesium into rice, the migration of cesium and the factors... investigate the contamination of radiocesium in rice and paddy field’s soil, the factors that effect to that contamination and the transfer of 137Cs and 134Cs into rice 1.4 Literature review After the. .. migration of radioactive cesium in the rice field In the present study, we investigated the depth dependence of soil in the concentration of radioactive cesium and the concentration of the rice ears in