Radioactive Iodine (I‐131) (The Tokyo Metropolis and 12 Prefectures)
Radiation Monitoring Radioactive Iodine (I‐131) of Clean Water (the Tokyo Metropolis and 12 Prefectures)
110 Bq/kg in Tochigi Prefecture on March 24
Morioka City, Iwate
Akita City, Akita
Yamagata City, Yamagata
Hitachinaka City, Ibaraki
Utsunomiya City, Tochigi Maebashi City, Gunma
Saitama City, Saitama
Ichihara City, Chiba
Shinjuku Ward, Tokyo Chigasaki City, Kanagawa
Niigata City, Niigata Kofu City, Yamanashi Shizuoka City, Shizuoka Radiation Monitoring of Clean Water 7.6 Radioactive Iodine (I‐131) in Tap Water⽔道⽔中の放射性ヨウ素（I-131）
Bq/kg: becquerels per kilogram * In the figure above, values below the detection lower limit are treated as 0 for convenience. * Only prefectures where radioactive iodine was detected in the measurement are indicated in the figure. Interim Report on Measures for Radioactive Materials in Tap Water Prepared based on the reference material for the Ministry of Health, Labour and Welfare (MHLW)'s Study Meeting on Measures for Radioactive Materials in Tap Water (June 2011)
As a result of the inspection of radioactive materials in tap water conducted by the Ministry of Education, Culture, Sports, Science and Technology (MEXT), radioactive iodine was detected in the Tokyo Metropolis and 12 prefectures out of 47 prefectures nationwide. Highest concentrations were detected at the respective locations from March 18 to 29, 2011, but I-131 concentrations turned to decrease in many locations in the latter half of March 2011. In and after April 2011, only small amounts of I-131 were detected at some of these locations.
Included in this reference material on March 31, 2013 Updated on January 18, 2016
25 Radiation Monitoring Radioactive Cesium (Cs‐134 + Cs‐137) of Clean Water (the Tokyo Metropolis and 7 Prefectures)
18 Bq/kg in Ibaraki Prefecture on March 21
Morioka City, Iwate
Yamagata City, Yamagata
Hitachinaka City, Ibaraki
Utsunomiya City, Tochigi
Maebashi City, Gunma
Saitama City, Saitama
Ichihara City, Chiba
Shinjuku Ward, Tokyo Radiation Monitoring of Clean Water 7.6
Radioactive Cesium (Cs‐134 + Cs‐137) in Tap Water⽔道⽔中の放射性セシウム（Cs-134 +Cs-137） * In the figure above, values below the detection lower limit are treated as 0 for convenience. Bq/kg:becquerels per kilogram * Only prefectures where radioactive cesium was detected in the measurement are indicated in the figure. * ● is marked on dates when the readings were ND (not detected; below the detection lower limit). Interim Report on Measures for Radioactive Materials in Tap Water Prepared based on the reference material for the Ministry of Health, Labour and Welfare (MHLW)'s Study Meeting on Measures for Radioactive Materials in Tap Water (June 2011)
As a result of the inspection of radioactive materials in tap water conducted by the Ministry of Education, Culture, Sports, Science and Technology (MEXT), radioactive cesium was detected in the Tokyo Metropolis and 7 prefectures out of 47 prefectures nationwide. Highest concentrations were detected at the respective locations from March 20 to early April 2011, but radioactive cesium concentrations were relatively smaller than radioactive iodine concentrations. In and after April 2011, only small amounts of radioactive cesium were detected at some of these locations.
Included in this reference material on March 31, 2013 Updated on January 18, 2016
26 Radiation Monitoring of Results of Long‐term Radiation Monitoring of Clean Water Tap Water
110 100 岩⼿県盛岡市Morioka City, Iwate 秋⽥県秋⽥市Akita City, Akita 90 ⼭形県⼭形市Yamagata City, Yamagata 茨城県ひたちなか市Hitachinaka City, Ibaraki 80 Utsunomiya City, Tochigi 70 栃⽊県宇都宮市 群⾺県前橋市Maebashi City, Gunma 60 埼⽟県さいたま市Saitama City, Saitama 千葉県市原市Ichihara City, Chiba 50 東京都新宿区Shinjuku Ward, Tokyo 神奈川県茅ヶ崎市Chigasaki City, Kanagawa (Bq/kg) 40 新潟県新潟市Niigata City, Niigata ⼭梨県甲府市Kofu City, Yamanashi 30 静岡県静岡市Shizuoka City, Shizuoka 20 10 0 1/6 4/1 4/8 5/6 6/3 7/1 7/8 8/5 9/2 9/9 1/13 3/18 3/25 4/15 4/22 4/29 5/13 5/20 5/27 6/10 6/17 6/24 7/15 7/22 7/29 8/12 8/19 8/26 9/16 9/23 9/30 10/7 11/4 12/2 12/9 10/14 10/21 10/28 11/11 11/18 11/25 12/16 12/23 12/30 Radioactive Iodine (I‐131) in Tap Water
20 18 16 岩⼿県盛岡市Morioka City, Iwate ⼭形県⼭形市Yamagata City, Yamagata 14 茨城県ひたちなか市Hitachinaka City, Ibaraki 栃⽊県宇都宮市Utsunomiya City, Tochigi 12 群⾺県前橋市Maebashi City, Gunma 埼⽟県さいたま市Saitama City, Saitama 10 千葉県市原市Ichihara City, Chiba 東京都新宿区Shinjuku Ward, Tokyo (Bq/kg) 8 6 4 2 Radiation Monitoring of Clean Water 7.6 0 1/6 4/1 4/8 5/6 6/3 7/1 7/8 8/5 9/2 9/9 1/13 3/18 3/25 4/15 4/22 4/29 5/13 5/20 5/27 6/10 6/17 6/24 7/15 7/22 7/29 8/12 8/19 8/26 9/16 9/23 9/30 10/7 11/4 12/2 12/9 10/14 10/21 10/28 11/11 11/18 11/25 12/16 12/23 12/30 Radioactive Cesium (Cs‐134 + Cs‐137) in Tap Water
Committee on Living Environment and Water Supply in March 2012
The long-term tap water monitoring showed that radioactive cesium has seldom been detected since May 2011, not to mention short-half-life radioactive iodine.
Included in this reference material on March 31, 2013
27 Radiation Monitoring of Clean Water Inspections by Water Suppliers
Changes in Number of Specimens for Radioactive Cesium Inspection (specimens) Detection of Radioactive Cesium (Purified Water) (Bq/kg) (Note) Number of cases where radioactive cesium Purified Raw 浄⽔ 原⽔ 180 detection was reported (specimens) water water 165 Number of specimens with either showing a ≦ 8000 ⽚⽅がvalue over 1 and the total being 10 or less>1、合計が 10の検出検体数 160 7176 合計がNumber of specimens with the total being >10の検出検体数 over 10 7000 6812 6680 6670 6666 6753 6441 6573 6418 140 140.5 最⾼濃度Maximum concentration (Cs‐134+Cs‐137)Cs-134+Cs-137134Cs+137Cs（Bq/kg） 6101 6000 120
5000 100 130 83 4000 80 68.8 3000 2603 60 67 2000 40 29 1000 20 19 35 6.1 3.1 3 212 133 148 165 158 158 186 168 173 16 13 1.5 119 127 110.5 1 0.4 0 0 0 6 6 Radiation Monitoring of Clean Water 7.6
Bq/kg: becquerels per kilogram 12th Health Sciences Council's Committee on Living Environment and Water Supply in March 2012
Water suppliers conduct inspections of radioactive cesium for approx. 6,000 to 7,000 specimens of purified water and over 100 specimens of raw water per month. The maximum monthly value of radioactive cesium concentration was 140.5 Bq/kg detected in March 2011, but the value declined gradually thereafter and there has been no report of radioactive cesium detection at a level exceeding 10 Bq/kg since June 2011.
Included in this reference material on March 31, 2013
28 Radiation Monitoring of Clean Water Behavior of Radioactive Cesium
Conceptual Diagram of Behavior of Radioactive Cesium Environmental Water Tap water Air water purification (mainly river water)
Cs I May cesium iodide, gaseous cesium, etc. Cs Cs be contained?
Cs Cs Mote Removal Mote (coagulating sedimentation, filtering) ＋ ＋ Particulate cesium Cs Partial removal Cs Cesium ion (adsorption, coagulating sedimentation, filtering)
Cesium may exist in such forms as particulate Radiation Monitoring of Clean Water 7.6 cesium or Cs+ (cation) in environmental water. Generally, cations are easily adsorbed by ＋ adsorptive suspensoids with exchange capacity. I Iodine Cs Cesium ion
Prepared based on the reference material for the 12th Health Sciences Council's Committee on Living Environment and Water Supply in March 2012
Radioactive cesium discharged due to the accident at Tokyo Electric Power Company (TEPCO)'s Fukushima Daiichi NPS consists of Cs-134 and Cs-137 in equal proportion (1:1) and has also been detected at the same rate in the environment. Radioactive cesium was in the form of particles or gas immediately after discharge from the NPS, but it is considered to have fallen down onto the ground surface and to have been adsorbed into soil and particles, etc. In water, radioactive cesium is adsorbed into particles and tends to behave in the same manner as soil or other suspensoids, and therefore, is highly likely to be reduced by removing suspensoids in water.
Included in this reference material on March 31, 2013 Updated on January 18, 2016
29 Radiation Monitoring of Clean Water Control of Radioactive Cesium
Most of the radioactive cesium that reaches sources of tap water is adsorbed into suspensoids such as soil and flows out. Therefore, radioactive cesium can be controlled through strict turbidity management. Example of Behavior of Radioactive Cesium (Cs‐134 and Cs‐137) a浄⽔場における放射性セシウム(134Cs、137Cs)の挙動例t Water Purification Plant
National Institute of Public Health (Kosaka, et al., Journal of国立保健医療科学院（投稿中データ） Japan Water Works Association, 2014)
Cs-137 Cs-134
Radioactive cesium (Bq/L) Radioactive <0.83 <0.59 <0.76 <0.67 <0.58 <0.50 <1.0 <0.47 <0.58 <0.57 Radiation Monitoring of Clean Water 7.6 Water after Biological activated Raw water sedimentation carbon treated water Rapid filtered water Zeolite, ion exchangers, nanofiltration membranes and reverse osmosis membranes are professionally used for removing radioactive materials, but these cannot be used for ordinary water purification due to high cost, required facilities and inefficiency (in particular, the use of nanofiltration membranes and reverse osmosis membranes is power consuming). Bq/L: becquerels per liter 12th Health Sciences Council's Committee on Living Environment and Water Supply in March 2012
As of April 2011, radioactive cesium concentrations in raw water, water after sedimentation, biological activated carbon treated water, and rapid filtered water were measured at water purification plants in Fukushima Prefecture. As a result, it was confirmed that low- concentrated radioactive cesium detected in raw water had decreased through adsorption into soil in the process of sedimentation. A survey of water purification processes revealed that radioactive cesium had been almost entirely removed together with suspensoids through coagulating sedimentation, sand filtration and the use of powdered activated carbon. At present, radioactive cesium is not detected in almost all purified water. These results showed that radioactive cesium can be controlled through strict turbidity management.
Included in this reference material on March 31, 2013
30 Radiation Monitoring of Clean Water Waterworks System
Changes in Radioactive Cesium Concentrations at Water Purification Plants in Fukushima Prefecture as of April 28, 2011 １ Intake tower (raw water) National Institute of Public Health Sampling Sedimentation pond (water after ８ sedimentation) points Distributing reservoir (rapid 12 filtered water)
General purification system (rapid filtration) Below quantitation limit Cs-137 <0.58 Approx. 12 Bq/L Cs-134 <0.57 (Cs‐134 + Cs‐137)
５ ６ ９ ７ ４ 10 13 ３ ８ 11 12 １ ２ Below quantitation limit
Cs-137 <0.59 Radiation Monitoring of Clean Water 7.6 Cs-134 <1.0
① Intake tower ② Sand basin ③ Intake pump ④ Receiving well ⑤ Flocculant injection facility ⑥ Chemical mixing basin ⑦ Floc forming basin ⑧ Sedimentation pond ⑨､⑪ Chlorine injection facility ⑩ Filter basin ⑫ Distributing reservoir ⑬ Water pump Bq/L: becquerels per liter Prepared based on the reference material for the 12th Health Sciences Council's Committee on Living Environment and Water Supply in March 2012
This figure shows the rapid filtration method, which is generally used in Japan. In this method, chemicals are injected into raw water taken from a river or dam to cause sedimentation of mud and small particles and make them into big chunks called "floc." Tap water is created by filtering the clear upper portion of such water. Cesium has the property to be easily adsorbed into soil and mud (p.29 of Vol. 2, "Behavior of Radioactive Cesium"). Therefore, when water is separated from floc, cesium tends to gather around the floc, which is a chunk of soil and mud. Additionally, tap water is created using the clear upper portion of the water in plant basins. Therefore, this mechanism leaves little chance for cesium to be mixed into tap water. In the pattern diagram above, radioactive cesium concentrations (Bq/L) actually measured at a water purification plant in Fukushima Prefecture as of April 28, 2011, are indicated at points where measurement was conducted. Radioactive cesium concentration, which was initially approx. 12 Bq/L at the intake tower, decreased to below the quantitation limit in the end when being pumped out from the distribution reservoir. It can be found that the concentration was far below 200 Bq/kg, which was the allowable limit for radioactive cesium in tap water publicized by the Ministry of Health, Labour and Welfare (MHLW) in March 2011, and also far below 10Bq/L, which is specified in the new standards for radioactive materials in tap water publicized in March 2012 (p.43 of Vol. 2, "Standard Limits Applied from April 2012").
Included in this reference material on March 31, 2015 Updated on February 28, 2018
31