Fukushima Nuclear Accident Radiological Monitoring and Consequences April 1, 2011
Gamma Dose Rates in µSv/hour 14-31 March 1.600 Ibaraki(Mito) 1.400 Saitama(Saitama) 1.200 Tokyo(Shinjyuku) 1.000 0.800 0.600 0.400 0.200 0.000 Natural Background: 0.1 µSv/hour: continue to decrease
Measurements of the IAEA team March, 31- April 1, Fukushima Team1 and 2 • 1 April, FT2 and FT3 altogether as succession process. • 7 different points of radius of 23 to 58 km from the Fukushima NPP • Dose rates: 0.4 to 5 µSv/h • Beta-gamma contamination: 0.01 to 0.49 MBq/m2 • Several gamma spectra, air samples and smears col ected • No alpha particles detected in the air. • 2 April, FT2 back to Tokyo, and then to Vienna March 31, Tokyo team • 31st was the last day for Tokyo-team
Cs-137 deposition (Bq/m2) for 7 prefectures from 25 to 31 March (UTC) 600 500 400 Ibaraki Tochigi(Utsunomiya) Gunma(Maebashi) Saitama(Saitama) 300 Chiba(Ichihara) Bq/m2 Tokyo(Shinjyuku) Kanagawa(Chigasaki) 200 100 0
I-131 deposition (Bq/m2) for 7 prefectures from 25 to 31 March (UTC) 1600 1400 1200 1000 Ibaraki Tochigi(Utsunomiya) Gunma(Maebashi) Saitama(Saitama) 800 Chiba(Ichihara) Bq/m2 Tokyo(Shinjyuku) Kanagawa(Chigasaki) 600 400 200 0
Monitoring of Workers 29 March • Nuclear and Industrial Safety Agency’s report: – 106,095 people in Fukushima – 102 above 100,000 counts per minute (cpm) – Levels decreased after removal of clothes – No cases that may influence health • Among workers at Fukushima NPP: – 20 workers exceeded 100mSv – (Dose limit for emergency workers in life saving operation: 250 mSv)
Monitoring of drinking water 28 March • Recommendations for restrictions on drinking water being lifted in most locations. • Recommendations for restrictions based on I- 131 concentration remain in place in 4 locations of Fukushima prefecture.
Radioactivity in Foodstuffs • Results reported 31 March by the Japanese Ministry of Health, Labour and Welfare • 98 of the 111 samples for various vegetables, fruit, seafood, various meats and unprocessed raw milk • in 8 prefectures (Chiba, Fukushima, Gunma, Ibaraki, Kanagawa, Niigata, Tochigi, and Tokyo), • I-131, Cs-134 and Cs-137 were either not detected or were below the regulation values set by the Japanese authorities.
Radioactivity in Foodstuffs • 13 of the 111 samples: – for spinach and other leafy vegetables, parsley and beef – in Chiba, Fukushima, Ibaraki and Tochigi prefectures indicated that I-131 and/or Cs-134 and Cs-137 exceeded the regulation values set by the Japanese authorities.
Discussion concerning soil • The Japanese Agriculture Ministry has announced on 30 March the need to establish acceptable levels of radioactive Cs in soils to help farmers to decide whether to plant crops. • Fukushima prefecture conducted a survey of soil from farmlands on 31 March.
Joint FAO/IAEA Food Safety Assessment Team • The Joint FAO/IAEA Food Safety Assessment Team has successful y completed its mission. • The team presented its report to the Japanese Cabinet Office, Ministry of Foreign Affairs, Ministry of Health, Labour and Welfare and the Ministry of Agriculture, Fisheries and Forestry on 31 March. • The IAEA members of the Team are returning to Vienna today.
From Bq/kg to Bq/m2 • Soil sample taken with a device that penetrates the ground at the depth of 5 cm • Measurement of radioactivitiy within the sample, using a spectrometer • Result: Radioactivity in Bq/kg • Conversion from Bq/kg to Bq/m2 depends on: – Radioactivity (Bq/kg) – Soil density (kg/m3) – Sample depth (m) Assuming a homogeneous distribution of radioactivity within tha aera considered
Average soil surface Radioactivity in soil contamination Bq/kg Bq/m2 Radioactivity (Bq/kg)x Soil density (kg/m3)x sample depth (m) = Surface contamination (Bq/m2)