title: Utilization of (134)Cs/(137)Cs in the environment to identify the reactor units that caused atmospheric releases during the Fukushima Daiichi accident.
abstract: The Fukushima Daiichi nuclear power reactor units that generated large amounts of airborne discharges during the period of March 12-21, 2011 were identified individually by analyzing the combination of measured (134)Cs/(137)Cs depositions on ground surfaces and atmospheric transport and deposition simulations. Because the values of (134)Cs/(137)Cs are different in reactor units owing to fuel burnup differences, the (134)Cs/(137)Cs ratio measured in the environment was used to determine which reactor unit ultimately contaminated a specific area. Atmospheric dispersion model simulations were used for predicting specific areas contaminated by each dominant release. Finally, by comparing the results from both sources, the specific reactor units that yielded the most dominant atmospheric release quantities could be determined. The major source reactor units were Unit 1 in the afternoon of March 12, 2011, Unit 2 during the period from the late night of March 14 to the morning of March 15, 2011. These results corresponded to those assumed in our previous source term estimation studies. Furthermore, new findings suggested that the major source reactors from the evening of March 15, 2011 were Units 2 and 3 and that the dominant source reactor on March 20, 2011 temporally changed from Unit 3 to Unit 2.
authors.affiliation: Sector of Nuclear Science Research, Japan Atomic Energy Agency, 2-4 Shirakata, Tokai-mura, Naka-gun, Ibaraki 319-1195, Japan.
authors.forename: Masamichi
authors.initials: M
authors.lastname: Chino
authors.affiliation: Sector of Nuclear Science Research, Japan Atomic Energy Agency, 2-4 Shirakata, Tokai-mura, Naka-gun, Ibaraki 319-1195, Japan.
authors.forename: Hiroaki
authors.initials: H
authors.lastname: Terada
authors.affiliation: Sector of Nuclear Science Research, Japan Atomic Energy Agency, 2-4 Shirakata, Tokai-mura, Naka-gun, Ibaraki 319-1195, Japan.
authors.forename: Haruyasu
authors.initials: H
authors.lastname: Nagai
authors.affiliation: Sector of Nuclear Science Research, Japan Atomic Energy Agency, 2-4 Shirakata, Tokai-mura, Naka-gun, Ibaraki 319-1195, Japan.
authors.forename: Genki
authors.initials: G
authors.lastname: Katata
authors.affiliation: Sector of Fukushima Research and Development, Japan Atomic Energy Agency, 7-1 Taira Omachi, Iwaki, Fukushima 970-8026, Japan.
authors.forename: Satoshi
authors.initials: S
authors.lastname: Mikami
authors.affiliation: Sector of Fukushima Research and Development, Japan Atomic Energy Agency, 7-1 Taira Omachi, Iwaki, Fukushima 970-8026, Japan.
authors.forename: Tatsuo
authors.initials: T
authors.lastname: Torii
authors.affiliation: Sector of Fukushima Research and Development, Japan Atomic Energy Agency, 2-2-2 Uchisaiwai-cho, Chiyoda-ku, Tokyo, 100-8577, Japan.
authors.forename: Kimiaki
authors.initials: K
authors.lastname: Saito
authors.affiliation: Sector of Fukushima Research and Development, Japan Atomic Energy Agency, 45-169 Harama-chiku Kaibama sukakeba, Minamisoma City, Fukushima 975-0036, Japan.
authors.forename: Yukiyasu
authors.initials: Y
authors.lastname: Nishizawa
mesh_terms: D000396:Air Pollutants, Radioactive / Q000032:analysis*; D002588:Cesium Radioisotopes / Q000032:analysis*; D003198:Computer Simulation; D062406:Fukushima Nuclear Accident; D007564:Japan; D011834:Radiation Monitoring; D014875:Water Pollutants, Radioactive / Q000032:analysis*
chemical_list: D000396:Air Pollutants, Radioactive; D002588:Cesium Radioisotopes; D014875:Water Pollutants, Radioactive