P. Bossew, German Federal Office for Radiation Protection, PLUTONIUM EMISSION FROM THE FUKUSHIMA ACCIDENT (pdf), 2013 (emphasis added): [...] Apparently no explosive fuel fragmentation occurred, so that little, if any of the release happened in the form of fuel fragments. […] Only scattered data are available from the farther surroundings. It can be assumed that continuous and frequent monitoring of environmental media for Pu from locations more distant than a few km was deemed unnecessary […] Given two different sources (global and Fukushima fallout) with different, but known 238Pu : 239+240Pu ratios, the contributions of the both in a sample which is a mixture of both can be calculated […] we estimated a median 2.28 (95% conf. interval 1.98 –2.58),  and 2.19 ± 0.48 (1 ), , for Fukushima emissions. […] The background Pu ratio in global fallout has been reported 0.035 ± 0.008 […] a map of the 238Pu : 239+240Pu ratio in the region around the NPP […] The “trace” towards NW from the NPP, in which the Pu ratio deviates strongly from the background […] This proves that indeed Pu has been emitted by the accident […] For 238Pu, the Fukushima contribution is much higher than the global one in many places (as detectable at all) because the Pu ratio is much higher in Fukushima (~2.19) than in global fallout (~0.035). […] Keeping with [the total 137Cs release of] 15 PBq given by NISA […] we find an atmospheric emission of 239+240Pu equal 4.2 GBq. Using the upper estimate of released 137Cs, 50 PBq, a release of 14 GBq is found. [NISA 239+240Pu estimate = 6.4 GBq; Zheng et al. 239+240Pu estimate = 1.0 to 2.4 GBq] […] It should be stressed that the evidence of Pu from Fukushima does not pose any radiological concern [...]
P. Bossew, German Federal Office for Radiation Protection, Hirosaki University, Anthropogenic Radionuclides in Environmental Samples from Fukushima Prefecture (pdf), 2013: Three samples [all taken approx. 60 km from FDNPP, 1 from a parking area in Koriyama city and 2 from a playground in Fukushima city] were measured twice [...] Sample 4 was too small for a meaningful analysis. […] The result found in this study is consistent with a Pu/ Cs ratio reported by Imanaka et al. (2012) for a highly contaminated place in the Fukushima zone as below 1 E-6 [...] Zheng et al. 2011 found 239+240 Pu/137Cs in soil, close to the NPP, as (3.6 ± 1.1) E-7 (only samples with 241Pu>0 considered, and Fukushima contribution 87% to the sample J-village, surface soil , as suggested by the authors), which is in good agreement with the results of this study.
See also: Scientists: Plutonium released from Fukushima "is of radiological concern"; Reactor must be source, not spent fuel pool -- Study: Plutonium found 120 km from plant; "Pu and non-natural uranium certainly increased in environment"
Published: June 29th, 2014 at 2:57 am ET
- New Studies on Mystery ‘Black Substances’ Released: Fuel core materials from Fukushima plant detected — Plutonium, Uranium-236, Curium discharged into environment likely in form of fine particles (PHOTO) March 7, 2014
- Study: High plutonium-241 activity detected over 30 kilometers from Fukushima plant — Additional research suggests “long-distance transport” of plutonium October 8, 2013
- Scientists: Plutonium released from Fukushima “is of radiological concern”; Reactor must be source, not spent fuel pool — Study: Plutonium found 120 km from plant; “Pu and non-natural uranium certainly increased in environment” April 21, 2014
- Just-Published Study: Plutonium being found away from Fukushima is from nuclear fuel fragments blown out after explosions March 9, 2012
- VIDEO: Fukushima corium found in Pacific — Flowing into ocean after hydrogen dissolves nuclear fuel — Scientist: We’ve actually seen plutonium floating on surface; “We have no control over this accident… they’ve got leaks everywhere” January 2, 2015