Research conducted in Japan by scientists monitoring Fukushima atmospheric emissions documented a large spike in radiation emissions in the fall of 2011. During this time TEPCO announced that they measured fission at the plant. Radnet Beta chart measurements in the US cities under the jet stream also spiked substantially during this time.
Emissions events such as those that occurred in the fall of 2011 have NOT been included in the calculations for total atmospheric emissions from Fukushima.
SOURCE Sheng Xu, Stewart P. H. T. Freeman, Xiaolin Hou, Akira Watanabe, Katsuhiko Yamaguchi, and Luyuan Zhang (2013) Iodine Isotopes in Precipitation: Temporal Responses to 129I Emissions from the Fukushima Nuclear Accident. Environmental Science and Technology, 47, 10851-1085
Four periods of change in 129I concentration after the accident can be observed in Figure 2; these are summarized in Table 2.
• PERIOD I: In Period I, the 129I concentration increased dramatically from background level to the maximal value of 8 × 1011 atoms/L in the sample collected in March 2011 by a factor of about 4 orders of magnitude. Following the termination of radionuclide emission from the damaged reactors, 129I concentration in the atmosphere started to decline exponentially until October 2011.
• PERIOD II: The onset of Period II is characterized by an interruption of the previously decreasing 129I trend, with elevated 129I levels occurring around November−December 2011. This is followed by an exponential decrease that continued until March 2012.
• PERIOD III AND IV: Periods III and IV have patterns similar to Period II, with elevations in 129I levels starting around April 2012 and September 2012, respectively. In both cases, the elevated 129I subsequently declined exponentially.
NOV 2011 TEPCO REPORTS NUCLEAR FISSION
Tsuyoshi Inajima and Yuji Okada (2011, November 2) Tepco Detects Nuclear Fission at Damaged Fukushima Power Station. Business Week, http://www.businessweek.com/news/2011-11-01/tepco-detects-possible-nuclear-fission-at-fukushima-reactor.html
Nov. 2 (Bloomberg) -- Tokyo Electric Power Co. detected signs of nuclear fission at its crippled Fukushima atomic power plant in northern Japan, raising the risk of more radiation leaks. The situation is under control, officials said. The company, known as Tepco, began spraying boric acid on the No. 2 reactor at 2:48 a.m. Japan time to prevent accidental chain reactions. Tepco said it may have found xenon, which is associated with nuclear fission, while examining gases taken from the reactor, according to an e-mailed statement today.
RADNET READINGS SPIKE IN THE US AT LEVELS WE'VE NOT SEEN BEFORE OR SINCE. Levels drop off end of January 2012: