“Unequivocal” Criticality continues at Fukushima
April 29, 2011
Data released on April 28, 2011 by TEPCO is now unequivocal in showing ongoing criticalities at Unit 2, with a peak on April 13. TEPCO graphs of radioactivity-versus-time in water under each of the six reactors show an ongoing nuclear chain reaction creating high levels of “fresh” I-131 in Unit 2, the same reactor pressure vessel (RPV) with a leak path to reactor floor, aux building, and outdoor trenches, that is uncontrollably leaking high levels of I-131, Cs-134, Cs-137 into the Pacific Ocean.
Because I-131 has no long-lived “parent” to “feed it” by parent decay, the levels of I-131 in scrammed reactors with intact geometry will decrease exponentially with an 8-day halflife, meaning that after 5 halflives (40 days) the I-131 levels are only 3% of what they were at scram.
But instead of seeing that expected decrease in I-131 levels relative to Cs-134 and Cs-137 in the regular TEPCO press releases, I-131 was seen to be increasing, instead of decreasing as the physics said it should.
“Outlier” Unit 2 has I-131 levels roughly 20 times its levels of Cs-134/137. The only possible source of I-131 would be “pockets” of molten core in the Unit 2 RPV settled in such a way that the boron in the injected water is insufficient to stop the localized criticalities.