After 5 Halflives, I-131 Higher than Cs-134/137 Suggests Ongoing Criticalities, Gerson Lehrman Group, April 19, 2011:
… Japanese regulators NISA and MEXT seem oblivious of the mysterious fact that I-131 Bq “reactor density” is still often reported double the Cs-134/137 Bq. The TEPCO data suggest that fission is ongoing despite the reactor shutdowns. This is bad news. …
Everyone with just a very basic understanding of reactor safety should know that once a reactor is scrammed, U-235 is no longer fissioning, and I-131 has no parent which can be decaying to create it in an ongoing process… the water circulating in intact SNF pools should have absolutely no detectable I-131 in them. …
[I]t has been almost five full 8-day halflives for their I-131 to decay to stable xenon. At t=0, as we say, the Bq of I-131 and Cs-134 and Cs-137 would all be approximately equal, but, after five I-131 halflives, the “reactor density” radioactivity of I-131 should be only 1/2**5=~3% of what it was originally. Go look at all the data of relative radioactivity that TEPCO is reporting with dates of April 19, 2011 and you’ll see that instead of I-131 being below the levels of the two cesiums, I-131 is often twice as high as the two cesiums always reported.
The fact that nobody in Japan seems to know basics of reactor accident progression that I learned at Sandia Labs in early 1980s is truly scary, because it suggests they are playing with these broken/leaking reactors and SNF pools inside at least three buildings totally destroyed by steam explosions … as if the reactors and their SNF pools are broken toys that they’re using trial and error to try fixing.
Read the report here.
Published: April 21st, 2011 at 7:15 pm ET