Re:TMI releases

[Jacques.Read@eh.doe.gov]

There is actually no direct evidence that any radioiodine escaped from the TMI
containment. (One grass sample from a rural roadside had a few counts, but may
have been spurious, or the result of a medical testee's al fresco urination
while driving home from the hospital, since there was nothing else anywhere
near.)  Any that did escape would have evolved from solutions in the auxilliary
building as methyl iodide.  To attempt to estimate the iodine off-site from a
xenon measurement is less than hopeless ......  if you get the raw data and
back-calculate it becomes apparent that the xenon off-site did not leak from the
containment, but rather  is the daughter activity of iodate dissolved in the
sump solutions in the aux. building.  Much later, when the containment was
vented, krypton-85 was deliberately released, but by then all the xenon isotopes
were history.

There are several other very interesting radiochemical scenarios at TMI --  you
can, for example easily convince yourself by back-calculations that the lye
injections led to hydroxide precipation in the sump with the hydroxide being
tritiated to the isotope ratio of the coolant during the melt-down.  In the
weeks following the accident, the sump samples slowly increase in tritium as the
the hydroxide re-equilibrates with the additional collant injections and
let-downs.  There's also evidence in the time-histories of the iodine isotope
ratios that at early times a lot of the iodine was AgI precipitated by the
silver dissolved from the control rods.



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