Dispersal of Spent Fuel -Reply -Reply

[Charles Willis <CAW@nrc.gov>]

If someone blew up a spent fuel assembly that had been out of the core for a year or more, the
release of radioactive material would be negligible in terms of the resulting inhalation doses
and immersion doses because the volitile nuclides would have been largely eliminated by
radioactive decay. The krypton-85 would be released but it is relatively innocuous. Iodine-129
would be expected to escape to some degree but there isn't much I-129 activity present.  So
far as I know, there have been no actual measuremnts of this sort of event so all we have is
engineering judgement based on knowledge of half lives, vapor pressures, fission yields, other
fission product release measurements, etc.

If the explosive were energetic enough, and properly positioned, the fuel assembly could be
broken into small pieces and scattered over a large area.  If the area were in a city, quite a
number of overexposures, radiation "burns," and even lethal doses would be possible.  This
could be ameliorated if the local police used radiation instruments properly, but I am not sure
this would be the case.  Of course, if the detonation were staged in an unpopulated area, the
result would be a contamination problem (minor compared to what we once considered routine
at Jackass Flats) and a great political/public relations problems. Presumably the PR problem
would have been the purpose of the act since there are much easier ways to hurt people.

We also could have some very seriously irradiated terrorists, but most of us would not deem
that a tragedy.