Blast from the past

Stumbled on this interesting photo from 1965- this was the KIWI TNT
(Transient nuclear Test) test; a KIWI nuclear rocket test reactor was
purposely given a runaway nuclear reaction to see what its failure would
result in: http://www.wps.com/archives/wxvax7.e...ages/ktntb.gif
Note the railway tracks for scale, and the flying sparkling stuff- which
given that uranium is pyrophoric, I assume are the uranium pellets from
the reactor's fuel elements.
Aren't these things supposed to melt down? This looks like an SRB
exploding.
How would you like to have been sitting on top of that when it
malfunctioned?
I'll bet this was one fun clean-up job.

Pat