Apparently the concern is seismic (if I understood what I just read here:
http://seekerblog.com/2011/05/01/nisa-instructs-tepco-to-study-demonstrate-dry-well-flooding-is-safe-from-seismic/
They’ve had a few days so perhaps NISA and TEPCO have decided that it is seismically safe? Seems like their seismic concern has to do with going forward - drywell filled with water and then large aftershock hits?
http://seekerblog.com/2011/05/01/nisa-instructs-tepco-to-study-demonstrate-dry-well-flooding-is-safe-from-seismic/
“They’ve had a few days so perhaps NISA and TEPCO have decided that it is seismically safe? Seems like their seismic concern has to do with going forward - drywell filled with water and then large aftershock hits?”
It reads like they peformed the seismic analysis to ensure the integrity of the drywell if an earthqualke occurs while it is flooded.