Three of the spent fuel assemblies due to be carefully plucked from the crippled Japanese nuclear plant at Fukushima in a hazardous year-long operation were damaged even before the 2011 earthquake and tsunami that knocked out the facility.
The plant's operator, Tokyo Electric Power Co, or Tepco, said the damaged assemblies - 4.5 meter high racks containing 50-70 thin rods of highly irradiated used fuel - can't be removed from Fukushima's Reactor No. 4 using the large cask assigned to taking out more than 1,500 of the assemblies.
Tepco is due within days to begin removing 400 tones of the dangerous spent fuel in a hugely delicate and unprecedented operation fraught with risk.
Having to deal with the damaged assemblies is likely to make that task more difficult and could jeopardize a 12-month timeframe to complete the removal that many have already called ambitious.