Bringing the reactors at the plant under control will require permanently restoring cooling systems knocked out by the tsunami that prevent reactors from dangerously overheating. That task has been complicated by dangerous conditions at the plant that have often forced workers to stop what they are doing.
Meantime, crews at the nuclear facility are waiting to see if a second attempt to stop radioactive water from gushing into the Pacific Ocean is going to work.
Official noticed Saturday that a concrete-lined basin behind the plant had a nearly 8-inch crack.
Fresh concrete was initially used to fill the crack, but that didn't work. So, crews tried a synthetic compound earlier Sunday.
Also, the crippled complex has caused a power crunch in Tokyo. Officials are now concerned the strain will affect air conditioning during the summer.
The nuclear crisis has compounded the suffering of people in the northeast and, at times, overshadowed their plight. Tens of thousands have lost their homes and are living in shelters, 200,000 households do not have water, and 170,000 do not have electricity.
A focused effort to find bodies of tsunami victims was scheduled to end on Sunday. The joint mission between U.S. and Japanese military forces concentrated on areas that were submerged for the past few weeks, as well as the mouths of major rivers.
Since the earthquake and tsunami hit on March 11, 12,000 deaths have been confirmed and more than 15,000 people are still missing.
The Associated Press contributed to this story