About 400 tons of groundwater flow into the site each day, and TEPCO also pumps large amounts of water through the buildings to keep the crippled reactors cool.
The Japanese government has pledged to come up with emergency measures to tackle the growing toxic water problem.
"A package of comprehensive countermeasures" will be presented at a ministerial meeting headed by the prime minister on Tuesday, the local news agency Kyodo reported Monday.
Dump it in the ocean?
One approach flagged by experts to deal with the massive volume of toxic water at the plant is to dump some or all of it into the Pacific Ocean.
"We might have to consider the option of discharging tainted water that is below regulatory levels into the ocean," Tanaka said Monday.
But he stressed that he would not allow the discharge of "tainted water that is above accepted levels."
Tanaka also warned that the toxic water is not the only big challenge at the site -- there's also the decommissioning of the reactors, which is likely to take 30 to 40 years.
"We have a long road ahead of us," he said.