Three years after it was devastated by monster tsunami, the Fukushima No. 1 nuclear plant continues to be plagued by numerous problems as it lurches through the decades-long process toward decommissioning.

The most troubling problem is dealing with the buildup of radioactive water, which is increasing at a rate of 400 tons in the reactor buildings every day, and another 400 tons of lightly contaminated water that seeps daily into the Pacific.

Experts say Tokyo Electric Power Co. and the government will be wrestling with these problems, and the task of removing the highly toxic contaminants from the water, for years and maybe decades, but at least it has become clearer what measures will need to be implemented thanks to simulations of the groundwater flow.