https://www.lmtonline.com/news/article/Storage-capacity-of-radioactive-water-at-12928397.php
Water volume increasing
At the Fukushima No. 1 nuclear plant, groundwater and other water enters the reactor buildings that suffered meltdowns, where the water becomes contaminated. This produces about 160 tons of contaminated water per day. Purification devices remove many of the radioactive materials, but tritium — a radioactive isotope of hydrogen — cannot be removed for technical reasons. Thus, treated water that includes only tritium continues to increase.
Currently, the storage tanks have a capacity of about 1.13 million tons. About 1.07 million tons of that capacity is now in use, of which about 80 percent is for such treated water.
Space for tanks, which has been made by razing forests and other means, amounts to about 230,000 square meters – equivalent to almost 32 soccer fields. There is almost no more available vacant space.