Explainer-Wall of ice at Fukushima's crippled nuclear plant

FILE PHOTO: Employees of Tokyo Electric Power Co's (TEPCO) are seen next to the part of an underground ice wall unit, to prevent underground water from flowing in and stop radioactive water seeping into the Pacific Ocean, at tsunami-crippled Fukushima Daiichi nuclear power plant in Okuma town, Fukushima prefecture, Japan February 18, 2019. REUTERS/Issei Kato

The operator of Japan's crippled Fukushima nuclear power plant said this month that two storage tanks had leaked about four tonnes of coolant solution used to create an ice wall that prevented groundwater from seeping in.

The operator, Tokyo Electric Power Co Holdings (Tepco), said the leak had no impact on the wall or the environment, however.