TOKYO -- The Japanese operator of the Fukushima Daiichi nuclear plant has decided to release treated wastewater from the ruined facility in an area roughly 1 km offshore from the site, Nikkei has learned.

Tokyo Electric Power Co. Holdings will announce the decision Wednesday. The company, also known as TEPCO, is expected to present the plan to Japan's Nuclear Regulation Authority next month for review. But Fukushima Prefecture fishers remain strongly opposed to the discharge, slated to begin in spring 2023.

Since April, when Japan approved TEPCO's plan to release treated wastewater into the ocean, the country's biggest utility has explored discharging the wastewater either along the coast or farther out to sea.

Some experts claimed that releasing farther from the coast would dilute the wastewater faster due to the currents. Innkeepers and other business operators in Fukushima were in favor of discharging in an area beyond eyesight to limit reputational damage.

Before releasing the wastewater, TEPCO plans to remove as much radioactive material as it can, then dilute what remains with at least 100 parts of seawater.

The seawater for dilution will be supplied by waters near the Fukushima plant. Discharging along the coast carries the risk of reusing the wastewater for dilution.

The wastewater will be released through a pipeline yet to be constructed. The pipeline will be contained in a tunnel to be drilled through bedrock within the seafloor. TEPCO begins surveying the ocean floor as early as September.

A similar setup is used at a reprocessing plant for spent nuclear fuel in the Japanese town of Rokkasho in northern Aomori Prefecture. Liquid waste left over from cleaning equipment is treated, tested and released through a pipe into the sea 3 km offshore. A spent fuel reprocessing plant in Britain releases waste from a pipeline roughly 2 km from the coast.