The Japanese administration is considering keeping the enormous and still growing volume of radioactively contaminated water at the disaster-stricken Fukushima Daiichi nuclear plant in storage tanks for the long term, a source close to the government has told the Mainichi Shimbun.

Previously, five options to deal with the contaminated water were being compared: releasing it into the ocean; piping it into a deep stratum of the Earth's crust; releasing it into the atmosphere as steam; encasing it in cement and burying it; and using electrolysis to hydrogenate tritium -- a relatively low-impact radioactive element not filtered out with plant operator Tokyo Electric Power Co. (TEPCO)'s current decontamination systems -- in the water before releasing it into the air.

However, strontium 90 -- a radioactive element that can accumulate in the bones -- was discovered in treated water in government maximum-busting concentrations just before August 2018 public hearings on the contaminated water problem. The revelation "completely destroyed the premise for discussions," the Mainichi source said, and public worries about releasing the water into the environment prompted the government to reconsider.

As a result, a Ministry of Economy, Trade and Industry expert committee on the contaminated water issue set to meet in June will add long-term tank storage to the existing five options.

According to the government source, the administration will take the expert committee's opinions into account when it makes a final decision on the water problem. However, views in the prime minister's office are apparently split. Furthermore, the government is worried that taking any decision ahead of the 2020 Tokyo Games could invite increased attention on the problem and risks the spread of harmful rumors, making it very difficult to project which method will be chosen.

Any of the options is expected to take about two years to implement, a senior industry ministry official said.

Meanwhile, Nuclear Regulation Authority (NRA) Chairman Toyoshi Fuketa warned at a March news conference that "the time when a decision must be made (on how to deal with the contaminated water) is very close indeed."

There is already over 1 million metric tons of contaminated water stored on-site at the Fukushima Daiichi plant, while existing plans will see total capacity max out at 1.37 million tons in 2020. At the current rate of increase, all the 10-meter-tall tanks will be full in four to five years. It is thought that the government will look into processing the water in small quantities as the total volume nears capacity, beginning with the most lightly contaminated.

However, "from a scientific and technical standpoint, the only choice is to dilute it and release it into the ocean," Fuketa said at the March news conference. The industry ministry's panel of experts has released figures showing this is also the fastest and lowest-cost option.

The water volume continues to increase due to ground water flowing into the fractured reactor buildings, and the need to keep pumping more water into the shattered reactor cores to cool the nuclear fuel debris inside. Just after the March 2011 triple-meltdown at the plant triggered by the Great East Japan Earthquake and tsunami, the amount of groundwater flowing into the reactor buildings was around 400 tons daily. A subterranean ice wall and other measures have cut this by about half, but eliminating it entirely is impossible.

It is expected to take until 2051 to finish decommissioning the Fukushima Daiichi plant, including processing the contaminated water.

(Japanese original by Toshiyuki Suzuki and Riki Iwama, Science &Environment News Department, and Tatsushi Inui, Iwaki Local Bureau)