A visiting team of IAEA experts said Japan should weigh the possibility of discharging part of the growing stockpile of contaminated water at the crippled Fukushima nuclear power plant to the sea.

Its recommendation came with the caveat that radioactive levels would have to be below safety standards.

“It is necessary to find a sustainable solution to the problem of managing contaminated water at Tokyo Electric Power Co.’s Fukushima No. 1 nuclear power station,” the International Atomic Energy Agency team said in its preliminary summary report released Dec. 4. “This would require considering all options, including the possible resumption of controlled discharges to the sea.”

At the Fukushima No. 1 plant, the stockpile of radioactive water is growing by 400 tons every day as groundwater flowing into reactor and turbine buildings keeps adding to and mixing with water used to cool melted nuclear fuel. TEPCO is using an Advanced Liquid Processing System (ALPS), a purifier touted as capable of removing 62 types of radioactive substances, to treat the contaminated water.

But that does not help reduce the total amount of water that needs to be managed, because the ALPS cannot remove tritium, a radioactive isotope of hydrogen.

TEPCO said it was holding 390,000 tons of radioactive water in storage tanks as of Dec. 3, including 31,000 tons that have been treated with the ALPS.

Juan Carlos Lentijo, leader of the IAEA expert team, held a news conference in Tokyo on Dec. 4, where he said controlled discharges of contaminated water are a common practice around the world. He added that TEPCO should gather data on treated water for safety screenings by Japan’s Nuclear Regulation Authority, and release the water to the sea if it is found to have cleared regulation standards.

Lentijo, at the same time, emphasized the importance of gaining understanding from the general public and the parties involved, and said controlled discharges should be allowed to take place only after discussions are held with relevant stakeholders and their approval is obtained.

The 19-member team of IAEA experts was visiting Japan from Nov. 25 to review Japan’s effort to decommission the devastated Fukushima plant, including the removal of nuclear fuel from the No. 4 reactor’s spent fuel storage pool and the monitoring of seawater. The preliminary summary report praised Japan for achieving “good progress” in preparing for the decommissioning process.

The team is expected to submit a final report to the government of Japan by the end of January.

Shunichi Tanaka, chairman of the NRA, reiterated his support for controlled discharges of treated radioactive water.

“I don’t believe the technology is available for easy removal of tritium,” Tanaka told a news conference Dec. 4. “The amount is not particularly mind-boggling from a global perspective. We can’t help discharging water once it has cleared safety levels.”