This photo taken during the tour of the treated water dilution and discharge facility for foreign media shows a blue pipeline to transport seawater, part of the facility for the releasing treated radioactive water to sea from the Fukushima Daiichi nuclear power plant, operated by Tokyo Electric Power Company Holdings (TEPCO), in Futaba town, northeastern Japan, Sunday, Aug 27, 2023. (PHOTO / AP)

The nuclear-contaminated water released from the crippled Fukushima Daiichi nuclear power plant into the ocean, although treated by a multi-nuclide removal equipment, still contains various radioactive nuclides, raising safety concerns both within and outside Japan. Still, Japan plans to release the second batch this week.

“A number of radioactive substances still remain in the contaminated water. I’m really concerned about the safety and health issues that may arise from the discharge of the water into the ocean,” said Michiko Ueno, 64, a woman living in Chiba Prefecture.

TEPCO acknowledged that about 70 percent of the water stored in tanks had concentrations of more than 60 nuclides other than tritium exceeding the regulatory standards for release into the environment 

Mayumi Shirakura, a 74-year-old Tokyo resident, said: “It is wrong to say that the contaminated water is safe scientifically just because it has been processed. There are still many radioactive substances in the water, and that doesn’t change the fact that they are dangerous.” 

READ MORE: Fukushima: Mothers' group voices concerns on wastewater release

The Tokyo Electric Power Company (TEPCO), the Fukushima plant’s operator, said last week that the release of the second batch of radioactive water into the ocean would begin on Oct 5.  

Similar to the first phase, about 7,800 tons of water stored in tanks will be released into the ocean over approximately17 days.

A rapid measurement of tritium concentration in seawater was conducted on Sept 25 at 10 locations within 3 kilometers of the Fukushima plant. The tritium concentration at all locations was below the detection limit — less than 6.3 to 8.7 becquerels per liter, TEPCO, announced on its website. 

The measurement results of the concentration of Cs-137, Cs-134, and Total β (beta radiation) were also below the detection limits at 3:50 pm on Sept 27, TEPCO said. 

In reply to questions from the public, the company said currently, the nuclides that can be observed are limited to tritium, Cs-137, and Cs-134. Going forward, it plans to gradually expand the scope of nuclides that can be observed. 

TEPCO’s samplings of seawater were from the sea surface to a depth of 0.5 meters at several locations in and around the harbor. But since it started releasing contaminated water into the ocean on Aug 24, the company has not updated the information on seawater samplings at several other offshore locations.

However, public trust in TEPCO and the Japanese government has fallen due to problems with the emergency response to the Fukushima nuclear accident in March 2011 and the disposal of the nuclear-contaminated water. 

“They said the water is safe but they are lying. I don’t believe it. What the Japanese government and TEPCO are doing is likely to cause significant damage, not only to Japanese citizens but also to many people overseas. I can’t help but think they’re deliberately hiding something,” said Ikuko Tameguchi, a 64-year-old Tokyo resident. 

“Many people are unaware of the correct information, so I believe we, as taxpayers, should be well-informed and raise our voices,” she added. 

It is not known how many toxic substances such as cadmium and tellurium, which are present in Fukushima nuclear fuel debris, are included in the contaminated water treated by the Advanced Liquid Processing System (ALPS) multi-nuclide removal equipment, said Hikaru Amano, advisor to the Beta-ray nuclide measurement lab of the Iwaki Citizens’ Radiation Measurement Center, also known as Tarachine. 

Initially, TEPCO stated that if the contaminated water went through ALPS, it would meet regulatory standards, except for tritium. However, media reports revealed that radioactive substances other than tritium remained in the water at levels above regulatory standards. 

After that, TEPCO acknowledged that about 70 percent of the water stored in tanks had concentrations of more than 60 nuclides other than tritium exceeding the regulatory standards for release into the environment. The company then suggested a secondary ALPS treatment before releasing the water into the ocean.

The Fukushima Daiichi nuclear power plant, damaged by a massive March 11, 2011, earthquake and tsunami, is seen from the nearby Ukedo fishing port in Namie town, northeastern Japan, Thursday, Aug 24, 2023. (PHOTO / AP)

However, tritium, C-14, I-129, Sr-90, Cs-137, Co-60, Ru-106, and Sb-125 cannot be completely removed from the contaminated water even after the secondary treatment. 

There is also uncertainty regarding nuclides such as Ca-41, Cl-36, and Zr-93, said Amano at a webinar hosted by the Citizens’ Commission on Nuclear Energy earlier this year.

Moreover, TEPCO had analyzed only a small portion of the tanks, primarily focusing on the upper layer of the tanks’ supernatant. The high-concentration sludge and sediments in the lower and bottom layers had not been adequately examined, he said.

READ MORE: Japan starts releasing Fukushima wastewater despite opposition 

TEPCO had conducted a radiation impact assessment but only three tank groups, containing slightly less than 3 percent of the total stored contaminated water, were indicated by the company as source terms. 

Given the varied concentration of radioactive substances in the three tank groups, it is questionable whether these truly represent the entire contaminated water supply, said Kanna Mitsuta, executive director at Friends of the Earth Japan, one of Japan’s first NGOs to work on international environmental problems. 

“TEPCO and the government have been actively asserting that nuclear power plants worldwide release water containing tritium. However, what we need to be cautious about is that the treated contaminated water in question is mixed with cooling water from debris in which the fuel has melted. Since it has come into direct contact with the debris, it contains various radioactive substances,” Mitsuta said at the CCNE webinar.

Contact the writer at jiangxueqing@chinadaily.com.cn