Radioactive Sludge Collects in Japan's Sewage Treatment Plants

Special Report: Fukushima and the Future of Nuclear Power

Editor's Note: John Boyd is an IEEE Spectrum contributor reporting from Kawasaki, Japan. This is part of IEEE Spectrum's ongoing coverage of Japan's earthquake and nuclear emergency.

Toxic Sludge

Japan is struggling to deal with a new threat arising from the Fukushima nuclear crisis: contaminated sludge. And just like the thing in the old sci-fi movie The Blob, the problem keeps growing, with thousands of tons of waste accumulating in water treatment and sewage plants across eastern Japan.

The sludge is composed mostly of earth and sand, the residue from river water purification and sewage treatment systems. A significant percentage of it has become contaminated with radioactive cesium isotopes, which apparently came from the troubled Fukushima Dai-1 nuclear plant.

According to the latest figures from the Ministry of Health, Labour and Welfare, the amount of accumulated dehydrated sludge stored in water treatment facilities in 14 prefectures in eastern Japan was 92 000 tons as of July 28, while sludge from sewage treatment plants topped 35 000 tons as of August 12. Press reports said some 37 000 tons of this total was judged to be radioactive.

More recently, NHK, Japan’s national broadcaster, conducted its own survey of 17 prefectures and says the figure for radioactive sludge has now grown to about 50 000 tons, with over 1500 tons “so contaminated that it cannot be buried for disposal.” It added that another 50 000 tons had still to be checked.

Such findings have worried municipalities where treated sludge had been disposed of to date, and they are refusing to accept contaminated waste, forcing the water and sewage treatment plants to store the waste on their sites. Consequently, some plants are running out of storage space. Worse, NHK reported that a wastewater treatment facility in Gunma Prefecture, north of Tokyo, has had to suspend operations because the radiation from the stored contaminated sludge exceeds workers’ safety limits.

According to preliminary government guidelines issued in June, such contaminated waste can be stored on a temporary basis, providing radioactivity is less than 100 000 becquerels per kilogram and provided provisions are made to prevent any seepage into the ground. More highly contaminated materials should be stored in shielded facilities until the government decides how best to deal with it.

The guidelines also state that waste with radiation levels below 8000 becquerels per kg can be buried in controlled land-fill sites. Sludge with higher contamination levels can be incinerated under certain conditions, though the resultant ash needs to be stored.

Goshi Hosono, the minister in charge of the nuclear crisis said an expert committee is discussing how to deal with the problem, and he added that the government is considering bearing the cost of disposing of the waste.

A Nuclear Restart

On August 17, the No. 3 reactor at Hokkaido Electric Power Company’s Tomari nuclear plant in northern Japan became the first reactor since the March 11 earthquake to resume operations. But this doesn't signal a push towards restarting any of Japan's other 39 reactors that are currently out of service, either for maintenance inspections or due to damage or malfunctions.

When the March 11 earthquake struck the No. 3 reactor was in the last stage of resuming full operations after undergoing a maintenance inspection. As a result, the reactor remained in the “adjustment stage of operations” for an unprecedented five months, albeit while working at its full capacity of 912 megawatts. During that time the government came up with its two-stage scheme of stress tests for off-line nuclear reactors, which have to be passed before the reactors can resume operations. This added to the Tomari delay. But now that the Nuclear and Industrial Safety Agency (NISA) has issued its approval and the Hokkaido governor has assented, the reactor’s status has changed to one of normal commercial operations.

A Regulatory Reshuffle

In a move long expected, the Japanese government has decided to establish a new nuclear safety agency to oversee all matters related to nuclear energy, including security, radiation monitoring, safety inspections, and accident response. It will take over these tasks from NISA, the Nuclear Safety Commission, and other related agencies, including the Ministry of Science, which currently conducts radiation monitoring.

The decision was taken because the Ministry of Economy, Trade, and Industry (METI), which oversees NISA, was also promoting the use of nuclear power, even while NISA was expected to independently regulate the industry. Critics of this arrangement have noted that as many as 16 senor officials have shuffled between the nuclear promotional arm of METI and NISA in recent years. Similarly, a notable number of NISA officials have retired from the ministry only to join the power companies that they previously regulated. NISA has also been accused of using its influence over the power companies to have them sway public opinion during public hearings on controversial policies.

Commenting on the decision today, Goshi Hosono said, “I have keenly felt that we could never regain public confidence unless we fundamentally corrected (our) ways of regulating nuclear power, the relevant organizations and the levels of our response to these issues.”

Tentatively called the Nuclear Safety and Security Agency, the new entity will be established next April, after the government passes the necessary bills through the national Diet, and it will come under the authority of the Environment Ministry. Critics, however, point out that the Environment Ministry has few nuclear experts, and they wonder how much will really change if the new agency is to be staffed by the same people from the two current nuclear regulatory agencies. 

In another long expected move, Prime Minister Naoto Kan announced his resignation today. Kan has been widely criticized for the government's response to the earthquake, tsunami, and nuclear disaster. He has planned to resign for several months, but stayed in office long enough to get several bills passed, and to map out the new nuclear regulatory agency.

IMAGE: KYODO / AP PHOTO

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