Temporary water storage tanks at the Storage Area (North Side) of the Fukushima Daiichi Nuclear Power Station. These tanks are used for storing low-level radioactive materials in Unit 5 and 6, 27 May 2011. TEPCO

October 3 (Mainichi Japan) – Three months after the start of full-scale water circulation system operations at the crippled Fukushima No. 1 Nuclear Power Plant, high-level radioactive waste has kept piling up amid no clear indications of its final disposal destination. As of Sept. 27, plant operator Tokyo Electric Power Co. (TEPCO) had accumulated about 4,700 drums of radioactive waste after three months of cesium decontamination operations initially using U.S. and French equipment which was later joined by Toshiba Corp.’s “Sally” system in August. Since the start of October, TEPCO has conducted the plant’s water circulation operations using the Sally system alone while relegating its U.S. and French counterparts built by Kurion Inc. and Areva SA, respectively, to backups. The Kurion and Sally systems are designed to purify decontaminated water through an absorption unit called a “vessel” that contains zeolites. The vessel is changed every few days and the used vessels become radioactive waste. Areva’s water treatment system filters contaminated water by having sand absorb radioactive materials and precipitate with the help of chemicals. But the treatment produces highly polluted sludge. According to TEPCO, radioactive waste as of Sept. 27 included 210 Kurion-made vessels (a total of about 307 cubic meters) with each vessel measuring 0.9 meters in diameter and 2.3 meters in height and 581 cubic meters of sludge via the Areva unit. The radioactive waste has been kept at a temporary storage site on the premises of the Fukushima plant, which was heavily damaged by the March 11 earthquake and tsunami, and subsequent hydrogen explosions and meltdowns. But TEPCO has been unable to fully grasp the details such as the types and the concentration of nuclear materials. Professor Akio Koyama at Kyoto University Research Reactor Institute says, “The density of high-level decontaminated water is believed to be a maximum 10 billion becquerels per liter, but if it is condensed to polluted sludge and zeolites, its density sometimes increases by 10,000 times. The density cannot be dealt with through conventional systems.”

Radioactive waste piles up at Fukushima nuclear plant as disposal method remains in limbo