22 Août 2013
August 22, 2013
Tokyo Electric Power Co. (TEPCO)'s ambitious scheme to deal with contaminated water at the crippled Fukushima No. 1 Nuclear Power Plant is on the verge of collapsing, as the safety of storage tanks built on the complex has been called into question after highly radioactive water leaked from one of the aboveground storage tanks.
TEPCO, the operator of the badly-damaged nuclear power station, has been building one tank after another in a "shoestring operation" to store ever-increasing highly contaminated water. The Nuclear Regulation Authority (NRA) said the severity of the leakage of highly radioactive water is on par with a level-3 (serious incident) on the International Nuclear and Radiological Event Scale. But because the nuclear crisis has remained unresolved with no end in sight, the current situation cannot be assessed easily by conventional yardsticks.
TEPCO Executive Vice President Zengo Aizawa exhibited a sense of crisis, saying at a news conference on Aug. 21, "This is the biggest management crisis. Taking it as a pressing matter of the highest priority, we want to respond to this problem." He made the comment because about 300 metric tons of highly contaminated water leaked from one of the aboveground storage tanks. The leakage of the contaminated water from the tank set off alarm bells about TEPCO's scheme to store radioactive water.
Contaminated water continues to increase over time because about 400 tons of groundwater flows into damaged reactor buildings each day and comes into contact with melted nuclear fuel, turning itself into highly radioactive water. This process started immediately after the outbreak of the nuclear crisis at the Fukushima plant. There is also water contaminated with relatively low levels of radioactive substances that are produced after highly radioactive water has been treated by purification equipment.
If contaminated water, regardless of the levels of radiation, flows out of the complex, it will contaminate the environment. Therefore, TEPCO has been storing such water in tanks and other containers on the premises of the nuclear complex. As of Aug. 20, the total volume of such water stood at about 430,000 tons.
Initially, TEPCO had built seven underground storage tanks (for a total of 58,000 tons of water) that could store a lot more water at once than aboveground storage tanks that cannot be built easily and quickly. But contaminated water was found to be leaking from underground storage tanks in April this year. Thus, far more than 20,000 tons of contaminated water was hastily transferred from the underground tanks to aboveground tanks that were hurriedly built. The situation worsened to a level so bad at one time that experts predicted that only 3,600 tons of additional water could be stored in the aboveground tanks.
TEPCO aims for full-scale operations of its water decontamination system, called the Multi-nuclide Removal Equipment (ALPS), which could remove up to 62 kinds of radioactive substances from up to 500 tons of water each day. TEPCO also worked out a plan to build an "underground water bypass" system to pump up uncontaminated water before flowing it into the damaged reactor buildings and release it outside. On Aug. 7, Prime Minister Shinzo Abe said, "Instead of leaving it to TEPCO, the government will take measures." The government then started to extend financial assistance for a project to build walls of frozen soil to reduce the amount of groundwater flowing into reactor buildings.
The government and TEPCO had believed that if such measures worked to stop water from being contaminated with radioactive substances, they would be able to deal with the problem of the contaminated water under the current plan by increasing the total volume of storage tanks to about 800,000 tons of water by fiscal 2016.
But the ALPS system that began to run on a trial basis at the end of March this year was forced to shut down after it was found to have been leaking water in June. Furthermore, the device is not technically capable of removing radioactive tritium. The underground bypass system has not been built yet because of opposition from local fisheries cooperative associations that are concerned about harmful rumors about radioactive contamination.
There has been no successful case elsewhere in the world of a large-scale project to build walls of frozen soil, and therefore it remains unclear whether the project under consideration will actually be effective. The life span of the storage tank in question is five years, and therefore the tanks should be regularly replaced with new ones. The cause of the leakage of the radioactive water has yet to be found, and TEPCO is faced with another task of checking more than 1,000 small and large tanks on the premises of the nuclear complex.
At a working-group meeting of the NRA held on the evening of Aug. 21, some of the participants proposed that water-level gauges should be installed in the same type of storage tanks that leaked contaminated water. Other participants also urged TEPCO to transfer contaminated water to different types of tanks. But it is not easy to obtain such storage tanks.
NRA Chairman Shunichi Tanaka said, "We fear a situation in which we have no control unless (contaminated water) is dumped into the ocean as the number of tanks keeps increasing rapidly." He stressed that it is necessary to release water into the ocean after treating it with the ALPS system. But the consent of local residents and communities is needed to do so. It has become even harder for TEPCO, therefore, to secure the understanding of local residents and communities to release water into the ocean because of revelations in July of contaminated underground water flowing into the ocean and the "level 3" leakage of radioactive water from the aboveground storage tanks.
Yuzo Onishi, chairman of the government committee on contaminated water treatment countermeasures, said, "Unless drastic measures are taken promptly, the Fukushima No. 1 Nuclear Power Plant will collapse at some point." (By Shinpei Torii and Motofumi Fujino, Tokyo Science and Environment News Department)