2 Mars 2012
March 2, 2012
As Japan prepares to mark the first anniversary of the meltdowns at the Fukushima No. 1 nuclear plant, the facility remains plagued with problems despite Prime Minister Yoshihiko Noda's declaration that the crisis has been brought under control.
In order to decommission reactors No. 1 through 4 at the crippled plant, it is imperative to improve the work environment by draining and decontaminating areas submerged in radioactive water as much as possible. The flow of ground water into these areas, however, means making such operations a reality is a long way off.
According to plant operator Tokyo Electric Power Co. (TEPCO), the amount of radioactive water at the plant, inclusive of treated water, has reached as much as some 200,000 cubic meters. The utility has managed to secure 165,000 cubic meters worth of temporary tanks and has been building tanks that can hold another 40,000 cubic meters of water, on top of a 4,000-cubic-meter underground "reservoir" being built. However, all of these facilities are expected to be full by this fall, making the utility's efforts look like a shoestring operation even almost a year after the onset of the nuclear crisis.
Three essential tasks must be performed to shut down a nuclear plant: suspending the reactors, cooling them and containing radioactive materials. However, hydrogen explosions at the Fukushima No. 1 plant's reactor buildings in the days after the tsunami hit damaged the reactor pressure vessels. In the opening hours of the crisis, pumper trucks and other machinery injected water into the reactors to cool them, but the water leaked out of the damaged pressure vessels and into the basements of the buildings -- a continuing problem that has led to the ever-growing stock of contaminated water.
In June last year, TEPCO set up a circulating cooling system, in which radioactive materials are removed from contaminated water so that the water can be re-injected into the cores. The system had initially been made up of four stages -- oil separators provided by Toshiba Corp., cesium absorption equipment provided by Kurion Inc. of the United States, a decontamination apparatus set up by France's Areva SA, and desalination units by Hitachi Ltd. Areva's system, plagued with repeated water leakages, was later designated as a back-up. As the total pipe length of these systems extends four kilometers, the risk of leaks remains.
In a road map for bringing the nuclear crisis under control announced by TEPCO in April last year, the utility had stipulated that the contaminated water would be treated and reduced by mid-January 2012. However, the utility pushed that deadline back to fiscal 2020 in its plant decommissioning plan announced in December last year.
Water flowing in from outside the plant has also been hampering the treatment of contaminated water. On top of rainwater pouring in through the damaged reactor buildings, 200-500 cubic meters of groundwater is estimated to be seeping into plant building basements daily.
"The more contaminated water we collect, the more groundwater flows in because of the changes in water pressure," TEPCO spokesperson Junichi Matsumoto explains. In order to keep the pressure balanced, TEPCO has been maintaining the level of contaminated water in the basements, and no serious solution is in sight.
Furthermore, it appears difficult to dispose of the highly radioactive waste generated from the treatment of contaminated water. As of Feb. 21 this year, 581 cubic meters of radioactive mud has been accumulated, along with 358 used cesium filters. While TEPCO is planning to introduce dedicated containers for such materials by fiscal 2014, its road map for decommissioning the reactors only states that the materials "will be transported to disposal sites" as if these will be the final destination for the waste.