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Friday, April 22, 2011
Tepco's road map
Tokyo Electric Power Co. on Sunday announced a road map for actions to bring the nuclear crisis at its Fukushima No. 1 nuclear power plant under control. It is expected to take three months to steadily decrease the release of radioactive materials while cooling the reactors (Step 1), and additional three to six months to keep the reactors continuously cooled at less than 100 C (Step 2).
In Step 1, Tepco plans to flood the containment vessels of reactors Nos. 1 and 3 with water to the top of the active fuel. But it is not certain whether this process will cool the reactors sufficiently. Furthermore, a strong quake during this step could severely damage the reactors.
Tepco also plans to use adhesive cement to close a crack in the suppression pool at the base of the No. 2 reactor's containment vessel. But how will it locate the crack? And when the breach is found, how will it carry out the work to patch the leak in an environment of extremely high radiation levels?
Tepco faces a dilemma. It must cool the reactors by pouring water into them continuously. But the water becomes contaminated with radioactive materials and finds its way into the reactor basements and linked trenches, thus contaminating underground water. It also seeps into the sea.
An estimated more than 67,000 tons of contaminated water existed at one point in the power plant. Tepco plans to transfer the water into tanks, but that won't solve the problem.
Common sense suggests that Tepco should build facilities outside the reactors to cool water that has been poured into the reactors — large cooling towers — then set up a system to circulate the water between the reactors and the cooling towers.
Tepco also plans to place covers over the damaged outer buildings of the Nos. 1, 3 and 4 reactors. But steam will be trapped, making conditions for restoration work difficult. Nuclear power experts must do what they can to assist Tepco. The government and Tepco also should make public detailed information on the spread of radioactive materials, radiation levels at as many places as possible as well as the degree of reactor damage.