To safeguard against further damage from aftershocks following Japan’s devastating March 11 earthquake, Tokyo Electric Power Co. announced it will build a dike around part of the Fukushima Daiichi nuclear plant.
Over the weekend, TEPCO and government officials outlined plans for a structure 3 to 6 feet high and 1,500 feet long made from rocks, wire mesh and waterproof sheeting along the southeast side of the plant. The top of the barrier will sit 30 feet above sea level, according to the Daily Yomiuri newspaper. In addition to the existing seawall and plant layout, the dike would help safeguard against a tsunami from a magnitude-8 aftershock originating at the epicenter of the March earthquake.
One aftershock after another has struck the country since the first tremblor and ensuing tsunami killed thousands and knocked out power to the TEPCO plant. According to the Daily Yomiuri, plant officials believe earthquakes still represent a large threat to progress made to bring reactors under control. Other earthquake mitigation will include filling pits connected to tunnels at the reactors with concrete, which began at units 2 and 3 Saturday and should be complete late this month. TEPCO hopes to complete the dike by mid-June.
Plans also call for installing 30 steel pillars beneath the spent fuel tank at unit 4, which was badly damaged by an earlier fire and hydrogen explosion. By the end of July, a wall 3 to 6 feet thick will then be built around them, the newspaper reported.
On Sunday TEPCO also announced that another plant worker has exceeded legal dose limits at the plant. A week after another middle aged woman was relieved of duty after receiving a 17.55-millisievert dose, TEPCO said a woman in her 40s had accumulated a dose of 7.49 millisieverts. The 3-month dose limit for women is 5 millisieverts.
On Saturday, TEPCO reported on radiation measurements from its most exposed workers as of the end of March. According to a release from the Nuclear and Industrial Safety Agency, two people had received doses between 200 and 250 millisieverts, eight people received doses between 150 and 200 millisieverts, and 11 people received doses between 100 and 150 millisieverts.