Just as TEPCO workers have been spraying a green polymer resin over the Fukushima Daiichi site to prevent radioactive dust from blowing away, the utility has now announced plans to cover contaminated sand in the intake canals of units 1-4 and 5&6.
Cross-section of seabed coating medium (magnified)
Concerned that contaminated soil might be spread outside by wave action, the utility has been working since January on a survey of the seabed inside the port, and since December on a suitable covering material.
It now proposes to cover the seabed with two layers of bentonite clay/concrete mixes. These materials have the advantages of not affecting the coastal environment and have a uniform make-up. A lighter-coloured lower layer will consist of a lightweight mix to cover the highly-mobile floating mud on the seafloor. On top of it will be a second, more durable layer.
The materials will be provided, mixed and poured on site on several barges. A special mixing barge has arrived at site, and will feed a crane barge holding a tremie pipe, which is designed to pump concrete under water.
A test pour was due to start on 25 February.
TEPCO plans to monitor radionuclide content before, after and during construction to understand if the construction work tends to contaminate the area. As part of the work, TEPCO will also install a silt fence across the unit 5&6 intake canal to reduce the spread of radioactive material.
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