Timeline of the Fukushima Daiichi nuclear disaster pumps could be retrofitted to deliver concrete for that purpose. Prior to the elevation to level 7 by the Japanese authorities James Acton, Associate of the Nuclear Policy Program at the Carnegie Endowment for International Peace, was of the opinion that "Fukushima is not the worst nuclear accident ever but it is the most complicated and the most dramatic, was a crisis that played out in real time on TV. Chernobyl did not." A survey of radiation in seawater outside unit 2 shows radioactive isotope concentrations (iodine-131, caesium-134 and caesium-137) falling for the third consecutive day since the leak was
Caesium which could create wide-ranging contamination, gradually put some of these caesium sources out of use. Caesium-137 has been employed in a variety of industrial measurement gauges, including moisture, density, levelling, and thickness gauges. It has also been used in well logging devices for measuring the electron density of the rock formations, which is analogous to the bulk density of the formations. Caesium-137 has been used in hydrologic studies analogous to those with tritium. As a daughter product of fission bomb testing from the 1950s through the mid-1980s, caesium-137 was released into the atmosphere, where it was absorbed readily into solution.