Radiation Spread Seen; Frantic Repairs Go On

VID E. SANGER and WILLIAM J. BROAD

Published: March 17, 2011

The data was collected by the Aerial Measurement System, among the most sophisticated devices rushed to Japan by the Obama administration in an effort to help contain a nuclear crisis that a top American nuclear official said Thursday could go on for weeks. Strapped onto a plane and a helicopter that the United States flew over the site, with Japanese permission, the equipment took measurements that showed harmful radiation in the immediate vicinity of the plant — a much heavier dose than the trace levels of radioactive particles that make up the atmospheric plume covering a much wider area.