Mopping the floor

Mr. Friedlander, the former nuclear plant operator who is a specialist in emergency responses to nuclear accidents, said that the Japanese decision to evacuate more communities made sense not just to protect people, but also to make the eventual decontamination of farms and communities easier.

Allowing people and nonemergency vehicles to continue moving through both radiation-contaminated areas and safer areas farther from the Fukushima reactors runs the risk of spreading radioactively contaminated particles, which could result in more square miles of territory ultimately being contaminated. “Unless you gain control, it will be like trying to mop your kitchen floor with the kids running in and out of the house,” Mr. Friedlander said.

Masataka Shimizu, the president of Tokyo Electric, visited the tsunami-stricken area on Monday for the first time since the crisis began. He called on the governor of Fukushima Prefecture, Yuhei Sato, but was refused a meeting. He left his business card instead.