Mr. John Roos, US Ambassador to Japan, is visiting Fukushima with officials from 30 US companies in decontamination business, promising full cooperation in Fukushima's effort to have the residents come back to their homes in the areas contaminated with radioactive materials from the Fukushima I Nuclear Power Plant accident.
He also put in a word that the presence of the US citizens, working on the decontamination projects in Fukushima, will be beneficial as it will appeal to the world that Fukushima is now safe.
It was Mr. Roos who recommended the US citizens in Japan to leave the 50-mile (or 80-kilometer) radius from the plant, right after the accident started on March 11, 2011. But now, the US businessmen can be "safely" in Fukushima. After all, US college kids and high school kids have already been in Fukushima, doing cultural exchange and volunteer cleanup work.
So of course it is safe for adults...
From Fukushima Minpo (6/28/2012; emphasis is mine):
除染業務 米国が全面協力 ルース駐日大使が佐藤知事に約束
US will cooperate in all aspects of decontamination work, US Ambassador to Japan Roos promises Fukushima Governor Sato
US Ambassador to Japan Roos met with Fukushima Governor Yuhei Sato on June 27 at the Fukushima prefectural government office, and told him that the US will cooperate in all aspects of decontamination work utilizing the US technologies. Officials from 30 US companies in decontamination businesses accompanied Ambassador Roos.
Ambassador Roos said, "The US possesses the cutting-edge technologies in decontamination, and can be a good partner to solve problems that Fukushima faces. All these people here [probably referring to the businessmen who accompanied him] are also thinking of what they can do to help Fukushima." He further said, "By having the US citizens in Fukushima, we can appeal to the entire world that [Fukushima] is safe."
Governor Sato thanked the ambassador for the help from the US after the March 11, 2011 earthquake/tsunami, and said "Decontamination is a huge task as we proceed on having the residents return home. I hope the visit to Fukushima this time will [further?] enhance your [decontamination] technologies."
The group was briefed on the progress of decontamination work in the prefecture by the officials from the prefectural government and the Fukushima City government in Sugitsuma Kaikan [conference center and lodge run by the Fukushima prefectural government] in Fukushima City. Afterwards, they visited the decontamination sites in Nankodai and Onami Districts in Fukushima City and in Date City.
Ambassador Roos visited Fukushima in January this year, and spent more than one hour talking to residents from Okuma-machi in their temporary housing in Iwaki City. That's much more than most Japanese government politicians have done.