A publicity stunt to appeal his commitment to the resolution of the nuclear accident.
(Oh wait. Isn't he the one who declared the "cold shutdown state" at Fuku-I and the nuclear accident over, to the ridicule from all over the world? Even the newly installed chief of Nuclear Regulatory Agency said the term is not used right.)
From Jiji Tsushin (9/29/2012):
Prime Minister Noda to visit Fukushima I Nuke Plant on October 7, meet workers
It was revealed on September 29 that Prime Minister Yoshihiko Noda will schedule a visit to Fukushima I Nuclear Power Plant on October 7. He will reshuffle his cabinet on October 1, and by going to the plant as the first visit after the reshuffle he hopes to emphasize his commitment to have the Fukushima nuclear accident as his first priority. It will be his first visit to the plant since September 8 last year.
The prime minister wants to meet and thank the workers who remained at the plant after the nuclear accident started and tried to contain the damage. The workers, who did their best to prevent the damage from spreading in a dangerous situation, have been praised as "Fukushima 50".
So... It takes the prime minister of the country one and a half year to thank the workers who stayed at the plant to try to contain the accident.
If I remember right, from last year, "Fukushima 50" workers were not praised in Japan first. I don't think many Japanese were even aware of them. Foreign media, mostly in the US and UK, reported the desperate work going on at Fukushima I Nuke Plant in March last year, calling the workers who remained at the plant "Fukushima 50" and praised them as heroes. The news was imported to Japan, and the Japanese media started to report about the workers and their work at the plant (here's Asahi, on April 10, 2011, my translation).
Yakuza or not, these workers worked in the middle of the worst nuclear disaster in Japan.
So far, the only recognition these workers got is foreign - Spain's Prince of Asturias Award for Concord in September 2011.
In case you missed, here's what ex-Plant Manager Masao Yoshida said about those early days, when he saw divine figures sprung out of the ground and became the workers (here and here).