Nagano Prefecture is located basically in the center of Japan and is surrounded on all four sides by 3000-meter tall mountains, earning it the nickname of the “Roof of Japan”. It prevents radioactive materials to reach Nagano prefecture. (Source)
People in Nagano prefecture are fine and I couldn't find any impact of the accident there. People in Nagano prefecture have no worry about the accident, because there is no nuclear power plant in Nagano and there are no contaminations by the accidents.
Posted by Yoshitaka Kiriake from Japan on February 25, 2013.
----Updates on Local Radiation Levels----