Even though our onsen town Togura-Kamiyamada is located around 350km from the Fukushima nuclear plants, people are naturally worried about radiation if they visit. Yahoo Maps has recently released a map showing real-time radiation levels for 11 locations in Japan, including Nagano City.
The website address is: http://radiation.yahoo.co.jp/
Although the website is only in Japanese, but the data is presented in easy to understand numbers. And as of this writing, the data shows the level for Nagano at 0.084μSv/hour which calculates to an annual level of0.081mSv/year. The global average is 2.4mSv per year, so our level is well below the average.
Check out the info for yourself, then come and enjoy Nagano with the knowledge that you won't have to worry about radiation.