Prof. Takeda Kunihiko from Chubu university roughly estimated anyone can no longer live in Japan after 3/31/2015.
According to his explanation, the yearly dose will reach 5mSv/y (External dose and the slight internal dose) in 3 years and 4 months from January of 2012.
He states, he receives radiation data from one of his readers. The person measures radiation three times a day, at work, doorway of house, and the living room in Mie prefecture (500km from Fukushima). Prof. Takeda admits the data is scientific enough.
From the radiation level has been in the increasing trend since last September. In linear equations (y=ax+b), the average from January to March (=b) is 0.10 μSv/h, a is +0.004 μSv/h. y reaches 5mSv/y in 3 years and 3 months, so yearly dose will be over 5mSv/y in 3 years and 4 months from January of 2012, when is 3/31/2015.
Read more; http://fukushima-diary.com/2012/04/prof-takeda-3312015-is-the-last-day-of-japan/