At the time of the accident, I learnt that, previously, the radiation dose limit for the general public was stipulated by law as one millisievert in a year (or 0.23 microsievert per hour).
Before the nuclear power plant accident, the radiation level in Fukushima city was 0.03 microsievert per hour. Immediately following the 2011 accident, even inside homes, the level was 0.6 microsievert (approximately 20 times the normal level), and outside, the level was commonly 2 microsievert or higher (some 66 times the normal level). This amounts to levels far in excess of one millisievert per year. I thought that this was abnormal (and a violation of law).
On April 19, 2011, in Fukushima prefecture, the level at which children were permitted to engage in outdoor activities was changed to 20 millisievert a year, or 3.8 microsievert per hour. Thus, the former standard of 1 millisievert per year was raised to 20 times that level.
via — On March 31, 2017, Japan cuts off free housing for “voluntary” evacuees; one mother’s story | Heal Fukushima