The detail of the radiation release from the Fukushima, Japan, nuclear reactors accident in March 2011 are not known. We present a technique for the reconstruction of the release rate based on the SCIPUFF dispersion model and measurements from local stations. The observed radiation data were retrieved from 218 stations located in 17 Japanese prefectures. Meteorological data for the simulation domain area are used. The non-stationary time-series of the release rate is determined for a period of 20 days.