Estimation of the Release Time of Radio-Tellurium During the Fukushima Daiichi Nuclear Power Plant Accident and Its Relationship to Individual Plant Events

A simulation model was developed to estimate the areal (surface) deposition pattern of ^129mTe after the Fukushima Daiichi nuclear power plant (FDNPP) accident. Using this model, the timing and intensity of the ^129mTe release were reverse estimated from the environmental monitoring data. Validation using ¹³⁷Cs data showed that the model simulated atmospheric dispersion and estimated surface deposition with relatively high accuracy. The estimated surface deposition pattern of ^129mTe was consistent with the actual measured pattern. The estimated time and activity of ^129mTe emissions indicated that ^129mTe was predominantly emitted from FDNPP Unit 3.