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