Deduction of useful information from dose rate monitoring data under emergency conditions

The surface concentrations and release rates of radionuclides were estimated from gamma dose rates by using a rigorous modeling approach based on the relation between the dose rates and the concentrations. It was shown by applying this method to non-accidental cases that the surface run-off of deposited radionuclides can be analyzed. The concentrations of deposited radionuclides were in good agreement with the observations, although a difference in estimations among monitoring stations was observed due to radionuclides deposited on trees. The release rates estimated with the dose rates at the boundary of the Fukushima Daiichi Nuclear Power Station were in reasonable agreement with JAEA's estimations. However, sensitivity analyses indicated that these estimations have a large uncertainty. (author)