A simple and fractal analysis of the European on-line network for airborne radioactivity monitoring.

We introduce two simple descriptors and use the fractal dimension to characterize the capability of a monitoring network to either 'spot', 'delineate' or 'track' a pollution cloud moving across a territory. The descriptors are applied to the 'European' monitoring network for radioactive aerosol (i.e. the sum of the national networks). Simple analysis shows that on average the time and space resolution of the network are well balanced for tracking the movement of a radioactive cloud. Such tracking, however, can only be started one or two days after the release. The geographical inhomogeneity of the network is quantified by a fractal dimension of 1.6, implying that radioactive clouds with a dimension less than 0.4 might not be detected by the network.