Towards a monitoring framework for the source term estimation during the early phase of an accidental release at a nuclear power plant

In the RODOS project data assimilation methods are under development to assess the radiological situation in real time in case of an accident at a nuclear power plant. Due to the short time available to take decisions during the early phase a judicious combination of model predictions and monitoring data will have to be used. It is shown that actual site-specific monitoring strategies in Europe are not adapted to this new method. A new site-specific monitoring framework is proposed. Assimilation of simultaneous on-line gamma dose rates from detectors located around an installation constitutes the first and principal source of information to assess the magnitude of the release. Complementary mobile monitoring of particulates, iodine and noble gases can then directly be correlated to the gamma dose rates. The information about the exact monitoring location is not used, provided the three components are sampled simultaneously in a β field.