Generic guidance on the withdrawal of sheltering, withdrawal of evacuation and evacuation of sheltered populations (displacement) has been developed based on previously unpublished work in the UK and France and on input from stakeholder panels in Germany, Belgium, France and the UK. The guidance is a living document that can be developed further in the future, both in its generic form and also as customised versions in some Member States. The guidance outlines the many factors which influence the withdrawal of emergency countermeasures: official confirmation that any release has stopped; adequacy of monitoring data; radiological criteria; radiological protection advice; availability of resources; social and psychological needs; stakeholder dialogue; and communication strategy. The relative importance placed by decision makers on each of these criteria would vary according to the nature and scale of the accident and also on socio-political, economic and cultural perspectives. In the event of a radiological incident, decision makers will need to be in a position to construct a strategy for managing the withdrawal of emergency countermeasures. For larger scale, longer duration releases involving several nuclides, a management strategy is likely to be complex. The guidance therefore includes a series of checklists which have been developed in conjunction with stakeholders to take into account the main criteria and factors which should be considered.

In nuclear and radiological emergency and post-accident management decisions on countermeasures and remediation strategies have to be made. Whereas in the early phase decisions on emergency actions must be made in a very short time, according to emergency plans and dose thresholds, in the recovery phase complexity is higher. But there is also more time for evaluating alternative countermeasures and remediation strategies with respect to several goals. In this paper evaluation strategies supporting the decision makers throughout all phases are presented. The applied decision support techniques range from graphical presentations of decision relevant information about the alternatives for action to multi-criteria decision making (MCDM) methods. In particular methods to cope with several types of uncertainties inherent in the different phases are presented. By the integration of these techniques, the decision support system RODOS is able to provide support for more conscious, transparent and coherent decision making.

It is commonly assumed that heat flux and temperature diffusivity coefficients obtained in steady-state measurements can be used in the derivation of the heat conduction equation for fluid flows. Meanwhile it is also known that the steady-state heat flux as a function of temperature gradient in stably stratified turbulent shear flow is not monotone: at small values of temperature gradient the flux is increasing, whereas it is decreasing after a certain critical value of the temperature gradient. Therefore the problem of heat conduction for large values of temperature gradient becomes mathematically ill-posed, so that its solution (if it exists) is unstable.

In the present paper it is shown that a well-posed mathematical model is obtained if the finiteness of the adjustment time of the turbulence field to the variations of temperature gradient is taken into account. An evolution-type equation is obtained for the temperature distribution (a similar equation can be derived for the concentration if the stratification is due to salinity or suspended particles). The characteristic property which is obtained from a rigorous mathematical investigation is the formation of stepwise distributions of temperature and/or concentration from continuous initial distributions.