Probabilistic biosphere modeling for the long-term safety assessment of geological disposal facilities for radioactive waste using first- and second-order Monte Carlo simulation.

In the present paper, deterministic as well as first- and second-order probabilistic biosphere modeling approaches are compared. Furthermore, the sensitivity of the influence of the probability distribution function shape (empirical distribution functions and fitted lognormal probability functions) representing the aleatory uncertainty (also called variability) of a radioecological model parameter as well as the role of interacting parameters are studied. Differences in the shape of the output distributions for the biosphere dose conversion factor from first-order Monte Carlo uncertainty analysis using empirical and fitted lognormal distribution functions for input parameters suggest that a lognormal approximation is possibly not always an adequate representation of the aleatory uncertainty of a radioecological parameter. Concerning the comparison of the impact of aleatory and epistemic parameter uncertainty on the biosphere dose conversion factor, the latter here is described using uncertain moments (mean, variance) while the distribution itself represents the aleatory uncertainty of the parameter. From the results obtained, the solution space of second-order Monte Carlo simulation is much larger than that from first-order Monte Carlo simulation. Therefore, the influence of epistemic uncertainty of a radioecological parameter on the output result is much larger than that one caused by its aleatory uncertainty. Parameter interactions are only of significant influence in the upper percentiles of the distribution of results as well as only in the region of the upper percentiles of the model parameters.

Interdisciplinary perspectives on dose limits in radioactive waste management. A research paper developed within the ENTRIA project.

Within the ENTRIA project, an interdisciplinary group of scientists developed a research paper3 aiming at a synthesis of the technical, sociology of knowledge, legal, societal, and political aspects of dose limits within the field of radioactive waste management. In this paper, the ENTRIA project is briefly introduced and the work on dose limits is put into the perspective of this much larger project. Selected aspects of the ENTRIA work on dose limits related to the different roles such limits play for different actors as well as to the specific case of nuclear waste disposal are presented. The work recognizes that such limits are indispensable for technological developments and legal security but, at the same time, depend on country and project specific circumstances. This may result in serious conflicts and concerns in public debates as well as in the political realm. In order to better understand the interaction and interdependencies of these various contexts in which debates about dose limits play out, future interdisciplinary research is needed. This research should contribute to an open discourse on dose limits which reflects underlying values, objectives, actors and procedures that have defined present dose limit regimes. Additionally, this research should indicate paths for potential alternatives and complements to these established regimes.