[en] The Swiss Federal Nuclear Safety Inspectorate (ENSI) is in charge of reviewing the work developed by the National Cooperative for the Disposal of Radioactive Waste (NAGRA) in Switzerland. Within the context of the Opalinus Clay project, the performance and safety assessment exercise developed by NAGRA involved the derivation of Biosphere Dose Conversion Factors (BDCF). The objective is the derivation of BDCF by using an alternative modelling tool and the study of how several simplifications incorporated to the model can affect the results. It constitutes the basis of an expanded study aiming at developing ENSI's biosphere modelling capabilities, including the selection of a suitable computer program for biosphere transport and dose calculations alternative to the one used by NAGRA. The compartmental code AMBER has been used to obtain the values of the BDCF, in contrast to the code Tame used in the assessment of NAGRA. The results obtained agree with the ones reported by NAGRA. The project has been divided into four sections dealing with (1) the description of the conceptual model and its implementation in AMBER, (2) the comparison between BDCF results obtained by NAGRA and the ones derived in this study, (3) sensitivity analyses of the results versus different exposure pathways and contamination paths and (4) the comparison of the BDCF resulting from the reference model with the ones obtained by other biosphere approaches carried out by different national radioactive waste management agencies. Twelve radionuclides have been included in the analyses: four non-metallic elements (¹⁴C, ³⁶Cl, ⁷⁹Se, ¹²⁹I) and 8 metallic elements that are part of the decay chain of ²⁴⁶Cm (²⁴²Pu, ²³⁸U, ²³⁴U, ²³⁰Th, ²²⁶Ra, ²¹⁰Pb, ²¹⁰Po). Ingestion is the pathway contributing most to the total received dose for an individual. Two general trends can be distinguished between metallic and non-metallic elements: metallic elements present high sorption coefficients, resulting in higher concentration in the top-soil and bed sediments, while non-metallic elements are more concentrated in the local aquifer and surface water. Ingestion of milk provides a good example to study this distinctive behaviour. Soil consumption and pasture consumption contaminated by root uptake are the main mechanisms of milk contamination in the case of metallic elements, while drinking water and consumption of pasture contaminated by irrigation are the ones dominating for non-metallic elements. The elimination of the solid material fluxes in the model results in calculated BDCF higher than the ones of the reference case. A comparison has been done between the model implemented and the approaches followed by different radioactive waste management agencies. The following three aspects of the comparison and sensitivity analyses exercise can be highlighted: 1) The model implemented in TAME by NAGRA is transportable to the AMBER code, the results do not depend on the numerical code used; 2) The sensitivity analyses have shown that ingestion is the main contributor to the dose, and that the exposure pathways through fish and eggs can be neglected; 3) For most of the metallic radionuclides, BDCF up to 3 times larger are obtained if solid material fluxes are neglected. This highlights the relevance of accurately describing the association of radionuclides with solid material as well as the adequacy of selecting an appropriate set of data to describe solid/radionuclide interactions.