This paper deals with the experimentation made on different plants such as lichens, trees and lettuces exposed to HT and HTO throughout their lives. These experiments included, in the same time, consideration of meteorological data, measurement of tritium diffusion, characterization of the tritium transfer into biological materials, and dose estimation through the food chain.

Works on lichens collected around the site have confirmed previous results quoted in the literature in regards to OBT levels. However, because of their potential of pollutants accumulation and the difficulty to date them, lichens can not be chosen as bio-indicators.

Measurements carried out on annual rings of trees have shown the related evolutions in time of the OBT levels and the tritium releases of the Valduc Centre. These measures have underlined the possibility to reveal past contamination by OBT analysis around the centre in good correlation with the atmospheric discharge.

The results obtained on lettuces cultivated into the site near a source of tritium appeared as very promising. A global conversion rate from tissue free water tritium to OBT was evaluated to 0.20 - 0.24 %.h-1 in average on the whole growing period, corresponding to the order of magnitude given for many vegetables in the literature.