Séminaire spécialisé

mardi 5 mai 2015 à 16:00


Speciation of tritium and carbon-14 with organic molecules in nuclear plant effluents

Christophe MERIGNAC

Subatech (groupe Radiochimie)

Tritium and carbon-14 are the main contributors of the activity released in the effluents of nuclear power plants. Studies on the behavior of tritium and its impact on humans have raised many questions like a possible bioaccumulation of tritium in biological compounds. In 2008, ASN (Autorité de sureté nucléaire) started an extensive program based on increasing the knowledge of tritium and its impact on the environment. This led to the publication of the “Livre Blanc” of Tritium in 2010. Whereas the conclusion indicates no bioaccumulation, it was pointed out that further studies should be undertaken to better understand the distribution (speciation) of tritium in different physical forms (gaseous and
The results provided by EDF to the ASN show that, in gaseous effluents, 90 % of tritium is released as tritiated water (HTO) and 10% as hydrogen tritiated (HT). For the liquid effluents the knowledge is currently less accurate. Only the activity
of HTO has been measured but the distribution between HTO and OBT (organic-bound tritium) data is not available. For this reason, the first aim is to determine the speciation of tritiated species in liquid effluents. The second aim is the C-14 speciation distribution in the liquid effluents.
The presentation will be focused on the following points:
· Development and optimization of analytical methods for
separating/concentrating organic molecules
· Identification and quantification of the different organic molecules that
may be present in the effluents (bibliography study)
· Quantification of the distribution of HTO/OBT in this effluents
From the literature review it was identified that from on one hand, organic molecules may be present in different effluents of nuclear plants, characterized mainly as amines (morpholine, hydrazine and ethanolamine) and carboxylic (acetate and formate) and, for other hand, different chromatography techniques has been used to identify their speciation (ion chromatography, reversed-phase HPLC with UV and/or conductivity detection). It was developed and optimized a method in order to analyze the organic molecules and to determine their limits of detection (LD) and quantification (LQ). And, two techniques (freeze drying and distillation under reduce pressure) were
conducted to eliminate the tritiated water fraction, where a comparative study between both techniques was carried to estimate their performance. The aims of these two techniques are to eliminate a significant part of activity (elimination of HTO) and concentrate the molecules of interest.