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A critical evaluation of the dissolution mechanisms of high level nuclear waste glasses in conditions of relevance for geological disposal

Objective

Different theories have been proposed worldwide in the past years to interpret the considerable decrease with time of the dissolution rate of high-level waste glass upon contact with geological disposal media. These interpretations refer to saturation effects in the solution, to protecting effects of the reaction layer on top of the glass, or to ion exchange processes. The diverging interpretations hamper the efficiency of the R&D in this field and were recognized during an international workshop held in 2000. The objective of the proposal is mainly to achieve a common understanding on this interpretation. This will be achieved by applying a selection of existing analytical models on a limited amount of existing experimental data, both models and data referring to the differing interpretations, and by evaluating the output.

Different theories have been proposed worldwide in the past years to interpret the considerable decrease with time of the dissolution rate of high-level waste glass upon contact with geological disposal media. These interpretations refer to saturation effects in the solution, to protecting effects of the reaction layer on top of the glass, or to ion exchange processes. The objectives of the proposal are to achieve a common understanding on this interpretation, and to quantify the uncertainty of the calculations done in models that are nowadays applied to the glass dissolution. This will be achieved by applying a selection of analytical models on a limited amount of experimental data, both models and data referring to the differing interpretations, and evaluating the output. The partners in this proposal involve laboratories that are dealing with these studies.

The project will be split into the following actions (work-packages):
(WP1) Formal overview of the actual status of the R&D on the long-term dissolution mechanisms of high-level waste glasses, emphasizing on the different interpretations of the decreasing dissolution rate, and of the analytical models that have been developed to interpret the dissolution behaviour of the HLW glasses.
(WP2) Selection of the data that will be used for further discussion. The data need to be useful as an input, e.g. produced by different laboratories. They need to be well documented and reliable (uncertainties must be known). The availability of analytical data in excess of the solution analysis, e.g. surface analysis, profiling through the surface, mass losses, will be recommended.
(WP3) Selection of the analytical models that can be applied to the data. The selected models need to be representative for the different interpretations (that are at the basis of this proposal). The models selected should be fully described, and should be explained to the partners of the concerted action in full detail (parameters used, hypotheses, uncertainties).
(WP4) Application of the selected models to the selected experimental data. We propose that the partners apply the model developed by another partner, to their own data.
(WP5) Discussion of the results of the model output, in view of the interpretations of the experiments given before by the responsible institutes, and discussion of a possible common position.
(WP6) Writing of the reports associated with each work package and of the final report.

- Overview of the status of the long-term dissolution mechanisms of high-level waste glass (month 12)
- Selection of data and of the models to be applied to the data (month 12)
- Progress report for the previous actions (month 15)
- Application of the selected models to the selected data (month 24)
- Discussion of the output, and of a possible common interpretation (month 30)
- Final report for all actions (month 36)

Funding Scheme

CON - Coordination of research actions

Coordinator

BELGIAN NUCLEAR RESEARCH CENTRE
Address
200,Boeretang 200
2400 Mol
Belgium

Participants (3)

ASSOCIATION POUR LA RECHERCHE ET LE DEVELOPPEMENT DES METHODES ET PROCESSUS INDUSTRIELS
France
Address
Rue Alfred Kastler 4
44307 Nantes
COMMISSARIAT A L'ENERGIE ATOMIQUE
France
Address
Cea/valrho, Marcoule
30207 Bagnols-sur-ceze
ECOLE NATIONALE SUPÉRIEURE DES TECHNIQUES INDUSTRIELLES ET DES MINES DE NANTES
France
Address
Rue Alfred Kastler 4
44307 Nantes