Nuclear Energy Agency Online Bulletin

October 2000

Radioactive Waste Management Information

Launching of the NEA Sorption Project, Phase II

The NEA has launched a new co-operative programme - the Sorption Project, Phase II - with the objective of demonstrating the applicability of chemical thermodynamic models to support the selection of sorption parameters used in safety assessments of radioactive waste repositories.

The project is taking the form of a "benchmarking" exercise for the different modelling approaches in use at the participating organisations. The overall aim is to interpret selected, well-characterised datasets for sorption by complex materials. By applying the various modelling approaches in a systematic way to the same measured data, an evaluation of the merits and limitations of the approaches will be possible and recommendations on the use of these models can be made.

The Project was officially started with the first meeting of the Management Board on 28 September, and the first meeting of the Technical Direction Team on 28-29 September.

Further details

The technical direction of the Project is provided by a Technical Direction Team, which consists of five international experts with experience of sorption modelling and also an understanding of the requirements of safety assessments of radioactive waste disposal systems.

The project will consider the modelling of a number of systems relevant to safety assessment including:
  • geosphere systems – complex natural minerals and the associated single mineral components;
  • engineered systems – both bentonite and cement.
Evaluation criteria will include:
  • quality of "fit" to measured sorption data;
  • chemical plausibility;
  • complexity of input dataset and number of fitted parameters;
  • range of applicability of modelling approach, e.g. pH 6-9 or 9-13, and a range of ionic strength.

A total project timescale of 24 months is envisaged, with an intermediate milestone after the first six months. This milestone is considered important to allow an assessment of the viability of the project based on existing datasets. If there are insufficient datasets that are suitable for this type of detailed modelling exercise, the project will be ended.

The following twelve organisations from ten Member countries are participating in this project:

ANSTO, Australia;
RAWRA, Czech Republic;
POSIVA, Finland;
ANDRA, France;
JNC, Japan;
CRIEPI, Japan;
ENRESA, Spain;
HSK, NAGRA & PSI, Switzerland (participating jointly);
NIREX, UK; and