Investigations in VESPA II are related to the following topics:
- Analysis of the instantaneous release of 129I from high radioactive waste products (inventory, instant release fraction, chemical release form).
- Determination of the relevant mechanisms for retention and immobilization of reduced radionuclide species (I, Tc, Se) on/in primary and secondary mineral phases in the near field. Especially layered double hydroxide compounds and magnetite are investigated. Retention processes will be quantitatively specified.
- Experimental investigation and spectroscopic analyses for the development of process understanding at molecular level and derivation of suitable chemical models.
- Determination of thermodynamic data (solubility products, complex formation constants, activity coefficients) for caesium and reduced selenium, iodine and technetium species.
- Preparation of data for possible later inclusion in national (THEREDA) and international data base projects (NEA-TDB).
- Identification of geochemical conditions in the near field during developments in repositories of clay and salt formations, which will serve as a basis for further mobilization and dispersion calculations in VESPA II.
- Improvement of safety analysis tools by incorporating updated and robust solubility limits and sorption coefficients for the elements Cs, I, Tc and Se. Reduction of uncertainties in long-term safety analyses, based on an improved understanding of the relevant radionuclide geochemistry.