RD&D-Programme 2004 - SKB

A research programme to study cast iron corrosion products and their interaction with oxidized
radionuclide species under anoxic conditions has been started in cooperation with Nagra.
An accurate experimental method has been developed to achieve completely oxygen-free
conditions. A typical study of the interaction between tetravalent selenium and iron started
with corrosion of iron in oxygen-free solutions at room temperature. After several months,
the corrosion products were examined by various spectroscopic methods (XRD, SEM-EDS,
TEM and Raman spectroscopy). After addition of tetravalent selenium, the kinetics of selenium
reduction were followed by analyses of the solution at different points in time. Finally, the
iron surface was examined after the test by spectroscopic methods, which also included X-ray
absorption spectroscopy (XAS) to identify and speciate selenium adhering to the surface.
Preliminary results from the XAS characterization have been published /15-52/.
SKB is participating actively in the OECD-NEA project TDB (Thermodynamic Data Bases),
where quality issues concerning the use of thermodynamic databases in safety assessment are
continuously discussed /15-53 and 15-54/.
Programme
A new calculation of radionuclide solubility is being done within SR-Can. The main purpose
is to obtain a better assessment of uncertainties and sensitivities, particularly with respect to
variations in the composition of the groundwater and the bentonite’s pore water. Activities
for improving database quality are planned within the framework of the NEA TDB project.
Solubility studies of plutonium dioxide from undersaturation in water-saturated solutions will
be compared at Chalmers University of Technology.
Studies of redox kinetics for different oxidized forms of radionuclides (including hexavalent
selenium and heptavalent technetium) on fresh and corroded iron surfaces will be carried out in
cooperation with Nagra and within the EU project NF-Pro. Geochemical modelling of kinetic
data will be carried out, and based on all data conclusions will be drawn regarding radionuclide
retention.
15.2.15 Helium production
Alpha particles (helium nuclei) from alpha decay in the fuel form gaseous helium.
Conclusions in RD&D 2001 and its review
In RD&D 2001, it was deemed that the field did not require any further research, development
or demonstration, but that developments in the field would be monitored and acted on when
appropriate.
Newfound knowledge since RD&D 2001
No new knowledge has been forthcoming.
Programme
SKB makes the same assessment in RD&D 2001, that the field does not require any further
research, but that developments should be monitored in case new activities are called for.
182 RD&D-Programme 2004