The immobilization of technetium dissolved in salt brines, which are in contact with simulated spent fuel and HAW glass packages, has been studied under aerobic conditions at room temperature. The retention effect of spent fuel packages has been investigated by adding U0 2 , hull (zircaloy-4) and container material (iron) in appropriate ratios to NaCl-and MgCl 2 -rich salt brines containing an initial TcOi concentration of 10" 5 mol/L. The time dependence of the Tc concentration, pH and Eh has been measured simultaneously. Analoguous investigations have been carried out with borosilicate HAW glass. According to this scenario, container material (stainless steel) has been added to the salt solutions. In the system simulating the disposal of spent fuel, the Tc concentration decreases to less than 10~8 mol/L within 50 days, while in the system simulating the disposal of vitrified HAW, the immobilization of Tc is less efficient. In the latter case, even after 500 days there are still about 50-80% of the initial Tc dissolved. In both systems the addition of sulfide has a positive influence on the immobilization of Tc. The results are discussed in terms of reduction of Tc(VII) to sparingly soluble Tc(IV) hydrous oxide, sorption of technetium and precipitation of Tc 2 S 7 .

Extremely hard, wear-resistant SiC-bonded diamond materials with diamond contents of approximately 45% to 60% by volume can be prepared by pressureless infiltration of shaped diamond compacts with silicon. Components with large dimensions can be produced as graded or ungraded materials. Graded components are composed of Si-infiltrated SiC base materials with diamond-SiC composite layers of 0.1 mm to several mm in thickness in regions with high loading. This creates the possibility of producing low-cost, wear-resistant components of various geometries and dimensions with bending strengths of 400–500 MPa, hardness values of 48 GPa, and fracture toughness levels of 4.5–5 MPa∙m1/2 for use in extreme wear conditions. Thermal conductivities of up to 500 W/mK were obtained, render these materials interesting for heat sinks

No abstract

No abstract

No abstract