Endlagerung radioaktiver Abfälle

Shales, granites and rock salt are currently under investigation as host rocks for radioactive waste. With respect to heat‐producing waste (spent fuel, high‐active waste) these rock types comprise contrasting mechanical and chemical behavior. The differences are due to the respective geological formations: Shales form by slow accumulation of fine‐grained minerals from seawater with subsequent compaction and diagenesis; crystallization of deep‐seated magmas at 700 to 850°C is the process that generates granitic rocks in the upper 20 km of the earth's continental crust; rock salt is a chemical sediment which forms by precipitation of chloride and sulfate minerals from seawater evaporation in shallow marine basins under arid conditions. The extent of chemical reactions between granitic rocks and migrating saline fluids upon canister‐induced heating is quite small. However, thermally induced reactions between sheet silicate minerals in shales may result in a gradual loss of adsorption capacities for released radionuclides. Canister‐induced temperature gain in rock salt results in increasing creep rates which lead to an enhanced enclosure process. Great care has to be taken in the selection of salt formations as host rocks with respect to brines; depending on their composition and temperature brines might react with e.g. potash‐seams.     

Endlagerung radioaktiver Abfälle

This is the first in a series of three papers which introduces the issue “disposal of radioactive waste” and identifies related societal and scientific questions. Types and amounts of waste to be disposed of are presented. The authors describe the disposal options discussed in the past and argue in favour of the concept of disposal in deep geologic formations which does not require any follow‐up maintenance. They explain the basics of disposal concepts in crystalline rock, clays and claystones, and in rock salt.     

Endlagerung radioaktiver Abfälle

Chemical processes become relevant in a nuclear waste repository if water accesses the disposal area. The extend of potential radionuclide releases is determined by a variety of radio‐, geo‐, and biochemical reactions. Radiolysis and corrosion of waste form, container, and backfill material influence significantly the chemical environment in close vicinity of the waste form. Released radionuclides interact in the farfield of a repository with dissolved and colloidal groundwater constituents and react with mineral surfaces. For the safety case of a nuclear waste repository, the chemical behavior of radioactive waste components is elucidated and reactions are quantified by the derivation of thermodynamic data.     

Successful Decontamination of 99TcO4− in Groundwater at Legacy Nuclear Sites by a Cationic Metal‐Organic Framework with Hydrophobic Pockets

⁹⁹Tc contamination at legacy nuclear sites is a serious and unsolved environmental issue. The selective remediation of ⁹⁹TcO₄^? in the presence of a large excess of NO₃^? and SO₄^2? from natural waste systems represents a significant scientific and technical challenge, since anions with a higher charge density are often preferentially sorbed by traditional anion‐exchange materials. We present a solution to this challenge based on a stable cationic metal‐organic framework, SCU‐102 (Ni₂(tipm)₃(NO₃)₄), which exhibits fast sorption kinetics, a large capacity (291 mg g^?1), a high distribution coefficient, and, most importantly, a record‐high TcO₄^? uptake selectivity. This material can almost quantitatively remove TcO₄^? in the presence of a large excess of NO₃^? and SO₄^2?. Decontamination experiments confirm that SCU‐102 represents the optimal Tc scavenger with the highest reported clean‐up efficiency, while first‐principle simulations reveal that the origin of the selectivity is the recognition of TcO₄^? by the hydrophobic pockets of the structure.     

Converting Thioether Waste into Organic Semiconductors by Carbon–Sulfur Bond Activation

A goal for human society is to convert organic waste into valuable materials. Herein, 2‐(methylthio)‐bezothiazole (MTBT), an important organic waste in urban runoff, was catalytically converted into a series of organic semiconductors through carbon–sulfur bond activation. The efficient conversion of various substrates with different aromatic moieties and reacting functional groups (tin and boron) proved the generality of this novel diarylation Liebeskind–Srogl methodology. Moreover, the resulting organic semiconductors showed excellent performance in field effect transistors and cell imaging. This contribution presents an excellent example of converting organic waste into valuable materials and may open a new avenue to utilizing widely available aromatic thioethers.