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Most of the development in nuclear power in the past 30 years has gone into water-cooled reactors. As government funding has dwindled, development of promising alternative systems has lapsed in most countries. Although gas-cooled reactors have had a very good safety record, many have not been able to compete on economic grounds, mainly because of poor operating records and/or high infrastructure costs. Since broad-based construction has not been achieved, gas-cooled reactors have not benefited from cost reductions in the learning curve. The realization that nuclear energy will need to contribute to future power production expansion and the reduction of greenhouse gases has led to the resurgence of interest in safer and more economical ways to produce nuclear energy. One of these alternatives is the high-temperature gas-cooled reactor, as exemplified by the pebble-bed modular reactor (PBMR) being developed in South Africa. This direct-cycle, low power density design is based on clustering modules of modest power output into flexible power plants. Economic targets can be met through simplification by dispensing with the need for extensive back-up safety systems and high plant availability due to on-power refuelling and low-maintenance equipment.

Decomposition of a cellulose fleece in nanofibrils with diameters ranging from several nm to around 30nm could be realized by establishing a two-step process: the dispersion in sodium hydroxide solution followed by a mechanical dissociating step. This is supported by the crystal structure analysis, which indicates, with a refined crystallite size in the range of the fibril diameter, the decomposition of the cellulose in nanofibrils. The fiber length was largely preserved

The frictional contact between grinding bodies is determined by a characteristic course of the coefficient of friction. This periodic course can be transferred by a fundamental energy approach in the occurring energy of friction wherein the maximum is located in the rising half and the minimum in the dropping half of one contact zone. Crucial influencing variables are the ball diameter as well as intrinsic effects