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[en] Extensive constructive and operational experience with the HTR line in the FRG make it possible to realize all basic types of this reactor line on a technical scale. The operational experience is based on the AVR test reactor. In ten years of operation, the pebble-bed construction and the functioning of the power-generating HTR were tried and proved, and the highest coolant temperatures ever reached in a power station were reached and maintained. This plant also helped to prove the high inherent safety potential of HTR-type reactors. The next step will be the THTR prototype now under construction and the transition to high-power HTR plants. HTR-type reactors for direct coupling with a helium turbine (HTR) and for nuclear process heat utilization are being developed and planned. (orig.)

[en] In the context of the programme for the development of gas-cooled reactors in the USSR it is reported that pilot plants with VGR-50 MW(el) and VG-400 MW(el) have been developed up to the stage of engineering design and that now the efforts are concentrated on the project of pilot-commercial reactor plant VGM (PCRP VGM) of a modular type with unit thermal power of 200-250 MW. The installation is designed to solve the main scientific and engineering problems of construction of high-temperature gas-cooled reactors, to test equipment components, and to show advantages of the given type of installations having the enhanced safety and capability to generate high-potential heat. The status of work on the PCRP VGM project is described. 3 refs, 1 fig., 1 tab

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[en] A brief description of the safety characteristics of the HTGRs (high temperature gas-cooled reactors) is made, taking into particular account the recent adaption of the gas-turbine direct cycle. An analysis of the experiments of the blow down in the full scale, made at Julich (FRG) on the AVR (Arbeitsgemeinschafts Versuch reaktor) is performed. Afterwards, the possible accidents due to to the inlet of air and water to the reactor are analysed, stressing their probabilities and consequences are: a) the presence of an always negative temperature coefficient; b) the property of the fuel microspheres to retain the fission products completely, even in the most severe accidents; c) the capacity of the core to dissipate the decay heat through passive mechanisms based on the natural laws of the heat transfer (radiation and conduction); d) the safe behaviour of the fuel and the core in the presence of chemical attacks (air and water); e) the validation of the codes used in the preliminary valuations and the demonstration of their conservativity; f) the validity of the definition of the HTGR as the only reactor to deserve made in recent scientific congresses

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[en] At present, no nuclear power plant equipped with a high temperature reactor is suitable for being introduced shortly into the European or US market, promising to rival the 1300 MW power plants, even if serval plants had been built offering all the advantages of the high temperature reactor. Variants are analyzed, and the question is dealt with, whether spherical fuel elements, the non-integrated method of construction and the prestressed cast iron pressure vessel would not, after all, offer better chances for its competitive capacity when taking into account all the requirements to be met by the reactor system. The decision concerning the choice of the reactor system is to be prepared in the course of the next months. Since such a project with its whole fuel cycle included exceeds the financial power of the individual companies, and perhaps even that one of the individual nations, close international co-operation is in the offing. (orig.)

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[en] After some general remarks on reactor development in the F.R. of Germany the present status of the THTR is described. Special attention is given to the cost development and the economic and technical advantages of this reactors - factors which are of great importance for the decision on whether the activities should be continued. (orig.)