Numerische Untersuchung der 3-dimensionalen stationärenTemperatur- und Strömungsverteilung im Core eines Kugelhaufen-Hochtemperaturreaktors

This work presents a computer model determining the steady-state temperature- and flow field in 3 dimensions in the core of a pebblebed high temperature reactor. The numerical sprinkler method, basing on the THERMlX-model, allows to describe the thermo-hydraulicsof a non-rotational-symmetric core-geometry. The AVR-reactor in Jülich, in operation since 1967, represents a suitable investigation-object for the computer model of THERMIX-3D. It is in a 3D-mesh-structure to reproduce very precisely the so called "graphite noses", in which the shut-down rods are conducted as well as the filling cones in the inner and outer area. The results of the final calculation of the normal operation condition for the AVR-reactor unambiguously show, that within the core reproduced in 3 dimensions there are evident deviations in the flow profile and in the temperatures of the cooling gas in contrast to a 2D-handling

PANAMA : ein Rechenprogramm zur Vorhersage des Partikelbruchanteils von TRISO-Partikeln unter Störfallbedingungen

The computer code PANAMA and its underlying modeling assumptions are presented. The models are based on independent measurements of the properties of TRISO particles with a SiC interlayer. Essential features are the calculation of internal gas pressure, of coating strength and its decrease during irradiation and its weakening due to fission product interaction during accidents. At very high temperatures, particle life is determined by SiC thermal decomposition. Good comparison is obtained in the temperature range 1600 - 2500 ° C when applying PANAMA to a wide variation of existing accident simulation experiments with spherical fuel elements. At lower temperatures, PANAMA tends to be over-conservative. Predictions of particle failure during the depressurized accident sequence with the worst temperatures of the 200 MW$_{th}$ , side-by-side Modular Reactor System remain below the level of normal operations. The same holds true for the HTR-500 MW$_{e}$ accident sequence with the system under pressure. In the depressurized case, however, failure of all particles has to be expected after approximately 100 hours in the least favourable core position

Considerations on hydrogen as a future energy carrier and its production by nuclear power: an overview compiled

1. Introduction: In 1996, the $\textit{world's consumption of primary energy}$ amounted to 8380 MTOE, where 90 % originated from fossil fuels and the remainder from nuclear power and renewale energies. Currently hydro (20%) and nuclear (17%) are the only significant non-fossil contributors to electricity production. Burning hydrocarbons means liberation of carbonoxide gases with undesirable side effects: CO$_{2}$ is currently labeled as one of the primary causes of the $\textit{greenhouse effect}$. The second thought on hydrocarbons is its limited supply on earth. The future energy supply mix will depend on the magnitude of the demand growth, changing objectives and social priorities, and the technologies to meet them. A strong demand for more energy (plus 1,6 %yr) is expected, but no significant change in the world's energy-mix. Facing future with an arrayy of options and flexible strategies is recommended. Limited resources of fossil energy resources and pending environmental issues are likely to increase the significance of non-fossil energies - water, nuclear, solar, wind, geothermal - in the long run. $\textit{Nuclear power}$ is considered by many to be the most promising CO$_{2}$-free energy technology. Principally used as a base load power plants, nuclear off-peak electricity could be taken for $\textit{hydrogen}$ production. Nuclear hydrocarbon refinement and conversion contributes to fundamental objectives of energy policy: energy security, saving of resources, protection of the environment. In a future low-emission energy economy, the energy carrier hydrogen could become a strong contender using its advantages compared to other elternatives