[en] Measurements of the absolute fast neutron fluxes and reactor power have been carried out on the critical facility KAHTER in the Institute for Reactor Development at the Kernforschungsanlage Juelich GmbH. The Once Through Then Out core loading schemes OTTO 0/5 and OTTO 5/5 for the pebble-bed HTGR were investigated. The measurement results with the threshold detectors Rh¹⁰³ and In¹¹⁵ as well as with U²³⁵-, Np²³⁷- and Th²³²-fissionchambers have been compared to calculations with the program cycles GAMTEREX and MUPO-CITATION. A further task was to check for statistical effects of the pebble-bed loading on the consistency of the measured values. Experiments with fast fission chambers were also performed to investigate the detectibility of various flux perturbations in the upper core region by means of a detector system in the top reflector. (orig.)

[en] The objective of the Active Handling Experiment with Neutron Soruces was to investigate radiological aspects due to backscattered neutrons when spent fuel and high level waste will be handled in the drifts of an underground repository located in a salt dome. As neutrons play an important role in the direct disposal option, main emphasis was laid on their contribution to the total dose equivalent rate. The radiological exposure caused by direct neutrons and neutrons scattered by the salt rock during handling processes of POLLUX packages and shipping packages was simulated and experimentally analysed with the help of the AHE package. The AHE shielding cask was filled with one Cf-252 line source in order to simulate the neutron fields of a loaded POLLUX cask and a shipping cask loaded with a fuel element canister with respect to neutron energy distributions and local dose equivalent rates. The results of the AHE experiment provided valuable contributions for a better understanding of radiological aspects during handling spent fuel/high level waste in an underground repository. Validated computer codes are available now which make it possible to minimize the occupational dose. (orig.)

[en] The objective of the Active Handling Experiment with Neutron Soruces was to investigated radiological aspects due to backscattered neutrons when spent fuel and high level waste will be handled in the drifts of an underground repository located in a salt dome. As neutrons play an important role in the direct disposal option, main emphasis was laid on their contribution to the total dose equivalent rate. The radiological exposure caused by direct neutrons and neutrons scattered by the salt rock during handling processes of POLLUX packages and transfer packages was simulated and experimentally analysed with the help of the AHE package. The AHE shielding cask was filled with one Cf-252 line source in order to simulate the neutron fields of a loaded POLLUX cask and a transfer cask loaded with a fuel element canister with respect to neutron energy distributions and local dose equivalent rates. The results of the AHE experiment provided valuable contributions for a better understanding of radiological aspects during handling spent fuel/high level waste in an underground repository. Validated computer codes are available now which make it possible to minimize the occupational dose. (orig.)

[en] Under the programme for direct ultimate disposal of spent fuel elements, the active handling experiment with neutron sources aims at investigating the underground radiological problems due to direct neutron radiation scattered at the salt rock when handling POLLUX casks and single-element casks. Therefore, radiation exposure of the operating personnel may essentially be determined by neutron emission. The share of neutrons in the dose rate increases when handling WAU and MOX fuel elements. Therefore investigations into radiation exposure to neutrons in an ultimate underground repository are of special importance. Such investigations are carried out at the Asse salt mine of the GSF. (orig.)

[en] The current status of activities and experience gained and the basic features of the SELDA system are explained in connection with the task of giving proof of the reliable functioning of systems for safe stopping of hoisting equipment running at undue speed. The results available are used to establish the design principles and data for a shaft hoisting equipment for a payload of 85 t. The system designed according to preliminary test results for ascertaining the required stopping power and its behaviour in the project tests is described, as well as the planned test performance, and the results and their evaluation. The stopping tests with the SELDA system, accompanying materials studies for improvement of the SELDA conveying belts, and further tests investigating the dependence of stopping power on a variety of parameters is reported along with results on the applicability of test results in a design study. (orig./HP)

No abstract available

[en] For the pebble-bed-HTGR it is essential to know exactly the fast neutron dose of the graphite reflectors. Due to this value it has to be decided whether the reflectors will stand the whole reactor life-time or whether provisions are to be made to exchange reflector parts with high neutron irradiation damages. Therefore, in the critical facility KAHTER benchmark experiments for estimating fast neutron fluxes and doses were performed. These investigations include an accurate prediction and evaluation of the fast neutron fluxes with the HTGR-computer code system GAMTEREX normalized to the KAHTER-power

[en] Measurements were effected to predict the radiation damage in an 'OTTO'-core (OTTO=Ounce Through, Then Out) simulation in the critical facility KAHTER. The method adopted was the reaction rate measurement in Rh-foils which covers the energy-region from 0.01 MeV upwards; the neutron density was determined for neutrons above 1.2 MeV by fission rate measurements in Th-foils in connection with fission track recorders. The radial and axial fission rates measured in various channels are given

[en] Numerous disposal concepts have been investigated for the disposal of high-level wastes from reprocessing as well as direct disposal of spent fuel elements. This research and development work included the evaluation of the radiation exposure of the repository workers as a result of direct as well as scattered radiation experienced while handling the sources during emplacement in a repository. The transport and disposal underground were assumed to be either in POLLUX casks or in the case of consolidated fuel rods (cut to length to fit) in thick walled canisters, similar in dimensions to the canisters for vitrified HLW. These canisters and casks are to be transported underground in a transfer cask and disposed of in boreholes. The ''Active Handling Experiment with Neutron Sources (AHE)'' is a demonstration test to investigate the above mentioned radiological aspects of handling spent fuel and vitrified high-level active waste. Neutron dose rates are measured resulting from direct radiation and from neutrons scattered by the surrounding host rack (rock salt). The MORSE-SCG computer code and model calculations are verified by these demonstration tests. Thus, an experimentally validated tool will be available for future detailed repository design with emphasis on minimizing the radiation exposure of the operating personnel

[en] Published in summary form only