[en] In consideration of its use in an ultimate repository for nuclear waste in a mine, the mechanical properties of salt concrete are of particular importance, but so are its gas permeability and structure after stress. The investigations were carried out not only on salt concrete samples which hydratised under normal conditions, but also on sample blocks which had been subjected to deformation prestressing after hydratisation, in order to create pronounced flow structures. This was intended as a simulation of in-situ deformation resulting from extreme strain. The cement matrix and the rock salt additive show marked creep and indicate similarities with rock salt. The binding agent/additive compound is maintained intact, and the two components remain firmly bonded together even after major deformation, cracking only when rupture mechanics set in. Higher strain leading to slip and deformation of the additive shows that the cement matrix follows the distortion of the salt grains. The monoaxial compression strengths between rock salt and salt concrete are very similar, although salt concrete achieves higher values. The permeability of salt concrete is lower but comes close to that of rock salt when compacted. The results show that salt concrete appears to be a suitable construction material for the buttress of a dam structure in a nuclear waste repository. (orig./MM)

[en] The invention has been aimed at a procedure for the nuclear fuel shattering from organic solutions containing nuclear fuel in order to produce pellets. The procedure is also applicable to less crystallizing nuclear fuel compounds and ensures a direct fuel shattering without a preceding backwash. The organic solution containing nuclear fuel is percolated by an ammonia solution

[en] Short communication

[en] A radiation protection concept was worked out for final storage of spent fuel elements. It contains the areas of instrumentation and equipment with the necessary devices and measuring equipment for monitoring emission and the room air, personnel dosimetry, measuring contamination, local dose rate measurements and division into radiation protection areas. The barrel incoming inspection is described. The work for determining the radiological load of the operating staff and the environment for correct and incorrect operation is also described. The radiological load of the operating staff for correct operation was determined in the form of the collective dose with dose factors in accordance with ICRP and individual doses according to Radiation Protection Ordinance. The collective dose is 0.28 pers. Sv/a and the maximum individual dose remains below 1.0 E-2 Sv/a. The individual doses determined remain below the permitted limits of Radiation Protection Ordinance. In the context of accident analysis, it was found that no accidents occur, which load the operating staff radiologically above the permitted limits of the Radiation Protection Ordinance. A probability consideration of accidents shows that the accident risk of the operating staff is several orders of magnitude below that of the normal operating risk. (orig./HP)

[en] The mine for the accommodation of spent fuel elements differs basically from an ultimate storage site of integrated waste management by the following aspects: larger and heavier ultimate storage compounds; higher level of radiotoxicity of the waste and larger quantity of heat giving into the storage site. The ultimate storage compounds are self-shielding; they are moved but horizontally, i.e. no tilting is required; they are positioned in the tunnels. The handling equipment required for this purpose have been proved above ground but not underground. The higher level of radiotoxicity can be taken into account by technical measures. The thermal design takes into consideration the larger quantities of heat involved in direct ultimate storage, so that the same level of rock mechanics stability will probably be achieved. (orig./PW)

[en] The non-variable basis for planning was an annual quantity of radioactive waste for disposal consisting of 700 tonnes of heavy metal and 1 million spherical fuel elements. The variable planning specifications were: the ratio of radioactive waste from integrated disposal with reprocessing to directly disposable wastes; the cooling and interim storage times for highly radioactive waste from reprocessing and LWR fuel elements from nuclear power plants, and conditioning methods. The variation of these parameters produces differing construction designs for handling facilities and stations for waste containers in the overhead facilities, and also different dimensioning for the shafthead gear. These are described alongside all the other buildings not dependent on the variables. Taking into account technical feasibility, relation exposure of personnel and the costs, an assessment is made of the different planned facilities. (orig./HP)

[en] The invention should ease the process of enclosing containers which contain radio-active material. A sliding tensioning arrangement is proposed, which can be clamped, and there is a container insert between this tensioning arrangement and the lock bar. The threee above-mentioned parts can be coupled up or uncoupled. The tensioning arrangement is preferably made as a pair of pliers surrounding the container. It is advantageous if the shielding container does not have to remain connected by a flange during the locking process. (UWI)

[en] A new bolting device is created for this bottom slide, which makes it possible to cut the time spent by the staff in the vicinity of the transportation container considerably when operating the locking bolt. This is achieved by means of a mechanism making it possible for all the locking bolts to be opened and shut at the same time from one single operating station. All locking components are integrated into the sliding gate and form an internal lock. (orig./HP)

[en] Short communication

[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.)