In the Federal Republic of Germany, radioactive waste forms of pronounced decay heat generation shall be disposed of in deep vertical boreholes in the final repository at Gorleben site. The disposal technique for heat generation intermediate-level waste and for spent HTR fuel is under development in the R&D project, entitled "Intermediate-Level Waste and Spent HTR Fuel Element Test Disposal in Boreholes" (MHV project). The MHV project is divided in two sub-projects and is supported by the Bundesminister für Forschung und Technologie (BMFT) since 1983. In the sub-project "Retrievable Emplacement Test" (REV), supported by the Commission of the EC, an emplacement experiment with available waste packages will be conducted in the Asse salt mine. The objectives of the REV project are to characterize the available waste packages within a hot cell investigation programme at KFA, to demonstrate basic handling and emplacement operations, to show that emplacement in boreholes can be operated safely with respect to radiation protection, to investigate the interactions between waste packages, borehole atmospheres and surrounding salt rock by monitoring, and in particular, to study the effects on gas release and generation. The duration of the emplacement experiment itself intended to be up to a maximum of five years. N.B. In December 1992 the BMFT postponed the project.
Apart from demonstrating that radioactive wastes can be safely handled under real mining conditions, the objective of this programme is above all to demonstrate that during storage no circumstances arise which could cast doubt upon safe operation of storage boreholes. In addition, it will be possible for the first time so study the effects of gas release from wastes into a final repository borehole.
The retrievable emplacement test with intermediate level waste (ILW) and spent high tension reactor (HTR) fuel element packages will take place in three vertical boreholes of the Asse salt mine. The drift was driven, the boreholes were drilled and partially instrumented, and the main components were fabricated in parts during previous phases of the project. Installation of the borehole internals and fabrication of all components have nearly been completed. Inactive system tests have successfully been performed to check the interactive function of all major handling components.
1. Preparation of the experiment
1.1 Coordination of work between GSF and KFA
1.2 Assembly, installation and test of components
1.4 Installation of radiation protection instruments
1.5 Staff training for emplacement and retrieval
2. Implementation of the experiment
2.1 Coordination of work between GSF and KFA
2.2 Transport of the waste packages to the Asse mine
2.3 Emplacement of the waste packages
2.4 Measurement of dose rate, temperature, gas composition and borehole convergence
2.5 Maintenance of equipment
2.6 Radiation protection measurements
2.7 Staff training for retrieval