Two mobile roofs are under erection on the site of the National Disposal Facility for Low- and Intermediate-level Radioactive Waste (NDF), one on each of the two rows of cells for disposal of reinforced concrete containers with radioactive waste. Their installation is a crucial stage in the construction of the disposal facility. The mobile roofs protect the RAW packages against external atmospheric conditions during the process of filling the cells and during the construction of the roof plate of each cell. In addition, they will protect the employees during implementation of disposal operations, as well as the plant and control equipment located under the mobile roofs.
Construction of the mobile roof over the northern row of disposal cells began at the beginning of June. It is currently complete as a structure. Installation of the crane, instrumentation and control systems thereof and the side closing metal walls are to be implemented. The roof over the southern row of disposal cells is at structural construction stage.
The imposing assembly is a steel structure of 12 columns, 25 metres wide and 30 metres long, and weighs approximately 700 tonnes. The assembly completely covers the currently manipulated disposal cell and 1/3 of the two adjacent disposal cells. After filling the corresponding disposal cell, the mobile roof is moved forward on a rail track mounted longitudinally on massive foundations on both sides of the row of disposal cells. The stacking operations of the reinforced concrete containers of radioactive waste in the disposal cells will be carried out remotely using a 30-tonne overhead bridge crane mounted inside the mobile roof, using a waste package gripper and will be controlled remotely via SCADA monitoring and control system. Thereby, SERAW protects its own personnel by minimizing dose uptake in accordance with the ALARA* principle.
All systems needed to operate the assembly prior to its commissioning are subject to technical supervision and tests.
*ALARA (As Low As Reasonably Achievable) – one of the main criteria formulated as early as 1954 by the International Commission on Radiologic Protection in order to minimize the harmful effects of ionizing radiation. It envisages maintaining the lowest possible achievable level of both individual (lower than the limits established by the effective regulations) and collective exposure doses, taking into account social and economic factors.