Hot cells HZ
Hot cells (HZ) were used to examine materials irradiated in reactors. Fuel assemblies, fuel assembly samples and structural materials were analysed by physical and chemical means there. At the heart of the facility were five concrete cells that were supplemented by various lead cells. All kinds of different experiments could be set up in the cells, which were equipped with lead glass windows, manual manipulators, heavy-duty manipulators and various sluice systems. Further studies were carried out in a separate section of the laboratory, such as scanning electron microscopy. This section was also where decontamination and workshop work took place. The facility is subdivided into three distinct sections. In early 2010, the company formerly known as WAK GmbH and today known as KTE was entrusted with dismantling sections one and two as the sole licence holder pursuant to § 9 of the Atomic Energy Act (AtG). The third section is still operated by KIT as a fusion materials laboratory and has been separated from the other two sections in technical and construction terms.
Dismantling of the hot cells
The licence for dismantling the hot cells was granted in 2010. During the course of several dismantling steps, all activities have taken place since then, up to and including the clearance procedure pursuant to § 29 of the German Radiation Protection Ordinance and demolition of the buildings.
Before disassembly began, the building infrastructure was adapted to meet the requirements for dismantling. A full body monitor at the exit from the controlled area was installed, as was an airlock for inward and outward containers and large-scale components.
The five concrete cells are being dismantled according to a standardized procedure. First, the cell interiors are decontaminated on a remote basis with a view to reducing the existing dose rates to a level that allows manual work to be carried out in the cells. After measuring and evaluating the remaining dose rate, the next step of the dismantling process is to gut the cell interiors manually, strip the coatings and disassemble the steel linings and wall ducts of the cells.
Personnel airlocks with a supply of breathing air were installed at the entrance to the concrete cells. A dismantling booth was set up in the crane hall above so that cell installations can be removed through an airlock, and for the dismantling of the steel linings in the cells. Additional enclosures were erected for the removal of the lead glass windows and access plugs. The booth and the enclosures are set up as the dismantling process requires.
The dismantling team works its way from one cell to the next. One major challenge of this dismantling project is that the five cells exhibit very different levels of radiological contamination and on-site personnel must frequently be prepared for hotspots in the confined spaces. To acquire some initial concrete experience, the team began working on the least-contaminated cell 5 in October 2016. Remote-handled disassembly then followed in cells 3 and 4. Decontamination work was conducted remotely wherever possible. Radiological hotspots in cell 4 were removed by stripping the cell linings so that manual disassembly can now begin on the remaining cell elements (as per December 2018).
Following disassembly of all installations and a clearance measurement of the building structure, the building and the exhaust stack were demolished by conventional means.