In the early years, the main focus during dismantling of the WAK plant was to empty the process building. Once the decision was taken to prepare the HAWC on site for storage in a final repository, the Karlsruhe vitrification facility (VEK) had to be set up and put into operation. All of the high active waste concentrate from the WAK plant was prepared for storage in a final repository at the VEK. The resulting waste packages were packed into Castor canisters and, in 2011, were transported to Greifswald to the interim storage facility of the then Energiewerke Nord. This step allowed the radioactive inventory of the WAK plant to be reduced by approx. 99%. Now dismantling of the HAWC storage buildings has become the focus.
The process building contained all the equipment necessary for reprocessing. Its disassembly began in 1996. Depending on the dose rates at the work site, the equipment was disassembled either manually or on a remote basis. Remote disassembly of the process cells was conducted from the cell hall situated above. Pipes, containers and other parts of the facility were broken down on site and placed in barrels or – if possible – packaged in containers in a fully assembled state and transferred to KTE’s disposal facilities for further treatment. So far, roughly 3,500 tons of residual substances (plant components, concrete, cable etc.) have been removed.
The main process installations were removed at the end of 2002. This was followed by extensive work on the building structure that has not yet been completed. This work involves radiological decontamination and, to a greater extent, conventional decontamination in the form of PCB and asbestos removal. During this process, more than 200 concrete blocks with pipe openings have been sawn out so far and approx. 4,400 tons of dismantled material removed. In addition, a large part of the wall and ceiling coatings with radiological or conventional contamination were removed and a large number of Rawlplugs taken out.
The four containers formerly used to store the high active waste concentrate are to be found within the WAK plant in thick-walled concrete cells of two adjoining storage buildings. These storage containers, each of which have a capacity of approx. 60 m3, were emptied and rinsed out towards the end of the vitrification operation. They are now being disassembled. Because of the high dose rates in the cells and on the containers, only remote-operated tools and equipment are being used. As the cells with the large storage containers can only be accessed from the same level, dismantling there is being carried out horizontally. A new building was erected to deal with the residual substance logistics and remote operation of the equipment; access to the storage buildings from there was created.
The basic equipment used for remote horizontal disassembly is a commercially available and electrohydraulic small digger that was adapted for the specific operational conditions. A single-arm manipulator system carrying various tools, such as an angle grinder, stone saw and hydraulic shears, can be attached by remote operation. For concrete demolition work, equipment such as a concrete milling machine and a chisel can be attached to the digger. Preparations for dismantling the first of the four storage containers began in 2015. This involved cutting up a 1.5 m thick wall on a remote basis. A special tool was used to remove the sawn-out block, which weighed roughly 30 tons. It was broken down into transportable chunks in the room in front of the container.
Disassembly of the first large storage container was completed in spring 2018. Step by step, the three remaining containers are also being dismantled.
In the LAVA storage building, cells containing contaminated HAWC process components are also to be found above the storage tank. These cells have hatches leading to the crane hall above. Remote dismantling here is conducted vertically. A redesigned version of the technique used in the process building is being used here. The manipulator carrying system is placed above the respective cell opening by crane.
As far as possible, the containers in the cell are being removed whole. The handling processes were trialled on a test stand and the necessary adjustments made to the equipment. The results from the testing, which was completed in 2013, were given direct consideration during detailed planning of the actual disassembly in the LAVA cells. This work began in the summer of 2015.
Release of all buildings from the requirements of the German Atomic Energy Act
Following complete decontamination of the buildings, the remaining auxiliary facilities such as the ventilation and radiation protection instrumentation will be dismantled step by step. Extensive radiological measurements will follow to demonstrate that the required radiological clearance values have been met on all building structures. Only then can the buildings be released from the requirements of the German Atomic Energy Act.
The final step of the dismantling process will be to conventionally demolish all the buildings. The site’s recultivation will mark the end of the “WAK plant dismantling project”.