DECOMMISSIONING | DISMANTLING LARGE COMPONENTS


Above left: The working platform


Above right: Control and monitoring of the cutting process in the control room


V After the RPV has been dismantled and packaged, the RPV and the reactor building are in the final state


conditions as follows: ● The RPV components are removed from their installation positions, dismantled, and handed over to the customer in accordance with the approved disposal method,


● The contractor’s equipment as well as any machines and devices used by the contractor are removed from the dismantling area (clearance measurements and release are carried out by the customer; material that is not cleared is handed over to the customer as radioactive waste),


● Any enclosures or seals created by the contractor for ventilation purposes have been dismantled and disposed of by the contractor,


● The waste containers and the associated documentation have been handed over,


● Other components that do not require final disposal packaging have been packaged according to the existing requirements and handed over to the customer,


● At the customer’s request, the resulting open edges (especially the reactor cavity) are secured by the contractor by means of railings. Edges are also secured during the construction phase in accordance with the relevant safety regulations.


● Any other requirements and safeguards related to the work areas are prepared and carried out by the customer accordingly.


Pre-segmentation Based on the pre-segmentation design and the associated cutting plan, the RPV is dismantled using the following work steps:


● Segmentation of the pool sealing The segmentation is carried out by means of a plasma cutting system and/or an angle grinder, a saw or similar tooling.


● Removal of insulation per ring segment The insulation is removed manually in the pre- segmentation phase in-situ using a shielded working cage and required pole tools (handling bars). The removed insulation bricks and metal structures are segmented again


32 | February 2023 | www.neimagazine.com


at a separate location and are assigned to their appropriate disposal route or packaged in such a way that they can be loaded into designated containers.


● Marking for flame cutting start holes To perform thermal cutting, start holes need to be drilled first. The positions of the start holes are marked with the help of a marking module which is guided by the arms of the lifting beam.


● Drilling of start holes Start holes are drilled by a specially developed drilling device. The drilling device moves from the inside to the outside. The process is carried out remotely and is controlled and monitored from the control room.


● Cutting of ring segments The tool platform (also called the ‘working platform’) is positioned on the RPV ring by means of the lifting beam and the reactor building crane, and lifting holes are cut using the flame cutting method. These are used by the lifting beam to lift out the RPV ring segment after the final horizontal separation cut. To do this, the tool platform carries the guide system for the cutting system, which is used to perform the circumferential separation cut remotely. The reactor pressure vessel is pre-segmented one section after another from top to bottom. The tool platform is also used to extract the smoke produced during the separation cut.


● Lifting out ring segments and the calotte After the final cut, the tool platform is removed and placed in the storage position. The ring segment is then lifted with the help of the lifting beam and placed at a cleaning location in the pre-segmentation area. The RPV ring segment is cleaned on the outside to remove any possible residues.


The dismantling activities on the RPV within the pre- segmentation area are completed with the removal of the calotte, as well as the subsequent removal of the support frame and the remaining control drive parts. The post- segmentation of the RPV rings into segments suitable for packaging takes place in the post-segmentation area. U


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