Neckarwestheim: Both units are undergoing decommissioning
The Neckarwestheim nuclear power plant is located ten kilometers south of Heilbronn on the site of a former quarry directly on the Neckar River. There, we generated a total of over 576 billion kilowatt-hours of electricity using two pressurized water reactors - Unit I from 1976 to 2011 and Unit II from 1989 to 2023. Both units at the site are now undergoing decommissioning: GKN I since 2017 and GKN II since 2023.
We currently estimate that the decommissioning work, which is carried out under the provisions of nuclear law, will take about ten to 15 years for each unit - calculated from the start of decommissioning in each case. Once released from nuclear regulatory oversight, both units will be nothing more than conventional industrial facilities. Decisions regarding the handling of remaining buildings - such as the demolition or reuse of office buildings - can then be made.
Decommissioning of Unit GKN I
The decommissioning of Unit I in Neckarwestheim has been underway since 2017. Of the eight plants nationwide that were shut down in 2011 as part of the energy transition, GKN I was the first to begin decommissioning. This process is now well advanced: Work in the conventional turbine hall has already been completed, and in the reactor building, all major components - particularly the reactor pressure vessel, formerly the heart of the plant - have already been completely dismantled. Currently, the focus there is on dismantling concrete structures inside the building. All spent fuel assemblies have already been transferred from the plant to the state-run interim storage facility on site. From a formal standpoint, we have all the necessary permits to dismantle GKN I until it is released from nuclear regulatory oversight.
The reactor pressure vessel is the former heart of the plant, which housed the heat-generating reactor core consisting of fuel assemblies. To clear the way for the dismantling of the 240-ton vessel, its internal components first had to be removed and disassembled. This work was carried out underwater using remote-controlled, industry-proven tools - such as band saws or circular saws. The vessel itself was then excavated in one piece from its original position and dismantled into individual segments in the adjacent former spent fuel pool, also using a remote-controlled thermal cutting process.
The heat required for electricity production, which had been generated by the fuel assemblies inside the reactor pressure vessel, was transferred in the three steam generators of GKN I from the so-called primary circuit to the plant’s conventional secondary circuit. The steam produced in this process was then routed further into the turbine hall via the turbines. During the dismantling of the steam generators, the large components - each weighing nearly 290 tons and measuring 19 meters in length - were disassembled within a few weeks, lifted out of their installed positions using the reactor building crane and a special lifting system developed specifically for this purpose, and subsequently removed from the reactor building for further disassembly.
The coolant used to circulate between the reactor, steam generators, and primary coolant pumps through the primary coolant pipes. The pipes were cut using a pipe-cutting machine. The three primary coolant pumps, which circulated the coolant through the system, were each removed as a single unit.
Currently, the focus in Unit GKN I is on dismantling the massive concrete structures (“biological shield”) that formerly surrounded the reactor pressure vessel - the heart of the plant - inside the reactor building, which has already been completely dismantled. In this project, which is divided into several individual sections, a total of approximately 1,000 tons of concrete is expected to be removed. Among other tools, wire saws are being used to first cut the concrete into individual segments. These are then lifted out of their original positions using the building crane and subsequently further broken down.
In the turbine hall, generators used to convert the kinetic energy of the turbines into electrical energy. Demolition work there is already largely complete - what remains is a largely empty, gutted building.
Decommissioning of Unit GKN II
The decommissioning of Unit II in Neckarwestheim (GKN II) began in May 2023. We had received the necessary decommissioning and dismantling permit even before the plant’s final shutdown in April 2023. With this permit, all formal requirements are in place to dismantle the plant until it is released from nuclear regulatory oversight.
The first major decommissioning activities are currently focused on the primary circuit. This was a central component of the plant and ensured the transport of the generated thermal energy between the reactor and the steam generators. The main coolant lines - which were an important part of the circuit - have now been completely dismantled. The circuit is therefore no longer intact.
The first major decommissioning activity following the shutdown of GKN II was the decontamination of the so-called primary circuit. In this process, the radioactive layer on the inner surface of the pipes and components of the primary circuit was removed and extracted and collected using filters. From a radiation protection perspective, this process significantly simplifies the ongoing dismantling, disassembly, and processing of the decontaminated systems and was thus a key prerequisite for the further decommissioning of the plant.
The main coolant pipes were a key component of the primary circuit, ensuring the transport of the generated thermal energy between the reactor pressure vessel and the steam generators. The pipes, which were up to ten centimeters thick, were completely dismantled and disassembled using, among other things, a pipe-cutting machine. As a result of this work, the primary circuit is no longer intact. The main coolant pump motors, each weighing approximately 42 tons, have also been removed and further dismantled.