The construction phases
The PALLAS project is being realized in phases. After the preparatory works – such as site preparation and construction of the reactor pit – the construction of the PALLAS-reactor and its associated buildings will follow. The final phase is commissioning. Below you can see the key steps in the development of the project.
Lay down
area
Pit &
Foundation
Construction phase
Commissioning
Lay down area
In the first phase of the project, the construction site was prepared. The works began in the second half of 2022 and included the demolition of existing buildings and above-ground infrastructure, the removal of underground cables, and the rerouting of gas pipelines. To ensure site safety, temporary retaining walls were installed. These provide stability, prevent subsidence or landslides, and enable the safe delivery and storage of construction materials.
The opening of the entrance road in December 2022 marked a successful completion of the first phase.
Overview of activities in the Lay down area phase
- Removal of original buildings.
- Removal of above-ground infrastructure.
- Housing and parking possibilities.
- Removal of underground cables and pipes.
- Redirection of gas pipeline.
- Removal of the tritium installation
- Partial flattening and excavation of the current dike.
- Installing temporary retaining walls.
- Opening of the access road for construction traffic
Pit & Foundation
To enable the construction of the PALLAS-reactor building, the construction pit has been realized. The hole of approximately 50 metres by 50 metres and 21 metres deep has been using advanced construction techniques. The construction pit lays the foundation for the construction of the PALLAS-reactor building and helps fitting the building in with the dune landscape.
Overview of activities in the Pit & Foundation phase
- Preparation of the work area
- Installation of diaphragm walls
- Placement of capping beams
- Anchoring
- Excavation of the construction pit
- Drilling screw injection piles
- Application of soil improvement
- Application of underwater concrete
- Pumping out water from the construction pit
- Installation of the bearing slab
- Cleaning of the work area
Construction phase
In June 2025, NRG PALLAS, together with main contractor FCC and designer ICHOS, start the next phase of the project. The construction site has been reorganized for the construction of the PALLAS-reactor building and surrounding buildings. Construction and preparatory construction works and currently ongoing on:
- Underground floors of the Nuclear island (floor -3,-2,-1 of the reactor building)
- The construction pit of the secondary cooling system building and the cooling water pipes
Commissioning
Upon completion of construction, NRG PALLAS will have an advanced nuclear infrastructure. The commissioning phase that follows is an essential part of the project. During this phase, all installations and systems are carefully tested and validated to ensure they meet design and safety criteria. It is a technically complex process that is carried out step by step to bring the reactor into operation in a controlled and safe manner.
The commissioning program includes several phases, starting with the completion of construction and installation work and the execution of extensive system tests. This is followed by preparatory activities necessary to start up the reactor. In the subsequent phase, the systems are activated, first in a semi-commercial setting, and then fully operational.
An important part of this phase is the testing conducted before the fuel is loaded. This is followed by the loading of the fuel elements, low-power testing, and gradual ramp-up to full power levels. All these steps are aimed at bringing the reactor into operation safely, stably, and reliably—fully in accordance with the strict requirements applicable to nuclear facilities.
