Construction update PALLAS-reactor Q2 2026
Major construction milestone: completion of the -3 floor
In the second quarter of 2026, the PALLAS project has reached a historic milestone: the completion of the -3 floor of the reactor building. This is the first new nuclear building to be built in the Netherlands in more than 60 years. The -3 floor forms the foundation of the underground reactor structure (levels -3 to -1). The structure consisted of multiple concrete pours of 500–600 m³ per pour, with a total of almost 500 tonnes of reinforcing steel. The last pour was completed at the beginning of May after more than 13 hours of continuous concrete work. Due to the high requirements for strength and watertightness, a controlled curing process by means of cooling has been applied, including integrated cooling and a waterproof membrane. Together with the waterproof membrane, this provides a durable and robust base for the reactor.
With this phase completed, construction of the inner and outer walls of the underground levels is now underway, followed by the installation of key reactor components. Preparations also begin for the construction of the APS (airplane protection shell), the protective outer wall of the reactor building.
Progress Contract Batch 2: SCSB put (secondary cooling system building)
Significant progress has also been made within Contract Batch 2. The work on the SCSB pit is fully on schedule. After the excavation and lengthening of the piles, a 50 cm thick gravel layer was applied, followed by a pouring of approximately 900 m³ of underwater concrete in an 80 cm layer. In parallel, the water in the well has been filtered to achieve the required quality for dewatering to deeper soil layers.
In preparation for the upcoming HDD drilling (horizontal directed drilling) for the inlet pipes, the pipes have been delivered and temporarily stored on the site on the Zuiderhazerdwarsdijk. The Design Version Release D is available and the Manufacturing & Construction Data Packs are currently being finalized. As soon as the well is fully ready, drilling activities can start immediately.
