A crucial milestone has been reached in the construction of the Pallas research reactor in Petten, Netherlands: the installation of 380 foundation piles, each 33 meters in length, within the construction pit.
This signifies a major step forward in the project to replace the existing High Flux Reactor (HFR).
Regulatory Approval and Preparatory Work
In June 2022, the Foundation Preparation Pallas-reactor submitted an application to the Authority for Nuclear Safety and Radiation Protection (ANVS) for permission to construct and operate the Pallas reactor.
ANVS granted the construction license in mid-February of the previous year, and preparatory work on the foundation commenced in May 2023. Belgian construction firm BESIX, awarded the contract in November 2022, is responsible for executing this phase of the project.
Construction Pit: A Complex Undertaking
The creation of the construction pit involved excavating a hole approximately 50 meters by 50 meters and 21 meters deep, executed in multiple stages. This involved digging 30 narrow trenches, then filling them with concrete to form “diaphragm walls.” These walls are reinforced with 380 bored piles and connected by a ring beam at the top.
Within the construction pit, further stabilization and reinforcement measures are underway. Diaphragm walls are being strengthened with drilled steel pipes and anchor cords, ensuring stability.
The pit has been temporarily filled with water to counteract groundwater pressure, and a gravel layer will be added at the bottom to prepare for the concrete foundation pour.
Next Steps and Collaboration
The upcoming phase involves pumping out 48,000 cubic meters of water from the construction pit, preparing the site for the next stage: the actual construction of the reactor. The Foundation Preparation Pallas-reactor attributes the smooth progress so far to successful collaboration among NRG-Pallas, ICHOS (the main designer), and BESIX (the contractor).
While funding for the Pallas reactor’s construction has been allocated, the Dutch government has yet to finalize its decision. Construction can proceed if the Dutch parliament approves the establishment of a new state-owned company and the European Commission greenlights the public investment.
Continued Preparations and Contractor Selection
In January 2023, Pallas initiated a tender process for the construction of the reactor and surrounding buildings. Following EU public procurement rules, Spanish construction firm FCC Construcción was awarded the contract in December.
The Pallas research reactor will replace the existing High Flux Reactor (HFR) in Petten. The 45 MW HFR has been in operation since 1960, primarily used for fundamental research and medical radioisotope production. The new Pallas reactor, with a thermal power of around 55 MW, is designed to be more efficient and effective in deploying its neutron flux.