After the top sections of the 380 foundation piles were cut off, the piles were opened and inspected. Steel reinforcement bars (rebars) have been installed in the piles to strengthen their connection with the bearing slab (foundation floor of the reactor building), which is the final step yet to be completed in the reactor building's foundation.
With the fully pumped out construction pit, the works at the bottom of the pit have been underway. The top parts of 380 foundation piles remain sticking out from the concrete floor. These top parts are being cut off and in the next step, they will be opened and inspected. Placing rebars and filling piles with concrete follow.
With the foundation piles drilled and the concrete floor fully hardened, the basic foundation of the construction pit was established, which meant the water could be pumped out. A total volume of 48,000 cubic metres – equivalent to the volume of 19 Olympic swimming pools – were eventually pumped out.
For many months, the construction pit of the PALLAS-reactor resembled a swimming pool. Water in the pit balanced ground water pressure and prevented the uplift of the bottom. With all 380 foundation piles in place and the bottom concrete floor hardened, the water started to be pumped out of the pit. The water (of which quality was tested in the lab) is being disposed to surrounding landscape according to the approval given by the authorities. Groundwater level is monitored throughout the process to ensure the water does not exceed accepted levels.
During a continuous 30-hour work, 4,000 cubic meters of concrete were poured under water at the bottom of the PALLAS-reactor construction pit to create a 1.5-meter-thick concrete layer. Prior to this, a layer of gravel had been applied in to the excavated pit to ensure a high-quality underground pour.
On 8 June, the PALLAS construction site was opened for a visit of external and internal stakeholders as part of the initiative called ‘Dag van de bouw’ (construction day). Around 450 visitors had a chance to experience the preparatory works of the PALLAS-reactor up close.
More than half of 380 foundation piles have been drilled in the ground of the reactor building.
The drilling of the 380 foundation piles of the reactor building has been underway. Given that the piles are drilled under water and the quality of all work is not visible until the pit is fully pumped out, several diving inspections are conducted. A diver inspects the quality of the drilling process at the bottom of the pit.
The drilling of 380 foundation piles of the reactor building to a depth of -47.0 NAP has started. To balance ground water pressure, there is still water in the pit. Therefore, the 33-meter-long piles are drilled from the pontoon, using the pile cleaning device (PCD) to accurately position the drilling pile on the bottom.
After more than three months of digging (first by dry excavation, in the second phase by wet excavation), the pit excavation was completed. The pit is excavated and extracted sand, clay and peat have been disposed of at the sand depot. The pit is still filled with water up to the groundwater level.
Foundation piles have been successfully tested in 5 rounds of quality tests. The tests are conducted to verify pre-determined parameters of drilling such as speed, torque, and flow speed of the grout.
On 5 December 2023, PALLAS partners with FCC Construcción for the construction of the PALLAS-reactor.
The pit is being dug from the ground level down to -6.0 NAP by dry excavation. Thereafter, it is wet excavated from pontoon down to -9.0 NAP, followed by pumping out the sand with water to -17.5 NAP and reaching down to a depth of 21 metres.
Works on the anchors continue.
The anchors, consisting of 162 bored steel tubes with 15 anchor strings, are drilled through the upper part of the diaphragm walls, and serve as a reinforcement to the diaphragm walls.
Placement of capping beam
Ongoing work on the pit. A ring beam will be installed after finishing the diaphragm walls.
Trenches 1.5 meters wide have been dug into which concrete was poured to create the diaphragm walls - the first stage in the realization of the pit. Concrete is checked upon arrival at the construction site.
First concrete pour at the construction pit of the PALLAS-reactor on 4 May 2023.
Work area preparation
Works on the access road and official opening of the access road to the PALLAS site on 22 December 2022.
