From approximately 200 people on site currently, worker numbers will rise to 1,000 at the end of the year, before climbing to 2,000, then 3,000 at the peak of construction activities.
On the site of the future Diagnostics Building, rebar structures take their place. If all goes according to schedule, concrete pouring will begin on this side of the Tokamak Pit in August.
It's art that is appearing on the floor of the Tokamak Pit! Carefully placed, concentric circles of rebar at the exact spot where the Tokamak will be installed and assembled.
The 493 seismic pads are now hidden from view and the Seismic Pit is no longer 17 metres deep ... With the completion of the ground support structure and the newest propping, it's more like 13 metres deep.
In mid-June, only a small section of the Tokamak Pit still requires propping and formwork. Work is underway to position 4,000 tons of steel rebar—in radial/circular patterns in some areas, linear in others.
This gap between the Tokamak Complex and the Assembly Building will permit the installation of critical networks such as electricity, piping and cooling. Photo: F4E
Rebar in installed in pre-decided patterns on the floor of the Tokamak Pit. Approximately two metres will subsist between the Tokamak Complex basemat and the surrounding walls, so that the entire Complex can move on its seismic pads in case of ground motion.
The propping and formwork extends to the very walls of the Seismic Pit. And yet, all of these materials will have to be removed once the basemat is in place so that the seismic pads will remain accessible for inspection. How will it be done? A notch in the far wall will be the "exit door" through which the material will be removed.
In just three months, the seismic columns have nearly disappeared from view. Work will begin late in May on reinforcement work in the area of the Tokamak.
Propping and formwork are nearly done; reinforcement begins
Level with the top of the seismic pads, the crisscrossing of reinforcement bars gets underway in May. Four to five months will be necessary to lay 4,000 tons of rebar.
Reinforcement work begins in the Tokamak Pit, approximately 13 metres below platform level. The second basemat, like the first, will be 1.5 metres thick. Photo: F4E
The Seismic Pit was 17 metres deep after its excavation. But after the first 1.5-metre-thick basemat was set into place, followed by two metres of seismic columns and pads ... workers are now standing approximately 13 metres below the platform. Photo: F4E
This propping, like so many broad shoulders, will support the weight of the concrete basemat that will begin to take shape in August. Once the basemat is in place, these materials will be removed. Photo: F4E
The ITER Tokamak, surrounded by its cryostat and bioshield, will sit in the centre of the Tokamak Pit. Twenty-three thousand tons, that's three times the weight of the Eiffel Tower. Photo: F4E
On 25 April, the French nuclear regulatory inspectors (ASN), accompanied by one expert from the French Radioprotection and Nuclear Safety Institute (IRSN), scrutinized the ongoing works in the Seismic Pit.
Built upon the same foundation, the Diagnostics and Tritium buildings will stand to one side and another of the Tokamak Building. Under the future Diagnostics Building, it's easy to see the linear pattern of the anti-seismic pads and columns, compared to the Tokamak "star pattern" at left.
Adjacent to the Tokamak Pit, a 150 m2 mockup has been set up to demonstrate the complex pattern of the steel reinforcement bars planned for the B2 foundation slab. Four different areas of rebar presenting specific challenges (density, complexity) will be reproduced at 1:1 scale in the mockup.
The B2 slab will progress in stages: propping and formwork will take place February through June, followed by reinforcement work (April through August) and concrete pouring (June through December).
First silver, then yellow, then brown: on top of these aluminium props, workers will install yellow formwork, which in turn will be covered by wooden structures.
In the Hot Cell area, material is stored for the B2 prep work. Propping and formwork activities are underway and will continue through June 2013. Photo: F4E
Wooden formwork will be installed on top of these yellow panels. The seismic pads will be protected throughout the duration of foundation work. Photo: F4E
Four sides ... 493 columns. In order to pour a single foundation slab for the Tokamak Complex, a lot of precise formwork must be done in advance. Photo: F4E
The metal fingers (studs) on the top of the seismic pads will be crisscrossed with metal rebar and become part of the B2 slab. Space will remain between the two slabs for regular inspections. Photo: F4E
Material is being moved into the Seismic Pit for propping and formwork activities: at precisely 2 metres above the first slab, the floor of the Tokamak Complex will be in place by year's end. Photo: F4E
In preparation for the buzz of activity planned in the Seismic Pit during the construction of the B2 slab, wooden props are going up in the penetrations of the retaining wall. These both protect workers below and protect the openings. Photo: F4E
In one corner of the Seismic Pit, a tower crane is going up to prepare for the next phase of work: the pouring of the B2 slab that will act as a floor to the three buildings of the Tokamak Complex.
The basemat for the Tokamak Complex—the 1.5 metre-thick B2 slab—will sit directly on top of the Seismic Pit's 493 columns and pads. On 27 February 2013, the Central Integration & Engineering Directorate completed the challenging mission of closing B2 slab design and obtaining model approval in a meeting held with the European Domestic Agency and the Architect Engineer ENGAGE. Work began immediately on B2 propping and formwork activities in the Seismic Pit.
The construction consortium chosen in December to build the 360,000-ton Tokamak Complex is establishing offices on site and working on the detailed design of the structure. As the formwork is removed from the drying basemat in November, work will begin on the civil works. Photo: F4E
Between the bottom slab (which the seismic pads rest on) and the upper slab there will be a gap of two metres. All of the formwork supporting the second slab will have to be removed through this gap. Photo: F4E
These are the last pictures of the complete seismic protection system that will soon be hidden from view: formwork and propping will begin end February. Photo: F4E
The Seismic Pit is wearing its cloak of winter blue for this late-day photo taken mid-January. Building begins here in 2013 on the Tokamak, Diagnostic and Tritium buildings.
Snow never lasts for long in Provence - five days after this winter's first episode, nothing remains. ¶In the foreground, deep precipitation networks are put into place more than 10 metres below the surface of the platform.
The Assembly Building is a close neighbour to the Tokamak Building. Large, overhead cranes mounted on rails will run the entire length of the two buildings during assembly, along a continuous, 175 metre-long crane bay.
The waterproof Seismic Isolation Pit is designed to keep water OUT of the foundations of the Tokamak Complex ... but as long as it's open to the sky, water also stays IN.
Ten centimetres of water in the Seismic Pit attest to the heavy rainstorms that passed over Provence in early November. Photo: ITER Organization, November 2012
Heavy works are underway for the future antechamber to the Tokamak Building: the Assembly Building, which will house two 750-ton cranes and pre-assembly activities.
On 6 October 2012, ITER hosts 1,300 visitors for its second annual Open Doors Day. Guests are treated to a historic walk through the foundations of the Tokamak Complex, soon to be covered over by the next-level basemat.
The Seismic Pit stands ready for the next phase of work, which should begin in 2013: the formwork, reinforcement and concrete pouring for the next-level basemat that will hide the anti-seismic bearings from view.
This 90x130 Seismic Pit will support the weight of the Tokamak Complex. Made up of the Tokamak, Tritium and Diagnostic buildings, the total weight of the Tokamak Complex is estimated at 360,000 tons.
In the foreground, space has been cleared and foundations set for the ITER Hot Cell building. On the other side of the Tokamak Pit: the worksite for the future Assembly Building. Photo: F4E
In 2013, the seismic protection system that is now visible will be entirely covered by the floor of the Tokamak Complex. The view is impressive, but don't get too close to the edge!
For a TV program on ITER (local French channel TLP), an interview is conducted on the precise spot where—five years earlier—a flag flew to mark the location of the future ITER Tokamak.
In the completed Seismic Isolation Pit, the largest opening in the retaining walls looks onto the site of the future Hot Cell Facility. Smaller openings in the walls have been created to permit underground pipes and cables to reach the Tokamak Complex buildings.
After 18 months of presence, the workers have temporarily quitted the Seismic Pit for other areas of the platform: site trench work and excavation for the Assembly Hall.
Excavation work has begun in a large square area next to the Tokamak Pit, where an Assembly Hall will be constructed to house pre-assembly activities for Tokamak components.
The French Nuclear Safety Authority (ASN) inspects the ITER retaining walls in April 2012, verifying each crack (most of them a fraction of a millimetre deep), scratch, chipped concrete edge, and other slight departures from perfection.
Here it is: the completed ground support structure
The first-phase works in the Tokamak Pit are over. The next stage: the civil works on the Tokamak Complex, beginning with the creation of a reinforced basemat on top of the seismic pads. Photo: Engage-AP
Between the rough face of the rock and the 15-metre-tall retaining walls, a space persists. At a later stage in the contruction works the space will be filled with sand and gravel and compacted. Photo: Engage-AP
Support in the shape of a star for the ITER experimental device: the very device that aims to bring the energy of the stars down to Earth. Photo: Engage-AP
The ground support structure for the Tokamak Complex—basemat and walls—is now complete. The retaining walls maintain and stabilize the surrounding rock and "waterproof" the Seismic Pit.
Construction on the retaining walls of the Tokamak Complex Seismic Pit ends in April. A branch is hung from one of the tallest points to symbolize the end of works—a construction tradition originating in Eastern Europe called "topping out."
The concrete pillars (1.7 metres tall) and their seismic pads form an army of standing columns upon which the Tokamak Complex will be built. The area between the two concrete basemats will remain accessible for regular inspection of the seismic pads.
Formwork used to shape the retaining walls is supported during drying time. The space between the walls and the rock face will be filled with a mix of gravel and sand and compacted.
The excavation of the Tokamak Complex Seismic Pit, which required the displacement of 210,000 cubic metres of earth and rock, was completed in February 2011. One year later, progress made on construction is spectacular. Photo: F4E
As of early February 2012, 481 out of 493 concrete plinths had been cast (the formwork used for these 90 x 90 cm pillars can be seen in white and black in the photo). Three hundred and four plinths have now been topped with seismic bearings.
Among the "standing soldiers" at the bottom of the Tokamak Pit, it's easy to distinguish the future location of the machine by the spokes that branch out from a central plinth.
Three-and-a-half months were necessary to complete the 1.5 metre-thick Seismic Pit basemat. The works underwent regular inspection: both internal audits and those conducted by the French nuclear safety regulators (ASN) have confirmed the good quality of the works.
The 140 "oriented plinths" in the centre of the basemat are the last to be poured: these plinths will directly support the 23,000-ton ITER Tokamak. Photo: F4E
The surface elevation, roughness (guaranteeing that the second-phase concrete will adhere perfectly) and height of the reinforcement at the top of the plinth are verified before each bearing is installed. Tolerance for these measurements is in the range of one millimetre. Photo: F4E
Concrete pouring for the Seismic Pit basemat progresses at a rhythm of one slab per week. The twenty-one slabs, once completed, will form a single, smooth surface.
Late November 2011, the concrete slab at the bottom of the Tokamak Pit is 80 percent complete: 14,000 out of 17,000 cubic metres of concrete have been poured since August.
One and a half metres thick at their base, the retaining walls will form a box around the foundation slab of the Tokamak Pit and the anti-seismic pillars and bearings. Photo: F4E
Nearly 6,000 cubic metres of concrete will be necessary for the retaining walls of the Seismic Pit. Work began mid-October and will continue through February 2012.
Cohesion between the plinth, second-phase concrete and mortar is essential to achieve the monolithic behaviour of the structure. Image credit: ITER Organization
The bearing is placed on top of a height adjustment system that enables the position, level and inclination of the bearing to be fine tuned. Topographical checks are performed before plinth and bearing are ready to receive the second-phase concrete. Photo: F4E
The first five-metre vertical segment of retaining wall has been poured in this corner of the Seismic Pit. At this level, the retaining walls are 1.5 metres thick. Photo: F4E
Workers guide just the right dose of concrete onto the top of each seismic pillar; this "second-phase" concrete will join the pillar to the seismic bearing. All over the Seismic Pit, this operation is being repeated 493 times. Photo: F4E
Looking south over the football-pitch-sized Seismic Pit. To the right: the cleared area for the Hot Cell Facility. To the left: the long red line of the Poloidal Field Coils Winding Facility.
The seismic basemat—the white "floor" of the Tokamak Pit—is filled in progressively. Along the western wall, work has begun on the retaining walls (lower left).
493 seismic pads will protect the ITER machine and the Tokamak Complex (Tokamak, Diagnostic and Tritium Buildings). This CAD-generated image shows the exact configuration of the pads on the 1.5-metre-thick Seismic basemat. Image credit: ITER Organization
The lower five metres of retaining wall will be the thickest. From one and a half metres at its base, the wall will taper to 0.5 metres at its highest point.
The 15-metre-tall retaining walls will be poured in three 5-metre stages; the lowest five-metre segment, seen framed out here, is 1.5 metres in width. Space between the upper segments of the concrete retaining wall and the rock face will be filled in with gravel and sand and compacted. Photo: F4E
The "crawl space" between the Seismic Pit basemat and the Tokamak Complex basemat will permit regular inspection of the seismic pads, which are designed to last well beyond the lifetime of ITER. Photo: F4E
In order to cure the "second-phase" concrete below each seismic bearing, workers use a local heating unit to maintain the concrete temperature around 30 degrees centigrade. Photo: F4E
Atop the concrete plinth, the seismic pad has been positioned and cemented into place. When completely dry, the newer concrete will take on the exact colour of the older concrete.
On the ITER site, seismic isolation pads await installation. In the months to come, the pads will be installed at a rhythm of approximately ten per week.
Sandwiched between the Seismic basemat and the Tokamak Complex basemat
Each 90 x 90 cm pillar (1.7 metres tall) will support a seismic isolation pad made of alternate layers of metal and rubber. The floor of the Tokamak Complex will rest on a total of 493 pillars.
This portion of the Seismic Pit basemat has dried, and second phase work begins: the pouring of the 493 concrete plinths that will support the anti-seismic bearings of the Tokamak Complex.
Pouring activities begin in the north-west corner of the Seismic Pit; in the opposite corner, preparations are underway for the second day's pour planned for the following week. Work will continue—first one side, then the other—in a counter-clockwise direction until the edges of the basemat are filled in. Photo: F4E
The two concrete batching plants on site are each capable of providing a flow of 100 m³ per hour. One plant serves as a backup to the other, ensuring that no disruption occurs in supply during the 12-hour pouring days. Photo: F4E
Some 800 m³ of concrete are poured on the first day. This 12-hour operation will have to be repeated 21 times over the next 3 months to complete the basemat of the Seismic Pit. Photo: F4E
The three buildings of the Tokamak Complex will share a single foundation: having a monolithic structure avoids the relative displacement of process pipes crossing the buildings. Photo: F4E
Sitting atop the Seismic Pit basemat, 493 of these 1.7 metre concrete columns, or "plinths," will support the seismic pads. These, in turn, will support the basemat of the Tokamak Complex—the actual "floor" of the installation. Photo: F4E
Workers install metal "chairs" for structural stability between the lower and higher levels of crisscrossed reinforcement. Foundation pouring will begin in August. Photo: F4E
The vertical reinforcement bars standing five metres high against the rock face will be part of the lower retaining wall of the Seismic Pit. Photo: F4E
Workers measure the exact spacing of the rebar used on the floor of the Seismic Pit. Regular spacing and tying off the bars so that they remain in position are important to achieving the desired strength of the completed concrete. Photo: F4E
Metal "chairs" are positioned on the bottom layer of crisscrossed rebar. Steel reinforcement will be built up to 1.5 metres before foundation pouring begins. Photo: F4E
One of four pedestrian access staircases into the Tokamak Complex Seismic Pit. Some seventy workers involved with foundation work go up and down these staircases daily. Photo: ITER Organization
On top of a five to ten centimetre layer of "blinding concrete," workers position steel rebar in June 2011. Some 3,400 tons of rebar is planned for the first level of foundations: the Tokamak Complex Seismic Pit basemat. Photo: F4E
Work progresses in the neighbouring Hot Cell Facility area
Finishing touches to the Hot Cell Facility area before work begins on the blinding layer of concrete, reinforcement and foundation work, just like in the Tokamak Complex area seen beyond. Photo: F4E
The first level of steel rebar is positioned on the floor of the Seismic Ísolation Pit. Reinforcement for the Seismic Pit basemat will be 1.5 metres high. Photo: AIF
A thin layer of concrete is spread to create a clean and flat surface upon which to begin foundation operations. In the Seismic Pit, 550 m³ of concrete were necessary. Photo: ITER Organization
The final bottom and façade profile is completed in May, and work begins on the blinding layer of concrete. Photo: AIF
May 2011
All photos are to be credited to the ITER Organization unless otherwise specified. The ITER Organization provides images and videos on its public website free of charge for educational and institutional use. An explanation of the "Terms of Use" is available for download.
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