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ITER NEWSLINE 220
This is a place that will feel very much like the surface of the Sun. When deuterium-tritium operation begins, the ITER divertor will carry a heat load twenty thousand times higher than that of a hot July day in Provence.
As if that wasn't enough, the divertor structure will also have to withstand tremendous magnetic forces that will press and pull with a force on the order of one hundred tonnes.
An essential component of the ITER machine, the divertor is also one of the most challenging to build, assemble and install.
The ITER divertor acts as the Tokamak's exhaust system, running toroidally along the bottom of the vacuum vessel, extracting helium ash from the burning plasma. It is split into 54 cassettes, each containing a plasma-facing "dome", inner and outer "targets," and a number of diagnostic systems. There are 19 variances in the diagnostics arrangements and as many integration issues ...
Each nine-tonne cassette will be installed inside the vacuum vessel through remote handling operations. The highly complex and delicate installation sequences are being demonstrated and validated at the ITER Divertor Test Platform Facility in Tampere, Finland.
The Procurement Arrangement for the divertor cassette and assembly was signed on Tuesday, 19 April. It covers the manufacturing by Europe of 60 cassette bodies (54 cassettes plus 6 spares) and the integration of the components and diagnostics systems provided by other Domestic Agencies as part of different procurement packages.
"The key challenges in this Procurement Arrangement are: one, the manufacturing tolerance to meet the interfaces (on the order of a fraction of a millimetre); and two, the assembly sequence of the different divertor components," explains Mario Merola, head of the Internal Components Division. "Planning and coordination will be paramount."
Following the production of a full-scale prototype for assembly trials, series production should begin in 2015. The present schedule plans for the installation of all 54 cassettes beginning in 2021 during the second phase of ITER assembly; the divertor will only be needed when hydrogen-helium operation begins in 2022.
One line shows the energy demand of the world's population, which has just exceeded the seven billion mark; extrapolated into the future, this line shows a steep incline. The second line representing the world's supply of fossil fuels slopes downward almost as sharply. The question is: How do we fill the gap between the two trajectories? What technologies are available now or will become available in the future? Which are technologically and economically feasible? And also: How can we reduce greenhouse gas emission by 80 percent within the next 40 years, as indicated in Europe's ambitious Energy Roadmap 2050?
"If we make the right choices, the transformation is feasible," Günther Oettinger, Europe's Commissioner for Energy, said last week as he opened the European Energy Conference in Maastricht, the Netherlands.
It was not by coincidence that the conference chairmen, Harald Bolt and Fritz Wagner, had chosen the birthplace of the European Union as the location for this showcase for both available and yet-to-be-developed energy technologies and energy policies.
"In order to meet the ambitious goal of reducing CO2 emissions by 50 percent by 2050 and to meet the ever increasing energy demand, more than 40 times the current annual investment will be needed for the development of new energy technologies at a global scale," Herve Pero, Director General for Research within the European Commission, pointed out. "This looks almost impossible against the backdrop of the economic crisis," he continued, announcing the revision of Europe's current Strategic Energy Technology Plan (SET). "We need to go beyond technologies. We need a long term vision ..."
This message was also stressed by Javier Solana, former Secretary General of NATO and Secretary General of the Council of the European Union in his keynote lecture: "The measures we have are our minds ... to make this world a better world."
Besides updates on the status of wind and solar energy projects, carbon capture and sequestration technologies, and material research, fusion made its way onto the European energy stage. ITER Director-General Osamu Motojima presented the status of the ITER project followed by Francesco Romanelli, leader of the European Fusion Development Agreement (EFDA) and its figurehead, the Joint European Torus (JET), who gave an overview of the European strategy to take fusion to an industrial scale.
Recent analysis of the economic aspects of commercial fusion performed by EFDA has shown that fusion does have the chance to play an important role in the future energy roadmap. "But only if politics come in and CO2 emissions become a serious economic aspect," Helena Cabal from the Spanish fusion institute CIEMAT said. "Climate change will be a key driver for fusion to enter the market."
On Tuesday 24 April, for the third time in ten months, the French Nuclear Safety Authority (ASN) dispatched a group of inspectors to ITER. Regular inspections of ITER's nuclear installation are implemented within the framework of the ITER Headquarters Agreement, which was signed on 7 November 2007 by the ITER Organization and France.
As stipulated in the Agreement, ASN can carry out between five and ten inspections per year. "We are notified of their visit in advance, but not of the issues they will be investigating," says the head of the ITER Licensing Cell Joëlle Elbez-Uzan.
During their first visit on 20 July 2011, the ASN inspectors looked at the general organization of ITER, focusing on the implementation of quality control procedures all through the chain of contractors. Their conclusion was that the ITER Organization system is "robust."
The second ASN visit on 26 January 2012 was devoted to analyzing the procedures by which the ITER Organization deals with the inevitable "deviations" in the construction works such as small cracks in concrete or slight discrepancies in the plane of the surfaces. ASN considered on this occasion that the notification process—from the moment a deviation is identified by the contractor until a non-conformance report is processed by ITER Organization—was not satisfactory and had to be improved.
Last Tuesday, ASN experts decided to see for themselves and descended into the Pit in order to check, one by one, the cracks (most of them a fraction of a millimetre deep), scratches, chipped edges in concrete fillings, and other slight departures from perfection.
As with every inspection, an official letter will soon be sent to the ITER Organization detailing the actions requested by ASN. "Our responsibility as a nuclear operator is to ensure the supervision of the supplier chain and the way in which safety requirements are implemented," says Joëlle. "Filling a crack, however small, is important.
And working on an improved concrete 'formula' is one the solutions to be investigated in order to minimize the size of cracks at a further stage of construction."
A shallow crack on the surface of a retaining wall or slight discrepancies in surface plane might be considered by some as very minor defects. In nuclear safety, however, nothing is minor.
The ITER magnet system that confines, shapes and controls the hot plasma inside the vacuum vessel consists of an arrangement of several large coils wound with jacketed superconducting cable, referred to as conductor.
In order to qualify for operation, the ITER conductors must undergo extensive testing.
Beginning in 2007, the ITER Domestic Agencies involved in conductor procurement (China, the Republic of Korea, Europe, Japan, Russian Federation, USA) submitted samples to a dedicated European testing facility: the SULTAN installation, located at the Paul Scherrer Institute (PSI) in Villigen, Switzerland, operated by the Centre de Recherches en Physique des Plasmas of the École Polytechnique Fédérale de Lausanne (EPFL).
The SULTAN (SUpraLeiter Test ANlage) facility was originally built in the 1980s to test high field conductors for the NEXT European Tokamak project. It was modified as a conductor test facility before the start of the ITER Engineering Design Activities (EDA) in 1993 and since then has been used to test many conductors, including those for the ITER model coils in the late 1990s.
SULTAN is the only facility worldwide capable of testing the niobium-tin (Nb3Sn) and niobium-titanium (NbTi) conductors that will be used in ITER. In SULTAN, conductor samples are exposed to magnetic fields, current intensity and temperature conditions that are equivalent to those of the ITER operational environment.
Until now, contracts for conductor testing in SULTAN were directly concluded by the ITER Domestic Agencies.
In order to ensure continuity the ITER Organization, acting on behalf of the ITER Domestic Agencies involved in conductor procurement and the École Polytechnique Fédérale de Lausanne, has signed a three-year service contract that guarantees the availability of the facility.
Through this contract, which will enter into force on 1 May 2012, the ITER Organization becomes the primary user of the SULTAN facility.
With the 493rd and final antiseismic pad installed and the retaining walls finalized, a relative quiet has settled over the ITER Tokamak Pit.
As action will soon move toward the adjoining Assembly Building area, two of the four cranes that operated over the Pit were dismantled this week.
Crane C4, located on the northwest corner of the work site, was taken down on Monday 23 April. Two days later, a similar operation was performed on crane C3 in the south corner.
Dismantling a 50-metre-high tower crane is a delicate and spectacular operation. First, it's necessary to remove the concrete counterweights that balance the 65-metre-long boom. Once the 15 tonnes of counterweights have been lowered, crane dismantling specialists climb into the boom to begin the detachment process.
With the boom hanging solidly from a mobile crane, specialists can begin unscrewing the large bolts that connect the 14.7-tonne boom to the tower. Once freed, the lifting crane slowly moves it down to the ground where it will await further dismantling.
"The only real difficulty," explains dismantling specialist Armand Depit of MAGSUD, based in Aix-en-Provence, "is the wind. Also ... finding enough room to lay the boom on the ground ..."
On Wednesday, as crane C3 was dismantled, the air was perfectly still on the ITER platform and there was still plenty of room—although not for long—in the Tokamak Pit work site perimeter.
The dismantling operation went smoothly and took less than one hour and a half.