you're currently reading the news digest published from 14 Jan 2019 to 21 Jan 2019



Cryolines | Not just any pipes

In order to produce and sustain plasmas ten times hotter than the core of the Sun, some essential elements of the ITER machine need to be cooled to temperatures only encountered in the void of outer space. Superconducting magnets and cryopumps will operate at a few degrees above absolute zero—~ 4 K, or minus 269 °C—and the thermal shield will be only slightly warmer (80 K, or minus 193 °C). These temperatures are obtained by circulating a steady flux of cryogenic fluid through a complex network of high-technology piping—the ITER cryolines. Cryolines begin their long journey in the ITER cryoplant—where the cooling fluids are produced—and continue along an elevated bridge to the Tokamak Building, about 100 metres away. A section of cryoline can host up to six or seven 'process pipes,' each devoted to a specific fluid, flow direction or function. Cryolines rarely run straight; instead they bend and turn to adapt to the topography of the worksite, or to snake their way through the congested spaces of the cryoplant and Tokamak Building. ITER will have approximately 5 kilometres of cryolines ranging from 25 to 1000 millimetres in diameter. Part of India's contribution to ITER, the procurement is split between two companies, France's Air Liquide and India's INOXCVA. Not just any material can be chosen to transport extremely low-temperature fluids. 'Extreme cold makes most material brittle,' says Nitin Shah, the technical responsible officer for the ITER cryolines. 'As a consequence we need to use special-grade austenitic stainless steel, low in carbon and high in nickel and chromium.' Contraction is another challenge. When exposed to cold, materials retract—and when cold is extreme, contraction is significant. In the ITER cryolines, a 10-metre pipe will shrink in length by 3 centimetres when the cooling fluids begin to flow inside. The solution for compensating such contraction comes in the form of steel bellows and flexible hoses, made out of an extensible material and placed at regular intervals along both the inner pipes and the outer jackets. Like frozen food brought home from the supermarket, the cooling fluids flowing in the cryolines must be carefully insulated in order not to warm up during their journey from the cryoplant to the Tokamak Building and back. As the temperature gradient between the fluids and the outside environment is particularly high (on the order of 300 °C) the insulation of the cryolines is particularly sophisticated. 'There are three ways by which heat is transmitted from one environment to another: radiation, convection and conduction,' explains Shah. To minimize transmission by radiation, the inner pipes of the cryolines are wrapped with between 30 and 60 layers of glass-fibre/aluminized Mylar insulation. Convection is dealt with by creating a high vacuum within the outer jacket. And as for conduction, it occurs through solid contact. 'As the inner pipes are attached to the inner wall of the cryoline jacket, transmission by conduction is not completely unavoidable,' says Shah. 'But we can reduce it considerably by using as few support pieces ('spacers') as possible, by optimizing their geometry and, of course, by choosing the least conductive material.' As if all these challenging requirements were not enough, the ITER cryolines must also be particularly robust to resist the forces that could be exerted in case of a quench, which is the sudden loss of magnet superconductivity. During a quench the cooling fluids need to be transferred almost instantaneously from the machine to the quench tanks. At Indian Domestic Agency contractors Air Liquide (France) and INOXCVA (India), fabrication is approximately 50 percent complete. Newsline recently visited the Indian facility located in the outskirts of Vadodara, an industrial city with a population of more than two million in the western state of Gujarat (see gallery below). INOXCVA is a company with a quarter-century of experience in cryogenics, and whose Cryo Scientific Division is deeply involved in space applications, the nuclear industry, and all other major technologies involving cryogenics. The manufacturing of spools—the 2- to 10-metre sections of cryoline that, once assembled at the ITER site, will form the cryoline network—began in 2017 in a specially constructed workshop complete with a clean room devoted to the most delicate and sensitive operations. For the team at INOX, the challenge in filling the ITER order lay in the stringency of the technical specifications as well as in the quantity of spools to be produced—approximately 700 of them, each with a different shape. 'The ITER cryolines are all angles, bends and turns. Less than 20 percent of the spools we need to produce are straight,' says Sanjay Gajera, the quality responsible officer at the INOXCVA facility in Vadodara. In the large open space of the workshop, dozens of spools are in various stages of fabrication and, indeed, very few are straight. The factory receives the raw pipes from India and Europe (mainly the Ukraine); once cut to the required dimensions and cleaned, the welding process, which is exclusively manual, can begin. 'Because of the complex shapes involved it is impossible to use automatic (orbital) welding machines,' says Sanjay. The inner pipes pass through the clean room to be wrapped in insulating tape multilayer insulation before being inserted into their outer jacket. At each stage of fabrication, the pipes are visually inspected and their internal surface and welds are explored by way of 'boroscopy' (using a visualizing tool similar to an endoscope), X-rayed and cold tested. At the end of this process, the spools are sealed at both ends under a slightly pressurized atmosphere of nitrogen to protect them from corrosion and impurities during storage and transport, and until they are assembled and welded on site at ITER by INOXCVA personnel. The first batches of INOXCVA cryoline spools reached ITER in July 2017 after a one-month sea voyage from India. Installation in the cryoplant is underway; in the Tokamak Building work will begin this summer. The bridge between the two buildings will be in place in 2023, and the cooling fluids should begin circulating in the crydistribution network in 2024 in anticipation of First Plasma scheduled the following year. Click here to view a video of the fabrication process at INOXCVA.

Symposium in Japan | Fusion attracts strong political support

A recent symposium in Japan on fusion energy attracted 500 participants. The Fusion Energy Forum of Japan was established in 2002 for the purpose of promoting and supporting R&D activities for the realization of fusion energy. Its diverse membership includes representatives of universities, research institutes, industry, governmental organizations, and the general public. Every year the Forum holds a symposium on progress in activities related to ITER and to the Broader Approach* that are sited in Japan. The 2018 symposium, held in Tokyo on 14 December 2018, attracted approximately 500 participants. Strong political support for fusion energy was expressed in the opening speeches of the symposium by members of the Diet—Keiko Nagaoka, State Minister of Education, Culture, Sports, Science and Technology (MEXT); Eisuke Mori, Chairman of the Parliamentary Association for the Promotion of Fusion Energy—and also by the Vice Governors of the Aomori and Ibaraki prefectures, and the Vice Chair and Director of the Japan Business Federation. In keynote lectures, ITER Director-General Bernard Bigot and ITER Deputy Director-General Eisuke Tada brought participants up to date on construction and manufacturing progress for ITER, in a live broadcast from the ITER site at 6 a.m. In the sessions that followed—on Japan's national policy for fusion research (including the roadmap toward a DEMO reactor), the involvement of industry, and Broader Approach activities (including the assembly of JT-60SA and IFMIF prototype accelerator)—the message was the same: 'All Japan' is working hard to make fusion energy a reality! *EU-Japan collaboration on fusion R&D to complement the ITER Project and to promote DEMO design activities based on the "Agreement between the Government of Japan and the European Atomic Energy Community for the Joint Implementation of the Broader Approach Activities in the Field of Fusion Energy Research," which consists of three projects: the Engineering Validation and Engineering Design Activities for the International Fusion Materials Irradiation Facility (IFMIF/EVEDA), the International Fusion Energy Research Centre (IFERC), and the Satellite Tokamak Programme (JT-60SA). Learn more about the Broader Approach here.

Fiction | "Steampunk" fusion machine travels in time

Ever since a 'Mr Fusion' device appeared on Doc's time-travelling DeLorean in the first opus of the Back to the Future trilogy (1985), fusion energy has exerted a fascination on the film industry. Countless productions, from The Saint (1997) to the 2014 blockbuster Interstellar have featured fusion machines that are either central or accessory to the plot. Travelers, a Netflix series that premiered in December 2016, offers the latest example in this trend—except that an actual, real-life fusion machine plays the part of an antimatter device used to deflect an incoming asteroid. Neither a tokamak nor a stellarator nor even a zeta-pinch, the machine developed by General Fusion, a private fusion venture on the outskirts of Vancouver, Canada, is based on an unconventional approach. It uses steam-driven pistons to compress the plasma and heat it to fusion conditions. As a result, the device has a most unusual appearance that is sometimes described as steampunk—19th century technology and aesthetics set in a futuristic context. Coming across images of General Fusion's machine on the company's website, the series' producers, also based in Vancouver, were immediately inspired: the strange-looking device, with its array of steel pistons jutting from a central sphere wrapped in aluminium foil, could pass perfectly for a fictional antimatter apparatus. Having completed their experimental campaign on the 'steampunk' device, the General Fusion team made their workshop available to the Travelers production. A few props were added and—for a couple of days—a team of special agents from the post-apocalyptic future engaged in shootouts, personality transfers and other transforming acts that make up the gist of the series. As for the future, the General Fusion team is presently working on the design of a demonstration plant—'our equivalent of JET'—whose objective is to "show that the technology works and is ready to scale to a power producing pilot plant' ... a giant step from the steampunk device featured in the series.

Construction | Honouring the crown mockup

Medieval stone masons used to engrave their personal mark on the walls and pillars of the cathedrals they contributed to building. Their present-day counterparts, the builders of ITER, did something equivalent last week: with felt-tipped markers in place of chisels, all the men and women involved in the realization of the Tokamak's supporting 'crown' scrawled their signature on the smooth concrete of the mockup that had made the crown possible. Brief but highly symbolic, the event gathered a few dozen personnel from the BIPS Project Team (Building, Infrastructure and Power Supplies), architect-engineer ENGAGE, the ITER Organization, the European Domestic Agency Fusion for Energy and its contractors¹. Like the crown it prefigured, the mockup was a collective masterwork. The construction of the mockup during the summer of 2017 was made necessary by the complex and strategic nature of the Tokamak's supporting crown. Representing a true-size 40-degree section of the projected structure, the mockup—with a footprint of 50 m² and a height of 3 metres—was to be the ultimate demonstration of the crown's constructability. In his address to the small audience, Director-General Bigot stressed its importance in the successful realization of the crown—a challenging structure characterized by unique geometry, high-density steel reinforcement and high-performance concrete. The crown was successfully finalized last autumn, and the mockup's mission has been fulfilled. Because space on the ITER platform is always scarce it may one day be demolished. In the meantime, it deserved to be honoured for its significant contribution to the project. ¹Tiresia, Energhia, Nuvia, and APAVE (heath and safety).

Neutral beam diagnostics | Right in the line of the beam

A high-precision diagnostic is about to enter into service at the ITER Neutral Beam Test Facility, where scientists are testing key aspects of ITER's external heating powerhouse—neutral beam injection. Last-phase assembly activities are underway on the STRIKE calorimeter at the ITER Neutral Beam Test Facility, as carbon tiles are installed on the supporting structure. STRIKE will be used on the first of the facility's test beds SPIDER, an ITER-scale negative ion source inaugurated last June. STRIKE is the most remarkable diagnostic planned for the SPIDER beam—the only one able to measure beam uniformity and divergence at the same time. The principle is quite simple: the calorimeter will present a perpendicular surface made of carbon fibre composite (CFC) tiles to the beam. The power deposited by the beam on the front side of the tiles will be propagated in form of heat to the rear side, where a set of infrared cameras will detect and analyze the thermal pattern in order to reconstruct beam properties. In order to preserve the pattern all the way through the calorimeter, it is fundamental to minimize the heat conduction along the directions perpendicular to the beam axis, while maintaining parallel conduction. For this reason, the tiles are made of carbon fibres that are packed and oriented in the direction parallel to the beam. Fabrication requires several months and is only possible in few locations around the world. To fully intercept the SPIDER beam—which occupies approximately one square metre—16 carbon fibre composite tiles are needed. The tiles are kept in place by a metallic structure whose position can be remotely controlled in order to diagnose the beam at different distances from the source. The structure is also equipped with electrostatic sensors and thermocouples to provide additional information. Even if the tiles are capable of sustaining temperatures in excess of 1,000 ˚C, they cannot withstand the full power (up to 6 MW) of the SPIDER beam for long periods; hence, for long pulses, the metallic structure of STRIKE opens to allow the beam to pass through and be intercepted further along by an alternative calorimeter, the actively cooled 'beam dump.' Thanks to this high-tech instrument, scientists will be able to perform precision analysis on the SPIDER beam.

Image of the week | The VIP door

Although adjacent and complementary to each other, the Tokamak Building and the Assembly Hall feel like two separate worlds: one is a labyrinth of hard concrete and raw steel, the other a vast open volume, home to shining new handling machines. Facing opposite directions, their respective entrances are hundreds of metres apart and passing from one to the other requires a long detour through the main thoroughfares of the ITER construction site. Or rather, required... A few weeks ago, a door was opened up in the temporary facade that separates the two buildings. The first person to pass through it was the Princess of Thailand when she visited ITER at the end of last year. For the moment, the door's main purpose is to facilitate VIP visits; soon it will be enlarged and connected to a corridor that will allow assembly workers to commute between the Assembly Hall and the Tokamak Pit.


Raindrops and fiery sightings: new research from around the world

At the Culham Centre for Fusion Energy (CCFE), researcher Fulvio Militello is working on a statistical model that compares the seemingly random movement of filaments (structures that emerge at the edges of the hot plasma) to the behaviour of raindrops. In the same way that each unique raindrop follows the same laws of physics (they hit the pavement), filaments that differ in strength, speed, size, amplitude or position follow certain rules as they move. Militello's model estimates collective behaviour in order to give scientists a tool to predict and control them. Read more about his theory on the CCFE website. In working with data from the DIII-D tokamak, physicists Ahmed Diallo and Julien Dominski from the Princeton Plasma Physics Laboratory (PPPL) have uncovered a trigger for a particular type of ELM—fiery bursts of plasma called Edge Localized Modes—that does not fit into present models. Their findings could shed light on the variety of mechanisms leading to the onset of ELMs and could broaden the portfolio of ELM suppression tools. Read the full report on the PPPL website.


1/8 - ITER : vers une révolution énergétique

Strom aus Kernfusion soll die Energiewelt revolutionieren

„Deutschland wäre einer der größten Profiteure von Fusionskraftwerken"