you're currently reading the news digest published from 09 Oct 2023 to 16 Oct 2023

of-interest1
publication2
press21

featured

Wall conditioning | A coat of boron to capture impurities

Impurities, in the form of particles detached from materials inside the vacuum vessel, can be among a plasma's worst enemies. Even in trace amounts, they drain energy from the plasma, degrade its performance and lead in some cases to its complete collapse. In fusion machines, contamination of the plasma by impurities is mitigated two ways: at their source by implementing specific first-wall materials and 'wall conditioning,' and by preventing their penetration into the plasma through specific exhaust mechanisms such as divertors and cryopumps. There are many species of impurities, but one of the most deleterious is oxygen, which originates from the inevitable oxidation process in the materials inside the vacuum vessel. Oxygen release into the plasma can be limited by using a first-wall armour material that has a capacity to 'getter' oxygen atoms and strongly bind them in its atomic lattice. This capacity was one of the main reasons that justified using beryllium as the first-wall armour material in ITER; however, an updated understanding of the extensive implications of the use of beryllium has led ITER to reconsider its choice and opt for tungsten. No technological option is a panacea and choosing tungsten over beryllium implies a whole series of adaptations, modifications and, in some areas, the implementation of new processes. Experience accumulated from dozens of operating tokamaks has shown, for instance, that tungsten is not a good oxygen getter. How to make it better and more efficient? Thirty-five years ago, after close to ten years of research, an innovative technique called 'boronization' was developed for the Textor tokamak by Professor Jörg Winter and his team at the Forschungszentrum Jülich research centre in Germany. Boronization has been applied successfully on practically every fusion device since, with the exception of JET (which used beryllium as first-wall armour material). A few weeks ago, Professor Winter was at ITER to present the principles and challenges of the technique he pioneered. 'Boronization,' he explained, 'is the racehorse of wall conditioning. It is a plasma-chemical process that consists in coating the entire plasma-facing surface of a fusion device with a thin (~10-100 nanometres) boron layer.' Boron is a brittle and dark metalloid that has applications in the semiconductor and metalworking industries. During construction, ITER has used boron's appetence for neutrons in certain concrete formulations, and research is being conducted around the world on the 'ideal' aneutronic proton-boron fusion. These are not, however, the qualities that are central to the boronization process in fusion machines. What matters here, in Prof. Winter's words, is that 'boron getters oxygen like crazy.' Coating every square millimetre of first-wall armour with boron requires a technique that resembles, in its principle, the process used for plating objects with gold, silver, chrome or other metals. It consists in creating an electrical flow in a conductive environment, and using it to deposit particles on an object. The current originates from an electrode (an anode) with the object to be plated acting as a cathode. In the 'glow discharge' process used for boronization, anodes are used to create the electrical current flowing to the wall of the plasma chamber, which acts as a cathode. Once the magnetic field has been turned off, a gas containing boron is injected into the vacuum vessel chamber and submitted to a 'very mild' electrical discharge, like in a neon light, resulting in the gas acquiring the properties of an electrically conductive plasma. The ionized particles it contains are accelerated by the electrical field and, as their molecular bonds break upon impact with the wall, boron is deposited as a perfectly homogeneous, 'atomically clean' film on the wall's surface. The technique is 'easy to implement,' says Prof. Winter. Once boronization is complete after 5 to 10 hours of continuous controlled glow discharge, particles—and particularly oxygen—are trapped under or within the boron film and cannot be released into the plasma. Boronization creates optimal conditions for starting up plasmas. But as time passes and plasma discharges accumulate, the boron film becomes less efficient. On average, boronization is repeated every few weeks, 'but if you do a good job you can significantly extend the interval between two boronizations,' according to Prof. Winter. Boronization is routine—since 1991, it has been performed more than 100 times in the US tokamak DIII-D, for instance—but has never been experimented in a fusion device as large as ITER where approximately 700 square metres of first-wall surface need to be coated; there are also specific challenges when operating with deuterium-tritium plasmas. In addition, boronization requires equipping the ITER vacuum vessel with a number of additional glow discharge electrodes, dedicated fuelling lines for diborane, and specific equipment for which space availability must be identified. 'The boronization recipe stands,' says Prof. Winter—but in ITER it will require a completely new set of utensils.

Fusion world | More results from JET's record-breaking 2021 campaign

In 2021, researchers from the European consortium EUROfusion introduced the high-performance fuel mix of deuterium and tritium into the JET tokamak for only the second time in its history. The 'DTE2' campaign that followed produced a highly publicized world record for the most energy produced in a single fusion shot, and terabytes of data to be analyzed and modelled for the benefit of ITER and future fusion reactors. A more complete set of results has now been published in a special issue of Nuclear Fusion and will be presented in talks throughout the week at the 29th IAEA Fusion Energy Conference. The 40-year-old JET tokamak is unique in its ability to operate with the heavy hydrogen isotopes deuterium and tritium (DT), which fuse at temperatures that scientists and engineers can reach in a fusion installation (between 100 million and 200 million degrees Celsius). JET's DTE2 campaign, with a series of high-fusion-yield DT experiments, was designed to test crucial physics and technology aspects of reactor-relevant DT fusion plasmas ahead of ITER operation. In a press release published today, the EUROfusion consortium unveiled the main scientific results from the 2021 DTE2 campaign. 'One of our most eye-catching results is the first direct observation of the fusion fuel keeping itself hot through alpha heating. This is the process where high-energy helium ions (alpha particles) coming out of the fusion reaction transfer their heat to the surrounding fuel mix to keep the fusion process going,' said Costanza Maggi, a UKAEA Fellow and former JET Task Force Leader. 'Studying this process under realistic conditions is crucial to developing fusion power plants.' Self-heating plasmas are the key to producing electricity from fusion energy, allowing for sustained, ongoing fusion reactions despite strongly reduced input power from external heating sources. These important JET results on alpha heating are featured in a just-published special edition of Nuclear Fusion (click here) and also in Physical Review Letters. Other important results from the DTE2 campaign include the confirmation of predictions from advanced computer models for heat transport inside the plasma, successful tests of tritium recovery methods, the verification of a heating technique planned for ITER, and the successful demonstration of a control technique to protect the walls of the divertor. The JET team just brought a third and final campaign of experiments—DTE3, focusing on plasma science, materials science and neutronics—to a close last week. EUROfusion will be communicating about DTE3 results before the end of the year.

On site | There goes the unique spreader beam

Of all the lifting devices used on the ITER construction site, the circular spreader beam in the European Poloidal Field Coils Winding Facility was among the most spectacular and uncommon. Designed to transport coil windings (double pancakes) from one work station to the next, it was installed in late 2011 and performed its task until last year, when the last double pancake for poloidal field coil #3 (24 metres in diameter) was finalized. Attached to an overhead crane and capable of lifting up to 48 tonnes, the spreader beam was equipped with 24 lifting points, evenly distributed around its circumference. This arrangement, which could be adapted to the different diameters of the double pancakes to be handled (17 m for PF5 and PF2; 24 m for PF4 and PF3), prevented tilting and ensured an optimum balance when lifting and moving the load. Like the winding table, which was taken apart about one year ago, the spreader beam will not be needed anymore. Disconnected from its holding crane a few weeks ago, it was dismantled into its different segments. As for the crane, it remains in place: its 90-tonne lifting capacity will be put to use for whatever activities the building will accommodate in the future.

Tritium Building | Final concrete pour and other updates

Because most of its systems will only be needed when ITER operates at full nuclear power, work on the Tritium Building was put on hold in 2018, only to resume in the spring of 2021. Two-and-a-half years later, civil works and painting are complete at all levels from the second basement (B2) up to the third level (L3). Last week, the last 'significant concrete pour' was performed at the uppermost level (R2) of the building to create a 60-centimetre-thick slab for the aedicula sitting on top of the building. In parallel, work was progressing two floors below at level L4 where coats of smooth, shiny white paint were being applied to the walls and to the 10-metre-high ceiling of the 'vault annex.' Like the vault next door, the spectacular volume of the vault annex (a combined volume of 40,000 cubic metres) will accommodate equipment for the tokamak cooling water and tritium breeding systems.

of-interest

Apply now: SOFT Innovation Prize

Fusion researchers are constantly challenging the scientific state of the art and improving the technology. This drive lay the basis the conditions for innovation, much of which can be exploited in other sciences and industrial sectors for the benefit of society. The SOFT Innovation Prize rewards outstanding achievements in fusion energy research showcasing opportunities of valorization in the sector. It is intended for researchers and/or industrial actors who find new solutions, possibly with wider applications, to the challenges of fusion. SOFT stands for Symposium on Fusion Technology—the name of  conference where the prize is awarded. Following the success of the previous editions, the European Commission is holding the contest again in conjunction with SOFT 2024 (23-27 September 2024, Dublin, Ireland). There are no specific categories for this prize. Participants are free to submit an application concerning any physics or technology innovation that has been developed in magnetic confinement fusion research and that has market potential or has been taken up (or recognized) by industry to be further developed for the market. Entries will be assessed on originality and replicability, technical excellence, economic impact, exploitation, and plans for further development. Proposals are studied by an independent jury composed of experts in technology transfer, from business and academia. The deadline to submit applications is 16 January 2024. See further details on the SOFT Prize website.

publication

ITER Organization 2022 Annual Report

ITER Organization 2022 Financial Report

press

Special Issue of Papers Presenting Results from the JET Tritium and Deuterium/Tritium Campaign

IAEA Conference to Advance Global Fusion Agenda, Launch Outlook Report

FEC2023 opens: The IAEA, The International Centre of Fusion Energy past, present and future

IAEA Launches World Fusion Outlook 2023

IFMIF DONES: El acelerador de partículas allana el camino para sumar nuevos socios gracias al aval de expertos internacionales

A fúziós energiatermelést szupravezető mágnesek állítják pályára

First observation of how fusion keeps itself hot boosts confidence in ITER and future fusion power plants

UK's nuclear fusion site ends experiments after 40 years

Construction of fusion materials testing facility under way

« Le défi Iter était hors norme, mais nous touchons au but »

Hors Série : Quelles énergies pour demain ?

Construction of new fusion facility begins in Spain

Can German engineering solve the challenges of fusion?

Nuclear Fusion / Construction Begins Of Key €700 Million Facility In Spain (paywall)

29th IAEA Fusion Energy Conference (FEC 2023): Registration for Virtual Attendance as an Observer

L'intervista «La fusione nucleare è arrivata a un punto di svolta»

US Nuclear Regulatory Commission issues preliminary language for licensing and oversight of fusion energy systems

The star of the Swiss Plasma Center celebrates its 30th anniversary

La star du Swiss Plasma Center fête ses 30 ans

Учени от Физическия факултет на Софийския университет взеха активно участие на European Fusion Teacher Day 2023

ECRH antenna is coming back on WEST