Slow burn9 February 2017
We review the key developments in nuclear fusion over the last 12 months. In addition to progress on the international Iter project, there have been achievements in China, South Korea and Europe.
Anew schedule for the International Thermonuclear Experimental Reactor (Iter) fusion project was approved by the Iter Council in November 2016. It confirmed that first plasma is now scheduled for 2025 and the start of nuclear, or deuterium-tritium operation, for 2035.
Iter, under construction at the Cadarache nuclear site in southern France, will be the world’s largest experimental fusion facility. Iter’s successor, the Demonstration Fusion Power Reactor, or DEMO, will aim to demonstrate the continuous output of energy, supplying electricity to the grid. According to Eurofusion, DEMO is expected to follow Iter by 2050.
Thirty-five nations are collaborating to build Iter, a tokamak magnetic fusion device. Construction began in 2010. Iter’s November statement rubber-stamped a decision taken in June, when the Iter Organisation, whose work is overseen by the Iter Council, announced an updated schedule.
Iter said project construction and manufacturing has sustained “a rapid pace” for the past 18 months. However, Reuters reported that construction will cost almost four times the original estimate.
When the project was formally launched ten years ago it was at an estimated cost of €5bn.
First plasma was originally scheduled for 2018, and the start of deuterium-tritium operation set for 2026. In July 2010 the Iter Council agreed a new schedule with first plasma slated for November 2019, with deuterium-tritium operation in March 2027.
By 2011, the budget forecast had risen to about €16bn and in May 2016 new Iter chief Bernard Bigot said Iter would be delayed by more than a decade and incur another €4bn of cost overruns. He confirmed this in October, estimating the overall cost to commissioning to be around €18bn. “For the first time, we have a reliable estimate... In the past there was no realistic schedule, no detailed appreciation of the cost... It was much underestimated,” he said. A precise estimate is difficult as partner countries contribute most of their shares in the project by producing components. “Many domestic agencies do not want to disclose their exact costs,” he said, adding the running cost of the Iter Organisation plus the domestic agencies in the partner countries is about €200m a year.
Thousands of engineers and scientists have contributed to the design of Iter since the idea for an international joint experiment in fusion was first launched in 1985. Europe is responsible for the largest portion of construction costs (45.6%); the remainder is shared equally by the other members (9.1% each).
To date the ground floor has been completed of a complex that will house the tokamak reactor, diagnostics and tritium buildings, according to Fusion for Energy (F4E), the EU agency providing the European contribution. F4E said progress on the first floor of the complex varies, from 35% on the tritium building to 99% on the diagnostics building.
In October F4E signed a €100m deal to develop robotics equipment for the Iter facility. The contract, with Airbus Safran Launchers (France-Germany), Nuvia Limited (UK) and Cegelec CEM (France), will run for seven years. The UK Atomic Energy Authority (UKAEA), Instituto Superior Tecnico (Portugal), AVT Europe NV (Belgium) and Millennium (France) will also be part of the contract, which will deliver remotely operated systems for the transportation and confinement of components in the Iter vacuum vessel.
F4E, Oxford Technologies in the UK and the Katholieke Universiteit of Leuven in Belgium have developed an electronic chip that can perform in a radiation environment and could serve as a prototype for other electronics. The chip, which has been in development for five years, has been irradiated at the SCK-CEN research centre in Belgium and the results are promising, Iter said.
Russian Domestic Agency Iter has signed the two final contracts to supply 25 Iter systems. Of these, ten are process systems and components, and 15 are systems for diagnostics. In 2016, RUB2.9bn ($41m) was allocated in Russia’s budget to finance the activities of the Russian companies involved.
NRG at Petten in the Netherlands is preparing to use its high-flux reactor (HFR) to test the operation, integrity and quality of the “first wall” that will shield the nuclear fusion process at Iter. The first (innermost) wall comprises beryllium tiles welded onto a copper-chrome-zircon alloy enclosed in a stainless steel construction. Mock- ups will be placed in the reactor core at Petten and exposed to intense neutron radiation. “This enables us to simulate the radiation environment and temperatures in Iter,” said Sander de Groot of NRG.
HFR can simulate potential radiation damage during Iter’s life and determine how long components can withstand it. After irradiation the irradiated mock-ups will be transported to the Jülich research centre in Germany, where they will be exposed to an extremely high heat flux and intense variable thermal radiation to see how they withstand Iter’s extreme heat load.
The first of three Chinese-supplied electrical transformers has been installed. Two other transformers are due to arrive from China in early 2017.
Iran is also seeking to join Iter. In July, Ali Akbar Salehi, head of the Atomic Energy Agency of Iran, visited Cadarache for talks with Iter officials. Bigot said Iran would like to consider how to join the project, “but clearly not as a full member”. Iran is already studying the development of nuclear fusion and has smaller laboratory tokamak machines.
Meanwhile, the UK’s Culham Centre for Fusion Energy (CCFE) and the Joint European Torus (JET) have continued experimental work as the precursor to Iter. JET is operated by the CCFE under a contract between the European Commission and the UKAEA. It is used by all European fusion laboratories in the Eurofusion consortium.
In November CCFE head (and UKAEA chief executive) Ian Chapman dismissed press speculation that Britain’s decision to leave the EU would undermine the project (see also viewpoint on p18).
JET’s 2015-16 experimental campaign, which ended on 15 November, included: the rehearsal of procedures for future tritium-tritium and deuterium-tritium experiments; a hydrogen campaign during which physicists learned about the dependence of plasma parameters on the mass of the hydrogen fuel used; and a high-power deuterium campaign. Upcoming campaigns will include tritium-tritium and deuterium-tritium experiments.
A number of other fusion projects worldwide announced significant milestones during 2016.
The Korean Superconducting Tokamak Advanced Research (KSTAR), a tokamak nuclear fusion reactor, achieved 70 seconds in high-performance plasma operation, South Korea’s National Fusion Research Institute (NFRI) said in a December statement. NFRI said a fully non-inductive operation mode using a high- power neutron beam had been used. Various techniques, including a rotating 3D field, had been applied to alleviate the accumulated heat fluxes on the plasma-facing components.
While other reactors have managed to sustain plasma for longer than 70 seconds, KSTAR produced a high-performance plasma, which is better suited for nuclear fusion. Researchers at NFRI have also developed a new plasma operation mode, which should enable reactions to handle greater pressures at lower temperatures.
KSTAR’s research will focus on “the mission essential for the fusion reactor beyond Iter”, the institute said. “It includes a new efficient mode of operation and a new divertor concept suitable for the Korean fusion demonstration reactor, the K-DEMO device.” KSTAR was the first tokamak to feature a fully superconducting magnet system with a central solenoid, toroidal and poloidal field coils.
China also announced a fusion breakthrough in December. Researchers at the Experimental Advanced Superconducting Tokamak (EAST) at the Hefei-based Institute of Plasma Physics claimed to have independently invented components to keep ionised gas burning steadily for twice the time of the previous record. This included a component for a fusion reactor core that can withstand extremely high temperatures. The component is intended to be installed at Iter, and is about 20% more heat-resistant than the reactor’s design requires, China said.
EAST deputy director Professor Luo Guangnan said some previous fusion experiments had lasted for more than 100 seconds, but they were “like riding a bucking bronco”, with plasma that was volatile and difficult to control. However, in an experiment conducted at EAST in August, the plasma was tamed in a high-performance steady state, known as H-mode. EAST is an experimental superconducting tokamak magnetic fusion energy reactor, which began operating in 2006.
The goal of EAST is to reach 100 million degrees in the plasma for 1000 seconds. These recent experimental results and all of the progress on EAST will be available to Iter.
First plasma was also reported in December for WEST, formerly known as Tore Supra, a plasma facility near Cadarache owned by France’s Commissariat à l’Énergie Atomique (CEA).
Tore Supra began operating in 1988 and upgrading it to become WEST required an extensive refit, beginning in 2013. The reactor was upgraded to undertake research to support Iter.
WEST is the acronym for “‘W Environment in a Steady-state Tokamak”, where W is the chemical symbol for tungsten, the material that will be used for the Iter divertor. CEA will use WEST to minimise the cost and schedule risks of industrialising Iter’s components by testing prototypes. It will also give initial findings on the functioning of the divertor and test the durability and ageing of tungsten materials.
US and Germany
In September, the US’s, Alcator C-Mod tokamak nuclear fusion reactor at the Massachusetts Institute of Technology (MIT) set a new world record for plasma pressure of 2.05 atmospheres. This was 16% better than the previous record of 1.77 atmospheres, set at the same facility in 2005 at a temperature of 35 million Celsius and lasting for two seconds. Professor Robert McCrory of the University of Rochester, New York, said the result confirms that the high pressures required for a burning plasma can be best achieved with high-magnetic-field tokamaks such as Alcator C-Mod.
Sadly, funding from the US Department of Energy has now ended. MIT said the world record was achieved on the last day of the tokamak’s operation.
Earlier in December 2015, the Wendelstein 7-X (W7-X), the world’s largest stellarator, had begun operating at the Max Planck Institute of Plasma Physics in Greifswald, Germany. It plans to be able to operate with up to 30 minutes of continuous plasma discharge by 2021.
The W7-X aims to show that the earlier weaknesses in the stellarator fusion concept (an alternative to the tokamak) have
The first experimental campaign ended in March. Modifications in the plasma vessel are now underway to make the device fit for higher heating powers and longer pulses.