Target systems at ESS-Bilbao.
Spain was one of the first countries to send a Letter of Intent committing to the construction of the European Spallation Source, and a close collaboration has followed. In November 2014, ESS-Bilbao was chosen as the in-kind partner for the ESS target system.
“Working with ESS-Bilbao gives us access to the experience and capabilities of the Spanish nuclear industry,” says John Haines, head of the ESS Target division. “Beyond that, ESS-Bilbao has a focus just like our own, namely, making ESS a reality. Their dedication to the project is very valuable to us.” ESS is highlighting this collaboration during the Spanish Partner and Industry Day, held Thursday, April 16, in Bilbao.
ESS-Bilbao is a centre for neutron technologies with a staff of 60 scientists and engineers. It is a consortium in which the Spanish State Government and the Basque Autonomous Region each hold an equal stake. A team of 10 scientists and engineers, based in Madrid, is dedicated to the ESS target wheel systems, where they maintain close interaction with the Instituto de Fusión Nuclear. This team produced the shaft and mock-up target for the Oak Ridge National Laboratory’s Spallation Neutron Source Second Target Station (SNS STS) in 2009, where they gained the vital experience necessary to produce the ESS target system.
“To be working on the ESS target is a technological and scientific challenge, and an extraordinary opportunity for us,” says Fernando Sordo, lead engineer of the target wheel In-Kind Contribution (IKC) at ESS-Bilbao. “We are excited to be contributing to a major element of ESS that is fundamental for the functioning of the facility.”
The target system is where the process of spallation takes place, that is, where the neutrons to be used for scientific research at ESS are generated. In the target wheel, the highly energetic proton beam pulse of the ESS accelerator interacts with the tungsten in the target wheel to generate neutrons, while the energy deposited in the wheel is removed via a system of helium coolant passages. The moderator-reflector systems, oriented above and below the target wheel, slow down (or moderate) the fast neutrons emitted by the target to a speed suitable for the scientific research performed on the ESS instruments.
The ESS target baseline design was developed after the ESS site decision in 2009, and a working group was established to further explore the design possibilities. According to the 2013 ESS Technical Design Report, the choice to use a helium cooled, rotating tungsten target was based on two key factors: environmental and conventional safety perspectives; and to provide the highest possible scientific performance at a reasonable cost.
The tungsten wheel concept
The target wheel will measure 2.5 meters in diameter, is estimated to weigh 4 tonnes, and is divided into 36 radial sectors. The heart of the target station is the roughly 7,000 tungsten bricks set into the sectors of the wheel.
Sordo and his team at ESS-Bilbao are currently in the process of modifying the target system proposal to achieve a design that can be manufactured more easily. “Focusing on design efficiency now will make it easier to meet the challenge of manufacturing and testing later,” says Sordo. The current ESS-Bilbao proposal has specifically modified the geometric arrangement of the tungsten bricks such that protons will not cross the target without a spallation interaction.
“We have had a great start to the collaboration with ESS-Bilbao,” notes Haines. “They really hit the ground running. They hosted the target wheel, shaft, and drive unit kick-off meeting at the end of January 2015 and have already submitted a modified design proposal for the target wheel. This design is much easier to manufacture and more robust.”
Spanish Partnery & Industry Day
The current status of the design, and other collaboration possibilities, will be presented at Thursday’s Spanish Partner and Industry Day in Bilbao. The event will provide an overview of ESS and offer opportunities for industry to interact with ESS and ESS-Bilbao.
“Building the highest powered spallation target in the world will position the Spanish engineering industry in the field of neutron science,” says José Luis Martínez Peña, CEO of ESS-Bilbao. “The work will also foster collaborations between national academia and industry, as suppliers will be hired to manufacture and test the designs. This in return will fuel the Spanish national innovation potential by building capacity and supporting job growth.”
Fernando Sordo (bottom row, second from left) and the ESS-Bilbao target systems team. PHOTO: ESS-Bilbao
The Swedish-Basque Collaboration
in the 18th and 21st Centuries
Tungsten, in the form of 7,000 small bricks, will constitute the core of the ESS target wheel that is being constructed by ESS-Bilbao in the Spanish Basque country. This particular Swedish-Basque scientific collaboration, as it happens, extends back to the discovery of tungsten in the 18th century.
The tungsten ore, scheelite, was discovered in 1750 in Dalecarlia province in north-central Sweden by Carl Wilhelm Scheele, who gave tungsten its Swedish name, tung (heavy) and sten (stone). Thirty years later, a native of the Basque country, Juan José de D’Elhuyar, studied metallurgical chemistry in Uppsala, Sweden, with Torbern Bergman who suggested a method for isolating the single metal.
In 1783, D’Elhuyar returned to the Basque country and worked with his brother Fausto Jermin to execute Bergman's idea. They succeeded, published, and were credited with the discovery of what would become element #74 in the Periodic Table. The D'Elhuyar brothers named the new metal volfram, which in turn became the Swedish word for tungsten. The Spanish, however, went with tungsteno.
Scheele, the Swede D'Elhuyar, the Basque
Source: the International Tungsten Industry Association website.
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