Stainless Steel
Friday | 20 April, 2012 | 2:05 pm

Nuclear design

By Julie Sammarco

Outokumpu supplies quarto plate for a fusion nuclear research project

April 2012 - Outokumpu, Espoo, Finland, will supply 350 tons of quarto plates for JT-60SA, a fusion experiment project in Japan.

JT-60SA is designed to support the operation of ITER (International Thermonuclear Experimental Reactor) and investigate how to optimize fusion power plants that are built after ITER. It is a joint international research and development project involving Japan and Europe and will be built in Naka, Japan, using the existing infrastructure of the JT-60 Upgrade experiment. SA stands for super advanced because the experiment will have superconducting coils and study advanced modes of plasma operation.

Fusion is the energy source of the sun and the stars. On Earth, fusion research is aimed at demonstrating that this energy source can be used to produce electricity in a safe and environmentally benign way. With abundant fuel resources, it could meet the needs of a growing world population.

Theoretical advantages of fusing atoms, instead of splitting them as done in commercial reactors today, include a higher energy output per fuel unit used as well as waste that is almost radiation-free.

“In simple terms, the idea of this research is to explore if it is possible to produce commercially viable energy from fusion,” says Nora Berg, communications officer at Outokumpu.

Although the project began its operation, commissioning, assembly and construction phases in 2007, it has several phases that won’t begin until 2016.

Stainless steel applications
The stainless steel quarto plates, made out of low-cobalt 304, will be used in the cylindrical section of the cryostat, which is the hull surrounding the main components of the Tokamak reactor. The Tokamak is a device for containing a plasma inside a torus chamber by using a combination of two magnetic fields—one created by electric coils around the torus, the other created by intense electric current in the plasma. Fabrication of the cryostat vessel body cylindrical section will be done in Spain for the Japan Atomic Energy Agency.

Stainless steel is used in bottom, body and top sections of the cryostat. Approximately 350 tons are used in the bottom, some 350 tons in the body and roughly 70 tons to 80 tons on the top. The bottom part is currently in production in IDESA, the project’s engineering and design site in Gijon, Spain.

According to Berg, an austenitic stainless steel grade was used for the cryostat because it meets certain strict needs, such as low cobalt requirements in this particular application and high standards for product safety and reliability.

Although stainless steel is used in the cryostat, Berg notes it is not the focus in this project.

"Outokumpu has a long track record in supplying stainless steel to the nuclear industry where projects have high standards for product safety and reliability. Stainless steel with low cobalt content is used in core structures in nuclear equipment where, for example, corrosion resistance, permeability and cleanliness requirements are decisive," said Hirokuni Yoshida, head of Outokumpu’s sales office in Japan, in a press release.

Construction of the JT-60SA will take place in Naka, Japan, under the Satellite Tokamak Programme as part of the Broader Approach agreement signed between Japan and the European Atomic Energy agency.

While underway, the JT-60SA project currently does not have a completion date listed. MM

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