Where vessels are born

29 Oct 2013 - Robert Arnoux

This ��ƽ�� component seen in the shop at Hyundai Heavy Industries in Ulsan, Korea is the upper section of the inner shell of vacuum vessel sector #6—only a small piece of the full component. Still, it's a towering presence in this giant hall, one that dramatically conveys the industrial dimension of the ��ƽ�� project.

As General Manager of the marketing and sales department at Hyundai Heavy Industries (HHI), B.K. Chung has seen many a vessel come off the production line. In Ulsan, Korea the company's giant shipyard puts out more than one hundred large ships per year (tankers, container ships, etc.) and accounts for 15 percent of the world's shipbuilding capacity.

However of all the vessels that the company produces, one is unique. It is a vessel that will never take to the sea, one that will remain anchored for some thirty years amid the hills of Haute-Provence: the ��ƽ�� vacuum vessel.

Within the scope of its in-kind procurement to the ��ƽ�� project, it is Korea's responsibility to produce and deliver two of the nine sectors (#1 and #6) and 35 of the sets of ports that form the ��ƽ�� vacuum vessel. (Korea will also manufacture toroidal field on behalf of ��ƽ�� Japan.)

Following the contract signature in and the production of real-size in 2011, HHI launched the fabrication of the actual components in October 2012. It plans to have all four segments (upper, inboard, equatorial and lower) of the two vacuum vessel sectors complete by 2016, then welded and ready for shipping to the ��ƽ�� site in 2017.

Although the company has acquired considerable experience in cutting, forming, machining, welding and drilling steel structures—and although it is not new to fusion, having manufactured the core components of the tokamak in the early 2000s—the production of sectors for the ��ƽ�� vacuum vessel presents some unique challenges.

In Ulsan, Hyundai Heavy Industry's giant shipyard puts out more than one hundred large ships per year (LNG carriers, container ships) and accounts for 15% of the world's shipbuilding capacity. © Hyundai Heavy Industries

"It is a real challenge for us to overcome the difficulties of welding, non-destructive examination and tolerances due to the very unique shapes of the components," explains Byung-Ryul Roh the general manager of the Nuclear Power Department in HHI's Industrial Plant & Engineering Division. "However, the R&D acquired on the mockups has provided our engineers with all the necessary technologies."

The ��ƽ�� vacuum vessel, which forms the first standing barrier between the nuclear plasma and the environment, is one of the main ��ƽ�� Safety Important Class () components. It is also an ESPN component (équipement sous pression nucléaire, equipment under nuclear pressure) as defined by the French nuclear safety regulations that ��ƽ�� observes. As such, it is an extremely demanding piece of high technology.

The "��ƽ��-grade" steel that is used in vacuum vessel fabrication (supplied by Industeel France, formerly Creusot-Loire) requires specific welding techniques. Welding distortion has to be kept to a minimum, tolerances are very tight, and sophisticated non-destructive examination techniques must be implemented with utmost care and precision. Adding to these difficulties, ��ƽ��—with all of its organizational complexity—is very different from HHI's "normal" clients.

Although the company has experience in the domain of fusion, having manufactured the core components of the KSTAR Tokamak in the early 2000s, the production of sectors for the ��ƽ�� vacuum vessel presents some unique challenges. © Hyundai Heavy Industries

However daunting the challenge, the feeling in Ulsan is one of confidence. Carrying out the work for KSTAR added precious fusion expertise to the company's 40 years of experience and no one here doubts that the difficulties will be overcome.

Twenty months have elapsed since the company began high-pressure water jet cutting the 2 x 6 metre, 60 millimetre-thick steel plates that constitute the raw material of the ��ƽ�� vacuum vessel. Press forming followed, then heat treatment to release the tension inside the metal, machining, welding (five different plates for the upper segment) and drilling (75 holes for the inner shell of the upper segment alone, counting 11 hours to drill a single hole).

After R&D work, the company launched fabrication in October 2012 and plans to have all four segments (upper, inboard, equatorial and lower) of the two vacuum vessel sectors complete by early 2016, then welded and ready for shipping in 2017.

This long and painstaking process to produce the inner shell of Sector #6 to demanding ��ƽ�� specifications will be replicated for all of the vacuum vessel components that Korea is responsible for. But that's not all.

Because seven other vacuum vessel sectors will be manufactured by , HHI must also take into account the issue of interfaces. "We've had meetings with European manufacturers but it is not sufficient. What we need now is detailed discussions on a regular basis," says Chung.

Although the ��ƽ�� contract is the equivalent in value of two supertankers, ��ƽ�� activities occupy a very small place within the huge HHI Ulsan shipyard and represent only a portion of the company's sales. "It is small yes," agree Chung and Roh, "but it is very significant for the fame of our company."

Observing a large and strategic ��ƽ�� component slowly taking shape in a workshop some 10,000 kilometres away from the ��ƽ�� site is a stirring experience. It may only be one small piece of the vacuum vessel—still, it's a towering presence in the giant hall, one that dramatically conveys the industrial dimension of the ��ƽ�� project.

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