It takes many months for a single forged block of stainless steel to be transformed into the complex shape of an ITER blanket shield block, full of gullies, channels, gaps, and cutouts. In Korea, series production is underway and a major milestone has been achieved: the successful testing and certification of the first production unit.
These massive components measure about 1 x 1.5 metres (for 0.5 metre of thickness) and weigh about 4 tonnes. For perspective, that's about as far as your arms can reach and equivalent in weight to several small cars.
Eighteen rows of blanket shield blocks (440 individual blocks) will line the inner surfaces of the ITER vacuum vessel to protect the steel of the vessel as well as the coil systems from fusion neutrons.
Very few of the shield blocks are identical, making this a complex industrial package. The variations in design are related to the specific position of the shield blocks in the vacuum vessel (driven by the local geometry in the inboard and outboard regions) as well as the space requirements of interfacing systems such as plasma heating and diagnostics.
The Domestic Agencies of Korea and China are procuring 220 units each. The blanket shield blocks—and their front-facing first wall panels
—are required on site at ITER in time for installation during Assembly Phase II (2026 to 2028).
The basic fabrication method for a shield block involves the extensive transformation of a forged stainless steel block through precise machining, deep hole drilling, and the welding of cover plates over the cooling channels; a number of deep slits are also machined into the shield block for the purpose of reducing the impact of electromagnetic loads.
As a final fabrication step, the components undergo non-destructive examination at the factory as well as hydraulic pressure and hot helium leak testing.
The blanket shield blocks cover approximately 600 m² inside the ITER vacuum vessel and—depending on location—the shape and internal space requirements can vary. There are approximately 32 major and 100 minor design variants.
ITER Korea has been cooperating with domestic industries EM Korea Co., Ltd., and Vitzrotech Co., Ltd. since 2017 to manufacture and test its portion of the shield blocks, with actual series production beginning in August 2019 after the completion of qualification activities including the fabrication and testing of a full-scale prototype.
On the inboard and outboard walls inside the vacuum vessel are 440 blanket modules, arranged in rows. Each one is made of a blanket shield block and front-facing first wall panel.
The first series production unit, SB06A—for row 6 (situated near the top of the vessel on the inboard wall of the chamber), type A—has now been completed in Korea, including factory acceptance tests and the production of all required documentation. For future series production units, it is expected that the manufacturing can be accelerated through the experience gained and strong production and quality management systems.
Rene Raffray, Blanket Integrated Product Team Leader, congratulated Korean colleagues on the achievement of this important milestone. "This is not only the first series production shield block to be completed in Korea but also the first major series component of the blanket system to be successfully manufactured and tested, and as such it is a major step forward. It also testifies to the strong progress in the procurement of the shield blocks and to the productive collaboration between the ITER Organization and the procuring Domestic Agencies."
The Director-General of ITER Korea, Kijung JUNG, took pride in the accomplishment, saying: "We are happy to be engaging in some of the most difficult challenges in terms of fusion technology, so that our industry will be ready for the commercialization of hydrogen fusion. After the recent successes on the ITER vacuum vessel
, we know we are strengthening the capabilities of our domestic industries through participation in ITER."
In parallel, procurement is also progressing well in China
, with all shield blocks in rows 09 and 10 in series production, as well as several for row 17. Final machining has been completed on one row 10 shield block and final factory acceptance tests are underway.