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Procurement of in-wall shielding
After the signing of the Vacuum Vessel Procurement Arrangement by the ITER Organization on 7 October, the vacuum vessel group launched the Procurement Arrangement for in-wall shielding with a kick off meeting on Wednesday 22 October in the presence of Haresh Pathak from the Indian Domestic Agency.
The ITER vacuum vessel is a double-wall box structure, with a space between the inner and outer shells that is filled with pre-assembled or modular blocks. These blocks are called "in-wall shielding." There are two types of in-wall shielding: primary in-wall shielding provides effective neutron shielding, while ferromagnetic inserts provide neutron shielding and reduce the toroidal field ripple.
The Indian Domestic Agency is in charge of the procurement and delivery of more than 6,000 shielding blocks for installation into the vacuum vessel sectors being manufactured in Korea and Europe, while yet more blocks will be delivered to ITER for installation in the field joint regions when the vacuum vessel sectors are assembled in-pit. The weight of each neutron shielding plate can vary between 50 and 500 kg depending on its location.
The space between the inner and outer shells of the vacuum vessel is also used for cooling and so the in-wall shielding blocks will be exposed to water. Understandably there was concern regarding corrosion and the radiation levels of the cooling water. Other topics included interfaces with the in-wall shielding, electromagnetic loading, and ferromagnetic material distribution.
The deadline for the completion of the Procurement Arrangement is 20 November, followed by signature by the Indian Domestic Agency by the end of December 2008.
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