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Procurement of the in-wall shielding

-Peter Readman

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After the signing of the Vacuum Vessel (VV) Procurement Arrangement by IO on 7 October, the VV group launched the PA for the In-Wall Shielding (IWS) with a Kick Off meeting on Wednesday 22nd October in the presence of Haresh Pathak from the Indian DA.

The ITER VV is a double wall box structure and the space between the inner and outer shells of the VV is filled with pre-assembled or modular blocks. These blocks are called "in-wall shielding". There are two types of IWS: primary IWS provides an effective neutron shielding, while ferromagnetic inserts provide neutron shielding and reduce the toroidal field ripple.

The Indian DA will fabricate and deliver more than 6000 shielding blocks for installation into the VV sectors in Korea and the EU, while yet more blocks will be delivered to ITER for installation in the field joints regions when the VV sectors are assembled at Cadarache. 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 VV is also used for cooling and so the IWS 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 IWS, electromagnetic loading and ferromagnetic material distribution.

The deadline for the completion of the PA is 20 November, followed by signature by the Indian DA by the end of December 2008.


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