The ITER Neutral Beam Vacuum Vessel design

The Vacuum vessel of the ITER Heating Neutral Beam injector is a key component of the neutral beam system. It is host to the injector components and is also an extension of the ITER Vacuum Vessel. This article presents the s tatus of the design of the vessel. The first part of this article is dedicated to the presentation of the main design requirements. Besides the pressure and thermal load s, the various interfaces with other components are important constraints for the design . Some have specific requirements concerning displacement, or require specific featur es for their maintenance. Indeed all maintenance involving an opening of the vessel need s to be performed using remote handling systems. The second part aims at presenting the present desi gn of the NB vessel. Various concepts were studied before coming to the present day design. Structures were optimised to satisfy the RCC-MR code under the various loadin g scenarios applied to the vessel, both for normal and accidental cases. In addition, the vessel incorporates two sets of long lip seals which tolerate limited displacements. Lim iting the displacement is a real challenge considering the size of the flange and th e forces involved. An innovative solution has been developed to improve the mechanic al connection between the lids and the vessel walls in order to fulfil the requirement s. The vessel displacement is also important for the alignment of the Beam Line Compon ents with respect to the neutral beam and for the cryopumps interfaces. The geometry of the vessel was optimised to reduce the electric field stresses and to increase the voltage holding of the Beam Source, which is at 1MV. The present design satisfies all the requirements. The main issues have been solved, and the proposed design is now being optimised to f acilitate manufacturing.