The vessel called the cryostat will be home to the International Thermornuclear Experimental Reactor, the largest and the most advanced facility of its kind being built in Cadarache, France.
Scientists and engineers at the Institute of Plasma Research (IPR), Gandhinagar will manufacture this mammoth cryostat in segments at a cost of 100 million euros and ship it to France for being assembled at the site.
India is part of a seven nation consortium that is building the fusion reactor designed to produce 500 MW of output electricity with a power input of 50 MW.
ITER-India Project, a part of the IPR -- an autonomous unit of the Department of Atomic Energy, will make the `in-kind` contributions that form India`s share to the ITER project.
The procurement arrangement for the cryostat was signed recently by ITER-India.
"The cryostat is very crucial to the ITER experiment.It houses the fusion reactor in its entirety, including support to all internal systems," Shishir Deshpande, Project Director, ITER-India, told PTI.
Deshpande said the cryostat would protect the magnets from unwanted heat loads and help in keeping them in superconducting state.
"It also supports the entire mechanical, thermal and seismic load of the reactor and absorbs all the forces coming from fusion and magnetic forces," he said.
Welded together from thick stainless steel plates measuring between 40 and 180 millimetres, the cryostat forms the vacuum-tight container surrounding the ITER vacuum vessel and superconducting magnets.
It will have an outer diameter of 29 metres, be almost 30 metres tall weigh more than 3,500 tons, Deshpande said.
The steel cylinder will have 23 penetrations allowing access inside of the cryostat for maintenance.
It will also have over 200 penetrations some as large as four metres in size providing access to the vacuum vessel for cooling systems, magnet feeders, auxiliary heating, diagnostics, and the removal of blanket and divertor parts.
Large bellows are used between the cryostat and the vacuum vessel to allow for thermal contraction and expansion in the structures.
Given the huge size of the vessel, it will be fabricated in several pieces, each weighing about 100 tonnes, and transported to France by sea.
The supply of components is expected to take place between 2014 and 2017 and onsite fabrication and installation at Cadarache is scheduled to be completed by 2019.