Manufacturing
In the cradle of the cryostat
3 Dec 2018
-
Robert Arnoux
On the northwestern coast of India, facing the Arabian Peninsula, Hazira is one of the subcontinent's major industrial hubs. Under the still-blazing autumn sun, the landscape is one of refineries, shipyards, power plants, storage tanks and endless queues of oil and container trucks. It is here, at the Larsen & Toubro Ltd manufacturing complex, that a critical ITER component is taking shape.
A formidable industrial venture that began in 2015 is nearing its end. At the Larsen & Tourbo Hazira manufacturing complex, work is underway on the two last orders the company is filling for the ITER cryostat: segments of the 430-tonne upper cylinder and top lid.
Between ocean and mangrove, amidst a world of dust and rust, the Larsen & Toubro Ltd "campus" is like an oasis of green and cool. In the mid-1980s, the mammoth Indian conglomerate drained close to one thousand acres of marshland to establish this multi-facility complex.
Thirty years later, the place is a unique aggregation of manufacturing facilities that turn out offshore oil platforms at the rate of 10 to 12 per year and manufacture ships, submarines, tanks, giant boilers and turbines ...
At one kilometre long, the west campus' special steels and forging facility is one of the largest in the world. In an atmosphere that mixes space-age technology with a 19th century steel mill atmosphere, "manipulators" the size of freight train locomotives slowly move amidst giant furnaces and massive steel ingots laid to cool on sand beds. The facility produces more than 40,000 tonnes of finished forgings annually.
Across the road on the east campus, administrative buildings, fabrication facilities, workshops and port installations cover close to one hundred hectares.
Final dimensional inspection is being conducted on an upper cylinder sector for the ITER cryostat. Seven segments are packed and ready for dispatch; another two are undergoing finishing works and inspections.
This environment is the cradle of the ITER cryostat, the largest of the Tokamak's components—a giant, leak-tight cylinder 30 metres high and 30 metres in diameter that will act as a "thermos" to insulate the ultra-cold magnets from the environment.
From humble beginnings in the form of ingots that look strangely like truncated Doric columns, to the shining stainless steel segments ready to be shipped to the ITER site, it all happens here.
Since late 2015, segments for the ITER cryostat's base section and lower cylinder have been successively forged, machined, finalized, shipped to the ITER construction site, and assembled and welded in the onsite Cryostat Workshop.
In December 2013, as the first mockups were produced to demonstrate and validate welding and manufacturing sequences and techniques, Madhukar Kotwal, then president of Larsen & Toubro Heavy Engineering, told Newsline that despite the company's accumulated experience in manufacturing nuclear and space components, the ITER cryostat was so "special" that it presented unprecedented challenges, both technical and organizational.
Five years later, the challenges have been met and overcome and the manufacturing of the segments for the "huge assembly" of the ITER cryostat is nearing its end.
In the east campus, inside Medium Fabrication Shop #4, work is now underway on the last two orders that Larsen & Toubro is filling for the ITER cryostat: seven segments of the 430-tonne upper cylinder are packed and ready for dispatch; another two are undergoing finishing works and inspections; a segment prototype for the 655-tonne top lid is in the last stage of fabrication; and various tasks are being performed on the "ribs," "flanges," "knuckles," and "crown" that make up a top lid segment (see further technical detail in the photo gallery below.)
Although 7,000 kilometres and three and a half time zones stand between the Larsen & Toubro teams in Hazira and those on the ITER worksite, communication between them is constant. "We have a conference call every single working day," says Chirag Patel, the Larsen & Toubro project manager for the ITER cryostat and in-wall-shielding (see box). "And we will soon be implementing Wi-Fi-connected viewing goggles that will enable us to have a better visual assessment of the ongoing works in the Cryostat Workshop at ITER."
In the summer of 2019, the 12 top lid segments will be shipped to ITER, marking the end of a formidable industrial venture that has spanned two continents and involved hundreds of specialists in both Hazira and at the ITER site in Saint-Paul-lez-Durance.
Click here to watch the "Made in India" video.
Guided by Anil Parab, the Executive Vice President of Larsen & Toubro's Heavy Engineering division (second from left), ITER Director-General Bernard Bigot visits Larsen & Toubro's Hazira facility on 23 October. Also present are Johannes Schwemmer and Kijung Jung (respectively head of the European and Korean Domestic Agencies) and by representatives of the Indian Domestic Agency.
The most spectacular of all the facilities in the Larsen & Toubro Hazira complex is the one-kilometre long foundry that produces 40,000 tonnes of finished forgings annually. Among them are the steel ingots that are pressed and machined into ITER cryostat segments.
Welds, welds and more welds ...
Despite Larsen & Toubro's extensive experience in manufacturing for the nuclear and space industries, new processes and techniques had to be specifically developed for the welding of the cryostat segments. Pictured here: the welding of two segments for the top lid.
As work is being finalized on a tier-two segment of the cryostat upper cylinder, T-ribs for the top lid are being prepared for welding. The top lid is made of 12 segments that each comprise ribs, knuckles and a crown.
These tier-two upper cylinder segments are being packed and conditioned for the long journey to the ITER site. In the on-site Cryostat Workshop, Larsen & Toubro contractors will weld tier-one segments first, then position tier-two segments on top. Upper cylinder segments will begin arriving at ITER in March 2019.
The 655-tonne top lid will be the last of four cryostat sectors to leave the Larsen & Toubro factory (in segments). Before series manufacturing began, a prototype segment was manufactured in order to check potential profile distortions. All 12 top lid segments will be ready for dispatch in the summer of 2019.
Inside Medium fabrication shop # 4
On their way back from lunch, workers at Larsen & Toubro's Hazira faility pass by ongoing works for the ITER cryostat inside Medium Fabrication Shop #4.
Ready for dispatch
A small-size mockup of the ITER cryostat sits in front of an upper cylinder segment ready for dispatch. Once assembled in the ITER Tokamak Pit, the 30-metre-wide cryostat will represent 3,850 tonnes (approximately 16% of machine weight).
The quality control team inspects a 120-millimetre-thick upper cylinder flange. As a vacuum chamber, the leak-tight quality of all welds must be irreproachable.
"Submerged arc welding" (SAW) is the technique used in the welding of these two top lid plates. The molten weld and the electric arc zone are protected from oxydation by being "submerged" under a flux of small grains of carbon, manganese and silicon. The "HZMC" on the welder's overalls stands for Hazira Manufacturing Complex.
Thousands of plates, thousands of shapes
In-wall shielding plates--assembled into blocks--will fill 55% of the space between the double walls of the vacuum vessel. Their role? To shield components outside the vacuum vessel from the neutrons generated by the fusion reaction and contribute to the confinement of the plasma's fast particles. The ITER machine will require 50,500 such plates, each unique in shape, size and weight.
Due to the geometry of the vacuum vessel, the in-wall shielding plates (and hence the blocks) are unique. Once assembled, the blocks are shipped to the vacuum vessel manufacturers in Korea and Europe.
It takes between one and eleven in-wall shielding plates to form a block. In late October, some 160 blocks (representing close to 500 plates) were ready to be shipped from the Hazira facility to the Korean manufacturer in charge of producing four vacuum vessel sectors for ITER.