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Manufacturing experience of large size austenitic stainless steel inner vessels (I&II) for sodium technology complex

  • Posted on: 27th May, 2023

Sodium Technology Complex (STC) is an upcoming test facility at IGCAR for testing and qualification of large size (full scale) fast breeder reactor components before the installation and commissioning in the nuclear reactor.

Two large sizes InnerVessels (IVs) (ID 830 × 13000 mm long × 10 mm thickness & ID 780 × 13000 mm long × 10 mm thickness) for Sodium Test Vessels (STV) were successfully manufactured confirming to ASME Section VIII, division-1 code for elevated temperature in-sodium testing at STC. The primary material construction of inner vessel is from AISI 316 LN.

The IV-1 has two vertical type cylindrical vessels, fabricated in six segments separately and integrated with bottom & top flanges. The four flanges (Size: OD 980 x ID 852 x 20 mm and OD 980 x ID 802 x 20 mm thickness & OD 970 x ID 802 x 20 mm) were fabricated from AISI 316LN grade plate.

Raw material was optimally utilized through cutting into segments and integrated as a ring flange with double V butt weld joint to reduce the weld distortion. The weld joints were qualified through NDT and machined to achieve specified dimensional and geometrical tolerances. Support plates are provided on each flange to strengthen the IVs and to facilitate the assembling and dismantling requirements in the annular gap of STV.

The manufacturing of IVs was a challenging task due to machining of ring flanges, cover flanges with stringent dimensional & geometrical tolerances besides welding quality requirements. Welding procedure qualification was established for the automated TIG welding process using column and boom type welding machine and effectively utilized to minimize the fabrication time for longitudinal & circumferential seam welding of cylindrical shells.

In this endeavor, a unique automated gas purging system was developed and used, resulting in the reduction of defects and welding costs as well. This paper highlights the manufacturing methodology adopted, challenges encountered and overcome during fabrication and testing of IVs.

This article is shared by S. Murugan, S. Sathees Kumar, M. Krishnamoorthy, V. Praveen Kumar, B.S. Ramesh Babu, Utpal Borah, Mohd Sabih, Alka Kumari, G. Ramesh and M.V Kuppusamy.

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