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<p>This paper presents the development, numerical analysis, testing and qualification of long and slender bellows for sodium cooled fast reactors especially in in-vessel fuel handling mechanism. Bellows of SS316L material are used to prevent the entry of the sodium in the annular space between concentric gripper tubes of the mechanism. Based on the space requirements, the length to diameter ratio of the bellows is more than 3 which is beyond the recommended value in EJMA. Commonly such bellows are manufactured with intermediate squirm rings with circumferential seal welds. Failure of any single weld including L-seam weld can lead to loss of leak tightness of the system. An improved design with 2 plies with each ply independently capable to carry the pressure loading and with a tangent type lip seal weld configuration was developed. An in-house experimental facility was developed for testing of such long and slender bellows addressing their bucking under compression and column instability under internal pressure. Fractographic investigation of the tested bellows at the fracture location showed striations and confirmed that the failure mode was fatigue. The methodology proposed in this work can also be used for developing slender bellows such as in large size sodium valves.</p>

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Study on Fatigue Response of Long and Slender Multi-Ply Bellows and Its Failure Analysis

  • 期刊论文

  • 发表日期：

    2026年7月24日

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  • S. C. S. P. K. Krovvidi,
  • C. R. Das,
  • T.V. Maran,
  • S. Chandramouli

摘要

This paper presents the development, numerical analysis, testing and qualification of long and slender bellows for sodium cooled fast reactors especially in in-vessel fuel handling mechanism. Bellows of SS316L material are used to prevent the entry of the sodium in the annular space between concentric gripper tubes of the mechanism. Based on the space requirements, the length to diameter ratio of the bellows is more than 3 which is beyond the recommended value in EJMA. Commonly such bellows are manufactured with intermediate squirm rings with circumferential seal welds. Failure of any single weld including L-seam weld can lead to loss of leak tightness of the system. An improved design with 2 plies with each ply independently capable to carry the pressure loading and with a tangent type lip seal weld configuration was developed. An in-house experimental facility was developed for testing of such long and slender bellows addressing their bucking under compression and column instability under internal pressure. Fractographic investigation of the tested bellows at the fracture location showed striations and confirmed that the failure mode was fatigue. The methodology proposed in this work can also be used for developing slender bellows such as in large size sodium valves.