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Tripathi, Shri Krishna
- Qualification of Critical Weld Joints for Dynamically Balanced Nuclear Component
Abstract Views :207 |
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Authors
Affiliations
1 Quality Assurance Division, Indira Gandhi Centre for Atomic Research, Kalpakkam – 603102, India, IN
1 Quality Assurance Division, Indira Gandhi Centre for Atomic Research, Kalpakkam – 603102, India, IN
Source
Indian Welding Journal, Vol 55, No 2 (2022), Pagination: 54-62Abstract
Centrifugal extractors (CE) are widely used in reprocessing of spent fuel of fast breeder reactors due to various advantages. The extraction is carried out from a solution of 4-6N nitric acid, organic compounds, and elements containing fission products. Centrifugal forces generated from the rotating bowl (RB) are utilized for this purpose. RB is a thin hollow shell with complex internals. It rotates along a longitudinal axis inside a stationary bowl by maintaining a minimal specified annular gap ranging 3-5 mm during operation. A high-grade dynamic balancing is essential for each fabricated RB to keep generated vibrations within limits of safe operations. The Cylindricity of RB is controlled up to 0.1 mm and a surface finish of N8 is maintained for many reasons including the requirement of dynamic balancing. Despite maintaining all parameters, it is sometimes observed that a considerable quantity of fabricated RB gets rejected due to the non-feasibility of possible corrections during dynamic balancing of fabricated RB. The post-weld examination of internal surfaces is difficult and any type of post-weld repair of fabricated RB remains unproductive. A welding procedure has been adopted during manufacturing of AISI 304L material, 40 mm ID x 1.5 mm (thk) RB with specified dynamicbalancing requirement of grade 2.5 as per ISO1940-1 (2003) at 3500 RPM and corrosion rate of a maximum of 15 mills per year as per practice C of ASTM A 262. The welding procedure qualification has been carried out using gas tungsten arc welding (GTAW). The welding variables such as groove design, heat input, welding position, welding sequence, fixtures, clean fit-up, etc are found as important to monitor apart from other commonly used to meet the acceptance criteria as per ASME sec IX.Keywords
Welding Qualification, Dynamic Balancing, Corrosive Environment, Nuclear Reprocessing
References
- Natarajan R, Raj B (2011); Fast reactor fuel reprocessing technology: successes and challenges, Asian nuclear prospects 2010, Energy Procedia, 7, pp.414–420.
- Bernstein G J, Grosvenor D E, Lenc J F, Levitz N M (1973); Development and performance of a highspeed, long rotor centrifugal contactor for application to reprocessing LMFBR fuels, Argonne National Laboratory.
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- ISO 1940-1, Second Edition, 2003-08-15, Mechanical Vibration; Balance Quality Requirements for Rotors in a Constant (Rigid) State Part 1: Specification and Verification of Balance Tolerances.
- ASTM A 262-15, Standard Practices for Detecting Susceptibility to Intergranular Attack in Austenitic Stainless Steels.
- BPVC-ASME Boiler & Pressure Vessel Code Section IX (2017).
- Corrosion Behaviour of SS304L at Unapproachable Regions of Fillet Weld Joints in Fast Reactor Reprocessing Application
Abstract Views :45 |
PDF Views:2
Authors
Affiliations
1 Indira Gandhi Centre for Atomic Research, Kalpakkam – 603 102, IN
1 Indira Gandhi Centre for Atomic Research, Kalpakkam – 603 102, IN
Source
Indian Welding Journal, Vol 56, No 4 (2023), Pagination: 46-53Abstract
The Purex process is opted for reprocessing of spent fuel from fast breeder reactors. The process employs nitric acid with concentrations up to 11M. Nitric Acid Grade (NAG) SS304L is opted as material of construction for equipments, process tanks and piping of such process plants so as to minimise the corrosion losses due to nitric acid. Practice C test as per ASTM A262-15(2021) (Standard Practices for Detecting Susceptibility to Intergrannular Attack in Austenitic Stainless Steels), with maximum average corrosion rate of 15 mils/year (mpy) for five cycles of 48 hrs, and 18 mpy in any cycle, is one of the criteria for qualification of material among others. A similar acceptance criterion is adopted for qualification of undiluted weld metal deposit of filler material and welding procedure specification (WPS) used therein. However, conventional tests may not always accurately represent the corrosion behaviour of surfaces at all locations. One of such are the surfaces which abut each other, and hence are not approachable for visual examination and thereafter cleaning, such as unwelded open abutted surfaces of fillet weld joint (root), partial penetration (pp) weld joints facing process fluids in abutted portions not in a welded portion of joint. Multiple factors like remains of heat tints, adjacent inter-spaces and type of surface finish may collectively contribute to corrosion rates exceeding acceptable limits. This study delves into the often-neglected corrosion behaviour of these challenging regions. The samples with abutting surfaces are prepared by using EDM cutting and and Gas tungsten arc welding (GTAW) and subjected to corrosion test. The samples made by using base material, filler and WPS that already qualified for corrosion test for groove weld joints and hence fillet weld joints as per ASME BPVC sec IX (2021). Higher corrosion rates are being observed in these weld joints than standard test specimens during study.Keywords
Abutting Surfaces, Heat Tint, Gas Tungsten Arc Welding, Huey Test.References
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- Robert B (Ed) (2005); ASTM, Corrosion Tests and Standards: Application and Interpretation Sec. Ed. p.246.
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- Tripathi SK, Kuppusamy MV and Athmalingam S (2022); Qualification of critical weld joints for dynamically balanced nuclear component, Indian Welding Journal, 55, pp.54-62.
- Natarajan R and Raj B (2011); Fast reactor fuel reprocessing technology: successes and challenges, Asian nuclear prospects 2010, Energy Procedia, 7, pp.414–420.
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