A case study on elimination of premature failure source from manufacture of fluoroelastomer inflatable seals for Sodium-cooled Fast Reactor towards sustainability

Abstract

An innovative model of engineering failure analysis leading to a prospective model of sustainability and decarbonisation, supported by design-material-failure threads, emerge from two defective test inflatable seals (Seals; ∼2 m dia) subjected to laboratory investigations i.e. visual, dimensional, physico-mechanical, material fingerprinting and analysis of variation. The Seals of 500 MW(e) Prototype Fast Breeder Reactor (PFBR) design were industrially manufactured (year: 2007) by cold feed extrusion and continuous cure (CFECC) of a peroxide cured, Viton GBL 200S:600S blend compound, APA-1, 2007. Primary aim was to implement life maximization (global design thread) potential (≥30 y) of advanced polymer architecture (APA) fluoroelastomer (FKM) in reactor inflatable seals (∼6.3 m/∼4.2 m dia) with repeatability and reproducibility by eliminating premature failure source from improper manufacture.Unfeasibility of or unlikely value addition from validation-modelling-simulation-microstructure study necessitated innovative treatment i.e. extracting maximum from the minimalist investigation by maximizing interpretation-data mining-cross verification and utilizing past (validated) FEA results of standard FKM PFBR inflatable-backup seals (life: 10 y) through design-material threads. The treatment was reinforced by reorientation of perspective. Distribution of laboratory data along Seal circumference was interpreted as phenomenological manifestation of thermomechanical-electrochemical interactions in the APA-1, 2007 macromolecular realm, brought about by thermomechanical loads from the progressing CFECC with time. The data was thus utilised to reconstruct the CFECC (2007) in terms of processing parameter variance with respect to a benchmark CFECC study on identical seal design. Incorrect cure index (of APA-1, 2007; global failure thread) was ascertained as the source of premature failure by tracing the origin of departures e.g. tracking the straying of APA-1, 2007 tensile stress-strain behaviour (structure property correlation) and cracking failure limits (global material thread) from the desired (i.e. ≥30 y) along the abstracted echelons (i.e. reconstructing manufacture, molecular-phenomenological interplay) of the CFECC in terms of unacceptable macromolecular transitions. The novel approach and methodology predict new-seal-failure-situation in reactor (by residual stress) and/or continuing operation-safety uncertainty of inflatable seal and reactor (by undercure) from the incorrect cure index. The identified source and template for permanent rectification are crucial for FBR-Gen IV cover gas elastomeric sealing. The applicability extends to other nuclear and inaccessible-hazardous, critical/very critical elastomeric usage (marine, air, space, oilfield, gas etc.) as well.The research findings provide complete description of (APA-FKM) residual stress and tensile stress-strain behaviour by the first principles and an analogy of mechanical-entropy spring, accompanied by a new commentary on structure-property-performance correlation of APA-FKM. The findings are expected to enrich understanding of rubber failure. The failure analysis of a very critical nuclear component grows vastly in connotation using global threads to suggest a prospective conceptual benchmark template for sustainability-decarbonisation-augmentaion i.e. better realization of life maximization potentials in applications by synthesizing improved specifying-manufacturing-quality monitoring with the global threads.This study could provide basis for new research on defect modeling-simulation-validation and encourage formulation-modeling-validation of new constitutive relations, considering incorrect cure index and its effects. The concepts and routes of maximum from minimum, working by first principal, reconstruction, threads and molecular-phenomenological interplay are expected to find wider scope beyond this research.