Development of Stainless Steels in Nuclear Industry: With Emphasis on Sodium Cooled Fast Spectrum Reactors History, Technology and Foresight

Abstract

Stainless steels (SS) have earned a unique position as a widely accepted class of alloys with track record of steadily improving the performance and increasing applications from 1913 till date. This distinction is attributed to R&D, innovations and applications leading to harnessing the rare combination of properties of stainless steels, since its discovery hundred years back. Though the initial discovery of stainless steel is basically serendipity, and based on previous work, its indispensable position today, in many a wide range of applications is due to intense R&D efforts in understanding its physical, chemical, thermal and thermo-mechanical response for various chemistries and microstructures. A deliberate attempt to extend its application spectrum through various routes of manufacturing in the last century is another crucial aspect of the success story. The first part of the presentation would briefly review this exciting journey of unravelling the mysteries of stainless steels.The second part of the presentation would highlight the evolution of stainless steels in the nuclear industry, especially for the sodium cooled fast reactors. Early 70s have seen the application of stainless steels in first generation water based nuclear power plants and AISI types 304 and 316 SS was recommended for structural and core applications in fast spectrum reactors (FSR). Failure of some of the components even in the manufacturing stage and quest for improving mechanical properties and sensitisation and intergranular corrosion resistances resulted in the development of 304L, 304LN, 316L, 316LN SS during 1980-90 for further applications in FSRs. Towards core applications in intense radiation environments, three generations of stainless steels namely 20% cold worked 316 SS, D9, and D9I have been developed to yield high burnup and to triple the lifetime of the core components of the fast reactors. Towards closing the fuel cycle, again 304L SS was the workhorse material which was upgraded with newer varieties like nitric acid grade alloys for improved corrosion resistance and longer life. Manufacturing of special grades of SS and the developments in fabrication technologies was necessary in order to enhance the performance of components and to avoid failures. Welding, inspection, quality assurance and structural integrity of various components of SS for FSRs and fuel cycle facilities resulted in developments in areas like modelling, devices, methodologies and analysis. An opportunity existed for the development and application of innovative non-destructive testing techniques for robust examination of critical components.Nuclear industry is embarking a state of the art fourth generation reactors. The consequent newer generation of SS are evolving with improved properties to match the expectations of performance in increased temperature, pressure, chemical and other physical constraints. It is of paramount importance to consider the extension of the lifetime of the current reactors from 40-60 to 60-80 years for economic considerations, and in this regard innovations are necessary in the development of newer varieties of stainless steels with respect to modelling and life prediction, manufacturing, fabrication, testing and evaluation. Thus the management approach to knit a network of industry-research-academia is a key approach for way forward. A development of roadmap for robust science based technology development with foresight is a desired management strategy.

Control of exposure to hexavalent chromium concentration in shielded metal arc welding fumes by nano-coating of electrodes

“…The weld was laid on SS 316 LN plates fixed on a variable speed rotating plate inside the chamber. The authors have chosen SS 316 LN instead of SS 316 L since it is potentially being used as the major structural material in (1) T = 0.9 cos fast breeder reactors in the nuclear industry [18]. Though the low carbon content in SS 316 L reduces the tendency of carbide precipitation and localized corrosion in the weld, it has a detrimental effect on the strength of the weld thereby limiting its use.…”

Nuclear forensic signatures and structural analysis of uranyl oxalate, its products of thermal decomposition and Fe impurity dopant

“…This is fundamental knowledge to nuclear forensics, as industrial samples often contain impurities; this includes iron, of which, impurities may typically be found in concentrations up to 80 ppm in some reprocessed oxides [18]. Fe contaminants in industrial samples may arise from sources such as stainless steel, which is used extensively in industrial nuclear components [19].…”

Random Forest Approach in Modeling the Flow Stress of 304 Stainless Steel during Deformation at 700 °C–900 °C

“…Due to its superior properties, 304 stainless steel has been used in a variety of fields, including marine service, power plant, the nuclear sector, oil industries, etc. [ 1 , 2 , 3 , 4 ]. Correspondingly, the deformation characteristics and mechanical properties of 304 stainless and other austenitic stainless steel under various environments have represented one of the major research topics in the field.…”