Abstract: Prototype Fast Breeder Reactor (PFBR) is a 500MWe pool type, sodium cooled, first of its kind nuclear reactor which is presently in advanced stage of construction by BHAVINI at Kalpakkam, India. The boundaries of the sodium systems are designed so as to have an extremely low probability of abnormal leakage, rapidly propagating failure and gross rupture under the static & dynamic loads expected during various operating conditions. Therefore, design for the above shall include considerations of degradation of material properties (e.g. effect of sodium, temperature and irradiation), transients, residual stresses, flaw size etc. The principal material of construction for sodium piping circuits is austenitic SS316LN/SS304LN. All sodium pipelines inside Reactor Containment Building (RCB) of PFBR are provided with hot guard pipe and are inerted with nitrogen. The guard piping and the containment penetrations require sequential welding and NDT which are unique to PFBR. Limited space at site for the erection of sodium piping along with welding at inaccessible areas with confined space makes the work all the more challenging. Manufacturing of thin and big bore piping with tight tolerances along with the high distortion in stainless steels due to high thermal expansion and low thermal conductivity makes fabrication extremely challenging. With strict rules of sloping to be given to the piping to make conducive for full draining of the sodium loops, the fabrication challenges becomes multi fold. The welding standards and acceptance criteria of PFBR sodium piping system is very stringent compared to conventional piping systems. The welding of sodium piping systems are carried out by combination of Shielded Metal Arc Welding (SMAW) and Gas Tungsten Arc Welding (GTAW) process as per stringent PFBR specification requirements. Due to complex constructional features of the sodium piping systems, the argon gas purging, welding and non-destructive examinations are extremely difficult and challenging task. Various special tools and fixtures were designed, developed and used for welding & fabrication to ensure high degree of reliability against failure. This paper highlights on welding aspects, challenges faced by BHAVINI management and innovations during fabrication activities of sodium piping circuits for 500MWe Prototype Fast Breeder Reactor.
Keywords: Quality Management, Welding, Non-destructive examination, Sodium systems.
Title: Quality Management during Welding, Fabrication & Erection of Austenitic Stainless Steel Piping for Sodium Circuits of 500MWe Prototype Fast Breeder Reactor
Author: R.G.Rangasamy, Prabhat Kumar
International Journal of Mechanical and Industrial Technology
ISSN 2348-7593 (Online)
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