Experimental Facility for Thermal Striping Studies in Dynamic Sodium Environment

Abstract

In the Prototype Fast Breeder Reactor [PFBR], sodium coolant streams flowing out through the various fuel and blanket subassemblies mix in the sodium pools. This mixing interface is unstable, oscillating and the component structures nearby are subjected to the effects of oscillating temperature conditions causing stresses to be induced in the components. Thermal striping [TS] occurs due to the random thermal cycling of a structural component by a flow stream resulting from the mixing of nonisothermal jets near that component. The random thermal cyclic load leads to development of surface cracks and assist in crack growth which in turn may lead to failure of the structural component due to crack initiation by the high cycle fatigue mode. TS has been a critical mode of failure which has been studied in many FBR systems worldwide. An experimental facility has been constructed and commissioned at FRTG to study TS by conducting in-sodium experiments simulating the fuel-blanket interface to measure the temperature fluctuations on the surface due to mixing of nonisothermal jets in sodium. This paper brings out the spectrum of activities involved in establishing this test facility, focusing on its features, the challenges overcome, testing philosophy adopted for the effective utilisation of experimental facilities for conducting the TS experiments.