LAUSR

Abstract In Advanced Heavy Water Reactor (AHWR), two active, independent, functionally diverse, fast acting shut down systems are used. Shut Down System-1 (SDS-1) consists of mechanical shut off rods and Shut Down System-2 (SDS-2) based on liquid poison injection into the moderator. Gadolinium nitrate solution, which acts as neutronic poison, is injected in heavy water moderator through a set of nozzles located inside calandria vessel. This poison injection into moderator inside calandria is expected to take place in a very short time to shut down the reactor. As SDS-2 is critical for the safety of plant, detailed knowledge of poison distribution in calandria is required. CFD analysis using OpenFOAM has been carried out for high pressure poison injection of Shut Down System-2 of AHWR for various design options. Validation of CFD model is performed by experimental measurements. Experiments are performed for impulsively started poison jet in a 1/3.3 scaled and full-scale experimental facilities with array of tubes. In particular, the growth of poison jet is measured experimentally and CFD simulations are performed. An excellent agreement is found between CFD simulations and experimental data. CFD simulation shows that the poison covers a major portion of active core in 2 s time. In addition to this, effect of moderator flow and heat generation in moderator on poison distribution has also been studied.