Estimation of hydrogen mass flux from water side to sodium side in a sodium heated Mod 9Cr1Mo steam generator

Heat, produced in a SFR (Sodium cooled Fast Reactor) is exchanged to a sodium circuit, where it is further transferred from sodium to water in a steam generator (SG). SG, typically made of ferritic steel, is a shell and tube heat exchanger with sodium on shell side and water/steam on tube side. Water/steam, flowing through the SG tube, reacts with the tube material, producing magnetite and hydrogen. Most of the hydrogen, formed in the water side, permeates into sodium through the SG tube wall and becomes the major impurity in sodium. The mass flux of hydrogen, permeating into sodium, is particularly important in the design of cold trap (CT) which is used for purifying sodium. Experiments were performed with a model SG made of Mod 9Cr1Mo having 19 tubes, in Steam Generator Test Facility (SGTF) at Indira Gandhi Centre for Atomic Research (IGCAR), to quantify hydrogen flux. Material, structural layout and operating conditions of SG of Prototype Fast Breeder Reactor (PFBR) were simulated. This paper brings out the data and experiences gained through the experiments.

► In sodium heated steam generators, hydrogen is produced in the water side.
► Hydrogen permeates into the sodium side and becomes a major impurity.
► Hydrogen mass flux from water to sodium side, is a very important design data.
► We experimentally quantified hydrogen flux through a Mod 9Cr1Mo steam generator.
► It is compared with literature data available for 2.25Cr1Mo steam generator.