Regeneration qualification of cold trap using modeling validated by radiography and image processing

Cold trap is a purification unit used in sodium cooled Fast Spectrum Reactors (FSRs) for maintaining the oxygen and hydrogen level in sodium within acceptable limits. It works on the principle of crystallization and precipitation of oxides and hydrides of sodium in a wire mesh, when the temperature of sodium is reduced below the saturation temperature. The sodium hydride gets accumulated in the secondary cold trap as a consequence of the continuous diffusion of hydrogen in sodium and with time the trap is fully loaded and becomes inoperable. The removal of these impurity deposits at intervals by keeping the cold trap in same location of the loop is known as in situ regeneration. After regeneration cold trap is qualified by gamma radiograph technique to ensure adequate removal of impurities before bringing the cold trap back to service in sodium for purification. The numerical results predict the impurity deposition pattern in the wire mesh region of cold trap. The mathematical model has been validated with experimental data obtained from model cold trap. This paper discusses the methodologies developed for qualification of regeneration of cold trap using radiography and image processing techniques for assessing impurity deposition before and after regeneration.