Heat exchange in a mechanically stirred granular bed: application to the SimSan sodium carbonation process

Metallic sodium has been widely used in the fields of research, development and exploitation of fast breeder reactors as a coolant. Despite it reacts violently with substances such as water and other oxidants, it has been selected for its good thermal properties, its low viscosity and its low melting point (97°C). This sodium became activated (formation of radioisotopes: 22Na, 24Na, and 25Na) and/or contaminated by radioactive compounds (3H, 60Co, 55Fe) depending on the nature of the experiments. As a result of experiments, 90 litres of contaminated sodium must be treated in SCK•CEN. More important amounts of contaminated sodium are present in other countries. For example, 5500 tones of sodium have to be treated in France due to the exploitation of Superphenix. Although it reacts more violently than the pure sodium, NaK (alloy of sodium and potassium) has been also used as a coolant with the advantage of being liquid at the ambient temperature.