Solubility of Manganese and Iron in Sodium

Abstract

Neutron irradiation of the structural materials in a fast reactor core gives rise to activation products such as 54 Mn, 59 Fe, 51 Cr, 58 Co and 60 Co. These radionuclides may be released into the coolant, get transported to various parts of the primary coolant system and deposited there resulting in high radiation fields. This will render maintenance and repair very costly, necessitate longer waiting periods and lead to higher reactor down time which will affect reactor operating economios. Among the nuclides, 54 Mn is the most abundant and the most troublesome as it gets readily transported to cooler parts of the primary circuit (1). Data on the solubility of manganese in sodium will help in efforts to model the behaviour of 54 Mn in sodium systems and to devise means of minimising its transport. A program of experiments to measure the solubility of manganese in sodium is underway at Reactor Research Centre, Kalpakkam. Our initial experiments (2) had indicated strong dependence of the manganese solubility on oxygen concentration in sodium. The present experi¬ments were carried out both in static capsules and in a small pumped isothermal loop.