Trace analysis in the sodium coolant of fast breeder reactors

Liquid sodium is the preferred coolant in fast breeder reactors. While sodium itself is compatible with the structural materials in the coolant circuits, presence of even trace levels of impurities such as oxygen, carbon and hydrogen can lead to corrosion and mass transfer. In addition, metallic impurities, activation products and fission products have to be monitored in the coolant circuit to keep track of corrosion, mass transfer, activity transport, incursion of impurities and fuel failure. This paper summarises the development of trace analysis techniques as applied to sodium in support of India's fast reactor programme. The techniques for handling sodium are discussed and laboratory techniques for analysing trace level metallic and non-metallic impurities in sodium are described. On-line meters being developed for monitoring oxygen, carbon and hydrogen are mentioned. The main features of the analytical sodium loop that is being set up for meter calibration and intercomparison of results from different techniques are brought out. The methods proposed to be used for the determination of radioactive impurities in the primary sodium in the reactor are indicated. (author)