4. Sodium quality control in a nuclear reactor

4.1 Pollution sources

There are several types of pollution sources in a nuclear reactor (see box), the most characteristic of which are :

• desorption of oxygen and hydrogen from new metal surfaces introduced into the reactor (new component, new fuel assembly);

• decomposition of metal oxides on the surface by reducing sodium ;

• hydrogen diffusion from steam generators to secondary sodium, due to corrosion of water-side tubes and thermal decomposition of hydrazine added in excess to the water to limit corrosion;

• production of tritium and hydrogen in the core by ternary fission of the fuel ( ²³⁹ ...