Sodium quality control in a nuclear reactor
The Sodium Coolant

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 (²³⁹Pu and ²³⁵U) and by activation of the boron contained in the control rods in the form B₄C (boron...