Borates play a key role in the operation of nuclear power plants, and they are essential in the safety and control of pressurised water reactors (PWRs). The 10B isotope, present at around 20% natural abundance, has a very high nuclear cross section and is able to capture thermal neutrons resulting from the fission reaction of the uranium nuclear fuel.
The rate of the nuclear reaction, and the energy generated from it, can be controlled by adjusting the quantity of 10B in the reaction environment. In practice this is achieved by dissolving boric acid in the primary cooling circuit of PWRs. Very high purity boric acid is necessary for this application.
Borates are also used elsewhere in the nuclear power plant. Boron carbide can be used for the control rods, and borates are used as corrosion inhibitors and also as a key safety feature of the emergency core cooling system.